91bio Technical Blog

Why We Blend Cultures Against Your Data Instead of Selling Catalogue Items

2026-10-24T00:00:00Z

A culture for industrial effluent is not a catalogue item, because the same product name has to work across water that differs in load, temperature, salinity, pH and what has already killed the biology. A blend is assembled to solve a specific failure mode at a specific site: one organism for the carbon load, another for nitrification, a third where the water is cold or the ammonia is high. It is also the honest answer to the question a fixed specification cannot answer honestly, which is what a given water needs.

Why one product cannot cover every site

The argument against a fixed catalogue item is not commercial. It is biological. A nitrifying organism and a heterotrophic organism respond to temperature differently, grow at different rates, and are washed out by different conditions. The culture that is right for a lagoon in a warm climate at low ammonia is the wrong culture for a plant in a cold climate chasing a nitrogen limit, even where the two plants treat water from the same industry.

Add the site variables that are not in the product name at all. Retention time decides whether an introduced population has time to establish. The existing biology in the basin decides whether the new population is compatible or simply outcompeted. The injection point decides whether the culture ever reaches the water it is supposed to treat. And the failure mode decides what the culture has to do, which is a different question from what it is.

A single product sold against a range of conditions has to be dosed conservatively enough to be safe in the worst case, which means it is under-dosed in most cases. That is the mechanism behind most disappointing results: not a bad product, a product asked to do a job it was not selected for.

What a blend actually solves

A blend is not a larger dose of the same thing. Each component exists because a specific part of the problem needs it, and the useful question for a buyer is what each one is there for.

On carbon load, a fast-growing heterotrophic population is what consumes readily degradable organics, and it recovers on its own within days once conditions allow. On nitrogen, the organisms doing the work are slower, tolerate a narrower range, and are the first to be lost when conditions move. Those are different organisms with different requirements, which is the plain argument for combining them rather than hoping one strain does both adequately.

On cold or high-ammonia conditions, a component selected for that temperature range is added, because a population selected for a warm plant will not recover quickly enough in a cold one. Where a plant is being dosed to recover from a specific shock, the blend is assembled around the damage the shock caused, and the timing follows the correction of the cause rather than preceding it.

None of this is exotic. It is what an application engineer does when given a site's data, and the only reason it is unusual as a commercial offer is that most suppliers prefer to sell a fixed line rather than spend the time on the selection.

The variables that change the answer

Six groups of information actually change what gets proposed, and it is worth being specific about them because a buyer sending only one of them will get a general answer.

The water. COD, BOD, TN, TP, ammonia, salinity, temperature and pH. Not all of it is needed to start — an ammonia figure and a description of how the plant behaves are enough to tell whether biology applies at all.

The failure mode. A load spike, a toxic discharge, a pH excursion, a temperature drop and filamentous bulking are five different problems, and organic removal and nitrification failing are two more. This is the single most useful thing a buyer can tell us, because it narrows the selection faster than any other input.

The process. Aerobic, anaerobic, MBBR, SBR or lagoon, the SRT, and the temperature range. This decides whether an introduced population can establish at all.

The existing biology. Current MLSS, what is in the basin now, and what has happened recently. Compatibility with the population already present decides the outcome more often than the choice of culture does.

The dose point. Inlet, aeration basin, dosing skid, spray bar. The same product introduced at the wrong point is a different product.

The variability. Average load, peak factor, how often a batch arrives. A plant that varies needs a programme, not a single dose.

What we do with your data, and what we will tell you

The sequence is short and it is designed to fail early rather than late. You send whatever you have. We read it against the failure mode and the process, and we either propose a strain selection or a blend with a dosing plan and a monitoring method, or we tell you that the constraint is not biological.

That second outcome is the one worth emphasising. If the problem is hydraulic, structural, aeration capacity or a permit limit, no culture addresses it, and a supplier who sells you one anyway has sold you a delay rather than a solution. Where the bottleneck is a design fault or an operating regime, saying so early is worth more to a buyer than a quotation.

Where a blend is proposed, the reasoning is stated rather than implied, so the buyer's own engineer can review the selection instead of taking it on trust. The figures that go into the quotation are the ones we agreed against the site data, not a range printed on a web page, and they are the figures we will be judged against when the result is reviewed.

Why we would rather say not yet

A supplier who publishes a viable count, a strain composition and a fixed dosage on every product page is telling you something, and it is not that the figure is accurate. It is that nobody checked it against a site. The number is almost always the culture's own specification rather than a performance expectation, and a buyer who relies on it will size their dose against a number that was never tied to their water.

We would rather have a page that says the value is confirmed per site and explains what it depends on. It costs us the convenience of a number that can be quoted in a comparison table, and it costs the buyer a little more work before they can order. What it buys both sides is that a figure appearing in a quotation means the same thing on both sides of the table.

If that trade is not the one you want, a supplier who will print a number for you is available and the enquiry will be answered quickly. What it will not be is a number your engineer can rely on at the design stage.

Frequently asked questions

Why do you not publish the viable count or dosage on your product pages?: Because a number printed on a web page is a number nobody has confirmed against your water. It is the culture's own specification, not an expectation for your site, and a buyer who sizes their dose against it is working from a figure that was never tied to their effluent. We state the value in the quotation instead, after reading your data.
What data do you need before you can propose a culture or a blend?: Enough to know the failure mode and the process. A full analysis is ideal but not required — an ammonia figure plus a description of how the plant behaves is often enough for us to say whether a biological route applies at all. What is not useful is a request for a price list, because we cannot quote a culture without knowing the duty it has to do.
Will you tell us if biology is not the answer?: Yes, and we regard it as part of the job. If the constraint is hydraulic, structural, aeration capacity or a permit limit, no culture addresses it. In that case we say so, because a supplier who sells a product anyway has sold a delay rather than a solution, and the delay is more expensive than the quotation.
How long does a custom selection take?: Reading the data and proposing a strain selection or a blend with a dosing plan and a monitoring method does not take long once the operating data has been sent. What takes time is the site data itself, and where a plant has no recent analysis, arranging sampling is usually the critical path. A written technical response is normally within 48 hours of receiving usable operating data.

Controlling Dog Odour Without Compromising the Dog

2026-10-23T00:00:00Z

Odour control around dogs has a constraint that separates it from almost every other application: the treatment is in the same airspace as the animal, all the time, and a product that is not safe to inhale at close range is not usable. The useful measures are therefore structural rather than chemical wherever possible, and the chemical ones have to be selected on the basis of their safety data for the specific exposure, not on how well they work on odour.

Why dog odours differ from other sources

Dog urine is a different composition from cat urine and it smells different for chemical reasons rather than because it is worse. It is higher in volume in relation to the animal, it has a different nitrogen compound profile, and it often arrives in a concentrated spot rather than distributed. Dogs also sweat through their feet pads, which adds a further source at floor level, and their bedding and kennel fabric absorbs what the floor does not. Where cats use a latrine that can be isolated, dogs distribute over an area, which means the odour source cannot be contained by the same means.

The practical consequence is that kennel and multi-dog household problems are usually a surface-area problem as much as a chemistry problem. A dog kennel that is hosed once a day still holds odour in the fabric, and the fabric is what the dog sleeps on and what fills the airspace the dog breathes.

Structural control first

Four measures produce more than any product, and they should be in place before a chemical is specified. Frequency of removal removes the source, and it is the only method that does so completely. Drainage matters more than people expect: urine that lingers in a floor because the floor slopes the wrong way keeps a source active after cleaning, and correcting a slope is permanent while spraying is not. Washable surfaces in preference to absorbent ones, for the same reason. And ventilation at dog level, because a kennel with air movement only at roof level leaves the breathing zone unchanged.

Where a housing area has fabric that cannot be replaced, washable bedding pads and regularly washed fabric are a substantial improvement and cost little. Absorbent material that is never washed is a reservoir, and no deodoriser applied to the air around it will resolve that.

Choosing a product that is safe to use around a dog

The first question is whether the product has been assessed for direct contact and for inhalation at close range, and whether the safety data says so in writing. This is not a formality. A product formulated for environmental use in a refuse area may present a different profile from one assessed for use in an enclosed space where an animal lives, and the difference is in the exposure, not in the active ingredient.

The second is the contact question. A product that is safe to inhale but not to lie on is a poor fit for a kennel where the dog lies on the bedding that has been treated, and it is a reasonable specification requirement that the product be assessed for skin and coat contact. The third is whether the product is neutral to the dog rather than merely un-toxic: an odour that is unpleasant to the animal discourages the behaviour you are trying to encourage, and in a kennel that behaviour may be to avoid the bedding.

What works where

For hard floors and drainage, an enzymatic product applied to a clean surface before it dries is effective, because the enzyme is working on the substrate at the point where it is most concentrated. The timing is the thing: an enzyme applied after the urine has dried onto a floor has lost most of its advantage, because the substrate has become bound to the surface.

For bedding and fabric, the route is different. A product that competes biologically needs the fabric to be damp enough to support a population, which conflicts with the need to keep bedding dry; and a product applied to a dry absorbent surface will simply be absorbed along with the urine. In practice the effective sequence is: remove, treat the hard surface, wash or replace the fabric. Treating fabric alone does not work well, and any supplier implying otherwise is describing a result you are unlikely to reproduce.

For the airspace, air treatment has a limited role. It is worth using in combination with the source controls above, and it is not worth substituting for them.

The welfare question that comes before the product

Some odour problems in a domestic setting are behavioural rather than chemical. A dog that soils indoors is usually responding to a change in routine, a change in the household, insufficient access outside, or a medical condition, and treating the odour chemically without addressing the behaviour means the odour returns as soon as the chemical stops working. The first two questions to ask a client are therefore whether the behaviour is new, and whether anything in the household changed when it started.

In a kennel or shelter the equivalent question is whether the density has changed, whether the housing is undersized, or whether the cleaning interval has been reduced under staffing pressure. All three increase urine concentration and volume per unit of space, and all three will defeat any odour product. None of them is a product question, and identifying them early is the difference between a treatment that works and one that is bought twice.

Frequently asked questions

What is safe to use around dogs for odour control?: The product should be assessed for direct skin and coat contact as well as for inhalation at close range, and the safety data should say so in writing. This matters because a product formulated for environmental use may present a different profile from one assessed for an enclosed space where an animal lives. We supply formulations with that assessment and provide the current safety data sheet on request.
Why does my dog kennel still smell after being hosed down?: Usually because of what the hosing does not reach. Urine that lingers where the floor slopes the wrong way keeps a source active after cleaning, and fabric such as bedding and kennel mats holds odour in the material itself. The sequence that works is: remove, treat the hard surface while it is still wet, and wash or replace the fabric. Treating fabric alone does not work, whatever a product description suggests.
Should I use an enzymatic or a biological product for dog odour?: For hard floors and drainage, an enzymatic product applied to a clean surface before it dries works best, because the enzyme acts where the substrate is most concentrated. A biological product that competes with odour-forming bacteria needs a damp surface to support a population, which conflicts with keeping bedding dry. In practice the two serve different purposes, and a combined approach across floor and fabric is more reliable than either alone.
My dog has started soiling indoors. Is this an odour problem?: Not usually, and it should be treated as a behavioural or medical question first. New soiling indoors is usually a response to a change in routine, a change in the household, insufficient access outside, or a health issue. Chemical odour treatment will mask the symptom and the odour will return when it stops working. The first questions to ask are whether the behaviour is new and whether anything changed when it started.

Bacteriophages: A Working Overview of the Biology and Where They Fit in Practice

2026-10-22T00:00:00Z

Bacteriophages are viruses that infect bacteria. A phage attaches to a specific receptor on the bacterial surface, injects its genome, and uses the host's own machinery to replicate before lysing the cell. Three features follow from that description and explain most of the practical interest and most of the practical difficulty: they kill bacteria rather than inhibiting them, they are specific to a narrow set of strains, and they can replicate in the presence of susceptible bacteria. Whether that is an advantage or a problem depends entirely on what you are trying to do.

The infection cycle

A phage begins by recognising a receptor on the bacterial surface. That step is what determines host range, and it is why the same phage can be effective against one strain of a species and useless against another: the receptor is a specific structure, and strains differ in whether they carry it and in what form. The tail structure that makes the initial attachment is therefore the part of the genome that gets engineered when a broader range is wanted.

Once attached, the genome is injected and the host's ribosomes and enzymes are redirected to replicate it. New phage particles assemble, and the cell is lysed, releasing them. What happens next depends on the phage. In the lytic cycle that is the whole story, and the phage kills its host. In the lysogenic cycle the phage genome integrates into the bacterial chromosome and is copied along with it, so the cell survives and may not lyse at all. Temperate phages switch between the two, and the switch is not fully predictable.

Why specificity is both the strength and the problem

A phage kills rather than inhibits. That matters in medicine, where the aim is to remove a pathogen without damaging the surrounding flora, and where an antibiotic that suppresses growth leaves the organism alive to develop resistance. It also matters in any setting where the target population needs to be removed rather than held in check.

The cost is coverage. A receptor is a specific structure, and the population in a sample or a patient is a mixture of strains, not a single organism. A single phage will often cover only part of the population, which is why phage work is often done with cocktails, and why a library of phages with different receptor specificities is a practical asset. The engineering problem is to broaden range without making the phage recognise bacteria the application depends on, and that trade has not been fully resolved for general use.

What a phage library contains

A phage display library is a very large, very diverse population presented on the surface of phage particles, generated by fusing each variant gene to a coat-protein gene so that the encoded protein is displayed. The diversity typically runs to hundreds of millions to billions of independent variants, and because each variant is physically linked to the gene that encodes it, a phage that binds can be recovered and the gene sequenced from it.

That linkage is what makes the technique powerful and what distinguishes it from selection in animals or by hybridoma methods: the binding molecule and its gene are recovered together, with no cloning step in between. It is the standard route to antibody and binding-protein discovery, and it is the service we supply: presenting a target, screening a library, recovering and characterising the binders, and delivering the sequences in the format agreed for the work.

What phages are used for, and what we supply

Three application areas account for most of the work: anti-bacterial applications, where phages or engineered phages are developed against specific pathogens; resistance reversal, where a phage construct is used to select for bacteria that have regained antibiotic sensitivity; and delivery systems, where phages present antigens or other payloads. Each has a different engineering requirement, and the third is the most distant from a treatment.

What we supply is phage display and the related recombinant antibody work — library screening, binder recovery and characterisation. We are explicit that this is research-stage work and not a clinical product. A sequence recovered from a display campaign is a starting point for a project, not a treatment, and anyone presenting a display result as a therapy has misrepresented what the technique produces.

Frequently asked questions

What is a bacteriophage?: A virus that infects bacteria. It attaches to a specific receptor on the bacterial surface, injects its genome, uses the host's own machinery to replicate, and lyses the cell to release new particles. Some phages instead integrate their genome into the bacterial chromosome and are copied with it, which is called the lysogenic cycle, and temperate phages can switch between the two.
Why do phages only work against some strains of a species?: Because attachment depends on a specific receptor structure on the bacterial surface, and strains differ in whether they carry it and in what form. A phage selected against one isolate often will not attach to another. This is why phages are frequently used as cocktails, and why broadening host range by engineering the tail structure is a central research aim.
How large is a phage display library and what does it give you?: Typically hundreds of millions to billions of independent variants, each displayed on the phage surface and physically linked to the gene that encodes it. That linkage is the point: a phage that binds your target can be recovered and its gene sequenced directly, with no cloning step in between. It is the standard route to antibody and binding-protein discovery.
Do you supply phage therapy or clinical phage products?: No. We supply phage display and related recombinant antibody discovery as research-stage services: library screening, binder recovery and characterisation, with the sequences delivered in the agreed format. We do not supply clinical phage products, and a sequence recovered from a display campaign is a starting point for a project rather than a treatment.

Dosing Bacteria at a Wastewater Plant: How Much, How Often, and How to Know It Worked

2026-10-21T00:00:00Z

The most common question about a bacterial culture is how much to apply, and the honest answer is that a single figure is not useful because the same dose means different things in different volumes of water. What is useful is the ratio between the seeded population and the population already in the basin. Below is how that ratio is worked out, how often the dose is repeated, and which measurements should be used to judge the result rather than a subjective impression after two weeks.

Why a single number is not the answer

A dose expressed as a volume of product is meaningless on its own, because the same litre of culture is a negligible addition to a large basin and a significant one to a small tank. The meaningful quantity is the ratio of the seeded population to the population already present, because what matters biologically is whether the introduced organisms are numerous enough relative to the existing community to establish and to compete.

That is why the first two things we ask for are the volume of the reactor being treated and the mixed liquor solids concentration. The volume tells you the hydraulic scale, and the solids tell you the population density. With those, plus what the product's viable count is at the point of delivery, the seeded-to-existing ratio can be estimated rather than guessed.

Calculating a starting dose

The working method is to express the target as a ratio rather than as a volume. For a culture intended to establish and become the working population in a reactor, the practical starting point is a seeded population of roughly one to five percent of the existing biomass per application, repeated as needed. This is an order-of-magnitude figure for setting a trial, not a specification, and it will be adjusted once responses are seen.

Two corrections matter more than the base figure. Activity is the first: the same volume of product at a lower viable count is a smaller dose, which is why a count guaranteed at the end of the storage period matters and not one taken at manufacture. Retention time is the second: the seeded population has to survive long enough to establish, and in a reactor with a short retention time a large fraction of it leaves before it multiplies. Where retention time is short, either the ratio must be higher or the dose must be repeated more frequently, and this is the most common reason a first dose appears to do nothing.

How often to repeat

Frequency follows from establishment time and from how quickly the population declines. A culture in a healthy reactor with a working biological population usually establishes within a few weeks, and a single well-chosen dose is often enough. A reactor that is being repeatedly disturbed — a plant that is shocked regularly, or one where conditions fluctuate sharply — needs repeated dosing, because the population cannot establish if the conditions it depends on do not persist.

There is a specific case worth naming, because it is so common and so often handled in the wrong order. Where a plant is dosing a culture to recover from a shock, the culture should follow the correction of whatever caused the shock, not precede it. Adding biology to a plant that is still receiving a toxic influent is spending money on a population that cannot survive, and it is a frequent cause of the conclusion that the product does not work.

Judging the result by measurement

Four measurements, and none of them is an impression. Operational stability: the settling and sludge volume behaviour, which is usually the first thing to change because a healthier population aggregates better. Organic removal: the COD or BOD figures that existed before the dose, compared with the same figures afterwards, at the same sampling point and time of day. Nitrification: the ammonia figure, which responds more slowly and is the measure that separates a cosmetic change from a working population. Heterotrophic rate, where the plant runs a respirometry or similar routine, which is a direct measure and often the first to move.

Two cautions on how the results are read. Odour is not a measurement: operators adapt to a persistent smell, and a subjective improvement reported from within a plant is weak evidence in a way an ammonia figure is not. And a single improvement is not attributable without a comparison — ideally a period before and after, and ideally a second comparable reactor that was not dosed. Where no comparison reactor exists, the best available substitute is a sufficiently long baseline at consistent sampling.

What to send us, and what you get back

Five items and we can return a specific starting dose rather than a general recommendation: the reactor volume; the mixed liquor solids concentration; the retention time; the figures you are currently trying to move, with the sample point; and the problem itself in one sentence — a shock, a start-up, a chronic exceedance or a specific compound.

What you get back is a starting dose, the repeat interval we would suggest, and the measurements we would want to see at what times. What we will not do is guarantee a result for a plant we have not seen, and we will say so if the problem turns out to be something no biology addresses — an inhibitory influent, a hydraulic problem, or a design fault. Those cases are worth identifying early, because they are not dosing problems and no amount of culture fixes them.

Frequently asked questions

How much bacteria culture should I add to my wastewater plant?: A single volume figure is not useful on its own, because the same dose means different things in different reactor volumes. What is meaningful is the seeded-to-existing population ratio. As a starting point for a trial, a seeded population of roughly one to five percent of existing biomass per application is the order of magnitude we work to, adjusted for product activity and retention time. Send us the reactor volume, the solids concentration, the retention time and the current figures, and we will return a specific starting dose.
How often should bacteria be dosed?: It follows from establishment time and how fast the population declines. In a healthy reactor with a working biology, a single well-chosen dose usually establishes within a few weeks. Where the plant is repeatedly disturbed or conditions fluctuate sharply, the population cannot establish and the dose must be repeated. Where the dose is for recovery from a shock, it should follow the correction of the cause rather than precede it.
How soon will I see a difference?: The first thing to change is usually sludge settling behaviour and sludge volume, because a healthier population aggregates better. Organic removal figures typically move within a week or two. Ammonia responds more slowly, and it is the measure that distinguishes a cosmetic change from a working population. We agree a measurement plan before the dose so the result is readable rather than a matter of opinion.
Can a culture fix a plant that keeps being shocked?: Not on its own. A culture added to a plant still receiving a toxic influent is spending money on a population that cannot survive. Correct whatever is causing the shock first, then dose. If the cause cannot be corrected, the honest answer is that no biological product will hold the plant, and it is worth knowing that before buying rather than after.

Storing Wastewater Bacteria: What Determines Shelf Life and How to Keep a Culture Usable

2026-10-20T00:00:00Z

A wastewater culture is a living preparation, and its usable life is determined by how it is stored rather than by how old it is on paper. Four variables matter: the carrier it is held in, the moisture content, the temperature, and how long it sits. None of them is complicated, but a product delivered in good condition and then stored badly performs like a product that was old when it arrived, and the difference is indistinguishable at the point of use.

Why viability falls at all

The organisms in a culture are alive between delivery and application, and a bacterial population declines through a combination of natural die-off, moisture loss, temperature stress and, over longer periods, the breakdown of the carrier. The rate of that decline is what a shelf-life figure represents, and it is a property of the formulation rather than a general truth about bacteria.

This is why two products with the same nominal organism count can behave differently, and why a supplier quoting only a count is quoting half the relevant information. A count taken at manufacture says nothing about what arrives at your site, and a count taken before dispatch can be several steps from the count at the end of a long shipping and storage cycle.

The four variables

Temperature is the largest single factor, and the relationship is not linear. Refrigerated storage slows the decline markedly; storage in a hot vehicle, a container in summer sun or a warehouse without climate control accelerates it. Freezing is a separate question and depends on the formulation — some preparations tolerate it, and where a product is supplied as a dry powder, freezing and thawing cycles are a risk to be avoided rather than a storage method.

Moisture is the second. A dried preparation held in a humid environment reabsorbs water, and once the carrier is damp the population begins to decline at a different rate than in the dry state. Sealing the container immediately after opening matters more than most buyers expect.

The carrier determines the acceptable range for both of the above. Some carriers are stable dry and tolerate a wide temperature band; others keep the population viable but need refrigeration. Time is the fourth, and it is the one that is most often underestimated: a product specified for use within a short window after manufacture is not thereby unsuitable, but it is not suitable for long-term storage, and it should not be bought as though it were.

Storing between deliveries

For a plant using a product periodically rather than continuously, four rules cover most cases. Store sealed, in the original container, at a stable temperature away from direct light. Do not open a container and then return the remainder to the store; decant the amount needed into a clean, dry, closed vessel first. Keep the storage area dry and not subject to condensation, which matters more in a warm humid climate than most people expect. And label with the date received, because the useful life runs from manufacture and the two dates are not the same.

For a product requiring refrigeration, the practical failure is a plant that has no dedicated refrigerated storage and therefore keeps the product in a domestic fridge that is opened many times a day, where the temperature is not actually stable. Where that is the situation, it is better to order the quantity that will be used within the short acceptable window than to refrigerate badly and try to stretch it.

What to ask a supplier, and what to do when a product arrives late

Four questions are worth asking any supplier. What the specified storage conditions are, in temperature terms rather than as “cool and dry”. What the activity or count is guaranteed to be at the end of that period rather than at manufacture. Whether the guarantee is on the delivered product or on the batch, because these differ. And what evidence is available for the shelf-life figure, since a figure quoted without a test behind it is a marketing number rather than a specification.

If a product arrives after a shipping delay, the useful step is to assess it rather than to assume it is dead. Where the formulation allows, a simple check against the previous batch is possible. Where the delivery has been hot, the risk is real and the honest answer is to ask the supplier to assess the affected consignment and, if necessary, replace it. A supplier who replaces without argument is a supplier whose count is a specification; one who argues is telling you the count was only ever a number.

Frequently asked questions

How long does a wastewater bacteria product keep its activity?: It depends on the carrier, the moisture content, the storage temperature and the time, and the figure is a property of the formulation rather than a general truth. What we supply includes a stated storage condition in temperature terms and a guaranteed activity figure for the end of that period, not merely at the point of manufacture. Ask for both, and ask what the figure is based on.
Can I store the product at room temperature?: Only if the product is specified for it. Some carriers are stable dry across a wide temperature band; others require refrigeration to hold the population. The relationship with temperature is not linear, so a product kept in a hot vehicle or a sunlit container can decline considerably faster than the same product kept cool. If the storage area has no climate control, order the quantity you will use within the short window rather than storing badly and stretching it.
Does opening the container affect the remaining product?: Yes, which is why the practical rule is to decant the amount you need into a clean, dry, closed vessel and to reseal the original immediately rather than repeatedly opening and closing it. A dry preparation stored in a humid environment reabsorbs moisture, and once the carrier is damp the population begins to decline faster than in the dry state.
What if a delivery arrives late or has been stored hot?: Assess it rather than assume it is dead. Where the formulation allows, a simple comparison against the previous batch is possible. Where the delay involved heat, the risk is real: tell the supplier what happened to the consignment and ask for an assessment, and ask for replacement if the product is out of specification. A count that is guaranteed is a specification; a count that was taken at manufacture is only a number.

Running Wastewater Biology in Cold Weather: Why Recovery Takes Longer and What to Do About It

2026-10-19T00:00:00Z

Cold water slows biological treatment in two separate ways, and a plant can be affected by either one or both. The first is that the organisms grow more slowly, so the recovery of a damaged population takes longer in the cold than it would in summer. The second is that nitrifying organisms are affected more than others, so a plant that handles organic load reasonably in winter can still miss its ammonia limit. The practical consequence is that the dosing regime has to change in the cold, not simply continue unchanged from the summer.

Two different cold effects

The first effect is general. Below about 20 degrees Celsius, the maximum specific growth rate of most wastewater organisms falls, and a population that would double in a matter of hours in summer takes considerably longer. The consequence is a slower return to a healthy state after any disturbance: a plant that recovers from a shock load in three weeks in summer may take six in winter, and the extended period is still producing at reduced capacity throughout.

The second effect is specific to nitrification. Nitrifying organisms grow more slowly than heterotrophs even at optimal temperature, and they tolerate a narrower range of conditions; as a result they are the first to fall behind and the last to return. This produces the familiar pattern of a plant whose organic removal looks acceptable through the winter while its ammonia stays high, and it is why an ammonia exceedance in cold weather should not automatically be read as a dosing failure.

What cold actually does to the process

Two further consequences matter operationally. The rate of the biological reaction drops, so the same amount of load needs a larger volume of active biomass to be treated. And the rate at which the process responds to a change in load drops with it, which is why a plant can be operating acceptably and then breach within a day of a load increase that would have been absorbed in summer.

There is also a physical effect worth separating from the biological one. In cold water the gas transfer rate is lower, so aeration is less efficient at the same air flow. A plant can therefore have less oxygen available to the biology than it appears to, and the dissolved oxygen reading at the basin tells you about the mixed liquor rather than about the transfer capacity. Where the aeration system is marginal in summer, it becomes the limiting factor in winter before the biology does.

What helps and what does not

What helps is straightforward. Increase the active biomass ahead of the cold period rather than during it, because a population takes weeks to build and a cold period is not the time to start. Reduce the load where there is operational scope, since the same treatment capacity handles less in the cold. Keep the aeration system clean and check the transfer rate before the season rather than during a exceedance. And lengthen the retention time if the process configuration allows it, which is the cheapest lever available when a limit is being missed.

What does not help is dosing more of the same product on the assumption that more is always better. The population that is slow to establish is slow because of temperature, and adding a large single dose into cold water does not accelerate the growth rate. A culture added ahead of the season, in conditions that allow it to establish, is worth considerably more than the same total added during the first cold week.

Planning for the season

The useful work is done in the two months before the temperature drops. Confirm that the biomass is healthy while conditions still allow fast growth, and increase the solids concentration then rather than in January. Review the aeration capacity against the expected summer-to-winter oxygen demand, because air capacity is fixed and demand rises when biological rates fall. Establish what your ammonia limit becomes at the reduced rate, so the operating target is realistic rather than aspirational. And decide in advance what the trigger will be for a culture dose, so the decision is made on a measurement rather than on a date.

One honest warning. Any figure quoted for cold operation is specific to a temperature range, and a supplier quoting a rate without asking what your winter temperature actually is is quoting a number from a bench study. Send us the monthly temperature range, the current solids concentration, the retention time and the ammonia figures you are seeing, and we will tell you what we would expect and what we would want to measure.

Frequently asked questions

Why does ammonia rise in winter when organic removal looks fine?: Because nitrifying organisms are affected earlier and recover later than the organisms responsible for organic removal. Nitrifiers grow more slowly even at optimal temperature and tolerate a narrower range of conditions, so in cold water they fall behind first. The plant therefore keeps removing organic load reasonably while its ammonia performance declines, and the two do not move together.
Does dosing more bacteria solve cold-weather performance problems?: Not by itself. The population is slow to establish because of temperature, and a large single dose into cold water does not raise the growth rate. A culture added before the cold period, in conditions that allow it to establish, is worth considerably more than the same total added during the first cold week.
Which operational changes help most in cold weather?: Increase active biomass ahead of the season rather than during it, reduce load where there is scope, clean and check the aeration system before the season, and lengthen retention time if the configuration allows. Retention time is usually the cheapest available lever when an ammonia limit is being missed.
What temperature data do you need to advise us properly?: The monthly temperature range at the site, the current mixed liquor solids concentration, the hydraulic retention time, and the ammonia figures you are currently seeing. A supplier quoting a rate without asking what your winter temperature actually is is quoting a number from a bench study rather than from your plant.

Engineering Treatment for Black Odour Water: Why It Happens and What Actually Removes It

2026-10-17T00:00:00Z

Black water in a river or channel is not caused by a pollutant but by a process: organic load depletes the dissolved oxygen in the water, the water goes anoxic, and the sediments beneath it begin to release hydrogen sulphide. Removing the odour therefore means either restoring oxygen to the water or removing the oxygen demand, and only some of those causes can be addressed from inside the water body. That is the central point for anyone considering treatment, because a substantial share of black water cases are caused by inputs that no in-water product can reach.

The mechanism, in the order it happens

It is worth stating the sequence because most interventions are aimed at the wrong stage of it. Organic matter — sewage, agricultural runoff, decaying plant material, or the sludge from a treatment works — enters the water. Bacteria consume it, and consumption consumes dissolved oxygen. When the demand exceeds what the water can hold, the water becomes anoxic. And once the sediments beneath are deprived of oxygen, the anaerobic population in them takes over, producing hydrogen sulphide which escapes into the overlying water and the air above it.

Two consequences follow directly. The odour appears where the water is worst oxygenated, not necessarily where the pollution entered, which is why the visible source and the smelly reach are often in different places. And the sediment acts as a reservoir that continues to release hydrogen sulphide after the surface input has been stopped, which is why odour often persists after an apparent fix.

What biological treatment can and cannot do

What it can do is raise the oxygen demand handling capacity of the water body, or lower the oxygen demand reaching it. In practice that means accelerating the breakdown of the organic load in the water column, so the demand is consumed before it drives the water anoxic, and working the sediment so that the anaerobic population is displaced by aerobic organisms that do not produce hydrogen sulphide.

What it cannot do is remove a continuing input. A biological product added to a water body receiving untreated or poorly treated discharge upstream will improve conditions while it is dosed and lose them when it is not, because the oxygen demand is still arriving. Nor can it oxygenate a stratified, poorly-mixed water body during a warm spell, when the bottom water loses contact with the surface. In both of those cases the intervention that works is outside the water: stopping the input, or aerating it.

How to tell which case you are in

Three questions separate the treatable cases from the ones that need a source change, and they can largely be answered without a survey. Is the input still arriving? Trace the water upstream and look for a discharge. A storm drain, an untreated outfall, a land drain running after rain, or a slurry store is a continuing input and treatment downstream of it will be temporary. Is the water moving? In a slow, deep or stratified reach, bottom water can be anoxic for reasons that have nothing to do with the surface load, and no in-water product will fix stratification. Is the sediment the reservoir? If odour persists long after the input has been reduced, the sediment is holding hydrogen sulphide that will be released over a period of weeks.

Where the answer to the first question is yes, the priority is upstream. Where the answer is no and the water is moving, in-water biological treatment has a real place. Where the answer is no and the water is stratified, aeration is the lever and biology will help at best marginally.

What to send us so we can give a real answer

A section of the affected reach and the distance over which odour is complained about. Whether any discharge enters upstream, and if so what it is and roughly where. Water depth and how it is mixed, and whether the reach is straight or meandering, since a meander slows the flow. Whether the odour is seasonal, and if so which months; temperature stratification explains most seasonal patterns and changes the answer. And what has already been tried, because repeated unsuccessful treatment usually means the real constraint has not been identified.

With that we can return an assessment of whether the case is treatable from the water body, what the expected mechanism would be, and what we would want to measure over the trial. What we will not do is quote a removal figure for your reach. A percentage is meaningless without the volume, the flow and the load, and anyone offering one without asking for those three is selling a number rather than an assessment.

Scientific basis: what the literature says

Two peer-reviewed studies are useful background for the mechanism above. On biofilm, a 2024 study shows that a TatD-type DNase weakens the extracellular matrix that holds biofilms together (Environmental Research, 10.1016/j.envres.2024.118534); the same matrix is what lets sediment and pipe biofilm keep releasing odour after the surface load is reduced. On eutrophication, work on urban landscape lakes sets out how nitrogen and phosphorus load drives the anoxic, odour-releasing state (Water Environment Research, 10.1002/wer.10906). We reference these as background, not as product performance claims — see our Research summaries for the full context.

Frequently asked questions

What actually causes black water in a river?: A process rather than a pollutant. Organic load depletes the dissolved oxygen, the water becomes anoxic, and the sediments beneath begin to release hydrogen sulphide, which produces the odour. The visible source of the pollution and the smelly reach are often in different places, because the odour appears where the water is worst oxygenated rather than where the pollution entered.
Can a biological product treat black water in a channel?: It can raise the oxygen-demand handling capacity of the water and displace the anaerobic population in the sediment, so conditions improve while the product is dosed. It cannot remove a continuing input: a water body receiving untreated discharge upstream will revert when dosing stops. It also cannot oxygenate a stratified, poorly-mixed reach during a warm spell. Where either applies, the intervention that works is stopping the input or aerating the water.
Why does the odour come back after the pollution is reduced?: Because the sediment acts as a reservoir. Under anoxic conditions it accumulated hydrogen sulphide, and it continues to release it over a period of weeks after the surface input has been reduced. Working the sediment with aerobic organisms displaces the anaerobic population, but that takes time, and odour during the transition period is normal.
How long does a black water treatment trial take?: Long enough for the sediment response to show, which is weeks rather than days. A short trial will show a surface improvement and then revert, because the sediment reservoir has not yet changed. We agree the measurement plan and the duration before a trial starts, and we review the results with you afterwards.

Fermenting Livestock Manure: Turning a Storage Problem into a Product

2026-10-16T00:00:00Z

Livestock manure is normally a storage problem: material arrives wet, odours develop, and the volume and weight of what has to be moved afterwards is set by how wet it stayed. A fermentation agent is added to accelerate the breakdown of the organic fraction so that the material stabilises faster, dries more readily and stops generating odour during the period it is held. It works by changing the rate of the process, not by suppressing the smell after the fact, and that distinction is the whole of the product case.

What is happening in a manure store

A store that receives manure daily develops a structure. The wetter material runs to the bottom and forms a low-oxygen zone; drier material sits on top and re-wets each time the store is emptied onto itself. The centre of the pile is oxygen-poor, warm and rich in readily degradable carbon, which is exactly the combination in which anaerobic organisms produce hydrogen sulphide and the strong faecal note. Nitrogen in the same material is converted to ammonia, and the ammonia rises and leaves with the air above the store.

The consequences reach beyond the store. Volume and weight of material to handle are governed by its moisture content, so a wet store costs more in transport than a dry one of the same wet weight. Runoff from a wet store carries nutrients and organic load to drainage, and a farm with a drainage problem frequently has a store problem first. Odour complaints are usually received against the store rather than against the animals, which is why the store is where attention is worth spending.

What the fermentation agent changes

Three things, with different time scales again. The rate of breakdown rises. The readily degradable fraction is consumed faster, so the material stops being an active source of odorous intermediates sooner, and the point at which the material is considered stabilised arrives earlier. Odour during storage falls, because the population producing the strongest odours is displaced by organisms working on the same material through a less offensive pathway. Moisture loss is faster, because the material is being worked through rather than sitting, and the structure that holds water in a wet pile does not form.

The honest limit is that the agent accelerates a process that was going to happen anyway. Where a store is already warm, aerated and regularly turned, the difference between accelerated and normal is a matter of days. Where a store is cold, saturated and never turned, no agent will produce a good result, because the conditions are limiting the process rather than the biology.

Application: where it is added and when

For a heap that will be turned, the agent is added at building, mixed through the material rather than applied to the surface, and the heap is sized so that it can be turned. Turning is what introduces oxygen, and an agent in a heap that is never turned is a significant cost with a limited return. For a store, the addition point depends on how the store is emptied: if material is removed from the top, dosing at the working face treats the material that is actually leaving; if it is removed from the bottom, the addition point needs to move accordingly.

Two operational points carry more weight than the product. First, the material that produces odour fastest is the freshest, so treating the incoming face rather than the whole store body is usually the effective move. Second, the moisture content at the point of application determines whether the biology can act at all. A material that is saturated has no oxygen to offer, and the agent is a seeding rather than an oxygen supply.

Where a manure treatment does not help

It does not help with a drainage problem, and it does not substitute for roof cover. Rain falling into an open store is the single largest source of avoidable odour and the largest contributor to the volume of material being handled; covering the store addresses both directly and costs less than treating the consequences. It also does not remove the need for a covered, impermeable area from which clean water cannot enter, because an agent working in a store that receives surface water is working against the inflow.

Where a farm has an existing digestor, the question is different. Material going to a digester is already under active anaerobic digestion, and the objective becomes digestion performance rather than storage odour. A different product is called for there, and it is worth saying that a storage product is not the right specification for a digester feed.

What to measure to know whether it worked

Three measurements, and all three are straightforward. Odour intensity at the store boundary, on a scale anyone can apply consistently, recorded at the same time of day and preferably at the point in the emptying cycle that has historically been the worst. Moisture content of the material leaving the store, because that is what sets the transport cost. And the time to stability, meaning how long until the material stops generating odour when it is moved.

The comparison that produces a defensible conclusion is two comparable stores, treated and untreated, over a full cycle including emptying. Odour perception is unreliable on its own because operators adapt to a persistent smell, which is why the subjective score should be taken by someone who has not worked in the barn daily, or why the readings should be supported by an instrument. We supply the agent, the application guidance for your store geometry and the trial design, and we review the results afterwards. We do not quote a percentage reduction for a store we have not seen.

Related research

The microbiology behind manure fermentation is not only our internal know-how. In a peer-reviewed study co-authored with the Ningxia Academy of Agricultural and Forestry Sciences and Ningxia University, a combined Aspergillus oryzae and Bacillus subtilis inoculant was shown to accelerate the maturation of beef cattle manure compost and suppress pathogenic microorganisms during a 40-day windrow process. Read the research summary ›

Frequently asked questions

Does a manure fermentation agent replace covering the store?: No, and the order matters. Covering the store addresses both the odour entering from above and the volume of material you have to handle, and it costs less than treating the consequences. A treatment agent works on the material already in the store; rain falling into an open store continues to add odour and volume regardless of what has been added to it.
How is a manure fermentation agent applied?: Mixed through the material rather than applied to the surface, at building for a heap that will be turned, and at the working face for a store emptied from the top. The point of addition should follow the point of removal, because treating the material that is actually leaving is more effective than treating the whole body of the store.
Does it work in a store that is never turned?: The effect is limited. The agent accelerates a process that requires oxygen, and in a saturated, never-turned store the conditions are limiting the biology rather than the product. The same is true of a cold store where the material never reaches a working temperature. Where those conditions cannot be changed, the honest answer is that the treatment will not deliver what a turned and aerated store would.
Can I use a storage product for material going to a digester?: Not without checking. Material going to a digester is already under active anaerobic digestion, and the objective becomes digestion performance rather than storage odour, which is a different specification. Tell us where the material is going and we will tell you whether our product is appropriate or whether you need a digester-feed product instead.

Fermentation Bedding Bacteria on Livestock Farms: How Bedding Culture Works in a Barn

2026-10-15T00:00:00Z

Fermentation bedding culture is added to bedding at the start of a batch and works by turning the bedding into a stable, actively fermenting system rather than an accumulating pile of manure and urine. The culture speeds up the initial establishment of the bedding microbial community, and because the bedding is kept warm and slightly acidic, ammonia release stays low. It works well where the barn is well managed and it does very little where bedding is removed before the culture has established, which is the single most common reason for a disappointing result.

What the bedding actually is

Conventional bedding is an accumulating mixture. Urine adds nitrogen, faeces add both nitrogen and organic load, and the material is removed only every few days or weeks. Early in that cycle the bedding is warm, wet and anaerobic, which is the worst combination for odour: the microbial population that is producing the strongest odours is the one that thrives in those conditions. Deep litter systems work the other way round. The bedding is deliberately kept thick, warm and aerated, and the population established in it is one that processes the incoming material quickly, so the bedding behaves as a working reactor rather than as a store.

Culture is what starts the reactor. The bedding itself already contains microorganisms, but the population that establishes depends on what arrived with the animals, on the bedding material and on the temperature and moisture history. Adding a culture shortens the time needed to reach a stable community, and in the cold months that shortening is the difference between a bedding that works and one that does not have time.

What the fermentation actually changes

Three things change, and they are worth separating because they have different time scales. The odour profile changes because the organisms that break down organic material anaerobically, and produce the strongest sulphur notes, are outcompeted by organisms that work aerobically and produce far less offensive by-products. Ammonia release falls, because microbial activity in a well-established, slightly acidic aerobic bedding converts nitrogen through a pathway that releases less free ammonia. The bedding becomes easier to handle, because the material is structured and drier at the surface than the equivalent untreated pile.

The ammonia effect is the one most often measured, and it is the one most often attributed to the culture when the ventilation is doing most of the work. A barn with poor ventilation will show an ammonia problem whether or not a culture is present, and a culture will not fix it. Ventilation is the primary control; bedding culture is the second control that makes the ventilated air acceptable.

Establishing the culture: the first three weeks decide the result

Establishment is a short window and it is where most failures happen. At the start of a batch the culture is added to bedding that has already been used, or to fresh bedding with the first animals arriving, and the population needs warmth, moisture and time to establish. During that period the barn is at its most anaerobic and its odour is at its worst, because the old community is being displaced.

Three practical points follow. First, the culture is a seeding, not a treatment: it establishes a population and then that population maintains itself, so a single addition at the start of the batch is the correct dosing, not a weekly top-up. Second, the bedding must stay damp rather than wet. Waterlogged bedding goes anaerobic regardless of what has been added to it, and this is the most common cause of failure we are asked about. Third, removing and replacing bedding partway through a batch removes the established community with it, so a batch is a batch and should be run to its natural end.

What a culture does not do

It is worth stating the limits plainly, because the claims made for bedding products in general are broader than the biology supports. A bedding culture does not disinfect. It does not sterilise, and we do not describe it as doing so, and we do not publish sterilisation or disinfection figures for it. It does not remove the need to keep the barn clean, to manage wet areas where water sits, or to control the spillage of urine from a poorly designed drinker.

It also does not solve a ventilation problem, and specifying a culture for a barn whose air is not being exchanged is a common and expensive mistake. If air movement at animal level is inadequate, no bedding treatment will bring ammonia to a limit that the animals tolerate.

How to run a trial that produces a usable answer

If the product has to be justified rather than tried, the trial should be designed so that it can fail. Two comparable pens, one with culture and one without, same bedding material, same animal numbers, same management, over one full batch cycle. Measure ammonia at animal level at the same time of day, and record it rather than relying on a subjective impression, because odour adaptation makes subjective assessment unreliable in a way ammonia readings are not.

What we can commit to on a trial is supplying the culture, the dosing guidance for your bedding depth and the measurement protocol, and reviewing the results with you afterwards. What we cannot commit to is a reduction figure for your barn, because the result depends on bedding management and ventilation as much as on the culture, and a supplier who guarantees a percentage without seeing the barn is telling you something about their confidence rather than about the biology.

Frequently asked questions

How long does a bedding culture take to work?: Establishment takes roughly the first two to three weeks of a batch, during which the odour may be no better and occasionally worse while the new community displaces the old one. The stable phase follows and persists until the bedding is removed. This is why a trial shorter than one full batch cycle tells you very little.
Do you add bedding culture every week?: No. The culture is a seeding step, not a weekly treatment. It establishes a microbial population in the bedding, and that population then maintains itself through the batch. A single addition at the start of a batch is the intended dosing; repeated addition is unnecessary and is not what the product is designed for.
Can bedding culture replace barn ventilation?: No, and specifying it as a substitute is a common and expensive mistake. Ventilation is the primary control for ammonia in a livestock building; bedding culture is the second control that makes adequately ventilated air acceptable. In a barn with inadequate air movement at animal level, no bedding treatment will bring ammonia down to a level the animals tolerate.
Is a bedding culture a disinfectant?: No. It works by establishing a microbial community that processes the incoming material, which reduces odour and ammonia release. We describe it that way and we do not describe it as sterilising, because that is not what the mechanism does. It also does not replace cleaning, and it does not address water sitting in wet areas or urine spillage from poorly designed drinkers.

Sophorolipid Biosurfactants in Oilfield Applications: Interfacial Tension, Mobility Control and Temperature Tolerance

2026-10-14T00:00:00Z

A surfactant used in enhanced oil recovery has one primary job: lower the interfacial tension between oil and water enough that the remaining oil will move. Glycoside surfactants, and sophorolipids in particular, are interesting here because their structure combines a sugar head group with a lipid tail, which gives them a low interfacial tension and a tolerance for salinity and temperature that many conventional surfactants do not have. That tolerance is what makes them candidates for the reservoir conditions where a cheaper surfactant stops working.

What interfacial tension does and why the number matters

Oil sits in the pore space of rock as discrete ganglia, held in place by the capillary forces at the oil-water-rock contact. The capillary force is proportional to the interfacial tension, and it is what keeps the oil from moving when pressure is applied. Reducing the interfacial tension lowers that force, and at a sufficiently low value the oil ganglia can deform and mobilise, which means the oil flows toward the production well instead of staying where it is.

For that reason the figure that gets quoted and the figure that matters are the same one. Our published operating value for interfacial tension with this type of biosurfactant is in the region of 10 to the power of minus three millinewtons per metre, which is the range conventionally treated as the threshold for mobilising trapped oil. It is a published figure with a stated application, and we will re-check it against your specific oil and brine rather than quote it unchanged for a reservoir we have not seen.

What makes sophorolipids different from conventional surfactants

Most oilfield surfactants in commercial use are petrochemical-derived and work by partitioning at the interface in a way that depends on the salinity and temperature of the brine. As the salinity rises, the solubility of the hydrophobic tail changes, and above a certain point the surfactant is salted out of the aqueous phase and aggregates in the oil phase. The practical effect is that a surfactant that performs well in a bench test on fresh water can lose most of its effect in formation brine.

Glycoside surfactants have a sugar moiety as the hydrophilic head. Sugars are highly polar and tolerate high ionic strength without the same loss of solubility, and a glycosidic bond is stable across a wide pH range. That gives two practical advantages in the field: retention of activity at formation salinity, and a narrower pH sensitivity, which matters because produced water is often more acidic than the injection water people specify with.

Temperature, and what happens to a surfactant that fails

Temperature tolerance follows from the same chemistry. A sulfate or sulfonate head group degrades at elevated temperature, and the product loses activity in the reservoir rather than in the test. Glycosides are considerably more stable in this respect, which is the reason the class is discussed for steam-assisted and higher-temperature reservoirs where conventional chemistry is not viable.

It is worth being precise about failure modes, because they look similar from the surface. A surfactant that has degraded in the reservoir produces no change at all. A surfactant that has been adsorbed onto the rock produces a change that decays over the first few days as the concentration in solution falls. A surfactant that has partitioned into the oil may still be active but is no longer available to lower tension in the water phase. Only the first of these is a temperature problem, and the distinction matters for deciding whether temperature is the constraint or adsorption is.

Choosing between a surfactant and a viscosity reducer

Two different problems get grouped together under enhanced oil recovery, and they are solved by different products. Surfactant work lowers the interfacial tension so that capillary forces holding oil in place are reduced. Viscosity reduction addresses the fluid itself: heavy oil is difficult to push because it does not flow readily, and a polymer or a biosurfactant that reduces its apparent viscosity makes the fluid mobile.

They are combined in some fields, and a biological product can act on either. Sophorolipids are more usually discussed for the surfactant role; the heavy-oil products in our range are formulated for the viscosity role. The way to tell which you need is to establish whether the oil is immobile because nothing is pulling it out or because the fluid being injected is too thick to move it. That is a simple rheological comparison and it settles the specification much faster than a general enquiry about enhanced recovery.

What to send us so we can respond usefully

Four things, and with them we can return a specific recommendation rather than a general description. The oil properties: viscosity at reservoir temperature, and the wax or asphaltene content if the oil is crude rather than a refined stream. The brine: salinity, and the pH if it is known. The reservoir: temperature, and whether the injection is secondary or part of a waterflood. And the target: what the current recovery is and what you are trying to change.

Two questions worth asking a supplier before a trial. Whether they have tested against your oil and your brine rather than a standard reference fluid, and whether the reported interfacial tension was measured at reservoir temperature and salinity. Both are reasonable requests and a supplier who cannot answer them has not done the work. We are happy to answer both for the products we supply, and we will say plainly when a case needs field trial data we do not yet have.

Frequently asked questions

What interfacial tension can a biosurfactant achieve?: Our published operating value for this class of glycolide surfactant is around 10 to the power of minus three millinewtons per metre, which is the range conventionally treated as the threshold for mobilising trapped oil. The figure depends on the oil, the salinity and the temperature, so we re-check it against your specific fluid pair rather than quoting it unchanged.
Are sophorolipids better than petrochemical surfactants for oilfields?: Neither is better in the abstract; they suit different conditions. Petrochemical surfactants are cheaper and often effective at low salinity and moderate temperature. Glycoside surfactants tolerate higher salinity, a wider pH range and higher temperature, which is what makes them candidates where conventional chemistry stops working. The right choice depends on your brine composition and reservoir temperature.
Can a biosurfactant replace a polymer in a waterflood?: Generally not as a like-for-like substitution, because they act on different properties. A polymer improves mobility ratio by changing fluid rheology; a surfactant lowers interfacial tension so that capillary forces holding oil in place are reduced. Some biological formulations address the viscosity role, and combining roles is possible, but the specification should follow the problem: if the oil is immobile because nothing pulls it out, that is an interfacial tension problem; if the injected fluid is too thick, that is a rheology problem.
How much biosurfactant is needed for an enhanced oil recovery trial?: It depends on the reservoir, the oil and the injection scheme, and a figure given without those three is not a useful answer. What we can commit to is this: send the oil viscosity at reservoir temperature, the brine salinity and pH, the reservoir temperature and the current recovery, and we will return a specific recommendation with a starting concentration. For a first field trial we would rather agree the measurement plan in advance than quote a concentration nobody has checked.

Engineered Phages: What a 2025 Review Says About Host Range, Resistance Reversal and Targeted Delivery

2026-10-08T00:00:00Z

Engineered phages are being developed in three roles: as anti-bacterial agents that lyse bacteria antibiotic therapy can no longer reach, as vectors that restore antibiotic sensitivity to resistant strains, and as delivery systems for immune or anti-tumour payloads. The three roles are separated by different engineering requirements, and the field has moved furthest on the first. This overview is drawn from a 2025 peer-reviewed review co-authored by researchers at Shandong University of Technology and Shandong Jiuyi Biotechnology (Microbial Pathogenesis, 198:107052; PMID 39442821), which surveys those directions and what remains open.

Why engineered phages rather than wild-type isolates

A wild-type phage that works against one strain rarely works against the next, because host range is determined by the specific receptors on the bacterial surface. A cocktail of wild types improves coverage but does not address the underlying problem, which is that a new strain carrying a different receptor is simply outside the range. Engineering changes the situation by making the recognition step programmable.

The work concentrates on the tail fibre or tail pin protein, which is what makes initial attachment. Three routes have been used: directed evolution against a broader panel, rational design of the receptor-binding domain, and display libraries in which variants with a broadened range are selected directly. Each trades breadth against specificity, and that trade is the central difficulty of the field — a phage that binds too broadly will lyse a bacterium the host depends on.

What the 2025 review maps out: four engineering routes

The review (Cao X., Yu T., Sun Z., Chen M., Xie W., Pang Q., Deng H. Engineered Phages in Anti-Infection and Anti-Tumor Fields: A Review. Microbial Pathogenesis 2025, 198:107052; PMID 39442821) restates why engineering is needed at all: natural phages are highly specific and leave the normal flora untouched, which is exactly why they are attractive, but their narrow host range, the ease with which bacteria tolerate them, and the difficulty of controlling delivery and immunogenicity have kept them at the edge of mainstream use. The argument is that transgene or chemical modification lets each of those limits be addressed directly.

Four routes are surveyed. Host-spectrum modification: replacing or reprogramming the receptor-binding protein, usually on the tail fibre, reshapes or broadens the range so one construct covers more serotypes. Resistance reversal: an engineered phage carries sensitivity back into a resistant strain, after which the antibiotic does the killing. Antigen presentation: displaying a tumour-associated or pathogen antigen on the capsid turns the phage into a vaccine or immunotherapy scaffold. Targeted delivery: the phage is repurposed as a carrier that brings an anti-cancer or anti-infective payload to the infection site or malignant tissue. The review's conclusion is that these modifications take phages from a single killing tool to a programmable biological platform.

Resistance reversal and antibiotic re-sensitisation

The second role is different in kind. Here the phage does not need to kill the bacterium on its own. A phage carrying a small resistance-disrupting payload can select for bacteria that become sensitive to the antibiotic again, at which point the antibiotic does the killing. Because resistance to the phage construct carries a fitness cost while restored antibiotic sensitivity is a large benefit in a treated host, the selection pressure runs in the direction you want.

This is an area where the biology is more advanced than the deployment. The concept is well supported in laboratory study, and the practical obstacles are manufacturing, dosing schedule and the regulatory pathway for a product that is not itself an antibiotic. It also depends on phage biology in ways that matter operationally: a temperate phage integrating into the host genome can be lost when the bacterium divides, so strains carrying the resistance gene in their own genome are preferred for this application.

Antigen presentation and anti-tumour applications

The third role is the most different. Here the phage is not directed at a bacterium but at a mammalian cell, and its value is that it can display a tumour-associated antigen at high copy number without the adjuvant problems of a subunit vaccine. Multiple antigens can be displayed on one particle, which allows a single construct to present a combination, and the same particle can be engineered for a particular adjuvant effect.

The bottleneck is not engineering but delivery and immunogenicity. A multivalent particle is strongly immunogenic, and the useful response to a tumour antigen is not the one that a vaccine is designed to produce. The engineering questions that remain are about controlling where the particle goes and how long it persists, since both determine whether the presentation translates into a response.

What phage display is actually for

Phage display is a different technique and is often confused with the above, so it is worth separating. In display, a gene is fused to a gene encoding a coat protein, and the protein it encodes is presented on the phage surface. A library of billions of variants can then be screened for binding to a target, with the binding phage recovered and amplified. Nothing is lysed and no bacteria are killed; the phage is a display surface that carries a library.

Because the selected variant is linked to the gene that encodes it, this is a route to finding an antibody or a binding protein without having to design one. It is the standard method behind the human single-domain antibody libraries, which are supplied as a screening service: a target is presented, binders are recovered, and the resulting sequences are characterised and expressed in a chosen format.

For buyers specifying this work, the questions that determine whether a campaign succeeds are practical ones. What is the target and how it is presented, because a monovalent soluble antigen selects differently from a cell or tissue sample. What the selection stringency is across rounds. What the final output format is, because a sequence delivered as a gene is not yet a product. And what the acceptance criteria are for a hit, which should be agreed before the campaign starts rather than interpreted afterwards.

Where the field is genuinely open

Three gaps recur. The first is regulatory: a phage product is classified differently in different jurisdictions, and the classification determines the clinical pathway, which in turn determines what manufacturing evidence is required. The second is manufacturing. Phage production is biological, variable and, at anything beyond laboratory scale, expensive per dose, and the economics of a biological anti-infective depend on producing it cheaply enough for the indication to be worth treating.

The third is delivery and residency. A phage that is cleared quickly must be dosed repeatedly, and in the livestock applications this has so far been the limiting factor rather than the biology. A live replicating phage persists longer, but persistence in the host is exactly what regulators scrutinise, and the balance between the two is unresolved for most applications.

We work on phage display and related platform services rather than on clinical phage therapy, and we are explicit about the boundary. The services we supply are library screening and recombinant antibody discovery, which are research-stage activities. Nothing we supply is a clinical product, and any claim that a display-derived sequence is a treatment would be a claim the work does not support.

Where 91bio's phage work sits: from the lab to the farm

91bio's role in this field is practical rather than clinical. The review's corresponding author is affiliated with both Shandong University of Technology and Shandong Jiuyi Biotechnology, and that collaboration is the link between the two. On the 91bio side the relevant assets are phage strain resources, fermentation process know-how and formulation — the part of the chain that turns a construct designed in a lab into something that can be made, stored and applied at scale.

The near-term industrial use is livestock and aquaculture, where "reduce and replace antibiotics" policies have made phage biocontrol one of the most watched alternatives to in-feed antibiotics. A phage that targets a specific pathogen and spares the rest of the gut or pond microbiota is a good fit, because specificity is the property antibiotics lack. 91bio's work here is product development for those environments — see our phage biocontrol for livestock — not clinical phage therapy.

The same collaboration has produced related, publicly retrievable outputs along a "synthetic biology and new medicine" line: a study on planarian TatD DNase against biofilms in Environmental Research, and a review of CDK inhibitors in ChemistrySelect. These are the research record the engineering work builds on, not product claims.

We are explicit about the boundary. 91bio supplies phage-display and recombinant-antibody discovery as research-stage platform services, and develops phage biocontrol products for livestock and aquaculture. We do not supply clinical phage-therapy products, and any description of a display-derived sequence as a treatment would be a claim the work does not support.

Frequently asked questions

What is the difference between phage therapy and phage display?: They use the same biological system for different purposes. In phage therapy, a live phage infects and lyses a target bacterium to treat an infection. In phage display, a gene is fused to a coat-protein gene and the encoded protein is presented on the surface, so a large library can be screened for binding to a target. Display does not kill anything; the phage is a display surface.
Why do engineered phages need a broader host range?: Because host range is set by the specific receptors on the bacterial surface, and those receptors differ between strains. A phage selected against one clinical isolate will often not attach to another. Broadening range by engineering the tail fibre or tail pin is what allows coverage across a panel, and the difficulty is doing so without making the phage bind so broadly that it damages a bacterium the host needs.
Can phages replace antibiotics?: Not in the sense of a direct substitute, and anyone presenting it that way is overselling. The realistic expectation is complementary use: phages for bacteria that antibiotics no longer reach, phages as a means of restoring antibiotic sensitivity in resistant strains, and antibiotics still doing the killing in the second case. Development also faces real obstacles in manufacturing cost, delivery and regulatory classification.
What does a phage display service actually deliver?: Recovered binder sequences from a screened library, together with the characterisation data from the campaign: which clones were selected, at what stringency, and what they bound. The output format matters and should be agreed in advance, because a delivered gene sequence is not yet a product. We supply library screening and recombinant antibody discovery as research-stage services, not clinical products.
Is this based on a published paper?: Yes. The directions summarised here are drawn from a 2025 peer-reviewed review, 'Engineered Phages in Anti-Infection and Anti-Tumor Fields: A Review' (Microbial Pathogenesis, 198:107052; PMID 39442821), co-authored by researchers at Shandong University of Technology and Shandong Jiuyi Biotechnology. Related collaboration outputs include a biofilm study in Environmental Research and a CDK-inhibitor review in ChemistrySelect.

Odour Control at Food Waste and Landfill Leachate Sites: How the Chemistry Decides the Product

2026-10-12T00:00:00Z

Odour at a food waste transfer station, a food waste treatment plant or a landfill leachate site is not one problem. Ammonia, hydrogen sulphide and sulphur compounds behave differently, respond to different products, and are generated at different points in the process. Sites that treat odour as a single issue end up dosing a general deodoriser and chasing the peak. Sites that separate the compounds can usually reduce total dosage, because each product is doing only the job it is good at.

Why food waste and leachate are harder than most odour sources

Two features separate these sites from a wastewater plant or a pet facility. The first is concentration: food waste is a high-strength stream with a high nitrogen content, and leachate from a landfill is frequently an order of magnitude more concentrated than municipal sewage. The second is the surface area presented to the air. A liquid stream can be contained; a tipping hall full of mixed refuse cannot, and odour escapes from the whole volume as it is disturbed.

On top of these, the composition changes through the day. A facility receiving commercial waste in the morning and household waste in the evening sees a different nitrogen and sulphur load in each shift. Any dosing strategy that is set once in the morning and not adjusted is going to be wrong by the afternoon, and the complaint will arrive at the worst possible time.

The three compounds and where they come from

Ammonia comes from the nitrogen in the waste. It is light, it rises, and it is the compound that carries furthest into the surrounding area and into neighbouring properties. At a tipping hall it is released at the point of unloading, which is why complaints often track the collection schedule rather than any treatment step.

Hydrogen sulphide is produced when sulphur-containing material breaks down without oxygen. A compacted, wet, anaerobic mass inside a bin or a compacted layer in a landfill cell is the ideal condition, and the note it produces is the one most people describe as sewage-like. It is heavier than air and concentrates low, in pits, in the receiving area and in the drainage system.

Sulphur compounds beyond hydrogen sulphide — the mercaptans, which include methanethiol — are produced in the same anaerobic environment but from a different pathway. They are the reason a site can be handling a hydrogen sulphide problem correctly and still have an objectionable note, and they are generally the hardest of the three to treat by biological means.

Botanical extracts: where they belong

A botanical extract deodoriser works by neutralising. The active fraction complexes with the odour-forming molecule and converts it into a non-odorous compound, and because the reaction is chemical rather than biological, it is immediate. The practical consequence is that a botanical product is the right tool when you have a short, high-concentration odour event and no time to wait: a tipping hall during a delivery, a covered area being opened after a period of closure, a temporary odour from a tanker or an unwashed bay.

They are also useful where the site is being treated as a problem by people who cannot be persuaded to accept a sustained biological control programme as sufficient. A visible, fast, neutralising action is easier to run past a neighbours' committee than a slow biological improvement, and in that context it has a real place.

What botanical extracts do not do is keep working. The reaction consumes the active fraction, and once the extracted material in the immediate area has been neutralised, the effect fades. That is not a drawback, but it does mean they are an event product rather than a base treatment, and using them as the base treatment is the most common misuse we see.

Biological and enzymatic routes: where they belong

Biological and enzymatic products work on the source rather than on the air. Enzymes break down the specific substrate that releases the odour — typically protein residues for the ammonia pathway and sulphur-bearing compounds for the faecal note — and do so at the source, so the odour is no longer generated rather than being masked after it has formed. Biological formulations go further: they establish a population that competes with the organisms producing the strongest odours and keeps the material on a less odorous pathway.

These routes need time. A biological product establishes a working population over days, and an enzyme product needs to be present when the substrate arrives. The payoff is that the effect persists as long as the material keeps arriving at a controlled rate, which is the normal operating condition of a plant rather than an event.

The combination is where most well-run sites end up. A base biological or enzymatic treatment across the process, with a botanical extract available for the peaks — the tipping bay during unloading, the discharge of a strongly loaded liquor, the emptying of a reception pit. The total daily dose is often no higher than a single-product approach, because each product is only being asked to do the job it is actually suited to.

Dosing practice that determines the result

Most disappointing results in this sector are dosing problems rather than product problems, and they share a pattern. The product is applied once, in a fixed line, at a fixed concentration, and not adjusted. The site generates a variable load, the dose does not follow it, and the peak is untreated.

Practical measures that make a real difference: apply at the point where odour is generated rather than at the boundary where it is complained about; adjust the dose to the delivery schedule rather than to a fixed daily volume; use a fine mist and let the droplets reach the material, because a coarse spray that lands on the floor treats the floor; and keep nozzles clear, since a blocked nozzle is the most common single cause of an under-dosed line.

Two things to settle before specifying. Whether the site needs immediate action at opening, in which case a neutralising product has a place in the first hour, or steady suppression across the day, in which case it does not. And what the complaints actually are — if a neighbouring complaint is a hydrogen sulphide note at a specific time, tracking the complaints against the site timeline will usually identify the source step before any product is chosen, and that answer is worth more than any product selection.

Frequently asked questions

What is the difference between botanical extract and biological deodoriser?: A botanical extract works by neutralising: it complexes with the odour-forming molecule and converts it into a non-odorous compound. The action is immediate but does not persist, so it suits short, high-concentration events. A biological or enzymatic product works on the source, breaking down the substrate that produces the odour or competing with the organisms that produce it. It needs a few days to establish but then persists as long as the load does.
Which deodoriser works best for a waste transfer station?: A combination. A base biological or enzymatic treatment across the process, with a neutralising botanical extract available for peaks such as the tipping bay during unloading. Because each product handles only the compound it suits, the total daily dose is often no higher than a single-product approach.
How should we dose a food waste odour control system?: Adjust the dose to the delivery schedule rather than to a fixed daily volume, apply at the point where odour is generated rather than at the site boundary, and use a fine mist so droplets reach the material. Fixed dosing set once a day will under-treat peaks, which is where complaints originate. Check nozzles regularly, since a blocked nozzle is the most common cause of an under-dosed line.
Is a biological deodoriser a substitute for covering the material?: No. Containment is the first control and chemical treatment is the second. At a transfer station the emission area dominates, and no product substitutes for keeping the material enclosed and disturbed as little as possible. A deodoriser reduces the odour generated at an inevitably open point, and it works far better once the obvious containment measures are in place.

Where Pet Odour Comes From: Ammonia, Hydrogen Sulphide and Skatole

2026-10-09T00:00:00Z

Pet odour in an indoor space is carried by three compounds that behave very differently. Ammonia is produced from urine nitrogen and rises readily in a warm room. Hydrogen sulphide is a heavier, more localised compound associated with faecal degradation. Skatole is the compound that gives faecal material its distinctive note and is the one most products fail to address. Treating the three separately is more effective than treating “odour” as a single problem.

Ammonia: the compound that rises

Ammonia is what urine contributes, and it is the compound most often described as the sharp “animal” note in a room. It forms when urine nitrogen is broken down, and it is favoured by warmth, still air and a high pH. Three practical consequences follow. Ammonia is light enough to mix through the air of a room, so a source in one corner affects the whole space. It rises, so a low source such as a litter tray or a bedding box affects the breathing zone of anyone sitting down. And it is strongly absorbed by textiles — carpets, curtains, upholstery and bedding — where it accumulates and is re-released for months after the original source is removed.

That last point is the one that changes how a control programme has to be run. Ammonia removal from the air alone produces a result that fades within days, because the source and the reservoir are both still present. Effective control means treating the waste where it is produced, and the textile reservoir needs separate attention once the source is under control.

Hydrogen sulphide: the heavy one

Hydrogen sulphide is produced by anaerobic breakdown of sulphur-containing material, which in a pet context means faecal matter sitting in conditions without oxygen. It is heavier than air, so it does not distribute through the room the way ammonia does; it accumulates in the container and in the immediate airspace above it. It is also the compound most associated with the perception of a sewage or rotten-egg note, and it is detectable at concentrations far below the levels at which it becomes hazardous.

Because it is heavy and localised, a room-level deodoriser is the wrong tool for it. Control has to happen at the source, in the container, with enough frequency to prevent anaerobic conditions from establishing. Air treatment in the room can mask the note but does nothing about the material producing it.

Skatole: the one most products miss

Skatole is the compound that carries the distinctive fecal odour, and it is the usual reason a room continues to smell of animals after the waste has been removed and the surfaces cleaned. It forms in the hindgut from tryptophan breakdown and is present in faecal material from the moment it is produced. Being a low-volatility, persistent compound, it stays in textiles and porous surfaces long after the visible material is gone, and it has a low odour threshold.

This is the practical reason why a room can keep smelling after a thorough clean. Standard cleaning removes the material that is still producing skatole, but skatole already bound into fibres and fabrics is not removed by it, and is slowly re-released. Any control programme that has not addressed that reservoir will be working against a source that is not the one you can see.

Matching the treatment to the compound

Once the three are separated, the control routes are straightforward. For ammonia, the priority is frequent removal of urine-contaminated material, together with absorbent coverage under litter or bedding. Ammonia is a nitrogen problem, and it responds to removal rate more than to any product. Enzyme-based products that break down the protein residues releasing ammonia are useful here, because they address the source rather than the air.

For hydrogen sulphide, the control point is the container: keep the material aerated and non-anaerobic, and do not let the cleaning interval stretch. Absorbents that keep the surface drier are directly useful because anaerobic onset is a function of moisture and stagnation.

For skatole, the control point is the textile reservoir. Enzyme formulations selected for the relevant substrate class are the standard answer, together with washing or professional cleaning of the affected textiles. If a room has a persistent fecal note that survives cleaning, the source is in the fabric, and any product applied to the air is buying time at best.

We describe all of our products in this area as reducing odour and improving the biological handling of the waste. We do not describe them as sterilants, and we do not publish sterilisation or disinfection efficacy figures, because the mechanism of a biological or enzyme deodoriser does not support that claim. A buyer who needs a validated kill rate is asking for a different product category, and it is worth saying so plainly at the specification stage rather than after delivery.

Why the smell often returns after a clean

Almost always because of the textile reservoir, and occasionally because the cleaning interval is being stretched without anyone deciding to change it. If a room is cleaned and the note returns within a few days, the likely sequence is that the material producing skatole was removed from its container but not from the surrounding fabric, and the fabric has been re-emitting the whole time. A deodoriser applied to the air will appear to work for a day or two and then fail, and the natural conclusion — that the product is weak — is the wrong one.

The useful check is to clean the textile reservoir, not the room. Wash the bedding, clean the upholstery and curtains, and then judge the deodoriser on whether the note stays away. If it does, the product was adequate and the programme was not. If it does not, the problem is a source that is still producing odour, and it is worth finding where that is before specifying more product.

Frequently asked questions

What causes the smell in a room with a cat?: Three compounds do most of the work. Ammonia comes from urine nitrogen and rises into the air of the room, where it is absorbed by textiles. Hydrogen sulphide comes from faecal degradation, is heavier than air and stays concentrated near its source. Skatole is the faecal note, and because it is a persistent low-volatility compound it remains in fabrics and is re-released long after the material producing it is gone.
Why does the odour come back a few days after cleaning?: Usually because of what is called the textile reservoir. Cleaning removes the material that is still producing skatole, but skatole already bound into carpets, curtains, upholstery and bedding is not removed by surface cleaning and is slowly re-released. Cleaning the affected textiles is what removes the source, after which deodorising products can be judged properly.
Is ammonia the main cause of pet odour in a room?: It is the compound that travels furthest, because it is light enough to mix through the air and is absorbed into textiles. But it is rarely the only one, and treating only the ammonia commonly leaves a faecal note behind. A programme that works on the three compounds separately is more effective than one that treats odour as a single problem.
Does a biological deodoriser kill the bacteria causing pet odour?: No, and we do not claim that it does. Biological and enzyme deodorisers reduce odour and improve the biological handling of the waste, by competing with the organisms that produce the strongest odours and by breaking down the odour-forming compounds themselves. They are not sterilants. If you need a validated kill rate, that is a different product category and should be specified as such.

How Cat Litter Deodoriser Granules Work: Enzyme and Bacteria Deodoriser Partners

2026-10-08T00:00:00Z

Cat litter deodoriser granules do two things. Enzyme components break down the specific molecules that create the smell in soiled litter, while bacterial strains compete with the bacteria that produce those molecules in the first place. Enzyme action is the part that works within hours, so the granules do much of their job before the litter is scooped. Understanding which component does what tells you whether the product suits a single household, a multi-cat home or a commercial cattery.

Where the odour in used litter actually comes from

Used litter smells for two reasons that respond to different treatments. The first is the accumulation of nitrogenous waste — urine breaks down to ammonia and ammonium compounds, and ammonia is the component most people describe as the “strong” smell. The second is faecal bacteria, which break down proteins and produce sulphur compounds including hydrogen sulphide and skatole. Skatole is the compound responsible for the fecal note that ammonia removal alone does not fix.

This distinction matters because a product that neutralises ammonia can still leave a litter box smelling of feces, and the reverse is also true. A product selected for a litter with a strong fecal note needs the enzyme route; one selected for a litter that is mostly stale urine can often be handled by a simpler absorbent and deodorising blend.

Moisture is the third factor, and it is the one most often overlooked. Urine is fully biodegradable, and bacteria start to work on it immediately. In a deep, wet litter box the microbial load rises faster than the air can dry it, and the odour peaks. Granules that keep the surface drier and that keep litter turnover active will therefore outperform a product that only treats the smell in the air above the box.

What the enzyme component does

Enzymes work by breaking a specific chemical bond. The commercial deodoriser enzymes used in litter products are most commonly protease and amylase, sometimes with lipase added. Protease targets the protein residues in urine that release ammonia, and it does so within a few hours of contact. That fast action is what makes an enzyme granule useful: the odour is being reduced at the source rather than masked.

Because the action is catalytic, the enzyme itself is not consumed and does not need to be present in large amounts. What does get consumed is the substrate. When the granule has broken down the available protein, its enzyme activity effectively runs out, which is the reason these products are dosed regularly rather than once and forgotten.

Enzymes are specific, and that is their main limitation. An enzyme selected only for proteins will not touch skatole, which is produced from a different pathway. Products marketed for cat litter frequently add a sulphur-odour component for this reason, and that component is often a separate adsorbent rather than an enzyme. Reading what the granule actually contains, rather than only the front-label claim, tells you which of the two problems it will address.

What the bacteria component adds

Bacteria do not remove odour the way enzymes do. Their contribution is preventative and works on a longer timescale. Introduced into litter, a suitable bacterial population occupies the surface and outcompetes the organisms that generate the strongest odours, and it keeps the litter biologically active so that nitrogen is converted through a less odorous pathway.

The practical difference is timing. An enzyme granule can produce a measurable change the same day. A bacterial component needs several days of regular contact to establish a population. The combination therefore works best in a litter that is changed frequently enough to keep the material moist and undisturbed, which is the normal case for a household cat.

A note on what bacterial deodoriser products are and are not. They are a means of suppressing and competing, not of sterilising. We describe products of this type as reducing odour and improving the biological handling of the waste, and we do not describe them as disinfecting agents, because that is not what the mechanism supports. Buyers comparing listings that promise “99% sterilisation” from the same kind of product are looking at a claim the biology does not carry.

Choosing a granule product for your situation

Three situations dominate, and they point to different choices. In a single-cat household with a large covered box, an enzyme-led granule used at every change is usually sufficient, and the deciding factor is whether you accept a visible granule in the litter.

In a multi-cat home, or a cattery, the odour load per unit of litter is much higher and the box is cleared less frequently. Here the combination matters more than either part, and a granule with a bacterial component is worth the extra cost because it reduces the peak rather than only the last hour before scooping. For a cattery, the honest answer is that odour control is also a function of how often litter is removed; no granule substitutes for cleaning on a fixed interval.

For a pregnant or respiratory-sensitive household, the selection criterion changes. You want a product that has been assessed for direct contact with skin and fur, and one whose safety data can be supplied in writing. Ask for the current MSDS before you buy in quantity, and ask specifically for the form that is cleared for contact rather than the form sold for environmental use.

Dosing and what to expect

Dosing scales with litter volume, not with the number of cats alone. Adding a thin layer across the surface at each change is the usual practice; distributing it through the top of the litter rather than only into a corner is what keeps the odour profile even. If the box is a large deep pan, a small amount spread through the upper third does more than the same amount placed at one end.

On timing: with an enzyme-led product the first change in odour is usually noticeable within a day of application, and over a week of regular use the difference between a treated and an untreated box is the most useful test you can run. If the treated box still smells strongly by day three, the problem is usually loading rate — the box is being cleaned too late — rather than the product.

Two things reduce the effect and are worth ruling out. Litter that is kept deliberately dry and undisturbed gives bacteria very little to work with, so a very dry box with no turnover benefits far more from enzyme action than from the bacterial component. And a heavily scented litter masks odour at the surface while the odour source remains intact, so an apparently “working” combination of a scented litter and a deodoriser should be assessed on cleaning interval rather than on the scent you notice in the room.

Frequently asked questions

How quickly does a cat litter deodoriser granule work?: The enzyme component acts on the odour-forming molecules within hours, so a measurable reduction is often visible the same day. The bacterial component needs several days of repeated contact to establish a population. On a household litter changed regularly, most people report a clear difference within a week of consistent use.
Can a deodoriser granule replace cleaning the litter box?: No. Odour control and removal are different jobs. A granule reduces the intensity of odour from waste in the box, but the waste still has to be removed on a fixed interval, and the product should be dosed at each change. Where cleaning is infrequent, no deodoriser will keep odour under control.
Is a bacteria-based deodoriser safe around cats and people?: It depends on the product. We supply formulations assessed for direct contact with skin and fur, and we provide the current safety data sheet on request. For a pregnant or respiratory-sensitive household, ask specifically for the contact-cleared form and read the safety data before use rather than assuming that all granule products are equivalent.
Which is better for a multi-cat household, enzyme or bacteria granules?: The combination. A multi-cat home or cattery produces a much higher odour load per unit of litter, and the bacterial component reduces the peak while the enzyme component handles the immediate breakdown. A single-cat household with a large box is usually well served by an enzyme-led product alone.

Bioaugmentation After a Treatment Plant Shock

2026-10-08T00:00:00Z

A plant that has lost its biology after a toxic discharge, a pH excursion or an organic slug is usually discharging out of compliance, and the practical question is how quickly normal treatment can be restored. Bioaugmentation is dosed once the cause is contained, alongside corrective action on the influent side, and its job is to shorten the recovery period rather than to replace finding the cause.

What a shock actually does to the sludge

The word shock covers several different events, and they damage the biology in different ways. A toxic or inhibitory discharge — a solvent, a heavy metal, a cleaning chemical, a pesticide — damages or kills part of the population directly. A pH excursion does something similar, and the extent of the damage depends on how far the pH moved and for how long. An organic slug does not poison anything; it overwhelms the oxygen supply, so parts of the plant that should be aerobic become anaerobic and the population that survives is the wrong one.

In all three cases the visible signs arrive together. The mixed liquor becomes thin, the sludge settles poorly, the effluent turns turbid and removal figures fall away. Microscopy usually shows a population that has lost its structure, with free-swimming organisms dominating where a healthy floc used to be.

The point that matters for recovery is that the surviving population is not evenly damaged. Fast-growing heterotrophs recover comparatively quickly once conditions return. Nitrifying organisms grow slowly and tolerate a narrow range, so they commonly lag well behind — and are often the reason a plant appears to have recovered and then misses its ammonia limit for weeks afterwards.

The first hours decide the outcome

What happens in the first few hours after a shock has more influence on the recovery time than anything dosed later. The immediate priorities are to stop the source, protect what biology remains, and avoid making the situation worse with the response itself.

If the event is still arriving, diverting or buffering the influent is the highest-value action available. Where the cause was a pH excursion, correcting the pH gently is more useful than correcting it fast, because a rapid swing damages the surviving population a second time.

There is a strong temptation to stop wasting sludge immediately, on the reasoning that the plant cannot afford to lose any more biology. It is worth being careful here. If the sludge has already lost its settling properties, holding it in the system can leave the plant with a large volume of poor-quality sludge that is difficult to manage later. The right call depends on how much viable biology remains and how the sludge is settling, and it is a judgement better made from operating data than from reflex.

What bioaugmentation adds, and what it does not

Bioaugmentation adds a viable population to a system that has lost one, which shortens the period during which the plant is out of compliance. It does not remove the toxic compound, correct the pH, or prevent the next event. It is therefore used alongside corrective action on the influent side, not instead of it. If the cause is still present in the incoming wastewater, the added organisms will be damaged in the same way as the existing population and the dose is wasted.

The schedule is typically front-loaded: a larger initial dose to re-establish a working population, followed by a maintenance dose while the plant stabilises, tapering as removal performance returns towards its normal range. Because the correct dose depends on the volume of the biological system, the severity of the damage and the load arriving, it should be set against the plant's own operating data. The same event in a small works and in a large municipal plant calls for very different quantities, so we confirm the dose per plant rather than issuing a single figure.

Realistic timelines

Recovery is faster for organic removal than for nitrogen removal, and faster in warm water than in cold. In a plant that has lost its biomass, the first sign of progress is usually a thickening mixed liquor and improving settleability, followed by falling effluent organic figures. Nitrogen recovery generally lags behind. In cold weather both stages are extended, and a plant that would recover in a fortnight in summer may need considerably longer in winter.

Two factors most often derail an expected recovery. The first is a repeated event: where the same discharge arrives again during the recovery period, progress resets and the added population is lost along with the original one. The second is an uncorrected operating condition — a nutrient deficiency, insufficient dissolved oxygen, or a sludge age too short for the organisms being re-established. Both are worth checking before more product is dosed, because dosing again into unchanged conditions mostly buys a repeat of the previous result.

Preventing the next one

The most useful outcome of a shock event is a plan for the next one. That normally means identifying which incoming streams could cause it, agreeing a monitoring parameter that responds early enough to act on, and deciding in advance who diverts the flow and at what threshold. Where a plant receives industrial effluent from tenants it does not control, an equalisation tank or an agreed discharge standard with the upstream source is often more effective than any treatment response.

Frequently asked questions

How quickly should bioaugmentation be dosed after a shock?: As soon as the immediate cause has been contained and conditions in the tank are stable enough for organisms to survive. Dosing into an actively toxic or extreme-pH environment wastes the product, so the sequence is to stop the source, stabilise conditions, and then dose. In most cases that means within the first day or two rather than immediately.
Can a plant recover after a shock without adding anything?: Often yes, given enough time, provided the influent returns to normal and the operating conditions are sound. The reason to bioaugment is time: the plant is discharging out of compliance while it recovers, and the added population shortens that period. Where the plant has ample capacity and compliance is not at risk, waiting may be entirely reasonable.
What is the difference between bioaugmentation and a routine bacteria culture?: The application rather than the category. A culture used for routine process support maintains an already functioning population. Bioaugmentation is dosed after the population has been damaged, with a front-loaded schedule intended to rebuild it quickly. The same product family may serve both roles, but the dose and the timing differ.
Should we reseed with sludge from another plant?: Seeding with sludge from a comparable plant can help where a clean source is available and sludge quality is good, and it is a common approach when a plant has lost almost all of its biology. It also carries the risk of importing the other plant's problems along with its biology, so the source matters. A formulated culture is more predictable in composition, which is why many operators use one rather than relying on a transfer.

Why Black Water Smells and How Biological Treatment Fixes It

2026-10-08T00:00:00Z

Black water smells because sulphate-reducing bacteria in the sediment produce hydrogen sulphide under anaerobic conditions. Aeration and chemical dosing act on the water column and are consumed by ongoing sulphide production; biological treatment works at the sediment interface where the gas is generated, which is why its effect holds for longer once it is established.

Where the smell actually comes from

A black-odour water body — a slow-moving channel, a pond, a section of river downstream of a discharge — smells because of what is happening in the sediment, not in the water you can see. When organic matter settles faster than it can be oxidised, the sediment turns anaerobic. In that environment sulphate-reducing bacteria use sulphate as their oxygen source and produce hydrogen sulphide as a by-product. The surface can look unremarkable while the sediment below is actively generating the gas the neighbourhood is complaining about.

The black colour is a related symptom rather than a separate problem. Iron and other metals in the sediment form dark sulphide compounds, and the water turns black as those compounds are resuspended. Appearance and odour therefore tend to arrive together, which is one reason treatments applied only to the water column produce a visible improvement that does not last.

Why aeration and chemical dosing often do not hold

Aeration is a reasonable instinct: if the problem is anaerobic conditions, add oxygen. The difficulty is that oxygen added at the surface has to reach the sediment to change anything, and in a slow-moving or deep water body most of it does not. The sediment consumes the oxygen in the first few centimetres and the anaerobic zone beneath survives. Aeration can also resuspend sediment, temporarily making the colour worse.

Chemical dosing fails in a different way. Oxidising chemicals and metal salts do suppress sulphide, and in the short term that can be exactly what is needed for a single event or a pressing public complaint. But the effect is consumed by ongoing sulphide production, so it has to be repeated, and each application adds to the chemical load of the water body. Fragrance-based products sit further from the source again: they mask the odour at the point of detection while the sediment continues to generate it.

What biological treatment does differently

Biological control works at the sediment interface, where sulphide is produced, rather than in the water column. The aim is to re-establish aerobic and facultative organisms on the sediment surface, so that organic matter is broken down in the presence of oxygen instead of being reduced to sulphide. When that surface layer is functioning, the sulphate-reducing population beneath it is starved of the substrate it needs and sulphide production falls at source.

Because the mechanism is biological rather than chemical, the effect builds over days to weeks instead of arriving immediately, and it is correspondingly slower to reverse once established. That difference in profile is what should drive the choice between approaches: chemical dosing suits a single event with a fixed deadline, while biological treatment suits a water body that smells every summer or every dry season.

Matching the approach to the site

In practice most projects use both. An initial oxidation or a targeted chemical dose brings the complaint down quickly, and a biological programme then establishes the conditions that keep it down.

Two site conditions are worth checking early. The first is the source of the organic load: if a discharge is still feeding the sediment, any treatment is fighting a rising input. The second is exchange with the wider water body. A channel with strong flow dilutes and carries away the dosed material faster than a pond does, which changes the dosing frequency rather than the principle.

What to measure to know it is working

Smell is the outcome everyone notices, but it is a poor control variable: it is subjective and depends on wind and temperature. More useful is dissolved oxygen near the sediment, together with sulphide concentration at a fixed depth, both tracked at the same points over several weeks. If sulphide falls while dissolved oxygen near the sediment rises, the biological mechanism is working even when the smell on a particular morning is inconclusive.

Frequently asked questions

How long does black odour water treatment take to show an effect?: The first reduction in odour is usually noticed within days, but that early change is not a reliable guide. Establishing a working aerobic layer at the sediment surface takes longer, and the meaningful signal is a falling sulphide concentration measured at fixed points over several weeks. A water body with a heavy accumulated sediment load, or one still receiving organic discharge, takes longer than a clean channel.
Can black odour water be treated without dredging?: In many cases yes, and biological treatment is often used precisely to avoid or postpone dredging. It works on the surface of the sediment rather than its full depth, so a channel with a very thick, highly organic layer may still need dredging eventually. Where dredging is planned, treating before and after the work is common: before to reduce odour during handling, after to re-establish conditions on the new surface.
Is hydrogen sulphide from black water dangerous?: Hydrogen sulphide is toxic at high concentrations and is an asphyxiant, so confined spaces adjacent to black-odour water — culverts, chambers and manholes — must be treated as hazardous and entered only under a proper permit-to-work procedure with gas monitoring. Odour complaints usually arise at concentrations far below that risk, but the nuisance threshold and the safety threshold should not be confused.
Will the treatment harm fish or other aquatic life?: A biological programme is intended to restore aerobic conditions rather than to sterilise the water body, and we position our products as improving biodegradation, not as disinfectants. Any dosing programme for an open water body should still be reviewed against local environmental requirements and the sensitivity of the receiving water, and the supplier should be able to describe what the product contains and how it behaves.

How to Choose a Wastewater Bacteria Culture for Your Treatment Plant

2026-10-08T00:00:00Z

A wastewater bacteria culture should be chosen against four things: the parameter the plant is actually failing on, whether the existing biology and operating conditions will let new organisms establish, what the strain composition and viable count genuinely describe, and whether the supplier will support the dosing programme after the sale. A generic culture bought on price alone rarely solves the problem, because process failures are almost never generic.

Start from the failure mode, not the product name

Most enquiries we receive from plants start in the wrong place. The operator has already decided that a bacteria culture is the answer and asks for a price. The more useful starting point is the parameter that is actually failing, because a plant missing its COD limit and a plant missing its ammonia limit can look identical in a photograph and be entirely different problems biologically.

Organic removal is carried by a fast-growing heterotrophic population that recovers on its own within days once conditions allow. Nitrification is carried by slow-growing organisms with a narrow tolerance that are easily washed out and can take weeks to rebuild. A culture specified for one will not necessarily help the other, and dosing a nitrification culture into an organic-loading problem simply wastes money.

The second question is how the failure arrived. An effluent that has been drifting for months points to a population problem. An effluent that failed suddenly last Tuesday points to an event: a toxic discharge, a hydraulic washout, a temperature excursion or a slug of high-strength waste. Those two histories call for different products and different dosing schedules, and a supplier who does not ask which one applies is not really specifying anything.

Compatibility with the biology you already have

New organisms have to survive in the environment they are dosed into, and that environment is defined by the existing sludge, not by the product brochure. A plant running a very short sludge age is constantly losing biomass, which is one of the most common reasons a biological culture appears not to work: the organisms are dosed, they establish, and then they are wasted out faster than they can grow.

Before a culture is dosed it is worth confirming that sludge age, dissolved oxygen, pH, temperature and nutrient balance sit in a range where the new population can actually hold. In a number of cases the cheapest biological improvement is to correct a nutrient deficiency or to stop over-wasting, after which the culture performs as expected. Adding product to an unfavourable environment mostly buys a repeat of the previous result.

Salinity and inhibitory compounds matter just as much. A culture that performs well in a municipal plant may struggle in an industrial stream carrying high salt, solvents or heavy metals. If the effluent is industrial, ask what the product has actually been used in, not only what it contains.

What a viable count is really telling you

Product data sheets commonly quote a viable count in CFU per gram or per millilitre, and buyers reasonably treat the highest number as the best product. The figure is worth reading carefully. It describes how many organisms were alive in the container at the time of testing. It does not describe how many will still be alive after a month in a warehouse in a hot climate or a week in a shipping container, and it does not describe how many will establish in your plant.

Formulation — how the organisms are protected during storage and how quickly they reactivate after dosing — matters at least as much as the headline number. Two products with the same declared count can behave very differently after a long transit.

Strain composition is the other half of the picture. A count of several billion CFU per gram is not informative by itself; what matters is whether the strains present address the parameter you are failing on. For a nitrification problem, the useful question is whether the product contains ammonia-oxidising organisms and in what proportion. Ask for the composition, and ask whether it is declared on the certificate of analysis or only described in general marketing terms.

Dosing is a programme, not a purchase

A culture is dosed as a programme with three stages: a start-up phase, a maintenance phase and an exit condition. The start-up dose depends on the volume of the biological system and the severity of the failure; the maintenance dose depends on the load the plant sees and how quickly the population is lost; and the point at which dosing can stop depends on whether the underlying cause has been addressed.

A supplier who cannot describe those three stages cannot support the product after the invoice is paid. This is also where local reference matters. Ask what the product has been used on in comparable conditions — similar temperature, similar influent, similar plant size — and ask whether the supplier will review your operating data during the dosing period. For a biological product, technical support is not a service that sits outside the product; it is part of what you are buying.

Documentation to expect before you order

For an imported microbiological product, the paperwork decides whether the shipment clears at all. At minimum, expect an MSDS (SDS) for each product, a certificate of analysis per batch, and a clear statement of country of origin and manufacturing site. Microbiological goods are treated as biological material by many customs authorities, so quarantine approval or an equivalent import authorisation is frequently required and should be identified before the order is placed rather than after the container arrives.

Where efficacy claims are made, ask what they rest on. A percentage reduction in odour, or a percentage improvement in a treatment parameter, means very little without the conditions under which it was measured. Claims that a product sterilises or disinfects a water body deserve particular caution, because that is not what biological treatment does.

A short checklist

Which parameter is failing, by how much, and since when?
Was it a gradual drift or a single event?
What are the sludge age, dissolved oxygen, pH, temperature and nutrient balance today?
Is the effluent municipal or industrial, and what is its salinity?
What is the declared strain composition, and how does it map to the failing parameter?
What are the start-up dose, the maintenance dose and the exit condition?
Will the supplier review your operating data during dosing?
Which documents ship with the order, and what does your customs authority require?

Frequently asked questions

How long does a wastewater bacteria culture take to work?: It depends on which population is being restored. Organic-removal organisms grow and establish comparatively quickly; nitrifying organisms are much slower, so ammonia problems generally take longer to correct than COD problems. The realistic timeline for a given plant is set by its temperature, sludge age and load, which is why a dosing programme should be agreed against your operating data rather than against a fixed number of days.
Can a wastewater bacteria culture be used in a septic tank or a small package plant?: Yes. Small and decentralised systems are common applications, but dose and frequency have to be scaled to the tank volume and the actual inflow, which vary widely between installations. A programme written for a municipal plant should not simply be divided down; ask for guidance based on the volume and daily flow of the unit you actually operate.
Is a higher CFU count always better?: Not on its own. The count describes how many organisms were viable when the batch was tested, and says nothing about survival through storage and transport or about how quickly the product reactivates after dosing. Strain composition and formulation are at least as important, and the meaningful comparison is against the parameter your plant is failing on.
Do we need to change the process before dosing?: Often some adjustment helps, but it is plant-specific. In some cases the biomass needs a period of controlled conditions so new organisms can establish; in others the priority is correcting a nutrient deficiency or reducing sludge wasting. Ask the supplier to review your current operating parameters before the first dose rather than after the last one.