Does bioaugmentation actually work?

Why the question is worth asking properly

Bioaugmentation carries a credibility burden it has earned. Enough products have been oversold over the last thirty years that a meaningful share of experienced plant operators regard the whole category as snake oil. The US EPA published a literature review on the use of commercial bioremediation agents in 2004 that is worth reading in full, precisely because it reflects the scepticism a vendor will encounter.

We sell these products, so treat this page accordingly. What follows is our attempt to set out the strongest case against the product alongside the case for it, because the alternative — writing around the scepticism — is what produced the credibility problem in the first place.

What the evidence supports

The mechanism is enzymatic hydrolysis of organic solids. Published work shows that mixtures of protease, cellulase and lipase reduce total suspended solids by 30 to 50 percent and improve settling, with protease plus cellulase outperforming either alone and lipase augmenting the effect further. One study reported 33 percent volatile suspended solids reduction.

The genus Bacillus is the single most important bacterial source of exactly those enzymes, particularly proteases. Bacillus also sporulates, which means it survives drying essentially intact. For this specific job, the organisms that do the work are precisely the organisms that dry best — so a dry format costs nothing biologically.

What the evidence does not support

The central engineering problem of the category is delivery, and it is much less well studied than the marketing suggests. A lagoon may be six to fifteen feet deep with the sludge blanket at the bottom. Bacteria applied at the surface have to get down there, survive the trip, and remain in place long enough to work.

The peer-reviewed bioaugmentation literature consistently identifies three dominant failure modes for freely suspended introduced cells: washout with effluent, predation by protozoa, and competitive exclusion by the native microbial community. Standard limnology adds a fourth consideration, which is that unmixed water bodies stratify and density gradients limit exchange between surface and bottom layers.

There is circumstantial evidence that the industry agrees delivery is the problem. At least a dozen independent manufacturers have separately engineered dense sinking or carrier-based formats specifically to place organisms into the sludge layer. Competitors converging on the same solution across two decades is reasonable evidence that the industry regards surface dosing as inadequate for bottom sludge — but convergence is not a controlled trial.

When it does not work

There are three conditions under which we would expect a programme to disappoint, and we would rather say so here than discover it with you in the field.

• The accumulation is largely inert. Bioaugmentation digests the volatile organic fraction only. Sand, grit, silt, mineral precipitates and plastics are not biodegradable and will remain regardless of dose, product or format. A lagoon that has been taking road grit or industrial mineral load for twenty years may have very little treatable material in it.
• The lagoon is poorly mixed. No vendor and no independent source claims bioaugmentation works well in a poorly mixed lagoon. Mixing and aeration are treated universally as complementary to bioaugmentation, not as alternatives to it — including by the companies selling sinking-delivery products.
• The water is cold. Spore germination is optimal between roughly 28 and 38 degrees Celsius and slows substantially below that. Biological activity resumes as water temperature passes roughly fifty degrees Fahrenheit, which is why the treatment season is a warm-season window and why cold-adapted strains are commercially valuable.

One more thing a dry product cannot do

Nitrifying bacteria — Nitrosomonas and Nitrobacter — do not survive any drying process. A dry product cannot contain viable nitrifiers, regardless of what its label implies. This matters because ammonia limits are among the most common permit pressures on municipal lagoons. If nitrogen is your problem, a dry-only product line structurally cannot address it and you need a liquid.

How to evaluate a claim, including ours

• Ask whether a published figure came from a controlled study or a vendor case study. Both appear on this page and they are labelled differently for good reason.
• Ask for a guaranteed cell count at the end of shelf life, not at manufacture. Almost nobody in this category publishes it, and it is the number that matters to the operator applying product eighteen months after it was fermented.
• Treat cell count per gram as a weak proxy for performance. What reaches the sludge is concentration multiplied by dose, and neither figure says anything about which species are present, what enzymes they produce, or whether they survive the descent.
• Ask what the vendor measured before they started. If the answer is nothing, there is no way for either of you to know whether it worked.

The manufacturer's field results

Here is that policy applied. These are the manufacturer's published field results, shared with us under the supply relationship and reproduced with permission. We did not run them, we did not measure them, and we have not verified them. Each one carries a tag saying so, and the tag is set as large as the caption on purpose.

The library holds sixteen studies and four are published here. Most of the rest cover lift stations, grease interceptors and collection systems — duties deferred beyond the lagoon launch, which we do not yet size and hold no dose tables for. Two report nitrogen and ammonia results, which a dry product line cannot deliver for the reason given above. Several lead on odour and sulphide figures, which describe acting on organisms rather than on material and sit outside what we are willing to claim. Two more report reductions above 80 per cent, which we have left out because they sit outside the range this page tells you to expect.

Municipal

24 weeks

Barbourville, Kentucky

43.3%

of accumulated solids digested

Supplier-published

Just over five feet of accumulated solids in the primary aerated lagoon, assessed at 2,365 dry tons. The plant wanted a route that did not involve dredging.

• 1,025 dry tons removed
• Average depth 5.08 ft to 2.65 ft

Municipal

Five months, May to October

Inkom, Idaho

48%

reduction in solids volume overall

Supplier-published

Accumulated solids across two lagoon cells, against a specification calling for a 50 per cent reduction. The treatment window was bounded by water temperature, which has to stay above roughly 55°F for the organisms to work at all.

• Cell 1: 75.2 per cent
• Cell 2: 37.5 per cent

Municipal

3 months

Municipal WWTP, United States

672,659lb

of organic solids digested

Supplier-published

Decades of loading had taken the lagoon to a measured 20.5 per cent solids, with a dredging quotation in hand and no budget line to meet it.

• Dredging deferred, not ruled out
• Manufacturer reports a 4.5x cost saving against the quotation

Industrial

12 months

Meat processing facility

50%

reduction in accumulated solids

Supplier-published

Accumulated solids had cut hydraulic retention time to 13 days, capping what the facility could put through the plant and putting effluent quality within sight of a limit.

• Retention time 13 days to 25 days
• Treatment capacity recovered without dredging

Barbourville and Inkom are photographs of those two plants. The remaining pair name no facility — the manufacturer publishes them as a municipal works and a meat processing plant — so those two images are licensed stock showing the kind of lagoon in question rather than the lagoon in question. We would rather draw that line than let one caption cover both.

What remains lands between 43 and 50 per cent, which is the range set out at the top of this page. Inkom is the entry worth reading twice: the same treatment, in the same lagoon, returned 75 per cent in one cell and 37 per cent in the other. That spread is the honest shape of this technology, and it is why a dose is sized against the lagoon in front of us rather than against a brochure figure.