Do “Super Bugs” Really Improve effluent Treatment?
By Pulp & Paper Canada
By Pulp & Paper Canada
The addition of specialized blends of bacteria (or “super bugs”) to biological treatment facilities is sometimes used to improve effluent treatment performance and effluent quality. This process is kn…
The addition of specialized blends of bacteria (or “super bugs”) to biological treatment facilities is sometimes used to improve effluent treatment performance and effluent quality. This process is known as bioaugmentation. Although “super bugs” are still seen by some as a type of magic “snake oil” that does not really work, case studies in the pulp and paper industry are gradually revealing that the approach may have some merit.
“Super bugs” are essentially aerobic and facultative anaerobic microorganisms and fungi which are blended with biological nutrients and stimulants. They are typically in the form of a freeze-dried, free-flowing powder, often packaged in water-soluble packages and 10-kg plastic pails. The bugs are added directly to aerated lagoon or activated sludge treatment systems to introduce a “superior strain” of bacteria and develop a microbial diversity that improves biodegradation of organic matter. In some cases this can also reduce odor coming from effluent treatment systems. Bioaugmentation has been used for many years to treat outdoor toilets and septic tanks. Based on discussions with suppliers, it appears that bioaugmentation is used regularly by municipal sewage treatment plants. A number of pulp and paper mills have run trials with some positive feedback.
Recommended procedures would be as follows:
1. Clearly define your objectives.
Are you targeting better TSS (total suspension solids), BOD or COD removal? Or do you want toxicity or AOX removal? The following results are based on trials from three mills:
Lower TSS and BOD in final effluent;
Better control of filamentous organisms and less sludge bulking problems;
Minimize the shock from mill shutdown/start-up events.
2. Choose a supplier that provides good service and is willing to work with your company on a trial.
There are a number of suppliers and the difference between their “bugs” is somewhat of a mystery. I am aware of the following companies: Interbio, GFR Biosystems, B.B. Environmental Inc., Helix Laboratories Inc, Micro-link Inc., and chemical suppliers such as Nalco. Ask for information and quotes from several suppliers, including client references (preferably in the field of pulp and paper). Some companies may even offer a rebate on the product and a free depth survey of your ASB (aerated stabilization basin) lagoons as part of the deal.
3. Review dosages and try less than recommended to save money.
The cost of an ongoing bioaugmentation treatment for 1 year can range from $50 000 to over $150 000, depending on the size of the treatment system and the application rate. Dosage rates vary with effluent flow rates, retention times and system variations (e.g. activated sludge vs aerated lagoons). Based on an effluent flow of 75 000 m3/d, we calculated that 10 kg/d was a recommended maintenance rate (i.e. one bucket everyday). However, we decided to experiment with 10 kg every two days and this appeared to show equally good results in TSS removal.
4. Conduct the trial in the right conditions
Ideally, the conditions of the effluent throughout the treatment plant should be similar before and after the trial, especially with respect to the following parameters:
Effluent temperature and pH;
Inlet TSS, COD, BOD;
Nutrient addition and aeration rates.
I suggest adding the bugs in a relatively stable environment if possible. We added them after an initial aeration stage in our ASB, once effluent temperature and pH was more stable and most of the biological treatment had taken place.
5. Measure and track the right environmental indicators.
Depending on your objective, the proper indicators should be measured, including TSS, BOD and COD removal across the system. Since final effluent ammonia levels and acute toxicity are closely linked, I strongly recommend tracking ammonia removal rates. It should be noted that certain suppliers also market ammonia removal bugs (i.e. nitrifying bacteria) to help complete the nitrogen cycle.
Given today’s effluent issues it would also be interesting to monitor any final effluent improvements in colour, AOX, sublethal toxicity and endocrine disruptors. Since bioaugmentation changes microbial diversity and can reduce filamentous problems, the microbiology of the system should be tracked as well (daily microscopic examinations).
Keep in mind that the effect of the bugs may linger for two months after you stop adding them. After all this, I recommend a simple “before and after” comparison. In our case, we stopped adding the bugs several times in order to track any changes in system performance and effluent quality.
One of the claims of “super bugs” suppliers is that bioaugmentation can reduce sludge build-up in municipal activated sludge systems by improving the conversion (degradation) of organic material to dead bugs that weigh less and occupy less space. Certain suppliers claim anywhere between 10 and 35% reduction in dry solids, depending on the retention time of the system.
If it also holds true for pulp and paper systems, it could save large operational costs due to sludge handling/disposal, such as dredging ASB lagoons.
Long term studies are needed to evaluate solids generation in pulp and paper ASB and AST systems, and carefully track performance and effluent treatment costs. The end result should be overall cost savings due to less solids handling, lower chemical/nutrient costs, and less capital expenditures needed to improve effluent quality.
Bioaugmentation can have some benefits such as:
Reduced filamentous problems and improved settling;
Improved effluent quality;
Preparing or re-seeding biological systems for mill shutdown/start-up events;
Enhanced performance of lagoon systems in winter months.
One mill is currently experimenting with super bugs in a spill basin as an alternative to dredging. The plan is to add the bugs and introduce aeration to breakdown the solids in order to “buy more time” prior to dredging. The same mill also claims that super bugs have reduced its filament problems at its AST following a mill expansion and increase in effluent flow. As a result it has significantly reduced its use of hypochlorite as a control method for filaments. If the bugs can replace harsh chemicals then it is certainly beneficial to the environment!
Phil can be reached at firstname.lastname@example.org.