By Jason Calhoun, Managing Director — Municipal Business and Technology, World Water Works, Inc.

Bioaugmentation is an effective way to enhance wastewater treatment efficiency in both public and industrial wastewater treatment plants. The process involves the addition of certain archaea or bacterial cultures — either naturally occurring or engineered — to accelerate the degradation of specific contaminants.

The success of bioaugmentation relies on introducing bacterial cultures that can outcompete existing microorganisms based on their preferred constituent availability. This targeted approach allows treatment facilities to address specific contamination challenges while improving overall system performance and stability.

Important Environmental Parameters

Before implementing a bioaugmentation strategy, plant operators must ensure optimal environmental conditions for microbial growth and activity. These include:

• Proper pH management. Maintaining pH levels between 5.5 and 8.5 is essential for bacterial viability and metabolic activity. This range supports the majority of beneficial treatment microorganisms while preventing the dominance of problematic species.

• Nutrient balance. A Chemical Oxygen Demand to Nitrogen to Phosphorus (COD:N:P) ratio of 100:5:1 provides the right nutritional foundation for bacterial growth. It ensures that carbon, nitrogen and phosphorus are available in proportions that support healthy microbial communities without creating nutrient limitations.

• Alkalinity requirements. Alkalinity levels above 150 mg/L provide critical pH buffering capacity, preventing rapid pH swings that could stress or kill beneficial bacteria.

• Dissolved oxygen control. Maintaining dissolved oxygen levels between 0.5 and 5 mg/L creates the appropriate oxidative environment for aerobic biological processes while preventing over-aeration that could waste energy or damage microbial flocs.

• Retention time considerations. Proper solids retention time (SRT), or mean cell residence time (MCRT) management, is important for different biological processes. Nitrification requires SRT greater than 7 days, while heterotrophic bacteria for BOD removal need a minimum retention time of 2 hours.

During system upsets, operators should test for inhibitory compounds, including quaternary ammonium, peracetic acid and hydrogen sulfide. Microscopic examinations can help determine overall biological health and identify any deficiencies in the treatment system.

Strategic Dosing Practices

Advancements in biological carriers and preservation techniques have altered bioaugmentation dosing procedures. For example, modern dry bacterial formulations no longer require pre-hydration before addition to treatment systems, simplifying the dosing process.

Effective bioaugmentation should follow a two-phase dosing strategy to establish and maintain optimal microbial communities. The initial 7-day seed dosage period uses higher bacterial concentrations to quickly establish the desired microbial community. This approach allows the introduced bacteria to acclimate to local conditions and begin competing with existing microorganisms. Following successful inoculation, lower maintenance dosages sustain the established bacterial populations.

Optimal Dosing Locations

Proper dosing location can impact the success of bioaugmentation. Operators should add the bacteria to well-mixed and aerated areas as close to the influent as possible, ensuring maximum contact time with the wastewater stream. When conventional dosing points aren’t available, the return activated sludge (RAS) line serves as an excellent alternative inoculation point, providing good mixing and distribution throughout the biological treatment system.

If a scheduled dose is missed, operators should add the missed amount to the following day's dosage rather than attempting to maintain the original schedule, preventing gaps in bacterial supplementation.

Learn More

By following these guidelines and maintaining proper system conditions, public and industrial wastewater treatment plants can improve the efficiency of contaminant removal and enhance their system stability. 

Ready to optimize your bioaugmentation strategy? Take the guesswork out of dosing and try our bioaugmentation calculator.

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Bioaugmentation Dosing FAQs

What is bioaugmentation and how does it work?

Bioaugmentation is the addition of archaea or bacterial cultures to wastewater streams to speed up the rate of contaminant degradation. Degradation occurs through the competition and colonization of select cultures, which outcompete existing bacteria based on preferred constituent availability.

What are the ideal environmental conditions for successful bioaugmentation?

Several key parameters must be maintained for optimal results:

• pH should be between 5.5 and 8.5.

• COD:N:P Ratio of 100:5:1.

• Alkalinity greater than 150 mg/L.

• Dissolved Oxygen between 0.5 mg/L and 5 mg/L.

• SRT or MCRT with SRT greater than 7 days for nitrification, and greater than 2 hours for heterotrophic or BOD removal.

How should bacteria be dosed in the treatment process?

Due to advancements in biological carriers, operators no longer need to add dry bacteria to water prior to the treatment process. Dosing typically starts with a seed dosage over 7 days followed by a maintenance dosage. The seed dosage is higher than the maintenance dosage and is tailored to change the overall biological community, allowing for quick acclimation and improved treatment effectiveness.

Where should bacteria be added to the system?

Operators should add bacteria to a well-mixed and aerated part of the process as close to the influent as possible. If there is not a convenient dosage point, the RAS line is a suitable inoculation point.

What should I do if I experience system problems or miss a dosage?

If you’re experiencing an upset, test for a known inhibition like Quaternary Ammonia, Peracetic Acid or Hydrogen Sulfide. Conduct a micro exam to determine overall biological health and identify any deficiencies. If you miss a dosage, just add it to the next day’s dosage.