Restoring Wastewater Biomass After Infiltration and Inflow Washouts
Wastewater treatment systems in regions with high annual precipitation, such as the Pacific Northwest, are especially vulnerable to infiltration and inflow (I&I). Excess I&I can increase hydraulic loading and disrupt biological wastewater treatment.¹
Stormwater and groundwater entering the collection system can dilute the organic material in the influent and wash established biomass out of the treatment process. As a result, microorganisms may lose access to the food sources they need, while the structure of the biological community becomes less stable.
The following case study describes how ProBiotic Scrubber® II (PBII) and Candy Carbon® (CC) were used to restore biological treatment at an activated sludge plant following I&I-related biomass washouts.
High I&I Disrupts an Oregon Wastewater Treatment Plant
A 0.2 MGD municipal activated sludge plant in Oregon struggled to maintain a stable biomass after major storm events.
During periods of high infiltration and inflow, large volumes of rainwater entered the wastewater collection system. This diluted the influent biochemical oxygen demand (BOD) and contributed to biomass being washed out with the plant effluent.
As both the available food supply and microbial population decreased, treatment efficiency in the activated sludge basins declined significantly.
The plant needed a reliable way to restore biomass and increase the availability of organic carbon following these washout events.
Searching for an Alternative to Activated Sludge Seeding
Traditionally, additional activated sludge can be introduced into an aeration system to rebuild biomass after a biological upset.
However, plant supervisors understood that hauling and adding activated sludge could be expensive and time-consuming. It could also introduce unwanted microorganisms or create additional treatment challenges.
For these reasons, facility management wanted an alternative method for restoring biological wastewater treatment.
The plant contacted BioLynceus® to develop a bioaugmentation program for its specific operating conditions.
1 National Small Flows Clearinghouse West Virginia University. (1999, spring). Infiltration and Inflow can be Costly for Communities. Pipeline, 10(2), 1-8.
Figure 1. 0.2 MGD activated sludge plant oxidation ditch biological treatment supported by applications of Probiotic Scrubber® II and Candy Carbon®.
Bioaugmentation with PBII and Candy Carbon®
BioLynceus® recommended a dual treatment program using ProBiotic Scrubber® II and Candy Carbon®.
PBII was applied to provide a concentrated source of wastewater microorganisms and help rebuild the plant's biological population.
Candy Carbon® was added to increase the availability of organic carbon, providing an additional food source to support the newly introduced microbial community.
The treatment program was applied to the activated sludge basins following high-I&I events that caused biomass washout.
Results: Biological Treatment Restored
Within a few days of treatment, the activated sludge plant was once again effectively processing incoming wastewater.
The restored biomass settled properly and supported biological nutrient removal. The combination of ProBiotic Scrubber® II and Candy Carbon® provided the facility with a practical method for recovering from major infiltration and inflow events.
By rebuilding the microbial population and increasing available organic carbon, the bioaugmentation program helped stabilize biological treatment after I&I-related washouts.
BioLynceus® ProBiotic Scrubber® II and Candy Carbon® help stabilize biomass in activated sludge systems.