Improving Wastewater Biomass Stability During High Infiltration and Inflow
Wastewater systems with high infiltration and inflow (I&I) often experience hydraulic overloading, which can disrupt biomass stability and reduce treatment efficiency. Excess I&I can also limit the capacity of wastewater collection systems and treatment infrastructure.¹
When stormwater, groundwater, or snowmelt enters the collection system, wastewater flows can increase significantly. These higher flows may hydraulically overload the treatment plant and dilute the organic carbon available to the microbial population.
Organic carbon is an important food source for the microorganisms responsible for biological wastewater treatment. When carbon levels become too low, microbial growth and metabolism can slow, making it more difficult for the treatment system to process wastewater efficiently.
High I&I can also make it more difficult for wastewater treatment facilities to remain in compliance with state and federal water quality requirements.
The following case study describes how Candy Carbon® (CC) was used at a 2 MGD activated sludge plant to help support biomass stability following I&I-related washout events.
High I&I Causes Biomass Washouts
A 2 MGD activated sludge plant in a mountainous region of Arizona experienced treatment problems following heavy precipitation and spring snowmelt.
After large volumes of stormwater or snowmelt entered the collection system, organic carbon concentrations at the treatment plant decreased. The diluted wastewater provided less food for the microorganisms responsible for biological treatment.
Facility operators suspected that increased I&I was contributing to these recurring biomass disruptions.
To support biological treatment during high-flow conditions, plant staff began adding an organic carbon source to the return activated sludge (RAS) stream.
However, the original carbon product required a high application rate and produced only limited improvements in biomass recovery.
Seeking a more effective organic carbon supplement, the plant supervisor contacted the wastewater specialists at BioLynceus®.
Figure 1. Google Earth Image of the 2 MGD ASP experiencing washout
events due to I&I.
1 National Small Flows Clearinghouse West Virginia University. (1999,
spring). Infiltration and Inflow can be Costly for Communities. Pipeline,
10(2), 1-8.
Using Candy Carbon® During High-Flow Conditions
The activated sludge plant began injecting Candy Carbon® into the RAS stream during periods of elevated infiltration and inflow.
After the first two applications, operators noticed that the wastewater biomass recovered more quickly from I&I-related washout events.
The facility also required significantly less product to restore biological treatment.
According to the plant’s head wastewater operator, the facility applied approximately 75% less Candy Carbon® than the previously used carbon product.
The lower application rate made the treatment process easier and less time-consuming for plant personnel.
Results: Faster Biomass Recovery and Easier Treatment
Using Candy Carbon® helped the wastewater treatment plant maintain a more reliable organic carbon supply during periods of high infiltration and inflow.
The treatment program helped the facility:
- Reduce organic carbon product usage
- Shorten biomass recovery time
- Decrease application time
- Reduce product storage requirements
- Support biological treatment during hydraulic loading events
The facility continues to use Candy Carbon® during the winter and spring months, when precipitation and snowmelt increase the risk of I&I.
By providing an available organic carbon source during high-flow conditions, Candy Carbon® helps support biomass stability and improve the efficiency of the plant’s biological wastewater treatment process.
BioLynceus® Candy Carbon® provides organic carbon to support wastewater biomass.