Establishing a functional biological community for wastewater treatment is essential when starting a new plant. Monitoring the developing biology during startup provides the insight plant staff need to adjust operations and achieve high treatment efficiency.
Settleometer testing of aeration basin effluent in activated sludge processes can indicate whether the biomass will settle properly or cause bulking in the system. From the evaluation of settleometer readings and facility mixed liquor suspended solids (MLSS) concentrations, operators can calculate sludge volume index (SVI) values that describe biomass settleability.
SVI values are variable in activated sludge systems, but Jenkins et al. (2003) found that sludge bulking occurs at SVI values greater than 150 mL/g.¹
The following case study outlines the startup of a 1 MGD integrated fixed-film activated sludge (IFAS) process using ProBiotic Scrubber® II (PBII) as a seed culture.
A wastewater treatment facility in Colorado, serving 6,600 people, needed an upgrade to its existing infrastructure. The original mechanical plant was built in 1956 and was last upgraded in 1985. Over 25 years, the plant had deteriorated to the point where effluent ammonia levels were exceeding permit limits.
This was an issue because the facility’s effluent was released into the Arkansas River, an essential water resource for downstream farmers and municipalities. To bring the plant discharge back into compliance, facility management decided to add a new treatment train to the existing system.
The facility added an IFAS process that had a higher treatment capacity than the old trickling filter plant. After construction was completed, the system needed to be seeded with the proper biology for efficient wastewater treatment.
The operators were hesitant to seed the new IFAS process with activated sludge from the old plant. They did not want to transfer the same treatment issues from the existing system to the new one. Because of logistical concerns and expenses, the project engineer decided to use BioLynceus® PBII to start up the plant.
The IFAS process was inoculated with PBII in the aeration basin under low-flow conditions. After 10 days of treatment, the biomass in the new process had aggregated and was ready to begin processing the full influent load.
Figure 1. Settled sludge volume (SSV (grey)), settled sludge concentration (SSC (blue)) determined from aeration basin effluent sampling throughout the first month of IFAS operations. SSVs of the wastewater samples were recorded over 60 minutes in a settleometer test. MLSS were acquired on settleometer
testing days. SSC values were calculated using the SSVs and MLSS.
Settleometer testing was conducted throughout the first month of IFAS system operations. The results from the settleometer tests showed that SSV decreased over time while SSC increased. These parameter trends indicated proper settling in the aeration basin effluent.
Additionally, SVI values were calculated from the 30-minute SSV for each settleometer test. The average SVI value during the first month of operations was 130 mL/g, which was below the threshold associated with poor biomass settling.
After adding PBII for one month, operational reports showed that the clarifiers were fully functioning and that the discharge was within NPDES limits. The PBII treatment provided the facility with an optimal biomass for wastewater processing.
The system was working so efficiently that the plant was selected as the Wastewater System of the Year in 2013 by the Colorado Rural Water Association.
1 Jenkins, D., Richard, M.G., Daigger, G.T., 2003. Manual on the Causes and Control of Activated Sludge Bulking, Foaming, and Other Solids Separation Problems. Lewis Publishers, Boca Raton, FL.
BioLynceus® ProBiotic Scrubber® II is an effective biological seed for IFAS system startups.