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IMPACT ON DISINFECTION AT PEAK FLOWS DURING BLENDING/PARTIAL BYPASSING OF SECONDARY TREATMENT
Citation:
STINSON, M. K., R. I. FIELD, AND R. RUKOVETS. IMPACT ON DISINFECTION AT PEAK FLOWS DURING BLENDING/PARTIAL BYPASSING OF SECONDARY TREATMENT . Presented at 2008 WORLD ENVIRONMENTAL & WATER RESOURCES CONGRESS, HONOLULU, HI, May 13 - 16, 2008.
Impact/Purpose:
to inform the public
Description:
A U.S EPA study evaluated the impact on disinfection during peak flows when a portion of the flow to the wastewater treatment plant (WWTP) bypasses secondary treatment prior to disinfection. The practice of bypassing secondary treatment during peak flows, referred to as blending, takes place when the volume of primary treatment exceeds the capacity of the secondary treatment. This is considered a measure to avoid passing excess flow to the secondary treatment, which would result in inactivation or destruction of the vulnerable biological process of secondary treatment. The bypassed flow is only treated by sedimentation before it is recombined with the fully treated secondary effluent prior to disinfection. This practice raises the concern that the disinfection process is compromised and public health may be jeopardized.
The study was conducted at three WWTPs in New York City, ranging from 60 MGD to 275 MGD. A total of four dry-weather and 12 wet-weather events were sampled and analyzed. Three samples from four sampling points of the treatment train in the WWTP were taken per event. The principal analytical parameters were fecal coliform, Entercoccus, E.Coli, viruses, and protozoa. Other parameters were total residual chlorine, BOD, TSS, and particle size distribution.