Secondary Impacts of Supplemental Carbon Addition to BNR/ENR Treatment Processes

Nitrogen removal to increasingly strict discharge standards requires, in many cases, the use of supplemental carbon (methanol, glycerol, acetate, sugar water, etc). The supplemental carbon provides the driving force for further biological denitrification and is typically applied as a polishing treatment such as to a post anoxic zone or a tertiary denitrification filter. The practical use of supplemental carbons has attracted substantial attention from both process optimization and cost minimization perspectives. This paper presents the operational experiences gained with the secondary and indirect impacts of supplemental carbon addition to BNR/ENR treatment facilities at the Parkway WWTP, located in Laurel, Maryland, and at the Henrico County WRF, located in Richmond, Virginia. The focus of the paper deals with the sometimes unexpected beneficial secondary effects of supplemental carbon addition to post anoxic zones in the BNR/ENR treatment processes.