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

Parkway WWTP and Henrico County WRF
Laurel, Maryland and Richmond, Virginia

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. This paper has demonstrated secondary impacts from supplemental carbon addition for nitrogen removal. The benefits demonstrated included improved biological phosphorus removal, improved anoxic zone performance, increased biosynthesis for P and N removal, lower residual DO in the internal recycle, and improved utilization of influent rbCOD. Additionally various ways of calculating by the CODadded/Nremoved ratio was developed using effluent TN with and without supplemental carbon. The impact of lower NOx-N load in the RAS when the pre-anoxic zone is not fully utilized was shown to be a significant factor in the resulting CODadded/Nremoved ratio. These impacts illustrate the importance of considering the whole system response rather than an isolated portion of a reactor when evaluating supplemental carbon. Source: WEFTEC 2009 Proceedings

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Posted: August 27th, 2010 | Filed under: 50k-100k, Waste Water Treatment | Tags: Environmental Impact, Improved Anoxic Zone Performance, Lower Residual DO, Nitrogen Removal, Phosphorus Removal | 1 Comment »

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