Can We Operate Deep Bed Denitrification Filters with Limited Phosphorus?
Abstract:Back River Wastewater Treatment Plant (Baltimore, MD) adds waste pickle liquor to the secondary influent (MLE Process) to meet its final effluent total phosphorus (TP) limit of 0.20 mg/L bringing the orthophosphate in the secondary effluent to below detectable levels (<0.05 mg/L). The plant plans to install Deep Bed Denitrification Filters (DBDF) to meet future effluent total nitrogen goal of 3.0 mg/L that corresponds to ≤0.5-1.5 mg/L NOx-N from current 8-10 mg/L in the secondary effluent. Nitrogen removal of this magnitude will require addition of phosphorus in the DBDF influent. Ferric Chloride will be added for trimming phosphorus in the DBDF effluent increasing the total suspended solids (TSS) in this train. This additional TSS will have to be removed at the existing shallow bed sand filters that follow the DBDFs. Minimizing the amount of supplemental P without affecting the DBDF performance will reduce the costs for supplemental phosphorus and the ferric chloride used for trimming phosphorus. Minimizing supplemental phosphorus also minimizes the additional TSS loading to the shallow bed sand filters. In order to verify the phosphorus demand and the impacts of limiting phosphorus on the operation of the DBDF, pilot testing was performed on a small-scale DBDF at the Back River plant during July-August, 2009. It was demonstrated that DBDFs could be operated without supplemental phosphorus without compromising the performance most of the time except when loading was increased. This was analogous to other attached growth systems like MBBR where P-limitation was observed only when temperatures were decreased significantly.
Document Type: Research Article
Publication date: January 1, 2010
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