Evaluation of Crude Glycerin as a Supplemental Carbon Source for a High Rate Step-Feed BNR Process

The use of crude glycerin was evaluated as an alternative supplemental carbon source to methanol to enhance denitrification in a step-feed BNR process. Two of the four pilots were integrated with separate centrate treatment tanks to oxidize centrate ammonium; centrate was fed to the head of the step-feed process in two other pilot systems. The pilot treatment trains received primary effluent and centrate from the 26th Ward WPCP. Under normal operating conditions, it was demonstrated that crude glycerin could be used to achieve 5-10 mg/L of final effluent TN. Specific denitrification rates determined by the bench-scale batch tests were comparable to that achieved with methanol as the supplemental carbon source. A COD-to-N ratio in the range of 6 to 7 grams/gram was used, resulting in a chemical cost of ∼ 1/kg-NOx-N removed with a cost basis of 0.22/L, compared to ∼ 1.60/kg-NOx-N for 100% methanol at ∼ 0.40/L.