THE BEST BANG FOR THE BUCK: MAKING THE MOST OF AVAILABLE INFLUENT CARBON FOR NUTRIENT REMOVAL

摘要

The premise of this paper is that, even if influent carbon is insufficient to meet effluent nutrientlimit requirements, it will be cost effective to make as much use of it as possible, beforesupplemental carbon is added. Many North American designs include primary anoxic zones thatare too small to use the full denitrification potential of the secondary influent carbon. For theMLE process, nitrogen removal progressively increased up to primary anoxic volumes that are45% the total reactor volume, and up to 400% IMLR flow. The limit to performance withincreasing anoxic volume or IMLR flow is the point where NOx-N is reduced to zero in theanoxic zone. The required anoxic volume to maximize performance, and the associated IMLRflow depends on the secondary influent carbon/nitrogen ratio. In this study performanceimproved in the MLE process until the BOD_5/ammonia-N reached 5.7, beyond which no furtherimprovement occurred. Of the configurations evaluated for nitrogen removal, the Four-StageBardenpho process produced the lowest effluent TN. For combined phosphorus and nitrogenremoval, the MUCT process produced the lowest effluent TP, but the highest TN.