Suitability of Extended Aeration Plants for BNR Retrofits: A Case of Tripling Rated Capacity

The conversion of an extended aeration plant to modified Ludzack-Ettinger (MLE) process coupled with the construction of a dedicated septage receiving facility required the tripling of the plant contaminant processing capacity. Conversion to the MLE process affected a 55% reduction in annual average SVIs to about 126 ml/g, 75% reduction in alum dosage (on a molar basis), and 23% reduction in electrical power consumption. Biological nitrogen removed increased from 27 tons N in 2006, comprising 34% of the influent total nitrogen to 136 tons N or 67% of the influent nitrogen in 2008. The MLE achieved more stable nitrification throughout the year than the former extended aeration plant.