CONVERTING CONVENTIONAL FILTERS FOR DENITRIFICATION AT THE NEUSE RIVER WASTEWATER TREATMENT PLANT

The City of Raleigh's Neuse River Wastewater Treatment Plant is a 60 mgd advanced treatment facility that consistently meets stringent NPDES permit limits. In response to water quality problems in the summer of 1995 in the Lower Neuse River, the City of Raleigh and Hazen and Sawyer conducted a denitrification filter pilot study at the plant in 1996 and 1997 using one of the existing effluent filters as a denitrification filter by adding methanol to the filter influent. The results of the pilot study indicated that reduction of total nitrogen is possible by adding methanol to an existing dual media effluent filter.Due to the positive results achieved in the pilot study, the City of Raleigh proceeded with modifications to their existing effluent filters to provide denitrification. Construction was completed in late 2000. The project cost approximately 4 million and included replacing dual media with monomedia, increasing media depth from 2.5 feet to 4 feet, and reprogramming the filter PLCs to automatically perform nitrogen release cycles. The filter upgrade at the Neuse River WWTP has resulted in reduced total nitrogen in the plant's effluent.