EVALUATION OF INNOVATIVE LONG-TERM NITRATE MANAGEMENT SOLUTION FOR BIOSOLIDS APPLICATION FIELDS

Groundwater nitrate contamination originated from 20 years of biosolids application from a municipal wastewater treatment facility applied at a 269-acre (109-hectare) site in Columbus, Georgia. The long-term application of biosolids has resulted in elevated concentrations of nitrate (20 to 300 mg/L nitrate as nitrogen) in the shallow groundwater beneath the site. A conceptual plan for long-term management and continued operations of the biosolids application fields is currently being considered by the Georgia Department of Natural Resources – Environmental Protection Division (EPD). The conceptual plan is based on the successful demonstration of nitrate reduction from a pilot-scale field test using enhanced in situ biodenitrification and on-site column studies to measure biodenitrification rates using three different amendments: sodium acetate, emulsified soybean oil (EOS™), and hydrogen gas.The results of the pilot-scale field test were used to demonstrate the viability of biodenitrification of the site groundwater. The column studies were completed to quantify biodenitrification rates specific to the site. The on-site column study combined the benefits of control provided in a laboratory with the benefits of a field application by minimizing variables inherent with in situ applications while still utilizing site groundwater and indigenous microbial populations.The data collected in both the pilot-scale field test and the on-site column studies allowed for the development a site-specific and innovative nitrate management plan. The conceptual nitrate management plan utilizes a series of downgradient groundwater extraction wells to both capture and contain nitrate-impacted water prior to off-site migration. The nitrate-impacted groundwater is to then be conveyed to the wastewater treatment plant where an ex situ biodenitrification tank will be utilized to irreversibly destroy the nitrate.