Biological nitrate removal using waste-derived extracts as sole carbon source

Waste-derived multicomponent extracts were investigated as carbon source for biological nitrate removal. Aerobic and anaerobic sludge from a municipal wastewater treatment plant and leachate from an anaerobic digester treating food waste were studied. Alkaline-heat treatment was used for sludge solubilisation. More than 90% carbon was recovered at pH 10–11. The extracts contain very high volatile fatty acids (VFAs), protein and carbohydrate. The protein/carbohydrate ratio was 2/1 for both aerobic and anaerobic sludge extracts and 9/1 for leachate. Of the total chemical oxygen demand (COD), 60% was solubilised in both the aerobic and anaerobic sludge extracts, while 80% was solubilised in the leachate. The extracts were successfully tested in batch experiments for different time intervals as a sole carbon source for biological nitrate removal in synthetic wastewater. More than 95% nitrate removal was achieved in 24 h batch studies at carbon-to-nitrate (C/N) ratio of 8 and at 35oC. The nitrate removal perfo...