Production and Use of Short Chain Fatty Acids to Enhance the Via-Nitrite Biological Nutrients Removal from Anaerobic Supernatant

Abstract

The use of the different external carbon source was investigated to enhance the short-cut nitrification-denitrification (SCND) and the denitrifying phosphorus removal via nitrite (DPRN) using a sequencing batch reactor (SBR) to treat anaerobic supernatant. The SBR was fed with liquid effluent from the anaerobic co-digestion of waste activated sludge (WAS) and organic fraction of municipal solid waste (OFMSW). After the start-up period of 20 days, a stable and reliable via-nitrite pathway was achieved. Then, three available carbon sources (fresh drainage liquid from OFMSW, fermentation liquid from OFMSW, cattle manure and maize silage (CM&MS) fermentation liquid) were investigated. Significant in-situ specific denitritation rates (sNUR) in the range of 0.51-1.16 kgNO₂-N / kgVSSd were obtained for OFMSW and CM&MS related carbon sources. The specific consumptions obtained for the liquid effluents from OFMSW and CM&MS raged from 2.7-3.1 kgCOD / kgNO₂-N_rem. The presence of short chain fatty acids (SCFA), namely butyric and propionic acids in the fermentation liquid enhanced the DPRN. The cost of the external carbon source can be lower than 0.1 € / kgCOD when OFMSW is fermented. The total specific cost for nitrogen removal may decrease by 22% when the OFMSW fermentation liquid is used instead of methanol.