Combined biodegradation of carbon, nitrogen and phosphorus from wastewaters

The objective of this study was to develop an integrated system for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The system consisted a two step anaerobic digestion reactor for carbon removal coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed system, carbon is converted into biogaz by methanogenic activities. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion were used as electron donors for biological dephosphatation in the SBR in which anaerobic and aerobic phases were cyclically applied. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrate from the SBR is added to the acidogenic influx. The proposed process was fed with a synthetic wastewater with composition characteristics: Total Organic Carbon (TOC)=2200 mg l −1; Total Kjedahl Nitrogen (TKN)=86 mg l −1; Phosphorus under phosphate form (P–PO 4)=20 mg l −1). In these conditions, the removal of carbon, nitrogen and phosphorus were 98%, 78% and 95%, respectively. The benefits from the system are the saving of (i) an external carbon source for denitrification and dephosphatation, (ii) a reactor for the denitrification step.