Effect of a hydrolytic/acidogenic pre-stage on the organic matter content of wastewater treated in a sequencing batch reactor for biological phosphorous removal

An increase of 52.7% in acetate concentration was observed when urban waste water was used to feed a pilot-scale upflow-type, fixed-bed fermentor under a hydraulic retention time of 0.78 h. The fermentor influent and effluent were successively used to feed a laboratory-scale sequencing batch reactor (SBR) using similar operational variables of wastewater volume, sludge purg ing volume and retention times during the anaerobic and aerobic phase, givi ng a nominal 4 h hydraulic retention time. The fermentor effluent contained an organic substrate, with a volatile fatty acid content higher than 50 mg L-1, which was appropriate for the growth of the type of microorganisms ch aracteristically found in biological phosphorous removal (BPR)systems, and showed the behaviour of an easily and rapidly biodegradable wastewater. The specific rate of phosphorous release at the anaerobic stage was found to b e higher than 0.04 mg P-r g VSS-1 min(-1), when the fermentor effluent is u sed as feed of the SBR, which demonstrated its favourable conditions for an efficient processing in this type of systems.