EFFECT OF A HYDROLYTIC/ACIDOGENIC PRE-STAGE ON THE ORGANIC MATTER CONTENT OF WASTEWATER TREATED IN A SEQUENCING BATCH REACTOR FOR BIOLOGICAL PHOSPHOROUS REMOVAL

Abstract

An increase of 52.7% in acetate concentration was observed when urban wastewater 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 purging volume and retention times during the anaerobic and aerobic phase, giving 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 characteristically 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 be higher than 0.04 mg P _r g VSS⁻¹ min⁻¹, when the fermentor effluent is used as feed of the SBR, which demonstrated its favourable conditions for an efficient processing in this type of systems.

Keywords:

• Hydrolitic/acidogenic pre-stage
• Volatile fatty acids
• Urban wastewater
• Sequencing batch reactor
• Biological phosphorous removal

ACKNOWLEDGMENT

The authors wish to thank the ‘Comisión Interministerial de Ciencia y Tecnología (CICYT)’, Project PETRI no. 95-0118-0P, for providing financial support.