THE EFFECTS OF SULFIDE GENERATION IN WASTE STABILIZATION PONDS ON PHOTOSYNTHETIC POPULATIONS AND EFFLUENT QUALITY

This study concerns the role of sulphide production in the reduction of algal populations and proliferation of purple sulphur bacteria in primary waste stabilization ponds, and the effect of such changes on effluent quality and hydrogen sulphide odour release. Full-scale ponds in Israel were compared to laboratory-scale models fed with domestic wastewater at various organic and sulphate loads. The phenomenon occurred in ponds whose organic loads were between those normally thought appropriate to facultative and anaerobic ponds. Algae of the genus Chlamydomonas were most tolerant of sulphide in ponds, confirming previous in vitro studies. Populations of both photosynthetic groups in the models were related to surface BOD5 loading rates and influent sulphate and sulphide concentrations. Purple sulphur bacteria were unable to prevent all odour release, so situations where they proliferate should be avoided by redesign. Shifts from algal to purple sulphur bacterial dominance caused by increased sulphide concentrations under constant loads were not observed to affect adversely effluent quality in terms of BOD5 and COD.