Treatment of sulphate containing yeast wastewater in an anaerobic sequence batch reactor

Anaerobic mesophilic fermentation of sulphate containing yeast industry wastewaters at laboratory scale with anaerobic sequence batch reactors (ASBR) was studied. Three different treat­ment schemes were investigated – ASBR with and without a polymeric filler and coupled micro­aerophilic/anaerobic SBR (CSBR). The optimal concentration of sludge (total solids 17.3 g L–1) in the reactor and the optimal reaction time (22 h) were determined. It was shown that in the case of ASBR efficient treatment characterized by chemical oxygen demand (COD) removal of 75–82% took place at volume loading rates up to 7.7–8.0 kgCOD m–3 d–1 and at COD/(SO4)2– ratio 8.0. In optimal conditions the methane content of the biogas was 60%. The best results for sulphate removal (99%) were achieved in the CSBR with the concentration of sulphide in the reactor effluent being about 10 mg L–1. Decreasing treatment efficiency after a long-time exploitation of these reactors occurred as a result of the formation of insoluble sediment (presumably CaCO3 and Ca3(PO4)2).