ABSTRACT
This chapter assesses the effects of sulphide concentration on the anaerobic and aerobic physiology of polyphosphate accumulating organisms (PAOs). It provides new insights into the potential failure of enhanced biological phosphorus removal sewage plants receiving sulphate or sulphide rich wastewaters when sulphide concentrations exceed 8 mg dihydrogen sulphide-S/L. A PAO culture, dominated by Candidatus Accumulibacter phosphatis clade I, was enriched in a sequencing batch reactor fed with acetate and propionate. To assess the direct inhibition effects and their reversibility, a series of batch activity tests were conducted during and after the exposure of a PAO I culture to different sulphide concentrations. In order to assess to which extent the sulphide effects were reversible, fresh substrate was added to the biomass exposed to sulphide. Phosphate is transported over the membrane together with counter ions like potassium, magnesium and calcium. The direct inhibition effects of sulphide on the anaerobic/aerobic phosphate profiles were satisfactorily described with the proposed expressions.
