Short and long-term experiments on the effect of sulphide on 1 microalgae cultivation in tertiary sewage treatment . 2

11 Microalgae cultivation appears to be a promising technology for treating nutrient-rich 12 effluents from anaerobic membrane bioreactors, as microalgae are able to consume 13 nutrients from sewage without an organic carbon source, although the sulphide formed 14 during the anaerobic treatment does have negative effects on microalgae growth. Short 15 and long-term experiments were carried out on the effects of sulphide on a mixed 16 microalgae culture. The short-term experiments showed that the oxygen production rate 17 (OPR) dropped as sulphide concentration increased: a concentration of 5 mg S·L 18 reduced OPR by 43%, while a concentration of 50 mg S·L came close to completely 19 inhibiting microalgae growth. 20 The long-term experiments revealed that the presence of sulphide in the influent had 21 inhibitory effects at sulphide concentrations above 20 mg S·L in the culture, but not at 22 concentrations below 5 mg S·L. These conditions favoured Chlorella growth over that 23 of Scenedesmus. 24