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

- The effect of sulphide over a microalgae culture was studied.
- Experiments at lab-scale (short-term) and pilot-scale (long-term) were performed.
- Microalgae activity was reduced with increased sulphide concentration.
- In long-term experiments, low sulphide did not significantly inhibit microalgae.
- The presence of sulphide favoured the growth of Chlorella instead of Scenedesmus.

Microalgae cultivation appears to be a promising technology for treating nutrient-rich effluents from anaerobic membrane bioreactors, as microalgae are able to consume nutrients from sewage without an organic carbon source, although the sulphide formed during the anaerobic treatment does have negative effects on microalgae growth. Short and long-term experiments were carried out on the effects of sulphide on a mixed microalgae culture. The short-term experiments showed that the oxygen production rate (OPR) dropped as sulphide concentration increased: a concentration of 5 mg S L−1 reduced OPR by 43%, while a concentration of 50 mg S L−1 came close to completely inhibiting microalgae growth.The long-term experiments revealed that the presence of sulphide in the influent had inhibitory effects at sulphide concentrations above 20 mg S L−1 in the culture, but not at concentrations below 5 mg S L−1. These conditions favoured Chlorella growth over that of Scenedesmus.