Production of the cyanobacterium Phormidium bohneri in parallel with epuration of a dairy anaerobic effluent

Abstract

The nutrient removal and growth capacity of the cyanobacterium Phormidium bohneri were studied on dairy anaerobic effluent. Among the three concentrations of effluent used (30, 40 and 50 mg NNH 3 litre −1), the highest growth rate (0·58 d −1) and final biomass (565 mg dry mass litre −1 after 16 days) were found in the more dilute effluent. The removal rate of ammonium nitrogen during the first 6 days was similar for all treatments and was equal to 3·1 mg NNH 3 litre −1 d −1. In contrast, the rate of removal of phosphorus was proportional to the amount of phosphate present in the medium, with a maximum value of 4·9 mg PPO 4 3− litre −1 d −1. The cellular concentrations of chlorophyll a and phycobiliproteins were followed as a function of time. In all treatments a decrease in chlorophyll a content, from 1·8 to 0·7% of the dry mass, was observed. In contrast, after an initial decrease from 9·6 to 4·0% of the dry mass, the content of phycobiliproteins increased during the next 6–8 days of growth to reach about 6·0% of the dry mass after 10 days. It is concluded that the growth of P. bohneri on dairy anaerobic effluent is feasible for the production of a useful biomass in parallel to tertiary treatment.