Cultivation of native algal consortium in semi-continuous pilot scale raceway pond for greywater treatment coupled with potential methane production

The native algal consortium, collected from wastewater pond, was grown in greywater and the process was scaled up in open ponds raceway (800 L). It showed good growth along with removal of various nutrients concentration such as ammonia, nitrate, dissolved phosphate and sCOD below safe discharge limits, in both batch (flask study) and raceway ponds. The algal biomass thus obtained was rich in lipid (45.87% TS). The estimated theoretical methane potential was 745.87 mL CH4 g−1 VS while experimental cumulative yield of up to 630 mL CH4 g−1 VS (calculated based on the VS conversion into methane during anaerobic digestion) was observed during 30 d anaerobic digestion of algal biomass. The digestibility of the algal biomass was low (37%) with only 44% volatile solid reduction. The tested consortium has good potential for wastewater treatment coupled with substantial biomass production. However, further attempts for pretreatment and codigestion are essential to improve the methane yield and digestibility of the tested algal biomass.