Integration of microalgae cultivation and anaerobic co-digestion with dairy wastewater to enhance bioenergy and biochemicals production

A sequential anaerobic digestion and phycoremediation process was employed to recover nutrients and remove pollutants from dairy wastewater (DW), while simultaneously producing biomethane and biochemicals. Anaerobic digestion of 100% DW achieved a methane content and production rate of 53.7% and 0.17 L/L/d, respectively. This was accompanied by the removal of 65.5% chemical oxygen demand (COD), 86% total solid (TS), and 92.8% volatile fatty acids (VFAs). The anaerobic digestate was then used to grow Chlorella sorokiniana SU-1. Using 25% diluted digestate as the medium, SU-1 could reach 4.64 g/L biomass concentration, with total nitrogen (TN), total phosphorus (TP) and COD removal efficiencies of 77.6%, 87.1% and 70.4%, respectively. The obtained microalgal biomass (contained 38.5% carbohydrates, 24.9% proteins, 8.8% lipids) was used to co -digest with DW, resulting in good methane production performance. Co-digestion with 25% (w/v) algal biomass obtained a higher CH4 content (65.2%) and production rate (0.16 L/L/d) than other ratios.

Automated summary

A sequential anaerobic digestion and phycoremediation process was used to recover nutrients and remove pollutants from dairy wastewater while producing biomethane and biochemicals. The anaerobic digestion achieved a methane content of 53.7% and production rate of 0.17 L/L/d, along with significant removals of chemical oxygen demand, total solids, and volatile fatty acids. The digestate was then used to grow Chlorella sorokiniana SU-1, resulting in high removal efficiencies of total nitrogen, total phosphorus, and COD. The microalgal biomass obtained was co-digested with dairy wastewater, leading to improved methane production performance.