Seawater toilet flushing sewage treatment and nutrients recovery by marine bacterial-algal mutualistic system.

Seawater toilet flushing sewage with excess eutrophic and high salinity brought a great barrier on the municipal wastewater treatment plants. Nutrients recovery and biomass production as potential biofuel feedstock with less energy consumption will be a key challenge in wastewater treatment. In the optimal inoculation of algae and bacteria, a marine bacterial-algal mutualistic system was established to treat synthetic seawater toilet flushing sewage without extra carbon and O2 addition. It was showed that 85.5% of total nitrogen (TN) (from 200 mg/L), 91.0% of total phosphorus (TP) (from 40 mg/L) and 98.7% of chemical oxygen demand (COD) (from 1600 mg/L) were removed with 4.28 g/L of biomass yield (biomass productivity 159.3 mg/L/d) containing 16.3% lipid and 62.6% protein, which performance mainly achieved by bacteria during first six days and algae functioned subsequently. Both nitrogen and phosphorus removal of the system were mainly assimilation/accumulation. Algal facultative heterotrophia ensured dissolved organic carbon for bacterial utilization and avoiding excessive organic matter produced. The established algal-bacterial system provided a potential energy-efficient and eco-friendly approach for seawater blackwater treatment and nutrients recovery simultaneously.