Life cycle analysis of water resource recovery facilities based on algae-bacteria processes

International audienceMicroalgal biomass production using industrial wastewater offers the possibility of recycling industrial residues, while reducing pollutants discharge to natural environments and creating new sources of raw materials. This study analyzes the environmental impacts of microalgae production in an open raceway system fed by effluents from an anerobic digester, i.e., digestate (for N and P source) and CO2 from the biogas upgrade process. The ALBA model is used for simulating a large-scale High Rate Algal/Bacterial Pond (HRABP) with a membrane separation system. The analysis focuses on maximizing the algal productivity and N intake fraction in the algal biomass by assuming three scenarios associated to different HRT (hydraulic residence time) and SRT (solid residence time) hypotheses. Scenario 3 (HRT= 5 d, SRT= 10 d) presents the highest productivity but lower performance in terms of N and P removal. It also results in the lower environmental impact for the 3 Endpoint categories evaluated. Scenario 1 (HRT= 90 d, SRT= 15 d) offers the best performance in N and P removal rates but has a lower productivity and highest. Moreover, it requires a large production area. Scenario 2 (HRT= 10 d, SRT= 5 d) has similar values for productivity and removal rates of N and P with scenario 3performs the lower impact in CC, with similar values for the other categories to scenario 1. An HRT of 5 d exhibit the best performance with high biomass productivity, high removal rates of N and P, lower environmental impacts and a reduced demand of production pond area