Energy recovery by anaerobic digestion of algal biomass from integrated microalgae/constructed wetland wastewater treatment

The present study evaluated the potential for biogas generation from microalgae (MA) biomass and macrophytes used in vertical flow constructed wetlands (VFCW). The samples were obtained by separation and collection of MA after a hydraulic retention time of 14 days, frozen and taken to the laboratory, while the macrophytes of VFCW were obtained, by pruning, every 6 months. The obtained results presented reductions of 63.22% and 61.18% for COD and BOD5, respectively, and removal efficiencies of 53.91% for TP and 99.98% de N-NH3. Average biogas generation was 2322.51 NmL-gSV(-1) with 54.61% CH4 (winter/2019), 4491.47 Nml-gSV(-1) with 57.17% CH4 (spring/2019), 680.78 NmL-gSV(-1) with 16.04% CH4 (summer/2020), and 681.0 NmL-gSV(-1) with 19.86% CH4 (autumn/2020) for MA biomass and generation of biogas of 3826.70 NmL-gSV(-1) with 44.26% CH4 for VFCW biomass in winter and spring/2019 and of 829.68 NmL-gSV(-1) with 17.06% CH4 in summer and autumn/2020. Regarding electricity generation, the present work obtained 1.50 kWh/m(3), therefore reaching similar values to other studies that used more traditional biomass sources.

Automated summary

The present study evaluated the potential for biogas generation from microalgae biomass and macrophytes used in vertical flow constructed wetlands. The results showed that this method can effectively degrade pollutants while producing usable biomass energy and biogas.