Influence of pH and CO2 source on the performance of microalgae-based secondary domestic wastewater treatment in outdoors pilot raceways

Abstract

The influence of pH (7, 8 and 9) and CO2 source (pure CO2 or CO2 from flue gas) on both the performance of secondary domestic wastewater treatment and biomass productivity and composition in three outdoors pilot raceways was evaluated for 6months. Average COD, TN, TP and Escherichia coli removal efficiencies of 84±7%, 79±14%, 57±12% and 93±7%, respectively, were recorded. The influence of pH on wastewater treatment was negligible, while the supply of CO2 from flue gas supported higher COD, TOC and TP removals. Biomass productivities ranged from 4±0gm-2d-1 in December to 17±1gm-2d-1 in July. The highest C, N and P biomass contents (64.8%, 12.6% and 2.4%, respectively) were recorded when flue gas was supplied. Finally, while the protein content in the biomass remained constant (38.2±3.3%), the lipid and carbohydrate contents ranged from 5.8% to 23.0% and from 38.0% to 61.2%, respectively.