Abstract
Three different treatment technologies, namely mono-algae culture, algal-bacterial culture, and algal-fungal culture, were applied to remove pollutants form synthetic domestic sewage and to remove CO2 from biogas in a photobioreactor. The effects of different initial influent C/N ratios on microalgal growth rates and pollutants removal efficiencies by the three microalgal cultures were investigated. The best biogas upgrading and synthetic domestic sewage pollutants removal effect was achieved in the algal-fungal system at the influent C/N ratio of 5:1. At the influent C/N ratio of 5:1, the algal-fungal system achieved the highest mean chemical oxygen demand (COD) removal efficiency of 81.92% and total phosphorus (TP) removal efficiency of 81.52%, respectively, while the algal-bacterial system demonstrated the highest mean total nitrogen (TN) removal efficiency of 82.28%. The average CH4 concentration in upgraded biogas and the removal efficiencies of COD, TN, and TP were 93.25 ± 3.84% (v/v), 80.23 ± 3.92%, 75.85 ± 6.61%, and 78.41 ± 3.98%, respectively. These results will provide a reference for wastewater purification ad biogas upgrading with microalgae based technology.
Highlights
In rural areas of China, one of the main water pollution sources is domestic sewage, which contains abundant carbon, nitrogen, and phosphorus compounds
Study has shown that 85–88% of chemical oxygen demand (COD), 78–83% of total nitrogen (TN), and 73–80% of total phosphorus (TP) could be removed from wastewater by cultivating the algae Chlorella sp.[8]
These changes were similar under all tested influent C/N ratios
Summary
In rural areas of China, one of the main water pollution sources is domestic sewage, which contains abundant carbon, nitrogen, and phosphorus compounds. Many studies indicated that conventional water treatment processes, including oxidation ditch processes[2], anaerobic-anoxic-axic (A2/O)[3], University of Cape Town (UCT)[4], Bardenpho, and sequencing batch reactor (SBR)[5], achieved moderate success in removing pollutants These processes generally entail enormous land requirements, operational costs, complex operations, and large volumes of waste sludge production and are not practicable in rural areas in China. As an alternative for the purification of domestic sewage, biological wastewater treatment system using microalgae is currently attracting increased interest because of its low construction and maintenance costs, minimal energy consumption, freedom from spatial restriction during operation, as well as high removal efficiency[7]. The C/N ratio is vital to the growth of microalgae when cocultivation with fungi or bacteria
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