Changes of biotoxicity in food waste fermentation wastewater treated by a membrane bioreactor system

The biotoxicity of industrial effluents has attracted much concern in the wastewater treatment process. This research performed the biological treatment of the wastewater generated from food waste fermentation by anaerobic/anaerobic/anoxic/aerobic-membrane bioreactor (A³-MBR) system aiming at the meet of discharge standards and elimination of ecological risks to aquatic environment. The results showed that the A³-MBR could effectively remove pollutants such as COD, TN, ammonia, and TP in the wastewater. The study of biotoxicity revealed that the acute toxicity was mainly contained in the polar and mid-polar fractions of the wastewater, and the remained acute toxicity was less than 0.6 TU, much lower than the secondary effluent of domestic wastewater treatment plant. The genotoxicity was found abundantly in the polar fractions and less in mid-polar fractions, and a relatively low genotoxicity (0.086 μg 4-NQO/L) was obtained in the final effluent of the treatment system. The fulvic acid-like compounds and humic acid-like compounds were the main cause of the acute toxicity, while the aromatic proteins and soluble microbial by-products mainly resulted in the genotoxicity in the wastewater.