Pilot-scale experiments on brewery wastewater treatment and sludge reduction based on food chain predation

In a pilot-scale experiment, hydrolyzation-food chain reactor (H-FCR) system was used to treat brewery wastewater. The performance of the system, including COD, BOD5, NH3-N, SS removal, and sludge reduction, were investigated. The mechanism of sludge reduction and the characteristics of biological community during multilevel contact oxidation process were also explored. The food chain reactor (i.e. four-level contact oxidation reactor with a volume ratio of 4:3:3:2) was found to be contributory to the provision of a suitable environment for the formation of the food chain of bacteria–protozoa–metazoan–larger metazoan. The ratio of metazoan density to protozoa density and metazoan density to bacteria density increased gradually with COD concentration reduction along the flow direction. This change strengthened the role of predation in reducing sludge production from the source. The sludge production decreased to 8.15% kg suspended sludge/(kg COD removed). The formation of the food chain also provided ecological basis for the stable and efficient removal of contaminants. When the mass concentrations of COD, BOD5, NH3-N, and SS in influent water were 1585 ± 168, 711 ± 146, 43.1 ± 12.5, and 206.7 ± 53 mg/L, respectively; and when the hydraulic retention time of the H-FCR system was 11.7 h (5.2 h for the hydrolyzation segment and 6.5 h for the four-level contact oxidation segment), the average removal rate of the above four indicators were approximately 94.9, 97.9, 87.6, and 93.6%, respectively. Water quality of effluent conformed to discharge standard of pollutants for beer industry (GB 19821-2005). Therefore, the H-FCR system is an effective method for the treatment of wastewater from food industry, including breweries, because of its high efficiency, low consumption, and little excess sludge.