Researches and Strategies on Advanced Treatment and Resources Recycling of Dairy Wastewater

Dairy wastewater is a typical food-processing wastewater. The direct discharge of dairy wastewater is easy to cause serious pollution of accepting water body due to its characters of large discharging amount, high organic content and weak water's quality stability. The advanced treatment and resources recycling of dairy wastewater have become a key to achieving the sustainable development of dairy industry. In this work, the current researches on the treating methods and resources recovery of dairy wastewater are reviewed. Though analyzing the advantages and application bottlenecks of various methods, a comprehensive strategy integrating foam fractionation, sequencing batch reactor (SBR) and membrane separation is proposed. Firstly, foam fractionation have been used to recover casein from dairy wastewater. The precipitates in the foamate could be used as the feed additives of livestock. The foamate could be served as the fermentation medium of microorganisms for synthesizing biofuels or constructing microbial fuel cells. Subsequently, SBR method is used to further reduce the chemical oxygen demand (COD), biochemical oxygen demand (BOD₅) and phosphate content in the effluent. Finally, the nitrites in the effluent of SBR are removed by using membrane separation and they would be used in biofertilizer production. The advanced treatment period of dairy wastewater in this strategy is short and the resources recovery from the concentrated solutions is easy to perform. Furthermore, the dilute solution of membrane separation could be used in circulation cooling operation and farm irrigation.