Dairy industry wastewater generally has fats, lactose, whey proteins, and nutrients which lead play an important role to increase the biological oxygen demand (BOD) of water. With milk components also wastewater contain detergents and sanitizing agents which are the result of the cleaning process increases the concentration of chemical oxygen demand (COD). There are many ways to reduce the BOD and COD, but biological treatment is the primary mean. Both aerobic and anaerobic technologies have been used, while anaerobic treatment of wastewater has emerged as a viable and economical alternative over conventional aerobic treatment, particularly for high BOD. In aerobic technologies number of different treatment methods are there like, activated sludge, sequencing batch reactor, rotating biological contactors trickling filter. In anaerobic treatment methods are up-flow sludge blanket (UASB), anaerobic sequencing batch reactors (ASBR), continuous-flow stirred tank reactor, hybrid anaerobic digesters, contact reactor, up flow and down flow anaerobic filters, and two-stage systems that separate the acid-forming and methane forming. There are many cases where aerobic and anaerobic processes are combined in one single treatment system. Membrane technology is alternative to biotreatment being used for BOD reduction in dairy wastewaters which replaces secondary clarifiers in the waste treatment plants with membranes.