A low-cost wastewater treatment facility for milking center wastewater using handy FRP silos

With the purpose of developing a low-cost wastewater treatment facility for milking center wastewater having enough wastewater purification capacities, we produced a wastewater treatment facility using handy FRP silos, and inspected its purification capacities for about two years. The wastewater treatment facility consisted of seven tanks, i.e. a collecting tank, an aeration tank, a settling tank, and four aerobic biological contactor tanks, and was made by a handy FRP silo (each volume was 2.6 square m) each. In the facility, wastewater was treated by a combination of activated sludge process and biofirm process. To cut costs, crude styrene foam pellets, which are one of recycled marerials of plastic waste, were used as biological contactors. Under the condition that approximately 1 square m/d of milking center wastewater (average properties: BOD 1,833mg/l, COD 570mg/l, SS 597mg/l, n-hexane extracts 233mg/l, total nitrogen 69mg/l, total phosphorus 16mg/l) flowed into the treatment facility, more than 95% of BOD, COD, SS and n-hexane extracts in the wastewater were removed, so that those concentrations in the treated water were much lower than the effluent standard value of the Water Pollution Prevention Law. Total nitrogen and phosphorus were not removed well by the treatment, although the concentrations of those substances in the treated water were lower than the effluent standard. Average removal efficiencies of total nitrogen and phosphorus were 72.5% and 44.0%, respectively. The construction cost of this treatment facility was estimated at about 910,000 or 1,2900,000 yen, respectively, in case of self-construction or maker-construction. Therefore, the treatment facility could be construct at much lower than facilities on the market. The running costs were estimated at about 13,500 yen as electric bills for the aeration blowers.