Project Name: Hardware pretreatment wastewater Project Description: pretreatment of metal and iron parts (after pickling + powder spraying) Process flow: wastewater collection +ph regulation + primary sedimentation +ph regulation + secondary sedimentation + sand filtration carbon filtration + ultrafiltration Emission index: 4m3 / h Discharge standard: the requirements of class I standard in period II of the local standard of Guangdong Province "discharge limits of water pollutants" (db44/26-2001). Enterprises have emission standards for high COD, phosphorus, ammonia nitrogen, SS suspended solids and petroleum; The process of feizhiwei is acid pickling, phosphating and. COD concentration is not high, mainly for phosphorus removal. At present, the operation is reliable and stable, reaching the emission standard required by Dongguan environmental protection department.