Efficient recycling of sewage water in a polyester integrated industry: A case study

The water reuse system in a petrochemical and polyester integrated industry in Zhejiang, designed to handle industrial circular sewage, had a capacity of 1600 m3/h. The system employed a process comprising a high-efficiency sedimentation tank, V-shaped filter, aerated biological filter, ultrafiltration, and reverse osmosis. The high-efficiency sedimentation tank's mud water drainage, along with pretreatment through the biological aerated filter (BAF), V-shaped filter, and ultrafiltration system, resulted in an overall system recovery rate of 70 %. Actual operational results indicated removal rates exceeding 70 % for chemical oxygen demand (COD) and 94 % for chloride ions. The effluent water had a COD of ≤ 20 mg/L, chloride ion concentration of ≤ 50 mg/L, and conductivity of ≤ 20 μS/cm. Given the high recovery rate and the use of domestically produced ultrafiltration membranes, the direct operational cost of the system amounted to a mere 6.28 yuan/m3. This led to a reduction of approximately 9.67 million tons of wastewater discharged annually, fulfilling the objective of recycling industrial sewage for reuse.