Engineering Practice of Enhanced Pretreatment of Recirculating Cooling Sewage by Dehardening and Desalting
Industrial recirculating cooling sewage is difficult to treat.The recirculating cooling sewage of a cogeneration company faced problems such as large water volume,high hardness,high total phosphorus(TP),refractory and biorefractory content.To allocate water resources rationally,reduce the use of raw water,and increase the reuse of reclaimed water,a combined process of high-density sedimentation,ozone catalytic oxidation,and biological aerated filter(BAF)was adopted to enhance the pretreatment of recirculating cooling sewage.By this process,effluent COD was reduced from 134 mg/L to 55 mg/L,TP from 3.64 mg/L to 0.61 mg/L,and total hardness was reduced by half from 728 mg/L to 385 mg/L,respectively.Notably,the COD and TP met the direct discharge limits for new enterprises specified in the Emission Standard of Pollutants for Synthetic Resin Industry(GB 31572-2015),and the total hardness complies with the Standards for Drinking Water Quality(GB 5749-2022).The pretreatment cost of the sewage was 1.45 yuan/m3,significantly lower than the water supply fee of 3.62 yuan/m3 in the industrial park.
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