Characteristics of Tertiary Treatment on Complex Chemical Secondary Wastewater

Biochemical characteristics of chemical secondary effluent in tertiary treatment were studied with a piloted system of biological contact aerators to meet limits of national discharge. The results showed that biochemical characteristics of the secondary effluent had higher concentrations of residual COD and NH₃-N, as well as lower residual concentrations of BOD₅ and alkalinity. Residual COD in the effluent consisted mainly of three parts included the non-biodegradable COD presented by organic matter of toxicity, the soluble COD presented by BOD₅, and the particulate COD presented by SS. Under conditions of most non-biodegradable COD concentration of 132.70 mg/L and less alkality of 1.50mmol/L, COD concentration was decreased less than 100 mg/L, and NH₃-N effluent concentrations were decreased from 30.44 mg/L to 14.79 mg/L, and a scientific basis of reference was provided for reforming the pulse flocculated clarifier system which can meet limits of national discharge.