Effect of coagulation flocculation and sand & gravel filtration on the quality of car wash waste water

Car wash water contain dirt, surfactants and oil & grease which contaminate the air, land and natural water resources. Waste water samples from 12 different car wash service stations were collected and tested for the physiochemical parameters of TDS, TSS, turbidity, pH, BOD, COD sulphate, salinity, conductivity and oil and grease. TSS, turbidity and COD values were above the NEQ'S standard values for the effluent discharge. A laboratory treatment, comprised of coagulation flocculation followed and sand and gravel filtration was used to treat the waste water. The treated water was analyzed for the above mentioned parameters. Comparison of the treated water and untreated waste water showed a 100 % reduction in TSS, COD, BOD, sulphate and oil and grease. Turbidity was reduced by 98 %, TDS by 48 %, conductivity by 42 %, and pH by 3.7 %. Salinity however showed no response to the treatment method applied. The results obtained in this study are important and may be used for onward design of a treatment and recycling process for actual car wash stations.