AEROBIC TREATMENT OF WASTES CONTAINING COOL CUT OIL

Abstract

Waste water from a number of industries, such as oil refinery, automobile, metal working, dairy contains substan-tial amount of oils and greases. Depending upon the process operation, oil in waste water may be present either in floating or miscible form. The free oil can be easily separated out by conventional gravity separation devices. However, for miscible oil, it is essential that oil-water emulsion must be de-emulsi-fied to get free oil, which can be easily separated out by conventional oil separation processes. Waste water from metal working shop, contains cutting oil. Cutting oil consists of mineral oils and fatty acids, which are completely miscible with the water. Because of its high solubility with water, oil in the emulsion cannot be separated effectively by conventional oil separation methods. Some special physico-chemical or biological methods are requ-ired to separate the emulsified oil. Various physico-chemical methods have been tried,but because of high organic content and wide range of physical and chemical characteristics of the wastewater from metal working shop, a biological method is supposed to be more efficient. In the present investigation, an attempt has been made to study the effect of mixed culture, obtained from municipal sewage, on the degradation of organic matter present in the oily waste water. The experiments have been carried out to study the effect of temperature, pH, nutrient, aeration, and initial inoculum on the reduction of the COD of waste water containing cool cut oil. The results show that at 30°C and pH 4.0, about 76% reduction in COD is obtained in 96 hrs., when the initial COD of the waste water is 560 mg/l. On increasing the aeration rate from 15 1pm to 35.3 1pm, about 6% increase in COD is obtained. There is a substantial increase in the COD reduction with increase in ammonium biphosphate dose, and the inoculum to substrate ratio. From the present study, we conclude that waste water containing cool cut oil can also be treated effectively with aerobic waste water treatment system, however, the rate of reduc-tion of organic matter is less than that of domestic