TREATMENT OF OIL-WATER EMULSIONS

Abstract

Oily waste is one of the major pollutants in the environment, producing from large number of industries. Among them vegetable oil industry is one of the major contributor of waste in the form of oil-water emulsion. It is necessary to treat the oily waste before discharging to water bodies inorder to meet the stringent environmental standards, As per MINAS standards, oil & grease, it's 10 mg,/1 in general and specifically for vegetable oil industries it's 20 mg/1. Various methods for oil removal are such as adsorption, chemical coagulation, floatation, filteration and electrocoagulation. The objective of the present work is to treat the oil-water emulsion by using different coagulants like concentrated acid, alum and poly aluminum chloride (PAC) and to present the comparision of coagulants on oil removal efficiency. Oil-water emulsions are generated in oil extraction and processing plant so for this purpose soybean and peanut oil, which are commonly used in food processing industries, soap industries and in polymer industries, were taken to make synthetic oil-water emulsion by sonication method from 1 to 4 % (v/v) oil. All the chemical coagulants used, were found pH dependent. The optimum flocculation pH for oil removal, have been found 'to be 6.0 for alum and 7.0 for PAC SAB-18 in case of soybean oil-water emulsion, and 8 for alum in case of peanut oil-water emulsion. Among the various coagulants alum was found more effective than other two coagulants. Single stage treatment has been found to be inadequate for all three coagulant. Only by alum treatment it was possible to meet prescribed limit i.e. 10 mg/1 after second stage treatment, it was not possible to achieve the desired standard with PAC and concentrated acid even after second -stage iv treatment. No change in oil concentration was observed even after second stage treatment in case of concentrated HC1 acid. The effect of temperature on oil-water stability shows that stability is highly dependent on temperature and was found to decrease with increase in temperature.