TREATMENT OF WASTEWATERS FROM PARTS CLEANING OPERATIONS

Abstract

Poor management practices related to generation and disposal of untreated wastewater causes pollution of both surface and ground water bodies. Raw wastewater disposal from industry are some of the sources causing water pollution. Automobile industry particularly cleaning operations produce thick layered greasy wastewater that contains very high level of organic loads. Part's cleaning is an important process for organizations involved in manufacture, repair/maintenance of aircrafts, automotive, automobile and shipping facility. Parts are generally covered with heavy oils and solids which are removed prior to overhauling. An automobile overhauling facility located at Rawalpindi was selected as case study. Samples were collected and treatment studied from three sources within the facility (i.e. engine, transmission and body parts overhauling workshop). These wastewaters contained oil, high COD and solids. The study aimed at characterization of wastewaters from parts cleaning operations, designing a treatment system and study of economic effects of proposed system. Two types of oil contents were encountered i.e. free and emulsified oil. Wastewaters generated at locations where mechanical parts were being cleaned contained free oil. Separation of this oil was achieved using oil/water separator model. While the other workshop wastewater, where body parts were being cleaned, contained emulsified oil which was separated by chemical emulsion breaking/acid cracking. Commercial grade sulfuric acid was used to lower pH of wastewater to value less than or equal to 2 for this purpose. Solids removal was achieved through coagulation. Alum and calcium chloride were used as coagulants. High color was detected in body parts cleaning wastewater. Removal of color and remaining COD in this wastewater was achieved by mechanical emulsion breaking (activated carbon adsorption). Over 99 percent removal of contaminants was achieved in the treatment processes. Results revealed that wastewaters from these sources are treatable and pollution of water bodies can be minimized to NEQS limits. Moreover recycling of wastewater, after treatment, can achieve significant water conservation. Finally a treatment plant design was proposed for installation in the facility after considering its economic feasibility.