The metal working industries generate different kinds of waste waters as a result of processing metal parts/products, machinery, and other associated activities as well. The performing operations may have two types of activities: (a) manufacturing, and (b) rebuilding or maintenance. Actually, coolants are important component of metal working operations and it improves machinability, increases productivity and extends tool life by properly cooling and lubricating the parts and the cutting tools. But, the coolants get contaminated quickly with foreign materials, lose effectiveness and it may develop even foul odors. With a result, coolants may be used only for a short period and then it is normally discarded. In present context, a systematic and optimal disposal of metal industries wastes in the form of waste water or oil mixtures has become extremely important. This paper underlines the optimal disposal of metal working industrial waste water/oil mixtures with the help of operation research technique called Dynamic Programming.