Water is an essential commodity and in many instances, needs to be treated before it becomes fit for consumption either by humans or industries. Water treatment thus is one of the most common processes that is used across many sectors like municipalities, power plants, petrochem plants and process plants that use water either directly for drinking purpose and fire protection systems, or indirectly as in cooling systems as input for further processing like demineralization. Originally conceived and implemented at Motorola as an improvement tool for manufacturing industry, Six Sigma is a set of proven methods that have found widespread implementation and have successfully optimized processes even in the service sector. This paper is a case research which presents the implementation of the Six Sigma methodologies like DMAIC and SIPOC over a period of one year, in the context of minimizing process costs of a water treatment plant. The paper uses experimental laboratory data and correlates with the implementation in the water treatment plant under dynamic conditions. The results of the successful optimization reveal that cost savings on chemicals come to an impressive 18%. [ABSTRACT FROM AUTHOR]