As water resources become increasingly stressed by drought and intensifying demand from competing uses, industries that use significant quantities of water will face greater pressure to adopt water-efficiency strategies that can decrease fresh-water withdrawals. In industrial operations, cooling towers present a viable opportunity for water conservation. Traditionally, the vast majority of industrial plants that operate open evaporative, recirculating cooling systems rely on municipally supplied water of potable quality, on-site well water or locally available surface water (adjacent rivers/lakes) as the principal makeup water source. One approach that facilities can adopt to reduce their draw from these supplies — thus reducing stress on drinking water reserves — is to use alternative makeup water sources.
This analysis focuses on the evaluation and best practices application of four major alternative source options: sodium zeolite softened water, reverse osmosis (RO) permeate, high phosphate gray water and municipally treated wastewater. The concept of mitigating fresh-water usage by utilizing a nontraditional makeup water supply is readily welcomed at many U.S. facilities. However, difficulties emerge when performing a cost/benefit analysis of a selected option and, subsequently, the implementation of a project in terms of defining the practical method of application to an existing open evaporative cooling system.