(778f) Cooling Tower Wastewater Treatment and Reuse

Cooling towers are ubiquitous across many industries, from large-scale power generation to commercial buildings. Cooling towers consume large volumes of water due to evaporative and windage/drift losses. To limit the accumulation of dissolved and suspended solids (and thus to mitigate mineral scaling, corrosion, and biological growth) in cooling water systems, periodic discharge of cooling water (i.e., blowdown) is needed, contributing to additional loss of cooling water that must also be replenished. Applications of advanced membrane treatment technologies (ultrafiltration (UF) and reverse osmosis (RO)) for cooling tower wastewater (CTW, i.e. blowdown water) treatment and reuse, while environmentally and economically desirable, remain limited. CTW treatment and reuse reduce blowdown water loss, while at the same maintain cooling water quality at levels necessary for effective mitigation of cooling water system corrosion/scaling. In the present work, a fundamental computational framework was developed to quantify and assess the operational costs and benefits of CTW treatment via integrated UF-RO processes. Potentially effective UF-RO operational strategies for CTW treatment were assessed and their optimal process conditions were identified. The potential benefits of advanced adaptive UF-RO operation that optimally handles fluctuations in cooling tower system conditions and UF-RO operational costs (e.g., cooling water quality, peak/non-peak electricity costs) were examined, including both steady-state and intermittent operational modes. Examination of UF-RO process operational requirements for CTW treatment will be presented focusing on the results of a recent field study using a novel UF-RO pilot system operation in a co-generation plant at the University of California, Los Angeles. Results from the field study demonstrated both a significant level of water savings as well as monetary savings for the facility. The overall analysis approach and field study results demonstrate that there is a range of scenario for beneficial CTW treatment and reuse, which would be best served by a self-adaptive treatment process.