Severe drought inspired a southern California university to explore their water use and to implement aggressive sustainability goals. Treatment and reuse of cooling tower blowdown water was instrumental in their water action plan, and Kurita America has played a key role in this effort.
Southern California is population-dense and water-scarce. Although the bottom two-thirds of the state accounts for 80 percent of California’s water demand, it receives only 25 percent of the state’s rainfall. This leads to the energy-intensive practice of transporting water from northern California and from out-of-state to supplement the locally available resources. The limited supply and great distance of travel makes water an expensive commodity with inherent uncertainties.
During California’s last major drought, which began in 2012, the southern California university evaluated their water use and committed to reducing consumption of municipal water by 36 percent per capita by 2025 with an interim target of 20 percent by 2020. Their water audit identified a substantial waste stream at their cogeneration plant, which provides heating, cooling, and electricity to much of the campus. Over 27 million gallons of cooling tower blowdown water was being sent to the sewer each year. What if the university could recover some of that water through treatment and reuse?
The university had no lack of ideas on water reuse. Some local professors were aware of a technology that could help, and they designed a membrane treatment system that uses ultrafiltration followed by reverse osmosis (RO) to treat the cooling tower blowdown, which could then be recycled as make-up cooling water. This would significantly reduce waste discharge volume while minimizing draw from the municipal potable water supply.
Kurita America has worked with the university for over 20 years to help manage their water systems at the cogeneration plant, so Kurita America was uniquely situated to supply the treatment equipment and provide the necessary support. Although pilot testing determined the process feasibility, time was necessary to optimize full-scale operational conditions and establish cleaning regimens that would recover the most water while extending the life cycle of costly consumables.
Water is lost through evaporation during the cooling process, which causes dissolved solids to concentrate in the recirculated water. If left unchecked, then this will cause deposition and corrosion, which will impact process efficiency and equipment life. While chemical treatment can mitigate this to reduce water use, blowdown is necessary to maintain concentrations below a terminal threshold. As water is lost from blowdown and evaporation, an equal amount of make-up water is introduced to maintain the cooling water flow rate.
The cooling process increases the concentration of hardness and dissolved solids above the natural levels in the municipal potable water supply, which the university uses for make-up. The open cooling system promotes biological activity and allows entry of fine solids and debris blown in by the Santa Ana winds from nearby freeways and area wildfires. Concentrations and rates of accumulation are affected by seasonal variations in cooling requirements. Reflecting these inherent and site-specific factors, the blowdown water at the southern California university had a high fouling potential with fluctuating levels of suspended solids, which would add operational complexity to the membrane treatment processes. Meeting the reuse goals would require a flexible and robust system operation with a keen awareness of the varying water quality and seasonal demands.
The anticipated challenges proved formidable, and Kurita America worked closely with the university to integrate the new treatment process into their cooling system. This included close attention to the cooling water treatment program as it is inherently linked to the reclamation system. For example, sodium hypochlorite is used to control biofouling in the cooling system, but the chemical is incompatible with RO membranes. When manually adjusted to respond to system variability, there were frequent chlorine residual peaks that triggered automatic shutdown alarms on the reclamation system. A Lumyn™ controller was added to automatically adjust chemical feed based on real-time measurements, which maintained consistent chlorine residuals to prevent concentration spikes and ensure continuous operation of the reclamation system. The precision control also benefited the cooling system by ensuring adequate biological control while preventing the overuse of chemicals.
Since it was started up in 2016, the reclamation system has been reducing the university’s water footprint, and in 2019, the project was a finalist for the Water Efficiency Project of the Year hosted by the Los Angeles Better Building Challenge. In 2021, the university reclaimed 13.7 million gallons of cooling tower blowdown, exceeding their annual goal of 12 million gallons, which furthermore yielded a net operational savings of over $125,000 by the way of reduction in water utility costs.
The university met their 2020 campus-wide water reduction target and are on track for 2025 in part because of the reclamation system. However, no single project alone can be credited, and meeting these ambitious goals required a comprehensive effort spanning the university’s entire water-related infrastructure. This is true for the greater community, and no single entity alone can solve water scarcity. We can all follow the university’s example to share in the solution.
For more information on how Kurita America can help reduce water consumption in your facility, contact us or call 866-663-7633.
About the Authors
Throughout his near decade long career in water treatment technology, Patrick Freeman has focused on water and energy conservation that delivers increased output and cost reduction for his customers through improved system operation and efficiency. Prior to this, he earned a Bachelor of Science degree in Biochemistry from Arizona State University and worked in the laboratory industry with a focus on soil, groundwater, and wastewater contamination. His extensive knowledge of water chemistry proved invaluable while gaining experience in water technology solutions for cooling, boiler, and wastewater applications for facilities in the power, healthcare, entertainment, industrial, and large commercial industries. Patrick has assisted his customers with installation, startup, and on-going service of equipment solutions, such as reverse osmosis (RO), multimedia filtration (MMF), ultrafiltration (UF), water softening, deionization (DI), and monochloramine generating systems, while developing and utilizing appropriate controls/automation for each application. His experience also includes large construction projects in both the design, construction, and start-up phases, and expertise extends into the application of domestic water secondary disinfection and other Legionella prevention measures.
T.J. Stroebl is a technical marketing leader at Kurita America, specializing in equipment systems. After earning a chemical engineering degree from the University of Minnesota, he has spent his career with Kurita America focusing on process and equipment design, troubleshooting, and development relevant to water treatment systems. T.J. is an active member of the American Water Works Association (AWWA), currently serving as vice chair on the Manufacturers/Associates Council (MAC).