California University Reduces Water Consumption Through Blowdown Reuse

While the State of California was experiencing a drought in 2015, a southern California university made the decision to treat cooling tower blowdown for reuse at the campus cogeneration plant. The university hired an engineering firm to assist with design specifications and proper integration of the treatment system into the facility. U.S. Water was selected as the equipment supplier and collaborated with the customer and engineering firm through the remaining phases of the project. The project resulted in a reduction in water used by the cooling tower system, providing cost savings for the university.

During the design and implementation phases of this project, the team had to consider the high levels of hardness and dissolved solids in the municipal water supply, a major challenge of water treatment in the region. When used as a cooling tower make-up source, dissolved solids in municipal water concentrate in the recirculating water. These concentrated solids must be released from the tower via “blowdown”, which is a critical water treatment component that protects against fouling of heat exchange surfaces. At a plant such as this, blowdown water volume totals several million gallons of water per year that is discharged to sanitary sewer. The goal of the project was to reduce overall water consumption by reusing cooling tower water that would otherwise be discharged as blowdown waste.

Another unique challenge in this area was environmental factors, such as Santa Ana winds, wildfires, and nearby freeways, which tend to increase suspended solids within the cooling tower and in water released as blowdown. For this reason, it was important to implement a versatile system that takes into account varying water quality. The ease of adjustments and modifications to system operation proved vital in allowing the university to meet project goals.

In order to treat the complex water chemistry to project specifications, U.S. Water designed a system that combined Ultrafiltration (UF) and Reverse Osmosis (RO). The system was designed to allow water from the cooling tower to flow through a strainer to remove large suspended solids upstream of the UF/RO system, then advance to the UF membranes as pre-treatment for the prevention of particulate fouling of the RO membranes. The process concludes with high quality permeate water from the RO flowing back into the cooling tower, having removed 99% of the impurities.

Starting up in 2016, the water reuse system has reduced the university’s potable water use by approximately 18 million gallons. In 2019, the project was a finalist for the Water Efficiency Project of the Year, hosted by Los Angeles Better Building Challenge. In conjunction with other programs and initiatives that focus on creating a sustainable future for southern California residents, the university is well on the way to realizing its potential to reduce water consumption by 30 million gallons per year.

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