Results at a Glance
This case study examines how Apex helped a manufacturing facility reduce municipal water consumption by reusing deionized (DI) system reject water as cooling tower make-up. By implementing a controlled blending strategy and optimizing cooling water chemistry, the facility reduced freshwater demand by approximately 40% and achieved annual water savings of roughly 7.3 million gallons while maintaining stable cooling tower performance.
Manufacturing facilities operating in water-stressed regions face increasing pressure to reduce freshwater consumption, manage discharge volumes, and meet sustainability goals without compromising system reliability. Cooling towers, which require large volumes of make-up water, often present significant opportunities for reuse — provided water quality and chemistry are properly managed.
A large electronics manufacturing facility in Arizona was experiencing rising municipal water costs and growing concerns around long-term water availability. At the same time, its deionized (DI) water system generated a substantial volume of reject water that was discharged to sewer. The facility partnered with Apex to evaluate whether this reject stream could be safely reused to offset cooling tower make-up demand.
Results at a Glance
~7.3 Million Gallons of Annual Water Savings
Municipal Water Use Reduced by ~40%
Stable Cooling Tower Operation with Minimal Chemical Adjustment
Facility Background
- Industry: Manufacturing
- Application: Water Reuse for Cooling TowerÂ
- Primary Issue: High municipal water use and DI reject discharge in a water-stressed region
- Apex Solution: DI reject reuse strategy with blending, infrastructure upgrades, and chemical optimization
The facility operates in a high water-stress region of Arizona and relies heavily on municipal supply. Its DI water system generated 15–25% reject water, approximately 20,000 gallons per day, which was previously discharged to the sewer. At the same time, cooling towers required roughly 50,000 gallons per day of make-up water due to evaporation and blowdown. The site needed a reuse solution that would reduce water use and discharge while complying with Arizona Department of Environmental Quality (ADEQ) reuse regulations and maintaining stable cooling tower operation.
The Challenge
The facility faced several interconnected challenges:
- Rising municipal water costs in a high-stress region
- Significant volumes of DI reject water sent to sewer
- High cooling tower make-up demand
- Regulatory considerations related to water reuse
- Operational concerns about blending reject water and its impact on tower chemistry and performance
Any reuse strategy needed to be both technically sound and operationally reliable.
The Apex Solution
Apex worked closely with the facility to design and implement a DI reject reuse program tailored to cooling tower operation.
Key elements of the solution included:
- Diverting DI reject water to the cooling tower make-up system
- Testing and blending reject water with municipal supply at a 60:40 ratio
- Installing dedicated piping, flow control valves, and a 5,000-gallon holding tank for flow management
- Adjusting the chemical treatment program to accommodate the blended water, including scale inhibitor dosing and pH buffering
- Implementing real-time monitoring of pH, conductivity, and Langelier Saturation Index (LSI)
The program was designed to maximize water reuse while maintaining stable cooling tower performance.
Results & Operational Impact
Six months after implementation, the facility achieved measurable and sustained improvements:
- Municipal water use decreased from ~50,000 GPD to ~30,000 GPD
- DI reject discharge to sewer dropped from ~20,000 GPD to less than 1,000 GPD
- Annual water savings reached approximately 7.3 million gallons
- Cooling tower efficiency remained stable
- Chemical adjustments were minimal after initial optimization
The project also supported the facility’s broader sustainability roadmap, helping advance its 30% water reduction goal by 2030.
Applicable To
This solution is relevant for:
- Manufacturing facilities operating in water-stressed regions
- Plants with DI or RO systems generating reject water
- Facilities seeking cooling tower make-up water reuse opportunities
- Operations pursuing sustainability and water conservation goals
Conclusion
This Arizona manufacturing facility’s success demonstrates how strategic water reuse can deliver both environmental and economic benefits. By reclaiming DI reject water for cooling tower make-up, Apex helped the facility reduce freshwater demand, lower discharge volumes, and maintain reliable system performance in a water-constrained region.
For manufacturers facing water scarcity, rising utility costs, or sustainability mandates, Apex delivers practical reuse solutions grounded in chemistry, compliance, and operational confidence.
Frequently Asked Questions
Can DI reject water be safely reused in cooling towers?
Yes. When properly blended and treated, DI reject water can be reused as cooling tower make-up without causing scaling, corrosion, or operational instability.
Does reuse require major infrastructure upgrades?
Not necessarily. In this case, reuse was enabled through targeted piping additions, a holding tank, and control valves rather than large-scale system modifications.
How is cooling tower chemistry protected when using blended water sources?
Chemistry is managed through adjusted treatment programs and continuous monitoring of key indicators such as pH, conductivity, and LSI.
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