Customized double-pass RO plus EDI and polishing mixed bed solution for high-purity photovoltaic production water

In the photovoltaic and energy storage industry, ultrapure water is a critical utility for cell production, equipment cleaning, rinsing, and other precision manufacturing processes. Water containing dissolved salts, hardness, residual chlorine, particles, or microorganisms can affect product quality, reduce production stability, and increase the risk of defects or contamination on sensitive process lines.

To support its manufacturing requirements, a photovoltaic energy storage enterprise in China selected Zhongnuo Water Treatment to design and manufacture a 36 m3/h ultrapure water system. The customized solution was developed to convert municipal tap water into stable high-purity process water, helping the client strengthen water quality control, protect precision equipment, and maintain reliable large-scale production line operation.

As production capacity expanded and process quality standards became stricter, the client required a more advanced and stable water purification system. The key project challenges included the following:

◎  High-purity water demand was large and continuous

Photovoltaic production lines require a significant and stable supply of high-purity water. The client needed a system capable of delivering 36 m3/h continuously to support multiple process points without interrupting production.

◎  Municipal feed water still required multi-stage deep purification

Although municipal tap water is relatively stable, it still contains dissolved solids, residual disinfectants, hardness, organics, and fine particles. These impurities had to be removed through carefully staged pretreatment, RO, EDI, and final polishing to meet photovoltaic manufacturing expectations.

◎  Water quality consistency was essential for process control

For precision industrial production, fluctuations in water purity can affect rinsing performance, equipment cleanliness, and process repeatability. The system therefore needed to deliver stable final water quality across long operating cycles.

◎  Final distribution quality had to remain protected

Even after deep purification, the water still required hygienic storage and final polishing before entering production points. This made UV sterilization, polishing mixed bed treatment, and terminal filtration important parts of the complete solution.

Municipal Tap Water  ->  Raw Water Tank  ->  Raw Water Pump  ->  Multi-media Filter  ->  Activated Carbon Filter  ->  Softening Water Filter  ->  Salt Tank  ->  Security Filter  ->  First-stage High Pressure Pump  ->  First-stage RO System  ->  First-stage Pure Water Tank  ->  Second-stage High Pressure Pump  ->  Second-stage RO System  ->  Second-stage Pure Water Tank  ->  EDI Booster Pump  ->  EDI System  ->  UV Sterilization  ->  Ultrapure Water Tank  ->  Water Supply System  ->  Polishing Mixed Bed  ->  Terminal Filter  ->  Production Line Water Points

This 36 m3/h ultrapure water system was designed specifically for photovoltaic industry process water requirements. It integrates pretreatment, double-pass reverse osmosis, EDI polishing, final sterilization, mixed bed refinement, and terminal filtration into a complete high-purity water supply solution.

Comprehensive pretreatment for membrane protection

The process begins with the Raw Water Tank and Raw Water Pump, followed by a Multi-media Filter to reduce suspended solids, an Activated Carbon Filter to remove residual chlorine and organics, and a Softening Water Filter with Salt Tank support to reduce hardness and scaling risk. A Security Filter then provides fine particle protection before the first RO stage.

Double-pass RO for strong desalination performance

The First-stage High Pressure Pump and First-stage RO System remove the majority of dissolved salts and impurities. Water is stored in the First-stage Pure Water Tank and then sent through the Second-stage High Pressure Pump and Second-stage RO System for deeper purification, creating a cleaner feed for the downstream EDI unit.

EDI and final polishing for ultrapure water quality

After the second RO stage, the EDI Booster Pump feeds water into the EDI System for continuous ion removal and higher purity performance. The treated water then passes through UV Sterilization, enters the Ultrapure Water Tank, and is delivered through the Water Supply System to a Polishing Mixed Bed and Terminal Filter before reaching production line water points.

Designed for large-scale photovoltaic production

The complete system was configured to support stable high-capacity operation, reliable final water purity, and effective protection of downstream photovoltaic manufacturing processes. It is suitable for industrial users that require continuous high-purity process water at a larger production scale.

After installation and commissioning, the ultrapure water system successfully met the client’s production water requirements and provided stronger water quality assurance for its photovoltaic manufacturing lines.

· Stable ultrapure water output of 36 m3/h for production use.

· Improved consistency of high-purity water supplied to photovoltaic process lines.

· Reduced dissolved salts, hardness, particles, and contamination risk in process water.

· Better protection for precision cleaning, rinsing, and equipment operation.

· More reliable support for continuous large-scale industrial production.

· Stronger final water quality control through UV, mixed bed polishing, and terminal filtration.

With the new system in operation, the client achieved a more dependable ultrapure water infrastructure and improved support for long-term process stability, product quality, and plant expansion.

With extensive experience in industrial high-purity water treatment, Zhongnuo Water Treatment provides customized systems based on source water quality, target purity, plant layout, and production objectives. For photovoltaic manufacturers, our strengths include:

· Tailored double-pass RO plus EDI system design for high-purity industrial applications.

· Integrated purification planning from pretreatment through final mixed bed and terminal filtration.

· Practical automation and monitoring solutions for stable continuous operation.

· One-stop support covering design, equipment supply, commissioning, and application service.

1. Why does photovoltaic manufacturing require ultrapure water?

Ultrapure water helps reduce process contamination risk, supports precise cleaning and rinsing, and improves the consistency of sensitive photovoltaic manufacturing operations.

2. Why use both double-pass RO and EDI in this system?

Double-pass RO provides deep desalination before the EDI stage, while EDI further removes ionic contaminants to achieve higher purity and more stable final water quality.

3. What is the role of the polishing mixed bed and terminal filter?

The polishing mixed bed further refines final water quality, and the terminal filter helps protect the production line from any residual fine contaminants before the water reaches process points.

4. Can this system be customized for different factory capacities?

Yes. Zhongnuo Water Treatment can customize capacity, pretreatment layout, RO staging, EDI configuration, polishing steps, and final water targets according to the user’s production requirements.