Frequent and irregular fluctuations in the resistivity of ultrapure water are often rooted in biological contamination within the piping system, with over 80% of these hidden faults originating from this internal contamination. When ultrapure water systems operate continuously for extended periods, or are frequently started and stopped without maintenance, bacteria easily proliferate on the inner walls of pipes, the inner walls of the pure water tank, and in various dead-end connections. This bacteria gradually form a stubborn biofilm with strong adhesion, continuously releasing impurities and microorganisms into the water, constantly polluting the downstream pure water. Conventional filter replacement and chemical cleaning of the RO membrane only address the impurity trapping problem in the pretreatment unit; they cannot completely remove the deep-seated biological contamination within the piping. This is the core reason why many companies find their water quality unstable even after repeatedly replacing all consumables. Furthermore, EDI ultrapure water equipment has extremely high requirements for the quality of the incoming water and the cleanliness of the entire piping system. Microbial contamination in the downstream piping directly interferes with the deep desalination effect of the EDI module, ultimately causing large and irregular fluctuations in resistivity.
Ultrapure Water Equipment
For these typical malfunctions, Xi'an DIEN Water Treatment can customize exclusive pipeline sterilization retrofit solutions, adaptable to various configurations of EDI ultrapure water equipment systems. First, the entire pure water system is shut down and the stored water is drained. A food-grade, residue-free disinfectant is used to perform closed-loop disinfection of all points, including the pure water tank, main delivery pipelines, various valves, and dead corners at joints, thoroughly removing stubborn biofilms adhering to the inner walls of the pipelines and killing all residual bacteria. Second, the original pipeline layout is optimized to completely eliminate dead water areas within the system. A circulating pressure stabilizing unit and a matching ultraviolet sterilization device are installed to achieve 24-hour dynamic continuous antibacterial action. Finally, the entire process operating parameters of the equipment are readjusted, residual agents in the pipelines are flushed at high flow rates, and the online resistivity monitoring instruments are calibrated to ensure that the final effluent water quality consistently meets standards. The entire retrofit does not require significant changes to the original equipment structure, has a short on-site construction period, and low subsequent operation and maintenance costs, fundamentally solving the water quality problem of frequent fluctuations in ultrapure water resistivity.
Local Retrofit Case Study: Xi'an Electronics Factory Ultrapure Water System Sterilization Retrofit Project
A precision electronics processing plant in Xi'an High-tech Zone, equipped with EDI ultrapure water equipment specifically for chip wafer cleaning, recently experienced a fault where the resistivity of the ultrapure water fluctuated wildly, repeatedly jumping between 15-18 MΩ·cm. This directly led to minor defects in the cleaned products, resulting in a continuously rising production defect rate. The company's maintenance team had repeatedly replaced the entire set of filter cartridges and performed offline cleaning of the reverse osmosis membrane components, but the problem could not be completely resolved.
Our technicians conducted a comprehensive system-wide inspection and troubleshooting, ultimately determining that the core cause of the fault was the lack of dedicated pipeline sterilization over a long period. A large area of biofilm had grown on the inner walls of the pipelines, continuously releasing impurities into the final pure water, causing secondary pollution. Subsequently, the DIEN project team implemented a complete pipeline sterilization retrofit, completing closed-loop disinfection of the entire system, optimizing and eliminating pipeline dead zones, installing end-point UV sterilization devices, and simultaneously recalibrating and adjusting the operating parameters of the EDI equipment. After the upgrade was completed, water quality data was tracked for a week. The resistivity of the water output from the equipment remained stable in the range of 18.2-18.25 MΩ·cm, and the water quality was completely stable and met the standards. The equipment operated smoothly throughout the process, which completely solved the problem of water quality fluctuation that had plagued the company for a long time and provided a reliable guarantee for the continuous and stable production of the production line.
