Residential Secondary Water Supply Disinfection Project2

Overcome the residual chlorine assurance bottleneck in the "last mile" of water supply.

Secondary water supply is the terminal stage of the urban water supply system — and also the node where water quality safety risks are most concentrated. Some pump station tanks in Suzhou's urban area experience long retention times, leading to hidden issues such as residual chlorine decay and microbial growth. The traditional passive model of "flush and disinfect once every six months" struggles to cope with the rapid residual chlorine decline during high-temperature summer periods. How to provide continuous, stable booster chlorination for secondary water supply tanks — without large-scale renovation of existing pump stations — became an urgent technical challenge for Suzhou Water Supply Company.

Smart Sodium Hypochlorite Generator for Tank Booster Chlorination

Suzhou Water Supply Company's Water Production Branch, in accordance with the requirements of Jiangsu Province's "Technical Regulations for Residential Secondary Water Supply Engineering," selected a smart sodium hypochlorite generator as the tank booster chlorination method, completing pilot installation and trial operation at Nanhuan Huilin Plaza. The device produces sodium hypochlorite on-site through salt water electrolysis and can automatically adjust dosing based on tank outlet residual chlorine data. It features minimal limitations and low energy consumption — suitable for both routine distribution network booster chlorination and emergency water quality treatment. This model complements Suzhou's urban secondary water supply technical approach of "UV-chlorine combined disinfection," providing a flexible water quality assurance option for pump stations under different conditions.

Proven Stable Residual Chlorine Control During High-temperature Summer Periods

After nearly three months of on-site operation, the booster chlorination device performed stably, effectively ensuring continuous compliance of pump room tank outlet residual chlorine under high-temperature summer conditions. The pilot validated the applicability and controllability of sodium hypochlorite generators in secondary water supply scenarios, providing an engineering basis for Suzhou Water Supply Company to further promote this technology in combination with distribution network models and smart scheduling platforms. This practice responds to the industry trend of secondary water supply shifting from "periodic flushing" to "continuous assurance," and provides a replicable technical path for water quality safety in the "last mile" of urban water supply.

Client Testimonial

"Secondary water supply is the 'last mile' of water supply — and also where residual chlorine is most likely to fall short. We used to rely on periodic tank flushing, but during high-temperature summer periods, residual chlorine decays quickly and passive response is very difficult. In 2023, we piloted a smart sodium hypochlorite generator booster chlorination device at the Huilin Plaza pump station. After nearly three months of operation, outlet residual chlorine remained stable and compliant under high-temperature summer conditions, with automatic adjustment, low energy consumption, and minimal limitations. This pilot showed us a feasible path for secondary water supply to shift from 'periodic flushing' to 'continuous assurance,' and accumulated solid operating data for future promotion."

— Project Manager, Water Production Branch, Suzhou Water Supply Company