First CSO Trial Solution in China tackles Urban River Pollution

Hydro International (UK) has completed its first Combined Sewer Overflow (CSO) installation in China in an important trial to improve urban inland river water quality, funded through a Chinese government special innovation initiative.

As part of China’s National Water Pollution Control and Treatment Science and Technology Project, Hydro International has provided a Storm King advanced hydrodynamic vortex separation system in Chaohu city in the eastern province of Anhui.

Explains Hydro International’s China Business Manager, Charlie Zhong: “After hearing of the Storm King’s sustainable, no-power solution for high-performance pollutant removal, XiaoWangZhuangZhonggou retrofit engineering project research engineers from Shanghai contacted Hydro International. A trial site was identified in Chaohu city to assess the Storm King’s suitability with a view to recommending it as a Combined Sewer Overflow solution that could help solve wider water quality challenges in Anhui and potentially throughout China.”

Doctor Jia of Shanghai Urban Construction Design & Research Institute commented: “At XiaoWangZhuangZhonggou retrofit engineering in Chaohu city, Storm King improves the river water quality by minimising pollutants in combined sewer overflow going into the river.”

The Storm King prevents the highly polluting sediments that are re-suspended in sewer water during peak storm events from being discharged into the XiErChi River, one of the inland rivers in Chaohu City. With a design average flow rate of 200 l/s and a peak flow rate of 300 l/s, it will prevent floatables, grit and sediment carried in the sewer network from entering the watercourse.  

The installation is designed to take out 95% of 200 micron grit and sediment, with average 50% Total Suspended Solids (TSS) removal, achieving average 30% Biological Oxygen Demand (BOD). The retained effluent is diverted back through the sewer network to a nearby wastewater treatment works for processing.

Zhong continues: “A major advantage of the Storm King is that it is activated automatically by the rising flow of water during heavy rainfall periods. It does not need power and has no moving parts, so requires minimal maintenance.

“The system can deliver primary treatment pollutant removal levels, a high performance which only the Storm King is capable of achieving. Conventional CSO screening solutions would not be capable of these standards.”

Unusually, the Chaohu Storm King has been constructed in a raised position, so that it can be viewed in a public area to encourage community engagement in water quality improvements. 

The Storm King installation was designed by Shanghai Urban Construction Design & Research Institute and supplied via Inter Flow Control Technology of Tianjin, an appointed distributor of Hydro International equipment in China. The Storm King was manufactured by Hydro International at its UK-based fabrication centre in Cambridgeshire.

The National Water Pollution Control and Treatment Science and Technology Project, known as “water special”, is one of 16 major science and technology initiatives identified to make breakthrough progress in China over the next 15 years. Water projects cover six major themes incorporating lakes, rivers, urban water environment and drinking water. Anhui Province is one of the demonstration areas selected for the water projects, which cover improvements to river basin water pollution control, lake eutrophication control and water environment ecological restoration.

By protecting the watercourse, the project supports the ongoing success of water quality improvements at Chao Lake, one of China’s five largest fresh-water lakes and a popular tourist destination. Although in past decades high levels of surface runoff and agricultural organic pollution caused eutrophication and silting in Chao Lake, recent treatment work has significantly improved its water quality.