A Storm King® CSO treatment system improved water quality at a culturally important lake in Chaohu, China.

Situation

The Chinese government has identified an urgent need to improve the water quality of its lakes and rivers, and has instigated a number of national strategies designed to clean up the country’s waterways.

Within this national environmental improvement framework, as part of the Chaohu City Urban Water Environment Quality Improvement Research & Demonstration Project, Xi Er lake was identified by the local government as a trial site for a new combined sewer overflow (CSO) treatment strategy.

Problem

In recent years Xi Er lake, in the centre of Chaohu City, Anhui Province, had become extremely polluted, with water quality rated at worse than Grade V—classed as “unfit for human contact”. High levels of surface runoff and agricultural organic pollution had caused eutrophication and silting, turning the waters black and highly odorous.

For the trial to succeed, research engineers needed a high-performing primary treatment solution that could reduce Biochemical Oxygen Demand (BOD), as well as preventing grit, sediment and trash from entering the watercourse during peak storm events.

Solution

The Chaohu Housing & Urban Construction Bureau engaged the Shanghai Urban Construction, Design & Research Institute to design a treatment system for the trial, and the project team identified two candidate technologies.

The team selected the Storm King®, basing their decision on its compact nature, unpowered operation with no moving parts, and the fact that it represented a 50% cost saving over the original budget estimate.

They were also keen to work with a proven technology that was already successfully helping to protect the environment in countries all over the world.

Outcome

Trial data indicated that under storm conditions the Storm King® could reduce BOD by up to 93% and Total Settled Solids (TSS) by up to 87%.

Water quality in the lake has already improved, having been assessed as being no higher than Grade IV.

While protecting the lake from hazardous pollutants, the Storm King® also captures the trash and gross solids that act as an unsightly indication of poor water quality, helping to improve the public aesthetic of the waters.