SES Water partners with Evoqua for gas disinfection solution


SES Water supplies 160 million litres of clean water daily to over 735,000 people in the UK across parts of Surrey, Kent West Sussex and South London. Westwood Water Treatment Works in Surrey is central to keeping its supply of water safe for local residents.



SES Water needed to find a new cost-effective gas disinfection system that met its requirements for whole life costs, high safety, and operational efficiency, while delivering optimum water quality. Space was also a key consideration for the water treatment works, as the new system had to fit into the same footprint as its predecessor.



SES Water turned to Evoqua Water Technologies and following a site survey and extensive evaluation of all disinfection solutions available, it was identified that a full gas system replacement was the answer.

Evoqua installed its V10k™ chlorinator system, which was central to the new solution. This included a vacuum regulator mounted at the gas supply, a wall-mounted gas control unit which indicates feed rate and a water operated injector that provides the vacuum source to drive the entire system. It is a highly efficient system, with a flexible design for dosing up to 10 kg/hr.

Alongside this, the Evoqua S10k™ vacuum regulator and CCU (chemical changeover unit) was selected as the gas feeder unit to perform changeover of the cylinder banks. It is vacuum operated and positive shutoff allows the gas containers to be changed without admitting air, dirt or moisture into the control unit.

To provide consistent and accurate water quality monitoring, the DEPOLOX® 5 measurement module was installed. Importantly for SES Water it provides high response times of under 20 seconds to meet fluctuating disinfection demands, giving the team confidence they can guarantee water quality for customers. Furthermore, the DEPOLOX® 5 minimises chemical overdosing, which will optimise operating costs.

During collaboration over the design of the system, SES Water identified that it also wanted to improve the performance of the chlorine manifold header. Evoqua developed a bespoke solution for the Westwood site that incorporated break off points, so the gas cylinders could be cut off and maintained, without the need to shut the full cylinder bank down.





The new gas disinfection system has delivered against all of SES Water's objectives, including quality of technology, a low footprint, cost-effectiveness, safety levels and operational efficiency. The project demonstrates the importance of close collaboration between the client and project team to find the right solution. 

" Replacing the gas disinfection system was vital so we could deliver the best water quality for our customers but, alongside this, improve safety on site and increase the efficiency of our treatment works. Like many works, with cost and space constraints to work around, it was critical we got the right disinfection solution. By working closely with Evoqua, we were able to evaluate all technology options on the market and have confidence the gas system we selected was the right one. "

Steve Burgess, Water Treatment Manager, SES Water