In an effort to provide a reliable and adequate supply of potable water to the customers of the Water Supplies Department (WSD) in Tai Po, Hong Kong, Tai Po Water Treatment Works (TPWTW) increased its capacity of supplied potable water from 73,381 gpm to 146,762 gpm.
To make the expansion feasible, a solution was created for the procurement of disinfection chemicals: sodium hypochlorite and chlorine gas. It was also required that excess sodium hypochlorite be produced for transport to nearby facilities.
In 2017, Electrolytic Technologies Systems (ETS) was awarded a contract to supply on-site chlorine generation (OSCG) systems for the TPWTW. Klorigen, the technology employed, is designed for municipal applications in both water and wastewater treatment and has been implemented at plants globally since 2001.
“The project presents many challenges and excitement to WSD and the project team,” said Samson Chan, senior engineer in the consultants management division of the Water Supplies Department. “While the technology is proven and common for industrial applications, it is a relatively unique application for municipal water treatment works and new to Hong Kong. The complexity and sophistication of OSCG is significantly above and beyond the typical water treatment technologies.”
The primary reason for changing from pressurized chlorine gas to on-site generation of chlorine gas was safety. The logistical and safety concerns associated with the storage of chlorine gas cylinders as well as the decision to maintain chlorine gas as the primary disinfectant meant that an on-site chlorine generation solution was needed. The Tai Po WSD decided to implement territorial-wide OSCG at the water treatment works.
Ultimately, the solution was Electrolytic Technologies Systemsʼ Klorigen, which uses salt, water and power, to generate chlorine gas, caustic soda and sodium hypochlorite.
In order to meet the facilityʼs chemical demand, it was determined that the equipment installation should be able to produce approximately 7,495 ppd of chlorine. The equipment uses a modular, skid-mounted design and can be configured to accommodate the existing facility layout, which aided in sizing the equipment appropriately for the application.
Before the start-up of the on-site generation system at Tai Po Water Treatment Works, the previously used pressurized chlorine gas installation had to be decommissioned and stored cylinders had to be removed. This process required an interim chemical procurement solution to allow for uninterrupted supply.
Nearby, a facility already utilizing the Klorigen technology supplied sodium hypochlorite to be transported to TPWTW, pending the commissioning and full operation of the new system installation at the Tai Po facility.
“One of the exciting aspects of this project was that we were able to rely on the existing Klorigen OSCG units at Ngau Tam Mei Water Treatment Works to supply sodium hypochlorite for disinfection during the installation period,” said Derek Lubie, ETS CEO.
Since Tai Po is the third Klorigen OSG installation in Hong Kong under the same ownership, ETS has already experienced the design, manufacturing, installation and commissioning process with the previous plants. This experience allowed the team to have a clear understanding of the client’s requirements and expectations for the Tai Po WTW project.
For Lubie, what was truly an unexpected aspect of the project was the onset of COVID-19, which impacted the initial startup phase. The project began in January 2020 and concluded in July.