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The source water at Keldgate is derived from a chalk aquifer and is of excellent quality most of the time; however, turbidity and coliform spikes can occur, particularly after heavy rains. Because of tighter regulatory monitoring of cryptosporidium, Yorkshire Water Services needed to treat a number of groundwater sources susceptible to microbial contamination and to select a process route that offered better than four-log removal of cryptosporidia.
Earth Tech was retained by Yorkshire Water Services to complete the detailed process, mechanical, electrical, civil and structural design for this project. Earth Tech was also responsible for construction, mechanical and electrical installation, commissioning and testing of the works.
As a result of pilot trials that indicated membrane technology was an appropriate and cost-effective solution for the Kelgate plant, Earth Tech applied Norit membrane technology for an ultra-filtration membrane plant to provide a barrier against cryptosporidia.
The raw water is abstracted from several boreholes and chlorinated. It then passes through micro-strainers, 80 mm in size and through nine ultra-filtration primary units. Wastewater is treated by a secondary ultra-filtration unit prior to discharge to the treated water storage tank on site.
The design of the Keldgate plant provides an overall water yield in excess of 99.5 percent, which allows the wastewater discharge from the membrane plant to comply with the current site discharge permits.
