The Juas Water Treatment Work's recommissioning project is now complete, with the water treatment works successfully passing its test phase.
This project has been carried out by in-house Guernsey Water Staff, the refurbishment forms part of Guernsey Water's Water Treatment Strategy, revised in 2017 following a comprehensive review of the island's existing and future provisions. The strategy aims to save £10 million of expenditure over 25 years.
You can view the works, the water treatment process, and the refurbishment by using the infographic and refurbishment link below, the site history can be viewed below.
Click on the features to learn more!
This is where all the water treatment chemicals are stored and prepared for dosing. We also produce Sodium Hypochlorite here, a disinfectant which is added as a final dose to the filtered water, ensuring acceptable water quality is maintained as water travels though the distribution network to customers' homes.
The water treatment works is controlled remotely from our HQ at Brickfield House. However the water treatment works can also be operated from the control room on site. The control room is also home to many instruments that measure and report the quality of the water in real time to our operators.
Juas water treatment works is home to Guernsey Water's third largest storage reservoir, a combination of three quarries, Queens, Juas and Hougue Juas. These reservoirs join when the water level is above 11 metres. Storage is important & helps reduce nitrate and bacteria levels in the water naturally prior to treatment. Water is pumped from these quarries into the clarifier tanks where the treatment process begins.
The first treatment stage involves the removal of dirt aided by the addition of a small volume of two chemicals, a flocculant and clarifier aid, these allow for efficient settling of solids (bacteria / viruses / dirt) from the water in the clarifier. The 'clarified' water then flows to the filter house for additional treatment. The clarified solids and chemical dose are decanted from the clarifier periodically and pumped to waste via our sewer network.
Water flows from the clarifier to one of three rapid gravity sand filters, these dual media filters (sand / anthracite) further remove suspended particles. The water exits the bottom of each filter and flows into the clear water tank. Periodic washing of the sand filters takes place to clean them, the water from this process is recycled back to the reservoir following solids removal in the wash-water recovery tanks.
Particles captured in the filter beds are periodically washed out, this washwater, containing the particles, is then gravity fed into three of the site's washwater tanks, where the sediment settles out to form a layer of sludge. The sludge is then pumped into the sewer network and the remaining water returned to the quarry for future use.
Home to the pumps which feed treated water into our distribution network. Clean water from the filter beds flows to the high lift house where it is treated with ultraviolet light for disinfection and a final dose of chlorine. This ensures wholesome water quality is maintained as it travels through the distribution network to customers' homes. Water samples are taken on a regular basis at this point.
These treated water storage tanks provide a simple way to control constant pressures within the distribution network during fluctuating water demands during the day and also provide a short-term supply facility in times of emergency breakdown of pumps or other treatment equipment.
Powdered carbon can be added to the water feed before reaching the clarifier tank to improve the taste of the water during spring and summer algal bloom activity. Algal blooms can impart odd tastes to the water supply on occasion. The powdered carbon is then removed in the next stage of treatment - clarification.
Random samples are taken from our customers' homes throughout the year to ensure that water quality meets our standards. 1236 individual tests were conducted in 2017.
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