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New £3.8 million potable water plant opens in North Wales
casestudy
New £3.8 million potable water plant opens in North Wales Residents of the picturesque area situated to the west of Wrexham, in North Wales, UK, will soon benefit from an improved water supply from their local water utility, Dee Valley Water Plc. A new 4Mld (million litres a day) potable water treatment plant has just been completed at Llandegla in the area to simultaneously treat the water from three reservoir sources and meet the latest EU requirements for manganese removal. he new plant, which replaces an existing single stage filtration works on the site, has been designed by Biwater Treatment Ltd, who are responsible for the turnkey construction, installation, testing and
T
commissioning of the new facility, which is now fully operational. The company selected all the filtration systems at the site and installed a number of Rotork actuators to control the valves and consequently the flow of water throughout the plant. The new plant treats raw water from Pendinas reservoir, Nant-y-Ffrith reservoir, and Llyn Cyfynwy reservoir. The plant has just passed a 28-day performance trial and will maximise the available local water resources. It will produce drinking water to the 2001 water supply regulations, in accordance with the UK and EU water quality laws.
Treatment process
One of Biwater Treatment Ltd’s engineers’ commissions a Rotork filter valve actuator at the recently completed Llandegla potable water treatment plant in North Wales, UK. The new £3.8 million plant treats water from three nearby reservoirs and utilises flash mixing and flocculation, pH control with lime, coagulation with aluminium sulphate, first-stage rapid gravity sand filtration systems, and second-stage manganese removal pressure filters. 30 December 2004
The water treatment process consists of blending the three raw water sources from the reservoirs, followed by flash mixing and flocculation, pH control with lime, coagulation with aluminium sulphate, Dissolved Air Flotation, first-stage rapid gravity filtration, Intermediate pumping, second- stage manganese removal in pressure filters, and gas chlorination. The treated water is pumped to an existing service reservoir. The backwash water is processed through WRc thickeners and the supernatant returned to the inlet works. Sludge is stored in a holding tank and periodically tankered off-site. The works is controlled by an intelligent MCC controller using a touch screen SCADA system. Clarified water flows into the common filter inlet channel and is split between four first-stage filters installed to remove solids. Each filter measures 2 m x 4 m and is of a reinforced concrete construction. The filters contain a layer of 14/25 sand media on top of a layer of 8/16 sand. The maximum filter loading rate is 7.8 m/h. The monolithic filter floor is fitted with 36 Cadar nozzles per square meter through which the clean water flows. The solids deposited in the sand filter media can be removed from the bed ISSN 0015-1882/04 © 2004 Elsevier Ltd. All rights reserved
casestudy by regular backwashing initiated by high turbidity in the filtrate on a fixed time sequence, by a high differential head across the filter, or by operator intervention at the relevant MCC or HMI system. It is anticipated that each filter will require washing after a minimum period of 24 hours of operation. The full backwash sequence consists of a short air scour followed by a separate water wash. The air scour is used to agitate the bed and dislodge solids attached to the filter media. The separate water wash is then used to remove the dislodged solids from the media. The first-stage filtered water is pumped from the intermediate pumping station into the common header pipework. Here the flow is split between three 2.75 m diameter manganese removal pressure filters. The single media filter beds comprise of a 1010 mm deep layer of 16/30 sand with 20% manganese dioxide media. The maximum filter loading rate on this second filtration stage is 15 m/h. The anticipated filter run time to remove all the manganese is 72 hours.
Project timescale All the above filtration and separation systems were selected, installed and commissioned by the principle contractors, Biwater Treatment Ltd who ordered equipment from various different manufacturers. The company designed the solution based upon raw water data supplied by Dee Valley Water Plc, the owners and operators of the site, and by examining best practice within the water treatment industry. Work started on the site on 12th June 2003. The construction of the concrete sand filter tanks was completed by October of that year and the steel second-stage pressure filters were craned into position in November so that the portal frame building could be erected. The mechanical and electrical installation for the water treatment plant, including Rotork’s actuators, was completed by April 2004. This was followed by a period of dry and wet testing undertaken as part of the process commissioning stage. The plant went into initial operation on 12 August 2004. The performance trial, during September, was the final hurdle the facility faced before full-scale operations could begin. With its successful completion, the £3.8 million plant has now been handed-over to the end user who will provide consumers in the area with a reliable, quality water supply for years to come.
Control Two IQM modulating actuators from Rotork regulate the inlet supply control valves at the Filtration+Separation
Engineer’s from Biwater Treatment Ltd check an on-screen display during the commissioning procedure at the new Llandegla potable water treatment facility in North Wales, UK, which is owned and operated by the local water utility, Dee Valley Water Plc. Welsh facility. Each of the four first-stage filters is equipped with five IQT actuators to control inlet, outlet and the daily backwash and air scour operations. A similar IQT actuated valve configuration operates the three secondary pressure filters for manganese removal. Alarms from the normally unmanned site will be signalled by telemetry to the Dee Valley Water operations centre at nearby Packsaddle in Wales. The plant is also equipped with an emergency generator to keep it running during a power failure, supported by a battery back-up to ensure failsafe operation of the key valve actuators. This will allow for continued operation during times of emergency while still enabling the end users to keep the running costs of the plant low.
Contact Biwater Treatment Ltd, Gregge Street, Heywood, Lancashire, OL10 2DX, UK. Tel: +44 1706 367 555 Fax: +44 1706 365 598 Website: www.biwater.co.uk Rotork Controls Ltd Brassmill Lane, Bath, BA1 3JQ, UK. Tel: +44 1225 733 200 Fax: +44 1225 333 467 Website: www.rotork.com December 2004 31
New £3.8 million potable water plant opens in North Wales Residents of the picturesque area situated to the west of Wrexham, in North Wales, UK, will soon benefit from an improved water supply from their local water utility, Dee Valley Water Plc. A new 4Mld (million litres a day) potable water treatment plant has just been completed at Llandegla in the area to simultaneously treat the water from three reservoir sources and meet the latest EU requirements for manganese removal. he new plant, which replaces an existing single stage filtration works on the site, has been designed by Biwater Treatment Ltd, who are responsible for the turnkey construction, installation, testing and
T
commissioning of the new facility, which is now fully operational. The company selected all the filtration systems at the site and installed a number of Rotork actuators to control the valves and consequently the flow of water throughout the plant. The new plant treats raw water from Pendinas reservoir, Nant-y-Ffrith reservoir, and Llyn Cyfynwy reservoir. The plant has just passed a 28-day performance trial and will maximise the available local water resources. It will produce drinking water to the 2001 water supply regulations, in accordance with the UK and EU water quality laws.
Treatment process
One of Biwater Treatment Ltd’s engineers’ commissions a Rotork filter valve actuator at the recently completed Llandegla potable water treatment plant in North Wales, UK. The new £3.8 million plant treats water from three nearby reservoirs and utilises flash mixing and flocculation, pH control with lime, coagulation with aluminium sulphate, first-stage rapid gravity sand filtration systems, and second-stage manganese removal pressure filters. 30 December 2004
The water treatment process consists of blending the three raw water sources from the reservoirs, followed by flash mixing and flocculation, pH control with lime, coagulation with aluminium sulphate, Dissolved Air Flotation, first-stage rapid gravity filtration, Intermediate pumping, second- stage manganese removal in pressure filters, and gas chlorination. The treated water is pumped to an existing service reservoir. The backwash water is processed through WRc thickeners and the supernatant returned to the inlet works. Sludge is stored in a holding tank and periodically tankered off-site. The works is controlled by an intelligent MCC controller using a touch screen SCADA system. Clarified water flows into the common filter inlet channel and is split between four first-stage filters installed to remove solids. Each filter measures 2 m x 4 m and is of a reinforced concrete construction. The filters contain a layer of 14/25 sand media on top of a layer of 8/16 sand. The maximum filter loading rate is 7.8 m/h. The monolithic filter floor is fitted with 36 Cadar nozzles per square meter through which the clean water flows. The solids deposited in the sand filter media can be removed from the bed ISSN 0015-1882/04 © 2004 Elsevier Ltd. All rights reserved
casestudy by regular backwashing initiated by high turbidity in the filtrate on a fixed time sequence, by a high differential head across the filter, or by operator intervention at the relevant MCC or HMI system. It is anticipated that each filter will require washing after a minimum period of 24 hours of operation. The full backwash sequence consists of a short air scour followed by a separate water wash. The air scour is used to agitate the bed and dislodge solids attached to the filter media. The separate water wash is then used to remove the dislodged solids from the media. The first-stage filtered water is pumped from the intermediate pumping station into the common header pipework. Here the flow is split between three 2.75 m diameter manganese removal pressure filters. The single media filter beds comprise of a 1010 mm deep layer of 16/30 sand with 20% manganese dioxide media. The maximum filter loading rate on this second filtration stage is 15 m/h. The anticipated filter run time to remove all the manganese is 72 hours.
Project timescale All the above filtration and separation systems were selected, installed and commissioned by the principle contractors, Biwater Treatment Ltd who ordered equipment from various different manufacturers. The company designed the solution based upon raw water data supplied by Dee Valley Water Plc, the owners and operators of the site, and by examining best practice within the water treatment industry. Work started on the site on 12th June 2003. The construction of the concrete sand filter tanks was completed by October of that year and the steel second-stage pressure filters were craned into position in November so that the portal frame building could be erected. The mechanical and electrical installation for the water treatment plant, including Rotork’s actuators, was completed by April 2004. This was followed by a period of dry and wet testing undertaken as part of the process commissioning stage. The plant went into initial operation on 12 August 2004. The performance trial, during September, was the final hurdle the facility faced before full-scale operations could begin. With its successful completion, the £3.8 million plant has now been handed-over to the end user who will provide consumers in the area with a reliable, quality water supply for years to come.
Control Two IQM modulating actuators from Rotork regulate the inlet supply control valves at the Filtration+Separation
Engineer’s from Biwater Treatment Ltd check an on-screen display during the commissioning procedure at the new Llandegla potable water treatment facility in North Wales, UK, which is owned and operated by the local water utility, Dee Valley Water Plc. Welsh facility. Each of the four first-stage filters is equipped with five IQT actuators to control inlet, outlet and the daily backwash and air scour operations. A similar IQT actuated valve configuration operates the three secondary pressure filters for manganese removal. Alarms from the normally unmanned site will be signalled by telemetry to the Dee Valley Water operations centre at nearby Packsaddle in Wales. The plant is also equipped with an emergency generator to keep it running during a power failure, supported by a battery back-up to ensure failsafe operation of the key valve actuators. This will allow for continued operation during times of emergency while still enabling the end users to keep the running costs of the plant low.
Contact Biwater Treatment Ltd, Gregge Street, Heywood, Lancashire, OL10 2DX, UK. Tel: +44 1706 367 555 Fax: +44 1706 365 598 Website: www.biwater.co.uk Rotork Controls Ltd Brassmill Lane, Bath, BA1 3JQ, UK. Tel: +44 1225 733 200 Fax: +44 1225 333 467 Website: www.rotork.com December 2004 31