Automatic Coagulation Control at Water-Treatment Plants in the North-West Region of England |
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Authors: | R F CRITCHLEY BSc MA E O SMITH P PETTIT LRSC |
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Affiliation: | Senior Research Officer, Chief Scientist's Dept., North West Water Ltd.;Senior Technician, North Lakes Water Supply District. North West Water Ltd.;Process Chemist, Peak Water Supply District, North West Water Ltd. |
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Abstract: | North West Water has evaluated several automatic coagulation control systems covering a range of raw waters and treatment facilities. The experiences have shown that streaming-current type systems are effective in controlling coagulant dose automatically, provided that appropriate plant conditions exist. In particular, rapid fluctuations in flow or poor mixing of chemicals can lead to unstable signals. Recent investigations indicate that for some waters streaming-current voltage is sensitive to small changes in pH, and precise control of pH is therefore necessary. The main observed benefits have been treated water of a more consistent high quality, together with improved security of service, as the systems will respond reliably and effectively over long periods. Significant savings in coagulant usage can be obtained in certain cases. |
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Keywords: | Automatic coagulation control water treatment streaming current microprocessor systems feed-forward control feedback control coagulant dose floc size |
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