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The Use of Redox Potential to Control Ferric Sulphate Dosing during Phosphate Removal
Author(s) -
KERRISON P. H.,
McEWEN B.,
PHILLIPS G. L.,
CROOK B. V.
Publication year - 1989
Publication title -
water and environment journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 37
eISSN - 1747-6593
pISSN - 1747-6585
DOI - 10.1111/j.1747-6593.1989.tb01545.x
Subject(s) - effluent , phosphate , environmental science , sewage , phosphorus , environmental chemistry , redox , ferric , chemistry , sewage treatment , environmental engineering , inorganic chemistry , organic chemistry
In recent years, the Norfolk Broads have been enriched with sewage effluent and runoff from heavily fertilized land. Nitrogen and phosphorus compounds from these sources can cause ecological problems by stimulating increase in algal biomass in the water, so part of Anglian Water's programme of research in Broadland has been to remove phosphate from major sewage effluents discharged to the Rivers Ant and Bure. This is achieved by dosing ferric sulphate to secondary effluent and settling the resultant insoluble complex. At three sites on the River Bure, the performance of timeclock‐ and redox‐based dose control systems was evaluated. Redox control, by restricting dosing when phosphate load was low, increased the efficiency of phosphate removal and produced up to 19 per cent savings in chemical costs. Modifications are described which made the system self‐regulating and ensured that savings were not eroded by maintenance costs. The system now operates efficiently and routinely at major sites on the Rivers Ant and Bure.