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Title: Ferric dosing of Grafham Water : a review of its impact on benthic invertebrates 1990-1993
Author: National Rivers Authority Anglian Region
Document Type: Monograph
Following the Incidence of severe blooms of blue-green algae in 1989 and 1990 a major phosphate reduction programme was initiated by Anglian Water Services. Between June 1990 and August 1992 ferric sulphate dosing of Grafham Water was carried out by Anglian Water Services as part of a strategy to lower phosphate levels and thereby reduce the incidence of blue-green algal blooms. In 1990 dosing was carried out by a combination of methods - discharge from the draw-off (valve) tower, discharge from the aeration (inlet) tower, and from a barge. In 1991 dosing was almost entirely from the aeration (Inlet) tower and in 1992 dosing took place only from this source. The ferric sulphate was discharged as an 11% solution as iron and between June 1990 and August 1992 substantial quantities were used. Up to 1,000 tonnes of ferric sulphate entered the reservoir weekly during 1991 and between May and August 1992 over 800 tonnes were discharged each week. By the end of August 1992 a total of 30,619 tonnes of ferric sulphate had been added to the reservoir. Since August 1992 no dosing has been reported by Anglian Water Services. The National Rivers Authority carried out biological monitoring of Grafham Water over this period and for a year after to assess the effect of the dosing programme on the benthic invertebrate communities of the reservoir. Reports were produced for the years 1990, 1991 and 1992. This report describes the results of benthic invertebrate monitoring and sediment iron analyses carried out in 1993 and reviews previous work.
Publisher: National Rivers Authority
Publication Date: 1993
Publication Place: [Peterborough]
Subject Keywords: LakesEutrophicationPollution controlPhosphatesIronAlgal bloomsBiological monitoringInvertebrates
Geographic Keywords: EA AnglianGrafham WaterCambridgeshire
Extent: n.p. [105]
Total file downloads: 292

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