Review of Drinking Water Treatment Coagulants

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report No UWRAA 200

December 1996

SYNOPSIS

This summary presents the findings of a study commissioned by the Water Services Association of Australia and carried out by Gutteridge Haskins & Davey Pty Ltd to review coagulants in drinking water treatment.

REVIEW OF COAGULANTS

It is concluded that:

Ferric chloride, ferric sulphate and PACI can generally offer similar performance to alum.
Promising new coagulants are hydroxylated ferric sulphate and poly ferric chloride. Trials with poly ferric chloride are planned in South Australia.
Organic polymers are generally suitable for water with high turbidity and low colour. They also perform well as a coagulant aid in conjunction with an inorganic coagulant (metal salt), reducing inorganic coagulant dose requirements. Organic polymers are generally not appropriate for highly coloured waters.
Coagulant performance is highly dependent on raw water quality characteristics. Bench and pilot tests are required to evaluate alternative coagulants.

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