Polymers as Alum Replacements in Water Treatment - a Case Study

Aluminium sulphate (alum) is one of the most widely used coagulants in water treatment. Over recent years however, the technology to produce synthetic polymers to compete with alum has been commercially developed to the extent that such polymers may economically replace alum in certain instances. Presented here is a case study which deals with the successful replacement of alum at a major potable water treatment plant. The economic and performance characteristics of the chemicals are compared both in the laboratory and in the plant. One of the important lessons learned was that the standard laboratory test procedure used to select the optimum alum dose was not necessarily appropriate in optimising polymer dose. This finding was also reflected in the plant.