Umgeni Water, the bulk treatment authority for the cities of Durban and Pietermaritzburg changed from inorganic coagulants to synthetic polymeric coagulants at its various works in the mid 1980s. The advantages and disadvantages experienced with the new chemicals are discussed in detail in the paper and the changes to test procedures necessary are highlighted. The polymeric coagulants were found to produce good quality water in line with international norms but their unsuitability for enhanced coagulation may preclude their use on some of the works where organic enrichment is becoming a problem.

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