Assessment of chloramination control strategy based on free-ammonia concentration

A new approach of using free-ammonia measurements as the basis of a control strategy to optimise a chloraminated water distribution system was tested in a laboratory evaluation. A test rig with a newly developed low level on-line free-ammonia analyser was constructed to investigate two different control configurations, the currently used feedback and the proposed feedforward. The results of this trial showed that only using the free-ammonia analyser for feedback control is not ideal due to its inability to detect chlorine overdosing situations. Better results regarding the maximum yield of disinfectant residuals when using the feedforward configuration were observed, and free-ammonia concentrations below 0.065 mg/L were consistently achieved.