Over 14-weeks during the Queensland summer (2019/2020), the chloraminated network received an elevated total chlorine residual (4.0 mg/L) as part of a trial to determine if this increased residual had any impact on improved disinfection residuals and reduced microbial detections in the Bulk and Water Supply Partners (Urban Utilities, Unitywater and Logan City Council) reticulated networks. Increased chloramine dosing was observed to improve the total chlorine residual in most of Seqwater’s bulk water network, however, it did not improve the secondary disinfection performance in areas known to have high water age due to network configuration. Observed and modelled information from the 2019/2020 summer trial demonstrated that some water quality indicators slightly improved, compared to the 2018/2019 summer. The primary objective of the trial was to increase the area of the network that held total chlorine residual >0.5 mg/L. The trial achieved this improvement for three reticulated zones in the Urban Utilities’ network, all of which were adjacent to Seqwater’s bulk water supply points. Network mode of operation was also critical. The increased chloramine dosing program resulted in an increased number of South East Queensland water customers receiving improved secondary disinfection residuals and associated public health benefits at their meter.
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