Results And Discussion

The programme of work at the AWTP includes routine sampling and analysis to optimise performance of each treatment process relative to the feed water quality, regular spiking trials of key risk compounds to ascertain cost effective removal and special projects such as disinfection by-product control.

Figure 2 shows the removal capability of GAC and RO treatments for high levels of key risk compounds actually found to date in River Trent feed water.

Boron being such a small element is unusual in that it is only removed to the same extent by RO as conventional treatment, approximately 50%. This could be important if the current UK limit of 1000fjg/l was reduced to WHO guide level of 300jig/l. To date up to 60% removal has been seen as a result of pH adjustment to 8.5 prior to RO and this will be investigated further together with the effects of reducing pH.

Bromide was detected in River Trent feed water at concentrations between 150 and 540ug/l. It is removed by RO to its limit of detection but has a mean concentration of 280ug/l (maximum 450ug/l) post GAC. Bromide is not included as a regulated parameter within drinking water standards but it plays a significant role in the formation of trihalomethanes and bromate resulting from disinfection with chlorine and ozone treatment respectively.

Nitrate levels in the Trent can at times exceed the 50 mg/1 limit which can not be reduced using the conventional processes currently available at Church Wilne WTW. To

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