Naegleria fowleri is a free-living amoeboflagellate inhabiting soil and water that can cause Primary Amoebic Meningoencephalitis (PAM), a rare and sometimes fatal disease. In Australia, the amoeba typically inhabits drinking water supplies that have consistent water temperatures above 20°C. The incidence of PAM is widespread in Australia, with reports from South Australia, Western Australia, New South Wales and Queensland. One of the key issues for water utilities is the potential widespread distribution of N. fowleri and its ability to infect and re-infect drinking water supplies. In Western Australia, the majority of drinking water supplies are operated by the Water Corporation. This paper describes the conditions under which Naegleria spp. have been detected and describes the operational methods employed by the Water Corporation to control and mitigate Naegleria in public drinking water supplies.
Background: Drinking water with an optimum fluoride concentration is a recognized effective method to reduce dental decay. Methods: In this study normal suppliers of drinking water in Western Australia provided map data regarding the distribution of their supplies and the locations of their test points. These data were collated into a single unified map of Western Australian water supplies and fluoride levels. It is clear that the effect of prevention in regionally isolated communities is significant as the cost of providing service is anywhere between 2 and 4 times higher than that in high density regions. Results: The current study found that although a very significant proportion of the population has access to water with fluoride concentrations that would be caries protective, most of these are large urban centre based. Conclusions: Those with high burdens of dental disease are mostly residential in rural and remote areas where water is either not fluoridated, nor regulated, or low in fluoride. However, it is acknowledged that water fluoridation, for many reasons, is not always feasible in rural and remote communities, and preventive efforts through alternative sources of fluoride (e.g. toothpaste) should be considered, even if less effective at community level.
Water utilities have experienced increasing pressure to minimise the formation of disinfection by-products (DBPs), as reflected in the increasingly stringent regulations and guidelines for the concentrations of DBPs in drinking water. Understanding the disinfection characteristics and molecular weight (MW) distribution of natural organic matter (NOM) will assist in the optimisation of drinking water treatment processes to minimise the formation of DBPs. This study investigated the disinfection behaviour of MW fractions of NOM isolated from a Western Australian source water. The NOM was fractionated and separated using preparative size exclusion chromatography (SEC) and the fractions were chlorinated in the presence of bromide ion. The larger MW fractions of NOM were found to produce the highest concentrations of DBPs (trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, and haloaldehydes), with the low MW fractions still producing significant amounts of these DBPs. The results also showed a trend of an increasing proportion of brominated DBPs with decreasing MW and aromatic character. Considering that the smaller MW fractions of NOM produce significant amounts of DBPs, with a higher relative contribution from brominated DBPs, water treatment processes need to be optimised for either bromide removal or the removal of aliphatic, small MW fractions of NOM, in order to meet DBP guidelines and regulations.
The cyanobacterium Microcystis aeruginosa can produce potent toxins known as microcystins. While many studies have focussed on the chlorination of microcystin toxins, little work has been conducted with respect to the chloramination of the microcystins. In addition, no studies have been reported on the effect of chloramination on intact Microcystis cells. This study was conducted to determine the fate of M. aeruginosa cells and microcystin toxins following chloramination of a drinking water source. Results indicate that monochloramine could effectively oxidise dissolved microcystin-LR (MCLR) provided high CT values were employed, typically greater than 30,000 mg min L(-1). The decay of MCLR was demonstrated to be a pseudo first-order reaction with rate constants ranging from 9.3x10(-7) to 1.1x10(-5) s(-1) at pH 8.5. However, in the presence of Microcystis cells, monochloramine was ineffective in oxidising microcystin toxins due to the cells exerting a demand on the oxidant. The doses of monochloramine applied (2.8 and 3.5 mg L(-1)) were shown to rapidly release intracellular microcystins into the dissolved state. Flow cytometric analysis of the cells determined that the lower monochloramine dose did not compromise the cell membrane integrity, even though microcystins were rapidly released from the cells. In contrast the higher monochloramine dose resulted in cell membrane disruption with up to 90% of the cells shown to be non-viable after the high dose was applied.
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