The perils of safe drinking water

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River draining catchment and feeding reservoir at Alwen Reservoir, North Wales

I’m sure one of the last things to run through your mind when pouring a glass of water, taking a shower or filling your very middle-class espresso machine for your morning cup of ‘Joe’, is that the water coming out of your tap can be potentially lethal. Well, over this past academic year, I have been discovering the processes of cleaning and disinfecting water for human consumption, and the health risks associated with it. The whole process, from catchment to reservoir and beyond, is very sleep inducing for many ecologists (as I have discovered at various presentations), but I will attempt to briefly explain the process and then the potential dangers.

Natural organic matter (hereby referred to as NOM) is present in all ground, surface and soil waters. It contains humic and fulvic materials, amino acids, carbon and nitrogen (to name but a few constituents). When dissolved in water, it is referred to as dissolved organic matter (DOM). Originating in the catchment, this DOM will find its way to the nearest stream draining the catchment, and will ultimately end up in the ocean, despite various interceptions from lake/reservoirs etc. DOM creates an amber brown colour in water, and leaves a nasty taste and aroma, and can stain clothing/ceramic sink basins/baths/toilets, therefore, removing this DOM before water is consumed by humans is of a high importance to water companies.

Removal takes place at the water treatment works, where aluminium sulphate is commonly added to a tank of water, to alter the polarity of the DOM from negative to positive. This causes the DOM compounds to bind to each other, before being brought to the surface of the tank by dissolved air flotation, and removed. However, this process is never 100% successful at removing the DOM, and some remains in the water when it moves on to the disinfectant stage.

Common disinfectants used are chlorine and its compounds, which are favoured for their low prices and their high disinfection qualities. However, when mixed with the carbon and nitrogen in the DOM that may be remaining in the water, the chlorine creates disinfection by-products, which are dangerous. Recent research has shown that these disinfection by-products (DBPs) (formed from carbon), and nitrogenous-disinfection by-products (n-DBPs) have been linked to cancer (especially in the colon and bladder) and cell mutations, still births, and respiratory illnesses. Research shows that consuming 1 litre of water is equivalent to the exposure from a 5 minute shower or a 15 minute bath, where the DBPs can be adsorbed dermally or through vapour. Over 700 DBPs and n-DBPs have been discovered to date.

Sounds worrying, huh?
Well, you can partially rest assured that the World Health Organisation (WHO, 2006), has limited some of the compounds contained under one major group of DBPs, trihalomethanes, (Chloroform, Bromodichloromethane, Dibromochloromethane and Bromoform) to a maximum concentration of 100 µg L-1 at the UK consumers tap. However, more and more dangerous compounds are being discovered each and every year, and more research into their potential effects will throw up more and more worrying statistics.

So, what can you do to protect yourselves? Well, nothing, to be brutally honest. However, if your water smells strongly of chlorine, water companies recommend pouring a jug of it and leaving it in the fridge, where the smell will dissipate. Stand alone water filters could provide a small amount of additional protection, but aside from that, not a lot else can be done by the consumer, or, currently, by the provider. So, another item to add to the list of cancer causing every-day items that the Daily Mail keeps publishing, those scare mongering b**tards!

Now for the extra exciting part: Work I’m doing here at the university is looking at the character of the dissolved organic carbon and nitrogen in 3 contrasting reservoirs for drinking water purposes in North Wales, and looking to see if there is a link between catchment properties (such as vegetation cover, soil type, bedrock, management practices) and the DOM in the streams draining the catchment, to provide information to the local water body to aid in the reduction of NOM in their drinking water, ultimately reducing the formation of DBPs. As a side project, I have also discovered a previously unpublished method of characterising dissolved organic nitrogen with promising results so far. This should lead to further understanding of what aspect of the catchment affects the release of nitrogen, and ultimately, should lead to the reduction of nitrogen concentrations in pre-treatment water.

Further reading

http://kill-or-cure.herokuapp.com for a list of Daily Mail cancer causes and preventions

http://srufaculty.sru.edu/Michael.stapleton/Class/Geochemistry/Papers/103leenheer.pdf for more info on NOM/DOM

www.jstor.org/stable/20485866 for risk of stillbirth from drinking water

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Posted on May 10, 2013, in Uncategorized and tagged , , , , , , , , , . Bookmark the permalink. Leave a comment.

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