The quality of water is not strained enough

The quality of mercy is not strained.
It droppeth as the gentle rain from heaven,
Upon the place beneath.
It is twice blessed.

Portia's speech from MoV

It is one of the ironies of the situation is that Ireland is awash with water: at least a meter of rain falls each year and the landscape is chock full of picturesque lakes and rivers, but Greater Dublin is currently having to restrict water supply.  I have just spent the last two weeks talking about drinking water DW supply with my 4th Year Environmental Chemists.  I've been saying how fascinating the process of DW processing is and how when Irish Water gets launched as a commercial venture there will be loads of really interesting, scientifically challenging jobs for my boys and girls.  Despite my enthusiasm, I only half believed that I was bringing them along with me, because, like everyone else, we take sparkling clean drinkable water coming out of the kitchen tap for granted.  We need ad lib drinkable, lightly chlorinated water so that we can wash our cars and flush our toilets with it, as well.

At the start of the week, problems of supply started to impact on the distribution of water to our capital city.  Red faces all round because Dublin is hosting 10,000 affluent geeks at the 2013 International Web Summit and restauranteurs are not sure if they will be able to wash dishes and boil pasta for their guests tonight.  "Problems of supply" stayed curiously undefined for a couple of days as international experts were being flown in to consult.  Paranoid me wondered if a UFO had seeded the reservoir with alien life-forms.  Scientific teacher me was all agog to get information to see which of the many and complex processes irequired to treat water had broken down and why.  Listening to pundits on the wireless recently has given me this much glimmer. 

We had a long dry summer over much of Ireland in 2013.  Under these circumstances the peat with covers much of our upland watersheds dies out, gets oxidised and breaks down into very fine unfilterable organic particles.  Over the last couple of weeks, we've had the tail end of a couple of hurricanes come across the Atlantic and dump rain on those uplands.  That has washed the discoloured water into the reservoirs which service Dublin's water supply.  So far, so what you may ask a little colour in the water never did my granny any harm.  But the suppliers of water are justifiably worried about microbial contamination of water. Niether they nor we want fecal or other coliforms coming out of anyone's kitchen tap, let alone cholera.  So part of the process is to chlorinate the water.  This kills all the bacterial pathogens (although it works not so well with Cryptosporidium) BUT it also reacts with unfilterable organic colour to form TriHaloMethanes THMs.  Trichloromethane is aka chloroform which is okay in small doses but all chlorine products are contaminated with bromine which has very similar chemical properties and so is difficult to separate out for a finite amount of money. TBM = bromoform is a known animal carcinogen and although, on the scale of things there are worse things to drink, no water supplier wants to have that coming out of the taps of their customers.  So they are moving experts and heaven and earth to deal with this problem.  That is expensive, but we don't want

Water, water, every where, 

And all the boards did shrink; 

Water, water, every where, 

Nor any drop to drink.

Coleridge The Rime of the Ancient Mariner