London's Water

[Morning Sun]

Is the water in London's water reservoir (the one beneth Heathrows flight path) cleaned and ready for drinking? if its not, what is the cleaning process the water goes though before it reaches our taps? thnxs

[derbyram]

why? what are you intending to do to the water supply?? Should I be contacting my mole in MI5?

[Morning Sun]

haha..come off it... i posted the question as it seems to me, rather illogical to situate most of londons drinking water in an area that is the most polluted. it is directly beneath just about every flight leaving heathrow (and take off is when aeroplanes consume and release the most fuel). heathrow is also one of the worlds busiest airports. my post was intended to question the safety of my water.considering your answer was somewhat light hearted, i do not feel the need to justify my question further. besides which you have added another dimension.. should we not be protecting our water supplies better then having a few grazing sheep on the reservoirs banks, (though they have obviously done a good job as of yet)

[trilobite]

The reservoir near Heathrow you mention is merely one of hundreds of reservoirs supplying water for London and the South East - so it is not "London's water reservoir"

Explanation coming up!! (Don't know max size per post!)

[trilobite]

2.

Two of the main suppliers of water to London and other parts of the region are; Thames Water and Three Valleys Water who between them control over 500 reservoirs.

There are two main procedures before water flows out of your tap - abstraction and treatment.
Abstraction means "collecting the water" from rivers, reservoirs, or from boreholes and aquifers.
Three Valleys Water (3VW) abstract 42% of from rivers/reservoirs and 58% from boreholes and aquifers, whilst Thames Water (TW) abstract 75% from r/r and 25% from bh/aq.
The reservoir at Heathrow is a STORAGE reservoir. This type of reservoir contains UNTREATED water - it's 'clean' but not suitable for drinking. Storage reservoirs include those created by damming a river valley where rivers and streams feed into them, aswell as those that serve as a receptacle for water pumped from nearby rivers.

[trilobite]

3.

Treatment of the water involves filtration, solute removal and disinfection.
Filtration is removal of solid suspended particles (clay, sand, micro-organisms, vegetation etc.) that make the water turbid (cloudy). Allowing water to stand in reservoirs already helps this process by allowing larger particles to sink to the bottom.
At the Treatment Plant, water passes through sand bed filters (of increasingly fine grades) to remove any remaining solid particles. Layers of Activated Charcoal within the sand help to remove dissolved impurities (Think of "Odour-Eaters in your trainers that contain activated charcoal - it's a similar thing!) Water abstracted from aquifers will need less filtration than river water for example, as it contains less suspended particles.
Finally, a 'disinfectant' (usually chlorine) is added to the now clean and clear water to kill any remaining bacteria. This water can now be pumped through the mains system to your tap, though most is pumped to SERVICE reservoirs for storage.

Service reservoirs contain clean, drinkable, treated water; are covered; and usually located on high ground to help maintain water pressure in the main by gravity.

[trilobite]

4.

So, for any given reservoir, if you can SEE the water, it is likely that;
- It contains untreated water
- It is only one of literally hundreds supplying a given area.
Also, that the treatment process is remarkably effective in removing pollutants - including aviation fuel and emissions from aircraft engines!!

Finally, it's worth bearing in mind that 3VW supply some 876 million litres of treated water per DAY through 13,500 Km of mains whilst TW supply 2,750 million litres per day and have over 31,600 Km of mains.
Why do we get on our high horses when occasionally a water main bursts?

Oh, I'd like to point out that I have absolutely nothing to do with the above companies or the water supply business whatsoever!

Phew!! (draws breath)

[Morning Sun]

thanks very much trilobite. good answer. you have educated an uneducated concern