Understanding water quality

# 6 What do you know about your water supply?

It could be claimed that water is probably the most important physical resource that we use. We often take its presence for granted in the UK: for most of us it arrives painlessly in our home out of a tap and we can easily dispose of it by pouring or flushing it away. However, how much do you really know about your own water supply and sewage disposal? Are you drinking groundwater or river water? Is it recycled? What is its quality? Where does your sewage go? How much does it cost you? In the next activity you will consider all these questions.

## Activity 7

To answer some of these questions you may need to contact your water supply and sewage disposal company.

1. Do you have a piped water supply? (1% or so of homes in the UK do not.)
2. What is the source of your water? Perhaps there are several sources. (Does it come from a reservoir, a river, groundwater or a combination?)
3. Where is your local water treatment works for water supply and what processes does it use?
4. What is the chemical analysis of your water? Are there any particularly high concentrations, over or near EU limits?
5. Do you have a water meter?
6. What was the cost per person for water supply to your home last year?
7. Is your home connected to sewers, or do you have a septic tank or cesspit?
8. If your home is connected to sewers, where is your local waste water treatment works and what processes take place there?
9. How does the waste water treatment works dispose of the effluent (into which river, lake, or sea) and the sludge (farmland, landfill or incineration)?
10. What was the cost per person for sewage disposal from your home last year?

## Answer

There is obviously no single answer to this question! It will vary depending on where you live. Below I have given the answers for my house (which is in a small village to the south of Milton Keynes) so you can see the type of answer that could be given.

1. Yes, my house has a piped water supply (and life would be very difficult without it).
2. I had to telephone my local water company to check on this: although I thought I knew the answer it proved to be more complicated than I expected. I live on a good sandstone aquifer (the Cretaceous Lower Greensand) and expected my water supply to be just groundwater from local boreholes. However, although part of the supply comes from two local boreholes, this water is linked in a water grid to other parts of my water company region, so my local borehole water is blended with that from two major lowland reservoirs, Rutland Water and Grafham Water, 100 km and 60 km away. I presume this is for security of supply and quality purposes.
3. Again, I had to ask the water company. The borehole water is just filtered and disinfected, but the reservoir water is screened, stored, settled, filtered and disinfected.

4. In England and Wales you can get this information from your water company on request. I was sent an analysis for my water supply which showed it to be within the EU limits (Table 4, Section 4) except for iron, which had a mean concentration of 0.1 mg l-1 and a maximum of 0.42 mg l-1, whereas the EU recommended maximum is 0.2mg l-1.

   The water analysis was for a total of 101 different parameters (many more than in Table 4) and I was also sent the full prescribed concentration list from which I was able to work out that my supply breached regulations additionally for manganese, nitrite, pesticides and phosphorus.

   I found the high iron concentration unsurprising, as the sandstone aquifer supplying most of my water has a high concentration of iron. The high nitrite, phosphorus and pesticide values are in the reservoir water, and could be caused by agricultural runoff.

5. I had a water meter installed in 1992, having calculated that it would save money on water bills to my house, and in the hope that it would also provide encouragement for me to use less water (it has).

6. For 2003 I used a metered 64m3 of water at £1.13 per m3, which cost £1.13 × 64 = £72.32.

7. My house is connected to a sewer.
8. I knew the answer to part of this — that my village has its own small sewage works for primary and secondary treatment — but not the full story. My water company told me that the effluent is discharged to our local small river (the Ouzel) but the sludge is tankered 10 km to the major sewage works in Milton Keynes for further treatment: anaerobic digestion. The digested sludge is then spread on farmland.

9. The cost is £1.86 per m3, taken as 90% of the water supplied (as sewerage is not metered). So

OpenLearn - Understanding water quality
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