ABSTRACT
If a private water supply is found to contain pathogens or the indicators of such contamination, the first consideration should be whether to change the supply. If the supply is easily contaminated or under the direct influence of surface water, it may be safer, cheaper or more effective to abandon it and arrange for the property to be connected to a public supply or to have a new borehole drilled. If a new source or borehole is not feasible, checks should be made to ensure that the supply is adequately protected. Earlier in this book, ways of identifying problems and protecting the source have been outlined, whatever the type of supply. As has been said before, it is much better to stop pollution getting into a supply than to attempt to remove it once it is there. Once protective measures have been fitted, repaired or improved, the water should be re-examined under a variety of meteorological conditions to see if there is anything in it that could still cause harm or unacceptable aesthetic problems. Unless the supply is proven to be totally free from any contamination, consideration should then be given to installing a treatment package. The use of technology to treat drinking-water is not a modern invention. Greek and Sanskrit texts dating back 6,000 years contain guidance on the use of charcoal (activated carbon filters), boiling, straining and exposure to sunlight (ultraviolet irradiation) to improve the aesthetic quality of drinking-water and over 4,000 years ago, the Egyptians used coagulants to reduce the turbidity of water (WHO, 2003). If the quality of the water is permanently satisfactory, treatment should be avoided as it may provide an opportunity for introducing possibly pathogenic material into what would otherwise be a sealed system. Treatment systems nowadays are effective at removing chemical contamination and dealing with physical problems such as low pH and turbidity. For most problems, a suitable form of treatment can be found that is designed to deal with the low flows associated with private water supplies.
