DISEASE CARRYING BACTERIA MAY BE HELD IN WATER

Bay of Plenty Beacon, Volume 14, Issue 4, 27 June 1949, Page 7

DISEASE CARRYING BACTERIA MAY BE HELD IN WATER

Clear sparkling water may harbour disease-carrying bacteria, and water very pure from a health aspect may be destructive to fittings and hot water cylinders, but most of New Zealand’s water supplies need no treatment. The local authorities of New Zealand are responsible, for the provision of adequate water supplies in their area. One or two of these bodies maintain small laboratories for chemical and bacteriological checks on the water supplied by them, but this is supplemented by research at the Dominion Laboratory of the Department of Scientific and Industrial Research. For the large number of authorities with no facilities of their own, the Dominion Laboratory in conjunction with the Health Department carry out the testing of water. The only certain method of finding out if water is fit to drink is by laboratory examination, said Mr H. J. Wood, of the Dominion Laboratory, for although water by appearance is clear this only indicates that there is no suspended dirt or silt in it. Typhoid and dysentery bacteria remain in a more or less dormant state in water, but they multiply and start their deadly work when absorbed in the body, Drinking water should always Ibe boiled unless it is definitely known to be pure, for the sparkling stream Or the clear-looking well water may harbour millions of disease carrying bacteria. N.Z. Water Satisfactory Most of the artesian water of New Zealand is satisfactory for drinking and other uses, and it needs no treatment. ' Sometimes, however, it has disadvantages because of its purity; the very pure water may be “aggressive” because the dissolved gases in it attack brass fittings in valves and taps and are very destructive to pipes in boilers and hot water systems. The oxygen attacks the metal in the absence of organic or mineral matter on which to expend itself. If carbon dioxide is also present the fittings and pipes may need renewal in 12 months or so. In these instances the water may be passed over beds of marble or lime t<3 remove the co2, and water for boilers is made less destructive by preheating to drive off the dissolved oxygeii. A supply of water showing an excess of iron content (which gives a taste to the water if the propor-

tion is only one part of iron to two million parts of water, and, is noticeable by stains formed on bath or basin by dripping taps) is usually in New Zealand corrected by boring deeper or changing the source of supply. Iron, which is more usual in artesian water, can be removed by l 'the apparently simple method of aeration settling and filtration, or by base exchange process, but the equipment required is expensive and difficult to maintain and so this process is usually avoided.

Apart from iron in water, there are also “iron bacteria” which can flourish when there is organic matter in water. They derive iron from the pipes, and form an accumulation of slimy rust-coloured deposit in pipes and tanks.' Most growth in water requires air and light, but these iron organisms need neither, and once established can flourish throughout the recticulation, blocking the pipes and giving an objectionable odour. This trouble may be prevented by lime treatment of the water or by sterilis-

ing of mains by chlorine or chloride of lime. We in New Zealand draw most of our water fresh from mountain stream and river, or from lake or artesian well—and on the whole it is very good water, too. But unless we are careful to avoid pollution of our water resources, this state of affairs may not always persist.