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CONFERENCE ON FRIDAY, JULY 25TH, 1884.
II.-QUALITY OF WATER. FILTRATION AND SOFTENING.
Sir FREDERICK ABEL, C.B., F.R.S., in the chair :
The CHAIRMAN, in commencing the proceedings, said the outcome of the previous day's discussion showed that there was agreement, at any rate, on some important points. All agreed that the water supply was derived from rainfall, though perhaps, with the exception of Mr. Jabez Hogg, who spoke of the illimitable supplies stored in the chalk. The importance of the systematic observations introduced by Mr. Symons, and the value of the data derived from those observations as indicating the relative abundance or scarcity of the supply of water in different districts, and their relation to the population of the districts, were also unanimously recognised. In connection with this matter very useful information had been supplied by Mr. Topley, Mr. De Rance, and Mr. Whitaker, and the maps prepared by the latter gentleman promised to be extremely valuable. There could be no doubt that a combination of careful hydrogeological surveys, with a study of rainfall observations throughout the country, would serve to enlarge our knowledge with regard to the conditions to be fulfilled for securing an efficient water supply to different parts of the kingdom. It was only natural that the discussion with regard to the sources of supply should gravitate towards the larger towns, and more especially towards the supply of water to London, which had been of late a question of such serious controversy. Mr. Bailey Denton, however, in his interesting communication, had referred more especially to the supply of rural districts or small communities, and it might be hoped that the disinclination of local authorities, to which he referred as having stood in the way of progress, was rapidly disappearing. There could be no question that the country generally was now thoroughly alive to the necessity for obtaining for all communities, large or small, as pure a supply as could be obtained. In connection with this subject, Mr. Denton gave interesting information with regard to the application of tube wells ; he might say that in connection with military matters he had had considerable experience of the usefulness of such wells, and so long as it was not necessary to apply power in connection with them, and a moderate supply only was required, their use would be attended with very considerable advantage. With regard to large towns, there was also a consensus of opinion to the effect that in order to ensure as pure a supply of water as possible, it should, if practicable, be obtained at its source, rather than after it had been more or less polluted by passing along streams and receiving surface drainage or still more objectional matters in its
With the exception of Mr. Hogg, he also thought they were all impressed with the fact that the necessity not only for having water pure, but for keeping it until used in a perfectly pure condition, gave rise to a wide spread objection to intermittent supply, and to the consequent necessity of having tanks in houses, in which the water inevitably became more or less polluted. It was somewhat remarkable that Mr. Hogg, in his search for the minute animalcules on which he based such important conclusions, should have entirely overlooked the grosser impurities which everyone else found in the cisterns,
With regard to the supply from wells, Mr. Baldwin Latham had directed attention to two or three important points ; for instance, to the necessity, in estimating the quantity to be derived from such a source, for ascertaining what was likely to be the minimum supply from those wells, and regulating the number of wells accordingly. There was no question that this might be a matter of considerable difficulty for water engineers to meet. He had also directed attention to an incidental point, which, as he (the Chairman) had pointed out, the Conference could hardly deal with, but which it was impossible to keep entirely out of sight, viz., the influence of wells in reducing the supply of water to streams in their neighbourhood, and the consequent questions of property which would arise. Upon the question whether the water supply should be taken from rivers or wells, there were great differences of opinion. Some believed that, although it would be most desirable to have water absolutely pure, yet there were considerations weighing somewhat strongly in favour of obtaining water from convenient streams, as high up the source as practicable, and to apply, in connection with such supply, the most efficient means of mechanical, and, if possible, chemical purification. Others took a somewhat poetical view with regard to the supply from deep wells, and utterly ignored the possibility of any contamination of such water, and seemed to think that you had only to sink any number of wells as close together as they could be placed conveniently, to obtain any amount of water to supply a town of any size. Those were points upon which differences of opinion would always exist until the matter was put to a practical test on a large scale. Again, many, in referring to the hardness of the water, said that companies had no business to give hard water; that they had only to adopt a softening process, which costs little or nothing; and that if a water company were allowed to supply water they should only supply it in the softest condition in which it could practically be produced. Of course that was a very natural demand from the point of view of the consumer, but it remained to be seen how, if they drew water from deep wells for the supply of London, a softening process could be carried out on the gigantic scale which would then be necessary. With regard to that point, they looked forward to have some valuable information given them by Mr. Homersham and also by Mr. Baldwin Latham.
WATER FOR DOMESTIC USE.
By S. C. HOMERSHAM, M.Inst.C.E. WATER for domestic use, and for distribution through pipes into dwellings in cities, towns, villages, and other places, should be derived from sources that afford adequate quantities at all seasons, characterised as being :
1. Wholesome for drinking, for culinary, and for other uses.
2. Soft without having the power to dissolve or injure lead, and well adapted for washing the person, for use in baths, and for use with soap.
3. Of a normal uniform temperature at its source equal to the average of the climate for the year, which in England differs but little from 50° Fah.
4. Well aërated, holding in solution eight or more cubic inches of gases per gallon, namely, about two of oxygen, six of nitrogen ; agreeable and refreshing when drunk.
5. Clear, transparent, colourless, bright, and, when seen in large bulk, pure blue, the natural colour of uncontaminated water.
6. Unable to cause a deposit or fur in the utensil in which it may be heated or boiled.
7. Free from organisms, animal or vegetable, living or dead, and any matter in suspension.
Water in its natural or normal condition characterised by all these seven qualities may be abundantly obtained in some portions of the globe. It abounds in parts of Brazil, in parts of New South Wales, and doubtless in other
places. Such water, however is not abundant in the United Kingdom.
Here it is difficult to find a source that will yield a considerable quantity of soft water associated with the other six named qualities; or to find a source that will yield an abundant quantity of soft water associated with qualities 1, 3, 5, 7.
Water, inland, is all derived from rains that fall on the surface. Land, composed at or near its surface of sand, gravel, chalk, and some other limestone, absorbs nearly all the rain that falls upon it and stores in its pores the greater portion below ground. Other land, consisting of clay, granite, millstone, grit, and other impervious rock, absorbs hardly any of the rain or snow that falls upon its surface. For the most part it flows off the land into valleys, and forms brooks, rivers, or floods. Sometimes the rivers or floods are collected in natural impervious hollows or basins, thus forming natural lakes.
Sometimes artificial hollows or reservoirs, or lakes, are constructed in valleys to catch and impound river and flood water, to supply or feed canals, or to be stored for domestic use. Thus the sources from which water can be obtained for the supply of a population, or for manufacture, or other uses, are
1. Brooks, rivers, and natural or artificial lakes. These may all be called surface waters.
2. Springs that often naturally issue from the sides of valleys into brooks or rivers, and other subterranean water stored in the pores of rocks below ground, may be collected above ground or by means of wells, bore-holes, and underground adits or tunnels. Such water may all be termed subterranean or spring water. Water, however, whether surface or spring, is all derived from rain falling on land, mostly on uplands or hills. All brook, stream, or river water ultimately finds its way by gravitation into the sea through uncovered channels, or rivers, that may be seen, and are often navigable, providing inlets and outlets for vessels from the land into the ocean, or from the ocean inland.