Is Softened Water a Desirable Municipal Supply
Scarcely had the McKeesport water softening and filtration plant been in operation four weeks before a certain professional man of that city declared “that any one who drinks the McKeesport softened water for two years will be dead.” Kindly note, these words did not come from a layman. They cannot be swept aside without further comment as the immature conclusions of an untrained mind. Coming as they do from a man of mature years, wide experience, and supposedly mature judgment, and a member of a profession whose calling it is to preserve human health and happiness, they demand the attention of waterworks men, and it is the object of this paper to examine if such conclusions have any foundation in fact. This is an extreme and drastic declaration, in which few persons will concur; but many persons, who are not acquainted with the methods of water softening, sometimes entertain some doubts in their minds as to the entire wholesomeness of a softened water supply. That water is softened successfully for boiler purposes no’one will deny. But that water intended for domestic use can be softened by chemical processes and leave no injurious matter in the water scents beyond the possible to many, even those who, it would appear, should by their training and experience be in a position to form an accurate opinion on the question. It goes without saying that one answer will not, and cannot cover all conditions; however, by classifying the conditions as generally found we find two very different conditions of hardness requiring softening of water. Waters may posses temporary hardness only, due to calcium and magnesium carbonates being held in solution by the presence of free carbon diox ide. We have also waters whose hardness is due to the presence of soluble sulphates of linn and magnesia; as a subdivision of the latter class we have waters which are contaminated with metallic salts and free mineral acids; of this latter type is the source of supply of the city of McKeesport.
Of course no one should undertake to select a system of softening for any given locality without first becoming thoroughly acquainted with all the varying conditions and peculiarities of that locality’s source of supply. Only a thorough knowledge of such data can result in a successfully designed plant; therefore no one should decide until all the conditions have been ascertained over a sufficiently long period of time to warrant definite conclusions. No definite time can be arbitrarily laid down. It may require months in one locality, and it may require years in another for the gathering of sufficient data. Waters of the first mentioned class, those water possessing temporary hardness due to the carbonates of lime and magnesia being rendered soluble by free carbon dioxide, are very successfully softened by the addition of carefully regulated quantities of lime water or milk of lime. The reaction that takes place is very simple, and consists of an immediate union between the added lime and the free carbon dioxide. As the water is now robbed of its lime solvent proper ties and the carbonate of lime is almost insoluble, the water becomes softened. This process of softening was first invented by Dr. Clarke of England. This method is, however, entirely useless with waters of high permanent hardness, due to calcium sulphates, and only partially successful with waters of combined magnesian and calcium hardness. In softening by this process no prod net of the softening remains in the softened water, as the calcium carbonate formed in the reaction is insoluble and comes down with the rest of the precipitate. The class of waters possessing permanent hardness, as well as those waters which are being ‘contaminated with mine and factory refuse, and therefore hold metallic salts and free sulphuric acid in solution, besides the lime treatment. This frees the water from the acid and forms in soluble metallic hydroxides with the metallic salts, but increases the hardness by the additional gypsum formed, requiring the addition of soda carbonate, which in its turn reacts with the gypsum, and by double decomposition forms insoluble calcium carbonate with the lime of the gypsum, and soluble sodium sulphate, which remains in solution in the finished product. We see at once that in this process there h left in the water a new product, something which is impossible with the process previously described. This product is. however, entirely harmless.and exists in c; nsiderable quantities in almost all natural waters, of known purity and acknowledged healthfulness, This latter process of softening is the one used in the McKeesport plant, which has now been in successful operation for one year. The had conditions of the N oughiogheny river tire so notorious as to require lit lie if any comment. A little over a year ago the published report of the U. S. Geological Survey classed it as “the worst in the country.” Such a sweeping statement does not give much of an idea of the conditions which require softening, in order to make this “sewage drain,” as another expression has designated the stream, yield a clear and wholesome drinking water. Therefore, f will state briefly that the stream is contaminated with mine and factors _ effluent, which renders the water very acid: from the same sources it carries always more or less iron and aluminum sulphates in solution; the water has no temporary hardness, except for brief periods following heavy rainfalls over the water sheds. During such periods the acidity disappears for possibly a few hours. These periods are so brief that they may be considered a neglible quantity. In addition to the above there is a small quantity of carbon dioxide pres cut, but which may even be considered negligible. Numerous weekly tests of the raw and filtered water, during the various stages of the river, have shown that the total solids in solution in the raw water vary between wide limits. The lowest find has been 7 and the highest 110 parts per 100,000; the general average is not far from 14 parts. The filtered water has yielded about 9 per cent less. This shows very clearly that the softening process does not tend to leave a great deal in the water of the chemicals used as is claimed by ignorant critics. The process of softening at the McKeesport plant is that of the well knowm Porter Clark, which has now stood the test for over one-half century, and is the only process which has been thoroughly successful with this class of waters. The chemicals used in this process arc lime of the highest ob tamable purity, and anhydrous soda ash, i. e., soda carbonate. Lime when slaked forms calcium hydroxide, a powerful alkali and an antacid. This is added to the water as a milk of lime and fully saturated lime water. It converts the metallic sulphates in the raw water into insolu hie metallic hydroxides, this includes also the magnesia, the 111 insoluble form of which is the hydroxid. Ihe free and combined sulphuric acid is converted into the sulphates of calcium otherwise known as gypsum. A few minutes after llu .caction is completed the water is treated with a solution of the soda ash, which, as explained above, enters into double decom position with the gypsum and precipitates the lime in the gypsum as insoluble calcium carbon ate, also forming soluble sodium sulphate, which remain in the finished product. The water is thus freed from all the salts of the heavy metals, also of Us gypsum; it has an alkaline reaction and cannot hold more than three parts of cal cium carbonate in solution, of magnesia about :M parts; in other words, the water is softened down to about a hardness of li parts or less per 100,000. M cmrse in actual work this is not always obtainable with Voughiogheny water ow ing to the extreme and sudden fluctuations of the conditions of the rixer. Therefore, the average hardness of the city supply is a little higher than the figure given, but the result is a very acceptable water. .Now to the sanitary question again. Is there anything of an injurious nature left in the water which has passed through this process? Show me the wall or spring water which con tains less of these very same substances. All waters contain them, not only in the small amounts mentioned, but many times this amount. Besides it hanever been proven that lime salts have been injurious to health, even when it has been present in very large quantities. Statistics show that there are places in many parts of the world where waters arc used with impunity which contain uo to loo parts of calcium carbonates per J00,000. Now, as to the soda, none is present in the lnushed product as carbonate, but there are localities where the wells are so charged with soda carbonate that the water acts prejudicially on the vegetation when used for watering purposes, yet it is drunk by men and animals with impunity. If this s true-and the observations mentioned have been carried on for a long time -of waters heavily charged with these substances, is there any likelihood of the small amount remaining in solution in sottened water being injurious? Writers on hygiene fix as an ideal and exceptionally good drinking water, one, which while conforming to other standards oi purity, does not contain more than 20 grains oi mineral matter in solution, per the Imperial gallon; in other words, 28.57 parts per 100,000. As our weekly analysis shows, the softened w’uter at McKeesport contains very much less on the average, we have very good reasons to conclude that water softening is making a very desirable municipal water supply.
‘Paper rciil at the Central States Water Works Association convention, ai Columbus, O.
The advantages obtained are in the saving of soap, preserving of clothes in the laundry, better results in cooking, etc.
Other advantages due to the softening of the water, which we have noticed at McKeesport, are I lie following:
Great diminution in the albuminoid ammonia in the filtered and treated water, which may at times amount to total disappearance of the albuminoid ammonia.
At McKeesport very nearly all bacteria disappear in the process of settling; this result may be peculiar to our water, a> the excess of metallic salts give a precipitate of hydroxide of alumina and iron which is both heavy enough to settle rapidly and are gelatinous enough to entangle the suspended matter, including tile bacteria; this makes filtering easier and the time between the washings of the filterbeds longer. This means also a considerable saving on the wash water. If by these simple remarks 1 shall have created some little interest in the softening of municipal supplies, and thereby the confidence in the process has been somewhat promoted, nty labors have been amply rewarded.