Ground Water in the Norwalk, Suffield, and Glastonbury Areas, Connecticut

Corrosion, or " pitting," is caused chiefly by the solvent action of free acids on the iron of the boiler. Many acids have this effect, but the chief ones are those freed by the deposition of hydrates of iron, aluminum, and especially of magnesium. The acid radicles that were in equilibrium with these bases may pass into equilibrium with other bases, thus setting free equivalent quantities of CO3 and HCO3 ; or they may decompose carbonates and bicarbonates that have been deposited as scale ; or they may combine with the iron of the boiler, thus causing corrosion; oV they may do any two or all three of these. Even with the most complete analysis this action can be predicted only as a probabilit3^ If the acid thus freed exceeds the amount re- quired to decompose the carbonates and bicarbonates it corrodes the iron. The clanger from corrosion obviously lies in the thinning and weakening of the boiler, which may result in explosion. The formula for the corrosive tendency ^ used in computations based on the anal- yses expresses the relation between the reacting values of magnesium and the radicles involving carbonic acid. If c is positive the water is corrosive, for this represents an excess of magnesium over carbonate and bicarbonate. If c— 0.0499 Ca (the reacting value of the calcium) is negative the carbonate and bicarbonate taken together can hold both the calcium and magnesium, and corrosion will not be caused by the mineral constituents. If c— 0.0499 Ca is positive the ability of the carbonate and bicarbonate to hold the calcium and magnesium is uncertain and corrosion is uncertain. These three conditions may be represented by the symbols C (corrosive), N (noncorrosive), and ( ? ) (corrosion uncertain) . (For formulas see page 54.) In working with the assays it is necessary to restate the conditions, as the amounts of calcium and magnesium are unknown. One-fif- tieth of the total hardness is equivalent to the reacting value of cal- cium and magnesium, and H divided by 230 (or 0.004 H) is equiva- 1 Meiulenhall, W. C, Dol(», R. B., and Stabler, Herman, op. cit., p. Go. GROUND ^\'ATEl; IXIR PUBLIC SUPPLY. 59 lont to tlio iViK'tiui:- vahu' of niao'iu'siiim on llu- :i>siiiiij)rK)H that Ca^r^^J jMii". a ratio whii-li £>i\-es niagncsiuui its .smallest probable value relative to caleiuiu. The reacting- values of carbonate aiul bi- carbonate are repre.sentcd, i-espcctively. by O.OSo CO.. and 0,016 HCO3, each coefficient being the ratio of the valence of the radicle to its molecular weight. The following propositions result: ■ If 0.0;V> CO,+0.0U) ITC(),>().0'2 II, then the mineral matter will not cause corrosion. Tf 0.0:);^ C().;+0.()1() HCO;;<0.(K)4: H. then the water is corrosive. If ().0;',8 CO.I+O.OIG HCO,<0.()2 H but>0.0()4 H. tlien corrosion is uncertain. Scale forruation. foaming, and corro.sion are the principal criteria in rating waters for boiler use, but their evaluation is a matter of i)ersonal experience and judgment. The committee on water service of the American Kaihvay Engineering and Maintenance of Way As- sociation has offered two classifications by Avhich waters in their raAv state may be approximately rated, but, as their report states. '• it is difficult to define by analy.sis sharply the line between good and liad water for steam-making purposes.'' Their tables, which are given below with tlii> amounts recalculated in terms of parts per million, Avere used in rating the waters for this report. In every case the less favorable of the U\o ratings was given. U'dlitiys of iratrr for Iioilcr ii-'se accordlnci to incn(stiii<i ojid (■orrod'nKj inyre' dirnt.s (111(1 to foainvu/ ingredievt^f- Tncrnstin;; and corroding ingredi- onte. Foammg intcreciifnts. Parts per miilioii. Classification. 6 Parts per million. I'U-.i.sifieation.c More than— Not more than— More than— Not more than— 90 200 430 Good. Fair. Poor. Bad. 150 Good. Fair Bad. Very bad. 90 200 430 150 250 400 250 400 oMcndenhali, W. C, Dole, R. B., and Stabler, Herman, Groxmd water in San Joaquin Valley, Calif.: !.'. 8. Cieol. Survey Water-Supplv Paper 398, p. 07, 1916. b Km. Railway Eui". and Maintenance of Way Assoc. Proc. vol. 5, p. 565, 1904. cldeni, vol. Ol p. 13!, 1908. Qualify of ■water for domef^tie use. — Waters whose harthiess does not exceed 200 parts per million and which are sufficiently low in mineral matter to be palatable are satisfactory for drinking and cooking. Althougli Avaters high in hardening constituents can be used for drinking they are unsatisfactory for cooking and launder- ing. Hardness exceeding 1.500 parts per million makes water unde- sirable for cookino;, and water much softer than that consumes 60 GROUND WATER IN NORWALK AND OTHER AREAS, CONN. excessive quantities of soap in washing. Approximately 200 parts per million of carbonate, 250 parts of chloride, and 300 parts of sul- phate can be detected by taste. Considerably higher amounts of these constituents can be tolerated by a human being, but more than 800 parts per million of carbonate, 1,500 parts of chloride, or 2,000 parts of sulphate is apparently intolerable to most people. How- ever, local conditions and individual preference largely determine the significance of the terms " good " or " bad " as applied to the mineral quality of water for domestic use. CONTAMINATION. Water supplies may become contaminated in various ways, chiefly by industrial and manufacturing wastes, by the washing in of sur- face drainage, or by sewage. The objectionable materials derived from industrial wastes are largely chemical ; those derived from sur- face wash or seAvage are organic, the germs of disease. As industrial wastes do not frequently pollute ground-water supplies, they are passed over briefly in this report. Sea water causes serious trouble in parts of the Norwalk area but need not be considered except in a strip along the shore of Long Island Sound. Sewage is 'a very serious clanger and is of various sorts, including animal excreta, human excreta, and kitchen wastes. It is only through a nearly criminal neglect of the elementary principles of h3^giene and sanita- tion that these substances ever get into water supplies. Wells should never be constructed where there is any possibility of underflow from barnyards, latrines, or kitchen drains. No spring that is thus wrongly situated should be used. No bai-nyard, pigpen, latrine, or kitchen drain should be built in a situation where it might pollute a well or spring. No rule can be laid down as to the direction of flow of the underground water, though it is in general the same as the direction of slope of the surface of the ground. Similarly no rule can be given as to what may be considered a safe distance between a well or spring and a source of pollution. To be safe this distance should always be made as great as possible. The excreta of all animals, especially of human beings, contain considerable amounts of chloride that has been taken into the body in the form of sodium chloride (common salt) and discharged in the same condition. The human excreta are richer in chloride because liuman beings are able to obtain more salt. Chloride is a normal constituent of all waters in Connecticut and is derived in part from the sea by the agencj?- of the wind, which carries inland small amounts of salt-laden spray. There is, then, for every point a " normal " amount of chloride, the amount that is normally carried there by the wind. Along the shore of Long Island Sound it is rather large, GR0U:N'D WATEi; FOn PUBLIC SUPPLY. 61 but inliiiul it is siiiall. I'lio uiiiount of cliloriile in iiormnl watei's of Connectiout lias been determined for different parts of the State tind slioAvn on maps ' indicating!: the normal distribution of chloride by means of isochlors, or lines dehnin.i!; areas within which the waters in their natural state contain certain definite amounts of cliloride. In the SufHcld area the normal chloride is about 1.5 parts per million, and in the (ilastonbury area about 2 parts. In the in- land portion (Ridgefield) of the Norwalk area the normal chloride is from 2 to 2.5 parts per million, but alon^; the shore it is much irreater. This wind-blown salt is almost the only normal source of cidoi'ide for Avatei's deri\ed from the crystalline rocks, the till, or the stratified drift, though it is possible that some of the sandstone Nvaters have dissolved small amounts of salt that was included in the sediments dnring their deposition. Chloride may be readily and accui-ately determined by the chemist. Any water which has an un- due amount of chloride should be looked on with suspicion and should not be used in its raw state unless frequent bacteriologic ex- amination shows it to be indubitably safe. Many of the cases of tA'phoid fever that have occurred in the State have been traced to water supplies contaminated by human excreta.