Proposed Revisions in Chemical Standards for Drinking Water J . K. H O S K I N S , Senior Sanitary Engineer, United States Public Health Service, Washington, D. C.
TΗΕ Treasury Department drinking water standards, adopted October 2 1 , 1925, are concerned with drinking and culinary water supplied b y common car riers in interstate commerce. In com pliance with widespread requests for re vision, the Surgeon General of the Pub lic Health Service has appointed an Ad visory Committee to consider desirable changes in the present standards. Each national organization interested in some phase of the subject is believed represented by membership on this Advisory Commit tee. In order to facilitate procedures, a small subcommittee of service officers was designated to prepare a preliminary re vision of the text for consideration of t h e committee. This revised statement, e m bodying suggested modifications as pre pared by the subcommittee, has been fur nished to the full committee membership for review and comment and for views of the organizations which they represent. The present standard states, with respect t o t h e physical and chemical characteris tics of drinking water, that "the water should be clear, colorless, odorless, and pleasant to the taste and should not contain an excessive amount of soluble mineral sub stances nor of any chemicals employed in treatment". In the present Appendix IV, quantitative values are given for cer tain physical and chemical characteristics which should not be exceeded b y accept able supplies. In the standard it is fur ther stated that the presence of lead, cop per, or zinc in excess of the limits suggested in the Appendix—0.1, 0.2, and 5.0 p. p. m., respectively—shall constitute grounds for the rejection of the supply. In the proposed revision t h e limit for lead has been left at 0.1 p. p. m.; for copper it has been raised from 0.2 to 2.0 p. p . m.; and for fluoride i t has been tentatively placed at 1.0 p. p. m. T h e limit for zinc has been omitted entirely. In the Appendix accompanying the revision, which refers to the chemical and physical characteristics, the following substances have been added to these for which limits were suggested in the 1925 standard: boron, not to exceed 20 p. p. m.; and selenium not to exceed 0.1 p. p. m. Changes in t h e present standard concerning desirable limits for other substances are: zinc raised from 5.0 to 15.0 p. p. m., magnesium from 100 t o 125 p. p. m., caustic alkalinity from 0 t o 15 p. p. m., carbonates of sodium and po tassium together from 50 t o 100 p. p. m . The limit for total solids has been reduced 1 Presented before the Division of Water, Sewage, and Sanitation Chemistry at the 102nd meeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J., September 8 to 12, 1941.
from 1000 to 800 p. p. m. and the desirable residual alkalinity of 10 p. p. m. now in effect is n o t mentioned. A further proposal under consideration is t h a t hexavalent chromium or its salts should n o t be present and also that until reliable data on the physiological effects of polymetaphosphates are obtained their use in excess of 2.0 p. p. m. should be avoided. Improvements in bacteriological tech nique, particularly for determination of the coliform group and the interpretation of t h e results, have indicated t h e advis ability of modifying the statement of the bacterial part of the standard to conform more nearly with accepted practices. No material increase in the stringency of the standard is contemplated. No evidence is available that waters which are produced in conformance with t h e present require ments transmit disease. The evidence is quite to t h e contrary. Certain features of t h e bacteriological requirements, however, are under con sideration. One concerns the examination of larger portions than the 10 ml. size now specified. Where the coliform density is approximately 1 per 100 ml. of sample ( t h e upper limit permitted by t h e present standard), it can be shown readily that the examination of 10 ml. portions does not permit t h e detection of the coliform group b y the dilution method in this range. B y increasing the size of portion examined this difficulty is overcome, and the result may indicate an approach to t h e limiting value s e t by the standard and consequently permit the inauguration of remedial meas ures before the permissible bacterial limit i s exceeded. It seems desirable also to avoid t h e o c currence of periodic breaks in t h e bacterial quality of approved supplies, lapses i n which now are possible because results are averaged over long periods. I t i s sug gested that the period for averages b e limited t o one month. In other words, a n y water supply before it can b e a p proved should meet both requirements of t h e standard during any one month. How ever, when a result is indicative of sig nificant pollution, it is suggested that a t least daily samples be examined until s a t isfactory bacterial quality is again a t tained. It is advisable also that due attention be given to the water quality as delivered t o t h e consumer and not alone at t h e inlet of the distribution system. I t is proposed, therefore, that a specified minimum num ber o f samples be examined routinely from various points in t h e distribution system,
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the number to be governed by t h e aver age daily volume of water delivered. The need for improvement in t h e stand ardization of laboratory techniques t o bring procedures into conformity with those approved fully by t h e American Water Works Association and American Public Health Association is also a c knowledged. It is suggested t h a t labora tories and laboratory methods b e subject to the inspection of the certifying authority and that failure to comply with specified procedures shall be cause for refusal of certification of t h e water supply. No significant changes have been sug gested in that part of the standard per taining to sources and protection. Some additions have been proposed t o the list of sanitary defects in water systems, as well as supplementary material in an appen dix concerning sanitary requirements for water purification and distribution sys tems. This supplement i s intended pri marily as a guide for inspecting officers. Consideration is being given also to limiting bacterial concentrations of raw waters undergoing various types of treat ment. These bacterial loads are ex pressed in terms of allowable maximum densities of coliform bacteria present in t h e untreated waters. Experience has indicated that there is a very definite rela tionship between t h e coliform content of t h e raw and finished water subjected to any particular type or combination of types of treatment, and t h a t i f such load ing limits of treatment processes are ex ceeded, defects in bacterial quality of the affluent will occur. It is realized that all the changes pro posed will not meet with t h e unanimous approval of t h e waterworks profession. The present standards d o n o t enjoy such complete acceptance. However, an earn est attempt will be made to develop a rea sonable statement of t h e requirements of a safe, potable drinking water. The Ad visory Committee members are receptive to constructive criticisms and suggestions concerning t h e present standards and pro posed revisions.
T h e AMERICAN C H E M I
CAL SOCIETY membership, through the adviser designated by its officers, has a direct representative t o whom its views may be expressed, and each suggestion will be given every consideration during the formulation of changes. The sole purpose of t h e Public Health Service in this activity is one of active cooperation with t h e profession in t h e maintenance of the high standards of quality of the drink ing water supplies of our country a s they are available to common carriers,
