The Hierarchy of Water Quality Cities of the future should have dual water systems. One, accounting for less than 10% of a community’s total consumption, would supply naturally pure water for human consumption; the other would supply reclaimed waste waters for nonpotable purposes.
P
1opulation growth and increased
Why not reuse?
requirements per capita are straining our limited resources of fresh waters, so that reuse is becoming more widespread and more intensive. “Water quality is at a shocking level for the wealthiest nation in the history of the world,” says a recent report. HundTeds of new chemicals, and wastes from their manufacture, find their way into our drinking waters every year, and their significance is difficult to assess. Viral contaminants, particularly those that cause infectious hepatitis, are found in all municipal waste waters and are resistant to conventional water treatment processes. The problem is described in “A Strategy for a Livable Environment,” the report of the Health, Education, and Welfare Department’s Task Force on Environmental Health and Related Problems. Because so many water sources are already polluted, it is not feasible to get ,all water from naturally pure sources. So, the evolution of a hierarchy of water quality seems inevitable. Water for potable purposes5-10% of the total water used in a community-would be taken from uncontaminated sources; the remainder would be supplied from the same polluted sources that are now being widely used. Cross connections would pose little hazard, as the nonpotable source would be bacteriologically safe. The cost of dual systems would differ little from conventional systems, if they are installed as new communities are built. By the year 2000, as much new city will be built as exists today, and use of dual systems would permit sound development of water resources.
Let us first look more closely at the problems involved in using reclaimed waste waters for human consumption. Hundreds of new chemicals are introduced into the market each year; many of them-and the wastes resulting from their manufacture---end up in our water courses. They cannot be completely prohibited from the water environment. Some chemicals, such as those in detergents, have been studied rigorously to establish their toxicity or safety. However, this procedure is long and costly. To require such an assessment prior to their authorization for general use would deprive society of the b e n e fits of important new products for long periods. Also, because of the potentiating effect of some chemicals and the subtle impact they have when ingested over long periods, many of the tests would be inconclusive. Epidemiological data are not available for those contaminants that are now on the scene, and it is not likely that we will come up with adequate data soon. Studies of this kind are not attractive to epidemiologists because the impacts to be assessed are subtle both in the environment and in man. While we can urge that such studies are necessary, we cannot afford to wait upon them in selecting from alternatives in water management. Perhaps the most expedient course of action would be, not to restrict the use of the many new chemicals created by industry, but, to avoid the use of waste waters for drinking water.
672 Environmental Science and Technology
Viral contaminants widespread
In addition to chemicals, the viruses,
particularly those that cause infectious hepatitis, may be significant in the health status of communities taking water from polluted sources. In a paper prepared for the World Health Organization, Chang (1968) concludes that water may be a significant route for the transmission of enteric viral infections and that “water treatment practice should be examined when polluted water is used as a source of supply and sporadic clinical cases of infectious hepatitis and other entero virus diseases exist in a community using the water.” Viral infections may be much more widespread than clinical viral disease indicates. Of infections due to infectious hepatitis and polio viruses, 9095% go undetected. Therefore, sporadic cases of these diseases may not be isolated incidents; more likely, they are clinical manifestations from among a much greater number of subclinical cases. Consequently, discussion and study of water as a mode of transniission for viral infections must not be arbitrarily limited to identifiable disease outbreaks. The occasional clinical case of jaundice from infectious hepatitis may, in fact, be only the exposed portion of the iceberg. In the presence of organic matter, the virus appears to be unusually resistmt to water treatment procedures. In Melbourne, Australia, Stoller and Collman ( 1965) correlated the rise and fall of mongol births (Down’s syndrome) with infectious hepatitis, but offset by about nine months. They postulated that exposure of the mother to infectious hepatitis prior to conception established a greater likelihood of a mongol birth.
FEATURE
Daniel A. Okun Department ofEnvironmental Sciences and Engineering University of North Carolina, Chapel HiU, N. C . 27.514 B ~ : x s e municipal waste waters cxiq cntcric viruses all the time, and
isxauw waste water treatment processes are not effedve in eliminaiiug t h e q we must examine critically the
p s i b i k y of virus 1 ion with current methods of water treatment where polluted waters are used as a souroe of municipal supply and where occasional cases of infectious hepatitis or other intestinal virw dkeases occur. Perhaps, the best recourse for the future is to avoid use of polluted waters as a source of drinking water supplies, just as we avoid use of dkeased cattle and unsanitary farms for milk supplies, even though we h o w we can purify the milk. An rrrrrcr in dual waterrupplii
How then can we guarantee high quality water when population is growing, when industry is spreading, when available resources of naturally pure water are beiig r e d d ? One way is to establish a hierarchy of water s-apply with the quality of water being adapted for the use to which it is p u t This idea is not, of course, new. Maay daerent water sup ply streams are used within a single industrial complex: raw water for cooling, a somewhat higher quality for process purposes, a demineralized water for boiler feed, and a bacteriologically safe water for drinkins Certain parts of the world-the Bahamas, Catalina Island off the coast of southem California, certain areas of Hong Ko7g I~land,and G m d C~IIYOU Village, for exampldual system because fresh water is extremely scarce.
Dual systems are reasonable. Consider the k t sewage systems. They took all drainage both from homes
and from surface runoff. Today we realize that two separate systems are better. Costs of hundreds of dollars per capita are being incurred to separate existing combied systems or to ameliorate the effect of combined systems, and all new communities are now designed with two entirely separate sewage systems. When dual water supply systems are proposed for urban communities, inevitably two important questions are raised: Danger of cross connections. High cost of introducing a second distriiution system.
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Crror cannections no pmbkm We are all familiar with the dangers of dual water supply systems where one is potable and the other, generally only used for emergency, is not. Serious waterborne disease outbreaks have resulted. In the dual system proposed here, the drinking water would be of highest quality, taken from naturally pure sources or produced from brackish or sea water by such processes as distillation. The second supply, providing the bulk of the water, might be of questionable chemical quality, might contain some viral contamination, and might be aesthetically less desirable because of taste or odor. But it would be bacteriologically safe through conventional treatment including disinfection. In fact, the nonpotable supply would be what many cities are now providing. Occasional ingestion of nonp~table water through misadventure would create no problem. Even if this were not discovered for weeks or months, the health effect would not be as bad x that from continuous ingestion of the low levels of potentially toxic sub-
stances over a period of many years. Of course, adequate plumbing codes, utilization of two kinds of piping material, and education of the public would generally lead to acceptance of the two kinds of water. As communities in water-short areas in Iowa have passed water restriction ordinances, well systems have been developed privately for lawn sprinkling, car washing, swimming pools, and the like. The Director of Marketing of Iowa points out that a private water well has become a status symbol. He foresees development of dual water systems, with one grade for human consumption and the other for industrial and other nondrinking uses. It would be preferable for both supplies to be provided by the community water system. Individual wells may have serious impact on ground water levels and may, in fact, provide contaminated waters.
Costimrearesnegligfble
Dual water supply systems should not be dismissed because of cost. Haney and Hamann (1965) showed that the order of magnitude of costs for the dual systems would not be significantly different from conventional systems. They assume that the potable supply would be used for drinking, cooking, dishwashing, cleaning. bathkg, and laundering. Such uses require about 40 gallons per capita per day. If high ruality potable water were used only for drinking and cooking, with all other purposes being served from the second supply, requirements for the potable supply would be less than 10 gallons per capita per day. Another-even more importantfactor in assessing the Haney and Hamann study of cost of dual systems Vdmne 2. Nmnkr 9. S e q t e d m 1968 673
is their assumption that the second potable water supply system would be added to existing conventional system. The c a t of dual system would be signi6cantly less if the two systems were to be installed at the same time. The number of people to be served by public water supply systems will about double by the end of this century. By 1980, more than $21 billion will be r e q u i d for construction of distribution systems alone. Shall these investments be made to bring a water of uncertain quality to consumers, or shall we use this opportunity to consider other alternatives? The urban population of the U.S. will probably grow at a rate of about 4 million people annually-the equivalent of four new San Francisco’s each year. Both private organizations and government have shown interest in creation of new cities, and more than 200 of these cities are either in the design stage or under construction in the U. S. Some are truly experimental, such as Columbia, Md., the Minnesota Experimental City, and the Disney World Experimental Prototype City of Tomorrow (EPCOT) in Florida. With two distribution systems, each system can be better adapted to the specific service. The drinking water lines can be made of materials that are virtually corrosionproof, not only assuring longer life for the pipe but eliminating the effects of corrosion of water quality. Each line could be o p erated at the most desirable pressure. Because drinking water quantities will not be great, high pressures could be used to avoid secondary pumping for high-rise buildings. Also, the nonpotable supply would conform to fire protection requirements. A hierarchy of water supplies would permit development of the optimal sources of water. Because the bulk of the water would not need to meet drinking water standards, it could be drawn from more accessible sources; reclaimed waste waters could be utilized with profit On the other hand, because relatively small quantities would be required for drinking, it would be feasible to go long distances, or to invest in what would otherwise be excessive treatmer?t costs, to produce this high quality water. Dual systems would reduce the requirements for waste water treatment because the receiving stream would not
be a source of drinking water. The greatest advantages of the dual sptem would be that introduction of new chemicals or the outbreak of enteric viral disease would no longer pose a threat to drinking water quality, and that plans can be made virtually in perpetuity to utilize water for drinking and cooking with confidence. Proper planning e s s e n‘tI~
In planning regiondy for future new communities, it would be feasible to use upstream reservoirs for all drinking water requirements. These sources would be adequate for the next decade or so; because the quantities are not great, it would be Teasonable to carry these waters over great distances. For the second, nonpotable supply, nearby run-of-river water could be used, as is now being done in many places. In arid and costal areas, where resources of fresh water are limited, drinking water could be obtained by demineralizing brackish or saline waters. Dual supplies could be more nomical, because large regiotial plants could be built with extensive distribution networks for the relatively small quantities of water required for drinking and cooking. A triple system might be feasible in some instances-for example, in arid coastal areas. Desalinated water would be used for drinking and perhaps other household uses, reclaimed waste waters for toilet flushing and lawn inigation, and salt water for f i e protection. With a hierarchy of water quality, new standards would be needed. These standards would have to be more exacting than current Public Health Service Drinking Water Standards for potable supplies and less stringent for other supplies. Future needs
To establish this hierarchy, we will need help. Chemists, in particular, can help by developing: More sensitive methods for determining water pllutants. More automation in water quality control. More automatic monitoring of b i e logic quality. The significance of long-term ingestion of low levels of water pollutants is very difficult to ascertain. Hueper (1 960) stated, “It is obvious that witb the rapidly increasing urbanization and
ind
* - . -
tion of the country and the
hcmasd demand placed on the pres-
of water from lakes, ent re~~urces rivers, and underground reservoirs, the danger of cancer hazards from the coIwlooption of contaminated drinking water will grow considerably within the foreseeable future.” In addition to well established carcinogens that are isolated from waste waters,Hueper includes radioisotopes (acting in concert with other contaminants), petroleum products, and the aromatic amino and nitro components likely to be found in water. Hueper concludes that “. . available knowledge on intentional and unintentional, actual, wpected, and potential carcinogenic pollutants of water is highly defectivq not only concerning the chemical nature of substances, but also to the carcinogenic effecwith re& tiveness on the consumer.” The prolonged or lifelong consumption of water containing potential carcinogens contributes to the total carcinogenic burden to which an individual is exposed throughout his lifetime, and the quality and quantity of this burden must be identified. The chemical contaminants of concern are the heavy metals. The contribution that water makes to the total exposure may very well be significant. Thus, it becomes essential to assess the inteusity of this exposure as well as exposures likely to result from air and food.
muemntmnmb‘on n&dcd i\s the cost of labor increases, and as the costs of instruments and equipment decrease relatively, the economics of replacing personnel by mechanization and automation become persuasive. For example, we can afford to invest from a quarter to a third of a million dollars in equipment or instruments if they permit replacement of one round-the-clock worker. Our most advanced water and waste water facilities already enjoy considerable mechanization and automation, primarily in handling flows and pressures. Relatively little automation has been introduced for water quality control. Such automated procasing and quality control as has been installed in treatment plants has generally been primitive chlorine residual control or pH contrd. Control of water or waste water
treatment processes IS much more complex, and we can expect to have computerized or programmed control. A continual scanning of all significant parameters will determine operation: as a result, not only will operating manpower he saved, hut the process will be controlled better than an individual could manage. For example, the decision to wash a filter-and the washing itself--can he initiated by a computer programmed to monitor influent water quality, rate of filtration, time of filtering, head loss, and temperature: together with the desired emuent quality, these data determine the optimum time to wash the filter. Similarly, in biological waste water treatment, aeration and biologic floc return would be optimized from a combination of influent waste water quality, rates of waste water flow, and dissolved oxygen levels at influent and effluent. To establish the program for tbis type of operation we need better methods of monitoring quality, considerably more knowledge of the significance of each parameter on the treatment process, and an ability to optimize the total treatment operation through so-called systems analysis. Monitoring biologic quality
Another gap is in automatic momtonng of biologic quality, both in water supply and waste water treatment. At present, one infers biologic safety of drinking water supplies through the use of chlorine residual determinations. Certain residual levels, along with the appropriate contact time, temperature, and pH, assure safety. We need devices to measure biologic quality directly without waiting for indicator organisms
to incubate. This development would permit use of disinfection methods other than chlorine. Of particular importance is a chemical method for determining the presence of viruses in water. Inability to culture the infectious hepatitis virus in the laboratory has prevented us from developing technology for control of tbis endemic disease. Also needed is a method for determining quickly the character of biologic floc used in waste water treatment. Methods for determining the physical properties of this floc are already becoming well established, hut we need to develop rapid measures of sludge vitality. The best prospect for success rests with some type of chemical determination. ADDITIONAL READING
Chang, S. L., “Water-borne Viral Infections and Their Prevention,” prepared for publication in the World Health Organization Bulletin. Haney, P. D., and C. L. Hamann, “Dual Water Systems,” Journal of the American Water Workr Association 57,1073-1098 (1965). Hueper, W.C., “Cancer Hazards from Natural and Artificial Water Pollutants,” Proceedings af the Conference on Physiological Aspects of Water Quality, Pnhlic Health Service, pp. 181-193 (Sept 1960). Kollar, K. L., and A. F. Volonte, “Water and Waste Water Facility Requirements, 1955-1980,” Water and Wastes Engineering, 48-51 (Feh. 1968). Stoller, A., and R. D. Collmann, “Virus Etiology for Dovn’s Syndrome (Mongolism),” Nature 208, 903 (1965).
Daniel A. Okun is head, Department of Environmental Sciences and Engi-
neering (since 19551, and professor of sanitary engineering, University of North Carolina. Previously, he held positions in government (U.S. Public Health Service) and industry (Malcolm Pirnie Engineers). He received his B.S. from Cooper Union Institute of Technology (1937),M.S. from California Institute of Technology (1940). and Sc.D. from Harvard University (1948). In addition to his teaching duties, Dr. Okun is project director, International Program in Sanitary Engineering Design, and director of the Institute for Environmental Health Studies at Chapel Hill. He is coauthor of Water and Wastewater Engineering, and is a frequent contributor to professional journals, including Sewage Works Journal and Civil Engineering. Dr. Okun is a fellow of the American Society of Civil Engineers and the American Public Health Association, a diplomate of the American Academy of Environmental Engineers, and a member of the Water PolIution Control Federation, Harvard Engineering Society, Sigma Xi, and Delta Omega.
Volume 2, Number 9. September 1968 615
