Recycled water poses disinfectant problem / | j k ENVIRONMENTAL—Recycling
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^ j F " water, particularly for industrial purposes, is regarded by many as in evitable, if it isn't already here. Like the one-way bottle, however, recycled water presents more problems than it solves, and the most pressing problem is how to disinfect recycled water ade quately. A detailed examination of the prob lems of adequate disinfection has been provided by Dr. Mark A. McClanahan of Georgia Institute of Technology. Al though recycled water is not widely used for human consumption, the increasing ly active regulation of water use by gov ernmental agencies and the militancy of environmentalists have occasionally caused alarm over the adequacy of present methods of disinfection. According to Dr. McClanahan, before deliberate recycle becomes a reality, the possible long-term deleterious ef fects of consuming water recovered from sewage will have to be determined. One way to do this is to study a popula tion that has been exposed to recycled water for a long time. Such a population might be that along the Ohio River, which, says Dr. McClanahan, is esti mated to be about 15% sewage effluent at low flow. Another population might be that along the Rhine River in West Germany, which is estimated to be as much as 40% sewage effluent at low flow. A comparison of these populations with others that have been drinking rel atively clean water would indicate if there have been any effects of recycled water. Some of the potential health hazards may be related to viruses present in the waste water. Studies have shown that viable nucleic acid from virus inactivat ed by disinfectants will survive many disinfection treatments. This raises the question of whether the nucleic acid of an inactivated virus can be released from the protein coat once the inac tivated virus enters the human body. And once released, can the nucleic acid infect the host, causing clinical symp toms of disease? Another question is whether the de struction of the usual indicator orga nism, Escherichia coli, is sufficient to make water safe. Other groups of viruses are known to survive even when the indicator suggests water is safe by con ventional U.S. Public Health Service standards. Dr. McClanahan doesn't think the usual methods are good enough. The present findings, he says, don't indict current standards, but neither do they answer the questions ad equately. To provide water that is safe to drink requires treatment to ensure against the possibility of deleterious effects to hu man health, not just prevent epidemics. This is why, Dr. McClanahan main tains, disinfection must be practiced that will irrevocably destroy all life in
the pathogenic particles present in water. Not all disinfection schemes do this. A more realistic distinction be tween sewage treatment plants and disinfection plants also must be made, he says. Not all the hazards of recycled water come in the form of viruses and bacteria. Consumption of recycled water will increase exposure of consumers to many different kinds of nonliving organic molecules, including those classified as carcinogens, toxicants, mutagens, and teratogens. Even disregarding the presence of chemical organics of known hazard, there is an increasing possibility of reactions between the chemicals present in a given water source after the best disinfecting technique has done its job. The fact is, says Dr. McClanahan, that the best waste treatment plant does not remove all organic compounds, and no treatment short of distillation seems to make such a claim. The result is a definite possibility of chemical reaction J between residual organic compounds in the water and in the disinfectant itself, which must be considered a possible source of materials hazardous to health. If the disinfectant is chlorine, forma tion of chlorinated organic compounds is possible and has been demonstrated on several occasions. As a result of re cycle, there will be an increase in the concentration of these chlorinated or ganics. And the ultimate concentra tions, Dr. McClanahan suggests, might reach nine times the single-pass concen tration. A major point, he stresses, is that because these organic compounds are chlorinated they will be persistent. If all the compounds were no more seri ous to human physiology than chlo rinated hydrocarbons in pesticides used over the past 30 years, there might be less reason to be fearful over the con sequences of recycled waste water. How ever, this view is not supported by data obtained from the World Health Organ ization. Dr. McClanahan believes that funda mental studies must be conducted to define the types of chemicals that will provide a devitalization of the viral nucleic acid as well as the inactivation of the virus particle itself. Some diseases now being diagnosed as caused by en vironmental stresses may be related to the water a person has been consuming for the past 20, 40, or even 80 years. At present, there appears to be some corre lation between hardness of drinking water and heart and blood disease. Chlorine is the most common disin fectant and will probably remain so for some time. However, it may not be the only one or the best one, particularly with recycled water. The most promis ing disinfectant for recycled water in Dr. McClanahan's opinion is ozone, which has been shown to be effective against bacteria, viruses, and cysts
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CIRCLE 48 ON READER SERVICE CARD Sept. 3, 1973 C&EN
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carbon in water? B
total organic carbon volatile organic carbon total carbon Dohrmann's DC-50 organic analyzer makes all of these measurements accurately and rapidly. Based on proven methods, it avoids interferences and undesirable pyrolysis re actions that historically have resulted in significant errors. Here's why the DC-50 is the complete solution for the analysis of carbon in water: D I R E C T READOUT. Four-digit presen tation shows carbon content directly in mg/liter or ppm. No recorder needed! D I R E C T M E A S U R E M E N T . A single sample injection gives either Organic Car bon or Total Carbon content directly, not by difference. INDEPENDENT MEASUREMENT. Volatile Organics are determined sepa rately from Total Organics to aid in source identification. R E L I A B L E M E A S U R E M E N T S . Deter mines important, lightweight volatiles such as low molecular weight alcohols and ke tones, normally lost by acidification and sparging. FAST: 5 minutes per determination A C C U R A T E : repeatability of ± 1 m g / liter or ± 2% W I D E R A N G E : 1 to 2,000 mg/liter (ppm) without dilution P R I C E : $7,500, including start-up assist ance and operator training E P A E V A L U A T E D : Newsletter # 1 5 Oct. 1972 AQCL, N E R C , E P A Cincinnati, Ohio 45268 Contact: D O H R M A N N Division, Envirotech Corporation, 1062 Linda Vista Ave. Mountain View, CA 94040 (415) 968-9710
ENVIROTECH
CIRCLE 24 ON READER SERVICE CARD 46
C&EN Sept. 3, 1973
under many different environmental conditions. Ozone does not undergo dis sociation reactions in water as does chlorine, with the resulting loss in efficiency, nor does it react with am monia to form a less reactive com pound. Ozone is a strong oxidizing agent. A major benefit from the use of ozone is that ozonated organics are more biodegradable than are chlorinated compounds. The major disadvantage of ozone is its thermodynamic instability in water. It also has a very short lifetime. Because of these characteristics, ozone does not provide any residuum that will main tain water protection in case the water becomes contaminated during distribu tion. A big operational problem with re cycled water systems is that there will be a direct connection with a major source of pathogenic organisms. Chlorination alone will not protect the consumer. The best approach would be to improve the reliability of the waste treatment sys tem. Another possibility would be use of a dual disinfectant such as chlorine and ozone. A safety feature of all recycle systems should be an adequate storage system that can be used when either the sewage plant or the disinfection plant breaks down.
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from c&EN • Vitamin B-12—Total Synthesis Listen to Dr. R. B. Woodward's first for mal description of this dramatic work— presented at Wesleyan University. • Vitamin B-12—Biological Aspects International experts discuss biochem istry, biosynthesis, and mechanism of action
—other Science Symposia on Tape also available from ACS— [ j Chemistry & Medicine—Clinical Lab A chemical frontier • Automation in Clinical Medicine A National Bureau of Standards Col loquium • Chemical Engineering Pediatrics At the frontier of chemical engineer ing—a full day symposium • Design of Safer.Drugs Top toxicoiogists air their views • Chemistry of the Moon—I Dr. Urey, other experts reveal their findings Q Nutrition & Public Policy— Food Quality Top Government and industry offi cials spell it out • Herbicides & Pesticides— Policies & Perspectives Hear Ruckelshaus tell it like it is
Toxic gases in fires remain elusive POLYMER—Although burns are an ever present danger in any fire, most fatalities and injuries are the re sult of exposure to and inhalation of smoke and toxic gases. In recent years the chemical factors influencing fire damage and injury have been better identified. However, some of the com bustion products remain elusive entities and others are minor surprises. According to Dr. Irving N. Einhorn of the University of Utah's flammability research center, physiological and toxicological factors in actual fires are hard to separate. He has made a rough anal ysis, however, and says that one of the major causes of injury in fires may be in ability of the victim to see. This is partly due to obscuration by smoke but also to the possibility that combustion prod ucts may adversely affect vision. In ad dition to lacrimation, some combustion products from fluorocarbons may cause severe opacification of the cornea. Hy drogen fluoride, fluorine, and carbonyl difluoride have been shown to be present in concentrations high enough to etch glass, even when there is little or no smoke. It's quite possible, Dr. Einhorn says, that some victims fail to escape a fire simply because they can't see. Another problem is hypoxia alone or in combination with carbon monoxide and noxious gases. Studies of many vic tims of mattress fires, for example, show that they died long before there were any flames to contend with. The in-
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