Reprinted from the ECHO Newsletter Published by: ECH2O2 Inc. P.O. Box 126 Delano, MN 55328 The information in this newsletter is for research and educational purposes only. It is not intended to be used for diagnostic or prescriptive purposes. SPRING 1992 VOLUME IV, NUMBER IV HYDROGEN PEROXIDE/OZONE FOR MUNICIPAL WATER SUPPLIES? If what the media is saying is true about chlorine destroying the ozone layer, then it is urgent that attention should be given to one of the largest uses of chlorine, and that is municipal water supplies. Some limited experimental studies are being done in the U. S. on the use of hydrogen peroxide and/or ozone as a disinfectant for municipal water supplies. These two substances are widely used in Europe. As an example, 3000 cities in Europe use ozone to disinfect their municipal water supplies. Paris is one of the cities that has used ozone for many years. Los Angeles, California recently installed an ozonator in their water system. Let's take a look at some of the studies that have been or are being conducted. H2S WATER TREATED WITH H2O2 Mohan V. Thampi authored the article "Water Treatment Controlled By H2S Levels", appearing in the May, I991 issue of WATER/Engineering & Management. Thampi says that "More than 90 percent of the drinking water supply in Florida is derived from groundwater aquifers. In Central Florida water wells 500 to 1000 feet deep tap the Floridian aquifer. This raw groundwater is of excellent quality, with all contaminant levels, except for dissolved H2S (aq)." Hydrogen sulfide (H2S) is generally stripped out of the water by cascade tray aeration or mechanical forced-draft aeration. Then it is stored in elevated tanks and chlorinated prior to distribution. Population growth and widely varying water demands have resulted in current processes not being as efficient as they once were. During high demand periods, there is less stripping of H2S, use of higher quantities of chlorine, turbidity (cloudiness) and this results in poor water quality as to taste and odor. Thampi goes on to say "To find a quick and cost effective solution to the turbidity and chlorine residual problem, a pilot test was conducted using NaOH (sodium hydroxide) and H2O2 (hydrogen peroxide) chemicals at the 10 million gal./day Econ Water Plant in Orange County." Finding the correct H2O2 dosage proved difficult initially. "It was found the turbidity occurred despite (the) addition of H2O2 and most of this H2O2 was leaving the tank unreacted. Chlorine demand was unusually low. This meant there was another H2S oxidizing reaction taking place." "Inspection of the insides of the tanks showed high clusters of colloidal sulfur adhering to the tank walls. Thus, it was deduced that the oxygen dissolving during the aeration was continuing to react with the H2S in the tank the tank because of favorable equilibrium conditions. When excess H2O2 was added to overcome the air oxidation, only then would the H2O2 oxidation with H2S proceed. So during startups, it took about 2 days for the H2O2 reaction with H2S to establish its own reaction conditions in the tank. OXIDATION TREATMENT OF WELLS FOR TWO EASTERN CITIES The March, 1991 issue of Public Works contained an article by Dyksen et al about the experimental use of ozone and hydrogen peroxide for the clean up of two contaminated wells. One of the wells is located in New Jersey and the other at Spring Valley, New York. A grant of $66,000 was awarded by American Water Works Research Foundation of Denver to the Ridgewood Water Department. Expertise and financial resources are also being provided by Malcolm Pirnie, Inc. of Paramus, New Jersey, for a total project cost of $115,600. "The project's overall objective is to develop a practical and cost effective means of applying the ozone/ H2O2 treatment system for use at individual public water supply wells. A pilot test unit will be designed to inject, dissolve and contact the oxidants in a pressurized line, simulating conditions in a well pump discharge line." Dyksen et al reported the importance of controlling organic contaminants in groundwater. This can be done by protecting groundwater resources and/or by reclaiming groundwater that has been affected. Chlorinated hydrocarbon solvents and gasoline- related contaminants have been detected in groundwater supply systems. Precautions have been taken at some wells affected by organic chemicals with such techniques as packed tower air stripping and granular activated carbon systems but there are limitations with each process. There is potential for air contamination around packed towers since organic substances are transferred from water to air. With activated carbon there is a need to replace the carbon on a frequent basis and a concern about using it where radon occurs, "because of the potential buildup of radioactive materials in the GAC bed." Methods considered were several Advanced Oxidation Processes (AOP's) because they ". . . have the potential for removing organics from drinking water including ozone, chlorine, chlorine dioxide, permanganate, and hydrogen peroxide." Ultraviolet light alone or in combination with other oxidants was also considered. In the end, ozone and hydrogen peroxide were chosen as having the most potential. Advantages of an in-line treatment of ozone/hydrogen peroxide are the fast destruction of many organic chemicals, adaptability for plant applications, cost-effectiveness and lack of toxic air emissions. Reports should be out soon on these tests. COMPARISON STUDIES OF PEROXIDE AND OZONE An article by David W. Ferguson et al appeared in the April I990 issue of the AWWA Journal and is entitled "Controlling Taste and Odor Compounds, Disinfection By products and Microorganisms." It describes the third of a five phase pilot project being conducted by the Metropolitan Water District of Southern California, ". . . in evaluating the hydrogen peroxide ozone (PEROXONE) advanced oxidation process----(followed by secondary disinfection with chloramines) for removal of taste and odor compounds, control of disinfection by- products (DPM's), and inactivation of microorganisms." The water being treated is from the California State Water Project and the Colorado- River. At the pilot plant facility, ozone is bubbled through four glass ozone contactors. Just prior to this, the raw water can be treated with hydrogen peroxide by means of a metering pump or in-line static mixer. The water depth is maintained at 16 feet and water treatment times varied up to 12 minutes, as do the levels of oxidation treatments. The article contains some plant schematics, numerous tables and charts describing the experiments and their effects on contaminants, effect of contact time, oxidation residuals, etc. Further studies will be conducted through the mid-1990's as the five phase process continues. Thus far, the study concludes that PEROXONE is significantly more effective than is ozone alone in oxidizing taste and odor compounds. As reported in a previous newsletter, a pilot plant was being designed "to cleanse San Fernando Valley water-supply wells of industrial solvents." This was reported in the March 25, 1988 issue of the Los Angeles Times. Hydrogen peroxide and ozone were selected over alternative processes because they remove contaminants from the water without creating hazardous waste problems. The initial design cost for the plant at North Hollywood was $423,200, the cost of the plant that was to be built to range from $500,000 to $1.5 million. The plant was designed to break down trace chemicals including TCE and PCE. Wells eventually to be treated are in Los Angeles, Burbank, Glendale and in the Crescenta Valley County Water District. "More than 2 dozen wells have been shut down because of pollution."