Rural Water - Quarter 3, 2008 - (Page 13)

these requirements. The disinfectant chosen was sodium hypochlorite (hypo). The water was pumped from the wells to distribution and storage with hypo added with positive displacement, chemical feed pumps. Dosages of approximately 2 mg/L (ppm) were sufficient to provide the desired system residual. Hypo was supplied in bulk by truck for offloading to CRWA tanks. The 12-percent strength solution was transferred from 1,500 gallon plastic containers on stake bed trucks to both the on-site feed and storage tanks at each well site. Some small systems pump directly from the bulk shipping containers placed at each site. Other small water systems have used common, household bleach (5-percent strength) and pump directly to the system from the bleach container. Operation change For more than 30 years, CRWA functioned using the hypochlorite feed system for disinfection. In the 1990s, a new general manager, George Hanson, arrived. His previous experience had been with regional rural water systems in North Dakota. One of his first actions was to evaluate the system and its operations so that he could determine its needs and institute improvement programs where needed. His objective was to reduce the operating and maintenance costs, reduce the labor intensity required by the hypo system, simplify the system while maintaining the high quality of service to which the customers were accustomed, and the operating personnel provided. George saw the need to simplify the disinfection operation and replace the labor-intensive and chemically unstable feed system. His successful experience with chlorine gas in the Dakotas led him to recommend a change to a simpler, more stable chemical that offered a simplification of the system. He recommended that hypo be removed as the disinfectant and replaced by chlorine gas. This recommendation ran counter to the general trend in the industry. Perception/reality There was, and is, a great deal of pressure from engineers, regulators, elected ofﬁcials, the general public and environmentalists to have the industry move away from chlorine gas to bulk delivered or on-site generated sodium hypochlorite. The perception that chlorine gas is unsafe has been in the forefront of public awareness since the 1980s This perception has been stoked by recent newspaper headlines relating to the explosive devices strapped to chlorine containers that had been used in Iraq. For years it has been common to see headlines in the newspapers proclaim a “chlorine leak,” “chlorine gas” or “chemical explosion.” The implication was that chlorine gas caused these events. The Chlorine Gas Disinfection Association analyzed the incidents reported in the news media in the late 1900s and early 2000s where words similar to those appeared in headlines. The analysis of these incidents showed that between 60 and 65 percent of the chlorine release incidents that occurred were hypochlorite (calcium hypochlorite and sodium hypochlorite) based. Fifty percent of these incidents had chlorine in the headlines with the implication that chlorine gas was the source of the leak. Chlorine gas was blamed by inference. These headlines helped the public develop a misperception of the actual situation. While it is correct that chlorine gas is toxic and supplied under pressure, in 150 pound cylinders, ton containers, tank trucks and rail cars, the handling and use of the containers has never been safer. There are more than 50,000 water treatment sites and many use chlorine gas from 150 pound cylinders. Only the larger systems, an estimated 1 to 2 percent of the water treatment facilities, receive chlorine gas in large quantities or containers such as ton containers, tank trucks or railcars. The CRWA hypo system operation required a great deal of maintenance and service. Chemical feed pumps required frequent cleaning of check valves, gasket and diaphragm replacement. In addition, the chemical cost for hypo was as much as three times greater than chlorine gas. A great deal of time and effort was being used by system personnel to operate and maintain the hypochlorite disinfection system. Each well house had a disinfectant room and a pump control room. Each disinfectant room was difficult to keep clean due to the formation of white precipitate from the solutions appearing at piping connections and at tank seams. Frequent cleaning of the hypo feed tank due to the sediment that appeared in the bottom of the feed tanks was required. In the summertime, air conditioning of the room was necessary to help maintain the strength of the solution. A constant odor of chlorine was noticed in the disinfectant room. This contributed to corrosive conditions in the room. Operators’ clothing frequently was splashed with hypo, causing deterioration and requiring frequent replacement. Since the strength of the hypo changed over time, a constant adjustment of the feed pump rate was required to maintain the correct feed of chlorine and provide the desired residual in the distribution system. The solution George Hanson used chlorine gas at the North Dakota water systems and considered replacing hypo with chlorine gas. Resistance was met from all sides, but mostly from the operating personnel. The perception that chlorine gas is more dangerous than hypo was the major obstacle to overcome. The truth is that all forms of chlorine may create dangerous conditions. This includes the “on-site” generation of chlorine. Several incidents have been reported of explosions at installations of on-site generators. Calcium hypochlorite can have chlorine gas releases and can >>14 While it is correct that chlorine gas is toxic and supplied under pressure, in 150 pound cylinders, ton containers, tank trucks and rail cars, the handling and use of the containers has never been safer. Third Quarter 2008 • 13

Table of Contents Feed for the Digital Edition of Rural Water - Quarter 3, 2008

Rural Water - Quarter 3, 2008 Contents From the President From Hypo to Gas - A Forward Leap If You Lose All Your Data Today... Would You Still Be in Business Tomorrow? Weaving the Wireless Web Rural Water and the Farm Bill Ensuring Your Water System's Security Guarding Against Becoming a Victim of Fraud 10 Ways to Improve Utility Efficiency New Technology Making a Difference By Being Involved Regulatory Update Source Water Protection Corner Throwing My Loop Cub Scouts Visit Alliance of Indiana Rural Water's Spring Conference Advertisers.com Index to Advertisers From the CEO

Rural Water - Quarter 3, 2008

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