Rural Water - Quarter 3, 2008 - (Page 14)

be a potential fire hazard. Sodium hypochlorite can release chlorine gas from mixing with other chemicals (acids and alkalis) and from heat. Given these concerns, replacing hypo with gas was a big step, requiring acceptance by all parties with the utility operating personnel presenting a significant obstacle. Since the CRWA system had been using hypo for almost 40 years, any change would certainly require their understanding and cooperation. The utility started the process by explaining the differences between the two disinfectants from their chemical and physical properties to methods of handling and feeding. Questions were asked and answered. Eventually, the operating personnel agreed to try the use of gas. All the four well sites now operate with chlorine gas as the source of the disinfectant. Those systems operate with a minimum of trouble, at the lowest cost and reduced maintenance. Each disinfectant room uses a set of scales to weigh the chlorine cylinders. The 150-pound chlorine cylinders are mounted on each scale and provide an indication of the amount of chlorine consumed. Spare cylinders are stored in the same room. The total amount of chlorine on-site at any time is less than 500 pounds (one cylinder in use, one full cylinder on standby and two replacement cylinders). There is no concern about providing heat since the experience of the Dakota operation showed the ability to feed chlorine gas even during sub-zero weather. Continuous chlorine feed rates of 10 pounds per day (200 gr/hr) are attainable with direct cylinder mounted chlorine gas feeders under sub-zero weather conditions. The need for summertime air conditioning of the room is not necessary since the strength of the chlorine is constant at 100-percent strength. Changing chlorine containers is required on a one- or two-week basis. From an operational point of view, the use of chlorine gas in 150 pound cylinders made a lot of sense. Gas and hypo differences Isn’t hypo safer to use than chlorine gas? 14 • Third Quarter 2008 Not necessarily. The CGDA data shows Th that there are more incidents of injury at water plants from injur hypo exposure than chlorine gas. The fact of the matter is that operating personnel have easy access to hypo and have a tendency to treat it with less respect than chlorine gas. After all, hypo can look like a glass of water. Cal hypo can be mistaken for dish of salt or sugar. Chlorine gas in a metal cylinder is less accessible to the operating personnel and thus has a built-in safety factor. Chlorine gas is treated with more respect. Isn’t hypo cheaper to use than chlorine gas? Hypo, which is made using chlorine gas, is about three times more expensive for an equivalent amount of chlorine gas. The exact value can vary with geographical region and shipping costs. One pound of chlorine gas provides the same oxidizing and disinfecting potential as one gallon (approx.) of hypo solution (12-percent strength). The volume of a 150 pound cylinder is less than 6 cubic feet while the volume of 150 gallons (more than 1,200 pounds) of hypo is about a 19 cubic feet. Since the concentrated chlorine gas has less shipping volume and weight for comparable quantities of chlorine gas, shipping costs are less for gas. Chlorine gas provides a greener shipping footprint than hypo. Isn’t hypo easier to use than chlorine gas? There was a need to educate the operating personnel in the benefits in the use of chlorine gas over hypochlorite. Only this way could complete acceptance be obtained. Chlorine gas requires less maintenance time and cost. There are obvious physical and chemical facts that favor chlorine gas. They would include: Stability — there is no decomposition with chlorine gas, whereas hypo starts to decompose the instant it is produced. Hypo decomposition can be caused by temperature, contamination by metals, exposure to light and UV rays, exposure to metal ions and solution pH. Strength — 100 percent of the chlorine is used in the process. There are no byproducts to be concerned about. Sodium chlorate is a byproduct of hypo decomposition and many hypo solutions contain bromate formed from the presence of bromine salts in the raw materials used in hypo manufacture. Both contaminants are of concern to the EPA and their limits have been set for drinking water. Handling incidents — The handling of hypo is subject to human error more than chlorine gas. The unloading of hypo into tanks containing other chemicals (acids, alkalis, etc.) has resulted in many releases of chlorine gas. Bulk delivery of containers have either leaked or spilled hypo, causing burns on the skin, degradation of clothing, splashing in the eyes and corrosion. There have been numerous incidents reported of spills from trucks on the highway during delivery. Results CRWA has been using chlorine gas for more than eight years. The oncereluctant operating personnel are now chlorine gas advocates. One minor leak developed at a container connection that was quickly rectified and caused no damage or injury. Training helped them understand what to do with chlorine containers if future leaks occur. Additional safety systems, such as automatic shutoff systems that would close the cylinders if a leak were detected by the gas detector, could be considered. George Hanson said conversion to chlorine gas was a no-brainer. Based upon the results to date, it appears he is correct. George suggests that utilities should look at all the facts (costs, maintenance, service, etc.) before considering any change from hypo. When this is done, the case for staying with chlorine gas or converting from hypo to gas is easy to understand. About the author: Gerald Connell is a consultant with more than 40 years’ experience in the handling chlorine and in the treatment of water with chlorine. He has authored two books, “The Chlorination/Chloramination Handbook (AWWA)” and “The Chlorination/Dechlorination Handbook (WEF),” in the use of chlorine in water treatment.

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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