Chlorine replacements would add billions to water costs

Correction: In the article headlined “Chlorine replacements would add billions to water costs,” please read the figures in the y axis of the graph labeled “Estimated cost of constructing and operating small water treatment systems” as $0–450,000 per m/gal day, instead of $0–45,000 per m/gal day. A corrected story follows

To understand chlorine’s contribution to a safe water supply, look at the cost of replacing it

Consultants’ corner
Ronald Whitfield, Francis Brown and Rowena Low/Whitfield & Associates

CONSUMERS IN the US and Canada generally take the availability of safe drinking water for granted. It is only when something goes wrong that the great importance of water treatment pushes its way into the public consciousness, sometimes forcefully.

For instance, when Cryptosporidia contaminated Milwaukee, Wisconsin’s water supply in 1993, the resulting outbreak of acute watery diarrhea killed more than 100 people and sickened another 400,000. In 2000, E. coli contamination of the water supply in Walkerton, Ontario, caused seven deaths, made 2,000 people ill, and cost the community about $45m (€31.91m).

The rarity of such disasters is due largely to chlorine, which has been the chemical of choice in the disinfection of drinking and wastewater for more than 100 years.

Chlorine has come under attack by environmental activists, but their objections should be considered in the light of the benefits it provides and, moreover, the cost and effectiveness of alternatives.

Chlorine chemistry is employed in more than 98% of the water treatment plants in the US and Canada. The technology required is simple, highly reliable and suitable for systems ranging in size from those serving small communities to those serving the largest metropolitan areas.

Chlorine chemistry is also low in cost, easy to use and, most importantly, extremely effective in protecting public health by destroying water-borne pathogens. Further, only chlorine-based disinfectants provide residual disinfectant levels to help protect treated water as it journeys to the tap.

Typically, chlorine gas is mixed with water. The amount of chlorine and contact time depend on the degree of destruction required, the mixing efficiency, the types and amounts of organisms present and the temperature and pH of the water. These conditions destroy viruses and bacteria, although they are not equally effective on all protozoa.

The public benefits from chlorine chemistry in water treatment because it is more cost effective than the use of alternative disinfection techniques. We have quantified this benefit by determining the additional costs that would have to be borne if all of the treatment plants currently using chlorine chemistry in disinfection were to substitute alternative technologies such as disinfection by ozone or UV radiation.

There are more than 63,000 drinking water treatment systems in the US and Canada. More than 92% of them are small, serving fewer than 10,000 customers. About 7% are mid-sized, and only 1% are large, serving more than 100,000 customers.

Nearly 85% of treated water is “ground water” and 15% is “surface water.” Less than 2% of systems disinfect with UV, and they are small systems. About 7% of systems disinfect with ozone and almost all of those treat surface water. The remaining 91% of systems use chlorine, chlorine dioxide and other chlorine-containing materials to disinfect both surface and ground water.

Without chlorine chemistry, approximately 57,000 drinking water systems would have to retrofit their systems to employ alternative disinfection technologies.

Considering the relative costs (see figure below) and current practices in water treatment plants, we believe that few systems would adopt nanofiltration technology. Most large and mid-sized plants would be likely to use ozone, while smaller systems would probably use either ozone or UV treatment.

Modular ozone generation and UV plants could be retrofitted within the confines of existing plants in most cases. In some cases, however, constraints on available space or the inadequacy of existing pretreatment systems would complicate the retrofit and could increase costs significantly.

We estimate that the capital requirements of this substitution in the US and Canada would amount to almost $43bn and cost consumers $8.3bn/year – significant costs, compared with the approximate $20bn in capital improvements committed to treatment plants each year and the near $5bn/year spent to operate them. Almost 90% of the new investments would be required to retrofit drinking water systems.

None of the chlorine-free technologies provide the residual disinfectant properties of chlorine, and waterborne pathogens could reenter the water supply. Water distribution systems would have to be upgraded significantly and better maintained, and consumers would need to add point-of-use treatment options at the tap to ensure the water they received had not been recontaminated.

Point-of use options include the installation of home filtration systems, home UV systems and boiling all water prior to its consumption. The last option is appropriate only for emergencies caused by a temporary malfunction in treatment and distribution.

Home filtration systems are available for as little as $50, but they are difficult to maintain and cannot remove very small particulates, so are effective only against larger microorganisms, such as microbial cysts. Home UV systems also require continuous maintenance, but can be effective against a wider range of pathogens. They are available from a variety of sources at prices ranging from about $300 to $600, with annual lamp replacement costing about $100.

If such systems were required in all of the 230 million-plus households in the US and Canada, as well as the commercial, institutional and industrial systems served by central water treatment facilities, the total installed costs could approach $100bn.

Annual costs for lamp replacement and operating power would be in the order of $35bn/year. Point-of-use costs at hundreds of millions of sites must be higher than those at central treatment plants because of the lack of economies of scale inherent in the installation of such small systems.

Alternatives to the use of chlorine chemistry exist for the treatment of drinking water, but all have limitations with respect to either effectiveness against certain pathogens, the ability to provide residual disinfection capability or cost. The substitution of alternatives for the chlorine-based disinfection technologies currently in use would burden consumers with high costs, both in construction and operation, with the greatest increase falling on consumers served by smaller systems.

THE BIG PICTURE
Chlorine’s influence extends well beyond water treatment. The chlorine-related industry in the US directly and indirectly supports more than 110,000 jobs across the country. It generates more than $60bn/year in sales and plants that manufacture chlorine and its derivatives operate in nearly every state.

If chlorine were not used, substitutes would have to be found for the products and processes now based on chlorine chemistry and new plants and equipment would have to be built to produce these alternatives. Whitfield & Associates selected nine specific end-uses for more detailed analysis and estimated their economic benefit: pharmaceuticals ($406bn); water treatment ($99bn); polyvinyl chloride (PVC) ($18bn); silicon-based products ($17bn); crop protection chemicals ($14bn); fluorocarbon-based products ($9bn); polyurethanes (PUs) ($5bn); titanium and titanium dioxide ($2bn); and bleaches and disinfectants ($2bn).

The sum of annual economic benefits of these nine applications amounted to more than $570bn/year in 2007, a staggering amount of money. If we take the ratio of net consumer benefits to the cost of chlorine consumed (based upon the market price of chlorine), we find the value of this ratio often to be in the range of between 10:1 and 20:1.

Ronald Whitfield is a visiting professor at Northeastern University and president of Whitfield & Associates, a consulting firm. He may be reached at ronaldmwhitfield@gmail.com.

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