Tablet chlorination, used as an alternative to the traditional chlorination methods of gas and liquid, provides a unique combination that accurately and safely delivers chlorine to drinking water systems; however, there are many misconceptions that pervade the potable water industry obscuring the facts. Using simple chemistry and engineering, it can be explained why and how tablet chlorination, along with the use of calcium hypochlorite tablets, can be a safe and cost-effective method for water treatment.

　　The Importance of Alternatives In the drinking water industry, chlorine gas and liquid bleach have long been the standard chemical used in water chlorination and disinfection. The practice of using chlorine in drinking water treatment has been acclaimed as one of the most significant public health advances of the 20th century, if not the entire millennium. More than 98% of water treatment plants use some form of chlorine to treat their water because of several benefits: germicidal potency, sustained residual disinfection properties, taste and odor control, as well as it being cost-efficient. In the past few years and more recently with the signing of the Bioterrorism Act by President Bush, the federal government has increased the effort to keep this nation’s water supply safe. Disinfection of the public water supply should not be compromised.

　　Water suppliers are continually being challenged to prevent the presence of disease-causing microorganisms in their water systems and methods of treatment vary depending on site-specific factors, as well as the quality of the raw water supply. The importance of water disinfection is evidenced by the fact that most past cases of outbreaks of waterborne diseases were due to inadequate disinfection or no disinfection at all. Alternatives to the use of chlorine have received increased interest because concerns over the formation of disinfection byproducts (DBPs) have emerged; however, most of these alternatives (i.e., chloramine, chlorine dioxide and ozone) also produce DBPs. Less is known about the DBPs formed by some of the alternatives, and the risks using these technologies may be equivalent or higher. Chlorine is still the most common drinking water disinfectant used today and the one we have the most information about. On balance, the health risks of not chlorinating water appear to be greater than risks associated with DBPs.

　　Emerging national security issues, along with having to comply with other federal regulations such as EPA’s Risk Management Plan and OSHA’s Process Safety Management, have pushed the water and wastewater treatment industry to look for alternatives. Alternatives like ozone, UV irradiation and chlorine dioxide have been used. Although these other processes do provide efficient disinfection capabilities, each alternative has associated disadvantages. Ozone and UV irradiation do not provide a persistent residual disinfection capability and have relatively high operating and maintenance costs associated with them. Chlorine dioxide forms organic byproducts and requires onsite generation equipment and the handling of several chemicals.