Case Studies/White Papers

CHLORINE DISINFECTION APPROACHES

Gaseous chlorine has been a historical disinfection choice for municipal potable water and wastewater systems due to its low commodity cost. However, the hazardous status of chlorine gas adds to its overall cost to account for transportation, storage, and handling. The safety precautions and risks, coupled with recent concerns with respect to terrorism, are leading facilities to consider alternative disinfection methods.

Liquid chlorine, commonly referred to as bleach, is also a common disinfectant and is manufactured at a concentration of approximately 12.5%, for industrial uses, but is typically guaranteed at 10% due to decomposition by the time the product is deployed. Bleach carries a much lower risk than handling and dispensing chlorine gas. However, concentrated sodium hypochlorite is also classified as a hazardous chemical and adds additional cost for the handling, transportation, and storage. Volatile demand for bleach, and rising transportation costs, and degradation over time during storage when combined with instability in supply are leading to a renewed interest in yet another alternative disinfection method.

Solid chlorine, referred to as calcium hypochlorite or HTH, while stable when stored in a sealed container, presents significant hazards and cost in the process of solubilizing to liquid form for dispensing. In general, solid chlorine has a higher cost than liquid chlorine and presents the same subsequent hazards and costs for application as liquid chlorine.

On-site hypochlorite generation has been available for many years. On-site generation (OSG) is the solution to improving cost, safety, supply stability, and personnel risk. With OSG, salt water is converted to sodium hypochlorite at an output concentration that is generally regarded as safe and non-hazardous, i.e., the product is less than 1% sodium hypochlorite.