03-09: One Company's Legionella Standard

Following issuance of Legionella guidelines by CTI, Shell Chemical Company (SCC) upgraded procedures for control of Legionella in its water systems. A Standard was developed which addresses all water systems. This paper will focus on SCC standards and guidelines for cooling towers. The Standard is more prescriptive than the CTI guideline and represents a compilation of regulations and guidelines in the literature. It requires a Health Risk Assessment (HRA) and development of a plan to address risk areas, outlines minimum standards, and provides examples of how to meet the standards. For towers, Legionella testing is required and chlorine residual control ranges are specified.