[Current status of bath water treatment techniques]

The Federal German DIN standard No. 19644 that has been enforced in West Germany since 1989 had to be revised in view of the fact that German legislation is expected to issue an ordinance on swimming pool and public bath water within the framework of the Federal Communicable Diseases Act; furthermore, the need for revision also arose from the solution of the hygienic problems of treatment and disinfection of warm whirlpool water, and from the necessity of modifying several now outdated regulations. It is the aim of public health legislation to prevent health risks of bathers and of attendant staff by Legionella pneumophila in all types of basins with additional water cycles and intake of air (aerosol formation); likewise, adverse health effects of side reaction products of the disinfectant chlorine (i. e. chloroamines and halogenated organic compounds, especially the trihalomethanes) must be avoided. Recent research has shown that these aims can be achieved by altering the mode of running and backwashing filters of all process combinations including those using ozone and introducing an additional absorption on powdered activated carbon, and the process combination of flocculation-filtration-chlorination. Improved treatment would be without effect if turnover rates could not be assessed reliably for basins of irregular geometry--as they are preferably used today--operated with additional water cycles involving intake of air. Lack of costly investigations prompts users to estimate turnover rates on the basis of experience collected with basins of square or rectangular dimensions.