THE DESIGN OF DISINFECTION CONTACT TANKS

The basic concept of chemical reaction engineering, as applied to the disinfection of water in a continuous flowing system, is summarized, and the effect of flow dispersion (i.e. the spread of residence time) on the efficiency of the process is highlighted. It is shown that deficiencies compared with the ideal batchwise situation can be offset by adjustments to the residence time or the disinfectant concentration, provided that the design is reasonable. The term 'compensation factor' is offered as a means of characterizing tanks which are intended for a specific duty. Reference is also made to recently available software which now enables tanks to be evaluated at the design stage without resorting to specialist computing services.