Control of microbial fouling in circular tubes with chlorine
Characklis, William G.
Master of Science
Microbial attachment to liquid-solid interfaces has detrimental effects in flow systems. Frictional resistance shows a pronounced increase due to microbial films and thus causes higher energy requirements for fluid transport. The objective for this study was to obtain basic information about attachment and growth of bacteria and destruction of existent slime layers on the walls of a tubular reactor. Results indicate that high pressure drops caused by film formation cannot be explained by the resultant decrease in tribe diameter. The microbial film is assumed to have a rippled surface and viscoelastic properties which explain large increases in frictional resistance. Friction factors are as much as three times as high as in the clean tube. Chlorine was used as a slimicide to prevent fouling and remove formed slime layers. Results indicate that chlorine effectively removes microbial films if added at relatively high concentration for a short period of time at least once a day or at low concentrations with continuous addition. Shock chlorination every other day was not sufficient to prevent extensive fouling between chlorinations. Chlorine utilization by the film was shown to be dependent on concentration of chlorine feed and flow rate suggesting that slime control efficiency could be improved by increasing flow rate during chlorination. Chlorine utilization rate was not dependent on film thickness. A computer model for microbial fouling was developed. Experimental data were used to test the validity of the model and good agreement was obtained.