Biofilm Development and Destruction
Final Report, EPRI-CS-1554. Rice University, Houston, Texas, (September 1980)DOI: 10.2172/7044527
Abstract
Fouling biofilm formation, its effects on energy losses and, finally, its destruction were studied. The project objectives included: developing a better understanding of fouling biofilm accumulation and factors affecting its rate; determining the effectiveness of fouling biofilm destruction by chemical oxidants; and developing a practical, reliable, sensitive device for monitoring biofouling. Special apparatus and simulated cooling water were used in the laboratory. A tubular reactor and an annular reactor consisting of a stationary outer cylinder and a rotating inner cylinder were used. Experiments and apparatus were designed to isolate the effects of biofouling from other processes such as corrosion or particulate fouling which could complicate data interpretation. Biofilm development rate is affected by fluid velocity, wall temperature, and nutrient concentration. Increase in fluid frictional resistance, resulting from biofilm formation, is a good indication of biofouling after the biofilm reaches a critical thickness corresponding to the viscous sublayer thickness. Changes in heat transfer are the net result of decrease in conductive heat transfer due to biofilm accumulation, and increase in convective heat transfer due to increase in fluid frictional resistance. Destruction of biofilms by chemical oxidants is a diffusion-limited process. Consequently, oxidants are more effective when applied at high concentration for short periods. High flow rates enhance biofilm destruction by oxidants. Several promising techniques for monitoring biofouling film development and destruction were developed and tested.