Effects of suspended bacteria on biofouling in recirculating water at different nutrient levels

Biofouling is a common but serious problem in recirculating cooling water systems. It damages equipments through biocorrosion, and causes clogging and increased energy consumption through decreased heat transfer. It is well known that the biofouling is mainly caused by deposits and growth of suspended bacteria in recirculating cooling water. Furthermore, the quality of cooling water, which would fluctuate within a certain range according to the conditions of makeup water, was also a major factor determining the nature of biofouling. So this research aims to examine the influences of suspended bacteria on biofouling at three different COD concentrations of 25, 50 and 100 mg/L. It was found that there existed a heterogeneous relation between adherent biofouling and suspended bacteria at different nutrient levels. The growth processes and competitions between attached and suspended bacteria varied greatly even at the same amount of suspended bacteria, which indicated that both suspended bacteria and nutrient levels should be concerned when inhibiting biofouling development.