Refereed Proceedings Heat Exchanger Fouling and Cleaning: Fundamentals and Applications Engineering Conferences International Year 2003 Biocide Dosing Strategies for Biofilm Control

In order to reduce environmental impact of biocide use for the control of biofilm formation in cooling water circuits, “environmentally friendly ” biocides have been developed, but they are generally more expensive than the more traditional chemicals. It is imperative therefore, that the minimum quantity of biocide is employed, so that costs are kept to a minimum. To achieve this objective optimum dosing strategies are required. Using apilot plant in conjunction with a monoculture of Pseudomonas fluorecsens as the biofouling bacterium, tests were carried out using a proprietary biocide, to investigate the effects of dose concentration, duration and frequency of dosing and fluid mechanics on biofilm control. With four 15 minute applications per day, at a peak concentration of 16.8 mg/l, it was not possible to inhibit biofilm development. Control was effected however, by doubling the peak concentration using a short dosing period. Concentration, as would be expected, was shown to be a critical factor for control. A boicide concentration below that for growth inhibition, seemed to enhance biofilm formation! Increase frequency of dosing is only effective if the concentration employed is biofilm growth inhibiting