Effect of sodium hypochlorite (Clorox) and its mode of application on biofilm development

The use of biocide is an important method in the control of biofouling in industrial processes. The efficacy of the biocide is influenced by various factors such as the type, concentration and mode of application of the biocide. Studies were carried out using ‘Clorox’, which contains sodium hypochlorite, in controlling biofilm development in laboratory scale biofilm reactors. The reactors were operated at a 10‐day hydraulic retention time (HRT) at 28°C, with mixing at 500 rpm. The initial inoculum was obtained from a cooling tower, and growth was maintained using Characklis Medium (Trulear & Characklis, 1982). There appears to be an inverse relationship between biocide concentration and biofilm thickness. Applying the biocide in sub doses showed less of an effect in controlling the biofilm than application of biocide in one dose. Application of biocide at different phases of biofilm growth showed no significant difference. Temperatures of 38°C and above increase the effect of the biocide.