Evaluation of Disinfectant action on Biofilm Bacteria

The control of potentially pathogenic bacteria in aquatic environments is of paramount importance. In the present study the effect of three disinfectants(concentration versus time)-phenol, formaldehyde, and Domex on bacteria in multispecies biofilm (MSB), single species biofilm of E.coli, Enterococcus spp., klebsiella spp., Pseudomonas spp.and Staphylococcus aureus and stable multispecies biofilm with E.coli, Enterococcus spp., klebsiella spp., Pseudomonas spp. and Staphylococcus aureus as indicators was determined by viable count method. There is a correlation between concentration of disinfectant and time. Initially with higher concentrations being more effective at 10 min. to 30 min. contact but at longer contact time of 60 min. to 120 min. the rate of killing is independent of concentration. Domex was found to be the most effective disinfectant especially against potentially pathogenic bacteria in biofilms. Enterococcus spp. was most susceptible to chlorine-at a concentration of 1 mg/l; while E. coli was most resistant requiring 30 min. to control in SSB and60 min. to control E.coli in multispecies biofilm. Similarly Staphylococcus aureus demonstrated highest resistance to phenol; Klebsialla spp. showed highest resistance to sodium hydroxide while the bacteria in single species biofilm (SSB) exhibited higher resistance to formaldehyde.