Optimization of ozone disinfection and its effect on trihalomethanes

Abstract

Ozone is an attractive disinfection alternative to chlorine as chlorine has some environmental consequences due to its disinfection byproducts potential. In the present study ozone was used for the disinfection of secondary treated effluent of sewage treatment plant which is based on rotating biological contactor, process, Malaviya National Institute of Technology (Jaipur). From the experimental results it was found that ozone dose of 30mg/L was required to achieve WHO standards for Total Coliform Count (TCC) of 1000CFU/100mL for food crop irrigation and recreational impoundments. One factorial design method of response surface methodology (RSM) was used for statistically obtaining optimum ozone dose that satisfies the norms for COD and TCC simultaneously. The optimized ozone dose suggested by the model was 30mg/L to bring TCC within norms and the value of COD at this dose was 21mg/L. Experimental verification of the results was in good agreement with the predicted results of one factorial design. Analysis of scanned electron microscopy (SEM) images, shows the effect of ozone doses on bacterial cell membrane. Effect of ozone on four trihalomethanes was also studied using GC–MS/MS.