Studies on the O3-initiated disinfection from Gram-positive bacteria Bacillus subtilis in aquatic systems.

The kinetics of inactivation of Gram-positive strain, Bacillus subtilis in aquatic systems was investigated as function ozone aeration duration under varied conditions. Oxygen flow was in situ enriched with ozone using ozoniser, with [O(3)] ranging from (0.3 - 9.8) x 10(-5) moles per liter of oxygen. The inactivation kinetics of B. subtilis followed pseudo-first-order kinetics with respect to microbe, under excess [O(3)] conditions. The disinfection kinetics had first order dependence on ozone concentration and the overall second-order rate constant was (7.54 +/- 1.37) x 10(3) M(-1) min(-1). The effect initial temperature and pH of the system on the ozone initiated inactivation of microbe was also explored. Relative to hydroxyl radicals, molecular ozone was found more effective in microbial inactivation. Appropriate mechanism for ozone initiated inactivation is proposed. Ozone aeration significantly decreased the BOD levels of natural and B. subtilis spiked waters.

Kinetics of inactivation of Pseudomonas aeruginosa in aqueous solutions by ozone aeration.

The effect of ozonation on the disinfection of Gram-negative strain, Pseudomonas aeruginosa was investigated as a function of time. Ozone was generated in situ using corona discharge method, with ozone concentrations ranging from (0.29-9.84) x 10(-5) moles L(-1). The microbial inactivation kinetics followed pseudo-first-order kinetics under excess concentration conditions of ozone. With over all second-order constant, k = (4.02 +/- 0.20) x 10(4) M(-1) min(-1), the reaction rate had first-order dependence both on the microbial count and ozone. The influence of temperature and pH on the ozone initiated disinfection of the microbe was also investigated. Molecular ozone is found more effective in disinfection than hydroxyl radicals. Probable mechanism for antimicrobial power of ozone in water systems is discussed. The ozone aeration decreased the biochemical oxygen demand (BOD) value of natural and microbe spiked waters significantly.