Bacterial Inactivation Studies in Shrimp Pond Water by using Different Disinfectant Agents.

Background: Aquaculture water plays an important role in the dissemination of antibiotic-resistant bacteria during harvest of shrimps. Mitigation of bacteria through discharge is essential to prevent dissemination downstream. Chemical disinfection of culture water is feasible compared to other methods of bacterial inactivation.
Objective: To study the effect of different disinfectant agent's viz., chlorine, Fenton's reagent, and hydrogen peroxide (H2O2) on inactivation of bacteria from shrimp pond water.
Methods: The water samples were subjected to treatment with various concentrations of chlorine (0.0, 1.0, 2.5, 5.0 and 10.0 mg L-1), Fenton's reagent (1:10 mM ratio of Fe2+:H2O2; 2:20, 3:30, 4:40, 5:50) and H2O2 (20, 30, 40 and 50 mM) for different time durations (5 min, 15 min, 30 min and 60 min).
Results: The results indicated that all the disinfecting agents inactivated both the total heterotrophic bacteria and tetracycline-resistant bacteria with increased concentrations and time. At the end of 60 min treatment with chlorination (2.5 mg Cl2 L-1), Fenton's reagent (2 mM Fe2+ + 20 mM H2O2) and H2O2 (50 mM H2O2), the total heterotrophic bacterial count in the water samples gradually decreased by 2.35, 2.65, and 1.38 log10 CFU mL-1, and tetracycline-resistant bacteria count reduced by 1.57, 1.66, and 1.43 log10 CFU mL-1, respectively from initial bacterial load.
Conclusions: The study revealed that disinfection agents can be successfully employed in the inactivation of antibiotic-resistant bacteria discharged through aquaculture water. Among three disinfection agents, Fenton's reagent has been found effective in inhibiting both heterotrophic bacteria and tetracycline-resistant bacteria from water samples.
Highlights: Bacterial inactivation studies were carried with Chlorination, Fenton's reagent, and Hydrogen peroxide. The highest decrease in HPC (2.65 log) and tetracycline-resistant bacterial (1.66 log) was noticed in the water samples treated with Fenton's reagent. The use of disinfection agents effectively mitigates antibiotic-resistant bacteria from aquaculture wastewater.
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