Bacterial survival and regrowth in drinking water systems

Area of Science:

• Environmental Microbiology
• Water Quality Management

Background:

• Chlorine is a common disinfectant in drinking water supplies.
• Monitoring microbial contamination and disinfectant residuals is crucial for public health.
• Previous studies suggest varying efficacy of chlorine against different bacteria.

Purpose of the Study:

• To investigate the correlation between chlorine residuals and microbial concentrations in IIT Kharagpur's water supply.
• To assess the impact of low-level chlorine residuals on bacterial growth.
• To explore the use of turbidity as a real-time indicator of bacterial growth in chlorinated water.

Main Methods:

• Weekly monitoring of free and total chlorine residuals and microbial counts (HPC, total coliforms, faecal coliforms).
• Statistical analysis to determine correlations between chlorine levels and bacterial densities.
• Bacterial growth studies in chlorinated drinking water using nutrient broth and turbidity measurements.

Main Results:

• No significant correlations were found between HPC, coliforms, and free or total chlorine residuals.
• Low levels of residual chlorine (0.01-0.41 mg/L free, 0.02-1.23 mg/L total) did not inhibit coliform survival or growth.
• Bacterial growth rate in simulated drinking water was 0.196 ± 0.049 1/h, with a correlation between cell density and turbidity established.

Conclusions:

• The studied low levels of residual chlorine are insufficient to control bacterial populations in the IITKgp water supply.
• Turbidity shows potential as a real-time tool for monitoring bacterial growth in chlorinated drinking water.
• Further research is needed to optimize chlorine disinfection strategies for effective microbial control.