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A laboratory hot tub model for disinfectant efficacy evaluation
Darla M Goeres1, Linda R Loetterle, Martin A Hamilton
1Center for Biofilm Engineering, 366 EPS Building, Montana State University, Bozeman, MT 59717-3980, USA. darla_g@erc.montana.edu
Journal of Microbiological Methods
|September 5, 2006
Summary
A new laboratory hot tub (LHT) apparatus and standard operating procedure (SOP) reliably measure antimicrobial efficacy in hot tubs. The LHT system accurately quantifies bacterial reduction in water and on surfaces, proving sensitive to disinfectant levels.
Area of Science:
- Microbiology
- Environmental Engineering
- Public Health
Background:
- Recreational and therapeutic hot tubs can harbor significant bacterial contamination.
- Assessing the efficacy of disinfectants in complex hot tub environments is crucial for public health.
- Existing methods may not fully replicate the conditions found in operational hot tubs.
Purpose of the Study:
- To develop and validate a novel laboratory hot tub (LHT) apparatus and standard operating procedure (SOP).
- To quantitatively assess antimicrobial efficacy against planktonic and biofilm bacteria under simulated hot tub conditions.
- To establish a reliable testing model for evaluating disinfectants in hot tub water.
Main Methods:
- A novel Laboratory Hot Tub (LHT) apparatus was designed to mimic recreational hot tub parameters.
- Standard Operating Procedure (SOP) was established for consistent experimental conditions.
- Efficacy was measured using log reduction values against planktonic and biofilm bacteria.
- Sensitivity to chlorine and bromine concentrations was assessed.
- Ruggedness of the method was tested against variations in mixing, water chemistry, inoculum, and organic load.
Main Results:
- The LHT, without antimicrobial treatment, consistently supported bacterial growth (e.g., 7.2 log10 cfu ml-1 in bulk water).
- Chlorine treatment significantly increased log reduction values for planktonic and biofilm bacteria (p<0.05).
- The LHT system differentiated efficacy between chlorine and bromine, with chlorine showing greater reduction.
- The method demonstrated robustness against variations in key experimental parameters.
Conclusions:
- The LHT apparatus and SOP provide a reliable and reproducible method for evaluating antimicrobial efficacy in hot tubs.
- This model serves as a critical second tier in a multi-tiered testing strategy, bridging suspension tests and field trials.
- The findings support the development of effective disinfection strategies for maintaining safe hot tub water quality.
