2. Materials and Methods
- Disinfection using chlorine gas (0.45 mg L−1 free chlorine in the pool water).
- pH adjustment (pH 7.0 in the pool water).
- Flocculant dosing approx. 0.05 mg L−1 Al as poly-aluminium chloride (PAC).
- Dual media filter (0.5 m sand depth, 0.7–1.2 mm grain size), (0.5 m anthracite depth, 1.4–2.5 mm grain size).
- Filtration velocity 35 m h−1.
3.1. The Gage–Bidwell Law of Dilution: Empirical Approach
3.2. The Gage–Bidwell Law of Dilution: Computational Approach
3.3. The Role of Filter Efficiency in Contaminant Removal
3.4. Application of the Gage–Bidwell Approach to Modelling the Peak Turbidity of Pool Water
- To establish the equilibrium turbidity likely to be achieved if a constant bathing load (in terms of numbers of bathers per hour) is maintained indefinitely.
- To establish the maximum turbidity likely to be achieved if a constant bathing load is sustained for a finite time that is too short for the equilibrium to be achieved.
3.4.1. Modelling the Maximum Turbidity Achievable If the Design Maximum Bathing Load for a Pool Is Sustained Indefinitely
3.4.2. Modelling the Maximum Turbidity Achievable If the Design Maximum Bathing Load for a Pool Is Sustained for a Finite Period
3.5. Modelling Observed Time Courses of NTU
3.6. Public Health Implications
- Prediction of the time it takes to achieve satisfactory removal of a contaminant (e.g., Cryptosporidium oocysts) following a single contamination event.
- Prediction of the maximum equilibrium concentration of a contaminant under conditions of a steady input of the contaminant (we considered the maximum turbidity achieved under conditions of a prolonged constant bathing load).
- Prediction of the amount of water that should be circulated per bather to ensure that water clarity remains excellent, even when there is a very prolonged period when bathers are entering the pool.
- Prediction of the peak turbidity likely to be achieved in practice from knowledge of the distribution of bathing load during the day.
- Depth ranging from 1–2 m (average depth 1.5 m).
- 4 m2 pool area allowed per bather at maximum bathing load following the UK guidelines , i.e., each bather occupies 6 m3 of water on average.
- 3 h water-turnover time.
- Average bathing time of 0.75 h.
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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|State||Cumulative Fraction of Pool Volume Removed||Average Concentration (C) in Pool Water after Mixing|
|Starting state||0||C = Co|
|After first container||1/3||C = (1 − 1/3) Co|
|After second container||2/3||C = (1 − 1/3) (1 − 1/3) Co|
|After third container||1||C = (1 − 1/3) (1 − 1/3) (1 − 1/3) Co|
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