Value of oxidation-reduction potential in determining microbial indicators in swimming pool water
Objective To explore the value of oxidation-reduction potential(ORP)in determining microbial indicators in swimming pool water.Methods A total of 468 water samples were collected from artificial swimming pools in Taiyuan city's competitive training venues,public swimming pools,school pools,and hotel pools between 2019 and 2022.Water quality was assessed based on the national new standard Hygiene Standards and Limits for Public Places(GB 37488-2019),including parameters like water temperature,cyanuric acid,turbidity,free residual chlorine,combined chlorine,ure-a,ORP,total bacterial count,and coliform bacteria,and the qualification rate of water samples from 2019 to 2022 was ana-lyzed.Bivariate correlation analysis was used to determine the association between physicochemical indicators and microbial detection indicators,and automatic linear modeling was employed to ascertain the significance of physicochemical indica-tors.Receiver operating characteristic(ROC)curves were plotted to evaluate the efficacy of physicochemical indicators in assessing total bacterial count qualification.Results There was a statistically significant difference in the qualification rates of water samples from 2019 to 2022(x2=9.289,P=0.026),with 2020 having a higher qualification rate than 2021 and 2022(x2=8.153,7.983;P＜0.05).In 2020,water tem-perature and ORP were negatively correlated with the total bac-terial count(r was-0.384,-0.729;P＜0.05),while turbidity,pH,and urea showed a positive correlation(r was 0.387,0.389,and 0.607;P＜0.05).In 2021,ORP was negatively correlated with the total bacterial count(r was-0.549,P＜0.05).In 2022,pH and ORP were negatively correlated with the total bacterial count(r was-0.178 and-0.502;P＜0.05),and urea was positively correlated(r=0.293,P＜0.05).ORP was the most significant in as-sessing the qualification of total bacterial counts,consistently exceeding 0.60 in importance.ORP showed some indication for qualitative judgment of water quality,as demonstrated by the ROC curve analysis.The optimal cutoff value for ORP was 655.500 mV,with a sensitivity of 0.509 and specificity of 0.864,and an area under the curve(AUC)of 0.756.Conclusion ORP is an effective indicator for evaluating the microorganisms in swimming pool water,and a higher ORP value is associated with a lower total bacterial count.ORP has important value in evaluating the water quality and microbi-al level of swimming pools.
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