Pollution Status of Cyanuric Acid and Its Influence on Disinfection Effect

Pollution status: my country has not yet conducted extensive surveys on the concentration of cyanuric acid in swimming pool water, but some foreign surveys have shown that the content of cyanuric acid in swimming pool water may exceed the standard. For example, Sandel's survey found that the average value of cyanuric acid in water is 75.9mg/L, and the highest value can be as high as 406mg/L. Rakestraw's survey showed that more than 25% (122/486) of swimming pools contained cyanuric acid greater than 100mg/L, even as high as 140mg/L, and the highest concentration could reach 500mg/L. Therefore, there is a possibility that the excessive dosage of disinfectant in swimming pool water in our country will increase the content of cyanuric acid. Impact on disinfection effect: During the disinfection process, cyanuric acid will gradually accumulate and increase with the consumption of hypochlorous acid. When its concentration is high enough, it will inhibit the production of hypochlorous acid. However, it cannot produce enough free chlorine and cannot exert its disinfection effect. This is called the 'chlorine lock' phenomenon of cyanuric acid. Anderson et al simulated different concentrations of residual chlorine (0.25, 0.50 and 1.00 mg/L) in the laboratory under different cyanuric acid levels (0, 25, 50 and 100 mg/L) in the actual swimming pool. For the bactericidal effect of coccus, at a constant temperature of 20°C and a pH of 7.0 and 9.0, it is believed that the concentration of cyanuric acid (25-30) mg/L can stabilize residual chlorine, but in the case of high concentrations of chlorine, cyanuric acid The higher the concentration of uric acid, the higher the concentration of chlorine required to achieve the same disinfection effect. Cyanuric acid is considered to be a disinfection by-product produced during the use of disinfectants. Generally speaking, its toxicity is low. Within 24 hours after human ingestion, more than 98% of cyanuric acid is directly excreted from urine without metabolism. Taking advantage of this feature, the intake parameters of swimming pool water for swimming pools can be obtained by measuring the concentration of cyanuric acid in urine samples of swimming pools and swimming pools when carrying out health risk assessment. However, the latest research by Sinclair et al. found that the metabolic capacity of cyanuric acid varies greatly among different groups of people. About 25% of individuals excrete less than 80% of their intake dose within 24 hours. Using cyanuric acid as an evaluation indicator will underestimate Crowd intake of swimming pool water.