Residual chlorine cannot be detected in circulating water
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When 70 mg/L of trichloroisocyanuric acid was added to the circulating water on a daily basis, residual chlorine levels of around 0.03 could be detected only within the first hour after addition; thereafter, it became difficult to detect such levels. At first, it was thought that this was due to the slow dissolution of trichloroisocyanuric acid, so sodium hypochlorite at a concentration of 270 mg/L was used, but the situation remained the same. I’d like to ask experts how to deal with this?
Status of circulating water makeup and drainage; are there any material leaks in the system?
There is no material leakage, and the water replenishment and drainage are normal; approximately 10% of the current water volume is drained each day
The concentration of sodium hypochlorite added is quite high; it should be possible to detect it. It either gets diluted away or is expelled. Another reason is that the concentration becomes insufficient due to self-decomposition over time, or it could be an issue with the analysis.
The poster should test the total residual chlorine to determine whether there are any organic substances or reducing agents in the circulating water, which could cause the available chlorine to react with them and change its form.
A simpler method of verification is to take water samples from the circulating pool, add chemicals to them in proportion to the amount of water present, and then monitor the residual chlorine level to see the results. Possible reasons for undetectable residual chlorine: 1. Inaccurate monitoring ； 2. Decrease in concentration due to the loss of effectiveness of sodium hypochlorite ； 3. Insufficient amount of oxidizing bactericide added ； 4. Water quality deteriorates, requiring larger amounts of oxidizing disinfectants.
In addition to the points mentioned above, check whether there are any leaks in the system What about the COD of organic matter in water?