Are there any mandatory standards for COD in industrial circulating water and cooling water?
Thread Content
Relevant books state that COD should not exceed 5 mg/l, but this is impossible to achieve in most chemical industries; the 2007 edition of the design standards specifies that COD should not exceed 100 mg/l. I would like to ask everyone: if the COD leakage from the system is above 100 mg/l, can the biological sludge in the circulating water still be effectively controlled? The method for using fungicides is as follows: chlorine is applied daily, and in addition, powdered hypochlorite is used in an impact-based manner; at the same time, isothiazol and 1227 are also added. Will this work?
Control indicators: COD (manganese method) ≤ 15 mg/l, COD (chromium method) ≤ 120 mg/l. 1. If COD is determined using the manganese method, and the COD leakage from the system exceeds 100 mg/l, the biological sludge in the circulating water has already exceeded the allowable levels. If the leaking heat exchanger is not removed, it will be very difficult to control the water quality. 2. If COD is determined using the chromium method and the system leakage of COD exceeds 100 mg/l, the biological sludge in the circulating water can be used to control it. Using daily chlorine addition, along with the shock application of powdered hypochlorite, and additionally incorporating isothiazolinone and 1227, is a viable approach.
I think the difference between oxygen consumption and CODCr isn’t as large as 15 and 120
Try to keep the COD as low as possible; if the COD is high, chemical dosing can be used for control, and this can be verified through practical testing. Of course, it's step by step.
The Water Quality Standard for Circulating Water (GB50050-2007) specifies that this value should be less than 100. Here, COD mainly affects the growth of algae in the system; if algae are well controlled, COD has little impact on the system. However, SS has a significant effect on scale prevention and corrosion inhibition in the system.