The excessive COD (Chemical Oxygen Demand) of evaporator condensate is a concern that directly affects the safety and environmental standards of water quality. The following is a detailed analysis of the problem of COD exceeding the standard in the condensate water of the evaporator and corresponding solutions.

          1. Reasons for Excessive COD in Evaporator Condensed Water

          1. Raw water quality:

          When the raw water contains organic components with low boiling points or boiling points similar to water, these organic compounds may partially or completely evaporate during the heating process and mix into the condensate, resulting in excessive COD in the condensate.

          When the COD of the raw water is high and the composition is complex, such as pharmaceutical wastewater, coating wastewater, etc., the residual concentration of COD in the evaporator condensate may also be higher.

          2. Working principle of evaporator:

          The evaporator vaporizes wastewater by heating it, and then condenses it to obtain distilled water. However, during the heating process, components with boiling points lower than the heating temperature (including organic compounds) may vaporize and condense into the condensate with water vapor.

          2、 Solution

          1. Optimize evaporator process:

          Choosing the appropriate type of evaporator, such as a low-temperature evaporator, whose lower operating temperature helps to reduce COD residue in condensed water.

          Improve the operating conditions of the evaporator, such as adjusting heating temperature, pressure, etc., to reduce the volatilization and condensation of organic matter.

          2. Deep treatment of condensate water:

          Select appropriate deep treatment processes based on the specific composition of COD in condensate water.

          Activated carbon adsorption: The cost is relatively moderate, but the consumption is high and the regeneration frequency is high. Suitable for situations where COD treatment requirements are not particularly high (<300mg/L).

          Reverse osmosis membrane separation: It has a good removal effect on some substances (>75%), but is affected by various factors such as pH. Can be used as a supplementary process after activated carbon adsorption.

          Biochemical treatment: suitable for situations with high COD residue and large water volume. By the degradation effect of microorganisms, COD in condensed water can be effectively reduced.

          When selecting advanced treatment processes, it is necessary to analyze the COD composition of condensed water to ensure treatment effectiveness.

          3. Strengthen raw water pretreatment:

          Add pre-treatment processes such as coagulation, sedimentation, and filtration before the evaporator to remove suspended solids, organic matter, and other impurities from the raw water.

          Adjusting the pH value of raw water to a suitable range for microbial growth can help improve the efficiency of subsequent biochemical treatment.

          4. Regular maintenance and management:

          Regularly clean and maintain the evaporator to prevent scaling and blockage inside the equipment.

          Monitor the COD and other indicators of condensate water, promptly identify and solve problems.

          The solution to the problem of COD exceeding the standard in evaporator condensate water needs to be approached from multiple aspects, including optimizing the evaporator process, deep treatment of condensate water, strengthening raw water pretreatment, and regular maintenance and management. By implementing these measures, the COD content of condensed water can be effectively reduced, ensuring the safety of water quality and meeting environmental standards.