Why are the COD levels of both the inlet and outlet water high in electrodialysis?
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Our company uses electrodialysis to treat *AO acid wastewater, which mainly contains ** and *AO acid. The temperature is 80 degrees Celsius; the COD level, as measured by the cadmium method, is 800 in the inlet water, and it remains at 700 in the outlet water. The conductivity at the outlet is 1 us/m. Can’t electrodialysis reduce the COD level? What could be the substances causing such high COD levels (**there are no bacteria, oil, or similar substances in the production process**)?
Similar problems have occurred in our company’s production as well, with a higher COD level of around 1000 (using the potassium dichromate method); the possibility of oil contamination has been ruled out.
It could be the effect of salts; some salts also contribute to COD
Now, electrodialysis technology has made great progress; especially since homogeneous membrane electrodialysis has been developed domestically, there is almost no difference in terms of application and technical development compared to imported membranes, and they can be used interchangeably!
The COD in water is primarily due to organic substances present in it; the electrodialysis process is intended to remove the conductive ions in water (which are mostly inorganic substances), so it has no significant effect on reducing COD. If reverse osmosis treatment is used, COD will decrease significantly.