Removal of high chloride ions from wastewater
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I want to know how to remove chloride ions from wastewater, as the chloride ion concentration is between 15,000 and 20,000. What are the effects of some conventional methods, such as precipitation, ion exchange, and membrane filtration? What other effective methods are there?
With such high chloride levels, there is no need to consider using resin adsorption for ion exchange.
This problem is also quite troublesome; it would be best to find a chlorinated composite salt that can precipitate in order to solve it.
Chloride ions in wastewater are essentially insoluble. If environmental regulations require treatment, it depends on the volume and quality of water; for large volumes of water, reverse osmosis can be used for concentration followed by evaporation of the concentrated liquid to produce solid salts, while for smaller volumes, direct evaporation using MVR or multi-effect systems is sufficient. The investment and operating costs are basically unacceptable to anyone. It is best to handle this at the front end, by reducing the use of salt or by collecting the high-salt water separately, so as to prevent it from mixing with ordinary wastewater.
Analyze its sources systematically to see if it can be reduced, and then consider investment costs along with other methods
So high? What kind of water is this? Use evaporation crystallization
For this, the reverse osmosis concentrate stream can be considered； Treating chloride ions by evaporating concentrated water!
With such a high concentration, resin treatment is not practical; concentration and crystallization are the better options.
With a chloride ion concentration of 15,000–20,000 mg/L, it’s not very worthwhile to go straight to evaporation equipment; it’s better to use a high-pressure flat membrane system for concentration first. Such high-pressure diaphragm membranes can concentrate the salts to nearly 20%, after which multi-effect evaporation or MVR evaporation can be used for evaporation and crystallization, thus solving the problem
This chloride concentration isn’t high; what about other water quality parameters? For water treatment, diluted biochemicals can be used ； If the components in the wastewater are relatively simple, membrane processes such as electrodialysis or reverse osmosis can be considered; however, these processes require high water quality standards, and it is not appropriate to use them when the COD level is high.