Treatment of wastewater containing high chloride levels
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The pharmaceutical wastewater used in vitamin C production contains 25,000 mg/L of chlorides, with a flow rate of 3,200 tons per day. Experts, please advise on what methods can be used to treat or recover hydrochloric acid Thank you!
Are you saying that the chloride content in the wastewater is 2.5%, and that the chlorides exist in the form of hydrochloric acid? What are the levels of metal ions and other organic impurities in it? If the wastewater contains sodium chloride, it is about 4%. If you want to recover hydrochloric acid, that means electrolyzing saltwater. It is essentially a small chlor-alkali plant. Chlor-alkali plants require a salt concentration of over 26%, an organic amine content of less than 5 ppm, an ammonia content of less than 1 ppm, and a COD content of less than 50 ppm. There are also requirements regarding the sulfate concentration, while the levels of calcium, magnesium, and iron ions must be at the ppb level. With a water volume of 3,200 tons per day, this constitutes a small desalination plant and salt production facility. The concentration of saline requires the removal of mycelium and similar substances in advance, through conventional filtration, ultrafiltration, and reverse osmosis; multi-effect evaporation is then used when the concentration exceeds 7%. As a result of these efforts, the cost of treating one ton of wastewater is 40–50 yuan, while the benefit generated is only 8–12 yuan. I understand that the treatment you mentioned is aimed at bringing the COD levels within the acceptable range, but it does not deal with the salts present.
It’s a bit difficult, mainly in terms of processing costs; use reverse osmosis.