How to effectively recycle the wastewater generated again from the secondary brine chelating resin column

Many companies have begun to recycle acids and bases; at the very least, they recycle them for use in the desalination of brine. Waste salts and acids can be used to adjust the pH in wastewater treatment, or added to dechlorination towers. Caustic soda can be utilized for handling hydrogen chloride, for preparing caustic solutions, for adjusting the pH of wastewater, and for adding alkali to dechlorination towers; it is also used in the production of VCM from PVC and in the acetylene production process to manufacture sodium hypochlorite. As for organic substances, they can be ignored; the brine entering the resin column contains no free chlorine, so is it still necessary to treat it after it exits the column?

We have many project examples related to the recovery of acids and bases from resin regeneration fluids. Base recovery poses no issues, but for acids, it depends on what type of acid it is and its concentration

We have recently started to make comprehensive use of the waste liquids generated during the resin tower regeneration process: the alkali wash liquid is used for preparing sodium hypochlorite, the acid wash liquid is used for chlorate decomposition, and the water from washing steps 2 and 3 is collected and combined to be used as a substitute for high-purity water in resin tower regeneration, thereby achieving zero emissions.

At present, all the wastewater after neutralization here is recycled and reused; it has been in use for several years now, and no significant effects seem to be present.

Are there companies that use separate tanks for recycling waste acids and wastes alkalis, which are then used for dechlorination?

The recycling of alkaline wastewater and the alkaline pure water from washing step 3 is not a problem. However, returning acidic wastewater to the primary brine seems to have an impact. It takes a lot of effort to remove metal ions from the resin tower; metals such as calcium, magnesium, strontium, barium, and iron are not a concern in this regard, but what about the others? Closed-loop cycle? By one-time sedimentation and filtration of saline mud?

This post was last edited by kuyeliu on 2018-8-25 at 12:45. For resin regeneration wastewater, nanofiltration units can be considered to separately purify and recover acids and bases. It can generate significant economic value and environmental benefits. Generally, recycled waste hydrochloric acid with a high concentration (greater than 1%) is collected and purified using nanofiltration to remove more than 95% of calcium, magnesium ions, pigments, and other large-molecule impurities, with a recovery rate of over 80%. It is also possible to collect recycled waste alkali solutions with a high concentration (greater than 1%), purify them using nanofiltration to remove more than 93% of macromolecular impurities such as pigments, with a recovery rate of over 80% as well. The purified dilute hydrochloric acid can be supplemented with some concentrated hydrochloric acid for use in the next regeneration. The purified weak alkaline solution can also be reused for the next regeneration by simply adding some liquid alkali to it. I saw on Baidu Wenku, at https://wenku.baidu.com/view/83a...d4b14e84243e54.html, that device rental services are offered. It can be used without any investment. But it seems there are requirements regarding the processing volume. It’s not very cost-effective when the quantity is too small. Excerpts are as follows: Application areas: 1. Purification and recovery of acidic and alkaline waste liquids resulting from resin regeneration in industries such as starch sugars, fructose syrup, oligosaccharides, sorbitol, xylose, and refined sugar. 2. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as amino acids, monosodium glutamate (glutamic acid), citric acid, and lactic acid. 3. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as fermentation broths, vitamins, and acarbose. 4. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as antibiotics, cephalosporins, penicillin, erythromycin, and streptomycin. 5. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as animal and plant extracts, stevioside, and ginkgo extract. 6. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as fruit juices, apple juice, and pear juice. 7. Purification and recovery of acidic and alkaline waste liquids from resin regeneration in industries such as metallurgy, rare metals, lithium, tantalum, tungsten, and gallium. 8. Purification and recovery of acidic and alkaline waste liquids resulting from the regeneration of chelating resins used in the chlor-alkali industry. Questions of interest: 1. Question: How much investment is required for a nanofiltration machine? Answer: The main equipment is invested by **** Company, and the property rights belong to **** Company. Your company needs to provide 4-6 acid and alkali storage tanks. A small equipment deposit is required, which will be refunded interest-free at the end of the rental period. 2. Question: What are the recycling costs? Answer: Apart from the storage tank, no investment is required; profits are generated through cooperation. For the first collaboration, after paying the equipment deposit, the lead time for custom orders is 4 months. Initially, it is based on the principle of splitting profits 50-50. Your company shall provide the water, electricity, gas, and space required for the operation of the nanofiltration unit. The nanofiltration elements required for the operation of the equipment, other consumables, and maintenance services are provided by **** Company. 3. Question: Will recycling increase other consumptions? Answer: There will be a small amount of water and electricity consumption. Approximately 5-10 kWh of electricity is consumed per ton of waste acid or alkali solution filtered, and 3-5 tons of deionized water are used for cleaning daily. A small amount of compressed air is used to control the pneumatic valves on the equipment. 4. Question: Will it cause pressure on wastewater treatment? Answer: Reduce the pressure on wastewater treatment. 80% of the acids and bases were recovered, thereby reducing the salt content resulting from the neutralization of acids and bases in water. The total COD level in the wastewater remains unchanged, and it is still discharged to the wastewater treatment plant. 5. Question: Will new pollutants be generated? Answer: It is a purely physical process that does not generate new pollutants. 10 kg of acid and 10 kg of alkali are required for cleaning every day. Cleaning should be intensified once a month, using 10 kg of specialized cleaning agent. Nothing other than the cleaning agent is added. 6. Question: Is there any odor? Answer: Fully enclosed operation. A small amount of the odor from the waste acids and alkalis that have entered evaporates. No new flavors are introduced. 7. Question: What is the required concentration of hydrochloric acid HCl in the water fed into the nanofiltration unit? Answer: The concentration of hydrochloric acid HCl in the waste acid liquid resulting from normal resin regeneration is 2-6%. The nano-filter elements in the equipment require a certain concentration of hydrochloric acid HCl