On the utilization of wastewater from resin column regeneration

1. The wastewater from the resin tower is sent to the desalination system for recovery； 2. During normal production, the amounts of acidic water and alkaline water are roughly equal, and the pH of the wastewater remains stable ； 3. The impurities in wastewater are present in the salts, and can be removed during the purification process of the salt water ； 4. The content of calcium and magnesium may also be relatively low; all other heavy metal ions can be removed ； 5. Therefore, the wastewater from the resin tower can be recycled, and it is currently performing well.

In our company, the acid and alkali wastewater after regeneration is neutralized and then discharged to the sewage treatment plant for further processing before being released. I don’t think there’s much value in recovering it for use in salt production; instead, the regenerated acid and alkali wastewater should be used separately for adding acid and alkali in the dechlorination process, thereby making use of their value.

Our company neutralizes the wastewater generated from resin tower regeneration, then discharges it to a wastewater treatment plant for processing before making comprehensive use of it. There is little economic value in using the wastewater generated from resin tower regeneration directly in the brine; the high-valent metal ions released through hydrochloric acid desorption increase the amount of brine that needs to be treated, which is not beneficial for maintaining stable production. It is better to discharge this wastewater to a sewage treatment plant for processing before reusing it, as modern sewage treatment systems are now capable of achieving zero emissions.

It is still better to neutralize the wastewater generated during the regeneration of the resin tower before discharging it to the sewage treatment plant. From a long-term perspective, the cost of recycling this wastewater is not worthwhile; moreover, the heavy metals that are extracted end up back in the brine system, which is not beneficial for the resin tower over time!

　　The wastewater generated during the regeneration of resin towers can be utilized comprehensively. The main heavy metal ions involved are divalent cations such as calcium, magnesium, strontium, barium, lead, and nickel; these ions can be removed during the purification of brine. For more information, see: Solubility products of common cations and anions in ion-exchange membrane brine: http://bbs.hcbbs.com/viewthread.php?tid=116809. As for discharging this wastewater, it is puzzling – there have always been problems with the treatment of saline wastewater, so the only option seems to be to dispose of it.

Our design involves separating acidic wastewater from alkaline wastewater; acidic wastewater contains high levels of ions such as calcium and magnesium, which are discharged, while alkaline wastewater is recycled

It is possible to neutralize the two and then carry out chemical salt treatment; however, if the concentration is too low, it may affect the water balance. If there is alkali in the form of a membrane, it can also be used for neutralization followed by chemical salt treatment using the membrane method.

If it is underground salt, then after one round of brine purification, when its concentration is kept very low, it has little impact on the stability of the entire system. As the saying goes, \"too many fleas don’t cause itching\"; the amount of heavy metal ions in such underground salt is practically negligible. Moreover, these ions precipitate out during the brine purification process, so there is no risk of accumulation. This post was last edited by limingshuguang on 2008-1-2 at 14:14.]

Regarding the recycling of acid and alkali regeneration wastewater, after extensive research, our company has developed effective methods for recovering these acids and alkalis; however, the economic value of such recovery is not high. I’m not sure what the volume of wastewater in your company is, nor how much refined raw salt and finished products are produced there

Our factory’s design involves directing the acid regeneration waste, alkali regeneration waste, as well as the wastewater from the second and third washing steps into a wastewater tank. From there, it is sent to a wastewater treatment plant for processing, before being returned to the brine mixing tank for use in salt production. This approach allows for the recycling of some water, without having a significant impact on the quality of the brine.

Alkaline wastewater can be used to add alkali in dechlorination systems, while acidic wastewater cannot be returned to the brine system due to its high calcium and magnesium content; it should instead be sent back to the primary brine, thereby adding a burden to that system. It is more appropriate to use it for wastewater treatment (to adjust the pH value).

The regeneration wastewater from our resin towers is adjusted in pH, then sent for wastewater treatment and reuse; it is subsequently mixed with raw water in a certain proportion to replenish the circulating water system

For resin regeneration wastewater, nanofiltration machines can be used to separately purify and recover acids and bases. It can generate significant economic value and environmental benefits. Generally, recycled 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 macromolecular 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 process. The purified weak alkaline solution can also be reused for the next regeneration by simply adding some liquid alkali to it.