| 摘要 |
A process for removing nitrate ions from a contaminated aqueous feed solution containing the same, and also chloride ion, by forcing the solution through a reverse osmosis membrane which permits passage of nitrate ions through the membrane and into the product water while rejecting chloride ion and other anions such as sulfate and bicarbonate, and concentrating such anions in the brine waste water. An anion exchange resin bed charged in the chloride form is placed in the product water during the reverse osmosis operation. Reverse osmosis product water containing nitrate is treated by the anion exchange resin bed to remove the nitrate ions and replace them with chloride ions. The resulting product water is essentially free of the nitrate impurity and a concentrated waste brine stream is obtained containing essentially chloride salts. In a preferred embodiment, when such anion exchange bed has exhausted the chloride ions and becomes loaded with nitrate ions, the resulting anion exchange resin charged with nitrate is placed in the concentrated waste brine stream to regenerate the anion exchange resin with an equivalent amount of chloride ion, liberating the nitrate ion in concentrated form into the waste brine concentrate stream from the reverse osmosis system. Thus, ionic impurities such as nitrate ion are concentrated in the waste brine solution. The same process will remove contaminant ions similar to nitrate such as arsenate, selenate and borate.
|
