Abstract
Treatment of reverse osmosis concentrate (ROC) has been complicated in terms of feasibility, cost, and most importantly, efficiency in removing contaminants. While adsorbents such as activated carbon, coal, and fly ash can remove organics, they may not be effective in removing nutrient salts that cause algae growth. Moreover, with regards to physical treatment, removing contaminants using adsorbents may not be appropriate, as toxic and non-biodegradable pollutants are not transformed or degraded into non-toxic forms. In this study, a series of processes involving adsorption using activated carbon and oxidation by hydroxyl and sulfate radicals were assessed as a means of treating ROC. The method includes treating water containing organics with an adsorbent, and adding nano-sized zero-valent iron (nZVI) to the water in the presence of oxygen, followed by the addition of persulfate, where the water is oxidized with reactive oxygen species (e.g., hydroxyl radical, peroxide, superoxide anion) produced by the addition of ZVI and persulfate radicals generated from persulfate activated by the addition of nZVI. Removal of non-biodegradable organics (as well as nitrogen and phosphorous) and nutrient salts not readily removed by conventional treatment methods can be effectively accomplished through the physical removal method described, using activated carbon, and by a chemical removal method using radical oxidation.
