Membrane combination technic on treatment and reuse of high ammonia and salts wastewater in rare earth manufacture process

Abstract

With the rapid development of rare earth industry in China, high NH 3-N and high salts wastewater generated in rare earth manufacture process had caused serious environment pollution especially for surrounding water body. Traditional treatment processes were either incapable of reducing pollutants concentration to the levels regulated by law or prohibitively expensive and difficult to operate. In this paper, a hybrid process which integrated air stripping pretreatment and low pressure reverse osmosis (LPRO) was proposed to treat this wastewater containing high ammonia and salt. Mechanism of treatment and remediation of ammonia and salt polluted water body was investigated. Influences of temperature, pH, and air stripping time on removal ratio of ammonia efficiencies were also discussed. Relationship among trans-membrane pressure drop (Δ P), additions ratio, stability of membrane and the possibility of water reuse were studied. The results showed that removal ratio of ammonia after LPRO desalination process could reach up to 98%, fluoride amounted to more than 99% and desalt efficiencies reached up to 95%, and stripped gas ammonia could be effectively recovered. Water quality had been improved significantly to meet reuse or discharge standards.