Simultaneous purification of salt and condensate by collaborated evaporation-peroxodisulfate treatment of high salinity organic wastewater

High salinity organic wastewater is commonly treated by evaporation, which produces a large amount of waste salts and condensed water containing organic compounds. The waste salts are typical classified as hazardous waste and the condensed water often requires advanced oxidation treatment before it can be biochemically treated. In this study, a synergistic treatment process combining evaporation with thermal activation of peroxodisulfate (PDS) was developed for the treatment of wastewater containing tetrabromobisphenol S (TBBPS) and Na2SO4 to reduce the content of organics in the crystal salt and condensed water. Compared with evaporation alone, the synergistic treatment process allows the complete removal of TBBPS from the crystal salt with an increase of TOC removal from 4.48 % to 94.44 %. Meanwhile, in the condensed water, TBBPS can also be completely removed with a decrease of the average TOC content from 25.56 mg/L to 4.97 mg/L. EPR detection reveals that the dominant reactive species are center dot OH, SO4-center dot, and 1O2. Moreover, the presence of SO42- can enhance the conversion of center dot OH to SO4-center dot, thereby improving the utilization of reactive species by increasing the contribution of SO4-center dot. The degradation intermediates of TBBPS were detected by IC and LC-MS, based on which the possible degradation mechanism of TBBPS was proposed. The synergistic treatment process can not only promote the resource utilization of waste salt and reduce the difficulty of condensed water treatment but also improve the stability of the evaporation system.