Study on Caffeine Wastewater Treatment by Combined Process of Micro-Electrolysis and SBR

Considering the characteristics of caffeine wastewater including high concentrations of organics and nitrogen, poor biodegradability and dull color, micro-electrolysis combined with SBR process were applied to treat caffeine wastewater and the effects and mechanisms of treatments were studied. The results showed that using micro-electrolysis to pretreat caffeine wastewater, removal rate of COD was up to 46.8%, ammonia nitrogen 62.6%, chrome 93.5%. Then using the SBR process to treat the wastewater after micro-electrolysis, the effluent concentrations of COD, NO₂^- and NO^3- were 203 mg·L^-1, 5.2 mg·L^-1, 10.6 mg·L^-1, respectively. The removal rates of COD, NO₂^- and NO₃^- reached 89.9%, 99.8% and 93.1%. Using GC-MS to detect the changes of organic compounds in influent and effluent of micro-electrolysis, it was seen that the major pollutants in caffeine wastewater were difficult biodegradable nitrogen-containing heterocyclic compounds. Through the micro-electrolysis treatment, the macromolecules of nitrogen- containing heterocyclic compounds open bonds, break rings and generate easily biodegradable micromolecules such as amide and urea.