Treatment of xanthine synthesis wastewater with chemical deposition-biotreatment technics

A scheme was designed for treating pharmaceutical waste water, which contained high concentration of chemical oxygen demand (COD) and SO₄^2-, and the impact of influent organic loads was also studied. SO₄^2- was removed by the chemical deposition techniques, and COD was then removed by the batch Anaerobic Hydrolysis-acidogenesis-Aerobic biotechnology which was performed under different influent organic loads adjusted by changing HRT and MLSS. The impact of influent organic loads was estimated by the removal loads and effluent COD. When the amounts of precipitators CaCl₂ and Na₂SO₄ were 13.64 g/L and 9.12 g/L respectively, the highest rate of SO₄^2- removal was about 60%, and about 95% SS and a little COD were removed at the same time. The pretreated wastewater was then treated by the Anaerobic-Aerobic biotechnology, and the remaining COD of aerobic effluence was less than 300 mg/L, the second class discharge standard of Sewage Comprehensive Discharging Standard GB 8978-1996. When the HRT, MLSS of anaerobic and aerobic units were 2 days and 1 day, 14.75-15.41 g/L and 9.45-9.98 g/L, the corresponding optimal influent biological load (COD), biological removal loads were 0.268 kg/(kg· d) and 0.246 kg/(kg·d), 0.045 kg/(kg·d) and 0.231 kg/(kg·d). The effluent quality would turn worse with the influent biological load increasing. It is suggested that the Chemical Deposition-Anaerobic Hydrolysis-acidification-Aerobicbiotechnology was an efficient method to treat such pharmaceutical wastewater.