A high efficiency biological system for treatment of coal gasification wastewater – a key in-depth technological research

Abstract

Coal is the main energy resource in China, hence pollution caused by coal gasification wastewater has been severe for decades. A three stage system was adopted to treat coal gasification wastewater; anaerobic hydrolysis acidification (333 days), aerobic oxidation (300 days), and ozonation–aerobic fluidized bed process (220 days) with the lowest HRT of 45 h. After more than a year of trials, high efficiency and stability of the treatment process has been achieved and the results showed that with an average influent (COD 4400 mg L⁻¹, total phenol 950 mg L⁻¹, volatile phenol 530 mg L⁻¹, NH₄⁺–N 300 mg L⁻¹, volatile acids 120 mg L⁻¹ and high chromaticity color blow 1000 times), the effluent COD could decrease to <60 mg L⁻¹, and total phenol, volatile phenol, NH₄⁺–N, and volatile acids were not detected, and for the chromaticity, the higher color removal reached to 10 times showed an average removal efficiency of COD, total phenol, volatile phenol, NH₄⁺–N and volatile acids of 96%, 99.9%, 99.9%, 99.9% and 99.9%, respectively. The pollutants removed were converted to biogas; organic transformations in the system were analysed by GC/MS equipment. The power consumption and the amount of sewage sludge were reduced by 30%. The wastewater treatment cost is 0.135 $ per m³. This study can be used to build a test to simulate future engineering applications of small scale technology platforms as it is a short, simple processing unit, with low energy consumption, low sludge production and easy management and maintenance.