The feasibility of using combined TiO2 photocatalysis oxidation and MBBR process for advanced treatment of biologically pretreated coal gasification wastewater

The study examined the feasibility of using combined heterogeneous photocatalysis oxidation (HPO) and moving bed biofilm reactor (MBBR) process for advanced treatment of biologically pretreated coal gasification wastewater (CGW). The results indicated that the TOC removal efficiency was significantly improved in HPO. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that the HPO could be employed to eliminate bio-refractory and toxic compounds. Meanwhile, the BOD5/COD of the raw wastewater was increased from 0.08 to 0.49. Furthermore, in the integration of TiO2 photocatalysis oxidation and MBBR process, the effluent of COD, BOD5, TOC, NH4+-N and TN were 22.1 mg/L, 1.1 mg/L, 11.8 mg/L, 4.1 mg/L and 13.7 mg/L, respectively, which all met class-I criteria of the Integrated Wastewater Discharge Standard (GB18918-2002, China). The total operating cost was 2.8 CNY/t. Therefore, there is great potential for the combined system in engineering applications as a final treatment for biologically pretreated CGW.