Enhanced anaerobic performance and SMD process in treatment of sulfate and organic S-rich TMBA manufacturing wastewater by micro-electric field-zero valent iron-UASB

This study focused on investigating reactor performance, simultaneous methanogeneis and denitrifiction (SMD) process for treatment of a sulfate plus organic sulfur - rich 3,4,5-Triethoxybenzaldehyde (TMBA) manufacturing wastewater with variable COD/TSO42- (total sulfate) ratio by micro-electric field- zero-valent-iron (ZVI) UASB for 390 days. The initial COD/TSO42- was set as 1.42, 0.9 and 0.5, respectively by manually introducing sulfate. The experimental results indicated that micro-electric field- zero-valent-iron UASB was an attractive integrated option for satisfactory COD removal, nitrate reduction and a reasonable methane yield rate even at COD/TSO42- as low as 0.9. Further declining the COD/TSO42- to 0.5 can result in a moderate inhibition of SMD process. The behavior of organic S release was not inhibited over the entire experimental period. Thus, surprisingly, sulfate concentration in the effluent was always higher than that in the influent. In comparison with sludge sample at Day-1, sludge at Day-390 was characterized with high abundant Tissierella Soehngenia, Anaerolinaceae and Brevundimonas diminuta, which played critical role in promising performance in COD abatement. The relatively low abundance of sulfate reducing bacteria (SRB) such as Desulfobulbus and Desulfomicrobium can explain the lower sulfate reduction efficiency in term of high concentration of sulfate plus released from organic S-rich compounds.