Enhanced treatment of nitroaniline-containing wastewater by a membrane-aerated biofilm reactor: Simultaneous nitroaniline degradation and nitrogen removal

Nitroaniline (NA) is an aniline derivative with high toxicity, potential carcinogenicity and mutagenic effects. At present, the physical, chemical and biological methods used in NA-containing wastewater treatment usually suffer from problems such as low removal efficiency, high energy consumption and secondary pollution generation. In this study, a membrane-aerated biofilm reactor (MABR) was constructed to enhance the treatment of wastewater containing o-nitroaniline (2-NA) and p-nitroaniline (4-NA). The stratified biofilm and counter-diffusion of oxygen in the MABR were conducive to NA degradation. At a lower concentration, NA was primarily removed through direct oxidative degradation in the absence of the cometabolic substrate acetic acid, while at a higher concentration, NA was predominantly removed through oxidative degradation after reduction of NA in the presence of acetic acid. With an influent NA loading of 0.120 kg/(m(3).d), an aeration pressure of 40 kPa and an acetic acid dosing ratio of 2.0, the 2-NA and 4-NA removal loadings reached 0.058 and 0.060 kg/(m(3).d), respectively. Additionally, the chemical oxygen demand (COD) and total nitrogen (TN) removal rates were 82.40 and 88.52%, respectively. The MABR technology promoted simultaneous NA degradation and nitrogen removal from NA-containing wastewater treatment, illustrating its prospects for industrial application.