Nitrobenzene degradation pathways and their interaction with sulfur and nitrogen transformations in horizontal subsurface flow constructed wetlands

• Intermittently aerated and un-aerated wetland were investigated to treat NB wastewater.
• Intermittent aeration enhanced buffer capacity of NB degradation to shock loading.
• NB degradation pathways in horizontal subsurface constructed wetlands were identified.
• Interaction of NB degradation with microbial mediated processes was assessed.

Nitrobenzene (NB) degradation pathways and their interaction with sulfur and nitrogen transformations in constructed wetlands are not fully understood. This study investigates the effectiveness of horizontal subsurface flow constructed wetlands (HSSFCWs) in NB biodegradation including the biodegradation pathways and microbial interactions. The investigation was based on two laboratory-scale wetlands planted with Juncus effusus. One wetland was intermittently aerated while the other was not. Data about NB degradation were collected at varying influent loading rates [35 and 140 mg/L] for 120-day period. From the results, both wetlands exhibited an overall performance of 99% NB removal. More so, intermittent aeration did not significantly improve overall performance but rather it enhanced the buffer capacity of NB degradation to shock influent loading. The result also demonstrates that NB mineralization account for about 96% and 4% for volatilization. Formation of ammonium from NB degradation increased the ammonium concentration in the pore water. In unaerated wetland, 84 mg/L of sulfide accumulated from complex microbial reaction involving sulfate as electron acceptor and NB as electron donor.

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