High-rate biodegradation of 3- and 4-nitroaniline

A municipal wastewater biosludge was acclimated to the degradation of 4-nitroaniline (4-NA). The acclimation was achieved by using this compound as the sole source of nitrogen during the degradation of succinate as the sole source of carbon and energy. The acclimated bacteria were able to eliminate and mineralize 4-NA as the sole source of carbon and energy. However, in batch tests, the degradation process was somewhat instable and only occurred at comparatively low rates. A continuously operated miniaturized fixed-bed bioreactor was used in order to increase the degradation rates. It was inoculated with the acclimated bacteria and fed with 4-NA as the sole substrate. The system enabled high bioconversion efficiency, due to the development of a high biomass concentration of up to 5.45 g SS L-1. At input concentrations of 4-NA up to 4.5 mM and a hydraulic retention time of 3.5 hours a high degradation rate of 1.1 mmol 4-NA L-1 h-1 and 90 ... 95% DOC removal were achieved. Partial nitrification, also occurred. After gradual adaptation, the bacteria also degraded 3-NA and 4-NA simultaneously in this system. Additional batch tests showed, that 3-NA can serve as the sole source of carbon, nitrogen and energy.