Removal of nitrogen by heterotrophic nitrification-aerobic denitrification of a novel halotolerant bacterium Pseudomonas mendocina TJPU04.

Excess inorganic nitrogen in water poses a severe threat to enviroment. Removal of inorganic nitrogen by heterotrophic nitrifying-aerobic denitrifying microorganism is supposed to be a promising and applicable technology only if the removal rate can be maintained sufficiently high in real wastewater under various conditions, such as high concentration of salt and wide range of different nitrogen concentrations. Here, a new heterotrophic nitrifying-aerobic denitrifying bacterium was isolated and named as Pseudomonas mendocina TJPU04, which removes NH4+-N, NO3--N and NO2--N with average rate of 4.69, 5.60, 4.99 mg/L/h, respectively. It also maintains high nitrogen removal efficiency over a wide range of nitrogen concentrations. When concentration of NH4+-N, NO3--N and NO2--N was up to 150, 150 and 50 mg/L, 98%, 93%, and 100% removal efficiency could be obtained, respectively, after 30-h incubation under sterile condition. When it was applied under non-sterile condition, the ammonia removal efficiency was slightly lower than that under sterile condition. However, the nitrate and nitrite removal efficiencies under non-sterile condition were significantly higher than those under sterile condition. Strain TJPU04 also showed efficient nitrogen removal performance in the presence of high concentration of salt and nitrogen. In addition, the removal efficiencies of NH4+-N, NO3--N and TN in real wastewater were 91%, 52%, and 75%, respectively. These results suggest that strain TJPU04 is a promising candidate for efficient removal of inorganic nitrogen in wastewater treatment.

Photocatalytic ozonation of organic pollutants in wastewater using a flowing through reactor.

Photocatalytic ozonation (PCO/O3) process is a promising technology for mineralizing refractory organics in wastewater. In this study, we described an efficient approach to improve the mass-transfer performance of PCO/O3 by using a helical photocatalytic module (HPM) in an annular UVC reactor. Under hydraulic retention time (HRT) of 19 min and influent phenol concentration of 33 mg/L (TOC 26 mg/L), TOC removal of 91.5% was obtained during a PCO/O3 process with HPM, while TOC removal was only 58.1% without HPM (UVC/O3). This flowing through reactor displayed good stability in a continuous test lasting 20 h. The electric energy required to reduce TOC by one order of magnitude per cubic meter of solution was calculated to be 10.23 kWh/(m3 order), which supported that the PCO/O3 process in this flowing through reactor was energy-efficient compared with other processes (24.30-68.75 kWh/(m3 order)). The steel-rolling wastewater after biological treatment was taken as a target. Under the HRT of 57 min and initial COD of 124 mg/L, COD in effluent dropped to 45.8 mg/L and met the discharge standard of pollutants for municipal wastewater treatment plant of China.