Using samarium (III) nitrate hexahydrate, manganese nitrate and citric acid as main raw materials, the SmMnO3 gel was prepared by sol-gel process. The gel was kept at 100 °C for 24 h to get the xerogel. Then, the xerogel was respectively calcined in muffle furnace at 600 °C, 700 °C, 800 °C and 900 °C. The structure and morphology of samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy. The UV photocatalytic activities of SmMnO3 were investigated by methyl orange which was used as simulated sewage. The results show that the pure SmMnO3 can be obtained through calcination between 700 °C and 800 °C, and the SmMnO3 have an average particle size of 80 nm. The SmMnO3 samples calcined at 700 °C and 800 °C show high photocatalytic activity for decomposition of methyl orange under UV-light irradiation. The SmMnO3 samples are consistent with first-order kinetics for the degradation of methyl orange. And the apparent rate constants are respectively k700 =0.01206 min-1and k800=0.01088 min-1.

Nitro oxide (NO) and Nitrous oxide (N2O) are inevitable intermediates of sulfide autotrophic denitrification (SAD) process, and have huge environmental hazard. This study investigated the produce mechanism and accumulation characteristic of NO and N2O in SAD process under different S/N ratios. The results showed that the lower S/N ratio, the higher NO accumulation. Which was due to the strong reducing effect of S2- and the electronic competition between nitrogen reductase. And under S/N ratio = 2, N2O level reached its peak, which was caused by electronic competition. When the S/N ratio = 1, although the electronic competition was more intense, the total amount of electrons was less, thus the N2O produced is lower than that produced when S/N=2. Microbial community analysis showed that Thiobacillus sp. (62.44%) was the predominant genus, and conducted the suldide-oxiding autotrophic denitrification process.

By using the GPS-X software, the enhanced phosphorus removal (EPR)process was simulated in this study. The comparisons among nitrogen and phosphorus removal efficiency of traditional A2/O process, University of Cape Town (UCT) process, Modified University of Cape Town (MUC) process and inverted A2/O process were conducted, in order to determine the best process under the same conditions of construction investment and running cost. The results showed that the simply reversed A2/O process exhibited poor total phosphorus (TP) removal efficiency under low carbon level. The effluent water qualities of the other three processes under low, medium and high levels of carbon source met the first B level criteria in Discharge Standard of Pollutants for Municipal Wastewater Plan (GB18918-2002) for China. The ranges of removal efficiencies of TP, TN, NH4 +-N and COD were 63.15% ∼ 94.91%, 55.38% ∼ 77.89%, 96.91% ∼ 97.70% and 90.89% ∼ 93.66%, respectively. Denitrifying phosphorus removal occurred in anoxic tank of EPR process. The phosphorus accumulation concentration was 6.91 mg/L, and the maximum phosphorus released in anaerobic tank was 24.01 mg/L, and the higher P release gave the EPR process a high P removal effiency. Except for the TN which met the first B level criteria (GB18918-2002), TP, NH4 +-N and COD met the first A level criteria GB18918-2002), above that, the process was feasible. Inverted A2/O process exhibited the highest nitrogen removal efficiency for its sufficient carbon source in anoxic tank.

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