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Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped TiO2 was used to effectively decompose humic acids (HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of 500°C calcined 0.0010% Fe-Zn co-doped TiO2 with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the Ca 2+ or Mg 2+ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on TiO2 photocatalytic activities was CO3 2-> HCO3-> Cl-, but a slightly promotion was achieved when SO4 2was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the 500°C calcined 0.0010% Fe-Zn (3:2) co-doped TiO2. For tap water added with HAs, the UV254 and TOC removal rates were 57.2% and 49.9%, respectively. The UV254 removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the UV254, but not the TOC.

The ability of a new SBR (sequencing batch reactor) based on simulating photovoltaic aeration for maintaining nitrification activity under a 25-day starvation period was studied. The activity and abundance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) and the diversity of AOB were investigated. The measured biomass decay rates were 0.017 day(-1) and 0.029 day(-1) for AOB and NOB, respectively. These decay rates correlated well with AOB and NOB population quantified by real-time PCR. The recovery of ammonia oxidation rate and nitrite oxidation rate needed 4 and 7 days, respectively, indicating that NOB was more affected than AOB by starvation conditions. According to the real-time PCR results, Nitrospira was the dominant NOB in the reactor. Phylogenetic analysis indicated that Nitrosomonas oligotropha cluster was the dominant major cluster before and after starvation. Moreover, Pareto-Lorenz evenness distribution curves were plotted to interpret the interspecies abundance of AOB; the results suggested that AOB community possessed a balanced structure with medium Fo (Functional organization). Thus, the community can potentially deal with changing environmental conditions (e.g., starvation) and preserve its functionality according to the concept of functional redundancy.