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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.

A B S T R A C TBy coupling the intermittent characteristics of rural sewage discharge and solar energy density, the performance responses of lab-scale tidal flow constructed wetland (TF) and conventional vertical flow constructed wetland (VF) to different organic loading rates (OLRs) (166.3, 300.9, 451.2, 602.4, and 751.2 g/m 2 d) in synthetic domestic sewage treatment were investigated to study its feasibility to replace conventional aeration and reduce the dependence of wastewater treatment plants on the grid in this study. Artificial aeration was conducted based on simulating photovoltaic aeration. The increase in OLR promoted the removal performances for the chemical oxygen demand (COD) and ammonia-nitrogen (NH þ 4 -N) in TF, which could be up to 95.7 and 97.2%, respectively, under OLR of 751.2 g/m 2 d. Excess organic carbons inhibited NH þ 4 -N removal through competition for oxygen available in VF, where the COD removal efficiency could be 89.6% while low NH þ 4 -N removal (40%) was obtained under OLR 751.2 g/m 2 d. With the increase in OLR, the removal of total nitrogen (TN) was enhanced. A higher OLR can not only provide enough electron donors but also produce more anoxic regions for denitrification. The best TN removal was 77.5% in TF and 49.8% in VF, which occurred at OLR of 751.2 and 602.4 g/m 2 d, respectively. A drop of TN removal in VF was attributed to the lack of nitrate-nitrogen (NO À 3 -N) when reaching OLR of 751.2 g/m 2 d. The removal efficiency for total phosphorus was increased gradually with the increase in OLR. This paper suggests that appropriate control of OLR can achieve the optimal effect of pollutants removal, especially the elimination of TN.

Soil trench system is an important way to phosphorus and nitrogen removal by the combination of physical, chemical and biological degradation processes. The specific surface, osmosis, saturation water holdup, cost adsorption and desorption capacity of four fillings (red soil, sand, coal fly-ash and carbonized rice hull) in soil trench system were analyzed. Taking the removal effect, useful time, construction cost and clogging problem into consideration, the mode of the quantity of four fillings in soil trench system should follow"red soil>coal fly-ash>carbonized rice hull>sand". Keywords-soil trench; red soil ; sand; coal fly-ash; carbonized rice hull -2008ZX07105-002 4515 978-1-4577-0290-7/11/$26.00 ©2011 IEEE

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