通讯机构：
[Wu, Xiaofu] C;Cent South Univ Forestry & Technol, Coll Environm Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
constructed wetland;multiple-cell system;pollutant transformation pathway;sewage treatment;sludge discharge;subtropical region
摘要：
A constructed wetland system, consisting of a surface-flow wetland cell connected in series with three vertical subsurface-flow wetland cells, was tested for treatment of domestic sewage from rural families in southern China. Diatomite, vermiculate, zeolite and hydrotalcite, were used, respectively, as filler adsorbents in the sequenced subsurface-flow cells for adsorption of organic, cationic and anionic pollutants. Selected trees, shrubs and annual herbs were planted to form a wetland plant community. The total treatment capacity, hydraulic loading rate and water retention time were 2 m3/d, 0.5 m/d and 48 h, respectively. Experimental data obtained from a year operation confirmed that the treatment process followed the dynamic pathway of pollutant transformation. The constructed system was effective to remove TSS, CODCr and BOD5 and their effluent concentrations met the first grade of the discharge standards legislated in China. The removal rates of TN, NH3-N and TP were relatively lower, and their effluent concentrations fell within the range between the first and second grade of the standards. An increase in initial pollutant loading and a decrease in temperature in winter caused apparent accumulation of TN, NH3-N and TP in the system. Discharge of sludge at adequate intervals was shown to be effective to enhance the treatment efficiency.
作者机构：
[吴晓芙; 纪智慧; 陈永华; 陈明利; 马群] College of Environment Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
通讯机构：
[Wu, X.] C;College of Environment Science and Engineering, Central South University of Forestry and Technology, Changsha, China
通讯机构：
[Wu, Xiaofu] C;Cent South Univ Forestry & Technol, Res Ctr Environm Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
vertical-flow constructed wetlands;plant intercropping model;warm seasonal plant model
摘要：
Subtropical climatic conditions can contribute to the death of the aerial parts of constructed wetland plants in winter. This presents a barrier to the widespread application of constructed wetland and is an issue that urgently needs to be solved. Three contrasting experiments, the plant-intercropping model (A), the warm-seasonal plant model (B), and the non-plant model (C), were studied in terms of their efficiency in removing pollutants, and the change in root structure of plants in the plant-intercropping model within the vertical-flow constructed wetlands. The results indicate that model A was able to solve the aforementioned problem. Overall, average removal rates of three pollutants (CODCr, total nitrogen (TN) and total phosphorous (TP)) using model A were significantly higher than those obtained using models B and C (P<0.01). Moreover, no significant differences in removal rates of the three pollutants were detected between A and B during the higher temperature part of the year (P > 0.05). Conversely, removal rates of the three pollutants were found to be significantly higher using model A than those observed using model B during the lower temperature part of the year (P<0.01). Furthermore, the morphologies and internal structures of plant roots further demonstrate that numerous white roots, whose distribution in soil was generally shallow, extend further under model A. The roots of these aquatic plants have an aerenchyma structure composed of parenchyma cells, therefore, roots of the cold-seasonal plants with major growth advantages used in A were capable of creating a more favorable vertical-flow constructed wetlands mediamicroenvironment. In conclusion, the plant-intercropping model (A) is more suitable for use in the cold environment experienced by constructed wetland during winter.
作者机构：
[Wu Xiaofu; Zhao Fang; Chen Mingli; Ji Zhihui; Ma Qun] Cent S Univ Forestry & Technol, Inst Environm Sci & Engn, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wu, XF ] ;Cent S Univ Forestry & Technol, Inst Environm Sci & Engn, Shaoshan S Rd, Changsha 410004, Hunan, Peoples R China.
摘要：
Adsorption experiments of Zn2+ and Cd2+ ions from aqueous solutions onto vermiculite were conducted to test the applicability of two basic functions derived for calculating the change in the Gibbs' free energy (ΔG0) and the chemical potential (Δμ) between the initial and equilibrium states in ion adsorption systems. The functions were deduced on the basis of the thermodynamic principle that the chemical potentials of the reactants and products of a physicochemical reaction should be equal in the equilibrium state and, consequently, the change in the Gibbs' free energy between the initial and equilibrium states of the reaction should be equal to the sum of the initial molar quantity of each reactant multiplied by its change in chemical potential. The results of the analysis conducted indicate that the two functions considered could well be used not only for calculating ΔG0 and Δμ but also for determining the adsorption capacity of an adsorbent under the conditions considered.
通讯机构：
Institute of Environment Science and Engineering, College of Resources and Environment, Central South University of Forestry and Technology, China
