Search results for: Dezhi Dai

Authors: Dan Qu, Dezhi Sun, Benhang Li

Abstract:

The removal of Nitenpyram from farmland runoff by an integrated eco-ditches and constructed wetland system was investigated in the case of different HRT. Experimental results show that the removal of COD, N and P was not influenced by the Nitenpyram. When the HRT was 2.5 d, 2 d, and 1 d, the Nitenpyram removal efficiency could reach 100%, 100% and 84%, respectively. The removal efficiency in the ecological ditches was about 38%-40% in the case of different HRT, while that in the constructed wetland was influenced by the HRT variation. The optimum HRT for Nitenpyram and pollutants removal was 2 d. The substrate zeolite with soil and hollow brick layer enabled higher Nitenpyram removal rates, probably due to the cooperative phenomenon of plant uptake and microbiological deterioration as well as the adsorption by the substrate.

Keywords: ecological ditch, vertical flow constructed wetland, hydraulic retention time, Nitenpyram

Procedia PDF Downloads 355

Authors: Dezhi Li, Peng Cui, Bo Zhang, Tengyuan Chang

Abstract:

In order to solve the housing problem for the low-income families, the construction of affordable housing is booming in China. However, due to various reasons, the service facilities and systems in the indemnificatory residential community meet many problems. This article established a Satisfaction Evaluation System of the Fundamental Public Services for Large-scale Indemnificatory Residential Community based on the national standards and local criteria and developed evaluation methods and processes. At last, in the case of Huagang project in Nanjing, the satisfaction of basic public service is calculated according to a survey of local residents.

Keywords: indemnificatory residential community, public services, satisfaction evaluation, structural equation modeling

Procedia PDF Downloads 323

Authors: Tiantian Gu, Dezhi Li, Mian Zhang, Ying Jiang

Abstract:

Considering the characteristics of residents’ participation in the governance of old community renewal (OCR), a theoretical model of the determinant of residents’ intention to participate in the governance of OCR has been built based on the theory of planned behavior. Seven old communities in Nanjing have been chosen as cases to conduct empirical analysis. The result indicates that participation attitude, subjective norm and perceived behavioral control have significant positive effects on residents’ intention to participate in the governance of the OCR. Recognition of the community, cognition of the OCR and perceived behavioral control have indirect positive effects on residents’ intention to participate in the OCR. In addition, the education level and the length of residence have positive effects on their participation intention, while the gender, age, and monthly income have little effect on it. The research result provides suggestions for the improvement of residents’ participation in the OCR.

Keywords: old community renewal, residents’ participation in governance, intention, theory of planned behavior

Procedia PDF Downloads 139

Authors: Yanni Chang, Dezhi Dai, Albert Y. Tong

Abstract:

Piecewise linear interface calculation (PLIC) schemes are widely used in the volume-of-fluid (VOF) method to capture interfaces in numerical simulations of multiphase flows. Dynamic overset meshes can be especially useful in applications involving component motions and complex geometric shapes. In the present study, the VOF value of an acceptor cell is evaluated in a geometric way that transfers the fraction field between the meshes precisely with reconstructed interfaces from the corresponding donor elements. The acceptor cell value is evaluated by using a weighted average of its donors for most of the overset interpolation schemes for continuous flow variables. The weighting factors are obtained by different algebraic methods. Unlike the continuous flow variables, the VOF equation is a step function near the interfaces, which ranges from zero to unity rapidly. A geometric interpolation scheme of the VOF field in overset meshes for the PLIC-VOF method has been proposed in the paper. It has been tested successfully in quadrilateral/hexahedral overset meshes by employing several VOF advection tests with imposed solenoidal velocity fields. The proposed algorithm has been shown to yield higher accuracy in mass conservation and interface reconstruction compared with three other algebraic ones.

Keywords: interpolation scheme, multiphase flows, overset meshes, PLIC-VOF method

Procedia PDF Downloads 127

Authors: Hongtao Zhu, Dezhi Sun

Abstract:

Nitrogen and phosphorus are essential nutrients for biomass growth. But excessive nitrogen and phosphorus can contribute to accelerated eutrophication of lakes and rivers. Constructed wetland is an efficient and eco-friendly wastewater treatment technology with low operating cost and low-energy consumption. Because of high affinity with ammonium ion, zeolite, as a common substrate, is applied in constructed wetlands worldwide. Another substrate seen commonly for constructed wetlands is steel slag, which has high contents of Ca, Al, or Fe, and possesses a strong affinity with phosphate. Due to the excellent ammonium removal ability of zeolite and phosphate removal ability of steel slag, they were considered to be combined in the substrate bed of a constructed wetland in order to enhance the simultaneous removal efficiencies of nitrogen and phosphorus. In our early tests, zeolite and steel slag were combined with each other in order to simultaneously achieve a high removal efficiency of ammonium-nitrogen and phosphate-phosphorus. However, compared with the results when only zeolite was used, the removal efficiency of ammonia was sharply decreased when zeolite and steel slag were used together. The main objective of this study was to establish an overview of the interaction of steel slag and zeolite on ammonium nitrogen removal. The CaO dissolution from slag, as well as the effects of influencing parameters (i.e. pH and Ca2+ concentration) on the ammonium adsorption onto zeolite, was systematically studied. Modeling results of Ca2+ and OH- release from slag indicated that pseudo-second order reaction had a better fitness than pseudo-first order reaction. Changing pH value from 7 to 12 would result in a drastic reduction of the ammonium adsorption capacity on zeolite, from the peak at pH7. High Ca2+ concentration in solution could also inhibit the adsorption of ammonium onto zeolite. The mechanism for steel slag inhibiting the ammonium adsorption capacity of zeolite includes: on one hand, OH- released from steel slag can react with ammonium ions to produce molecular form ammonia (NH3∙H2O), which would cause the dissociation of NH4+ from zeolite. On the other hand, Ca2+ could replace the NH4+ ions to adhere onto the surface of zeolite. An innovative substrate filling configuration that zeolite and steel slag are placed sequentially was proposed to eliminate the disadvantageous effects of steel slag. Experimental results showed that the novel filling configuration was superior to the other two contrast filling configurations in terms of ammonium removal.

Keywords: ammonium nitrogen, constructed wetlands, steel slag, zeolite

Procedia PDF Downloads 212