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Chen X.,Shanghai JiaoTong University | Chen X.,Ecosystems Center | He S.,Shanghai JiaoTong University | Zhang Y.,Shanghai East Sea Marine Engineering Survey and Design Institute | And 5 more authors.
Chemosphere | Year: 2015

Wetlands and ponds are frequently used to remove nitrate from effluents or runoffs. However, the efficiency of this approach is limited. Based on the assumption that introducing vertical mixing to water column plus carbon addition would benefit the diffusion across the sediment-water interface, we conducted simulation experiments to identify a method for enhancing nitrate removal. The results suggested that the sediment-water interface has a great potential for nitrate removal, and the potential can be activated after several days of acclimation. Adding additional carbon plus mixing significantly increases the nitrate removal capacity, and the removal of total nitrogen (TN) and nitrate-nitrogen (NO3 --N) is well fitted to a first-order reaction model. Adding Hydrilla verticillata debris as a carbon source increased nitrate removal, whereas adding Eichhornia crassipe decreased it. Adding ethanol plus mixing greatly improved the removal performance, with the removal rate of NO3 --N and TN reaching 15.0-16.5g m-2 d-1. The feasibility of this enhancement method was further confirmed with a wetland microcosm, and the NO3 --N removal rate maintained at 10.0-12.0g m-2 d-1 at a hydraulic loading rate of 0.5m d-1. © 2014 Elsevier Ltd.

Chen X.,Shanghai JiaoTong University | Huang X.,Shanghai East Sea Marine Engineering Survey and Design Institute | He S.,Shanghai JiaoTong University | Yu X.,Shanghai JiaoTong University | And 3 more authors.
Ecological Engineering | Year: 2013

Landscape ponds are vulnerable to eutrophication due to continuous pollutant load from surface run-off and excessive fish feeding. A combined recycling purification system consisting of an aquatic plant filter, bio-zeolite filter, bio-ceramic filter, gravel bed filter, and in situ algal control facility was built to solve this problem. The advantage of this system is its ability to preserve landscape pond water quality and control algal biomass without periodically refreshing water. A pilot-scale experiment was conducted within an artificial landscape pond. The results suggested that the system performed well in pollutant removal; the removal efficiencies for SS, TN, NH4 +-N, NO3 --N, NO2 --N, and PO4 3--P were all above 50% at hydraulic loading rate of 1.2m/d. The aquatic plant filter performed the best for SS, NH4 +-N and phosphorus removal. The bio-ceramic filter accounted for the primary COD removal. The gravel bed filter built for denitrophication eliminated 60.6% of TN load and 62.0% of NO3 --N load. When the purification system was stopped, the pond water quality deteriorated rapidly in six days. When the system resumed operation, COD, TP, TN immediately declined in the landscape area. Additionally, the purification system showed high efficiency in algal removal. To further understand the algal reduction mechanism, floating plants and the aerator were removed. In response, an increase of Chl-a was observed, suggesting that in situ treatment was an important supplement to the purification system. © 2013 Elsevier B.V.

Bian L.,China Academy of Engineering Physics | Song M.,South University of Science and Technology of China | Ma L.,South University of Science and Technology of China | Zhou T.,University of Science and Technology Beijing | Dai Q.,Shanghai East Sea Marine Engineering Survey and Design Institute
2010 4th International Conference on Bioinformatics and Biomedical Engineering, iCBBE 2010 | Year: 2010

The rutile TiO2, La/rutile TiO2 and Y/rutile TiO 2 were synthesized by one-step method, and the densities of states were investigated by ab initio method. Firstly, the result of ab initio calculation showed that the band gap of La/rutile TiO2 is less than that of Y/rutile TiO2 and rutile TiO2, and the crystal lattice energy of rare earths (La, Y)/rutile TiO2 are similar to each other. Secondly, the crystal structure and photocatalytic activity of La (Y)/rutile TiO2 are characterized by XRD, DRS, ζ potential and kinetics reaction of photocatalyzing methyl orange. In a word, the photocatalytic activity for degradation of methyl orange on 1.0wt% La/rutile TiO2 was better than those on Y/rutile TiO2 and rutile TiO2. © 2010 IEEE.

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