Effect of carbon source on the denitrification in constructed wetlands

ESPC State Key Joint Laboratory, Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China.
Journal of Environmental Sciences (Impact Factor: 2). 01/2009; 21(8):1036-43. DOI: 10.1016/S1001-0742(08)62379-7
Source: PubMed

ABSTRACT The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source (glucose) can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 mg/L, the retention time was 24 h and 25 mg/L dissolved organic carbon (DOC) was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.

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Available from: Hong-Ying Hu, May 19, 2014
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    • "Thus, organic matter may supply dissolved organic carbon (DOC) to microbes. Lu et al. (2009) report that an additional carbon source (glucose) can remarkably improve the nitrate removal ability of a constructed wetland. They demonstrate that the nitrate removal rate can increase from 20% to more than 50% in summer Table 5 Comparison of denitrification rates in various created and natural wetlands. "
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    ABSTRACT: The creation and restoration of new wetlands to mitigate wetland losses is a newly developing sciencewhose success still needs to be assessed. This study focuses on the ecological restoration of a gravel-pit in the low valley of the Seine estuary (France). Restoration consisted in filling the gravel-pit usinga hydraulic technique with dredged sediments from the Seine river and covering it with alkaline peatfrom adjacent wet meadows. Our objectives were to survey the functions of recreated soil 3 years afterthe gravel-pit was filled and assess whether it regained typical wetland functionality and to determinewhich soil functioning parameters are the most efficient for assessing restoration success. To addressthese questions, an approach combining analyses of in situ and ex situ soil functioning was used. Thesurvey was conducted on recreated soil as compared to a control soil (i.e. soil before gravel extraction).Four topographic zones were sampled corresponding to 4 types of recreated soil functioning in terms ofwaterlogging conditions: Hemic Histosol without waterlogged periods, Hemic Histosol with temporarywaterlogged periods, Hemic Histosol with the longest waterlogged periods and Interstratified Histosolwithout waterlogged periods. Soil respiration and SIR results showed that large stocks of organic matterare maintained after 3 years of restoration and proved able to sequester C in recreated soils. 3 yearsafter restoration, nitrogen removal function measured through denitrification technique was restored inthe Hemic Histosol with the longest waterlogged periods. These results demonstrate that waterloggingregime maintain the C stock and accelerate the restoration of denitrification process.
    Ecological Engineering 08/2014; 71:628–638. DOI:10.1016/j.ecoleng.2014.07.064 · 2.58 Impact Factor
    • "nt TN gradually decreased from 1 . 5 to 0 . 6 mg / L , and effluent TN decreased from 1 . 2 to 0 . 1 mg / L . The TN removal efficiency gradually increased from 17 . 3% to 81 . 8% at the end of experiment ( stage 3 ) . The increase in removal efficiency might be primarily attributed to the growth of denitrifying bacteria in the gravel bed filter ( Lu et al . , 2009 ) . Notably , such TN removal efficiency was much higher than the value obtained at the steady state condition ( stage 1 ) . A possible explanation would be the influence of temperature on denitrifica - tion . The first experiment ( stage 1 ) was conducted in early spring , whereas the second experiment ( stage 3 ) started in mid April "
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    ABSTRACT: 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 PO43--P were all above 50% at hydraulic loading rate of 1.2 m/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.
    Ecological Engineering 12/2013; 61:383-389. DOI:10.1016/j.ecoleng.2013.09.043 · 2.58 Impact Factor
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    • "condary treated nitri - fied effluents from conventional wastewater treatment systems that virtually contain no organic matter ( Headley et al . , 2001 ) . In conventional wastewater treatment systems , this limitation can be overcome by the addition of an external dissolved organic carbon source , such as methanol , ethanol , acetate or glucose ( Lu et al . , 2009 ) . However , the plants growing in wetlands automat - ically convert atmospheric CO 2 into biomass ( organic C ) through photosynthesis . This endogenously derived organic C in the wet - lands can then potentially become available to denitrifying bacteria through a number of pathways , including death and decomposition of plant litter "
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    ABSTRACT: Rooted emergent wetland plants may deliver organic carbon via root exudates to fuel the microbial denitrification process in subsurface flow constructed wetland systems receiving nitrate-rich and low-carbon wastewater. We quantified the amount of dissolved organic carbon (DOC) released from roots of three wetland species, Phragmites australis, Iris pseudacorus and Juncus effusus, which are commonly used in constructed wetlands. Plants were grown hydroponically at two temperatures (10 and 20 °C) and three light-regimes (a normal 14 h:10 h light:dark cycle, continuous light and continuous dark), and the release rates of DOC from the roots as well as the uptake rates of NH4-N, NO3-N, PO4-P and K were analyzed. DOC release rates were significantly different among the three species, and were also affected by temperature and light-regime. At 20 °C, higher amounts of DOC were generally released in the root exudates than at 10 °C. The average DOC release rate of the three species was nearly two times higher in the light (10.2 ± 0.7 μg g−1 root DM h−1) than in the dark (6.8 ± 0.7 μg g−1 root DM h−1). As expected, DOC release rates were positively related to the relative growth rate (RGR) and nutrient uptake rate. DOC release rates amounted to 0.6–4.8% of the net photosynthetically fixed carbon. Extrapolating the laboratory measurements to field conditions suggests that plant root exudates may potentially fuel a denitrification rate of 94–267 kg N ha−1 year−1 in subsurface flow constructed wetlands. Hence, root exudates are potentially important as an organic C source for denitrification in lightly loaded subsurface flow constructed wetland systems receiving nitrate-rich water with a low content of BOD (e.g. nitrified effluent or agricultural drainage).
    Ecological Engineering 12/2013; 61:555–563. DOI:10.1016/j.ecoleng.2013.02.014 · 2.58 Impact Factor
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