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result(s) for
"constructed wetlands"
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Existing forms and changes of nitrogen inside of horizontal subsurface constructed wetlands
Horizontal zeolite subsurface constructed wetland system (HZCWs) and horizontal limestone subsurface constructed wetland system (HLCWs) were applied to the removal of nitrogen in lightly polluted wastewater, and the existing forms, changes, and removal mechanism of nitrogen in the constructed wetlands were analyzed. The results indicated that compared with HLCWs, HZCWs exhibited better nitrogen removal effect, and the maximum removal rates of ammonia nitrogen and total nitrogen could reach 96.97 ± 5.29 and 93.12 ± 3.35%, respectively. Besides, analysis of the removal effect on nitrogen in different existing forms on different substrate heights in the constructed wetlands showed that variation of nitrogen removal efficiency had certain regularities, which were related to the interior construction features of the wetland systems, and agreed with the regularities in the changes of the influential factors such as DO inside of the wetlands. In addition, degradation mechanism of pollutions was also analyzed, and the results indicated that the quantity of microorganisms and enzymes, including FDA, catalase, and urease, on the surface of the substrates had significant influence on the removal regularities and effects of the major pollutions in constructed wetlands.
Journal Article
Transformation from biofiltration unit to hybrid constructed wetland-microbial fuel cell: Improvement of wastewater treatment performance and energy recovery
This study aimed to compare the performance of biofiltration, constructed wetland, and constructed wetland microbial fuel cell (CW-MFC). The transformation from a biofiltration unit to a hybrid CW-MFC was demonstrated with the advantages of improvement of wastewater treatment while generating electricity simultaneously. The introduction of plants to the upper region of the bioreactor enhanced the DO level by 0.8 mg/L, ammonium removal by 5 %, and COD removal by 1 %. The integration of electrodes and external circuits stimulated the degradation rate of organic matter in the anodic region (1 % without aeration and 3 % with aeration) and produced 5.13 mW/m
3
of maximum power density. Artificial aeration improved the nitrification efficiency by 38 % and further removed the residual COD to an efficiency of 99 %. The maximum power density was also increased by 3.2 times (16.71 mW/m
3
) with the aid of aeration. In treating higher organic loading wastewater (3M), the maximum power density showed a significant increment to 78.01 mW/m
3
(4.6-fold) and the COD removal efficiency was 98 %. The ohmic overpotential dominated the proportion of total loss (67-91 %), which could be ascribed to the low ionic conductivity. The reduction in activation and concentration loss contributed to the lower internal resistance with the additional aeration and higher organic loading. Overall, the transformation from biofiltration to a hybrid CW-MFC system is worthwhile since the systems quite resemble while CW-MFC could improve the wastewater treatment as well as recover energy from the treated wastewater.
Journal Article
Enhanced wastewater treatment and electricity generation using stacked constructed wetland–microbial fuel cells
Water pollution and energy production are major issues in the context of climate change, urbanization and industrialization. There is need for cost-effective and sustainable processes for wastewater treatment. Here we designed a novel system made of a stack of 12 vertically-arranged constructed wetlands coupled with microbial fuel cells. Performance was evaluated in terms of chemical oxygen demand (COD) removal, NH4+–N, NO3−–N, and PO4−3 removal efficiency, and electricity generation. The results reveal that the efficiency of COD removal increased gradually with decreasing external resistance, reaching 98.5% at 0.08 kΩ. The maximum removal efficiency was 90.4% for NH4+–N at 15 kΩ and 86.9% for NO3–N at 0.08 kΩ. The maximum power density reached 30.85 mW/m3 at 15 kΩ.
Journal Article
Effects of plants and soil microorganisms on organic carbon and the relationship between carbon and nitrogen in constructed wetlands
Constructed wetland is an ideal place for studying the effects of plants and microorganisms on the nutrient cycling and carbon–nitrogen coupling in wetland for their clear background. This study examined both bare plots and others with plants (
Phragmites australis
or
Typha angustifolia
) in constructed wetlands and vegetation and soil samples were collected to investigate the effects of plants and soil microorganisms on carbon and nitrogen content. Results showed that the soil organic carbon content was high in plots with high plant biomass, and the increase of soil organic carbon driven by plant biomass was mainly from light fraction organic carbon (LFOC). Correlation analysis and redundancy analysis (RDA) suggested that plants play an important role in the cycle of carbon and nitrogen elements in constructed wetland soils, and that plant nitrogen components were key factors influencing wetland soil carbon and nitrogen. In addition, this study found that most of the main microbial taxa were significantly correlated with dissolved organic carbon (DOC), ammonium nitrogen (NH
4
+
), and nitrate and nitrite nitrogen (NO
x
−
) indicating that microorganisms might play an important role in regulating soil element cycles in constructed wetlands by affecting the metabolism of activated carbon and reactive nitrogen. This study has implications for increasing the carbon sink of constructed wetlands to mitigate the effects of global warming.
Journal Article
Effects of Design and Operational Conditions on the Performance of Constructed Wetlands for Agricultural Pollution Control – Critical Review
Constructed wetlands (CWs) can be considered as an efficient nature-based solution for the treatment of agricultural drainage water (ADW) and consequently for the mitigation of non-point source pollution. Aiming to provide suggestions for the construction and implementation of CWs, this paper proposes and discusses key parameters of CW design and operation. In order to verify the effect of these features, different case studies were reviewed, focusing on the performance of CWs that are treating agricultural drainage water. The findings showed that design and operational factors (e.g., the application of simple hydraulic structures and vegetation establishment) can improve pollutant removal efficiencies by increasing hydraulic retention time. Hydraulic efficiency of CWs can also be enhanced through certain shape characteristics (e.g., adoption of a high aspect ratio and creation of a long and narrow CW shape). The careful consideration of these parameters before and during CW implementation can therefore help these systems to achieve their full potential. However, further study is recommended to assess the effects of some parameters (e.g., flow direction and the application of deep zones).
Journal Article
A Complete Water Balance of a Constructed Stormwater Wetland
Constructed wetlands are often overlooked as a stormwater management system in the urban context. In comparison to alternatives (e.g., green roofs, bioretention, bioinfiltration), constructed wetlands have a much larger space requirement, which comes at a cost and can be challenging to allocate. The stormwater management function of constructed wetlands in urban settings has therefore not been extensively studied and understood. Constructed wetlands are well‐understood to provide services to humans and for creating more hospitable habitats to organisms, thus reducing fragmentation of their habitats and aiding in ecological protection and restoration. Ultimately, as hydrological systems, they demonstrate the potential to provide both stormwater and ecosystem services. To assess the stormwater management capabilities of a constructed wetland in Villanova, Pennsylvania, USA, a novel and comprehensive water budget model was developed. The constructed wetland of interest was retrofitted from an existing retention basin with the hypothesis that under a wetland configuration, the system could manage a comparable amount of incoming flow and provide more ecosystem services. The water budget model was aimed at assessing how water flows through the system during both wet (active rainfall) and dry conditions (baseflow between rainfall). Over 10 years of monitoring, the constructed wetland was found to manage 37% of incoming flow through percolation and evapotranspiration from a large receiving area. Additionally, the hydrological signature of the large receiving area mimics that of a less‐developed or less‐impervious area with the constructed wetland in place.
Journal Article
Domestic wastewater treated with Sagittaria latifolia in constructed wetlands
Constructed wetlands are viable alternatives for the removal of multiple pollutants. The performance of Sagittaria latifolia in free flowing and subsurface wetlands in removing pollutants from domestic waters was evaluated. 12 wetlands will be followed, three free with species and three without species, three subsurface with species and three without species, with retention times of 6.7 days for the free and 3.5 days for the subsurface. The subsurface with species presented an effluent with turbidity of 4.4±0.8 NTU, color of 143.9±27.4 UC and 33.9±25.7 mgL-1 of COD. The free samples with species presented turbidity of 10.1±2.8 NTU, color of 346.3±87.0 UC and 74.7±30.0 mgL-1 of COD. The wetland with the best performance was the subsurface with species, eliminating turbidity, color, and COD in 95.9, 89.4, 95.7% respectively, obtaining a COD kinetic coefficient of 0.34 (free flow) and 0.89 days-1 (subsurface).
Journal Article