Article

Nutrient removal in tropical subsurface flow constructed wetlands under batch and continuous flow conditions

DHI-NTU Centre, Nanyang Environment & Water Research Institute, Nanyang Technological University, N1.2-B1-02, 50 Nanyang Avenue, 639798 Singapore.
Journal of Environmental Management (Impact Factor: 2.72). 04/2012; 96(1):1-6. DOI: 10.1016/j.jenvman.2011.10.009
Source: PubMed

ABSTRACT

The aim of this investigation was to evaluate the influence of batch versus continuous flow on the removal efficiencies of chemical oxygen demand (COD), nitrogen (N) and total phosphorus (TP) in tropical subsurface flow constructed wetlands (SSF CW). The quantitative role of the higher aquatic plants in nutrient removal in these two operational modes was also investigated. Results indicated no significant difference (p > 0.05) in COD removal between batch and continuous flow modes for either the planted or unplanted treatments. Furthermore, the batch-loaded planted wetlands showed significantly (p < 0.05) higher ammonium removal efficiencies (95.2%) compared with the continuously fed systems (80.4%), most probably because the drain and fill batch mode presented systematically more oxidized environmental conditions. With respect to TP removal, for both planted and unplanted beds, there was significant enhancement (p < 0.05) in batch flow operation (69.6% for planted beds; 39.1% for unplanted beds) as compared to continuous flow operation (46.8% for planted beds; 25.5% for unplanted beds). In addition, at a 4-day hydraulic retention time (HRT), the presence of plants significantly enhanced both ammonia oxidation and TP removal in both batch and continuous modes of operation as compared to that for unplanted beds. An estimation of the quantitative role of aeration from drain and fill operation at a 4-day HRT, as compared to rhizosphere aeration by the higher aquatic plant, indicated that drain and fill operation might account for only less than half of the higher aquatic plant's quantitative contribution of oxygen (1.55 g O2 per m2 per day for batch flow versus 1.13 g O2 per m2 per day for continuous flow).

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    • "With the unique advantages of lower costs and more benefits , CW treatments have evolved into a reliable wastewater treatment technology for removing pollutants from many types of wastewater during the last five decades of development. Moreover, according toZhang et al. (2012), the traditional CW was also a typical sustainable technology due to less investment, lower operation costs, less energy consumption, and more ecological benefits except for higher land requirement, as compared to conventional wastewater treatment processes. The current review indicates that advances on enhancing strategies and techniques employed in CWs have greatly improved the sustainable operation and successful application of this wastewater treatment system. "
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    ABSTRACT: Constructed wetlands (CWs) have been used as an alternative to conventional technologies for wastewater treatment for more than five decades. Recently, the use of various modified CWs to improve treatment performance has also been reported in the literature. However, the available knowledge on various CW technologies considering the intensified and reliable removal of pollutants is still limited. Hence, this paper aims to provide an overview of the current development of CW strategies and techniques for enhanced wastewater treatment. Basic information on configurations and characteristics of different innovations was summarized. Then, overall treatment performance of those systems and their shortcomings were further discussed. Lastly, future perspectives were also identified for specialists to design more effective and sustainable CWs. This information is used to inspire some novel intensifying methodologies, and benefit the successful applications of potential CW technologies.
    Full-text · Article · Aug 2015 · Environmental Science and Pollution Research
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    • "The increased removal in control units may also be facilitated due to sequential presence of anaerobic and aerobic conditions in Up-flow constructed wetlands where both mechanisms were in contribution for removal of organic matter as denitrifiction and aerobic biodegradation were played major role for excellent COD removal in control unit [13] [14]. Also an author [15] gives apparent reason for COD removal due to combine effect of aerobic and anaerobic organic carbon degradation. As it is known that the uptake of organic matter by plants is of less significant [16] the organic matter removal is not dependent on the presence/ absence of plant species in constructed wetlands. "
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    ABSTRACT: The use of constructed wetlands for wastewater treatment has been exercised since 1950's and still are being in use. The vertical flow constructed wetlands provide more oxygenated environment and significantly reduce the organic matter as well as microbial species from wastewater. In the present study vertical up-flow constructed wetlands were constructed and used as bio-filter to improve the water quality of secondary treated effluent. The reduction pattern is studied in this research and correlated with plant species and presence of plant. The plant species used in the constructed wetlands were canna and phragmitis. The fibrous rooting system of canna species causes the high aerobic conditions throughout the treatment bed which in turn facilitates higher removal in comparison to phragmitis planted wetland. Removal of nitrogenous compounds like ammonia-nitrogen, TKN and nitrate were observed better in canna planted wetlands than others.
    Full-text · Article · Dec 2014
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    • "In general, batch feeding mode can obtain the better performance than continuous operation by promoting more oxidized conditions. Zhang et al. (2012) investigated the influence of batch versus continuous flow on the removal efficiencies in tropical SSF CWs. They indicated that the wetlands with batch flow mode showed significantly higher ammonium removal efficiencies (95.2%) compared with the continuously fed systems (80.4%). "
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    ABSTRACT: Constructed wetlands (CWs) have been used as a green technology to treat various wastewaters for several decades. CWs offer a land-intensive, low-energy, and less-operational-requirements alternative to conventional treatment systems, especially for small communities and remote locations. However, the sustainable operation and successful application of these systems remains a challenge. Hence, this paper aims to provide and inspire sustainable solutions for the performance and application of CWs by giving a comprehensive review of CWs' application and the recent development on their sustainable design and operation for wastewater treatment. Firstly, a brief summary on the definition, classification and application of current CWs was presented. The design parameters and operational conditions of CWs including plant species, substrate types, water depth, hydraulic load, hydraulic retention time and feeding mode related to the sustainable operation for wastewater treatments were then discussed. Lastly, future research on improving the stability and sustainability of CWs were highlighted. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Full-text · Article · Oct 2014 · Bioresource Technology
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