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Water 2016, 8(12), 556; doi:10.3390/w8120556

Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands

1
Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin 541004, China
2
Collaborative Innovation Center for Water Pollution Control and Water Safety in Karst Area, Guilin University of Technology, Guilin 541004, China
3
Department of Bioscience, Aarhus University, 8000C Aarhus, Denmark
4
College of Earth Sciences, Guilin University of Technology, Guilin 541004, China
5
Sino-Danish Centre for Education and Research (SDC), 8000C Aarhus, Denmark
*
Authors to whom correspondence should be addressed.
Academic Editor: Fabio Masi
Received: 8 October 2016 / Revised: 22 November 2016 / Accepted: 23 November 2016 / Published: 29 November 2016
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
View Full-Text   |   Download PDF [3537 KB, uploaded 29 November 2016]   |  

Abstract

This study aimed at optimizing horizontal subsurface flow constructed wetlands (CWs) to improve hydraulic performance and pollutant removal efficiency. A groundwater modeling package (MODFLOW) was used to optimize three design parameters (length-to-width ratio, inlet/outlet-to-length ratio, and substrate size configuration). Using the optimized parameters, three pilot-scale CWs were built to treat actual wastewater. For model validation, we used a tracer test to evaluate hydraulic performance, and investigated the pollutant spatial distributions and removal efficiencies. We conclude that MODFLOW is suitable for designing CWs, accurately predicting that increasing hydraulic conductivity from surface to bottom layers could improve performance. However, the effect of vegetation, which decreased the hydraulic conductivity of the surface layer, should be considered to improve simulation results. Multilayer substrate configuration, with increasing hydraulic conductivity from the surface to bottom layers, significantly increased pollutant removal compared with monolayer configuration. The spatial variation in pollutant transport and degradation through the filling substrate showed that the multilayer configuration was able to increase use of the available space and moderately reduced short-circuiting and dead zones. Thus, multilayer CWs had higher experimental retention times, effective volume fractions and hydraulic efficiencies, and lower short-circuiting compared with monolayer CWs operating under similar conditions. View Full-Text
Keywords: constructed wetlands; MODFLOW; hydraulic conductivity; hydraulic performance; flow distribution; substrate size configuration; tracer test; multilayer; pollutant spatial distributions constructed wetlands; MODFLOW; hydraulic conductivity; hydraulic performance; flow distribution; substrate size configuration; tracer test; multilayer; pollutant spatial distributions
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Bai, S.; Lv, T.; Ding, Y.; Li, X.; You, S.; Xie, Q.; Brix, H. Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands. Water 2016, 8, 556.

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