HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (20) Citing Articles via Google Scholar Google Scholar Articles by Langergraber, G. Articles by Simunek, J. Search for Related Content PubMed Articles by Langergraber, G. Articles by Simunek, J. GeoRef GeoRef Citation Agricola Articles by Langergraber, G. Articles by Simunek, J. Related Collections Wetlands and Aquatic Processes Water Pollution Software Vadose Zone Processes and Chemical Transport

ORIGINAL RESEARCH

Modeling Variably Saturated Water Flow and Multicomponent Reactive Transport in Constructed Wetlands

Günter Langergraber^a,* and Jirka imnek^b

^a Institute of Sanitary Engineering and Water Pollution Control, BOKU Univ. of Natural Resources and Applied Life Sciences, Vienna, Muthgasse 18, A-1190 Vienna, Austria
^b Dep. of Environmental Sciences, Univ. of California, Riverside, CA 92521, USA
^* Corresponding author (guenter.langergraber{at}boku.ac.at)

Received 25 November 2004.

Constructed wetlands (CWs) are becoming increasingly popular worldwide for removing organic matter (OM), nutrients, trace elements, pathogens, or other pollutants from wastewater and/or runoff water. We present a multicomponent reactive transport model CW2D (i.e., Constructed Wetlands 2D), as an extension of the HYDRUS-2D variably saturated water flow and solute transport software package. CW2D was developed to model the biochemical transformation and degradation processes in subsurface-flow CWs. Such wetlands involve a complex mixture of water, substrate, plants, litter, and a variety of microorganisms to provide optimal conditions for improving water quality. The water flow regime in subsurface-flow CWs can be highly dynamic and requires the use of a transient variably saturated flow model. The biochemical components defined in CW2D include dissolved oxygen (DO), three fractions of OM (readily and slowly biodegradable, and inert), four N compounds (ammonium, nitrite, nitrate, and dinitrogen), inorganic P, and heterotrophic and autotrophic microorganisms. Organic N and organic P were modeled as part of the OM. The biochemical degradation and transformation processes were based on Monod-type rate expressions. All process rates and diffusion coefficients were assumed to be temperature dependent. Heterotrophic bacteria were assumed to be responsible for hydrolysis, mineralization of OM (aerobic growth), and denitrification (anoxic growth). Autotrophic bacteria were assumed to be responsible for nitrification, which was modeled as a two-step process. Lysis was considered to be the sum of all decay and sink processes. We demonstrate the performance of the model for one- and two-stage subsurface vertical flow CWs. Model simulations of water flow, tracer transport, and selected biochemical compounds are compared with experimental observations. Limitations of the model are discussed, and needs for model improvements are summarized.

Abbreviations: ASM, Activated Sludge Model • COD, chemical oxygen demand • CW, constructed wetland • CW2D, Constructed Wetlands 2D • DO, dissolved oxygen • IP, inorganic phosphorus • OM, organic matter • OM CI, inert OM • OM CR, readily biodegradable OM • OM CS, slowly biodegradable OM • PSCW, pilot-scale subsurface vertical flow constructed wetland • SSP, Small-Scale Plot • TOC, total organic carbon • XANb, autotrophic microorganisms, Nitrobacter • XANs, autotrophic microorganisms, Nitrosomonas • XH, heterotrophic microorganisms

This article has been cited by other articles:

				G. R. Miller, Y. Rubin, K. U. Mayer, and P. H. Benito Modeling Vadose Zone Processes during Land Application of Food-Processing Waste Water in California's Central Valley J. Environ. Qual., September 2, 2008; 37(5_Supplement): S-43 - S-57. [Abstract] [Full Text] [PDF]

				J. Simunek, M. Th. van Genuchten, and M. Sejna Development and Applications of the HYDRUS and STANMOD Software Packages and Related Codes Vadose Zone J., May 27, 2008; 7(2): 587 - 600. [Abstract] [Full Text] [PDF]

				G. Langergraber Modeling of Processes in Subsurface Flow Constructed Wetlands: A Review Vadose Zone J., May 27, 2008; 7(2): 830 - 842. [Abstract] [Full Text] [PDF]