Dear Colleagues,

The use of constructed wetland systems for purifying wastewater is an area of increasing importance in water resources management. Such systems typically include a combination of substrate, wetland plants, microorganisms, and fauna, such as earthworms. Efficiency of operation depends on composition and is variable over time due to reduced purifying capacity of constituents, changes in dissolved oxygen and susceptibility to clogging of the constucted wetland system. Therefore, the design and management of constructed wetland systems is very important in maintaining purifying capacity and system sustainability. This Special Issue of Water will bring together current knowledge of the design, operation and management of constructed wetland systems. The Special Issue will help inform the future development and implementation of effective constructed wetlands.

Dr. Alan Howard
Prof. Dr. Defu Xu
Guest Editors

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• constructed wetlands
• wastewater
• wetland plants
• water resources management
• purification

Title: Applicability of Constructed Wetlands to Treat Source-Separated Domestic Grey Wastewater-A Decade of
Dutch Experiences
Author: Tiemen A. Nanninga ^1,*,
Affiliation: ¹ Lettinga Associates Foundation, P.O. Box 500, 6700 AM Wageningen, The Netherlands;
* Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +31-317-483-202.
Abstract
Introduction: Constructed wetlands (CWs) are increasingly being implemented as a decentralised wastewater
treatment technology in both Northern and Southern countries. Although CWs have been used to treat
wastewater since the 1950’s, most of the experiences documented focus on technical performances during the
first three years after construction. Thus while CWs are often promoted as being a suitable technology for
wastewater treatment, long-term non-technical experiences are poorly documented.
Aim: The aim of this paper is to learn from experiences with CWs that treat grey wastewater at neighbourhood
scale for a decade or more and to identify possible constraints for future implementation of CWs. Three case
study sites in the Netherlands (Drielanden in Groningen; Polderdrift in Arnhem; Lanxmeer in Culemborg) serve
to assess socio-technical factors related to the operation of CWs. In addition, the performance of CWs
functioning longer than eight years will be assessed by conducting a sampling programme at one site (Lanxmeer)
under challenging conditions (winter). The constraints identified will be analysed in order to allow for
translocation to Southern countries.
Methodology: The implementation process, costs, operation and maintenance (O&M) requirements and
structures, functioning, performance, perceptions and experiences were investigated using 34 semi-structured
interviews with users, operators, policy makers, constructors and consultants. Literature reviews were used to
gather background information about the cases, wastewater, CWs and results from previously performed
sampling programmes. 36 Influent and effluent composite samples were collected during the last week of
January and first week of February 2011 from three vertical sub-surface flow CWs in Lanxmeer and analysed for
BOD5, COD, TKN, NO3^-, NO2^-, NH4⁺, Ptotal, TSS, E.coli, dissolved O2, pH and Temperature.
Results: Results show that annual renewal and O&M costs (€230-€285/household) were a bit lower than the
annual costs of the conventional wastewater treatment system in Culemborg (€292.06-€398.18/household), that
maintenance requirements proved to be more work and more complex than initially anticipated and that all CWs
needed adjustments or major revisions during start-up. In all three cases there were people highly motivated to
ensure that the CWs were implemented and used. Very good removal efficiencies were found during the
sampling programme (BOD5: 97.7-99.9%, COD: 89.1-96.7%, Ntotal: 42.8-95.0%, NH4
+: 66.5-99.7%, Ptotal: 69.4-
97.5%, TSS: 19.4-96.7%, E.coli reduction of Log 2.5-5.2), which were similar or better compared to those of the
nearby conventional wastewater treatment plant. In general operators and users were positive about the CWs.
Conclusions: CWs have shown to be comparable in costs and efficiency to conventional technologies, yet the
start-up and operational and maintenance requirements proved to be more demanding than anticipated. Thus
despite often being promoted as robust, simple and ideal for rural areas, CWs have critical boundary conditions
that are actually quite complex and need to be addressed to ensure successful functioning.
Keywords: constructed wetlands, grey wastewater, decentralised, performance, operation and maintenance,
costs, implementation, users’ perceptions

Title: Economic Valuation of Constructed Wetlands with Treated Wastewater: A Review of Environmental Valuation Techniques and Ecosystemic Services
Author: Oscar Alfranca
Abstract: The objective of the paper is to revise the main literature on the use of environmental valuation techniques for the calculation of the environmental value of wetlands with treated wastewater. In the paper the efficiency of the different environmental valuation techniques to evaluate the main ecosystemic services related to wetlands will be discussed, both considering the relevance of the different economic and hydrological conditions. So finally, the quality of the different environmental valuation techniques is examined, and also the efficiency of these techniques to quantify the different environmental and economic characteristics of the constructed wetlands.