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Headley T.R.,Southern Cross University of Australia | Headley T.R.,Helmholtz Center for Environmental Research | Headley T.R.,BAUER Nimr LLC | Davison L.,Southern Cross University of Australia | And 2 more authors.
Water Research | Year: 2012

The balance between evapotranspiration (ET) loss and rainfall ingress in treatment wetlands (TWs) can affect their suitability for certain applications. The aim of this paper was to investigate the water balance and seasonal dynamics in ET of subsurface horizontal flow (HF) TWs in a sub-tropical climate. Monthly water balances were compiled for four pilot-scale HF TWs receiving horticultural runoff over a two year period (Sep. 1999-Aug. 2001) on the sub-tropical east-coast of Australia. The mean annual wetland ET rate increased from 7.0 mm/day in the first year to 10.6 mm/day in the second, in response to the development of the reed (Phragmites australis) population. Consequently, the annual crop coefficients (ratio of wetland ET to pan evaporation) increased from 1.9 in the first year to 2.6 in the second. The mean monthly ET rates were generally greater and more variable than the Class-A pan evaporation rates, indicating that transpiration is an important contributor to ET in HF TWs. Evapotranspiration rates were generally highest in the summer and autumn months, and corresponded with the times of peak standing biomass of P. australis. It is likely that ET from the relatively small 1 m wide by 4 m long HF TWs was enhanced by advection through so-called " clothesline" and " oasis" effects, which contributed to the high crop coefficients. For the second year, when the reed population was well established, the annual net loss to the atmosphere (taking into account rainfall inputs) accounted for 6.1-9.6 % of the influent hydraulic load, which is considered negligible. However, the net loss is likely to be higher in arid regions with lower rainfall. The Water Use Efficiency (WUE) of the wetlands in the second year of operation was 1.3 g of above-ground biomass produced per kilogram of water consumed, which is low compared to agricultural crops. It is proposed that system level WUE provides a useful metric for selecting wetland plant species and TW design alternatives to use in arid regions where excessive water loss from constructed wetlands can be problematic. Further research is needed to accrue long-term HF TW water balance data especially in arid climatic zones. © 2011 Elsevier Ltd. Source

Tanner C.C.,NIWA - National Institute of Water and Atmospheric Research | Sukias J.P.S.,NIWA - National Institute of Water and Atmospheric Research | Headley T.R.,NIWA - National Institute of Water and Atmospheric Research | Headley T.R.,BAUER Nimr LLC | And 2 more authors.
Ecological Engineering | Year: 2012

The performance of five alternative treatment trains receiving primary domestic wastewaters was compared in side-by-side trials over an annual period after 2 years maturation. One of the systems was a passive horizontal-flow wetland. The other four hybrid systems comprised different configurations of subsurface horizontal- and/or intermittently-dosed (24/d) vertical-flow constructed wetlands (single pass or recirculating), and attached growth and carbonaceous (wood-chip and coconut husk) denitrifying bioreactors. The scale of the systems ranged from ∼20 to 40% of that required for a single household. Mean biochemical oxygen demand (BOD 5) and total suspended solids (TSS) were reduced by over 94% in all systems. Mean ammonium-N (NH 4-N) concentrations were reduced to between 0.05 and 0.20gm -3 (98-99.8% reduction) in the hybrid wetland and bioreactor systems, compared to ∼13gm -3 (61% reduction) in the horizontal-flow wetland. Mean total nitrogen (TN) removal ranged from 49% in the horizontal-flow wetland to between 58 and 95% in the hybrid systems. Apparent nitrification rates of 3.8-7.3gNm -2d -1 (based on ammonium reduction) were recorded in the vertical-flow wetlands and apparent denitrification rates of 2.8-12.4gNm -3d -1 (based on nitrate reduction) in linked denitrifying bioreactors and horizontal-flow wetlands. Mean total phosphorus (TP) removal ranged from 36 to 65%, while faecal indicator bacteria were reduced by 2.5-4.7log units in the different systems. The results of this study show that simple hybrid systems combining wetland and denitrifying bioreactor components are capable of achieving advanced effluent quality with low energy inputs. The areas required for these hybrid systems were generally half or less of those required for horizontal-flow wetlands. © 2012 Elsevier B.V. Source

Zhai X.,University of Aarhus | Piwpuan N.,University of Aarhus | Arias C.A.,University of Aarhus | Headley T.,BAUER Nimr LLC | Brix H.,University of Aarhus
Ecological Engineering | Year: 2013

Rooted emergent wetland plants may deliver organic carbon via root exudates to fuel the microbial denitrification process in subsurface flow constructed wetland systems receiving nitrate-rich and low-carbon wastewater. We quantified the amount of dissolved organic carbon (DOC) released from roots of three wetland species, Phragmites australis, Iris pseudacorus and Juncus effusus, which are commonly used in constructed wetlands. Plants were grown hydroponically at two temperatures (10 and 20°C) and three light-regimes (a normal 14h:10h light:dark cycle, continuous light and continuous dark), and the release rates of DOC from the roots as well as the uptake rates of NH4-N, NO3-N, PO4-P and K were analyzed. DOC release rates were significantly different among the three species, and were also affected by temperature and light-regime. At 20°C, higher amounts of DOC were generally released in the root exudates than at 10°C. The average DOC release rate of the three species was nearly two times higher in the light (10.2±0.7μgg-1rootDMh-1) than in the dark (6.8±0.7μgg-1rootDMh-1). As expected, DOC release rates were positively related to the relative growth rate (RGR) and nutrient uptake rate. DOC release rates amounted to 0.6-4.8% of the net photosynthetically fixed carbon. Extrapolating the laboratory measurements to field conditions suggests that plant root exudates may potentially fuel a denitrification rate of 94-267kgNha-1year-1 in subsurface flow constructed wetlands. Hence, root exudates are potentially important as an organic C source for denitrification in lightly loaded subsurface flow constructed wetland systems receiving nitrate-rich water with a low content of BOD (e.g. nitrified effluent or agricultural drainage). © 2013 Elsevier B.V. Source

Fonder N.,University of Liege | Headley T.,Helmholtz Center for Environmental Research | Headley T.,BAUER Nimr LLC
Ecological Engineering | Year: 2013

This paper proposes a structure for classifying and naming different treatment wetland (TW) design alternatives, based on physical design traits. A classification hierarchy is organised like a polychotomous key, from general classification criteria to wetland type identification. Three characteristics are typical of all TWs: the presence of macrophytic vegetation; the existence of water-logged or saturated substrate conditions for at least part of the time; and inflow of contaminated water with constituents to be removed. Treatment wetlands are further classified based on hydrology and vegetation characteristics. Hydrological traits relate to water position, flow direction, degree of saturation and position of influent loading. Based on the predominant position of water in the system, two main groups are identified: those with surface flow above a benthic substrate and those with subsurface flow through a porous media. The systems with surface flow are divided into three standard types, differentiated by vegetation type: Surface flow (SF), free-floating macrophyte (FFM), and floating emergent macrophyte (FEM) TWs. Subsurface flow systems always contain sessile emergent macrophytes and are divided into four standard types, based on flow direction: horizontal sub-surface flow (HSSF), vertical down flow (VDF), vertical up flow (VUF) and fill and drain (FaD) TWs. Standard types are described with their main applications. Associated variants are identified. An overview of intensified variants, which have elevated energy, chemical or operational inputs in order to increase efficiency or overcome process limitations, is also provided. © 2012 Elsevier B.V. Source

Nivala J.,University of Aarhus | Nivala J.,Helmholtz Center for Environmental Research | Headley T.,BAUER Nimr LLC | Wallace S.,Naturally Wallace Consulting LLC | And 4 more authors.
Ecological Engineering | Year: 2013

The Langenreichenbach ecotechnology research facility contains 15 individual pilot-scale treatment systems of eight different designs or operational variants. The designs differ in terms of flow direction, degree of media saturation, media type, loading regime, and aeration mechanism. Seven systems were constructed as planted and unplanted pairs, in order to elucidate the role of common reed (Phragmites australis) in these technologies. The facility is unique in the fact that it is located adjacent to the wastewater treatment plant for the nearby village, enabling all of the pilot-scale systems to receive the same wastewater. The construction of the Langenreichenbach research facility is placed within the overarching discipline of ecological engineering. An overview of the treatment wetland design spectrum (ranging from passive to highly intensified designs) is discussed and the specific designs implemented at Langenreichenbach are presented in detail, along with the internal sampling methods for both saturated and unsaturated systems. © 2013 Elsevier B.V. Source

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