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Phosphorus retention in constructed wetlands enhanced by zeolite- and clinopyroxene-dominated lava sand

Alewell, Christine; Huang, Jen-How; McLaren, Timothy I.; Huber, Lea and Bünemann, Else K. (2021) Phosphorus retention in constructed wetlands enhanced by zeolite- and clinopyroxene-dominated lava sand. Hydrological Processes, 35 (2), e14040.

[thumbnail of alewell-etal-2021-HydrologicalProcesses-Vol35-Issue2-pe14040.pdf] PDF - Published Version - English
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Document available online at: https://onlinelibrary.wiley.com/doi/full/10.1002/hyp.14040


Constructed wetlands (CWs) are engineered systems for treating wastewater by sequestering nutrients and contaminants. Our aim was to assess the main phosphorus (P) binding states in operating CWs to assess P saturation and indications on P recycling potential of filter materials, which might be necessary under future peak P scenarios. The investigated vertical flow CWs (operation time up to 16 years) are based on either fluviatile (Fluv) sand or zeolite- (Ze-LS) and clinopyroxene (Cl-LS)-dominated lava sand. Organic and inorganic P accumulated in all CWs independent of filter materials and showed a considerable increase with operation time. Concentrations of P decreased sharply with depth in the Fluv-CWs compared to only a slight decrease in the lava sand CWs, with P concentrations of deeper horizons approximating the relatively P enriched original lava sand substrates. Orthophosphate was the dominant pool in all CWs, while the sum of organic fractions ranged between 11% and 33%. Sequential extraction indicated that P was mainly associated with Fe and Al (hydr)oxides for Fluv-CWs and Ze-LS-CWs, while Ca and Mg bound mineral phosphates dominated in Cl-LS-CWs. Oxalate extractions pointed to a clear dominance of P fractions associated with poorly crystalline Fe- and Al-(oxy)hydroxides. Solution 31P NMR analyses revealed that inositol hexakisphosphates were a major pool of organic P in surface layers of CWs, which increased with operation time. With a maximum of 0.5% P content, filter sands do not appear to be a suitable fertilizer for direct application to agricultural fields. The dominance of inorganic, poorly crystalline P species point to potentially high desorption capacity which might be investigated further, to assess recycling potential of P or usage of filter materials as soil amendments with relatively high plant available P. The latter might become feasible and economically attractive under future P scarcity. Simultaneously, P saturation indexes (DPS) did not indicate an imminent P saturation of filters, since P accumulation was not restricted by binding to Al and Fe minerals.

EPrint Type:Journal paper
Keywords:filter materials, NMR spectroscopy, organic P species P recycling, P saturation, sequential P extraction, vegetated soil filters, waste water cleaning
Agrovoc keywords:
filtering -> filtration
waste water -> wastewater
Subjects: Environmental aspects > Air and water emissions
Research affiliation: Switzerland > ETHZ - Agrarwissenschaften
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil > Soil quality
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Sustainability > Nature conservation > Water protection
Switzerland > University of Basel
Deposited By: Forschungsinstitut für biologischen Landbau, FiBL
ID Code:40132
Deposited On:29 Jun 2021 08:03
Last Modified:29 Jun 2021 08:03
Document Language:English
Refereed:Peer-reviewed and accepted

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