URL | Facility

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Facility

The URL is an outdoor laboratory consisting of channels with circulating water and wetlands designed to investigate new techniques to improve the water quality of highly modified streams and rivers. Feeding water comes from the effluent of a wastewater treatment plant.

Channels

18 channels of 12 meters length with a section of 0.74 x 0.47 m. The circulating water comes from a central tank fed by treated water from the effluent of a wastewater treatment plant. The input flow rate of each channel is adjustable up to 0.5 L/s.

Current setting:

The current experimental setting was designed to examine the influence of different species of helophytes, commonly used in river restoration, on the biogeochemistry of water flowing through the sediment where they are rooted. The channel beds are covered with gravel (5 to 50 mm diameter) and the water flows sub-surficially at a rate of 5 L/min. In 15 out of 18 channels, we planted 5 species of helophytes: Typha angustifolia, Iris pseudachorus, Phragmites australis, Lysimachia vulgaris and Scirpus lacustris, with 3 replicates per each species. The remaining 3 channels were kept unvegetated (only gravels) and served as control treatments.

Physico-chemical variables of the circulating water*:

NH₄⁺ (mg N/L): 1.0 ± 0.3

NO₃^– (mg N/L): 3.3 ± 0.3

NO₂^– (mg N/L): 0.1 ± 0.03

PO₄⁺(mg P/L): 0.7 ± 0.4

DIN:P (molar): 26 ± 17

Conductivity (µS/cm): 1704 ± 3

Oxygen (mg/L): 5.9 ± 0.1

Flow rate (L/min): 4.8 ± 0.1

(*) Data measured in June 2015, corresponding to the mean ± standard error of the water entering to the 18 channels.

Wetlands

There are 4 units of stainless steel of 4.5 x 1.8 x 0.4 m divided into three compartments of 1.5 x 1.8 m each, resulting in a total of 12 experimental wetlands. The supplying water of the wetlands is obtained from a central tank fed with treated water from the effluent of a wastewater treatment plant.

Current setting:

The current experimental setting is designed to test the role of helophytes in the biogeochemistry of hyphorreic water in wetlands. 6 wetlands were vegetated with Iris pseudachorus, one of the most common helophyte species used in river restoration and 6 were rested unvegetated and served as a control. We considered two sediment types differing in their grain size (sand and gravel) because their distinct hydraulic conductivity can influence differently nutrient cycling at the microhabitat scale. Each treatment of presence/absence of Iris has 6 replicates of each sediment type. Wetlands are flooded periodically.