Influence of surface layer on hydrology and biology of gravel bed vertical flow constructed wetlands

In France, gravel vertical flow constructed wetlands (gVFCWs) were adapted to treat raw wastewater, which led to important accumulations of matter in filters (organic and mineral). To prevent clogging, large gravel sizes were employed (O 2-6 mm). The aim of this paper was to present the influences o...

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Bibliographic Details
Published in:Water science and technology 2005-01, Vol.51 (9), p.91-97
Main Authors: Chazarenc, F, Merlin, G
Format: Article
Language:English
Subjects:
Artificial wetlands
Biodiversity
Biology
Data Collection
Density stratification
Ecosystem
Filters
Filtration
Fluid filters
France
Gravel
Hydrology
Microfauna
Oxygen - metabolism
Particle Size
Percolation
Raw wastewater
Respiration
Stratification
Surface layers
Surveying
Vertical distribution
Vertical flow
Vertical mixing
Waste Disposal, Fluid - methods
Wastewater
Wastewater treatment
Water Movements
Wetlands
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Summary:In France, gravel vertical flow constructed wetlands (gVFCWs) were adapted to treat raw wastewater, which led to important accumulations of matter in filters (organic and mineral). To prevent clogging, large gravel sizes were employed (O 2-6 mm). The aim of this paper was to present the influences of matter accumulation on the hydraulic and biological behaviour of the system. A one-year survey of accumulated matter content and potential respiration activities was completed in three gVFCWs (operating for 3, 4 and 8 years). Cores were sampled into filters. Results showed a vertical stratification of accumulated matter and respiration rates. Dry accumulated matter quantities ranged from 20 kg m(-2) (3 and 4 years operating) to 80 kg m(-2) in the oldest plant (8 years). Potential respiration was larger in the oldest plant (75g O2m(-2)h(-1)) than in the most recent one (15g O2m(-2)h(-1)). Accumulated matter seemed to play a role both on the water retention (enhancing initial percolation time by 5 times) and biological profile (enhancing microfauna's diversity). Contrary to what is generally proposed in the literature, accumulated matter in French gVFCWs seemed to provide better treatment efficiency without leading to surface clogging compared to systems using sand.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2005.0295