scholarly journals How to treat raw sewage with constructed wetlands: an overview of the French systems

2005 â—½  
Vol 51 (9) â—½  
pp. 11-21 â—½  
Author(s):  
P. Molle â—½  
A. Liénard â—½  
C. Boutin â—½  
G. Merlin â—½  
A. Iwema
Keyword(s):  
Constructed Wetlands â—½  
Pollutant Removal â—½  
Vertical Flow â—½  
Low Level â—½  
Vertical Flow Constructed Wetlands â—½  
And Performance â—½  
Raw Wastewater

The development of vertical flow constructed wetlands treating raw wastewater in France has proved to be very successful over the last 20 years. In view of this a survey was carried out on more than 80 plants in order to study their performance and correct the design if necessary. This study shows that such systems perform well in terms of respecting the goals of both low level outlet COD and SS and nitrification. Pollutant removal performance in relation to the loads handled and the specific characteristics of the plants were investigated. Nitrification is shown to be the most sensitive process in such systems and performance in relation to sizing is discussed. Such systems, if well designed, can achieve an outlet level of 60 mg L−1 in COD, 15 mg L−1 in SS and 8 mg L−1 in TKN with an area of 2–2.5 m2.PE−1. The sludge deposit on the first stage must be removed after about 10–15 years.

French vertical flow constructed wetlands: a need of a better understanding of the role of the deposit layer

2013 â—½  
Vol 69 (1) â—½  
pp. 106-112 â—½  
Author(s):  
Pascal Molle
Keyword(s):  
Constructed Wetlands â—½  
Organic Layer â—½  
Vertical Flow â—½  
Biological Behaviour â—½  
Positive Role â—½  
Vertical Flow Constructed Wetlands â—½  
Key Factor â—½  
Deposit Layer â—½  
Raw Wastewater

French vertical flow constructed wetlands, treating directly raw wastewater, have become the main systems implemented for communities under 2,000 population equivalent in France. Like in sludge drying reed beds, an organic deposit layer is formed over time at the top surface of the filter. This deposit layer is a key factor in the performance of the system as it impacts hydraulic, gas transfers, filtration efficiency and water retention time. The paper discusses the role of this deposit layer on the hydraulic and biological behaviour of the system. It presents results from different studies to highlight the positive role of the layer but, as well, the difficulties in modelling this organic layer. As hydraulic, oxygen transfers, and biological activity are interlinked and impacted by the deposit layer, it seems essential to focus on its role (and its quantification) to find new developments of vertical flow constructed wetlands fed with raw wastewater.

Constructed wetlands for the treatment of raw wastewater: the French experience

2014 â—½  
Vol 9 (3) â—½  
pp. 430-439 â—½  
Author(s):  
S. Troesch â—½  
F. Salma â—½  
D. Esser
Keyword(s):  
Organic Matter â—½  
Constructed Wetlands â—½  
Suspended Solids â—½  
Oxygen Demand â—½  
Vertical Flow â—½  
Small Communities â—½  
Vertical Flow Constructed Wetlands â—½  
French Experience â—½  
Raw Wastewater

Vertical flow constructed wetlands for small communities (<5,000 population equivalent) have been successfully developed in France since the 1990s (currently about 3'000 plants are in operation). This paper summarizes the results and efficiencies of 70 plants designed and built by Epur Nature or SINT. The results show clearly that the design performs well for organic matter removal and nitrification and makes sludge management easy. Therefore if well designed, such systems can achieve an outlet quality of BOD5 < 20 mg/L, chemical oxygen demand <90 mg/L, suspended solids <30 mg/L and TKN < 15 mg/L. In addition, some new configurations involving a French vertical first stage fed with raw sewage, patented by Epur Nature, are presented as an aid to reduce the global footprint.

Reversing Clogging in Vertical-Flow Constructed Wetlands by Backwashing Treatment

2010 â—½  
Vol 129-131 â—½  
pp. 1064-1068
Author(s):  
Fei Ma â—½  
Li Jiang â—½  
Ting Zeng
Keyword(s):  
Waste Water â—½  
Hydraulic Conductivity â—½  
Constructed Wetlands â—½  
Constructed Wetland â—½  
Removal Rate â—½  
Pollutant Removal â—½  
Vertical Flow â—½  
Vertical Flow Constructed Wetlands â—½  
The World â—½  
Design Guidance

More and more constructed wetland CW) were used to treat waste water in the world for its advantage on cheaper and efficiency. CW would clog for improper design or imperfect management, so application for it was limited. The purpose of this paper is that using backwashing method resolve filter media clogging problem which is an intractable matter in constructed wetlands project. The effects of the backwashing treatment on pollutant removal, as well as the influence on characteristics of hydraulics of wetlands, were studied. The experimental results indicate that CW hydraulic conductivity, hydraulic resistance time and removal rate of COD increased after backwashing. This paper confirmed that backwashing method can reverse clogging in vertical-flow constructed wetlands, and provided design guidance for applying backwashing method to treat clogging vertical-flow constructed wetlands.

The improvement of pollutant removal efficiency in saturated vertical flow constructed wetlands by tubifex tubifex

2020 â—½  
Vol 318 â—½  
pp. 124202
Author(s):  
Jiqiang Yang â—½  
Qiming Li â—½  
Yu An â—½  
Miao Zhang â—½  
Juan Du â—½  
...  
Keyword(s):  
Removal Efficiency â—½  
Constructed Wetlands â—½  
Pollutant Removal â—½  
Tubifex Tubifex â—½  
Vertical Flow â—½  
Vertical Flow Constructed Wetlands â—½  
Pollutant Removal Efficiency

scholarly journals Performance of the first stage of the French system of vertical flow constructed wetlands with only two units in parallel: influence of pulse time and instantaneous hydraulic loading rate

2018 â—½  
Vol 78 (4) â—½  
pp. 848-859 â—½  
Author(s):  
Jorge A. García Zumalacarregui â—½  
Marcos von Sperling
Keyword(s):  
Constructed Wetlands â—½  
Loading Rate â—½  
Oxygen Demand â—½  
Feeding Time â—½  
Vertical Flow â—½  
Hydraulic Loading Rate â—½  
Hydraulic Loading â—½  
Vertical Flow Constructed Wetlands â—½  
Removal Efficiencies â—½  
Raw Wastewater

Abstract The technology of vertical flow constructed wetlands – French system for treating raw wastewater depends on several hydraulic factors, one of them being the duration of the pulse feeding and the resulting instantaneous hydraulic loading rate. This paper analyses two scenarios in the same system, the first of a faster feeding by pump and the second of a slower feeding by siphon, both with instantaneous hydraulic loading rate values lower than the literature recommendations. The system treated raw wastewater from a population equivalent of 100 p.e. in Brazil, and was comprised by only the first stage and two units in parallel. The shorter duration of feeding time and higher instantaneous hydraulic loading rate were associated with significantly higher chemical oxygen demand and total Kjeldahl nitrogen removal efficiencies, but with no significant differences in terms of biochemical oxygen demand (BOD) and suspended solids (SS). Oxygen concentrations and redox potential in the effluent were evaluated, together with the effluent flow rate profiles. The removal efficiencies were associated with the accumulation of solids in the upper part of the filter resulting from seven years of operation and to the operating hydraulic conditions, which are important elements in the performance of the system.

scholarly journals The Effects of Plants on Pollutant Removal, Clogging, and Bacterial Community Structure in Palm Mulch-Based Vertical Flow Constructed Wetlands

Sustainability â—½  
10.3390/su11030632 â—½  
2019 â—½  
Vol 11 (3) â—½  
pp. 632 â—½  
Author(s):  
Marina Carrasco-Acosta â—½  
Pilar Garcia-Jimenez â—½  
José Alberto Herrera-Melián â—½  
Néstor Peñate-Castellano â—½  
Argimiro Rivero-Rosales
Keyword(s):  
Community Structure â—½  
Bacterial Community â—½  
Constructed Wetlands â—½  
Bacterial Community Structure â—½  
Rflp Analysis â—½  
Domestic Wastewater â—½  
Experimental Period â—½  
Pollutant Removal â—½  
Vertical Flow â—½  
Vertical Flow Constructed Wetlands

In this study, the effects of plants on the performance and bacterial community structure of palm mulch-based vertical flow constructed wetlands was studied. The wetlands were built in August 2013; one of them was planted with Canna indica and Xanthosoma sp., and the other one was not planted and used as a control. The experimental period started in September 2014 and finished in June 2015. The influent was domestic wastewater, and the average hydraulic surface loading was 208 L/m2d, and those of COD, BOD, and TSS were 77, 57, and 19 g/m2d, respectively. Although the bed without plants initially performed better, the first symptoms of clogging appeared in December 2014, and then, its performance started to fail. Afterwards, the wetland with plants provided better removals. The terminal restriction fragment length polymorphism (T-RFLP) analysis of Enterococci and Escherichia coli in the effluents suggests that a reduction in their biodiversity was caused by the presence of the plants. Thus, it can be concluded that the plants helped achieve better removals, delay clogging, and reduce Enterococci and E. coli biodiversity in the effluents.

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

2005 â—½  
Vol 51 (9) â—½  
pp. 91-97 â—½  
Author(s):  
F. Chazarenc â—½  
G. Merlin
Keyword(s):  
Constructed Wetlands â—½  
Matter Content â—½  
Vertical Flow â—½  
Treatment Efficiency â—½  
Biological Profile â—½  
Biological Behaviour â—½  
System A â—½  
Vertical Flow Constructed Wetlands â—½  
One Year â—½  
Raw Wastewater

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 (∅ 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 (75 g O2 m−2 h−1) than in the most recent one (15 g O2 m−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.

Vertical-flow constructed wetlands as an emerging solution for faecal sludge dewatering in developing countries

2011 â—½  
Vol 1 (1) â—½  
pp. 13-19 â—½  
Author(s):  
I. M. Kengne â—½  
E. Soh Kengne â—½  
Amougou Akoa â—½  
N. Bemmo â—½  
P.-H. Dodane â—½  
...  
Keyword(s):  
Developing Countries â—½  
Constructed Wetlands â—½  
Matter Content â—½  
Pollutant Removal â—½  
Dry Matter Content â—½  
Vertical Flow â—½  
Loading Rates â—½  
Solids Loading â—½  
Vertical Flow Constructed Wetlands â—½  
Faecal Sludge

Yard-scale experiments aiming at assessing the suitability of vertical-flow constructed wetlands to dewater faecal sludge (FS) were conducted in Yaoundé (Cameroon). During 6 months, beds vegetated either with Cyperus papyrus L. or Echinochloa pyramidalis (Lam.) Hitchc. & Chase were fed under constant solids loading rates (SLR) of 100, 200 and 300 kg TS (total solids) m−2/year. Physicochemical parameters of raw FS and percolate as well as the dewatering efficiency of each bed unit were monitored weekly. Results showed that, despite the high loading rates, the beds' pollutant removal efficiencies were more than 78% for the parameters considered and were not affected by the SLR or the macrophyte types. Beds loaded at 100 kg TS m−2/year rarely clogged with an average dry matter content ≥ 30%. However at SLR ≥ 200 kg TS m−2/year, the occurrence of clogging was higher in the papyrus beds than those of E. pyramidalis. Approximately 30–40 cm/year of sludge will be accumulated in beds loaded at the lowest SLR against 50–70 cm/year at 200 kg TS m−2/year and more than 80 cm/year at 300 kg TS m−2/year. These promising findings suggest the system as adequate for further investigation at real scale for FS dewatering in the context of developing countries.

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