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

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

scholarly journals Vertical flow constructed wetlands subject to load variations: an improved design methodology connected to outlet quality objectives

2015 ◽  
Vol 72 (5) ◽  
pp. 817-823 ◽  
Author(s):  
C. Boutin ◽  
S. Prost-Boucle
Keyword(s):  
Organic Matter ◽  
Constructed Wetlands ◽  
Oxygen Demand ◽  
Nitrification Rate ◽  
Vertical Flow ◽  
Design Standards ◽  
Rural Villages ◽  
Vertical Flow Constructed Wetlands ◽  
Nitrogen Concentrations ◽  
Improved Design

This study surveyed four campsites and four rural villages of major tourist interest, called tourist-interest or ti-villages, that were monitored for several years, generating over 70 performance balances for vertical flow constructed wetlands (VFCWs) that were intentionally scaled down for experimental trials. The wastewater effectively qualifies as domestic sewage, although relatively concentrated, with the campsites presenting particularly high nitrogen concentrations (122 gTKN L–1) (TKN: total Kjeldahl nitrogen). The applied daily loads were also particularly high, with some combinations of load parameters (hydraulic load, organic matter, TKN) leading to 400% overloading. Even under those drastic conditions, the quality of effluent remained excellent on the characteristic organic matter parameters, with removal performances always over 85%. Analysis of the dataset points to two major design thresholds: for campsites, in order to maintain a 73% nitrification rate even at the height of the summer season, the load applied onto the first stage filter in operation could achieve up to 600 gCOD m–2 day–1 (COD: chemical oxygen demand). For tourist-interest villages, in order to maintain an 85% nitrification rate, the load applied onto the second stage filter in operation could achieve up to 22 gTKN m–2.day–1. Here, VFCWs were demonstrated to robustly handle a massive increase in loads applied, providing the construction and operation stringently follow design standards and practices.

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 ◽  
Vol 78 (4) ◽  
pp. 848-859 ◽  
Author(s):  
Jorge A. García Zumalacarregui ◽  
Marcos von Sperling
Keyword(s):  
Constructed Wetlands ◽  
Loading Rate ◽  
Oxygen Demand ◽  
Feeding Time ◽  
Vertical Flow ◽  
Hydraulic Loading Rate ◽  
Hydraulic Loading ◽  
Vertical Flow Constructed Wetlands ◽  
Removal Efficiencies ◽  
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 Treatment performances of French constructed wetlands: results from a database collected over the last 30 years

2015 ◽  
Vol 71 (9) ◽  
pp. 1333-1339 ◽  
Author(s):  
A. Morvannou ◽  
N. Forquet ◽  
S. Michel ◽  
S. Troesch ◽  
P. Molle
Keyword(s):  
Constructed Wetlands ◽  
Oxygen Demand ◽  
Pollutant Removal ◽  
Vertical Flow ◽  
Removal Rates ◽  
Waste Stabilization Ponds ◽  
Small Communities ◽  
Technical Department ◽  
In Series ◽  
High Chemical Oxygen Demand

Approximately 3,500 constructed wetlands (CWs) provide raw wastewater treatment in France for small communities (<5,000 people equivalent). Built during the past 30 years, most consist of two vertical flow constructed wetlands (VFCWs) in series (stages). Many configurations exist, with systems associated with horizontal flow filters or waste stabilization ponds, vertical flow with recirculation, partially saturated systems, etc. A database analyzed 10 years earlier on the classical French system summarized the global performances data. This paper provides a similar analysis of performance data from 415 full-scale two-stage VFCWs from an improved database expanded by monitoring data available from Irstea and the French technical department. Trends presented in the first study are confirmed, exhibiting high chemical oxygen demand (COD), total suspended solids (TSS) and total Kjeldahl nitrogen (TKN) removal rates (87%, 93% and 84%, respectively). Typical concentrations at the second-stage outlet are 74 mgCOD L−1, 17 mgTSS L−1 and 11 mgTKN L−1. Pollutant removal performances are summarized in relation to the loads applied at the first treatment stage. While COD and TSS removal rates remain stable over the range of applied loads, the spreading of TKN removal rates increases as applied loads increase.

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

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

Influence of pH on the formation of organic and mineral colloïds and the associated release of various elements from surface sludge deposits of vertical flow constructed wetlands.

2020 ◽  
Author(s):  
Camille Banc ◽  
Mathieu Gautier ◽  
Blanc Denise ◽  
Lupsea-Toader Maria ◽  
Marsac Rémi ◽  
...  
Keyword(s):  
Trace Elements ◽  
Organic Matter ◽  
Constructed Wetlands ◽  
Organic Molecules ◽  
Major And Trace Elements ◽  
Vertical Flow ◽  
Colloidal Transport ◽  
Vertical Flow Constructed Wetlands ◽  
Neutralizing Capacity ◽  
Colloidal Carrier

<p>In the treatment of raw domestic wastewaters in vertical flow constructed wetlands (VFCW), a sludge layer is formed at the surface of the first-stage filters by the retention of wastewater’s suspended solids. The deposits constituting this layer is now known to accumulate and degrade a large variety of contaminants during regular conditions of operation. The potential release of the contaminants from the sludge deposits under disturbed conditions or during off-site sludge reuse is therefore a major concern. This study investigated the influence of organic colloids on the mobilization of major and trace elements bound to VFCW surface sludge deposits.   </p><p>Although the role of organic and/or mineral colloidal carrier phases in the transport of elements in natural systems has been extensively studied, little is known in contrast on the production of colloidal carrier phases from anthropic materials and media such as the sludge deposits considered here.</p><p>The acid/base neutralizing capacity (environmental assessment procedure ANC/BNC) (CEN/TS 14429) was carried out to assess the release at different pHs. Samples of sludge deposits were contacted with solutions in a wide pH range and the suspensions filtered through 0.45 µm acetate cellulose filters were subsequently analyzed. In addition, the suspensions were also treated by ultrafiltration using successively membranes of decreasing pore size (30 kDa, 10 kDa and 3 kDa). The leached organic molecules were thereby divided into three groups: (i) large colloids (30 kDa-0.45 µm), (ii) small colloids (10 kDa-3 kDa) and (iii) truly dissolved fraction (< 3 kda). The permeates were analyzed for major and trace elements and organic particles. UV-vis spectra were also recorded to evaluate organic matter aromaticity.  </p><p>Results showed that the molecular weight of the organic matter released was pH-dependent. Under very acidic conditions, the release of dissolved and poorly aromatic organic matter was mostly observed. At natural pH, close to neutrality, the sludge deposits released mostly large organic colloids. At higher pHs, the release of larger organic colloids was observed associated with an increase in the aromaticity of organic molecules.</p><p>The major and trace mineral elements released were found in the different fractions analyzed, depending on  their affinity with the organic colloidal carrier phases described previously. A first group of elements (As, P, B, V, Na, K) were mostly found in solution, and therefore poorly affected by colloidal transport regardless of pH conditions.  A second group (Co, Cu, Ni, Cd, Zn) was found to be relatively uniformly distributed in the fractions associated with the large and small colloids as well as in the dissolved fraction. A third group (Cr, Ba, Mn, Ca, Li, Mg, Sr) was mostly associated to large organic and/or mineral colloids.  </p><p>The results obtained in this study are a contribution to a better description of colloidal production and the release of associated elements and contaminants from VFCW sludge deposits. This is a key issue in the assessment of environmental risks related to the operation of the treatment plants or the reuse of the sludge material.</p>

Contaminant removal in septage treatment with vertical flow constructed wetlands operated under batch flow conditions

2015 ◽  
Vol 73 (4) ◽  
pp. 909-915 ◽  
Author(s):  
Valerie Siaw Wee Jong ◽  
Fu Ee Tang
Keyword(s):  
Constructed Wetlands ◽  
Palm Kernel ◽  
Oxygen Demand ◽  
Vertical Flow ◽  
Contaminant Removal ◽  
Efficient Operation ◽  
Palm Kernel Shell ◽  
Second Stage ◽  
Vertical Flow Constructed Wetlands ◽  
Study Results

Individual septic tanks are the most common means of on-site sanitation in Malaysia, but they result in a significant volume of septage. A two-staged vertical flow constructed wetlands (VFCWs) system for the treatment of septage was constructed and studied in Sarawak, Malaysia. Raw septage was treated in the first stage wetlands, and the resulting percolate was fed onto the second stage wetlands for further treatment. Here, the effects of a batch loading regime on the contaminant removal efficiency at the second stage wetlands, which included palm kernel shell within their filter substrate, are presented. The batch loading regime with pond:rest (P:R) period of 1:1, 2:2 and 3:3 (day:day) was studied. The improvement of the effluent redox condition was evident with P:R = 3:3, resulting in excellent organic matters (chemical oxygen demand and biochemical oxygen demand) and nitrogen reduction. The bed operated with P:R = 1:1 experienced constant clogging, with a water layer observed on the bed surface. For the P:R = 3:3 regime, the dissolved oxygen profile was not found to decay drastically after 24 hours of ponding, suggesting that the biodegradation mainly occurred during the first day. The study results indicate that a suitable application regime with an adequate rest period is important in VFCWs to ensure efficient operation.

scholarly journals Effectiveness of septage pre-treatment in vertical flow constructed wetlands

2017 ◽  
Vol 76 (9) ◽  
pp. 2544-2553 ◽  
Author(s):  
Beata Karolinczak ◽  
Wojciech Dąbrowski
Keyword(s):  
Constructed Wetlands ◽  
Municipal Wastewater ◽  
Oxygen Demand ◽  
Vegetation Period ◽  
Ammonia Nitrogen ◽  
Vertical Flow ◽  
Municipal Wastewater Treatment ◽  
Vertical Flow Constructed Wetlands ◽  
Hydraulic Load ◽  
Pre Treatment

Abstract Septage is wastewater stored temporarily in cesspools. A periodic supply of its significant quantities to small municipal wastewater treatment plants (WWTPs) may cause many operational problems. In the frame of the research, it has been proposed to utilize vertical flow constructed wetlands for pre-treatment of septage prior to its input to the biological stage of a WWTP. The aim of the work was to assess the effectiveness of pre-treatment in relation to factors such as: seasonality, hydraulic load, pollutants load of the VF bed and interactions between these factors. The results proved that application of a VF bed to septage pre-treatment can significantly reduce the concentration of pollutants (biochemical oxygen demand (BOD5): 82%, chemical oxygen demand (COD): 82%, total suspended solids (TSS): 91%, total nitrogen (TN): 47%, ammonia nitrogen (NH4-N): 70%), and thus decrease the loading of the biological stage of a WWTP. The mathematical models of mass removal process were created. They indicate that in case of all analysed parameters, removed load goes up with the increase of load in the influent. However, with the increase of hydraulic load, a decrease of the removed BOD5, COD, TSS and total phosphorus, and in vegetation period an increase of TN, can be observed in terms of load. There are no statistically significant effects of seasonality.

Nitrification in Vertical Flow Constructed Wetlands with Different Substrate and COD: N Ratio

2010 ◽  
Vol 96 ◽  
pp. 117-120 ◽  
Author(s):  
Xiao Li Han ◽  
Re Ti Hai ◽  
Wen Xin Wang
Keyword(s):  
Chemical Oxygen Demand ◽  
Constructed Wetlands ◽  
Oxygen Demand ◽  
Vertical Flow ◽  
Vertical Flow Constructed Wetlands ◽  
Peaty Soil

In this paper, the effect of chemical oxygen demand (COD) in the influent on nitrification in CWs with different substrate (peaty soil and turfy soil) was investigated. The results indicate that the influence of the substrate is insignificant but the COD: N ratio in the influent affects nitrification mainly.

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

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

scholarly journals Lampiran 1G Paper The Use of Pumice Amended with Sand Media for Domestic Wastewater Treatment in Vertical Flow Constructed Wetlands Planted with Lemongrass (Cymbopogon citratus)

2021 ◽  
Author(s):  
Philiphi de Rozari
Keyword(s):  
Organic Matter ◽  
Removal Efficiency ◽  
Constructed Wetlands ◽  
Suspended Solids ◽  
Domestic Wastewater ◽  
Vertical Flow ◽  
X Ray Diffraction ◽  
Cymbopogon Citratus ◽  
Domestic Wastewater Treatment ◽  
The Media

The performance efficiency in constructed wetlands (CWs) technology is primarily affected by the media material and the types of plants used. Recently, investigations into the usage of local materials and plants in CWs has increased. Pumice is a material which is potential used as a media. However, research on amendment of pumice with other media in CWs is still limited. Therefore, this study aims to evaluate the potential of pumice amended with sand media and planted with lemongrass (Cymbopogon citratus) in CWs to remove organic matter, suspended solids, nutrients, and coliform. The adsorbents were characterized using X-ray diffraction, FTIR and XRF followed by adsorption experiments for PO4–P. Furthermore, Six vertical flow (VF) mesocosms with a diameter of 10.2cm and 55cm depth were established over six months. The treatments were based on percentage of sand media amended with pumice and planted with lemongrass. Furthermore, the barren media were applied to investigate the effect of lemongrass. The loading rate of domestic wastewater into the VF mesocosms was 2 L/day while inflows and outflows were determined for nutrients, organic matter, suspended solids and coliform. The adsorption of PO4–P followed the Langmuir model with adsorption capacity was 0.089 and 0.067 mol/g for pumice and sand, respectively. The results also showed that the removal efficiency of TSS, COD, NO3–N, NO2–N, PO4–P and total coliforms were in the range of 93.7–97.3 %, 52–83 %, 63–86 %, 51–74%, 81–88 % and 92–97 %, respectively. Based on the results, the highest removal efficiency was observed in the sand media amended with 50 % pumice and planted with lemongrass, while the lowest was found in the barren sand media.

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