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.

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.

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>

Removal efficiency of subsurface vertical flow constructed wetlands for different organic loads

2007 ◽  
Vol 56 (3) ◽  
pp. 75-84 ◽  
Author(s):  
G. Langergraber ◽  
C. Prandtstetten ◽  
A. Pressl ◽  
R. Rohrhofer ◽  
R. Haberl
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Constructed Wetlands ◽  
Specific Surface Area ◽  
Nitrogen Concentration ◽  
Specific Area ◽  
Ammonia Nitrogen ◽  
Vertical Flow ◽  
Design Standards ◽  
Vertical Flow Constructed Wetlands

Using subsurface vertical flow constructed wetlands (SSVFCWs) with intermittent loading it is possible to fulfil the stringent Austrian effluent standards regarding nitrification. For small plants (less than 500 persons) standards for ammonia nitrogen concentration have to be met at water temperatures higher than 12 °C, effluent concentrations and treatment efficiencies for organic matter have to be met the whole year around. According to the Austrian design standards the required surface area for SSVFCWs treating wastewater was 5 m2 per person. Within the first part of an Austrian research project the goal was to optimise, i.e. minimise the surface area requirement of vertical flow beds. Therefore, three SSVFCWs with a surface area of 20 m2 each have been operated in parallel. The organic loads applied were 20, 27 and 40 g COD/m2/d, which corresponds to a specific surface area requirement of 4, 3 and 2 m2 per PE, respectively. The paper compares the effluent concentrations and elimination efficiencies of the three parallel operated beds. It could be shown that a specific area demand of 4 m2 per person is suitable to be included in the revision of the Austrian design standard. Additionally it could be shown that during the warmer seasons (May–October) when the temperature of the effluent is higher than 12 °C the specific surface area might be further reduced; even 2 m2 per person has been proven to be adequate.

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.

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.

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.

scholarly journals French vertical-flow constructed wetlands in mountain areas: how do cold temperatures impact performances?

2015 ◽  
Vol 71 (8) ◽  
pp. 1219-1228 ◽  
Author(s):  
S. Prost-Boucle ◽  
O. Garcia ◽  
P. Molle
Keyword(s):  
Constructed Wetlands ◽  
Nitrogen Removal ◽  
Winter Season ◽  
Oxygen Demand ◽  
Vertical Flow ◽  
Mountain Areas ◽  
Cold Temperatures ◽  
Vertical Flow Constructed Wetlands ◽  
Online Measurements ◽  
Solids Removal

The French version of vertical-flow constructed wetlands (VFCWs) is characterized by treating directly raw wastewater on a first-stage filter. VFCW is a well developed technology with more than 3,500 plants in operation in France. However, VFCW performance may be affected under the low temperatures reached in mountain areas during winter. The effect of cold conditions over 12 plants, ranging from 75 to 1,900 person equivalent and from 680 to 1,500 m above sea level, was studied over 2 years. The plant hydraulic loads, and air and filter temperatures were continuously measured. In addition, 24-h flow proportional sampling, at each stage of treatment, was conducted in summer (as a reference) and winter. Online measurements of ammonium and nitrates were also analyzed to describe the nitrogen removal dynamics. Since no impact on chemical oxygen demand (COD), biochemical oxygen demand (BOD) and suspended solids removal was observed, the effect of cold temperatures on nitrification was further analyzed. Nitrogen removal was relatively unaffected during winter season. Significant effects were confirmed only for the second stage for loads above 10 gTKN/m2/d (TKN: total Kjeldahl nitrogen). Temperature profiles allowed analysis of the filter buffer capacity in terms of freezing. Under minimal air temperature of −19 °C, no critical operation was observed, although design and operation recommendations can be provided to ensure suitable plant performances.

scholarly journals Hybrid Constructed Wetland to Improve Organic Matter and Nutrient Removal

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2023
Author(s):  
M. I. Fernandez-Fernandez ◽  
P. T. Martín de la Vega ◽  
M. A. Jaramillo-Morán ◽  
M. Garrido
Keyword(s):  
Organic Matter ◽  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Small Businesses ◽  
Primary Treatment ◽  
Small Towns ◽  
Vertical Flow ◽  
Urban Agglomerations ◽  
Vertical Flow Constructed Wetlands ◽  
Agricultural Industries

Constructed wetlands are one of the best technologies for wastewater treatment in small towns, small businesses or farms and/or livestock breeding. In this work, a wastewater depuration ecological system implemented in a hybrid constructed wetland to remove nutrients and organic matter from small urban agglomerations is studied. It comprises two processing stages: a primary treatment carried out in two hydrolytic up-flow sludge bed digesters working in parallel and a secondary one made up of two vertical flow constructed wetlands, which are alternatively used, followed by a horizontal flow constructed wetland. An internal recirculation system connects the output of the vertical flow constructed wetlands to the input of the hydrolytic up-flow sludge bed digesters with the aim of promoting the nitrification-denitrification process. High nutrients and organic matter removal efficiencies were observed when treating highly polluted wastewater from an animal farm. Therefore, this ecological depuration system, designed with an internal recirculation to enhance nitrogen reduction, may be considered an efficient alternative to treat wastewater from small urban agglomerations and diffuse contamination from agricultural industries and livestock farms polluting surface waters with nitrates, which may cause serious environmental problems, such as eutrophication.

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