Elevated Vertical-Flow Constructed Wetlands for Light Greywater Treatment

Integrated planning of urban blue–green infrastructures is crucial to strengthen urban environmental quality and mitigate negative climate change-associated effects. It implies, however, increased water demand for irrigation, wherefore greywater (wastewater excluding wastewater from toilets and urinals) can be used, yet it requires handling for safe reuse. One treatment option is the use of constructed wetlands (CW), which have thus far not been broadly applied in inner-city districts due to large area requirements. This work investigates a novel bipartite container-based vertical-flow constructed wetland (VFCW) for the treatment of light greywater (from showers and hand wash basins) and its use as irrigation water for urban facade greenery. The VFCW consists of two compartments with 2.5 m2 filter area each, filled with 75 cm zeolite-containing lava sand (0–4 mm) and 75 cm Rhine sand (0–2 mm), respectively. In short, screening has proven to be well suitable for coarse solids removal, so there is no further need to settle light greywater, which reduces overall treatment area and benefits urban application. Treated greywater complied with irrigation standards at all times, yet mixing with rainwater can help reduce salt contents, if applicable. The modular/elevated lava sand VFCW exhibited extensive nitrification, even at extremely low water temperatures, as well as mean effluent concentrations of 6.3 mg/L COD and <0.05 mg/L Ptot, which makes it a very promising treatment option for greywater. All in all, the modular/elevated design promotes urban application of VFCW as a multifunctional blue–green system that can help increase urban resilience.

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Performance evaluation of horizontal and vertical flow constructed wetlands as tertiary treatment option for secondary effluents

Applied Water Science ◽

10.1007/s13201-019-1014-9 ◽

2019 ◽

Vol 9 (6) ◽

Cited By ~ 5

Author(s):

Arun Kumar Thalla ◽

C. P. Devatha ◽

K. Anagh ◽

Elsa Sony

Keyword(s):

Performance Evaluation ◽

Constructed Wetlands ◽

Treatment Option ◽

Vertical Flow ◽

Tertiary Treatment ◽

Vertical Flow Constructed Wetlands ◽

Secondary Effluents

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

Water Science & Technology ◽

10.2166/wst.2015.074 ◽

2015 ◽

Vol 71 (8) ◽

pp. 1219-1228 ◽

Cited By ~ 5

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.

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Wavy Subsurface Flow and Vertical Flow Constructed Wetlands: Effects of Aeration and Wastewater Composition on Wetland Clogging

Journal of Environmental Engineering ◽

10.1061/(asce)ee.1943-7870.0000948 ◽

2015 ◽

Vol 141 (9) ◽

pp. 04015018 ◽

Cited By ~ 4

Author(s):

Yongzheng Ren ◽

Qilong Gong ◽

Tian C. Zhang ◽

Jianxiong Kang ◽

Dongqi Liu

Keyword(s):

Constructed Wetlands ◽

Subsurface Flow ◽

Vertical Flow ◽

Vertical Flow Constructed Wetlands

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Treatment performances of French constructed wetlands: results from a database collected over the last 30 years

Water Science & Technology ◽

10.2166/wst.2015.089 ◽

2015 ◽

Vol 71 (9) ◽

pp. 1333-1339 ◽

Cited By ~ 30

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.

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Experiences with a top layer of gravel to enhance the performance of vertical flow constructed wetlands at cold temperatures

Water Science & Technology ◽

10.2166/wst.2009.085 ◽

2009 ◽

Vol 59 (6) ◽

pp. 1111-1116 ◽

Cited By ~ 2

Author(s):

Guenter Langergraber ◽

Alexander Pressl ◽

Klaus Leroch ◽

Roland Rohrhofer ◽

Raimund Haberl

Keyword(s):

Organic Matter ◽

Constructed Wetlands ◽

Common Reed ◽

Treated Wastewater ◽

Second Phase ◽

Vertical Flow ◽

Cold Temperatures ◽

Main Layer ◽

Gravel Layer ◽

Filter Bed

In a first phase of this study it was shown that the Austrian effluent standards for organic matter could not be met in winter for vertical flow (VF) beds designed for and loaded with 27 g COD.m−2.d−1 (3 m2 per person equivalent). The aim of this second phase of the study was to investigate, if the performance of a constructed wetland can be enhanced, i.e. if the effluent requirements can be met, when an additional gravel layer (15 cm, 4–8 mm) is added on top of the main layer of the VF bed. The hypothesis was that this top layer would increase the thermal insulation and consequently the temperatures in the filter bed during cold periods, thus resulting in higher removal efficiencies during winter. Two VF beds were operated in parallel; one bed with such a 15 cm top layer, one without. Otherwise the construction of both beds was identical: surface area of about 20 m2, 50 cm main layer (grain size 0.06–4 mm, d10=0.2 mm; d60=0.8 mm), planted with common reed (Phragmites australis). The beds were intermittently loaded 4 times per day with mechanically pre-treated wastewater (hydraulic loading: 47 mm.d−1; median value of the influent concentration: 505 mg COD.L−1). Despite a better performance during the first winter, the bed with additional top layer showed in general a very unstable performance. It is assumed that the main reason for this was that the oxygen transfer was reduced by the additional top layer so far that suspended organic matter could not any longer be degraded in between loadings. Therefore clogging of the filter occurred.

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Behaviour of 27 Selected Emerging Contaminants in Vertical Flow Constructed Wetlands as Post-Treatment for Municipal Wastewater

SSRN Electronic Journal ◽

10.2139/ssrn.3970770 ◽

2021 ◽

Author(s):

Silvia Venditti ◽

Hana Brunhoferova ◽

Joachim Hansen

Keyword(s):

Constructed Wetlands ◽

Emerging Contaminants ◽

Municipal Wastewater ◽

Post Treatment ◽

Vertical Flow ◽

Vertical Flow Constructed Wetlands

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Comparative characterization of surface sludge deposits from fourteen French Vertical Flow Constructed Wetlands sewage treatment plants using biological, chemical and thermal indices

The Science of The Total Environment ◽

10.1016/j.scitotenv.2018.07.440 ◽

2019 ◽

Vol 647 ◽

pp. 464-473 ◽

Cited By ~ 8

Author(s):

M. Kania ◽

M. Gautier ◽

A. Imig ◽

P. Michel ◽

R. Gourdon

Keyword(s):

Constructed Wetlands ◽

Sewage Treatment ◽

Vertical Flow ◽

Thermal Indices ◽

Sewage Treatment Plants ◽

Comparative Characterization ◽

Vertical Flow Constructed Wetlands

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Using one filter stage of unsaturated/saturated vertical flow filters for nitrogen removal and footprint reduction of constructed wetlands

Water Science & Technology ◽

10.2166/wst.2017.115 ◽

2017 ◽

Vol 76 (1) ◽

pp. 124-133 ◽

Cited By ~ 4

Author(s):

Ania Morvannou ◽

Stéphane Troesch ◽

Dirk Esser ◽

Nicolas Forquet ◽

Alain Petitjean ◽

...

Keyword(s):

Constructed Wetlands ◽

Oxygen Demand ◽

Pollutant Removal ◽

Operating Conditions ◽

Vertical Flow ◽

Saturated Layer ◽

Recirculation Rate ◽

Total Filtration ◽

Filtration Area ◽

Stage System

French vertical flow constructed wetlands (VFCW) treating raw wastewater have been developed successfully over the last 30 years. Nevertheless, the two-stage VFCWs require a total filtration area of 2–2.5 m2/P.E. Therefore, implementing a one-stage system in which treatment performances reach standard requirements is of interest. Biho-Filter® is one of the solutions developed in France by Epur Nature. Biho-Filter® is a vertical flow system with an unsaturated layer at the top and a saturated layer at the bottom. The aim of this study was to assess this new configuration and to optimize its design and operating conditions. The hydraulic functioning and pollutant removal efficiency of three different Biho-Filter® plants commissioned between 2011 and 2012 were studied. Outlet concentrations of the most efficient Biho-Filter® configuration are 70 mg/L, 15 mg/L, 15 mg/L and 25 mg/L for chemical oxygen demand (COD), 5-day biological oxygen demand (BOD5), total suspended solids (TSS) and total Kjeldahl nitrogen (TKN), respectively. Up to 60% of total nitrogen is removed. Nitrification efficiency is mainly influenced by the height of the unsaturated zone and the recirculation rate. The optimum recirculation rate was found to be 100%. Denitrification in the saturated zone works at best with an influent COD/NO3-N ratio at the inflet of this zone larger than 2 and a hydraulic retention time longer than 0.75 days.

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