Changes in the nitrification-denitrification capacity of pilot-scale partially saturated vertical flow wetlands (with corncob in the free-drainage zone) after two years of operation

The aim of this 15-month study was to evaluate and compare two partially saturated (PS) vertical flow (VF) wetlands for total nitrogen (TN) removal. The PS VF wetlands, evaluated in duplicate, were added with corncob (CC) in two different heights of the free-drainage zone (FDZ). The FDZ had a height of 40 cm and the saturated zone (SZ) had a height of 30 cm. The configuration of the system I (SI) was a 20 cm-corncob bed above the SZ followed by a 20 cm-tezontle bed; in system II (SII) the order of the beds were inverted. The SZ was added with tezontle with a size of 1−2 cm. Weekly measurements of water quality parameters including oxygen demand (BOD5), chemical oxygen demand (COD), color, total suspended solids (TSS), organic nitrogen (Org-N), ammonium (NH4+), nitrate (NO3−) and nitrite (NO2−), were taken in the influent and effluents, and interfaces (nitrate and nitrite). Measurements of pH, dissolved oxygen (DO) and oxidation-reduction potential (ORP) were taken in the SZ. The addition of CC in the FDZ did not interfere with the capacity of the PS VF wetlands for BOD5, COD, TSS and true color removal, reaching mass removal efficiencies of 91.9% and 92.2%, 66.6% and 75%, 89.8% and 92%, 63.3% and 66.0%, for SI and SII, respectively; without significant difference between the systems (p > 0.05). The CC in the FDZ neither interfered with the PS VF wetlands nitrification capacity. The removal of TN was similar in SI and SII (p > 0.05), attaining average mass removal efficiencies of 68.2% and 66.0%, respectively. These efficiencies were not sufficiently high due to the limited denitrification process in the SZ as a result of the absence of biodegradable carbon, generated and consumed in the FDZ.

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Pilot-scale study of vertical flow constructed wetland combined with trickling filter and ferric chloride coagulation: influence of irregular operational conditions

Water Science & Technology ◽

10.2166/wst.2015.077 ◽

2015 ◽

Vol 71 (7) ◽

pp. 1088-1096 ◽

Cited By ~ 4

Author(s):

B. Kim ◽

M. Gautier ◽

G. Olvera Palma ◽

P. Molle ◽

P. Michel ◽

...

Keyword(s):

Constructed Wetland ◽

Phosphorus Removal ◽

Water Saturation ◽

Oxygen Demand ◽

Pilot Scale ◽

Saturation Level ◽

Vertical Flow ◽

Trickling Filter ◽

Operational Conditions ◽

Vertical Flow Constructed Wetland

The aim of this study was to characterize the efficiency of an intensified process of vertical flow constructed wetland having the following particularities: (i) biological pretreatment by trickling filter, (ii) FeCl3 injection for dissolved phosphorus removal and (iii) succession of different levels of redox conditions along the process line. A pilot-scale set-up designed to simulate a real-scale plant was constructed and operated using real wastewater. The influences of FeCl3 injection and water saturation level within the vertical flow constructed wetland stage on treatment performances were studied. Three different water saturation levels were compared by monitoring: suspended solids (SS), total phosphorus (TP), dissolved chemical oxygen demand (COD), ammonium, nitrate, phosphate, iron, and manganese. The results confirmed the good overall efficiency of the process and the contribution of the trickling filter pretreatment to COD removal and nitrification. The effects of water saturation level and FeCl3 injection on phosphorus removal were evaluated by analysis of the correlations between the variables. Under unsaturated conditions, good nitrification and no denitrification were observed. Under partly saturated conditions, both nitrification and denitrification were obtained, along with a good retention of SSs. Finally, under saturated conditions, the performance was decreased for almost all parameters.

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Small wastewater treatment plants in Flanders (Belgium): standard approach and experiences with constructed reed beds

Water Science & Technology ◽

10.2166/wst.2000.0010 ◽

2000 ◽

Vol 41 (1) ◽

pp. 57-63 ◽

Cited By ~ 7

Author(s):

S. Vandaele ◽

C. Thoeye ◽

B. Van Eygen ◽

G. De Gueldre

Keyword(s):

Wastewater Treatment ◽

Removal Efficiency ◽

Wastewater Treatment Plants ◽

Treatment Plant ◽

Pilot Scale ◽

Surface Flow ◽

Limiting Factor ◽

Vertical Flow ◽

Reed Beds ◽

Reed Bed

In Flanders (Belgium) an estimated 15% of the population will never be connected to a central wastewater treatment plant (WWTP). Small WWTPs can be a valuable option. Aquafin bases the decision to build SWWTPs on a drainage area study. To realise an accelerated construction the process choice is made accordingly to a standard matrix, which represents the different technologies in function of the size and the effluent consents. A pilot scale constructed two-stage reed bed is used to optimise the concept of the reed beds. The concept consists of a primary clarifier, two parallel vertical flow reed beds followed by a sub-surface flow reed bed. The removal efficiency of organic pollutants is high (COD: 89%, BOD: 98%). Phosphorus removal is high at the start-up but diminishes throughout the testing period (from 100% to 71% retention after 7 months). Nitrogen removal amounts to 53% on average. Nitrification is complete in summer. Denitrification appears to be the limiting factor. In autumn leakage of nitrogen is assumed. Removal efficiency of pathogens amounts to almost 99%. Clogging forms a substantial constraint of the vertical flow reed bed. Problems appear to be related with presettlement, feed interval and geotextile.

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Optimization of subsurface vertical flow constructed wetlands for wastewater treatment

Water Science & Technology ◽

10.2166/wst.2007.129 ◽

2007 ◽

Vol 55 (7) ◽

pp. 71-78 ◽

Cited By ~ 16

Author(s):

G. Langergraber ◽

Ch. Prandtstetten ◽

A. Pressl ◽

R. Rohrhofer ◽

R. Haberl

Keyword(s):

Grain Size ◽

Specific Surface ◽

Surface Area ◽

Constructed Wetlands ◽

Organic Load ◽

Vertical Flow ◽

Two Stage ◽

Main Layer ◽

Free Drainage ◽

Stage System

Constructed wetlands (CWs) use the same processes that occur in natural wetlands to improve water quality and are used worldwide to treat different qualities of water. This paper shows the results of an Austrian research project having the main goals to optimize vertical flow beds in terms of surface area requirement and nutrient removal, respectively. It could be shown that a subsurface vertical flow constructed wetland (SSVFCW) operated with an organic load of 20 g COD.m−2.d−1 (corresponding to a specific surface area demand of 4 m2 per person) can fulfil the requirements of the Austrian standard regarding effluent concentrations and removal efficiencies. During the warmer months (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 have been proven to be adequate. Enhanced nitrogen removal of 58 % could be achieved with a two-stage system (first stage: grain size for main layer 1–4 mm, saturated drainage layer; and second stage: grain size for main layer 0.06–4 mm, free drainage) that was operated with an organic load of 80 g COD.m−2.d−1 for the first stage (1 m2 per person), i.e. 40 g COD.m−2.d−1 for the two-stage system (2 m2 per person). Although the two-stage system was operated with higher organic loads a higher effluent quality compared to a single-stage SSVFCW (grain size for main layer 0.06–4 mm, free drainage, organic load 20 g COD.m−2.d−1) could be reached.

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