Constructed Wetland Units Research Articles

Hyperspectral monitoring of a constructed wetland as a tertiary treatment in a wastewater treatment plant

Hyperspectral sensing devices are being increasingly applied in the field of environmental monitoring. High spatial and spectral resolution hyperspectral data are particularly suited for detecting the vegetation health state due to the unique spectral characteristics exhibited by green plants. Wetlands are capable of filtering polluted water, with their functionality strictly related to the health state of the plants bedded out in the lagoon. This paper presents a ground spectroscopy monitoring survey of the vegetation implanted in the constructed wetland unit located in the wastewater treatment plant for domestic sewage of Latina Mare. The measurement campaign was carried out through the collection of hyperspectral data by means of a spectroradiometer. Broadband indices of vegetation were computed from the data acquired to infer the plant health state. For the test case discussed in this contribution, there is a remarkable agreement between data acquired and the observations at the ground. The broadband indices Red Difference Vegetation Index, Simple Ratio and Transformed Vegetation Index make it possible to highlight the vegetation health state in the investigated wetland unit. Removal efficiency of the unit well reflected the values of the indices.

Application of integrated local plant species and vesicular basalt rock for the treatment of chromium in tannery wastewater in a horizontal subsurface flow wetland system

In this study, integrated local plant species and vesicular basalt were used in the constructed units with a horizontal subsurface flow wetland system to investigate the removal efficiency of chromium in tannery wastewater. Four pilot units were vegetated with Pennisetum purpureum, Typha domingensis, Cyprus latifolius, and Echinochloa pyramidalis, and a fifth unit was left unvegetated (control). The constructed wetland units vegetated with P. purpureum and C. latifolius were effective in removing chromium up to 99.38 % and 99.21 % respectively in the 6 days of hydraulic retention time. All the constructed wetland units were effective in removing chromium from the tannery wastewater and there was no statistically significant difference between the vegetated and control units. The plant species used for removal of Cr (III) indicated bioconcentration factor >1 and translocation factor <1. Based on its rapid growth and biomass production, P. purpureum can accumulate more Cr (III) in its above-ground parts compared to the other three plant species. The integrated horizontal subsurface flow wetland units indicated high treatment potential of chromium (III) in the tannery wastewater, which is below the standard discharge limit set to surface water bodies (2 mg L−1) according to Ethiopia EPA.

Efficiency of constructed wetlands in treating E. coli bacteria present in livestock wastewater

Constructed wetlands are artificial wetland units, designed for adopting the principle of natural wetlands for purifying wastewater. Well-designed and well-constructed wetlands play an important role not only in reduction in organic compound/impurities, but also in coliform reduction in wastewater. The three small laboratory-scale units were control, Typha and plant species design based on USEPA procedure. The plant species are watered for a few days to promote their stable growth. Then, the three wetland units were seeded with livestock wastewater from a nearby cattle farm. Qualitative analysis by polymerase chain reaction and quantitative analysis are carried out by doing microbial culture in selective medium of MacConkey agar. The E. coli load is monitored before and after treatment in all the three units with different trials. It is found to be at a higher level in Typha unit after 24 h than in mixed and control units. The sample from the bottom of the constructed wetland unit is withdrawn and cultured for five days, and the bacterial load is found to be 9 × 104. Meanwhile, considerable reduction is observed in the Typha wetland unit after 5 days, and the bacterial load is 4 × 102. Mixed species wetland shows excellent treatment efficiency, and the bacterial load (E. coli) is very less after 5 days. It is evident from the study that constructed wetlands are effective in the treatment of E. coli bacteria wetland plants which are used for treatment.

S-metolachlor herbicide removal in pilot-scale horizontal subsurface flow constructed wetlands

The aim of this study was to explore the efficiency of three horizontal subsurface flow (HSF) constructed wetlands (CWs) to remove S-metolachlor from contaminated water. The three CWs, with code names MG-R, MG-C and MG-Z, all contained medium gravel as porous media. MG-R and MG-C were planted with Phragmites australis and Typha latifolia, respectively, and MG-Z was left unplanted and used as control unit to study the effect of vegetation. The CWs units in this experiment operated continuously for one year but they were mature systems operating in various experiments for more than fourteen years. The results showed that the mean percent S-metolachlor removal values were 68.9%, 47.8% and 40.8% for MG-R, MG-C and MG-Z units, respectively. The vegetation (Phragmites australis) and the hydraulic residence time were found as the most important parameters affecting the CW capacity in herbicide removal. The current data suggest that HSF CWs are an efficient and low-cost technology in treating S-metolachlor-contaminated surface runoff in agricultural areas.

Nitrogen removal and recovery from lagoon-pretreated swine wastewater by constructed wetlands under sustainable plant harvesting management

A series of three-stage pilot-scale surface flow constructed wetlands (CWs) planted with Myriophyllum aquaticum were fed with three strengths of lagoon-pretreated swine wastewater to study nitrogen (N) removal and recovery under sustainable plant harvesting management. The CWs had mean removal efficiency of 87.7–97.9% for NH4+-N and 85.4–96.1% for total N (TN). The recovered TN mass via multiple harvests of M. aquaticum was greatest (120–222 g N m−2 yr−1) when TN concentrations were 21.8–282 mg L−1. The harvested TN mass accounted for 0.85–100% of the total removal in the different CW units. Based on mass balance estimation, plant uptake, sediment storage, and microbial removal accounted for 13.0–55.0%, 4.9–8.0%, and 33.0–67.5% of TN loading mass, respectively. The results of this study confirm that M. aquaticum is appropriate for the removal and recovery of nutrients in CW systems designed for treating swine wastewater in conjunction with sustainable plant harvesting strategies.

Modified Soil Compositions for Removal of Acetaminophen from Wastewater

ACT is a widely used prescriptive drug for analgesic treatment. Due to incomplete conversion of ACT in the body, a significant portion of it is released with human excreta. Most wastewater treatment plants lack the efficiency to treat influent containing ACT residues. As a result, risk of surface and groundwater contamination has been increased. Constructed wetlands (CWs) are one of the widely used natural wastewater treatment technologies, employing soil-plant interactions in treating pollutants through a number of reactions such as plant uptake, ion adsorption and advanced Fenton reaction. In addition, the wetland plants are well-known to generate H2O2 in the surrounding rhizosphere for advanced oxidation process. In this study, the potential of laterite soil in initiating Fenton reactions by its abundant composition of iron (Fe) and its modified structure with activated carbon, cement and crushed shellfish (modified soil) were evaluated for ACT treatment. The induced H2O2 soil environment in the constructed wetland units could remove almost 80% of the ACT present initially. The results showed good occurrence of Fenton process on both natural laterite soil and modified media bed (cement: laterite soil fine: 50% laterite soil coarse: 50% activated carbon).

A novel horizontal subsurface flow constructed wetland: Reducing area requirements and clogging risk

The use of Constructed Wetlands (CWs) has been nowadays expanded from municipal to industrial and agro-industrial wastewaters. The main limitations of CWs remain the relatively high area requirements compared to mechanical treatment technologies and the potential occurrence of the clogging phenomenon. This study presents the findings of an innovative CW design where novel materials were used. Four pilot-scale CW units were designed, built and operated for two years. Each unit consisted of two compartments, the first of which (two thirds of the total unit length) contained either fine gravel (in two units) or random type high density polyethylene (HDPE) (in the other two units). This plastic media type was tested in a CW system for the first time. The second compartment of all four units contained natural zeolite. Two units (one with fine gravel and one with HDPE) were planted with common reeds, while the other two were kept unplanted. Second cheese whey was introduced into the units, which were operated under hydraulic residence times (HRT) of 2 and 4 days. After a two-year operation and monitoring period, pollutant removal rates were approximately 80%, 75% and 90% for COD, ammonium and ortho-phosphate, respectively, while temperature and HRT had no significant effect on pollutant removal. CWs containing the plastic media achieved the same removal rates as those containing gravel, despite receiving three times higher hydraulic surface loads (0.08 m/d) and four times higher organic surface loads (620 g/m2/d). This reveals that the use of HDPE plastic media could reduce CW surface area requirements by 75%.

Rhizofiltration of a Bordeaux mixture effluent in pilot-scale constructed wetland using Arundo donax L. coupled with potential Cu-ecocatalyst production

Rinsing tanks of crop sprayers produce significant volumes of Cu-rich Bordeaux mixture effluents (BME) that can be treated by rhizofiltration in constructed wetlands (CWs). A pilot-scale CW (6×600L) was developed to jointly rhizofiltrate such BME, produce Cu-rich root mat for ecocatalysis and provide usable shoot biomass with low Cu concentration. Three CW units were unplanted control (Ctrl) while three others were planted with Arundo donax L. (Ad) in floating racks. The rhizofiltration was carried out during 30days in the early growing season. Total Cu concentration in the BME was 4.4mgCuL−1. Copper removal peaked within the 48 first hours after Bordeaux mixture addition in the Ad and Ctrl units (i.e. 92 and 81% respectively). The BME Cu concentration met the requirement for indirect discharge of chemical industry effluents (i.e. 0.5mgCuL−1) at T48h (0.4±0.2) and T21days (0.4±0.1) for the Ad and Ctrl units, respectively. At day 30, in the Ad units, Cu concentration remaining in the water and distributed between A. donax roots, shoots was respectively 3.5, 33 and 0.5% of the initial Cu input. In the Ctrl units, Cu remaining in water was low (7%) and Cu removal (93%) could be partly explained by its immobilization in the Cu-rich biofilm (i.e. 207210±18516mgCukg−1) coating the vat wall. Foliar chlorophyll (i.e. a, b and total) and carotenoid contents decreased at day 30 but root and shoot dry weight (DW) yields increased by 23% and 47% per Ad unit, respectively. The shoot Cu concentration remained in the common range (i.e. 3–20mgCukg−1) while the root Cu concentration reached 623±140mgkg−1 allowing 786mg Cu removal by the root mat. Higher Cu concentration in BME or subsequent repetitions of treatment cycle must be tested to achieve at least 1000mgCukg−1 DW in roots (threshold value for Cu-ecocatalyst) whereas the biofilm role must deserve more attention.

KINERJA SUBSURFACE CONSTRUCTED WETLAND MULTYLAYER FILTRATION TIPE ALIRAN VERTIKAL DENGAN MENGGUNAKAN TANAMAN AKAR WANGI (Vetivera Zozanoides) DALAM PENYISIHAN BOD DAN COD DALAM AIR LIMBAH KANTIN

Wastewater from the canteen is a domestic wastewater that has high concentrations of organic matter that needs to be processed before being released and not contaminating the water stream. The wastewater treatment at canteen SMA Negeri 34 Jakarta begins with collecting basin and aeration basin, and then it is pumped into two reactor that is the subsurface constructed wetland multilayers filtration type flow vertical with Vetiver Grass unit (SCW-MLF) and multilayers filtration type flow vertical unit without plants (MLF) as a control. The purpose of this study was to test the effectiveness of the vetiver grass in wastewater treatment with subsurface constructed wetland unit multilayers filtration type vertical flow with vetiver grass to fulfill effluent standards before it is released into stream water. Metodology of the study was conducted from acclimatization of plants, removal the plant to the SCW-MLF unit, and analyze the quality of wastewater. Flowrate that goes into the processing unit is 6.9615 m3/day. The detention time in SCW-MLF unit was 17.7 hours. The results showed that at steady state COD organic loading on SCW-MLF unit is 917.08 to 4126.84 kg COD/ha/day for the removal efficiency around 69.2 to 80.0%, BOD organic loading is 309.78 to 850,73 kg BOD/ha/day for the removal efficiency 61.2 to 70.8%. K value SCW-MLF unit around 0.55 to 0.71 m/day for BOD, 0.57 to 0.89 m /day for COD. The concentration of the wastewater effluent from WWTP are complied to effluent standart regulation (Pergub DKI Jakarta No. 112 Tahun 2005).

Methanogenic activity of accumulated solids and gas emissions from planted and unplanted shallow horizontal subsurface flow constructed wetlands

Anaerobic processes play an important role in horizontal subsurface flow (HSSF) constructed wetlands (CW) and methane generation contributes to overall greenhouse gas emissions. Plants and bed depth are two main factors that can influence anaerobic processes but the effect of plants’ presence and species on methane emissions on shallower HSSF (0.3m bed depth) has not been studied. We measured CH4 and CO2 emissions from a pilot plant constituted of five HSSF units in parallel with different plant species (CW1-UN: unplanted, CW2-JE: Juncus effusus, CW3-IP: Iris pseudacorus, CW4-TL: Typha latifolia L. and CW5-PA: Phragmites australis). Shallow HSSF beds showed high methane emissions (averaging 440mgCH4/m2*d) even at low loading rates (<5.0gBOD5/m2*d). Differences in mean emissions between units were not significant. However, the unplanted unit showed lower methane emissions during cold periods and higher emissions during warmer periods than planted units. Temperature was the main variable determining CO2 and CH4 emission for all units, except for CO2 emissions in CW2-JE unit. Temperature models explained 63–98% of seasonal variability and predicted zero emissions of CH4 and CO2 at temperatures of 9±1°C and 7.6±1.3°C, respectively. Organic matter accumulation (volatile solids, VS), specific methanogenic activity (SMA) and methane potential (MP) of accumulated solids were also determined. None of these parameters showed significant differences among CW units, except the higher values of MP in CW2-JE unit. While VS content and minimum SMA clearly increased with operation time, maximum SMA and MP remained stable. Potential methane emissions can be estimated from the product of surface density of VS and SMA, the measured emissions fitting well in the estimated range from batch assays.

Effects of design and operational parameters on ammonium removal by single-stage French vertical flow filters treating raw domestic wastewater

Four pilot-scale single-stage vertical flow filters (of 2.25m2 each), treating raw domestic sewage, were studied over 20 months in order to assess the impact of different designs and operational conditions on treatment efficiency. One of them was designed and operated as a standard 1st stage “French” vertical flow constructed wetland unit. The other 3 pilots differed from the standard pilot with respect to the filtration depth, the loading rate or the partial replacement of gravel by zeolite (chabazite), respectively. The pilots were monitored by analysing 24-h flow-weighted composite samples for TSS, CODtot, CODd, ammonium, nitrate and carbonate. All pilots showed a high ability to remove TSS and CODtot, with average removal of 81% and 75%, respectively. Increasing the depth of the filtration layer from 40 to 100cm allowed to significantly improve ammonium removal (81%), whereas the simultaneous increase in hydraulic and organic loads resulted in a deterioration of ammonium and CODd removals (44% for both parameters). Using zeolite did not induce any observable improvements in ammonium removal under the conditions of the study.

Effect of operational and design parameters on performance of pilot-scale horizontal subsurface flow constructed wetlands treating university campus wastewater.

Three horizontal subsurface flow (HSF) pilot-scale constructed wetland (CW) units operated for 3years treating municipal wastewater originating from a university campus. The main objective of the study was the evaluation of the performance of these systems under several operational, design, and climatic conditions. Several parameters and factors were investigated, including the influence of temperature, vegetation, and hydraulic residence time. The results were compared to those of a previous study conducted in the same pilot-scale units and under the same operational conditions where synthetic municipal wastewater was used. Results show the satisfying overall performance of the CW units. Performance seems to be influenced by vegetation, temperature, and hydraulic residence time (HRT). The planted units produced better results than the unplanted one while, generally, all units operated better under warmer conditions. In addition, longer HRTs contributed to higher removal efficiencies. Finally, the systems showed higher removal efficiencies in the previous study (synthetic wastewater) regarding organic matter removal, while for the other pollutants, the present study (real wastewater) showed higher or comparable performance in most cases and especially in the planted units. The study also shows the overall good, continuous, and long-term operation of CW systems, since these systems operate for about 13years.

Removal of Endocrine Disrupting Chemicals in HSF and VF pilot-scale constructed wetlands

During the last decade, several emerging chemicals, also referred as Endocrine Disrupting Chemicals (EDCs), have raised the interest of the scientific community, because of possible adverse effects on the environment and the living organisms. Although several treatment technologies have been applied for their removal, operation and maintenance costs are prohibitive. Therefore, this study aims to study the treatment of EDCs with an alternative and environmentally friendly technology: constructed wetlands (CWs). For this purpose, 6 pilot-scale CW units of two types, horizontal subsurface flow (HSF) and vertical flow (VF), were used for the treatment of municipal wastewater originating from a university campus, targeting the removal of five EDCs: Bisphenol A (BPA), Nonylphenol (NP), Nonylphenol monoethoxylate (NP1EO), Nonylphenol diethoxylate (NP2EO) and Triclosan (TCS). Results showed that the median removal performance in HSF-R was 49.6%, 51.4% and 48.4%, in HSF-C was 50.0%, 99.0% and 66.0%, and in HSF-Z was 55.4%, 98.9% and 80.3% for BPA, NP1EO and NP2EO, respectively. NP was not removed but its concentration was increased by 48.0%, 43.7% and 51.9% in the HSF-R, HSF-C and HSF-Z, respectively. TCS was not detected in influent wastewater. In the VF-CWs, the median removal efficiencies were: 45.6%, −12.5%, 41.5% and 72.2% in VF-R, 60.0%, 96.2%, 99.0% and 99.8% in VF-C, and 59.0%, 95.6%, 98.7% and 99.8% in VF-Z for BPA, NP, NP1EO, NP2EO, respectively. The study indicates that the main removal pathways of the target EDCs is their biodegradation under aerobic or/and anaerobic conditions and adsorption onto the organic matter retained in the substrate.

Effect of plants and surface loading rate on the treatment efficiency of shallow subsurface constructed wetlands

The aim of this research was to study the influence of the presence of plants and of plant species on the treatment efficiency of shallow (0.3m effective depth) horizontal subsurface flow constructed wetlands (CWs) treating diluted municipal wastewater. The pilot plant was situated in A Coruña (Spain) and constituted of five CW units in parallel: CW1 (unplanted), CW2 (Juncus effusus) CW3 (Iris pseudacorus), CW4 (Typha latifolia L.) and CW5 (Phragmites australis). A long term study (from October 2009 to March 2012) was carried out with five monitoring campaigns during the two first years of operation at low surface loading rate (SLR, 2.5g BOD5/m2d on average) and two monitoring campaigns during the third year at design SLR (4.7g BOD5/m2d on average). At low SLR rate, significant differences between units were not found for TSS (89–93%), COD (83–88%) or BOD5 (90–95%) percentage removal which, in turn, appeared at design SLR, when BOD5 removal decreased to 78% (CW1), 69% (CW4), 87% (CW2), 86% (CW3) and 94% (CW5). Thus, the effect of plants on the removal efficiency of organic matter (COD, BOD5) appeared to be dependent on the loading rate. CW2 reached the highest nitrogen removal, followed by CW4, CW5 and CW3 at a similar level and, finally, by CW1. Results indicate that the additional nitrogen removal rate in planted units increased with plant biomass productivity which also determined evapotranspiration variability between units. Typha latifolia L. appeared to be the most sensitive species to adverse conditions.

Methane and carbon dioxide emissions from constructed wetlands receiving anaerobically pretreated sewage

The aim of this research was to determine methane and carbon dioxide emissions from a hybrid constructed wetland (CW) treating anaerobically pre-treated sewage. The CW was constituted of two horizontal flow (free water surface followed by a subsurface) units. A long-term study was carried out as both CW units were monitored for three campaigns in Period 1 (0.9–1.5years after start-up), and four campaigns in Period 2 (4.5–5.8years after start-up). The closed chamber method with collecting surfaces of 1810cm2 was used. For this system, variability due to position in the transverse section of CW, plant presence or absence and recommended sampling period was determined.Overall methane emissions ranged from 96 to 966mgCH4m−2 d−1, depending on several factors as the operation time, the season of the year and the position in the system. Methane emissions increased from 267±188mgCH4m−2d−1 during the second year of operation to 543±161mgCH4m−2d−1 in the sixth year of operation. Methane emissions were related to the age of the CW and the season of the year, being high in spring and becoming lower from spring to winter. Total CO2 emissions ranged mostly from 3500 to 5800mgCO2m−2d−1 during the sixth year of operation, while nitrous oxide emissions were below the detection limit of the method.

Effect of hydraulic retention time, temperature, and organic load on a horizontal subsurface flow constructed wetland treating cheese whey wastewater

AbstractBACKGROUNDOne of the main components of dairy wastewaters is cheese whey. Although different technologies have been used extensively in the past for cheese‐whey treatment, constructed wetlands (CWs) applications are limited. Furthermore, the effect of crucial operational parameters (e.g. temperature, pollutant loading rate) have not been thoroughly studied. Having this in mind, two horizontal subsurface flow pilot‐scale CW units (one planted and one unplanted) were used to treat secondary cheese whey, in order to examine the effect of different chemical oxygen demand (COD) influent concentrations (1200 to 7200 mg L−1), hydraulic residence times (8, 4, 2 and 1 day) and temperature (2.4 to 32.9 °C).RESULTSDuring a 2‐year operating period both pilot‐scale units successfully removed organic matter, with COD removal efficiencies recorded at 91% and 77.2% for the planted and the unplanted unit, respectively. Hydraulic residence time affected COD removal efficiency only when limited to 1 day. Temperature significantly affected COD removal only in the unplanted unit.CONCLUSIONSConstructed wetlands could successfully treat secondary cheese whey and provide COD effluent concentrations below EU legislation, when hydraulic residence time is above 2 days and COD influent concentration ranges from 1200 to 3500 mg L−1. © 2015 Society of Chemical Industry

First stage of the French vertical flow constructed wetland system: experiments with the reduction of surface area and number of units

Small vertical-flow constructed wetland units comprising the first stage of the French system were studied in Brazil for the treatment of raw sewage. Planted and unplanted units and different feeding strategies were tested. In the first phase, hourly batches of a daily flow of 13 m3 d−1 were applied over three alternating units, resulting in an average hydraulic loading rate (HLR) on the full system of 0.15 m3 m−2 d−1. A second phase, aimed at reducing land requirements, kept the same daily flow and batch frequency, but used two alternating units, resulting in a HLR on the full system of 0.22 m3 m−2 d−1. Removal efficiencies were very good when the system operated with three units, with mean values of 82% for biochemical oxygen demand (BOD), 81% for chemical oxygen demand (COD), 85% for total suspended solids (TSS) and 59% for NH4+-N. With two units, the equivalent values were 74% for BOD, 59% for COD, 67% for TSS and 51% for NH4+-N. There were significant differences in the median removal efficiencies of COD and TSS. No significant differences were found between planted and unplanted units for most constituents. In both phases, the overall good performance and the simplicity of the system make this treatment process a very attractive alternative for developing countries.

Evaluation of a hybrid constructed wetland system for treating urban stormwater runoff

This study developed hybrid constructed wetlands (CWs) for treatment of urban stormwater runoff pollutants. Hybrid CWs applied at narrow sections in urban areas are typically small and modular in type. Several treatment mechanisms were occurring in the hybrid system to treat high level of pollutant mass loading from urban stormwater runoff. A small scale hybrid CW comprised of a sedimentation tank, free water surface (FWS) CW, and horizontal sub-surface flow (HSSF) CW, was studied. A total of 10 test runs were simulated in the hybrid CW since July 2011–November 2012. Based on the results, almost 51–78% reduction in pollutants such as TSS, COD, TN, TP, and total heavy metals (Fe, Cu, and Zn) was achieved after passing the first and second units of the hybrid CW (i.e. sedimentation tank and FWS CW). Finally, additional 9–25% reduction of these pollutants was obtained as they went through the HSSF CW. Using normalized pollutant concentration with respect to the facility length, the appropriate size of hybrid CWs was determined to be at least 2 m. Comparing the removal efficiencies of the two types of hybrid CW system (i.e. reed and iris combination in Type A; and reed and cattail combination in Type B) similar results were obtained.

Pollutant Removal Efficiency of Vertical Sub-surface Upward Flow Constructed Wetlands for Highway Runoff Treatment

Four small-scale cylindrical, vertical upward flow constructed wetland units were installed and evaluated to determine the effectiveness of these units to treat highway runoff. The highway runoff was collected during various rainfall events in the year 2009 from Lukou Viaduct section of Nanjing airport express highway. The natural zeolite and gravel were used as filter substrates and all four units were planted with common reed (Phragmites spp.). These four units were subjected to similar hydraulic retention time (6 h HRT) with different hydraulic loads. Water samples were collected from the influent and effluent of vertical flow constructed wetlands, and were analyzed for determination of total suspended solids, COD, ammoniacal nitrogen, total nitrogen and total phosphorus. The results show that vertical flow constructed wetlands with zeolite–gravel substrate combination achieved the best performance between all systems with mean removal efficiency of 57 % TSS, 45 % COD and 78 % ammoniacal nitrogen. The average ammoniacal nitrogen decreased by approximately 65 % in all wetland units, suggesting that this design had the highest nitrification rate. The study also revealed that the use of substrate materials with specific characteristics, such as zeolite and gravel, can enhance the removal of nutrients. However, the overall performance of vertical upward flow constructed wetlands was not effective.

Highway runoff treatment by lab-scale horizontal sub-surface flow constructed wetlands

In this study, lab-scale horizontal sub-surface flow constructed wetlands were experimented to assess their removal efficiency of highway runoff pollutants under different hydraulic conditions. Constructed wetland units with cobble-stone and broken-stone material as filter media were planted with common reed (Phragmites spp.) plants. Water samples collected from inlets and outlets of the wetland units were analyzed to determine total suspended solids, COD, ammonia-nitrogen, total nitrogen and total phosphorus. The results show that removal efficiency was quite low with cobble-stone filter media, whereas constructed wetland units with broken-stone filter media led to higher removal efficiency for SS (73.54%), COD (55.48%), NH3-N (81.89%) and TP (57.08%), respectively, but had a TN removal of −29.29% (increase in effluent). Results indicate that overall broken-stone filter media demonstrated better performance than cobble-stone filter media because broken-stone has larger specific surface area.