**1. Introduction**

[62] Esteve-Zarzoso B, Belloch C, Uruburu F, Querol A. Identification of Yeasts by RFLP Analysis of the 5.8S rRNA Gene and the Two Ribosomal Internal Transcribed

[63] Granchi L, Bosco M, Vicenzini M. Rapid Detection and Quantification of Yeast Spe‐ cies During Spontaneous Wine Fermentation by PCR-RFLP Analysis of the rDNA

[64] Bray HG, Thrope WV. Methods of Biochemical Analysis. London: Interscience Pub‐

[65] Colarieti ML, Toscano G, Greco G. Toxicity Attenuation of Olive Mill Wastewater in

[66] Hamdi M, Kadir A, Garcia JL. The Use of *Aspergillus niger* for Bioconversion of Olive Mill Wastewaters. Applied Microbiology and Biotechnology 1991; 34 (6): 828–831. [67] Afify AS, Mahmoud MA, Emara HA, Abdelkreem KI. Phenolic Compounds and COD Removal from Olive Mill Wastewater by Chemical and Biological Procedures.

[68] Martin A, Borja R, Chica A. (1993). Kinetic Study of an Anaerobic Fluidized Bed Sys‐ tem Used for the Purification of Fermented Olive Mill Wastewater. Journal of Chemi‐

Spacers. International Journal of Systematic Bacteriology 1999; 49 (1): 329-337.

ITS Region. Journal of Applied Microbiology 1999; 87 (6): 949-956.

Soil Slurries. Environmental Chemistry Letters 2006; 4 (2): 115-118.

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lishers; 1954. p. 27-50.

66 Applied Bioremediation - Active and Passive Approaches

Constructed wetlands are promising engineering technique that reproduce the conditions of the natural wetlands [1]. They have high water treatment capacity because of the intensive "work" of the plants and the microorganisms. Depending on the conditions various types of plants are growing: common reed (*Phragmites australis*), rush (*Typha latifolia*), iris, etc. (Fig. 1). These plants are stable toward the climatic changes and the quality parameters of the medium in which they are growing. The metabolism of the microorganisms plays an important role in the pollutants removal from wastewaters. The main chemical and physical processes are sedimentation, sorption, chemical oxidation, photo degradation, evaporation [2] as well as biotic processes such as aerobic/anaerobic degradation, plants accumulation, phytodegradation, phytoevaporation. Many publica‐ tions demonstrate the removal of suspended solids, organic matter, nutrients and bacte‐ ria from wastewater in constructed wetlands. There are two types of constructed wetlands: *surface flow wetlands systems* and *subsurface flow wetland systems*. The latter are subsurface horizontal flow wetlands systems (Fig. 2) and subsurface vertical flow wetland systems (Fig. 3), [3-6]. They are characterized with the different extent of nutrients removal [7-10].

In the subsurface vertical-flow constructed wetlands (SSVFCW) the wastewater enters through the surface and flows in vertical direction slowly through the supporting material and the plant roots until reaching the bottom outlet zone. These systems are built with porous materials such as sand and gravel, that restrict the clogging. The package clogging was observed at high organic load of the system [11]. The recirculation of the wastewater is helpful to overcome this limitation.

© 2013 Lavrova and Koumanova; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Figure 3.** Subsurface vertical-flow wetlands system

+

COD – 49 % and 40 %, NH4

phosphorus (TP) – 63 % and 9 %, PO4

Scholz and Hu [12] investigated various filter materials and macrophytes for the removal of lead and copper from wastewaters. They demonstrated the possibility to replace the expensive activated carbon and charcoal with the cheaper sand and gravel. Korkusuz [13] reports for the treatment of domestic wastewater in subsurface flow wetland with wasted granular slag and gravel. He obtained for both materials the removal of suspended solids (SS) 64 % and 62 %,

3--P – 60 % and 4 %. SSVFCW are used for treatment of industrial wastewaters from different sources: dyecontaining waters [14,15], pharmaceutically polluted waters [16], wastewaters from food industry [17], olive mill wastewaters [18], liquid waste activated sludge from a soft drink factory [19]. Gross et al. [20] reports for a novel method of recycling greywater for irrigation. The all SS and BOD were removed and about 80 % of COD after 8 h. A recirculating vertical

A combined subsurface vertical and horizontal flow constructed wetland system was designed for rular domestic wastewater treatment [22]. Several water quality parameters pH, BOD, COD, TSS, TKN, TP and faecal bacteria's number in both raw and treated wastewaters were monitored during a macrophytes life cycle. Seven mesocosm-scale constructed wetlands of different configurations were operated out-doors for 39 months to assess their ability to remove

flow constructed wetland was used also for treatment of domestic waters [21].


Nutrients and Organic Matter Removal in a Vertical-Flow Constructed Wetland

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**Figure 1.** Different types of plants growing in the wetland systems

**Figure 2.** Subsurface horizontal-flow wetlands system

**Figure 3.** Subsurface vertical-flow wetlands system

**Figure 1.** Different types of plants growing in the wetland systems

68 Applied Bioremediation - Active and Passive Approaches

**Figure 2.** Subsurface horizontal-flow wetlands system

Scholz and Hu [12] investigated various filter materials and macrophytes for the removal of lead and copper from wastewaters. They demonstrated the possibility to replace the expensive activated carbon and charcoal with the cheaper sand and gravel. Korkusuz [13] reports for the treatment of domestic wastewater in subsurface flow wetland with wasted granular slag and gravel. He obtained for both materials the removal of suspended solids (SS) 64 % and 62 %, COD – 49 % and 40 %, NH4 + -N – 88% and 58 %, total nitrogen (TN) – 41 % and 44 %, total phosphorus (TP) – 63 % and 9 %, PO4 3--P – 60 % and 4 %.

SSVFCW are used for treatment of industrial wastewaters from different sources: dyecontaining waters [14,15], pharmaceutically polluted waters [16], wastewaters from food industry [17], olive mill wastewaters [18], liquid waste activated sludge from a soft drink factory [19]. Gross et al. [20] reports for a novel method of recycling greywater for irrigation. The all SS and BOD were removed and about 80 % of COD after 8 h. A recirculating vertical flow constructed wetland was used also for treatment of domestic waters [21].

A combined subsurface vertical and horizontal flow constructed wetland system was designed for rular domestic wastewater treatment [22]. Several water quality parameters pH, BOD, COD, TSS, TKN, TP and faecal bacteria's number in both raw and treated wastewaters were monitored during a macrophytes life cycle. Seven mesocosm-scale constructed wetlands of different configurations were operated out-doors for 39 months to assess their ability to remove organic matter and nutrients from urban wastewaters [23]. F. Ye and Y. Li [24] have shown that nitrification/denitrification is the main mechanism for nitrogen removal from domestic wastewater in a novel constructed wetland configuration with three stages towery hybrid CW. Increased dissolved oxygen (DO) by passive aeration enhanced nitrification rates and addi‐ tional organic matter supplied - for denitrification. In an installation, consisted of two settling tanks in series, a VFCW and a zeolite tank, Gicas and Tsihrintzis have studied household wastewater treatment [25]. The zeolite was found to offer additional removal of nitrogen, total phosphorus and organic matter. Significant reduction of total coliform and faecal coliform was achieved in a pilot scale VFCW in North Cairo planted with three kinds of plants [26]. The use of VFCW as a post treatment step will make possible the usage of the treated water for irrigation. The treatment effect of two pilot-scale VFCWs (one planted with *Tipha latifolia* and the second – with *Phragmites australis*) on municipal wastewaters and their suitability for irrigation reuse were studied in a 2-year experiment [27]. Zurita et al. [28] suggested that it is possible to produce commertial flowers in CW.

tages were over 99 %, 72 % and 97 %, respectively. The removal of *Escherichia coli* was 99,9 %.

Many investigations have been done of the influence of the operational parameters on the treatment efficiency of the constructed wetlands. Giraldi and Iannelli [42] used a capacitance probe to measure water content in a vertical flow CW pilot plant. They compared field measurements with data recorded in a laboratory apparatus. The effect of various design parameters has been studied by Stefanakis and Tsihrintzis [43]. Various porous media materials (carbonate material, material from river bed, zeolite and bauxite), two vegetation types (common reeds and cattails) and three total thicknesses of the porous media were used in 10 wetlands. Organic matter removal was good in all units, since it reached on the average 71,1 % and 66,9 % for BOD and COD, respectively. Nitrogen removal was 47,1 % for TKN and

domestic wastewater [44]. The main oxygen source was the atmospheric reoxygenation and approximately 50 % of it was supplied to 0-10 cm below the water distribution system. Over 99,8 % of the oxygen consumed was used for organic degradation and nitrification. The performance response of planted and unplanted wetlands to simulated wastewater with different ratios of carbon to nitrogen (2,5:1, 5:1 and 10:1) was studied during a 9-month period in greenhouse conditions by Zhao et al. [45]. At C/N ratio 5:1 was achieved a relatively high biological nitrogen removal efficiency and a low level of greenhouse gases flux [46]. Prochaska et al. studied the influence of the season, substrate, hydraulic load and frequency of application of simulated urban sewage on the performance of pilot-scale VFCW [47]. The ANOVA statistical model was applied to analyse the relationships between the main operational factors


tested with rhodamine WT and numerical modeling was used as written in [48]. The capacity of an on-site recirculating VFCW to withstand disturbances and highly variable influent quality was studied [49]. It was found that the general recovery is reached within 24 h. Lihua Cui et al. treated domestic wastewater using three different slags, hydraulic loading rates, operational periods with and without plants for the removal of nitrogen and phosphorus [50]. Hybrid systems were compared at different C/N ratios by Zhao et al. [51]. S. Prost-Boucle and P. Molle established the dependence of nitrification on the recirculation rate and seasons (temperature effect) [52]. Effect of loading, resting period, temperature, porous media, vegetation and aeration were studied by Stefanakis and Tsihrintzis [53]. In a review Saeed and Sun [54] discussed the dependence of nitrogen and organics removal on the environmental

The role of the plants was studied toward the removal of nitrogen and phosphorus [55,56]. Iamchaturapatr et al. studied nutrient removal by 21 plants (18 emergent and 3floating plants)

Bacterial carbon utilization in VFCW was studied by Tietz et al.[58]. A simple mass-balance approach was applied to explain the bacterially catalysed organic matter degradation. In another paper Tietz et al. [59] made a quantitative description of the microbial biocoenosis in subsurface VFCW fed with municipal wastewater. The microbial biomass was measured at


Nutrients and Organic Matter Removal in a Vertical-Flow Constructed Wetland

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71

3--P. The hydrodynamics of VFCW was

Nitrogen and phosphorus removal was studied also in [38-41].

42,2 % for NH4

+

and the effluent COD, NO2


parameters, operating conditions and supporting media.

by area-based calculation and biomass-based calculations [57].

High rate nitrogen removal in a two-stage SSVFCW has been studied by Langergraben et al. [29]. The first stage used sand with a grain size of 2-3.2 mm and the second stage – 0.06-4 mm. Better effluent quality as compared with to conventional single-stage VFCW was obtained. The Austrian effluent standards for organic matter and ammonium nitrogen were met and the average nitrogen removal efficiency was 53 % without recirculation. A three-stage experi‐ mental CW system consisting of a vertical flow-gravel filtration bed without plants, a hori‐ zontal subsurface flow bed planted with *Iris australis* and a vertical subsurface flow bed planted with *Phragmites australis* in series were fed with primary treated domestic water [30]. The beds with plants produced effluents of better quality than that without plants. It was observed that the average removal efficiencies increased with the decrease of hydraulic loading rate. Panuvatvanich et al. studied the nitrification and denitrification potential of sand layer and the effect of percolate impounding regime on nitrogen transformation in four laboratory-scale units of vertical-flow CW fed once a week with faecal sludge [31]. Biabowiec et al. investigated the effects of reed and willow on bioremediation of landfill leachate in comparison with an unplanted control by measuring redox potential levels in the rhizosphere of microcosm systems in a greenhouse [32]. Molle et al. discussed the nitrogen removal in terms of the efficiency of the stages in a hybrid constructed wetlands plant designed for 100 person equivalent [33]. The first stage was composed of vertical filters, followed by a second stage of horizontal filters. Ouyang et al. [34] developed a model using the STELLA software for estimating nitrogen dynamics in a vertical-flow constructed wetland. It was established 18 % of TN lost due to denitrification, 6 % of TN was taken up by roots of a single plant and the rest of 22 % TN from the wastewater was removed from other mechanisms, such as volatilization, adsorption and deposition. Anaerobically pretreated domestic wastewater was treated in a hybrid CW with recirculation (first in horizontal-flow CW and then in vertical-flow CW). 98% total Kjeldahl nitrogen and 79 % total nitrogen removal was obtained [35]. Li-Hua Cui et al. demonstrated the role of *Cyperus alternifolius*for the removal of total nitrogen in a VFCW [36]. Saeed and Sun [37] conducted comparative experiments in a lab-scale hybrid system with gravel, wood mulch and zeolite as medium. Average NH4 + -N, TN and BOD removal percen‐ tages were over 99 %, 72 % and 97 %, respectively. The removal of *Escherichia coli* was 99,9 %. Nitrogen and phosphorus removal was studied also in [38-41].

organic matter and nutrients from urban wastewaters [23]. F. Ye and Y. Li [24] have shown that nitrification/denitrification is the main mechanism for nitrogen removal from domestic wastewater in a novel constructed wetland configuration with three stages towery hybrid CW. Increased dissolved oxygen (DO) by passive aeration enhanced nitrification rates and addi‐ tional organic matter supplied - for denitrification. In an installation, consisted of two settling tanks in series, a VFCW and a zeolite tank, Gicas and Tsihrintzis have studied household wastewater treatment [25]. The zeolite was found to offer additional removal of nitrogen, total phosphorus and organic matter. Significant reduction of total coliform and faecal coliform was achieved in a pilot scale VFCW in North Cairo planted with three kinds of plants [26]. The use of VFCW as a post treatment step will make possible the usage of the treated water for irrigation. The treatment effect of two pilot-scale VFCWs (one planted with *Tipha latifolia* and the second – with *Phragmites australis*) on municipal wastewaters and their suitability for irrigation reuse were studied in a 2-year experiment [27]. Zurita et al. [28] suggested that it is

High rate nitrogen removal in a two-stage SSVFCW has been studied by Langergraben et al. [29]. The first stage used sand with a grain size of 2-3.2 mm and the second stage – 0.06-4 mm. Better effluent quality as compared with to conventional single-stage VFCW was obtained. The Austrian effluent standards for organic matter and ammonium nitrogen were met and the average nitrogen removal efficiency was 53 % without recirculation. A three-stage experi‐ mental CW system consisting of a vertical flow-gravel filtration bed without plants, a hori‐ zontal subsurface flow bed planted with *Iris australis* and a vertical subsurface flow bed planted with *Phragmites australis* in series were fed with primary treated domestic water [30]. The beds with plants produced effluents of better quality than that without plants. It was observed that the average removal efficiencies increased with the decrease of hydraulic loading rate. Panuvatvanich et al. studied the nitrification and denitrification potential of sand layer and the effect of percolate impounding regime on nitrogen transformation in four laboratory-scale units of vertical-flow CW fed once a week with faecal sludge [31]. Biabowiec et al. investigated the effects of reed and willow on bioremediation of landfill leachate in comparison with an unplanted control by measuring redox potential levels in the rhizosphere of microcosm systems in a greenhouse [32]. Molle et al. discussed the nitrogen removal in terms of the efficiency of the stages in a hybrid constructed wetlands plant designed for 100 person equivalent [33]. The first stage was composed of vertical filters, followed by a second stage of horizontal filters. Ouyang et al. [34] developed a model using the STELLA software for estimating nitrogen dynamics in a vertical-flow constructed wetland. It was established 18 % of TN lost due to denitrification, 6 % of TN was taken up by roots of a single plant and the rest of 22 % TN from the wastewater was removed from other mechanisms, such as volatilization, adsorption and deposition. Anaerobically pretreated domestic wastewater was treated in a hybrid CW with recirculation (first in horizontal-flow CW and then in vertical-flow CW). 98% total Kjeldahl nitrogen and 79 % total nitrogen removal was obtained [35]. Li-Hua Cui et al. demonstrated the role of *Cyperus alternifolius*for the removal of total nitrogen in a VFCW [36]. Saeed and Sun [37] conducted comparative experiments in a lab-scale hybrid system with

+


possible to produce commertial flowers in CW.

70 Applied Bioremediation - Active and Passive Approaches

gravel, wood mulch and zeolite as medium. Average NH4

Many investigations have been done of the influence of the operational parameters on the treatment efficiency of the constructed wetlands. Giraldi and Iannelli [42] used a capacitance probe to measure water content in a vertical flow CW pilot plant. They compared field measurements with data recorded in a laboratory apparatus. The effect of various design parameters has been studied by Stefanakis and Tsihrintzis [43]. Various porous media materials (carbonate material, material from river bed, zeolite and bauxite), two vegetation types (common reeds and cattails) and three total thicknesses of the porous media were used in 10 wetlands. Organic matter removal was good in all units, since it reached on the average 71,1 % and 66,9 % for BOD and COD, respectively. Nitrogen removal was 47,1 % for TKN and 42,2 % for NH4 + -N. J.Ye et al. studied the vertical oxygen distribution in a VFCW treating domestic wastewater [44]. The main oxygen source was the atmospheric reoxygenation and approximately 50 % of it was supplied to 0-10 cm below the water distribution system. Over 99,8 % of the oxygen consumed was used for organic degradation and nitrification. The performance response of planted and unplanted wetlands to simulated wastewater with different ratios of carbon to nitrogen (2,5:1, 5:1 and 10:1) was studied during a 9-month period in greenhouse conditions by Zhao et al. [45]. At C/N ratio 5:1 was achieved a relatively high biological nitrogen removal efficiency and a low level of greenhouse gases flux [46]. Prochaska et al. studied the influence of the season, substrate, hydraulic load and frequency of application of simulated urban sewage on the performance of pilot-scale VFCW [47]. The ANOVA statistical model was applied to analyse the relationships between the main operational factors and the effluent COD, NO2 - -N, NO3 - -N, TN and PO4 3--P. The hydrodynamics of VFCW was tested with rhodamine WT and numerical modeling was used as written in [48]. The capacity of an on-site recirculating VFCW to withstand disturbances and highly variable influent quality was studied [49]. It was found that the general recovery is reached within 24 h. Lihua Cui et al. treated domestic wastewater using three different slags, hydraulic loading rates, operational periods with and without plants for the removal of nitrogen and phosphorus [50]. Hybrid systems were compared at different C/N ratios by Zhao et al. [51]. S. Prost-Boucle and P. Molle established the dependence of nitrification on the recirculation rate and seasons (temperature effect) [52]. Effect of loading, resting period, temperature, porous media, vegetation and aeration were studied by Stefanakis and Tsihrintzis [53]. In a review Saeed and Sun [54] discussed the dependence of nitrogen and organics removal on the environmental parameters, operating conditions and supporting media.

The role of the plants was studied toward the removal of nitrogen and phosphorus [55,56]. Iamchaturapatr et al. studied nutrient removal by 21 plants (18 emergent and 3floating plants) by area-based calculation and biomass-based calculations [57].

Bacterial carbon utilization in VFCW was studied by Tietz et al.[58]. A simple mass-balance approach was applied to explain the bacterially catalysed organic matter degradation. In another paper Tietz et al. [59] made a quantitative description of the microbial biocoenosis in subsurface VFCW fed with municipal wastewater. The microbial biomass was measured at different depths of planted and unplanted systems. Sleytr et al. demonstrated the influence of the plants on the rhizosphere community [60].

**3. Material and methods**

**Table 1.** Characteristics of the influent wastewater


started again and the water began to flow again through the SSVFW.

+

NO3 -

Nitrogen (NH4

Pig slurry was taken from a farm located in south-western part of Bulgaria and the landfill leachate was taken from a landfill situated in the north-western region in Bulgaria. After collection, the wastewater was allowed to settle overnight. After that the supernatant was

**Parameter Influent**

**Pig slurry Landfill leachate**

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73

treated. Table 1 summarizes the main characteristics of the influent wastewaters.

COD, *mg L-1* 1535 ± 502 2940 ± 140 BOD, *mg L-1* 612 ± 419 230.5 ± 26.5 NH4 +-N, *mg L-1* 322 ± 87 206.7 ± 8.3

 -N, *mg L-1* 0 1.5 ± 0.4 pH 7.2 ± 1.1 7.9 ± 0.4

The water samples were taken every day. The water samples have been examined for pH, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Ammonium-

**• Lab-scale subsurface vertical-flow wetland planted with** *Phragmites australis* **(SSVFW)**

The laboratory system consisted of sedimentation tank, subsurface vertical-flow wetland, peristaltic pump and storage tank of the treated water (Fig. 4). The SSVFW was made of Plexiglas with dimensions of 123 mm in diameter and 900 mm in height. The reactor was filled with 35 ÷ 55 mm round gravel with 300 mm height as bottom layer and top layer of 5 ÷ 25 mm gravel with a height of 500 mm. Young *Phragmites australis*, obtained from comparatively clean area, was planted in the top layer of the SSVFW. After collection, the wastewater was allowed to settle overnight, the supernatant was diluted with tap water and then was treated. This was done to avoid possible damage of the plant because of the significant contamination of the raw pig slurry and landfill leachate. For increasing the purification capacity effluent recirculation was used [77-82]. The SSVFW was operated continuously in recirculation regime. The recirculation was employed at ratio of 1:1, giving SSVFW 1 h of wastewater-bed matrix contact and 1 h of effluent recirculation. The flow rate of the system was 80 ml min-1 [80-82] and the hydraulic retention time was 0.9 h. After filling the reactor with wastewater, the laboratory peristaltic pump was turned on and the water started to flow through the system for a period of one hour. After that, controlled by programmed electronic timer, connected with peristaltic pump, the water stopped moving and remained calm in the SSVFW for one hour. After one hour the peristaltic pump



Nutrients and Organic Matter Removal in a Vertical-Flow Constructed Wetland

Based on Life Cycle Assessment (LCA) Fuchs et al. suggested that constructed wetlands have less environmental impact in terms of resource consumption and greenhouse gas emissions [61].

Different filter materials for phosphorus removal from wastewater in treatment wetlands have been studied [62, 63]. The potential of fragmented Moleanos limestone [64], wollastonite [65], crushed brick and palygorskite [66], a mixture of river sand and dolomite (10:1 w/w), [67] was investigated.

The landfill leachate is characterized with high nitrogeneous pollutants content. Investigations have been done on its purification in constructed wetlands. Four vertical-flow wetlands under predominately aerobic conditions were used for a mass-balance study in the transformation of nitrogeneous pollutants [68]. Landfill leachate was treated in a pilot-scale sub-surface CW planted with *Cyperus haspan* and three weeks retention time. Samples were tested for 13 parameters (pH, turbidity, color, TSS, COD, BOD5, NH4 + -N, TP, TN, Fe, Mg, Mn, Zn) and a high removal efficiency was obtained [69]. Justin et al. present a combination of landfill leachate pre-treatment in CW and subsequent reuse for the irrigation of grass and willows [70]. Six interconnected beds with horizontal and vertical subsurface water flow and planted with *Phragmites australis* were used. According to Bulk [71] CWs as a tertiary system or as an independent system could be a low-cost alternative for the treatment of leachate from old landfill sites. Leachate from a closed landfill was treated in an integral system consisted of extraction, aeration, settling, intermittent vertical sand filtration, a surface flow wetland with recycle and discharged in a river [72]. Experiments were conducted to treat a sanitary landfill leachate with high nitrogen and bacterial contents [73]. Mass balance analysis, based on total nitrogen contents of the plant biomass and dissolved oxygen and oxidation reduction potential values, suggested that 88 % of the input total nitrogen were uptaken by the plant biomass. Lavrova and Koumanova studied the influence of recirculation in a lab-scale VFCW on the treatment efficiency of landfill leachate [74]. Comparison of horizontal and vertical CW systems for landfill leachate treatment with two types of material (gravel and zeolite) and planted with *Typha latifolia* was made by Yalcuk and Ugurlu [75]. Better NH4 + -N removal performance was observed in the VF system with zeolite. Horizontal flow system was more effective in COD removal.

#### **2. Aim**

The aim of this study is to investigate treatment efficiency of the raw pig slurry and the landfill leachate in a lab-scale subsurface vertical-flow wetland (SSVFW) planted with *Phragmites australis*, in the lab-scale aerobic activated sludge bioreactor (ASR) and in an hybrid installation where the first stage includes an aerobic activated sludge bioreactor and the second stage – a subsurface vertical-flow wetland (ASR-SSVFW).
