**3. Material and methods**

different depths of planted and unplanted systems. Sleytr et al. demonstrated the influence of

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

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

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

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

performance was observed in the VF system with zeolite. Horizontal flow system was more

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

+


+


the plants on the rhizosphere community [60].

72 Applied Bioremediation - Active and Passive Approaches

parameters (pH, turbidity, color, TSS, COD, BOD5, NH4

emissions [61].

investigated.

effective in COD removal.

subsurface vertical-flow wetland (ASR-SSVFW).

**2. Aim**

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


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

The water samples were taken every day. The water samples have been examined for pH, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Ammonium-Nitrogen (NH4 + - N) and Nitrate-Nitrogen (NO3 - - N) by standard methods [76].

#### **• 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 started again and the water began to flow again through the SSVFW.

**Figure 4.** Flow diagram of the SSVFW

#### **• Lab-scale aerobic activated sludge reactor (ASR)**

ASR of 195 mm in diameter and 650 mm in height was used. The aeration system consisted of three diffusers, situated at the bottom of the bioreactor. The activated sludge (AS) was taken from a municipal wastewater treatment plant. After preliminary sedimentation in primary sedimentation tank the wastewater entered the ASR, where it was mixed with activated sludge in volume ratio 1:1. After reaching of the standard measurements of the controlled physico‐ chemical characteristics, wastewater flow into secondary sedimentation tank for clarifying, which leading to removal of the suspended activated sludge (Fig. 5).

#### **• hybrid installation consisted of an aerobic activated sludge reactor (ASR) and a subsur‐ face vertical-flow wetland (ASR / SSVFW)**

**Figure 6.** Flow diagramme of the hybrid installation ASR-SSVFW

Fig. 7 to Fig. 10 illustrate the comparison of the water characteristics during the experiments.


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

http://dx.doi.org/10.5772/56245

75

/ BOD0 and NH4

+ -Nt / NH4 + -N0).

/ COD0, BODt

**4. Case study 1: Pig slurry treatment**

+

certain moment and its initial concentration (CODt

COD, BOD and NH4

**Figure 5.** Flow diagram of the ASR

After preliminary sedimentation in primary sedimentation tank the wastewater entered the ASR, where it was mixed with activated sludge in volume ratio 1:1. For several days the water is treated in the ASR to achieve a double reduce of pollutants concentration in terms of COD and [NH4 + - N]. After reaching the necessary concentration, the suspension passed through the secondary sedimentation tank for clarification and then entered the SSVFW for polishing (Fig. 6). 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 recircula‐ tion. The flow rate of the system was 80 ml min-1 and the hydraulic retention time was 0.9 h.

**Figure 5.** Flow diagram of the ASR

**Figure 4.** Flow diagram of the SSVFW

74 Applied Bioremediation - Active and Passive Approaches

**• Lab-scale aerobic activated sludge reactor (ASR)**

**face vertical-flow wetland (ASR / SSVFW)**

which leading to removal of the suspended activated sludge (Fig. 5).

ASR of 195 mm in diameter and 650 mm in height was used. The aeration system consisted of three diffusers, situated at the bottom of the bioreactor. The activated sludge (AS) was taken from a municipal wastewater treatment plant. After preliminary sedimentation in primary sedimentation tank the wastewater entered the ASR, where it was mixed with activated sludge in volume ratio 1:1. After reaching of the standard measurements of the controlled physico‐ chemical characteristics, wastewater flow into secondary sedimentation tank for clarifying,

**• hybrid installation consisted of an aerobic activated sludge reactor (ASR) and a subsur‐**

After preliminary sedimentation in primary sedimentation tank the wastewater entered the ASR, where it was mixed with activated sludge in volume ratio 1:1. For several days the water is treated in the ASR to achieve a double reduce of pollutants concentration in terms of COD and [NH4

N]. After reaching the necessary concentration, the suspension passed through the secondary sedimentation tank for clarification and then entered the SSVFW for polishing (Fig. 6). 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 recircula‐ tion. The flow rate of the system was 80 ml min-1 and the hydraulic retention time was 0.9 h.

+ -

**Figure 6.** Flow diagramme of the hybrid installation ASR-SSVFW
