Efficacy of Typha angustifolia based vertical flow constructed … · Efficacy of Typha angustifolia based vertical flow constructed wetland system in pollutant reduction of domestic

INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 3, No 5, 2013

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4402

Received on March 2013 Published on April 2013 1497

Efficacy of Typha angustifolia based vertical flow constructed wetland

system in pollutant reduction of domestic wastewater Arivoli A1, Mohanraj R2

1- Research Scholar, Department of Environmental Management, Bharathidasan

University, Tiruchirappalli, Tamilnadu, India-24

2- Assistant Professor, Department of Environmental Management, Bharathidasan

University, Tamilnadu, India -24

[email protected]

doi:10.6088/ijes.2013030500020

ABSTRACT

Constructed wetland containing tolerant aquatic macrophytes have been found to remove

contaminants from domestic wastewater more efficiently. In this study, Vertical Flow

Constructed wetland was applied and examined for the removal efficiency of organic and

inorganic pollutants from domestic wastewater by using gravel and sand as substrates planted

with Typha augustifolia (Cattail) and other without plantation which serves as a control. To

evaluate the performance, three different operating Hydraulic Retention Time (HRT) 12, 24

and 36 hours were maintained. Influent and effluent samples were collected, analysed for

their removal performance. The treatment efficiency was found to be maximum in cattail

planted VFCW with 36 hours HRT followed by 24 and 12 hours. The removal efficiency at

36 hours HRT were found to be 84.66% for TDS, 92.90% for Turbidity, 80.53% for COD,

75.49% for BOD5, 83.51% for PO4, 88.48 % for NO3. The removal efficiency of unplanted

VFCWs were 64.76% for Turbidity,67.26% for TDS, 64.70 % for COD, 56.45 % for BOD5

64.45% for PO4, and 61.80 % for NO3. When compared the removal efficiency of planted

with unplanted constructed wetland, planted VFCWs shows a maximum removal the results

showed that the removal efficiencies of the organics TDS, COD, BOD5, Phosphate and

Nitrate were improved significantly with the extension of HRT.

Keywords: Typha augustifolia, constructed wetland system, domestic wastewater,

Hydrualics Retention Time, vertical flow constructed wetlands.

1. Introduction

Treatment of domestic wastewater in rural and urban India is mostly carried out by activated

sludge or by bacterial process. Constructed Wetlands (CWs) can be used as an alternative

technology for the treatment of wastewater. In most part of the world especially in

industrialized countries, it has been successfully applied for treatment of domestic sewage

(Kivaisi, 2001, Brix et al., 2011: El Hamouri et al., 2007: Konnerup et al., 2009: and Trang et

al., 2010). Constructed wetlands (CWs) are vigorous biological systems that can be applied

for the treatment of several types of polluted water (Brix, 1994: Vymazal et al., 2006). A

good designed constructed wetland should able to maintain the Hydrualic Retention Time and

Loading Rates (Kadlec and Knight, 1996).

CWs are considered the most promising technology to wastewater due to low cost simple

operation and maintenance, and favourable appearance (Shutes, 2001). CWs for wastewater

treatment may be classified according to the life form of the dominating macrophyte, into

Efficacy of Typha angustifolia based vertical flow constructed wetland system in pollutant reduction of

domestic wastewater

Arivoli. A, Mohanraj. R International Journal of Environmental Sciences Volume 3 No.5, 2013

1498

systems with free-floating, floating leaved, rooted emergent and submerged macrophytes

(Brix, and Schierup, 1989). Further division could be made according to the wetland

hydrology (free water surface and subsurface systems) and subsurface flow CWs could be

classified according to the flow direction (horizontal and vertical) (Vymazal, and Kröpfelová.

2008). The most common systems are designed with horizontal sub-surface flow (HF CWs)

but vertical flow (VF CWs) systems are getting more popular at present (Brix, 1994:

Vymazal et al., 1998: Vymazal, 2001a).

VFCW have been used successfully in domestic wastewater over the last five year

(Prochaska et al., 2007), due to the treatment performance to obtained 90% of COD and

nitrogen removal, low operation cost (Brix and Arias, 2005: Tsihrintzis et al., 2007) higher

oxygen transfer capacity, high hydraulic loading rate, good removal nutrients and their small

size( Cooper et al., 1999: Brix and Arias, 2005a: Prochaska et al., 2007: Langergraber

et al., 2009).

In CWs pollutants are reduced from wastewater by physicochemical and biological process.

The pollutant is the wastewater could be removed in VFCW by precipitation as insoluble

salts, plant uptake and microbical metabolism (Lesage et al., 2007).

The wetland plants growing in CWs possess several functions in relation to the water

treatment (Brix, 1997). The most common aquatic plants used in subsurface flow wetland are

bulrush (Scirpus sp.), Cattail (Typha sp.), Reeds (Phragmites sp.), Cattail (Typha angustifolia

L.) is also widely used which is known to be highly tolerant to various types of wastewater

(Koottatep et al., 2001a: Koottatep et al., 2005b). In the present study Typha augustifolia was

employed which is a local aquatic plant. Normally, local aquatic plant is chosen due to its

natural adaptation with the local climate and availability as well as to mitigate the

unnecessary introduction of foreign or new species to the local environment (Calheiros et al.,

2008), it is normally used as a emergent plant because it forms extensive monoculture very

rapidly through vegetative reproduction and maintain its dominance with formation of dense

rhizome mats and litter which can used as a better to remove in wastewater treatment

(Motivans and Apfelbaum, 1987: Calheiros et al., 2008). The main objective of this study

was to assess the ability of vertical flow constructed wetland system. The objectives of the

present study were to assess the ability of vertical flow constructed wetland systems to treat

organic and nutrients present in wastewater, to evaluate the performance of system planted

with and without Typha augustifolia.

2. Materials and methods

Two VFCW were constructed, one was planted with Typha augustifolia and another without

planted which served as a control. Their dimensions were 29 cm diameter, 40 cm height and

total volume ranged in 25 liters (Two beds were maintained, 15 cm with gravel and sand) as

shown in Figure 1. Raw domestic wastewater was collected from the Post Graduate Hostel

of Bharathidasan University, allowed for gravity settlement for 6 hours in a sedimentation

tank and clear supernatant wastewater of 20 liters from the sedimentation tank was sieved

and transferred to the constructed wetland. The wastewater was treated at different

hydraulic retention time of 12, 24 and 36 hours. The experiment was performed from

August 2008 to January 2009. The water samples were collected in a sterile 500 ml plastic

bottle and stored at 4º C and physico-chemical parameters like pH, Electrical Conductivity

(E.C), Turbidity, Total Dissolved Solids, (TDS), Chemical Oxygen Demand (COD),

Biological Oxygen Demand (BOD5), Phosphate (PO4) and Nitrate (NO3) were analyzed as

described by APHA (1998).


domestic wastewater


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Treatment efficiency was calculated and expressed in percent removal (R) R = (Ce /Ci) × 100,

were Ci and Ce were the influent and effluent concentrations in mg/ L, respectively for each

parameter. Mean effluent values for every batch sampling over each month were used to

calculate removal rates for each parameter. To test the level of significance between the HRT

and the removal percentage statistical test like One Way ANOVA (Tukey method) was

performed at a significant level of P< 0.05.

3. Results and discussion

The characteristics of raw domestic wastewater from the post graduate hostel in

Bharathidasan University and pretreated water (6 hr settled effluent before applied in the

VFCW) are presented in table 1.

The pH of domestic wastewater and influent samples were 8.25 and 7.86 respectively and

the alkaline nature shall be due to washing, bathing etc. The effluent from the planted

VFCW had a mean pH of 7.70, 7.65, 7.57 and unplanted bed had a mean pH of 7.80, 7.74

and 7.70 during different retention time of 12, 24 and 36 hours respectively. The observed

pH reduction is due to CO2 production from decomposing plant litter and other wastewater

components trapped in their root mat (Chalee, 1985: Verhoeven, 1986) and nitrification of

ammonia (Bitton, 1994: IWA, 2000).

The Electrical Conductivity (E.C.) of domestic wastewater and influent samples were

observed to be 1.99 and 1.77 dS/m. The effluent from the planted VFCW had as mean E.C.

of 0.89, 0.80, 0.75 and unplanted bed had a mean E.C. of 1.32, 1.06 and 0.96 dS/m. during

different retention time 12, 24 and 36 hours respectively. Electrical Conductivity were

reduced due to evapotranspiration and/ or movement of substrate by plant roots accumulated

for this effect (Hench et al., 2003). The decrease in conductivity despite significant water

losses is explained by uptake of micro and macro elements and ions by plants and bacteria,

and their removal through adsorption to plant roots, litter and settleable suspended particles

(Bitton, 1994: IWA, 2000: DeBusk and DeBusk, 2001).

The turbidity of domestic wastewater and influent samples were observed to be 22.08 and

18.16 NTU. The effluent from the planted VFCW had a mean Turbidity of 2.54, 1.72, 1.26

NTU and unplanted bed had a mean Turbidity of 6.52, 5.96 and 5.56 NTU during different

retention time 12, 24 and 36 hours respectively. Efficiency of constructed wetland in the

removal of turbidity may depend on the sand granules, soil particle sizes and depth of the

bed (Prasad et al., 2006). VFCW system acted as a mechanical and biological filter and

removed suspended particles from the water and thus decreased turbidity as (Matagi et al.,

1998).

The Total Dissolved Solids (TDS) of domestic wastewater and influent samples were

observed to be 591 and 477.48 mg/l. The effluent from the planted VFCW had a mean TDS

of 104.04, 85.46, 73.26 mg/l and unplanted bed had a mean TDS of 147.4, 126.5 and

115.1.4 mg/l during different retention time 12, 24 and 36 hours respectively. The TDS

reduced due to the processes of sedimentation, filtration bacterial decomposition and

adsorption (Stowell et al, 1981).

The Chemical Oxygen Demand (COD) of domestic wastewater and influent samples were

observed to be 412.32 and 374.34 mg/l. The effluent from the planted VFCW had as mean

COD of 85.64, 73.90, 63.84 mg/l and unplanted bed had a mean COD of 126.4, 117.78 and

111.70 mg/l during different retention time 12, 24 and 36 hours respectively. This data


domestic wastewater


1500

agrees with the finding of Mashaurai et al., (2000) who found that longer retention time

would reduce COD. The removal of COD is attributed to microbial degradation of substrate

to the plants roots (Greenway and Woolley, 1999: Vymazal, 2002: Steer et al, 2003).

The Biological Oxygen Demand (BOD5) of domestic wastewater and influent samples

were observed to be 157.20 and 128.44 mg/l. The effluent from the planted VFCW had a

mean BOD5 of 38.86, 33.74, 30.74 mg/l and unplanted bed had a mean BOD5 of 66.08,

61.20 and 55.94 mg/l during different retention time 12, 24 and 36 hours respectively.

BOD5 removal between planted and unplanted wetlands may be due to microbial

degradation of organics coupled with root zone oxygen input (Klomjek and Nitisoravut,

2005).

Figure 1: Schematic diagram of vertical flow constructed wetland system

(a. Side view b. Aerial view)

Table 1: Physico-chemical characteristics of raw and influent domestic wastewater

Parameters Raw Influent

pH 8.16±0.00 7.86±0.01

E.C ( dS/m) 1.99±0.31 1.77±0.02

Turbidity (NTU) 22.08±0.87 18.16±0.32

TDS (mg/l) 591.06±2.49 477.48±0.96

COD(mg/l) 412.32±3.00 374.34±2.73

BOD5 (mg/l) 157.20±0.86 128.44±2.46

Phosphate (mg/l) 18.16±0.32 22.08±0.87

Nitrate (mg/l) 91.50±2.64 78.98±1.01


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Figure 2: Effect of planted and unplanted VFCW on the pH of domestic wastewater

0

0.5

1

1.5

12 24 36

dS

/m

Hours

Effect of planted and unplanted VFCW on the

E.C of domestic wastewater

Planted

Unplanted

Figure 3: Effect of planted and unplanted VFCW on the EC of domestic wastewater

0

1

2

3

4

5

6

7

12 24 36

NT

U

Hours


turbidity of domestic wastewater

Planted

Unplanted

Figure 4: Effect of planted and unplanted VFCW on the turbidity of domestic wastewater

7.45

7.5

7.55

7.6

7.65

7.7

7.75

7.8

12 24 36

Hours


pH of domestic wastewater

Planted

Unplanted


domestic wastewater


1502

0

50

100

150

200

12 24 36

mg

/l

Hours


TDS of domestic wastewater

Planted

Unplanted

Figure 5: Effect of planted and unplanted VFCW on the TDS of domestic wastewater

0

50

100

150

12 24 36

mg

/l

Hours


COD of domestic wastewater

Planted

Unplanted

Figure 6: Effect of planted and unplanted VFCW on the COD of domestic wastewater

0

20

40

60

80

12 24 36

mg

/l

Hours


BOD5 of domestic wastewater

Planted

Unplanted

Figure 7: Effect of planted and unplanted VFCW on the BOD5 of domestic wastewater


domestic wastewater


1503

0

2

4

6

8

12 24 36

mg

/l

Hours

Effect of planted and unplanted VFCW on

the PO4 of domestic wastewater

Planted

Unplanted

Figure 8: Effect of planted and unplanted VFCW on the PO4 of domestic wastewater

0

5

10

15

20

25

30

12 24 36

mg

/l

Hours

Effect of planted and unplanted VFCW on

the NO3 of domestic wastewater

Planted

Unplanted

Figure 9: Effect of planted and unplanted VFCW on the NO3 of domestic wastewater

Table 2: Efficiencies of VFCW system with effluent under HRT of 12, 24 and 36 hours

Parameter

% Removal Efficiencies planted

(HRT hours)

% Removal Efficiencies unplanted

(HRT hours)

12 24 36 12 24 36

EC(dS/m) 49.72 54.80 57.63 25.42 40.11

45.76

Turbidity

(NTU) 86.01 90.53 92.90 58.7 60.9 64.76

TDS (mg/l) 78.21 82.10 84.66 62.73 65.15 67.26

COD (mg/l) 74.89 75.05 80.53 61.01 62.86 64.70

BOD5 (mg/l) 69.74 71.96 75.49 48.55 52.35 56.45

PO4 (mg/l) 78.71 81.34 83.51 60.14 62.86 64.45

NO3(mg/l) 78.02 85.72 88.48 47.13 53.46 61.8


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The Phosphate (PO4) of domestic wastewater and influent samples were observed to be

18.16 and 22.08 mg/l. The increased phosphate content after the settling period of the

study experiment might be by the conversion of long-chained polyphosphates to short

chained phosphates during the sedimentation (Korkusuz, 2004). The effluent from the

planted VFCW had a mean PO4 of 4.7, 4.12, 3.64 mg/l and unplanted bed had a mean

PO4 of 7.94, 7.26 and 6.76 mg/l during different retention time 12, 24 and 36 hours

respectively. The mechanisms of phosphate adsorption, complexation and precipitation,

plant uptake and biotic assimilation might have reduced the phosphate level in the

wastewater (Watson, et al., 1989).

The Nitrate (NO3) of domestic wastewater and influent samples were observed to be

91.50 and 78.98 mg/l. The effluent from the planted VFCW had a mean NO3 of 17.36,

11.28, 9.10 mg/l and unplanted bed had a mean NO3 of 30.76, 26.76 and 23.17 mg/l

during different retention time 12, 24 and 36 hours respectively. Nitrate removal can be

attributed to any or all the mechanisms-uptake by plants, volatilization of ammonia or

bacterial nitrification/denitrification. Of these, bacterial process has the most effect on the

overall nitrogen removal (Russel et al., 1994: Weisner et al., 1994,). Nitrosomonas and

nitrobacter nitrify ammonia into nitrates which is available for plant and microbial uptake.

Denitrifying bacteria convert nitrate into gaseous nitrogen, which gets volatilized (Brady

et al., 2007).

4. Conclusion

The vertical flow constructed wetland system has been proven to be an effective system

which utilizes the interaction of emergent plant, microorganisms and media in the

removal of pollutant. It was also observed that the higher the Hydraulic Retention Time

increased the effectiveness of wetland system. Typha augustifolia and its rhizospheric

microorganisms contributed strongly to the degradation of organic matter and

assimilation of the released nutrients, a good capacity of the plant for absorbing nutrients.

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Efficacy of Typha angustifolia based vertical flow constructed … · Efficacy of Typha angustifolia based vertical flow constructed wetland system in pollutant reduction of domestic