dùng thực vật trong làm sạch nước thải 2

8/16/2019 dùng thực vật trong làm sạch nước thải 2

1/12

Temperature

inuence on nitrogen removal in a hybrid constructedwetland

system

in

Northern

Italy

Anna Mietto, Marco Politeo, Simone Breschigliaro, Maurizio Borin *

Department of Agronomy, Food, Natural Resources, Animals and Environment –DAFNAE, Agripolis, University of Padova, Viale Dell’ Università 16, 35020

Legnaro, Padova, Italy

A R T I C L E I N F O

Article history:

Received 7 March 2014Received in revised form 16 September 2014

Accepted 9 November 2014

Available

online

xxx

Keywords:

Vertical ow (VF)

Horizontal ow (HF)

Temperature

VF operation mode

Phragmites australis

Canna indica

A B S T R A C T

The objective of this research was to investigate the ef ciency and seasonal performance of a full-scale

hybrid constructed wetland system (HCW) in reducing total nitrogen (TN), ammonia nitrogen (NH4-N)and nitrate nitrogen (NO3-N). HCWwith a total areaof about 130m

2 and hydraulic load of 2m3/day was

composed of three subsurface ow vertical systems (VF), working in parallel and one horizontal (HF)

connected in series. The system was loaded daily with synthetic wastewater having an average

concentration of TNof 250mg/L (about125mg/L of NH4-Nand125mg/L ofNO3-N). Watersamples were

collected and analyzed from May to July 2011 and from January 2012 to July 2012. Variations were

observed in nutrient removal performance related to temperature.

During thewhole monitoringperiodmedian reduction ef ciency (RE)in the HCWwas TN95%, NH4-N

95% and NO3-N 93%, although three sub-periods characterized by different performances have been

observed.Duringthe rstperiod (fromMayto July 2011) theRE waspositive for the three nitrogen forms

considered, whereas from January to the end of March 2012 the RE was lower, particularly for TN and

NO3-N. From April 2012, when the temperature rose above 14.8C, there was an increase in the

performance that reached the 2011 values.

Internal production of NO3-N was observed, mainly in the VF systems between January and March

2012. The median removals ofmass pollutants per m2 of HCW per day were TN3.1g/m2/d, NH4-N 1.5g/

m2

/d, NO3-N 1.5g/m2

/d. Segmented regression analysis identied a breakpoint at 14.2

C forwastewatertemperature thatcaused variationsin TNand NO3-N concentrationreductionperformances.According to

this approach the abatementwasalways positivelycorrelatedwith temperature, butdifferent regression

slopes were obtained below and above the breakpoint. In particular, with lower

temperature the

abatementof NO3-N and TN increased by 1.7 and2.0%per C of temperature increase;with temperature

higher than 14.2C the increase in abatement due to increased temperaturewas sharper, especially for

NO3-N.

ã 2014 Elsevier B.V. All rights reserved.

1. Introduction

Wetland technology emerged in the 1950s and the use of

controlled wetland environments for wastewater treatment hassince been developed. The major nitrogen removal mechanism is

achieved by biological processes that convert the organic and

ammonia nitrogen to nitrate in an aerobic environment (nitrica-

tion) and then reduce the nitrate to nitrogen gas in an anoxic

environment (denitrication) (Leverenz et al., 2010). Volatiliza-

tion, absorption and plant uptake play a much less important role

in CWs (Kadlec and Wallace, 2009). The use of vertical-subsurface

ow constructed wetland (VF) systems became very popular in

Europe in the 1990s compared to the horizontal system (HF) due to

their enhanced ability to oxidize ammonia nitrogen (Stefanakisand Tsihrintzis, 2012). Single-stage CWs cannot achieve high

removal of total nitrogen because of their inability to provide both

aerobic and anaerobic conditions at the same time.

The design of hybrid constructed wetland systems (HCW)

(combination of vertical and horizontal ow systems) has been

proposed to exploit the anoxic areas within the horizontal bed for

denitrication (Cooper et al., 1999; Kadlec and Wallace, 2009;

Molle et al., 2008). HCW systems have been used to treat domestic

or municipal sewage (Brix et al., 2003; Canga et al., 2011), and more

recently for many other types of wastewater including agro-* Corresponding author. Tel.: +39 0498272838; fax: +39 0498272839.

E-mail address: [email protected] (M. Borin).

http://dx.doi.org/10.1016/j.ecoleng.2014.11.027

0925-8574/ã 2014 Elsevier B.V. All rights reserved.

Ecological Engineering 75 (2015) 291–302

Contents

lists

available

at

ScienceDirect

Ecological

Engineering

journal homepage: www.else vie r .com/locate/e coleng

mailto:[email protected]:[email protected]://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://www.sciencedirect.com/science/journal/09258574http://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.elsevier.com/locate/ecolenghttp://www.sciencedirect.com/science/journal/09258574http://dx.doi.org/10.1016/j.ecoleng.2014.11.027http://dx.doi.org/10.1016/j.ecoleng.2014.11.027mailto:[email protected]://crossmark.dyndns.org/dialog/?doi=10.1016/j.ecoleng.2014.11.027&domain=pdf


2/12

industrial (Comino et al., 2011), agricultural (Borin et al., 2013;

Hunt and Poach, 2001; Kantawanichkul et al., 2003) and landll

leachate (Mæhlum et al., 1999).

As reported in several previous studies (Akratos and Tsihrintzis,

2007; Kadlec and Wallace, 2009; Kotti et al., 2010; Kuschk et al.,

2003; Vymazal, 1999) temperature is one of the principal variables

that mainly inuences biological activity and so the seasonal

performances of constructed wetlands. Hill and Payton (1998)

reported that the ef ciency of treatment in a constructed wetland

decreases at low temperature primarily due to reduced biotic

activity. Kadlec and Reddy (2001) studied the temperature

dependence in surface ow wetlands on removal of contaminants.

They concluded that the performance of wetlands in treating

wastewater is seasonally cyclic and the biotic reactions are reduced

at temperatures lower than the optimal range (20 to 35 C). Kadlec

(2006) pointed out three reasons for the importance of water

temperature in treatment wetlands: (1) temperature modies the

rates of several key biological processes, (2) temperature is

sometimes a regulated water quality parameter, and (3) water

temperature is a prime determinant of evaporative water loss

processes. Several biogeochemical processes that regulate the

removal of nutrients in wetlands are affected by temperature, thus

inuencing the overall treatment ef ciency (Kadlec and Reddy,

2001).The goals of this study are (1) to investigate the ef ciency of a

full-scale hybrid constructed wetland system (HCW) in reducing

total nitrogen (TN), ammonia nitrogen (NH4-N) and nitrate

nitrogen (NO3-N); (2) study the effects of temperature on nitrogen

forms abatement; (3) conrm or identify a wastewater tempera-

ture breakpoint that causes variation in nutrient removal perform-

ances; (4) study the effects on vertical ow cells performance in

relation to different vegetation, medium and operational mode.

2.

Materials

and

methods

2.1. Hybrid constructed wetland con guration and characteristics

The HCW was located at a private pig farm in Carmignano diBrenta, Padova, in Veneto Region, NE Italy, (E: 11419.58 ; N:

453745.16; 46 m a.s.l).

It was built in 2008 and designed to provide tertiary treatment

of 2 m3/d of pre-treated liquid fraction of pig slurry ef uent. The

design guidelines provided by APAT were based on municipal

wastewater treatment wetlands (APAT, 2005).

The HCW system is composed of three vertical-subsurface ow

wetlands (VF1–VF2–VF3) in parallel with a total area of 21 m2,

followed by one horizontal-subsurface ow wetland (HF) con-

nected in series (105 m2) (Fig. 1).

The entire system was designed for a hydraulic retention time

(HRT) of 7 days as minimum. Each VF unit was built in concrete

(length: 10 m; width: 1 m; depth: 0.7 m). Three different plastic

sheet liners were placed inside each cell to prevent leakage and

contact of wastewater with groundwater. The layers from bottom

to top were: nonwoven geotextile sheet with a basic weight of

400–800 g/m2 and thickness 1 mm; interlayer EPDM geo-mem-

brane; nonwoven geotextile sheet with a basic weight of 400–

800 g/m2 and thickness 1 mm. The rst two cells were lled with

washed gravel: grain size 10–20mm (d10= 8.5 mm; d60= 9.7 mm)

with porosity of 40%. The rst one (VF1) was vegetated with Canna

indica L., the second (VF2) with Phragmites australis (Cav.) Trin. Ex

Steud (common reed). The third (VF3), planted as VF2 cell, was

lled with a 0.10m deep gravel layer (grain size 10–20 mm)

overlying a 0.10m deep coarse sand (grain size 3–5mm) and

zeolite (grain size 5–10 mm) transition layer and a 0.30 m deep

gravel drainage layer (10–20 mm in size). The main components of

the zeolite were: chabasite 60%, K-feldspar 13%, phillipsite 5%, mica

5% and augite 2%. The synthetic wastewater was distributed evenly

over the surface of the VF beds by a pressurized PVC distributionpipe 75 mm in diameter that ran along the VF wetland units. Three

lters with interchangeable cartridges were placed in series at the

inlet of VF system. The lters were used to remove particles larger

than 1 mm from the feeding tank ef uent, and were installed to

minimize the accumulation of solids in the inuent distribution

pipe. At the inlet of each VF wetland units a water meter with ve

digit mechanical counter was attached at the distribution pipe to

measure the incoming wastewater quantity delivered to each cell.

A drainage pipe (diameter 75 mm and length 10 m) was located on

the bottom of each VF cell in order to facilitate ef uent collection.

The drainage pipe was connected on one side to a 100 mm

diameter collection pipe that discharged the ef uent from the bed

to a manhole that had a water level control structure equipped

with a siphon pipe where a timer-controlled pump was placed(Fig. 2).

The siphon maintained water level at 0.30 m from the surface in

each VF cell. A 200 watt power submersible pump installed in the

same manhole was used to drain the porous media and transport

the leachate to separate sumps (OUT VF1, OUT VF2, OUT VF3). The

wastewater discharged from each VF sump was collected in a

Fig. 1. HCW system dimensions in overhead view. Sampling points: (1) inuent, (2) VF1 ef uent, (3) VF2 ef uent, (4) VF3 ef uent, (5) inuent to HF, (6) HF ef uent (nal

ef uent).

292 A. Mietto et al. / Ecological Engineering 75 (2015) 291– 302


3/12

common sump (OUT VF) (length: 1.2 m; width: 0.8 m; depth:

0.66 m). The VF ef uent was then transferred with a submersible

sump pump with an integrated oat switch to the horizontal

subsurface ow wetland. A water meter with vedigit mechanical

counter attached to the submersible pump outlet measured the HF

incoming wastewater volume.

The horizontal-subsurface ow wetland (HF) was a basin 25 m

long, 4 m wide and depth 0.7 m with a bottom slope of 1%. The

bottom and sides of the basin were waterproofed with the same

plastic sheets used for VF cells. The inlet and the outlet sections

were lled using two strips of coarse-rock material (grain size 50–

100 mm) along two opposite edges of the basin, with washed

gravel: grain size 10–20mm (d10= 8.5 mm; d60= 9.7 mm) with

porosity

of

40%

placed

in

the

central

area.

At

the

HF

inlet

adistributor pipe was buried immediately below the surface

(diameter 100 mm), placed horizontally and perpendicular to

the direction of ow. At the outlet, a similar collector pipe was

buried at the bottom. The HF ef uent volumes were measured by a

water meter, collected in an interred tank and recycled for cleaning

the piggery. The wetland was planted in April 2008 with

Phragmites australis (Cav.) Trin. Ex Steud. (common reed).

2.2.

System

mode

operation

From May 2011 the HCW system was loaded daily with

synthetic wastewater. The wastewater was prepared daily in the

feeding tanks just before the feeding by dissolving ammonium

nitrate fertilizer 26% N (13% nitrate and 13% ammonia) in 1.7 m3 of

fresh water. The average concentration was 250.3 (3.7) mg/L of

TN, 124.5 (2.5) mg/L of NO3-N and 124.9 (3.2) mg/L of NH4-N.

The feeding tank (pump chamber) consisted of a 5 m 0.7 m

concrete tank 0.7 m deep, with a submersible water pump inside

used to load the wastewater to each VF unit. The pump was

controlled by two programmable timers in series. One timer

dictated the time of loading cycles and was set to work once per

day, with one loading cycle in the morning from 10 am to 12 am.

The other timer dictated the loading time per cycle (one minute)

and the time between pumping events within each loading cycle

(every 4 min). Daily wastewater ow rate of 1.7m3 was evenly

distributed to all three VF cells with average ow rate of 565 L/day

per cell.

Two programmable timers in series controlled the submersible

water pump placed inside the water level control structure of each

VF. The rst timer dictated the time of discharging cycles and was

set to work once per day, the other timer dictated the discharging

time per cycle (one minute) and the time between pumping events

within each discharging cycle (every 4 min).

To provide suf cient oxygen transfer for nitrication, load and

discharge cycles of VF unit were set with anoxic/oxic (A/O) steps.

The A/O stages were generated with rapid water ow through the

lter media, the phenomenon called passive air-pump (Greenet al., 1998). During the investigation period two different daily

operation modes (DOM) of the vertical-ow system were tested

(Table 1). We chosen this loading scheme to manage the VF cells

with alternation of period of saturation and unsaturation as

describe below. The rst (DOM 1) was applied from May to July

2011 and from January to 11th July 2012 with a feeding strategy

consisting of 2 h of wastewater inow, followed by 6 h of

completely full cell, 2 h of discharging and 14 h of completely

empty cell in order to assist the oxidation. This “intermittent

feeding” mode was chosen to provide good oxygen transfer to the

water phase. DOM 2 was applied from 11th to 25th July 2012,

programming 14 h of fully lled cells and 6 h of empty cells.

2.3. Sampling, chemical analysis and data elaboration

Water samples were collected and analyzed from May to July

2011 and from January to July 2012 from inow (1; IN), outow of

VF1 (2; OUT VF1), outow of VF2 (3; OUT VF2), outow of VF3 (4;

OUT VF3), inow of HF (5; IN HF), outow of HF and nal ef uent

(6; OUT HF) (Fig. 1). IN sample was taken at the beginning of each

cycle, after synthetic feed preparation, OUT VF of each cell and IN

HF were taken at the end of the daily feeding period of the cycle

(after 6 h from inlet), and OUT HF sample was taken according to

the retention time (after 7 days from the start of the cycle).

Monitoring consisted of thirty seven weekly samplings during the

whole investigation period, collecting 211 samples.

In situ, measurements of pH, electrical conductivity (EC),

dissolved

oxygen

(DO),

wastewater

temperatures

(T )

and

redox-potential (E h), were taken with a Hach Lange HQD 40d multi-

parameter meter with interchangeable probes according to

standard methods (APHA, 1998). Before testing, each probe was

carefully calibrated according to the manufacturer's procedures.

Samples were collected, preserved at 4 C and then analyzed

within a short time.

Total nitrogen (TN), ammonia-nitrogen (NH4-N) and nitric-

nitrogen (NO3-N), were determined photometrically using a Hach-

Lange DR-2800 spectrophotometer and adequate cuvette test kits

(cuvette-tests LCK 338, 302, 340), (Hach-Lange,1989), according to

DIN (1985). Adequate sample dilutions were made with a stock

supply of deionized water.

Air temperature, humidity, solar radiation, rainfall volumes,

wind

speed

and

direction

were

recorded

every

day

from

the

Fig. 2. Schematic representation (not to scale) of water level control structure of

each VF cell.

Table 1

Daily

operation

modes

of

the

vertical-ow system. DOM1: from May to July

2011 and from January to 11th July 2012; DOM2: from 11th to 25th July 2012.

DOM 1 DOM 2

Phase VF unit cycle Duration

(h)

Schedule Duration

(h)

Schedule

I loading cycle 2 10 a.m.–12 a.

m.

2 10 a.m.–12 a.

m.

II wet period 6 12 a.m.–6 p.

m.

14 12 a.m.–2 a.

m.

III

unloading

cycle

2

6

p.m.–8

p.m.

2

2

a.m.–4

a.m.

IV dry period 14 8 p.m.–10 a.

m.

6 4 a.m.–10 a.

m.

A. Mietto et al. / Ecological Engineering 75 (2015) 291– 302 293


4/12

beginning of the experiment by a meteorological station installed

at the site. Evapotranspiration (ETO) was calculated with the FAO

56 Penmam-Monteith equation (Allen et al., 1998) for short

reference crop ETos (Allen et al., 2005).

The data series of the parameters did not follow normal

distribution even after transformations. Thus, statistical analyses

were carried out with the Kruskal–Wallis nonparametric test to

compare the six sampling positions (IN, OUT VF1, OUT VF2, OUT

VF3, IN HF, OUT HF) and Box and Whiskers were used to display the

variability.

In this study, the performance comparison of each HCW unit

was based on three different approaches:

(a) concentration percentage abatement (A), calculated on the

rst quartile (Q1), second quartile (Q2; median) and third quartile

(Q3) concentration values as (Eq. (1)):

A% ¼ Cin Coutð Þ

Cin

100 (1)

where Cin is inow concentration (mg/L) and Cout is outow

concentration (mg/L);

(b) Reduction ef ciency (RE) calculated as (Eq. (2)):

RE% ¼ Cin Vinð Þ Cout Voutð Þ

Cin

Vinð

Þ

100 (2)where Cin is inow concentration (mg/L), Vin is average inow

volume of synthetic wastewater applied (m3/d) with daily rainfall

volume (mm/d) included, Cout is outow concentration (mg/L),

Vout is outow volume detected at the outlet of the unit (m3/d);

(c) Areal load reduction (ALR), expressing the removed

pollutants mass per m2 of CW and time (g/m2/d). ALR is a useful

parameter to assess system ef ciency (Stefanakis and Tsihrintzis,

2012).

In addition, segmented linear regression analysis (or broken-

line regression) with a non-parametric approach developed by

Pettitt (1979) was used to identify a change-point of wastewater

temperature that caused variation in nutrient percentage abate-

ment. For this purpose, the Flat Steps method (Bai and Perron,

2003)

was

used,

implemented

in

the

Strucchange

library

of

R software (Zeileis et al., 2003). Partial F -test in one-way analysis of

variance was used to determine any signicant differences at

p < 0.05.

3. Results and discussion

3.1. Wastewater, air temperature and evapotranspiration

During the rst monitoring period (May– July 2011), slight

differences in air and wastewater temperatures were found at

different HCW sampling points (Fig. 3). Inlet temperature values

ranged between 20.5 and 22.3 C. These values result as being more

ef cient for biological N removal (range of 20–25 C) as reported by

Sutton et al. (1975) since ambient temperature positively

inuences microbial activity and diffusion rates (Phipps and

Crumpton, 1994).

During the second period (January– July 2012) air temperature

vs inlet wastewater showed two different trends: in cold months

(January–March) air temperature (average 6.3 C) was lower than

the inlet wastewater (average 11.9 C) whereas in the warm period

(from April to July) an opposite tendency was observed, especially

in June– July. The freshwater temperature used to prepare synthetic

wastewater (average 14.2 C) showed less variation than the other

sampling points during the second part of the monitoring period,

ranged between 9.2 and 17.7 C. Until the beginning of March

2012 wastewater temperature measured from VF unit (average

8.1C) was lower than inlet (average 11.1 C), whereas higher

values (average 19.8 C) were observed in VF with respect to theinlet (average 15.3 C) till the end of the experimental period. HF

temperature followed the same tendency observed for VF

wastewater (Fig. 3).

The daily ETO results were in accordance with the data found in

the literature for similar conditions (size, latitude and measure-

ment method) (Borin et al., 2011). The time pattern of the

cumulative ETos in the rst period, from May to September 2011,

showed an average daily ETO of 5.90 mm; from October 2011 to

March 2012, plants consumed 1.97mm/day on average. In the

winter-spring period, daily ETO was 5.04 mm.

3.2. On site parameters

During rst monitoring period (May– July 2011), electricalconductivity (EC) of the inuent wastewater was higher than

1600 mS/cm and increased after passage through VF cells. HF

slightly increased this to a median value of 1840 mS/cm (Fig. 4).

Fig.

3.

Mean

air

and

wastewater

temperature

at

the

sampling

points

of

the

HCW

system

during

the

monitored

period.



5/12

Fig. 4. Variation of EC, pH, DO, E h at the sampling points of the HCW system during the monitored period.



6/12

Fig. 5. Nitrogen forms concentration at the sampling points of the HCW system during the monitoring period.



7/12

During the second monitoring period (January– July 2012), the

incoming EC did not exceed 1600 mS/cm until 28th March, then

rose to higher values until the end of monitoring: this is probably

related to the increasing water temperature that promoted

dissolving ammonium nitrate in water. The same trends as the

previous monitoring period were observed for VF and HF, mainly

due to substrate biolm interaction that may result in soluble salt

release from the media to the water (Stefanakis and Tsihrintzis,

2012). EC seasonal variations were observed during summer each

year probably due to increased evapotranspiration (May–Septem-

ber 2011 and April– July 2012) and plant growth, as reported by

Hench et al. (2003).

The median inuent pH during the rst and second monitoringperiod was neutral or slightly alkaline 7.64 0.04. HF unit

exhibited alkaline pH values from 21st March 2012 till the end

of the monitoring period (Fig. 4). As nitrication proceeds

optimally at pH between 7.5 and 8.5 (Platzer, 1996), the pH values

were optimal in all three VF beds. However pH values measured in

the HF unit were not optimal for denitriers that operate best in

the range between 6.5 and 7.5 (Paul and Clark, 1996). Furthermore

ammonia nitrogen loss through volatilization was negligible since

it generally requires a pH of 9.3 ( Jing and Lin, 2004).

Median dissolved oxygen concentration value at the inlet was

constant (4.17 0.05 mg/L) during the whole investigation period.

DO concentration above 1.5 mg/L is essential for nitrication to

occur (Ye and Li, 2009). During rst monitoring period DO

concentration increased after passage through VF cells to the

median value of 4.57 mg/L probably due to aerobic conditions

provided by the oxic stage during DOM 1 of the vertical-ow

system. The DO detected at the ef uent of HF cell varied from

0.14 to 0.28 mg/L. The same trends were observed during the

second monitoring period in VF unit: from the beginning of March

to 11th July 2012 a slight increase appeared in ef uent DO

concentration, possibly due to plant growth and enhanced oxygentransfer to the plant roots. From 11th July 2012 to the end of

monitoring average DO concentration from VF unit ef uent

decreased from 4.18 to 2.74 mg/L due to the longer anoxic stage

promoted by DOM 2. HF ef uent DO concentration was very low

during end winter-early spring, from May to 4th July 2012 it

slightly rose with the common reed re-activation (Fig. 4).

Redox potential (E h) variations within a range of a few hundred

mV from reduced (0 mV) to moderately oxidized redox conditions

(+270 mV) were observed (Fig. 4). During the rst period, median

wastewater redox potential value of 269 decreased to 206 mV after

VF cells passage. This suggests that the VF system provided

conditions suitable for nitrication, but not for denitrication. The

HF outow E h decreased drastically in the range from +10 to 0 mV

probably inducing favorable (anaerobic) conditions suitable formicrobial denitrication. The second period followed the same

trend as the rst. From 11th July 2012 to the end of monitoring E hfrom VF unit ef uent decreased drastically, possibly due to the

prolonged period of saturation of the cell promoted by DOM 2, as

demonstrated by DO values. In the HF cell Eh patterns differed

between the warm and cold periods probably affected by

wastewater temperature. Increase of temperature during the

warm period accelerated biochemical processes including bacteria

activity (Kadlec and Reddy, 2001). Moreover, oxygen solubility in

Fig. 6. Box-plot diagrams of nitrogen forms concentration (mg/L), at the sampling points of the HCW system during the monitoring period. Different letters indicate

signicant differences at p = 0.05 by Kruskal–Wallis test.

Table 2

Slope and R2 for the linear relationships among wastewater temperature and

nitrogen forms abatements and for values below and above breakpoint.

Nitrogen

form

Linear

regression

Values

below

breakpoint

Values

above

breakpoint

Slope R 2 Slope R 2 Slope R 2

TN 3.63 0.88 2.01 0.38 2.9 0.7

NH4-N 0.62 0.66 0.36 0.4 0.44 0.23

NO3-N 6.5 0.83 1.7 0.1 6.6 0.62

Fig. 7. Wastewater temperature and percentage abatement correlation charts with breakpoints for nitrogen forms.



8/12

water decreases with increasing temperature, so as a result, Eh

decreased, as also reported by Dušek et al. (2008) (Fig. 4).

3.3. Nitrogen forms concentrations

From May to July 2011, TN concentration decrease was clear and

constant accomplished by VF unit with median value of 173.4 mg/L and HF unit with 105.6 mg/L. With low temperatures measured

during the rst part of the second period (January–March 2012,

average temperature 10.4 C), TN concentration abatement was

negligible. Then, from the end of March to the rst ten days of May

following an increase in temperature from 15.5 to 20.4 C the

concentrations at the outlets of VF and HF progressively decreased.

Finally, when mean wastewater temperature of 20.2 C was

reached, TN outlet concentrations showed similar values as the

year before in the same period (Fig. 5).

The VF cells provided outlet values statistically lower than the

inlet ones; differences were also found among cells, with lower

values in VF3 with respect to VF1, probably related to the combine

effect of different plant and porous media types. The performance

of VF2 and VF3 units, both planted with P. australis, were similarand the statistical analysis showed no signicant differences. The

HF system lowered the inlet median value from VF unit from

146 mg/L to a nal discharge concentration of 114mg/L and slightly

increased the variability (Fig. 6).

Ammonia median concentration measured from VF and HF unit

showed a decreasing trend in both monitored periods. From May to

July 2011 median NH4-N concentration at VF outlet was 68.3 and

48.6 mg/L in HF. From January to July 2012 it was 68.4 and 50 mg/L,

respectively. The different wastewater temperature did not

inuence ammonia values at the outlet of wetland cells. No

statistically signicant differences were found between VF1 and

VF2 even though different plant species were used. Signicant

differences were found between VF3 and the rst two VF cells

(VF1

and

VF2)

probably

due

to

composition

of

the

medium

layerwhich comprised zeolite stones that could absorb NH4

+ (Nguyen

and Tanner, 1998) (Fig. 6).

During the rst period, NO3-N trend concentrations followed

the same temporal pattern as the other nitrogen forms, with

decreasing values passing through VF and then HF. During the

second period, in the cold season ef uent concentrations from VF

and HF unit exceeded inuent with median values of 179.7 and

182.7 mg/L respectively. With increasing wastewater temperature

during the warm season, measured concentration decreased

reaching values found in the rst period (Fig. 5). Statistical

differences were found only between inlet and outlet of HCW

system (Fig. 6). As reported by Kuschk et al. (2003), the microbial

activities related to nitrication and denitrication can decrease

considerably

at

water

temperature

below

15

or

above

30

C.

In

particular, the activity of denitrifying bacteria in CWs is generally

more robust in spring–summer seasons than in autumn–winter

(van Oostrom and Russel, 1994).

3.4.

Effect

of

wastewater

temperature

In our study, correlation analysis was performed betweenpercentage abatement (A%) for nitrogen forms calculated on a

weekly basis for all 37 weeks of monitoring and the corresponding

average wastewater temperatures during the whole monitoring

period. We focus on the results obtained for the whole HCW.

First, linear regressions between A% and temperature were

calculated for the nitrogen forms, obtaining signicant relation-

ships, with higher R2 for TN and NO3-N (Table 2). The regression

slope for NO3-N suggested a sharp inuence of temperature on

abatement, which increased by 6.5% with every 1 C. On the

contrary, the effect of temperature on NH4-N was less marked, as

suggested by the lower R2 and regression slope.

In a second step a segmented regression analysis was conducted

according to Bai and Perron (2003) to identify any presence of a

breakpoint of wastewater temperature that caused variations innutrient abatement performances. The segmented analysis model

was signicant with respect to the linear regression for TN and

NO3-N and evidenced breakpoints at 14.2C for both nitrogen

forms (Fig. 7).

According to this approach the abatement was always

positively correlated with temperature, but different regression

slopes were obtained below and above the breakpoint. In

particular, with lower temperature the abatement of NO3-N and

TN increased by 1.7 and 2.0% per C of temperature increase; with

temperature higher than 14.2 C the increase in abatement due to

increased temperature was sharper, especially for NO3-N (6.6%

every 1 C) (Table 2).

Nitrogen pollutants abatement statistics were calculated for

wastewater

temperatures

below

and

above

the

breakpointidentied with segmented regression analysis (Table 3). As

previously mentioned, higher performance was observed at

temperature above breakpoint for both TN as NO3-N. In particular,

NO3-N median abatement that was negative below 14.2C, became

consistent above this critical temperature.

3.5. Nitrogen RE and ALR

Median TN RE during the rst period (from May to July 2011)

was 63%, 83% and 96% for VF, HF unit and SIF respectively (Fig. 8).

During the second period from January to the end of March

2012 the RE was lower, with values between 11% and 40% for VF

unit and the entire system. Considering the same period negative

reduction

values

were

found

for

HF

unit

(ranging

from

0.7

and

Table 3

Nitrogen pollutant percentage abatement (A) statistics for wastewater temperatures above and below identied breakpoint.

Temperature below break point Temperature above break point

VF1 VF2 VF3 HF HCW VF1 VF2 VF3 HF HCW

TN (A%)

Minimum 3.5 6.1 4.4 8.9 5.3 16.2 7.8 22.9 7.4 22.7

First quartile (Q1) 1.2 3.6 3.8 8.7 0.5 18.8 29.5 37.8 14.7 53.8

Median (Q2) 5.3 3.8 7.1 4.9 5.1 21 34.4 42.6 19.9 57.5

Third quartile (Q3) 12.4 8 10.8 2.3 8.1 24.3 36.4 46.7 29.2 60.9

Maximum 17.7 26 35 13.1 41.8 27.1 42.1 50.4 39 63.7

NO3-N (A%)

Minimum 54.4 49.8 61.6 2.7 55.7 28.5 22.3 20.7 1.8 27

First quartile (Q1) 50.6 46.7 51.2 2.1 51.3 10.4 16.7 18.2 14.6 35.6

Median (Q2) 47.8 41.8 47.1 0.2 47.3 13.4 26 26.5 25.3 45.4

Third quartile (Q3) 44.3 39.9 39.9 1.2 45.6 14.4 28.7 30.4 30.6 59.3

Maximum 3.2 3.3 2.6 2.9 1.8 22.1 33.8 46.2 52 68.4



9/12

Fig. 8. Nitrogen forms RE (%) at the sampling points of the HCW system during the monitoring period.



10/12

6%). From April 2012, when the temperature rose above14.8 C,

there was an increase of TN reduction in the system that reached

the 2011 values (Fig. 8).

VFand HF system provided a NH4-N reduction pattern similar to

that found for TN during 2011,with values ranging from 57% to 94%

in the entire system during the whole monitoring period (Fig. 8).

Fig. 9. Nitrogen forms ALR of the HCW during the monitored period.



11/12

VF reduction was slightly higher during the warm period of 2012

(median value 71%) than cold period of the same year (median

value 43%). The HF system performed better during the last

monitoring period, with median reduction ranging between 35

and 87%.

Median NO3-N reduction ef ciency during 2011 was higher forHF (85%) than VF (57%) (Fig. 8). During the cold period of

2012 negative reduction values were observed for VF unit and in

the SIF. The negative RE value (30%) rose from the end of March

until reaching, at the end of the investigation period, a value higher

than 60% in VF.

The median removals of mass pollutants per m2 of HCW per day

were TN 3.1 g/m2/d, NH4-N 1.5 g/m2/d and NO3-N 1.5 g/m

2/d

(Fig. 9). ALR removals of nitrogen forms showed a different trend

during the rst monitoring period of 2012. In particular, from

January to March 2012 the data reveal a low treatment capability,

probably related to temperature (Stefanakis and Tsihrintzis, 2012).

From April to the end of the monitoring period an increment was

observed: from the initially low performance, it reached the same

results

observed

during

2011

(Fig.

9).

The

combination

of

verticaland horizontal stages ensures the right conditions to obtain a

higher nitrogen removal performance. Moreover, when consider-

ing a year of operation, we can suppose that the HCW would

remove approximately 1.1Kg TN/m2.

3.6. Comparison among vertical systems

Nitrogen pollutant reduction ef ciency (RE) and areal load

reduction (ALR) of VF system measured during DOM1 and

DOM2 are presented in Table 4. The performance comparison

was made between two loading cycles of each DOM with the same

conditions (air and wastewater temperatures). In particular, we

considered the subset data from the last two weeks of DOM1 (from

27th

June

to

11th

July

2012)

and

the

data

of

the

two

weeks

of

DOM2 (from 11th to 25th July 2012). DOM 1 allowed higher RE and ALR

to be obtained, probably due to the longer empty period that

promoted better oxidative conditions. Lower average RE values for

TN (varying between 64.1 to 68.3%) and NH4-N (varying between

68.6 and 73.1%) were found with DOM 2. However RE values for

NO3-N were quite similar to those observed during DOM 1.

VF systems planted with P. australis (VF2 and VF3) showed

better performance in TN reduction ef ciency (70.3 and 70.5%,

respectively) than VF1 (63%), planted with C. indica. Average NH4-N

reduction ef ciency was 76.3 and 77.3% in VF2 and

VF3 respectively with higher ALR of 8.2 g/m2/d in VF2. NO3-N

values were lower than other nitrogen forms, best RE and ALR

performances were measured in VF2 with 65.4% and 7.1g/m2/d.

4. Conclusions

The system showed higher performance in terms of TN, NO3-N

and NH4-N reduction. Nonetheless, seasonal variations appear to

affect the HCW system performance. Lower ef uent concentra-

tions were observed during the warm period (higher temperature),

especially for TN and NO3-N, whereas the performances amelio-

rated with the increase in wastewater temperature. NH4-N

reduction ef ciency was inuenced by seasonality to a lesser

extent in the VF than the HF.

Higher RE and ALR for TN and NH4-N were obtained with the

rst daily mode of operation (DOM 1) probably related to the dry

period of 14h that seemed to promote the medium layer oxidation

and nitrication process, whilst similar ndings were obtained in

DOM 2 for NO3-N reduction ef ciency. VF systems planted with P.

australis (VF2 and VF3) showed slightly higher performance in TN

reduction ef ciency compared to VF1, planted with C. indica.

Segmented regression analysis identied a breakpoint at 14.2 C

for wastewater temperature that caused variations in TN and NO3-N

concentration reduction performances. According to this analysis

the abatement of NO3-N and TN increased by 1.7 and 2.0% per C

when temperature was below breakpoint; with a temperature

higher than 14.2 C the increase of abatement due to increased

temperature was sharper, especially for NO3-N (6.6% every 1 C)In the VF cells the mode of operation of loading/discharging

cycles induced a sharp variation in DO and E h values; both

decreased passing from 6 h of completely full cells and 14h of

empty cells to 14 h of full cells and 6 h of empty cells. As a

consequence, the NH4-N concentration at the outlet increased and

the reduction ef ciency decreased. Addition of zeolite to the

porous medium reduced the NH4-N concentration and P. australis

gave better results than C. indica.

It is important to highlight that during this study synthetic

wastewater was used and that temperature in the inuent was

affected by the environmental climate conditions. Slurry temper-

ature is usually quite constant during the year, at around 15–17 C

(Politeo,

2013) and

this

can

explain

the

lower

performanceobserved during winter compared to summer season. This has

to be taken into account when considering the effective potential

of using wetland hybrid systems to treat slurry ef uents as a higher

performance can be expected.

Acknowledgment

Research supported by Progetto AGER, grant no. 2010-2220. We

thank Luigi Guarnieri, the owner of the pig farm and the hybrid

constructed wetland, for its kind hospitality.

References

APAT, 2005. Linee guida per la progettazione e gestione di zone umide articiali perla depurazione dei reui civili. Agenzia per la protezione dell'ambiente e per iservizi tecnici, Firenze, Italy.

American Public Health Association (APHA), 1998. Standard Methods for theExamination of Water and Wastewater, 20th ed. American Water WorksAssociation (AWWA), and Water Environment Federation (WPCF), Washington,DC.

Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop Evapotranspiration:Guidelines for Computing Crop Requirements–FAO Irrigation and DrainagePaper 56. FAO, Rome, Italy.

Allen, R.G., Walter, I.A., Elliott, R.L., Howell, T.A., Itensu, D., Jensen, M.E., Snyder, R.L.,2005. The ASCE standardized reference evapotranspiration equation. Am. Soc.Civil

Eng.

Reston,

VA

59

(with

supplemental

appendices).Akratos, C.S., Tsihrintzis, V.A., 2007. Effect of temperature, HRT, vegetation and

porous media on removal ef ciency of pilot-scale horizontal subsurface owconstructed wetlands. Ecol. Eng. 29 (2), 173–191.

Bai, J., Perron, P., 2003. Computation and analysis of multiple structural changemodels.

J.

Appl.

Econ.

18,

1–22.

Table 4

Mean values of nitrogen pollutant reduction ef ciency (RE) and areal load reduction

(ALR) measured during the two last two weeks of DOM1 (from 27th June to 11th July

2012) and DOM 2 (from 11th to 25th July 2012).

DOM1

DOM2

VF1

VF2

VF3

VF1

VF2

VF3

RE (%)

TN 63 70.3 70.5 64.1 68.3 65.5

NH4-N 73.7 76.3 77.3 68.6 72.5 73.1

NO3-N 57.1 65.4 58.8 59.4 63.7 58.4

ALR (%)

TN 13.3 15.3 12.7 13.4 14.7 12.1

NH4-N 7.7 8.2 6.9 7.2 7.8 6.7

NO3-N 6 7.1 5.3 6.2 6.8 5.4


http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0030http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0025http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0020http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0015http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0010http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0005


12/12

Borin, M.,Milani, M., Salvato, M., Toscano, A., 2011. Evaluation of Phragmites australis(Cav:) Trin. evapotranspiration in Northern and Southern Italy. Ecol. Eng. 37,721–728.

Borin, M., Politeo, M., De Stefani, G., 2013. Performance of a hybrid constructedwetland treating piggery wastewater. Ecol. Eng. 51, 229–236.

Brix, H., Arias, C.A., Johansen, N.H., 2003. Experiments in a two-stage constructedwetland system: nitrication capacity and effects of recycling on nitrogenremoval. In: Vymazal, J. (Ed.), Wetlands – Nutrients, Metals and Mass Cycling.Backhuys

Publishers,

Leiden,

The

Netherlands,

pp.

237–258.Canga, E., Dal Santo, S., Pressl, A., Borin, M., Langergraber, G., 2011. Comparison of

nitrogen elimination rates of different constructed wetland designs. Water Sci.

Technol.

64

(5),

1122–1129.

Comino, E., Riggio, V., Rosso, M., 2011. Mountain cheese factory wastewatertreatment

with

the

use

of

a

hybrid

constructed

wetland.

Ecol.

Eng.

37,

1673–1680.

Cooper, P., Grif n, P., Humphries, S., Pound, A., 1999. Design of a hybrid reed bedsystem to achieve complete nitrication and denitrication of domesticsewage. Water Sci. Technol. 40 (3), 283–289.

DIN

(Deutsches

Institut

für

Normung),

1985.

German

Standard

Methods

for

theExamination of Water, Waste Water and Sludge. Deutches Institut für Normung,Berlin.

Dušek, J., Picek, T., Cížková, H., 2008. Redox potential dynamics in a horizontalsubsurface ow constructed wetland for wastewater treatment: diel, seasonaland spatial uctuations. Ecol. Eng. 34 (3), 223–232.

Green,

M., Friedler,

E.,

Safrai,

I.,

1998.

Enhancing

nitrication in vertical owconstructed wetland utilizing a passive air pump. Water Res. 32 (12), 3513–3520.

Hach-Lange, 1989. Water Analysis Handbook. HACH, Company, Loveland, CO, USA.Hench, K.R., Bissonnette, G.K., Sexstone, A.J., Coleman, J.G., Garbutt k, Skousen, J.G.,

2003.

Fate

of

physical,

chemical

and

microbial

contaminants

in

domestic

wastewater following treatment by small constructed wetland. Water Res. 37(4), 921–927.

Hill, D.T., Payton, J.D., 1998. Inuence of temperature on treatment ef ciency of constructed wetlands. Trans. ASAE 41 (2), 393–396.

Hunt,

P.G.,

Poach,

M.E.,

2001.

State

of

the

art

for

animal

wastewater

treatment

inconstructed wetlands. Water Sci. Technol. 44 (11–12), 19–25.

Jing, S.R., Lin, Y.F., 2004. Seasonal effects on ammonia nitrogen removal byconstructed wetlands treating polluted river water in southern Taiwan. Environ.Pollut. 127 (2), 291–301.

Kadlec, R.H., 2006. Water temperature and evapotranspiration in surface owwetlands

in

hot

arid

climate.

Ecol.

Eng.

26

(4),

328–340.Kadlec, R.H., Reddy, K.R., 2001. Temperature effects in treatment wetlands. Water

Environ. Res. 73 (5), 543–557.Kadlec, R.H., Wallace, S.D., 2009. Treatment Wetlands, second ed. CRC Press/Lewis

Publishers, Boca Raton, Florida, pp. 1016.Kantawanichkul,

S.,

Somprasert,

S.,

Aekasin,

U.,

Shutes,

R.B.E.,

2003.

Treatment

of agricultural wastewater in two experimental combined constructed wetlandsystems in a tropical climate. Water Sci. Technol. 48 (5), 199–205.

Kotti, I.P., Gikas, G.D., Tsihrintzis, V.A., 2010. Effect of operational and designparameters on removal ef ciency of pilot-scale FWS constructed wetlands andcomparison with HSF systems. Ecol. Eng. 36 (7), 862–875.

Kuschk, P., Wiebner, A., Kappelmeyer, U., Weibbrodt, E., Kästner, M., Stottmeister, U.,2003. Annual cycle of nitrogen removal by a pilot-scale subsurface horizontalow in a constructed wetland under moderate climate. Water Res. 37 (17),4236–4242.

Leverenz, H.L., Haunschild, K., Hopes, G., Tchobanoglous, G., Darby, J.L., 2010. Anoxictreatment

wetlands

for

denitrication. Ecol. Eng. 36 (11),1544–1551.

Mæhlum, T., Warner, W.S., Stålnacke, P., Jenssen, P.D., 1999. Leachate treatment in

extended

aeration

lagoons

and

constructed

wetlands

in

Norway.

In:Mulamoottil, G., McBean, E.A., Revers, F. (Eds.), Constructed WetlandsReferences

499

for

the

Treatment

of

Landll Leachates. Lewis Publisher/CRCPress, Boca Raton, pp. 151–163.

Molle, P., Prost-Boucle, S., Lienard, A., 2008. Potential for total nitrogen removal bycombining vertical ow and horizontal ow constructed wetlands: a full-scaleexperiment study. Ecol. Eng. 34 (1), 23–29.

Nguyen,

M.L.,

Tanner,

C.C.,

1998.

Ammonium

removal

from

wastewaters

usingnatural New Zealand zeolites. N. Z. J. Agric. Res. 41 (3), 427–446.

Paul, E.A., Clark, F.E.,1996. Soil Microbiology and Biochemistry, second ed. AcademicPress, San Diego, CA, pp. 340.

Pettitt, A.N., 1979. A non-parametric approach to the change-point problem. Appl.Stat. 28 (2), 126–135.

Phipps,

R.G.,

Crumpton,

W.G.,

1994.

Factors

affecting

nitrogen

loss

in

experimentalwetlands with different hydrologic loads. Ecol. Eng. 3 (4), 399–408.

Platzer, C., 1996. Enhanced nitrogen elimination in subsurface ow articialwetlands - a multi stage concept. Proceedings of the Fifth InternationalConference on Wetland Systems for Water Pollution Control, Vienna, AustriaSeptember

15–19,

I/7–1–I/7–9.

Politeo, M., 2013. Performance of hybrid constructed wetland for piggerywastewater treatment. PhD Thesis. University of Padova, pp. 1–134.

Stefanakis, A.I., Tsihrintzis, V.A., 2012. Effects of loading, resting period,temperature, porous media, vegetation and aeration on performance of pilot-scale

vertical ow constructed wetlands. Chem. Eng. J. 181–182 416–430.

Sutton, P.M., Murphy, K.L., Dawson, R.N., 1975. Low temperature biologicaldenitrication of wastewater. J. Water Pollut. Control Fed. 47 (1), 122–134.

van Oostrom, A.J., Russel, J.M., 1994. Denitrication in constructed wastewaterwetlands receiving high concentrations of nitrate. Water Sci. Technol. 29 (4), 7–14.

Vymazal, J., 1999. Nitrogen removal in constructed wetlands with horizontal sub-surface

ow – can we determine the key process? In: Vymazal, J. (Ed.), NutrientCycling and Retention in Natural and Constructed Wetlands. BackhuysPublishers, Leiden, pp. 1–17.

Ye,F.X., Li, Y., 2009. Enhancement of nitrogen removal in towery hybrid constructedwetland to treat domestic wastewater for small rural communities. Ecol. Eng. 35(7),

1043–1050.Zeileis, A., Kleiber, C., Krämer, W., Hornik, K., 2003. Testing and dating of structural

changes in practice. Comput. Stat. Data Anal. 44 (1–2), 109–123.

http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0035http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S0925-8574(14)00598-9/sbref0040http://refhub.elsevier.com/S09

Documents

dùng thực vật trong làm sạch nước thải 2