nutrient retention in an integrated constructed wetland used to treat domestic wastewater
DESCRIPTION
Environ 2011TRANSCRIPT
Nutrient Retention in an Integrated Constructed
Wetland used to Treat Domestic Wastewater
Mawuli Dzakpasu1 , Oliver Hofmann2, Miklas Scholz3,
Rory Harrington4, Siobhán Jordan1, Valerie McCarthy1
1 Centre for Freshwater Studies, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland. 2 School of the Built Environment, Edinburgh Napier University, Edinburgh EH10 5DT, UK
3 Civil Engineering Research Group, the University of Salford, Newton Building, Salford M5 4WT, UK. 4 Water and Environment section, Waterford County Council, Kilmeadan, Co. Waterford, Ireland.
21st Irish Environmental Researchers’ Colloquium
6-8 April, 2011
Presentation outline
• Introduction
o Background
o Objectives
• Case study description
• Materials and methods
• Results
• Conclusions
• Acknowledgements
1
Background • Constructed wetlands are used to treat several
categories of wastewater worldwide.
• Nutrient removal efficiencies are generally
lower and more variable.
• Irish integrated constructed wetlands (ICW)
concept has developed over last decade.
2
Integrated Constructed Wetlands are:
• Multi-celled with sequential through-flow.
• Free water surface flow wetlands.
• Predominantly shallow densely
emergent vegetated.
Background
3
Background
ICW
concept Biodiversity enhancement
ICW conceptual framework
Landscape fit
Water treatment
4
Background
Contaminant removal processes
BIOLOGICAL
PHYSICAL CHEMICAL
TREATED
WATER
INFLUENT
O2 UPTAKE AND TRANSFER
TO ROOT ZONE
5
Objectives
• To evaluate nutrient removal in ICW over a 3-year full-scale operation by:
o establishing a water balance of the system, using hydrological variables of inflow, outflow, precipitation, evapotranspiration, runoff, storage, and assess its effects on nutrient treatment.
o comparing annual and seasonal nutrient removal rates of the ICW.
omodelling kinetics of nutrient removal in the ICW and the influence of water temperature.
6
• Total area = 6.74 ha
• Pond water surface = 3.25 ha
• Commissioned Oct. 2007
• 1 pump station
• 2 sludge ponds
• 5 vegetated cells
• Natural local soil liner
• Current load = 800 pe.
• Mixed black and grey water
Study site description
ICW layout 8
Study site description
Process overview of ICW 9
Materials and methods
• Automated composite
samplers at each pond inlet.
• 24-hour flow-weighted
composite water samples
taken to determine mean
daily chemical quality.
Wetland water sampling regime
10
Materials and methods
Water quality analysis
• Water samples analysed for NH3-N,
NO3-N and PO4-P using HACH
spectrophotometer DR/2010 49300-22.
• N-allylthiourea BOD5 determined with
WTW GmbH OxiTop system.
• Dissolved oxygen, temperature, pH, redox
potential measured with WTW GmbH
portable multiparameter meter. 11
Materials and methods
• Onsite weather station measures
elements of weather.
• Electromagnetic flow meters and allied
data loggers installed at each cell inlet. 12
Data analysis and modelling
Ci and Ce= influent and effluent nutrient concentrations (mg/L),
Qi and Qe = influent and effluent volumetric flow rate of water (m3/d).
q = hydraulic loading rate (m/yr); Q = volumetric flow rate in
wetland (m3/d); A = wetland area (m2); P = precipitation rate (m/d);
ET = evapotranspiration rate (m/d); I = infiltration rate (m/d). 13
Data analysis and modelling
C* = background concentrations (mg/L);
K = areal first-order removal rate constant (m/yr).
14
Results
ICW water budget
52.9%
47.1%
4.2%
56.7%
14.8%
64 ± 371.3 m3 day-1
139 ± 65.7 m3 day-1 39 ± 27.9 m3 day-1
124 ± 77.8 m3 day-1
149 ± 174.7 m3 day-1
11 ± 9.4 m3 day-1
15
Results
1
10
100
1000F
eb-0
8
May
-08
Au
g-0
8
No
v-0
8
Feb
-09
May
-09
Au
g-0
9
No
v-0
9
Feb
-10
May
-10
Au
g-1
0
No
v-1
0
Feb
-11
Co
nce
ntr
ati
on
(m
g/l
)
BOD influent BOD effluent
0
1
10
Feb
-08
May
-08
Au
g-0
8
No
v-0
8
Feb
-09
May
-09
Au
g-0
9
No
v-0
9
Feb
-10
May
-10
Au
g-1
0
No
v-1
0
Feb
-11
Co
nce
ntr
ati
on
(m
g/l
)
Nitrate influent Nitrate effluent
0.001
0.010
0.100
1.000
10.000
Feb
-08
May
-08
Au
g-0
8
No
v-0
8
Feb
-09
May
-09
Au
g-0
9
No
v-0
9
Feb
-10
May
-10
Au
g-1
0
No
v-1
0
Feb
-11
Co
nce
ntr
ati
on
(m
g/l
)
MRP influent MRP effluent
ICW influent and effluent nutrient concentrations
0
1
10
100
Feb
-08
May
-08
Au
g-0
8
No
v-0
8
Feb
-09
May
-09
Au
g-0
9
No
v-0
9
Feb
-10
May
-10
Au
g-1
0
No
v-1
0
Feb
-11
Co
nce
ntr
ati
on
(m
g/l
)
Ammonia influent Ammonia effluent
16
Results
Results
Nutrient mass loading and removal rates
Variable Loadings (kg/yr) Mass retained
Influent Effluent (%) (kg/yr)
BOD5 8275.8 123.3 98.5 8152.4
NH3-N 1025.5 42.2 92.4 983.4
NO3-N 116.8 9.7 88.4 107.1
PO4-P 110.3 6.5 94.3 103.9
17
Results
Areal first-order kinetic coefficients
for nutrient removal in ICW
Parameter K (m/yr) K20 (m/yr)
θ Mean SD n Mean SD n
BOD5 10.5 6.69 194 9.3 5.96 194 0.982
NH3-N 10.0 7.34 204 13.2 9.11 204 1.025
NO3-N 6.0 4.47 195 5.3 3.97 195 0.979
PO4-P 9.5 8.53 197 12.7 11.04 197 1.026
18
Results
Seasonal variation of nutrient removal
rate and hydraulic loading rate 19
0
5
10
15
0
20
40
60
80
100
Sp
ring
Su
mm
er
Au
tum
n
Win
ter
Sp
ring
Su
mm
er
Au
tum
n
Win
ter
Sp
ring
Sum
mer
Au
tum
n
Win
ter
2008 2009 2010
HL
R (
mm
/d)
Rem
oval
Rate
(%
)
BOD NH3-N NO3-N PO4-P HLRNH3-N NO3-N BOD5 PO4-P
Rem
ov
al
rate
Conclusions
• Removal rates consistently > 90 %.
• Removal rates slightly influenced by seasonality.
• Removal rates influenced by hydrological regime.
• Slightly minimal temperature coefficients indicate
slight temperature dependence.
20
Acknowledgements
• Monaghan County Council, Ireland for funding
the research.
• Dan Doody, Mark Johnston and Eugene Farmer
at Monaghan County Council and Susan Cook at
Waterford County Council for technical support.
21
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Thank you for your attention!
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