January 2014
Slow Sand Filtration (Biofilm reactors):
a solution to remove micro-pollutants
in small WWTP’s effluents?
Mònica Escolà Casas, Kai Bester
Department of Environmental Science, Aarhus University, Roskilde, Denmark
1
moes@dmu.dk
kb@dmu.dk
Disposition
› Background
› Objectives
› The Set-up and Results
› Discussion and Conclusion
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Background: The Problem
XENOBIOTICS
CONVENTIONAL
WATER TREATMENT
MICROPOLLUTANTS
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Background: Possible Solutions
› Activated carbon and Reverse Osmosis
TRAB act. carbon
› Advanced Oxidation Processes
Bouillides WTP
› Biological Processes
Rielli.com
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Background: Biofilm Reactors
› Biofilm Reactors = porous media + biofilm
(Biofilters)
(Sand)
› Affordable, robust and suitable for small WWTP’s
› Constructed soil biofilters eliminate micro-pollutants from
wastewater effluents.
› Effectiveness: hydraulic residence-time, compounds residence time
and biological activity.
› Mechanisms and most efficient biofilm reactor configuration?
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Disposition
› Background
› Objectives
› The Set-up and Results
› Conclusion
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Objective: Efficiency
XENOBIOTICS
CONVENTIONAL
WATER TREATMENT
MICROPOLLUTANTS
BIOFILM
REACTOR
(Filter media
and biofilms)
SORPTION
+
DEGRADATION
Sorption or degradation?
Transport?
Aerobic or anaerobic?
%?
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Aim: Understanding mechanisms
What is happening in the reactor?
› Adsorption or degradation?
› Observed removal in soil = adsorption + degradation
› Observed removal in sand ≈ degradation
› Transport?
› Observed transport in soil = adsorption + porosity
› Observed transport in sand ≈ porosity
› Sand particles  known size and even distribution
Quartz-sand
biofilm reactor
› Aerobic or anaerobic?
› Aerobic degradation >> Anaerobic degradation
› Sand-based biofilm reactor operated aerobically
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Disposition
› Background
› Objectives
› The Set-up and Results
› Conclusion
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
The Set Up: Which compounds?
Pharmaceuticals
Diclofenac and propranolol
Detected in WWTP’s effluents (ng L-1 )
Diclofenac
Fungicides
Propiconazole and tebuconazole.
Detected in WWTP’s effluents (ng L-1 )
Tebuconazole
X-ray contrast media
Iopromid, iohexol and iomeprol
Detected in WWTP’s effluents (µg L-1 )
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
Iohexol
January 2014
The Set-up: Biofilm reactor
TRANSPORT
Ø = 5 cm2
On-Line
measurements
29 cm
REMOVAL
Tank
”WWTP”
Effluent
Tank
”clean”
+ Oxygen consumption
+ TOC
Off-line
measurements
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Transport: Results
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
The Set Up: Biofilm reactor
TRANSPORT
Ø = 5 cm2
Off-line
measurements
29 cm
REMOVAL
Tank
”WWTP”
Effluent
Tank
”clean”
+ Oxygen consumption
+ TOC
Off-line
measurements
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Removal: Oxygen and TOC
Oxygen (mg / L)
10
9
8
7
6
5
4
3
2
1
0
TOC (mg C / L)
12
27%
10
8
6
60%
0%
27%
4
2
0
25 µl/min
200 µl/min
Inlet
Outlet
25 µl/min
200 µl/min
Inlet
Outlet
Oxygen consumption and TOC removal for min. and max. flows
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Removal: Method
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
15
Removal: kinetics (k’s)
Agrees with O2 and TOC…
-5
-5
Diclofenac
y = -0.0401x
R² = 0.93
-3
-3
-1
y = -0.1431x
R² = 0.37
-1
0
-5
10
20
30
40
0
50
-5
Iopromid
y = -0.0462x
R² = 0.81
-3
10
Iohexol
-3
20
30
40
50
-5
Iomeprol
y = -0.1012x
R² = 0.83
-3
0
10
20
30
40
0
50
-2
-2
-1
0
0
0
10
20
30
40
50
10
20
30
40
50
30
40
50
0
10
20
30
40
50
Propiconazole
Tebuconazole
-1
y = -0.0899x
R² = 0.68
-1
-1
-1
ln(Coutlet/Cinlet)
Propranolol
0
10
20
Hydraulic Residence Time (h)
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Disposition
› Background
› Objectives
› The Set-up and Results
› Discussion and Conclusion
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Similar studies
Parameter
Present study
Reungoat et al.
(2011)
Scheytt et al.
(2006)
Matamoros
(2007)
Water type
Real wastewater
effluent
Real wastewater
effluent
Syntetic
wastewater
Raw wastewater
Hydraulic loading
rate
[m3 m-2 h-1]
0.01176
6
0.00917
0.0029
Filter
(particle size
[mm])
Quartz sand
(0.21-0.29)
Sand
(2.25)
Sandy sediment
(0.063-0.630)
(foc=0.13%)
Coarse gravel (8-16)
Gravel(0-4)
Initial TOC/DOC
[mg C L-1]
4.86 and 7.58
11.2 ± 0.4 (DOC)
Not tested
Not tested
HRT [h]
9.01
2
0.108
(unsaturated)
342
Diclofenac
Removal (%)
41.7 ± 2
20 ± 10 (graph)
35
39 ± 22
Diclofenac
Degr. Rate [h-1]
0.040
(kA=0.0041 m/h*)
Not tested
0.37
kA=0.004 m/h*
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Similar studies
Parameter
Present study
Reungoat et al.
(2011)
Scheytt et al.
(2006)
Matamoros
(2007)
Water type
Real wastewater
effluent
Real wastewater
effluent
Syntetic
wastewater
Raw wastewater
Hydraulic loading
rate
[m3 m-2 h-1]
0.01176
6
0.00917
0.0029
Filter
(particle size
[mm])
Quartz sand
(0.21-0.29)
Sand
(2.25)
Sandy sediment
(0.063-0.630)
(foc=0.13%)
Coarse gravel (8-16)
Gravel(0-4)
Initial TOC/DOC
[mg C L-1]
4.86 and 7.58
11.2 ± 0.4 (DOC)
Not tested
Not tested
HRT [h]
9.01
2
0.108
(unsaturated)
342
Diclofenac
Removal (%)
41.7 ± 2
20 ± 10 (graph)
35
39 ± 22
Diclofenac
Degr. Rate [h-1]
0.040
(kA=0.0041 m/h*)
Not tested
0.37
kA=0.004 m/h*
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Similar studies
Parameter
Present study
Reungoat et al.
(2011)
Scheytt et al.
(2006)
Matamoros
(2007)
Water type
Real wastewater
effluent
Real wastewater
effluent
Syntetic
wastewater
Raw wastewater
Hydraulic loading
rate
[m3 m-2 h-1]
0.01176
6
0.00917
0.0029
Filter
(particle size
[mm])
Quartz sand
(0.21-0.29)
Sand
(2.25)
Sandy sediment
(0.063-0.630)
(foc=0.13%)
Coarse gravel (8-16)
Gravel(0-4)
Initial TOC/DOC
[mg C L-1]
4.86 and 7.58
11.2 ± 0.4 (DOC)
Not tested
Not tested
HRT [h]
9.01
2
0.108
(unsaturated)
342
Diclofenac
Removal (%)
41.7 ± 2
20 ± 10 (graph)
35
39 ± 22
Diclofenac
Degr. Rate kA
kA=0.0041 m/h
Not tested
nd
kA=0.004 m/h
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Comparing data
Target compound
Propranolol
k
[h-1]
0.143
%
Removal
at 98
µl/min
94±2
Other studies
Incubated sludge
K: 0.096 h-1-0.113 h-1
(S- and R-enantiomers)
Ribeiro et al. 2013
Diclofenac
0.040
41±2
Propiconazole
Tebuconazole
-
17±3
58±4
Iohexol
0.101
57±3
% Removal sand filters
39-35
(Matamoros et al. 2007
Scheytt et al. 2006)
No previous data
No previous data
% Removal MBBR
79
Sand reactor,
getting started
(Hapeshi et al.2013)
Iomeprol
0.090
85±0.2
Iopromide
0.046
58±0.3
No previous data
% Removal sand filter - drinking water
13
(Zearley and Summers 2012)
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Conclusions
› Sand biofilm reactors are easy to control due to hydraulics
and minimized sorption processes
› Micro-pollutants (some considered reclacitrant) can be
eliminated by the sand biofilm reactor
› Operation over 10 months without signs of clogging
› Low flows (1000 m 3 h -1 )  filter-area of 85.000 m2
› Biofilter thickness can be increased (meaning less filterarea)
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Acknowdledgements
› AUFF grant: Advanced water purification using bio-inorganic
nanocatalysts and soil filters.
› The personnel of WWTP Bjergmarken that was always
extremely helpful considering provisions of samples and data
on their WWTP.
› Aasbjørn Haaning Nielsen and Jes Vollertsen of Aalborg
University helped with setting up the oxygen sensing.
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
Thanks for your attention
LITERATURE
› Hapeshi, E., Lambrianides, A., Koutsoftas, P., Kastanos, E., Michael, C. and Fatta-Kassinos, D. (2013)
Investigating the fate of iodinated X-ray contrast media iohexol and diatrizoate during microbial
degradation in an MBBR system treating urban wastewater. Environ Sci Pollut Res Int.
› Kadlec, R.H. and Knight, R.L. (1996) Treatment Wetlands, Lewis Publishers, Boca Raton, New York, London,
Tokyo.
› Matamoros, V., Arias, C., Brix, H. and Bayona, J.M. (2007) Removal of Pharmaceuticals and Personal Care
Products (PPCPs) from Urban Wastewater in a Pilot Vertical Flow Constructed Wetland and a Sand Filter.
Environmental Science & Technology 41(23), 8171-8177.
› Reungoat, J., Escher, B.I., Macova, M. and Keller, J. (2011) Biofiltration of wastewater treatment plant
effluent: Effective removal of pharmaceuticals and personal care products and reduction of toxicity. Water
Research 45(9), 2751-2762.
› Ribeiro, A.R., Afonso, C.M., Castro, P.M.L. and Tiritan, M.E. (2013) Enantioselective biodegradation of
pharmaceuticals, alprenolol and propranolol, by an activated sludge inoculum. Ecotoxicology and
Environmental Safety 87(0), 108-114.
› Scheytt, T.J., Mersmann, P. and Heberer, T. (2006) Mobility of pharmaceuticals carbamazepine, diclofenac,
ibuprofen, and propyphenazone in miscible-displacement experiments. Journal of Contaminant
Hydrology 83(1–2), 53-69.
› Zearley, T.L. and Summers, R.S. (2012) Removal of Trace Organic Micropollutants by Drinking Water
Biological Filters. Environmental Science & Technology 46(17), 9412-9419.
Sand Biofilm Reactors: a solution to remove micro-pollutants in small WWTP’s effluents?
Mònica Escolà Casas
January 2014
January 2014
Slow Sand Filtration (Biofilm reactors):
a solution to remove micro-pollutants
in small WWTP’s effluents?
Mònica Escolà Casas, Kai Bester
Department of Environmental Science, Aarhus University, Roskilde, Denmark
25
moes@dmu.dk
kb@dmu.dk