Optimized Water Sensitive Urban Design:
Trade-offs in
Pollutant Removal Efficiency
Photo: Monash University
Photo:
Sustainable Melbourne
Outline
Water Sensitive Urban Design Technologies; biofilters
- Common in SE Australian urban landscapes
Design Component: Saturation Zone (SZ)
- Nitrogen removal
Are there tradeoffs associated with the implementation of SZ
that affect other pollutants of concern?
Implications of tradeoffs for urban watershed management
- Are there lessons that Southern California can learn
from the Australian experience?
Engineered WSUD Systems: Biofilters
Designed to:
Characterized by:
Strain, sediment, adsorb,
precipitate, lyse, immobilize,
or degrade suites of pollutants
in stormwater or wastewater
- Small Spatial footprint (2.5% CA)
- Vertical flow
- Layered media
- Vegetation
- Soil microbe
and animal communities
inflow
ponding zone
filter media
drainage layer
(gravel, often
supplemented
with organic
carbon such as
woodchips)
transition layers
(sand, gravel)
SZ outflow
standard outflow
Figure modified from Grant et al., 2013
Pollutants of Concern: Biofilters
Nutrients:
- Nitrate, Ammonia
- Phosphate
Indicator Protozoa, Bacteria, and Viruses:
- C. perfringens spores
- E. coli
- F-RNA coliphages
Heavy Metals:
- Lead
- Copper
- Zinc
Suspended Solids
Organic Micropollutants:
- Trihalomethanes: disinfection of drinking water
- PAHs: fossil fuel and coal combustion
- Phthalates: plasticizers
- Glycophosphate: herbicide
- Triazines: resin manufacture & herbicide base
Pollutants of Concern: Biofilters
Nutrients:
- Nitrate, Ammonia
- Phosphate
Indicator Protozoa, Bacteria, and Viruses:
- C. perfringens spores
- E. coli
- F-RNA coliphages
Heavy Metals:
- Lead
- Copper
- Zinc
Suspended Solids
Organic Micropollutants:
- Trihalomethanes: disinfection of drinking water
- PAHs: fossil fuel and coal combustion
- Phthalates: plasticizers
- Glycophosphate: herbicide
- Triazines: resin manufacture & herbicide base
Removal efficiency is constantly high (> 70%)
Removal varies from 90% pollutant capture to net leaching
Pollutants of Concern: Biofilters
Nutrients:
- Nitrate, Ammonia
- Phosphate
Indicator Protozoa, Bacteria, and Viruses:
- C. perfringens spores
- E. coli
- F-RNA coliphages
Heavy Metals:
- Lead
- Copper
- Zinc
Suspended Solids
Organic Micropollutants:
- Trihalomethanes: disinfection of drinking water
- PAHs: fossil fuel and coal combustion
- Phthalates: plasticizers
- Glycophosphate: herbicide
- Triazines: resin manufacture & herbicide base
Removal efficiency is constantly high (> 70%)
Removal varies from 90% pollutant capture to net leaching
Pollutants of Concern: Biofilters
Nutrients:
- Nitrate, Ammonia
- Phosphate
Indicator Protozoa, Bacteria, and Viruses:
- C. perfringens spores
- E. coli
- F-RNA coliphages
Heavy Metals:
- Lead
- Copper
- Zinc
Port Phillip Bay:
Organic Micropollutants:
Concerns regarding
nitrogen
loadingwater
- Trihalomethanes:
disinfection
of drinking
- PAHs: fossil fuel and coal combustion
- Reduce nitrogen inputs
Suspended Solids
- Phthalates: plasticizers
* 100 Tonnes per year
- Glycophosphate: herbicide
* ½ by runoff reduction
Photo: Joe Armao- Triazines: resin manufacture & herbicide base
Removal efficiency is constantly high (> 70%)
Removal varies from 90% pollutant capture to net leaching
Pollutants of Concern: Biofilters
Nutrients:
- Nitrate, Ammonia
- Phosphate
Indicator Protozoa, Bacteria, and Viruses:
- C. perfringens spores
- E. coli
- F-RNA coliphages
Heavy Metals:
- Lead
Organic Micropollutants:
- Copper
- Trihalomethanes:
drinking water
- Can
Zinc biofilters be optimized
to removedisinfection
nitrogenofusing
- PAHs: fossil
fuel and
coal combustion
SZ technology & still effectively
remove
other
pollutants
Suspended Solids
- Phthalates:
plasticizers
of concern like phosphate,
E. coli and
F-RNA coliphages?
- Glycophosphate: herbicide
- Triazines: resin manufacture & herbicide base
Removal efficiency is constantly high (> 70%)
Removal varies from 90% pollutant capture to net leaching
How does a Biofilter Remove Nitrogen?
Total Nitrogen
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
SZ
No SZ
How does a Biofilter Remove Nitrogen?
Total Nitrogen
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
SZ
No SZ
Immobilization: plant uptake (varies by plant species)
How does a Biofilter Remove Nitrogen?
Total Nitrogen
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
Heterotropic
bacteria:
Org-N NH4+
SZ
No SZ
Immobilization: plant uptake (varies by plant species)
Aerobic heterotrophic bacteria: metabolize organic nitrogen compounds
How does a Biofilter Remove Nitrogen?
Total Nitrogen
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
Heterotropic
bacteria:
Org-N NH4+
NH4+
NH4+
SZ
No SZ
Immobilization: plant uptake (varies by plant species)
Aerobic heterotrophic bacteria: metabolize organic nitrogen compounds
Sorption: Ammonium adsorbs to negatively charged soil particles and SOM
How does a Biofilter Remove Nitrogen?
Total Nitrogen
N2O
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
Heterotropic
bacteria:
Org-N NH4+
NH4+
NH4+
Nitrifying
bacteria:
NH4+ NO2NO2- NO32-
SZ
No SZ
Immobilization: plant uptake (varies by plant species)
Aerobic heterotrophic bacteria: metabolize organic nitrogen compounds
Sorption: Ammonium adsorbs to negatively charged soil particles and SOM
Nitrification: microbial mediated aerobic oxidation of ammonia
How does a Biofilter Remove Nitrogen?
Total Nitrogen
N2O
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
Heterotropic
bacteria:
Org-N NH4+
NH4+
NH4+
Nitrifying
bacteria:
NH4+ NO2NO2- NO32-
How do we keep labile nitrate from leaching?
SZ
No SZ
Immobilization: plant uptake (varies by plant species)
Aerobic heterotrophic bacteria: metabolize organic nitrogen compounds
Sorption: Ammonium adsorbs to negatively charged soil particles and SOM
Nitrification: microbial mediated aerobic oxidation of ammonia
How does a Biofilter Remove Nitrogen?
Total Nitrogen
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
rce
u
o
C-s
Heterotropic
bacteria:
Org-N NH4+
NH4+
NH4+
Build a Saturation Zone
Nitrifying
bacteria:
NH4+ NO2NO2- NO32C-source
SZ
No SZ
Saturation Zone:
- Elevate outflow to increase moisture / decrease aeration
(promotes an O2 gradient)
- Add a carbon source to the biofilter bed to serve as an electron donor
How does a Biofilter Remove Nitrogen?
NO
2
Total Nitrogen
N2O
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
decomposed
rce
u
o
C-s
Heterotropic
bacteria:
Org-N NH4+
Denitrifying bacteria: NO32-
NH4+
NH4+
N2
Nitrifying
bacteria:
NH4+ NO2NO2- NO32C-source
SZ
No SZ
Saturation Zone:
Denitrification:
anaerobic
heterotrophy
that reduces
nitrate to N2 gas
- Elevate
outflow microbial
to increase
moisture / decrease
aeration
(promotes an O2 gradient)
With SZ TN- Add
TP a carbon
E. coli Coliphages
source to the biofilter bed to serve as an electron donor
Outflow
Conc.
N
How does a Biofilter Remove Nitrogen?
NO
2
Total Nitrogen
N2O
immobilized
aerobic
aerobic
(no SZ)
or
anerobic
(SZ)
>70%
But What About Other
Pollutants?
decomposed
rce
u
o
C-s
Heterotropic
bacteria:
Org-N NH4+
Denitrifying bacteria: NO32-
NH4+
NH4+
N2
Nitrifying
bacteria:
NH4+ NO2NO2- NO32-
C-source
SZ
No SZ
Saturation Zone:
Denitrification:
anaerobic
heterotrophy
that reduces
nitrate to N2 gas
- Elevate
outflow microbial
to increase
moisture / decrease
aeration
(promotes an O2 gradient)
With SZ TN- Add
TP a carbon
E. coli Coliphages
source to the biofilter bed to serve as an electron donor
Outflow
Conc.
N
How does a SZ affect removal of Total Phosphorous?
Total Phosphorous
aerobic
aerobic
or
anerobic
(SZ)
With SZ TN
Outflow
Conc.
SZ
No SZ
TP
E. coli
Coliphages
How does a SZ affect removal of Total Phosphorous?
Total Phosphorous
immobilized
aerobic
decomposed
Heterotropic
bacteria:
Org-P H2PO4-
aerobic
or
anerobic
(SZ)
SZ
No SZ
Immobilization
With SZ TN
Outflow
Conc.
TP
E. coli
Aerobic heterotrophic bacteria
Coliphages
How does a SZ affect removal of Total Phosphorous?
Total Phosphorous
immobilized
aerobic
decomposed
Heterotropic
bacteria:
Org-P H2PO4-
OPO3H-
Al+
Al+
OPO3H-
OPO3HFe(OH)3
OPO3H-
aerobic
or
anerobic
(SZ)
SZ
No SZ
Immobilization
With SZ TN
Outflow
Conc.
TP
E. coli
Aerobic heterotrophic bacteria
Coliphages
Adsorption
- Clays
- Ferric Oxides
How does a SZ affect removal of Total Phosphorous?
Total Phosphorous
immobilized
aerobic
decomposed
aerobic
or
anerobic
(SZ)
Al+
Al+
OPO3H-
OPO3HFe(OH)3
OPO3H-
Phosphorus is Efficiently Removed
SZ
No SZ
Immobilization
With SZ TN
Outflow
Conc.
Heterotropic
bacteria:
Org-P H2PO4-
OPO3H-
TP
E. coli
Aerobic heterotrophic bacteria
Coliphages
Adsorption
- Clays
- Ferric Oxides
Anaerobic, high carbon SZ does not favor TP adsorption
Total Phosphorous
immobilized
aerobic
aerobic
or
anerobic
(SZ)
Heterotropic
bacteria:
Org-P H2PO4-
decomposed
C-source
C-source
Al+ 2H2PO4Al+
Desorption: C-source competes with
phosphorous for binding site
With SZ TN
Outflow
Conc.
TP
E. coli
Coliphages
OPO3H-
Al+
Al+
OPO3H-
OPO3HFe(OH)3
OPO3H-
SZ
Anaerobic, high carbon SZ does not favor TP adsorption
Total Phosphorous
immobilized
aerobic
aerobic
or
anerobic
(SZ)
Heterotropic
bacteria:
Org-P H2PO4-
decomposed
C-source
C-source
Al+ 2H2PO4Al+
Outflow
Conc.
TP
E. coli
Coliphages
Al+
Al+
OPO3H-
OPO3HFe(OH)3
OPO3H-
Iron reducing bacteria:
Fe(OH)3-PO43- Fe2+ + H2PO4-
Desorption: C-source competes with
phosphorous for binding site
With SZ TN
OPO3H-
Dissimilatory iron reduction:
anaerobic microbial heterotrophy
that reduces ferric to ferrous iron
SZ
Anaerobic, high carbon SZ does not favor TP adsorption
Total Phosphorous
immobilized
aerobic
aerobic
or
anerobic
(SZ)
Heterotropic
bacteria:
Org-P H2PO4-
decomposed
C-source
C-source
Al+ 2H2PO4Al+
Outflow
Conc.
TP
E. coli
Coliphages
Al+
Al+
OPO3H-
OPO3HFe(OH)3
OPO3H-
Iron reducing bacteria:
Fe(OH)3-PO43- Fe2+ + H2PO4-
Desorption: C-source competes with
phosphorous for binding site
With SZ TN
OPO3H-
SZ
Dissimilatory iron reduction:
anaerobic microbial heterotrophy
that reduces ferric to ferrous iron
TRADE-OFF: Phosphorus conc. in the
outflow are enhanced when nitrogen
removal is favored
Management Implications:
Eutrophication & Nutrient Limitation
Different nutrients are limiting in marine vs fresh receiving waters
Freshwater systems: P limited
Coastal marine systems: N limited
Photo: Independent Magazine
Algal Blooms
Hypoxia
Native Ecosystem Collapse
Photo: Joe Armao
Darling Barwin River, AU
Port Phillip Bay, AU
Biofilters with a Saturation Zone may improve water quality in systems with
coastal receiving waters
Biofilters with Saturation Zones may be inappropriate for systems with high
phosphorus loading and/or fresh receiving waters
Management Implications:
Eutrophication & Nutrient Limitation
Different nutrients are limiting in marine vs fresh receiving waters
Freshwater systems: P limited
Coastal marine systems: N limited
Photo: Independent Magazine
Tailor biofilter design to
receiving water type
Photo: Joe Armao
Darling Barwin River, AU
Port Phillip Bay, AU
Biofilters with a Saturation Zone may improve water quality in systems with
coastal receiving waters
Biofilters without Saturation Zones may improve water quality in systems with
fresh receiving waters
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
aerobic
aerobic
or
anerobic
(SZ)
With SZ TN
Outflow
Conc.
SZ
No SZ
TP
E. coli
Coliphages
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
aerobic
aerobic
or
anerobic
(SZ)
SZ
No SZ
With SZ TN
Outflow
Conc.
Solar Radiation
Solar Radiation
TP
E. coli
Coliphages
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
aerobic
aerobic
or
anerobic
(SZ)
SZ
No SZ
Solar Radiation
Predation (bactiverous protists)
With SZ TN
Outflow
Conc.
TP
E. coli
Coliphages
Solar Radiation
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
aerobic
or
anerobic
(SZ)
Y
aerobic
SZ
No SZ
Solar Radiation
Predation (bactiverous protists)
Straining (bacterial attenuation)
With SZ TN
Outflow
Conc.
Y
Y
Y
TP
E. coli
Coliphages
Solar Radiation
Adsorption:
- microbial aggregations
- kaolinite clays and clay-loams
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
Y
aerobic
aerobic
or
anerobic
(SZ)
rc e
u
o
C-s
SZ
Predation: increased protist survival
Straining: reduced macropore
formation in dry periods
With SZ TN
Outflow
Conc.
TP
E. coli
Y
Y
Y
Coliphages
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
Y
Y
Y
Y
aerobic
rc e
u
o
C-s
Predation: increased protist survival
Straining: reduced macropore
formation in dry periods
With SZ TN
Outflow
Conc.
TP
E. coli
Coliphages
Y
Y
Y
C-s
rce
u
o
Desorption:
C-source
Y
aerobic
or
anerobic
(SZ)
SZ
Y
- virus particles desorb from microbial
aggregates
- C-source competes with virus for
attachment sites
How does a SZ affect removal of Fecal Bacteria & Viruses?
Escherichia coli
F-RNA Coliphage
Y
Y
Y
Y
rc e
u
o
C-s
Y
Y
Y
C-s
rce
u
o
C-source
Y
aerobic
or
anerobic
(SZ)
Y
aerobic
SZ
Y
TRADE-OFF: Outflow virus loads (like phosphorus) are
enhanced when FIB (and nitrogen) removal is favored
With SZ TN
Outflow
Conc.
TP
E. coli
Coliphages
Contaminants with adsorption as a
dominant removal mechanism are
removed less efficiently in biofilters
with a SZ design
Management Implications?
How do we weigh the importance of bacterial vs viral removal in biofilters?
Relative Abundance in Stormwater Runoff or Specific Health Risk?
Viruses:
- Adenovirus
Bacteria:
- Campylobacter
(84% of samples)
(100% of samples)
- Salmonella
(66% of samples)
Photo:
V. Brinkmann
- Polyomavirus
Photo:
L. Stannard
(50% of samples)
Salmonella
Adenovirus
Err on the Side of Caution
If a catchment has probable sewer inputs (from septic systems), a biofilter
with a Saturation Zone is not recommended
Otherwise, biofilter design should reflect receiving water type
- SZ for coastal systems
- No SZ for freshwater systems
Management Implications?
How do we weigh the importance of bacterial vs viral removal in biofilters?
Relative Abundance in Stormwater Runoff or Specific Health Risk?
Viruses:
- Adenovirus
Bacteria:
- Campylobacter
(84% of samples)
(100% of samples)
- Salmonella
(66% of samples)
Photo:
V. Brinkmann
- Polyomavirus
Photo:
L. Stannard
(50% of samples)
Salmonella
Adenovirus
Err on the Side of Caution
If a catchment has probable sewer inputs (from septic systems), a biofilter
with a Saturation Zone is not recommended
Otherwise, biofilter design should reflect receiving water type
- SZ for coastal systems
- No SZ for freshwater systems
Management Implications: health risk?
McBride et al,in press
Adenovirus
Photo:
L. Stannard
Bacteria:
- Campylobacter
(22/22 samples)
- Salmonella
(7/22 samples)
Viruses can have
higher infectivity
at lower doses
Salmonella
Photo:
V. Brinkmann
Err on the Side of Caution
If a catchment has probable sewer inputs (from septic systems), a biofilter
with a Saturation Zone is not recommended
Otherwise, biofilter design should reflect receiving water type
- SZ for coastal systems
- No SZ for freshwater systems
Summary and Conclusions
Low energy technologies like biofilters can be designed to remove
specific pollutants of concern like nitrogen
Trade-offs in removal efficiency exist and are linked to specific
design features
- SZ favors N & FIB removal but increases outflow loads of P & viruses
- This tradeoff may be due to the dominant removal mechanism
(biological or physical straining vs adsorption)
- Adsorptive processes are not favored in the SZ redox environment
These trade-offs can guide US biofilter implementation
- No SZ where septic inputs are suspect
- Receiving water type can guide design: marine – SZ; fresh – No SZ
Questions?
OPO3HFe(OH)3
OPO3H-