Wastewater treatment and
water recycling
Managing risks associated with irrigating
recycled water
Dr Daryl Stevens
• Managing Director and Principal Scientist
Dr Mirela Magyar - Atura
Dr Nick O’Connor – Ecos Environmental Consulting
daryl@atura.com.au
www.atura.com.au
www.recycledwater.com.au
Mobile: 0418 802 621
Ph:+61 3 9602 4001
6/5/2012
Strategic approach to water
supply
 1900s
– Traditional systems - build dams
– Dispose of sewage
 2000s
– Integrated water management
– Diversify water sources
• Rainfall (Catchments and tanks)
• Desalination – salt reduction
• Recycle
• Pipe
• Ground water
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1
Water management
Sources
 Desalination (Seawater)
 Rainfall (ground water, dams and

tanks)
Recycling (direct, indirect, drinkable)
What do Astronauts do?
Source management
 Demand management
 Interconnection between sources
 Water trading
 Storage and recovery
 Increasing efficiencies
Department of
Water Resources,
SA
6/5/2012
Australian water reuse
 Major water recyclers
– Agriculture
– Other Industries
– Water supply
 Total Reuse is
– 15% of Urban Water
– 5% of Agricultural
water
2
What makes up sewage?
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Water
Inorganic chemicals
Organic chemicals
Pathogens
Microbes
Organic matter
Minerals
Suspended materials
Physical properties (e.g. temperature)
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Raw sewage pathogens
Typically
 Viruses
– e.g. Rotavirus: 8,000/L (actually
Adenoviruses!)
 Protozoa or parasites
– e.g. Cryptosporidium: 2,000/L (may
not be viable!)
 Bacteria
– e.g. Campylobacter: 7,000/L
(actually, UK data!)
– e.g.
 Helminthes (1-1000/L)
– e.g. Taenia, Ascaris
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3
Key environmental
hazards
Key environmental hazards
Additional hazards associated
with use for environmental
allocation
•Boron
•Cadmium
•Chloride
•Chlorine disinfection residuals
•Hydraulic loading (water)
•Nitrogen
•Phosphorus
•Salinity
•Sodium
•Ammonium
•Aluminium
•Arsenic
•Copper
•Lead
•Mercury
•Nickel
•Zinc
•Phenol
•Surfactants
ie Linear alkylbenzene sulfonates
(LAS) and alcohol ethoxylated
surfactants (AE)
Hazards – Physical/chemical
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General – pH, BOD, Temp, Hydraulic load
Nutrient – B, N, P, K, Na, S, Cal, Fe, Zn, etc
Metals/metaloids/halides – Hg, Pb, F, Zn, CN, etc.
Surfactants – AES, LAS and SAS
Organic compounds
Pesticides and their metabolites
Disinfection by-products
Radionuclides
Pharmaceuticals
Algal toxins
Estrogenic and androgenic hormones
Antiseptics
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Overview of what is in sewage
EPA Ireland (2007) Waste Water Treatment Manuals. Primary, Secondary
and Tertiary Treatment. Ardavan, Wexford, Ireland: Environmental Protection
Agency
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Sewage treatment basics
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Typical Activated Sludge
Treatment Plant
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Typical Physical-Chemical
Treatment Plant
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Sludge Treatment
 Includes processes:

– Concentration (dewatering, mass reduction),
– Stabilization,
– Disposal/Benefical use
Sludge produced during the primary, secondary
and tertiary treatments.
Treatment levels
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WWTP: a critical control point
Cunningham VL (2008) Environmental Exposure Modeling: Application of PhATETM and Great-ER to Human Pharmaceuticals in the
Environment In K. Kümmerer, ed. Pharmaceuticals in the Environment Berlin, Heidelberg: Springer Berlin Heidelberg, p. 133–146
6/5/2012
Overview of STP processes
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Overview of biosolids treatment
6/5/2012
Basic principles of AGWR
 Aim is to ensure (as much as possible) that recycled
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water is safe before use
A coordinated approach from source to point of
use
Reduces reliance on recycled water testing (too
little, too late)
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Hydrological cycle
Key:
Phase 1
Phase 2
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Sewer mining  Municipal use
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STP and Soil Models
6/5/2012
Modelling degradation
through the STP to assess risk
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Source
Sewers
Sewage
treatment
Environmental
compartments
Receptor
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Variables: Phyico-chem
 BTF estimates (measured/predicted) = BCF M:P
 Biodegradation rates (measured/predicted) =
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Biodegrade M:P
Variation in toxicity impact on population
Variation in Henry’s law constant (log10
measured/predicted) = Log HLC M:P
Variation in Log Koc = LogKocP-+M
Variation in Log Kow = LogKowP-+M as defined by EPI
Suite (USEPA, 2011b)
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Variables: Soil
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Irrigation rate = IR
Depth of irrigation water = Depth Irrigated PDF
Soil bulk density PDF = SoilBD
Leaching rates = Leach
Root density = Den_roots
Fraction of organic carbon in soil = FOC
Mass fraction of organic carbon = FOCM
6/5/2012
Input variable
STP
 Typical influent to process step (ML/D)
 VSS Sludge Conc (g/m3)
 TSS Sludge Conc (g/m3)
Receptor
 Yield
 Weight (Child/Adult)
 Bodyfat
 Pasture intake
 Stockwater source and volumes consumed
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180
160
140
120
100
80
60
40
20
0
Frequency
PDF of child/adult weight
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PDF of water ingested
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PDF of soil ingested
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Irrigation requirements
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Preventive measures
 Exclusion barrier
– Effective design of WTP
– Decrease
concentration
– Hazard source control
– Storage design
– System maintenance
– Water Treatment
 End-use Restrictions
–
–
–
–
–
–
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Buffer distances/strips
Crop/plants grown
Hydraulic load
Irrigation tools
Light reduction
Nutrient balancing
Shandy with fresh
water
– Site selection
– Soil ameliorant
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Risk Management Systems
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HACCP - Food & beverage safety & quality
HAZOP - Plant operation
CHAIR - Plant layout/operability, safety
AZ/NZS 4360 - Risk management
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Benefits of Risk Assessment
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Hazards: SRA
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General – pH, BOD, Temp, Hydraulic load
Nutrient – B, N, P, K, Na, S, Cal, Fe, Zn, etc
Metals/metaloids/halides – Hg, Pb, F, Zn, CN, etc.
Surfactants – AES, LAS and SAS
Organic compounds
Pesticides and their metabolites
Disinfection by-products
Radionuclides
Pharmaceuticals
Algal toxins
Estrogenic and androgenic hormones
Antiseptics
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Hazard control & preventive measure
Within
target criteria
and critical limit
Hazard controlled by
• Preventive
Preventive
measures
measures
• Critical control
Exclusion barrier
(prevents entry or
removes hazard )
points
• Target criteria
• Critical limits
Within
target
criteria
End-use restriction
barrier
(controls exposure)
Critical
limit
exceeded
Monitoring
program
Control lost
Unacceptable health
or environmental risk
Deviation from
target criteria
Take corrective action
immediately
Losing control
Within
target
criteria
Critical Control Point
Take corrective
action
Critical
limit
exceeded
Inform health or
environment regulator?
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Hazard quotient
PEC
PNEC
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HQ MRL Plants
6/5/2012
Sensitivity
analysis:
MRL Plant
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Sensitivity
analysis:
MRL Beef
Includes
Stockwater
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Sensitivity analysis:
MRL Beef
No recycled water as Stockwater
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Milk MRLs sensitivity to Soil?
6/5/2012
Modelling system sensitivities
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Modelling system sensitivities
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Irrigation of plants
g
0.79
0.8
5.0%
/
y
4.12
90.0%
5.0%
0.7
Irrigation water /
Hexythiazox
0.5
Minimum
Maximum
Mean
Median
Std Dev
10%
90%
Values
0.4
0.3
0.790
13.309
1.807
1.480
1.141
0.794
3.088
500
0.2
0.1
14
12
10
8
6
4
2
0.0
0
Frequency
0.6
Variable
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300
250
200
150
100
Frequency
50
Values x 10^4
Plant toxicity
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Modelling sensitivities
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Half-lives in chemicals potentially in
recycled water
6/5/2012
Management Strategies?
Enduse
 Volume of soil and recycled water ingested by
cattle
 Irrigation rates and total loads
 Soil depth of incorporation
Restriction barrier
 Source control and tradewaste management
crucial
 Sewage treatment plant flow rate
 Raw suspended solids entering STP
 Total organic carbon load to STP
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Thank you!
www.atura.com.au
daryl@atura.com.au
6/5/2012
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