Quantitative Chemical Exposure Assessment for Water
Recycling Schemes
Palisade Risk Conference
Sydney, October 20, 2010.
Stuart Khan
UNSW Water Research Centre, School of Civil & Environmental Engineering
University of New South Wales. s.khan@unsw.edu.au
Reduced inflow to Perth dams
52% of
1911-1974
24% of
1911-1974
Sydney’s current water storage
How it looked in 2005
80%
40%
3 years
SE QLD supply projections (from 2007)
Opportunities from water recycling
Major
challenges:
Preserve health of
waterways
Opportunities
from recycling:
Reduction in
effluent discharge
(EPAs, 1980s/90s)
Meet future
demands for water
(This century)
Alternative water
source
Sewage Reuse 2002
5%
11%
6%
10%
15%
3%
9%
11%
7%
2%
2%
10% 0.1%
The National Water Initiative - 2004
Agreement between Commonwealth and (now) all States
Parties agree that the outcome for water reform is to:
i provide healthy, safe, reliable supplies
ii increase water use efficiency in domestic & commercial settings
iii encourage reuse & recycling of wastewater where cost effective
iv facilitate water trading between and within urban & rural sectors
v encourage innovation in water supply sourcing, treatment,
storage and discharge
vi achieve improved pricing for metropolitan water (consistent with
economically efficient and sustainable use of water resources…)
National Water Commission
Water Smart Australia Program
Aim: to accelerate the development and uptake of smart
technologies and practices in water use across Australia
Method: $1.6 billion over five years to 2010
Results: Many large scale schemes affordable
Toowoomba: Indirect Potable Water Recycling?
Reverse osmosis
Reverse osmosis membrane module
UV/H2O2 – Advanced oxidation
QLD Western Corridor Project
Stage 1A: AWT plant at
Bundamba to treat water from
STPs at Bundamba and
Goodna to supply Swanbank
power station
(August 2007).
Stage 1B: Bundamba AWT
plant expanded to incorporate
water from Oxley & Wacol
STPs. Pipeline for off-take to
Tarong power station
(June 2008).
Stage 2: AWT plants
constructed at Luggage Point
and Gibson Island. Delivery to
Wivenhoe Dam
(January 2009).
Perth
• 60% of water from aquifers
• Managed aquifer recharge
(MAR):
 Superficial
 Leederville
• Trial MAR scheme under
construction
• ~27 GL/year by 2015
expected
Beenyup WWTP
Sydney Water “Replacement Flows Project”
Exposure assessment
• Involves the determination of exposure





magnitude,
frequency,
extent,
character,
duration in the past, currently, and in the future.
Exposure assessment – Default values
• Body weight, kg
 Adult male = 70
 Adult female = 58
 Average = 64 (often use 70kg)
• Daily water consumption, mL
 Normal conditions:
•
•
•
•
Adults = 1000–2400, representative figure = 1900 (often use 2000)
Adult male = 1950
Adult female = 1400
Child (10 years) = 1400
 High average temperature (32oC):
• Adults = 2840–3410
 Moderate activity:
• Adults = 3700
Exposure assessment – Probabilistic methods
• Point estimates are most commonly used for exposure
assessments.
 a single value chosen to represent a population e.g. 70kg as the weight
of an adult.
• Point estimates are usually typical values for a population or an
estimate of an upper end of the population’s value
 An upper end value may be chosen for reasons of conservatism and/or
to provide a ‘worse case’ scenario.
• Where a risk assessment uses a series of upper end estimates,
the result can be a worse than ‘worse case’ scenario due to the
compounding conservative assumptions.
• Probabilistic methods provide an alternative to point estimates
Example: Tap water intake (mL/day)
Lognorm2(6.870, 0.530)
X <= 403
5.0%
1
X <= 2303
95.0%
0.9
0.8
Frequency
Values x 10^-3
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
500
1000
1500
2000
2500
Total tap water intake (mL/day)
3000
3500
4000
Probabilistic exposure assessment
Probability density function (PDF)
Removal by Reverse Osmosis
Source Water Concentration
0.350
0.080
0.300
0.070
0.060
Frequency
Frequency
0.250
0.200
0.150
0.050
0.040
0.030
0.100
0.020
0.050
0.010
0.000
0.000
0
10
20
40
30
60
80
100
Percentage Removal
Concentration (ng/L)
Final Ef fluent Concentration
Removal by Advanced Oxidation
9
0.160
7
0.140
6
0.120
Frequency
8
5
4
3
0.100
0.080
0.060
2
0.040
1
0.020
0
0
0.175
0.35
Predicted Concentration (ng/L)
0.525
0.7
0.000
80
85
90
Percentage Removal
95
100
Frequency
F0(C0)
Influent PDF
C0
Concentration
Coagulation/
flocculation/
sedimentation
Frequency
F1(C1|C0)
Combining multiple treatment
barriers
C1
Concentration
F2(C2|C1)
Frequency
Filtration
C2
Concentration
Transformation PDFs
Ozonation
Frequency
F3(C3|C2)
C3
Concentration
Frequency
In-ground storage
F4(C4|C3)
C4
Concentration
To distribution
Frequency
Chloramination
F5(C5|C4)
C5
Concentration
F5(C5)
Product PDF
Haas & Trussell (1998)
Frameworks for assessing reliability of multiple,
independent barriers in potable water reuse.
Water Sci. Technol., 38(6), 1-8.
San Diego AWTP study
(1990s)
Figure
6
Treatment Trains to be Evaluated
North City AWT Options Evaluated
using Monte Carlo Analysis
Conceptually Approved
Treatment Trains
Olivieri, Eisenberg,
Soller, Eisenberg,
Cooper,
Tchobanoglous,
Trussell & Gagliardo
(1999)
Estimation of
pathogen removal in
an advanced water
treatment facility using
Monte Carlo
simulation.
HAC
DHS
Aqua III
Repurification
Project Treatment
Train
Tertiary
Filter
North City WRP Effluent
A
B
C
D
E
F
MF
UF
UF
MF
MF
UF
RO
RO
RO
RO
RO
RO
O3
Cl
O3
O3
Cl
O3
UV
Cartridge
Filter
RO
Air
Stripping
GAC
IX
Cl
Water Sci. Technol.
40(4-5), 223-234.
Cl
Reservoir
Source water quality from historical data
600
Aluminium
N = 54
400
300
10000
Aluminium
200
1000
100
0
1/1/00
1/7/00
1/1/01
1/7/01
1/1/02
1/7/02
1/1/03
Date (2000 - 2004)
Time series
1/7/03
1/1/04
1/7/04
Concentration (g/L)
Concentration (g/L)
500
100
10
LOR = 5 g/L
1
1
2
5
10
20
30
50
70
80
90
95
Percentile
Lognormal probability plot
98 99
Lognormal probability density function
10000
Aluminium
100
Aluminium
9
10
8
LOR = 5 g/L
1
1
2
5
10
20
30
50
70
80
90
Percentile
Lognormal probability plot
95
98 99
Frequency
Values in 10^ -3
Concentration (g/L)
1000
7
6
5
4
3
2
1
0
0
175
350
525
Concentration (ug/L)
Probability density function
700
Chemical Monitoring Strategy for the
Assessment of Advanced Water Treatment
Plant Performance
Sydney Water Replacement Flows Project
• 50 ML/day highly treated water
• To replace Warragamba
releases to Hawkesbury-Nepean
river system
• Three sewage treatment plants:
 Penrith STP
 St Marys STP
 Quakers Hill STP
• New advanced water treatment
plant at St Marys STP
Replacement Flows Pilot Plant
•
•
•
•
•
Approx 0.6 ML/day
St Marys STP
Operated for three months
Chemical risk assessment
Chemical monitoring program
Aims of the monitoring program
• Confirm that key chemicals of potential toxicological concern
are below concentrations that may present a source of human
health concern.
 including pharmaceuticals, endocrine disrupting chemicals, and
emerging disinfection by-products
• Establish and validate a series of indicator chemicals and
surrogate measures (bulk water parameters) that can confirm
proper performance of individual AWTP unit operations.
Samples for Chemical Analysis
Parameters Analysed
No. Samples
5 THMs & DHMs
242
25 PPCPs, 12 Hormones
203
7 Nitrosamines
68
Fluorescence EEM, UV, TOC, Conductivity, pH, Turbidity
272
Challenge: 6 PPCPs, 1 Hormone
54
Challenge: 3 Nitrosamines
54
Nitrosamine Formation Potential: 7 Nitrosamines
10
TOTAL SAMPLES:
903
Assessment of indicator chemicals
3-Stage RO system
Stage 3
RO Feed
Stage 1 Permeate
47%
100%
Stage 1
53%
Stage 1
Concentrate
Stage 2
Stage 2
Concentrate
Stage 2 Permeate
25%
28%
Stage 3 Permeate
12%
16%
Stage 3
Concentrate
Hydranautics ESPA2, 84%,
20 LMH.
84%
Combined
permeate
Sample collection
Tertiary STP
UF
Feed
Tertiary
STP
Effluent
UF Perm
RO
Feed
RO
Perm 1
Combined
Perm
Finished
water
Tertiary STP
Final Effluent
UF Feed
Balance
tank
Ultrafiltration
Balance
P-12
tank
Reverse Osmosis
Stage 1
RO Feed
32 kL/hr
Permeate 1
15 kL/hr
Concentrate 1
17 kL/hr
Ammonium hydroxide
Combined
Permeate
27 kL/hr
Permeate 2
8 kL/hr
Chlorine
Contact
Tank
Final Effluent
27 kL/hr
H2SO4
Reverse Osmosis
Stage 2
Sodium bisulfite
sodium hypochlorite
Antiscalant
RO
Perm 2
Permeate 3
4 kL/hr
Concentrate 2
9 kL/hr
Reverse Osmosis
Stage 3
RO
conc 1
RO
Perm 3
Concentrate 3
5 kL/hr
RO
Conc 2
RO
Conc 3
Trihalomethanes
Bromodichloromethane
100
Concentration (g/L)
1000
Chloroform
AGWR = 200 g/L
AGWR = 6 g/L
10
RO Permeate
1
LOR = 1 g/L
RO Feed
0.1
1
2
5
10
20
30
10
50
70
80
90
95
98 99
Percentile
RO Permeates
1000
Dibromochloromethane
1
AGWR = 100 g/L
100
LOR = 1 g/L
0.1
1
2
5
10
20
30
50
70
80
90
95
98 99
Concentration (g/L)
Concentration (g/L)
100
RO Feed
RO Feed
10
RO Permeate
1
LOR = 1 g/L
Percentile
0.1
1
2
5
10
20
30
50
Percentile
70
80
90
95
98 99
THM removal by reverse osmosis (CHCl3: 25-50%)
Chloroform
51%
61%
Bromodichloromethane
33%
55%
Dibromochloromethane
49%
68%
Bulk parameters (and boundary conditions)
Conductivity
98%
99%
DOC
90%
Peak C Fluorescence
99%
Determining rejection from concentrates
1e+5
Atenolol
(No AGWR)
Concentration (ng/L)
1e+4
Stage 3 RO Concentrate
>99%
1e+3
RO Feed
1e+2
>97% at 5th percentile
1e+1
LOR = 5 ng/L
RO Permeate 1
1e+0
1
2
5
10
20
30
50
70
80
90
95
98 99
Percentile
1e+6
Carbamazepine
AGWR = 100 g/L
1e+5
Concentration (ng/L)
60%
Stage 3 Concentrate
1e+4
1e+3
RO Feed
>98% at 5th percentile
1e+2
LOR = 20 ng/L
1e+1
1
2
5
10
20
30
50
Percentile
70
80
90
95
98 99
77%
Determining rejection from data < LOR
Ibuprofen
1e+6
AGWR = 400 g/L
Concentration (ng/L)
1e+5
87%
1e+4
1e+3
Stage 3 Concentrate
1e+2
RO Feed
1e+1
LOD = 5 ng/L
1e+0
1
2
5
10
20
30
50
70
80
90
95
98 99
Percentile
1e+7
Gemfibrozil
AGWR = 600 g/L
Concentration (ng/L)
1e+6
1e+5
>99%
1e+4
1e+3
centrate
Stage 3 Con
1e+2
RO Feed
1e+1
LOR = 5 ng/L
RO Permeate
1e+0
1
2
5
10
20
30
50
Percentile
70
80
90
95
98 99
Challenge testing
RO
Perm 1
RO
Feed
Combined
Perm
Finished
water
~500 ng/L
RO Feed
32 kL/hr
Balance
tank
Spiked RO Feed
32 kL/hr
Spiking solution
70 L/hr
H2SO4
Reverse Osmosis
Stage 1
Permeate 1
15 kL/hr
Concentrate 1
17 kL/hr
Combined
Permeate
27 kL/hr
Permeate 2
8 kL/hr
Chlorine
Contact
Tank
Reverse Osmosis
Stage 2
Sodium bisulfite
Antiscalant
RO
Perm 2
Permeate 3
4 kL/hr
Concentrate 2
9 kL/hr
Pump
Reverse Osmosis
Stage 3
RO
Conc 1
Final Effluent
27 kL/hr
RO
Perm 3
Concentrate 3
5 kL/hr
Concentrated Spiking Solution
0.25 mg/L
RO
Conc 2
RO
Conc 3
Challenge Testing
Challenge testing indicator chemicals (>90%)
1e+5
Caffiene RO Challenge Test
Ibuprofen RO Challenge Test
10000
1e+4
1e+3
Concentration (ng/L)
Concentration (ng/L)
Stage 3 Concentrate
RO Feed
1e+2
>99%
Stage 3 Concentrate
1000
RO Feed
>98%
100
10
1e+1
LOR = 10 ng/L
LOR = 5 ng/L
1
1e+0
2
5
10
20
30
50
70
80
90
95
98
2
5
10
20
30
Percentile
50
70
80
90
95
98
95
98
Percentile
10000
TCEP RO Challenge Test
Carbamazepine RO Challenge Test
Stage 3 Concentrate
Stage 3 Concentrate
Concentration (ng/L)
Concentration (ng/L)
10000
1000
RO Feed
>97%
100
1000
RO Feed
>94%
100
LOR = 20 ng/L
10
LOR = 20 ng/L
10
1
1
2
5
10
20
30
50
Percentile
70
80
90
95
98 99
2
5
10
20
30
50
Percentile
70
80
90
N-nitrosamines challenge testing (NDMA: 25-50%)
10000
NDMA Challenge Test
Stage 3 Concentrate
RO Feed
Combined RO Permeate
10000
NDPA Challenge Test
100
Stage 3 Concentrate
1000
10
1
5
10
20
30
50
70
80
90
95
Percentile
Concentration (ng/L)
Concentration (ng/L)
1000
RO Feed
100
10
Combined RO Permeate
10000
NDEA Challenge Test
1
Stage 3 Concentrate
5
Concentration (ng/L)
1000
10
20
30
50
Percentile
RO Feed
100
Combined RO Permeate
10
1
5
10
20
30
50
Percentile
70
80
90
95
70
80
90
95
N-Nitrosamines challenge testing (NDMA: 25-50%)
NDMA
26%
35%
NDEA
91%
91%
NDPA
97%
98%
Identified indicator compounds for full scale validation
• Four key chemicals identified and recommended:




Atenolol
Carbamazepine
Chloroform
Dilantin
• Can be monitored at full-scale start-up to confirm plant
performance in line with pilot plant study
• Future application for compliance monitoring
Conclusions
• Probabilistic characterisation of RO treatment
 Valid for defined operating conditions only
 Additional barriers also assessed
• Operational indicators and surrogates
identified
• Validation required for full-scale plant
 Confirm boundary conditions
 Confirm rejection of small number of identified indicators and surrogates
National Water Commission Fellowship
• Waterlines Report No 27
• A ‘how to’ handbook
 Quantitative chemical
exposure assessment for water
recycling
• Available for download:
 http://www.nwc.gov.au/