Drinking Water Through Recycling
The benefits and costs of supplying
direct to the distribution system
Dr Stuart Khan
School of Civil & Environmental Engineering,
University of New South Wales
Project aim
“To define in objective scientific, economic and
social terms, the potential place of recycling
directly to the drinking water distribution
system, in the spectrum of available water
supply options”
Target audience
“The report will be directed towards policy
makers, regulators, researchers, the water
industry at large and the consuming public”
Indirect potable reuse
Water treatment
plant
Indirect potable reuse
Water treatment
plant
Role of the ‘environmental buffer’
• Opinions of 80 Australian stakeholders:
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To provide an additional treatment barrier for pathogenic and/or trace chemical substances
To provide dilution of contaminants in recycled water
To stabilise/equilibrate highly purified reverse osmosis permeates
To provide ‘time to respond’ to treatment malfunctions or unacceptable water quality
Buffering the production and use of recycled water / storage
Maintenance of aquifer integrity and/or groundwater quality
– To provide a ‘perception’ of increased water quality or
safety / public confidence
– To provide a perception of a disconnection between
treated effluent and raw drinking water / To reduce the
“yuck factor”
Goreangab Water Reclamation Plant,
Windhoek, Namibia
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Pioneer DPR Project (since 1968)
Goreangab WTP converted to not only treat water from Goreangab Dam, but also
reclaimed effluent
New plant completed in 2002 (NGWRP)
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Capacity: 7.5 GL/year (~20 ML/day)
Provides 35% of total supply
Can do 50% in severe drought conditions
Cloudcroft, New Mexico, USA
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Small, high altitude skiing village
Permanent population <1000, but more than doubles on weekends and holidays
Potable water from springs and wells, but during drought has been tankered in on weekends
DPR system began operation in 2011
Operating license requires slightly greater fraction (51%) of surface or groundwater to be used.
DPR capacity: 0.1 ML/day
Big Spring, West Texas, USA
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Permian Basin city of around 30,000 population
Severe drought during much of last 15 years
Surface water (from Colorado River) and available groundwater insufficient for future needs
IPR considered but:
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Current raw water sources are distant and lower in elevation
High evaporative losses
High dissolved solids in current surface water (and in available effluent sources)
DPR began operation April 2013. Capacity: 10 ML/day
Contributes up to 15% of blended raw water in the pipeline
Treatment energy costs offset by energy savings from avoided raw water and effluent pumping
Beaufort West Municipality, South Africa
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Situated in Central Karoo, one of the driest areas in South Africa
Population: ~40,000 (spread across three towns)
Severe drought in 2010/2011 led to daily water trucking to >8000 homes
Increased water demand forecast in coming years
DPR plant commissioned in January 2011
Design capacity: 2 ML/day
Contributes 20% of blended raw water in the pipeline (will increase to 25%)
Health risk assessment and risk management
• Broad range of harmful substances in untreated sewage
– Pathogens (viruses, bacteria, protozoa)
– Chemicals (carcinogenic, endocrine disrupting, other toxicities)
• Objectives
– Reduce concentrations to levels of acceptable risk (treatment)
– Ensure that the above is achieved (monitoring)
– Engineer system reliability
• Hazard Analysis and Critical Control Points (HACCP)
• Multiple-barrier approach
• Probabilistic reliability analysis
– Foster operator reliability
• High levels of expertise and training within the Australian water industry
• Supported by mechanisms to ensure compliance with requirements to
only use appropriately skilled operators and managers
Cost, energy and GHG emissions
• Illustrative hypothetical case study
– Undertaken by GHD
Four scenarios based on alternative water supply
options for a hypothetical coastal Australian city:
• Seawater desalination
• Indirect potable reuse
• Direct potable reuse
• Dual-pipe systems
Model (including uncertainty):
• Financial (capital and operating) costs
• Potential environmental impacts
Cost, energy and GHG emissions
Power consumption
Flow-specific Power Use Breakdown, based on Product Water Flow (kWh/ML)
5,000
4,500
Error bars denote indicative range between 5%ile (lower) & 95%ile (upper)
for total
4,000
Product Water Distribution
Production
Raw Water Intake
Power Use (kWh/ML)
3,500
3,000
2,500
2,000
1,500
1,000
500
0
1 - SWRO
2 - IPR
3 - DPR
Option
4 - Dual Pipe
Greenhouse gas emissions
Flow-specific GHG Emissions Breakdown, based on Product Water Flow (kg CO2-e/ML)
6.0
Error bars denote indicative range between 5%ile (lower) & 95%ile (upper)
for Total (Scopes 2 & 3)
50%ile values plotted in columns
GHG emissions (tonnes CO2-e/ML)
5.0
Scope 3 - Sludge Disposal
Scope 3 - Membranes (negligible)
Scope 3 - Chemicals
4.0
Scope 3, Electricity
Scope 2
3.0
2.0
1.0
0.0
1 - SWRO
2 - IPR
3 - DPR
Option
4 - Dual Pipe
Social acceptance of DPR
• A significant challenge
• Numerous important factors
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Trust in organisations involved
Protection of public health is clear
The ‘Yuck factor’
Participation in planning
Timing of information
Religion?
Prior knowledge and understanding of urban water cycles
• But some interesting recent research on DPR
– Context and language
– Effect of Prior Knowledge of Unplanned Potable Reuse on the
Acceptance of Planned Potable Reuse
Report findings
• DPR can safely supply drinking water directly into the water
distribution system, but needs to be designed correctly and
operated effectively with appropriate oversight.
– Current Australian regulatory arrangements can already accommodate
soundly designed and operated DPR systems.
– Australian Guidelines for Water Recycling provide an appropriate
framework for managing community safety and for guiding responsible
decision-making.
• High levels of expertise and workforce training within the
Australian water industry are critical.
– These must be supported by mechanisms to ensure provider compliance
with requirements to use appropriately skilled operators and managers in
their water treatment facilities.
• Planning, decision-making and post-implementation management
processes should acknowledge and respond to community
concerns.
– Public access to information and decision-making processes needs to be
facilitated.
Report findings (cont).
• The relative merits of water supply options should be based on
quantifiable or evidence-based factors
– Public safety, cost, GHG emissions and other environmental impacts, as
well as public attitudes.
– There is little value in distinguishing DPR from other water supply options,
unless specific proposals are compared using these criteria.
• ATSE considers there can be considerable environmental,
economic, and community benefits of DPR in suitable
circumstances.
• ATSE concludes that DPR should be considered on its merits –
among the range of available water supply options for Australian
towns and cities.
• Governments, community leaders, water utilities, scientists,
engineers and other experts will need to take leadership roles to
foster the implementation and acceptance of any DPR proposal in
Australia.