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TRENDS IN INDIRECT AND DIRECT POTABLE REUSE
2012 NWRI Clarke Prize ConferenceResearch and Innovations in Urban Water Sustainability
NOVEMBER 2, 2012
George TchobanoglousDepartment of Civil and Environmental Engineering
University of California, Davis
Topics
• Types of reuse accepted worldwide• How to think about wastewater• Indirect and direct potable reuse• Treatment technologies• Regulatory framework• Need for uniform accepted vocabulary
TYPES OF REUSE ACCEPTED WORLDWIDE
Types of Reuse Worldwide
• Agricultural irrigation (seasonal demand)• Landscape irrigation (seasonal demand)• Industrial (constant demand, site specific)• Non-potable urban uses (limited volumes)• Recreation/environmental uses (site specific)• Indirect potable use through groundwater
recharge (requires suitable aquifer)• Indirect potable use through surface water
augmentation (availability of reservoir sites)• Direct potable use (best option, but public
perception issues must be dealt with)
DIRECT AND INDIRECTPOTABLE REUSE
Driving Forces for Direct and Indirect Potable Reuse
• The value of water will increase significantly in the future (and dramatically in some locations)
• De facto indirect potable reuse is largely unregulated (e.g., secondary effluent, ag runoff, urban stormwater, highway runoff)
• Infrastructure requirements limit reuse opportunities• Existing and new technologies can and will meet the
water quality challenge• Population growth and global warming will lead to
severe water shortages in many locations. A reliable alternative supply should be developed
• Must think differently about water
De Facto Indirect Potable Reuse
Courtesy City of San Diego
Impact of Coastal Population Demographicson Reuse, Hyperion WWTP, Los Angeles, CA
Urbanization Along Coastal Areas
• By 2030, 60 percent of world’s population will near a coastal region
• Withdrawing water from inland areas, transporting it to urban population centers, treating it, using using it once, and discharging it to the coastal waters is unsustainable.
How to Think About Wastewaterin the 21st Century
Wastewater is a renewable recoverable source of energy, nutrients, and potable water
Definition of Planned Indirect and Direct
Potable Reuse
De Facto and Indirect Potable Reuse(existing in fact, whether recognized legally or not)
Upper Occoquan,San Diego, CA (Proposed)
Surface Water Buffer
OCWDGroundwater Buffer
TYPES OFPROJECTS
Infiltration Basin, Florida, USA
Kraemer/Miller Spreading Basins, OCWDand Legacy Regulations
Barrier Injection Wells
Indirect Potable Reuse ThroughSurface Water Augmentation: San Diego, CA
Courtesy City of San Diego
San Vincente Reservoir, San Diego County
So What is the Issue?
If a significant amount of wastewater is to be recycled from large cities without the availability of suitable environmental buffers (either groundwater or surface water), then direct potable reuse, with adequate protective measures will have to be implemented
Direct Potable Reuse With and Without Engineered Storage Buffrer
Proven and ConceptualEngineered Storage Buffer Systems
TRENDS IN TREATMENT TECHNOLOGIES
Typical Flow Diagram for the Production of Purified Water
Adapted from OCWD
Microfiltration, Cartridge Filters, Reverse Osmosis, and Advanced Treatment (UV), OCWD
Treatment Process Flow DiagramBig Springs, Texas (c.a. 2011)
Treatment Process Flow DiagramWindhoek, Namibia
Technologies for the Removal ofTrace Constituents and Unknowns
Adapted from Sundaram et al., 2009
Comparison of Technologies for the Removal of Trace Constituents & Unknowns
Adapted from Sundaram et al., 2009
Item MF-Ozone-BAC MF-RO-UV/PeroxideFate of trace organics Degraded Removed and degradedReject/side streams Minor (periodic
backwash water)Major (up to 20%)
Salinity Unchanged Decreased significantlyCorrosivity Unchanged Increased (requires
buffering)Energy consumption without MF
0.03 - 1.0 kWh/m3 8 - 10 kWh/m3
TechnologicalImplementation,Process for DPR
OPPORTUNITY FORDIRECT POTABLE
REUSE INSOUTHERN CALIFORNIA
Opportunity for Direct Potable Reuse:The Southern California Example
Electric Power Consumptionin Typical Urban Water Systems
SystemPower consumption, kWh/Mgal
Northern California
SouthernCalifornia
Supply and conveyance 150 8,900
Water treatment 100 100
Distribution 1200 1200
Wastewater treatment 2,500 2,500
TOTAL 3,950 12,700
Opportunity for Direct Potable Reuse:The Southern California Example
Wastewater Management Infrastructure -Potential Locations for Water Plants
OCWD type plant
Benefits of the Southern California Example
• Reliable alternative source of supply, more secure from natural disasters
• Lower cost and reduced energy usage• 30 billion for peripheral tunnels versus 5 billion for
treatment • More water available for agricultural use, especially
during drought periods• Environmental benefits for bay delta habitat
restoration
REGULATORYREQUIREMENTS
Science Versus Regulations
Pre 1880sPhysical observations - No Science - Common sense practices (regulations)
Enlightenment 1880-1980sScience develops - Semi-scientific, observational, and empirical regulations follow
Post 1980sScience leaps ahead - Science based regulations have evolved, but have not kept pace - Semi-empirical and empirical legacy regulations persist.
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NEED FOR UNIFORM ACCEPTED
TERMINOLOGY
Need for Accepted Vocabulary
Issues• There is a need to speak with one voice• Not everyone agrees that indirect potable reuse is
acceptable• Little standardization of terms (e.g., indirect and
direct potable reuse)Consequence• Everyone says whatever suits their particular interest • The public is confused, especially about the safety of
reclaimed water.• A uniform vocabulary is of critical importance, if reuse
projects are to be discussed rationally
Take Home Message
Ultimately, direct (and indirect) potable reuse is inevitable in urban areas and will represent an essential element of sustainable water resources management
• Must think of wastewater differently.• To make it a reality, bold new planning
must begin now!! Water and wastewater agencies must be integrated
• The public is supportive.
THANK YOU FORLISTENING