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