WASTEWATER TREATMENT TRENDS IN THE 21ST CENTURY ACWA Annual Conference Mount Bachelor Village Resort Bend, OR July 25, 26, & 27, 2012 George Tchobanoglous Department of Civil and Environmental Engineering University of California, Davis
Topics Part-1 Some Global Trends Part-2 Uncontrollable Events and Unintended Consequences Part-3 Future Challenges and Opportunities
Part-1 Some Global Trends that will Impact Wastewater Treatment Population Demographics Impact of urban spread Urbanization along coastal areas Climate Change (wetter/dryer) Sea level rise Impact of intense storm events on WWTPs Aging infrastructure
Impact of Urbanization on Plant Siting
Impact of Coastal Population Demographics 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.
Impact of Sea Level Rise on Wastewater Management Infrastructure
Impact of Sea Level Rise on Stormwater Collection System Courtesy City of San Francisco
Impact of Sea Water Rise on Sewer System Courtesy City of San Francisco
Impact of Sea Level Rise on Stormwater Collection System Courtesy City of San Francisco
Climate Change: Impact of Intense Rainfall on Operation of WWTP
Aging Infrastructure Challenges Aging wastewater infrastructure, typical age 75 years, in large cities over 100 years old with excessive exfiltration Flowrates have decreased over the past decade and will continue to decrease 1. Increased corrosion 2. Most conventional gravity sewer design equations no longer suitable 3. Increased mass concentration loading factors have impacted wastewater treatment facilities
Part-2 Impact of Uncontrolled Events and Unintended Consequences Uncontrollable events Natural disasters Chemical costs Unintended consequences Treatment plant siting Water conservation Treatment plant design/energy usage
Impact of Storm Surges on Wastewater Management Infrastructure
Impact of Water Conservation and Drought: Solids Deposition, H 2 S Formation, and Downstream Corrosion due to Reduced Flows
The Impact of Conservation: Enhanced Corrosion and Increased Mass Loadings Reduced flow results in solids deposition Solids undergo decomposition and produce H2S H2S is transported with the water Downstream H2S increases the rate of corrosion Per capita wastewater flow rates decreasing Flow rates will not increase beyond current values Mass loadings of constituents will increase with population growth
Treatment Plant Design: Little Concern for: 1. The use of resources, 2. The consumption of energy, 3. Long-term sustainability, and 4. The carbon footprint At $0.03/kWh energy efficiency was not an Issue.
Part-3 Future Challenges and Opportunities Paradigm shift in view of water Alternative collection systems Energy and nutrient recovery Urine separation Recycling through direct potable reuse Integrated wastewater management
New View of Wastewater: A Paradigm Shift WASTEWATER is a RENEWABLE and RECOVERABLE SOURCE of ENERGY (heat and chemical), RESOURCES, and POTABLE WATER
Use of Existing Collection System For Source Separated Resource Streams
Energy Content of Wastewater Heat energy Specific heat of water = 4.1816 J/g C at 20 C Chemical oxygen demand (COD) C 5 H 7 NO 2 + 5O 2 5CO 2 + NH 3 + 2H 2 O (113) 5(32) Chemical energy (Channiwala,1992) HHV (MJ/kg) = 34.91 C + 117.83 H - 10.34 O - 1.51 N + 10.05 S - 2.11A
Energy Content of Wastewater Constituent Unit Value Wastewater, heat basis MJ/10 C 10 3 m 3 41,900 Wastewater, COD basis MJ/kg COD 12-15 Primary sludge, dry MJ/kg TSS 15-15.9 Secondary biosolids, dry MJ/kg TSS 12.4-13.5
Required and Available Energy for Wastewater Treatment, Exclusive of Heat Energy Energy required for secondary wastewater treatment 1,200 to 2,400 MJ/1000 m 3 Energy available in wastewater for treatment (assume COD = 5.0 g/m 3 ) Q = [500kg COD/1000 m 3 ) (1000 m 3 ) (13 MJ/ kg COD) 6,000 MJ/1000 m 3 Energy available in wastewater is 2 to 4 times the amount required for treatment
Heat Recovery from Wastewater SOURCE : City of Vancouver, Sustainability website retrieved from http://vancouver.ca/sustainability/neutechnology.htm FALSE CREEK ENERGY CENTER
Alternative Technologies for Primary Treatment and Energy Recovery
Urine separation New Concepts for the Future New treatment plant designs will be based on reduced energy usage Significant advances in treatment alternative technologies
Examples of Urine Separation Fixtures
Nutrients and Trace Organics in Domestic Wastewater: A Case for Urine Separation Greywater 100 80 Feces Greywater Feces Greywater Feces Composition, % 60 40 Urine Urine Urine Greywater Relative distribution unknown, preliminary > 70% in urine Feces and urine 20 0 Nitrogen Phosphorus Potassium Volume Trace organics Wastewater constituent Source: Jönsson et al.(2000) Recycling Source Separated Human Urine.
New Biological Treatment Processes Ambient Temperature Anammox Process
Conceptual Future WWTP Schematic Energy and product recovery Solids processing Preliminary treatment Primary Effluent treatment
Return flows contain nitrogen Impact of Recycle Flows on Nitrogen Removal
Recycling Through Direct Potable Reuse
Adapted from OCWD Typical Flow Diagram for the Production of Purified Water
Microfiltration, Cartridge Filters, Reverse Osmosis, and Advanced Treatment (UV), OCWD
Opportunities for the Future: The Southern California Example
Electric Power Consumption in Typical Urban Water Systems System Power consumption, kwh/mgal Northern California Southern California Supply and conveyance 150 8,900 Water treatment 100 100 Distribution 1200 1200 Wastewater treatment 2,500 2,500 TOTAL 3,950 12,700
Wastewater Management Infrastructure
Integrated Wastewater Management With Decentralized, Satellite, Centralized Facilities
Satellite Systems for Reclamation and Reuse
Intercepted In-Building Self-Contained Water Recycle System Reclaimed water is used for toilet flushing, landscape irrigation, and cooling water
Offsetting Potable Water Demand for Irrigation (System has been in Operation for 25 Years, Upland, CA) Courtesy D. Ripley
Review of Opportunities and Challenges Energy and nutrients in wastewater under utilized New models needed for retrofitting collection systems New technologies will revolutionize WWTP Direct potable reuse solves multiple problems with existing wastewater systems and future demographics New integrated infrastructure needed for enhanced water reuse
The Future Replacement or repair infrastructure with the same technology used to create it will perpetuate the same problems now experienced. Careful attention must be devoted in project development and technology implementation to assess potential unintended consequences the unthinkable must be thought.
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