ACWA Annual Conference Mount Bachelor Village Resort Bend, OR July 25, 26, & 27, 2012

Transcription

1 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

2 Topics Part-1 Some Global Trends Part-2 Uncontrollable Events and Unintended Consequences Part-3 Future Challenges and Opportunities

3 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

4 Impact of Urbanization on Plant Siting

5 Impact of Coastal Population Demographics Hyperion WWTP, Los Angeles, CA

6 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.

7 Impact of Sea Level Rise on Wastewater Management Infrastructure

8 Impact of Sea Level Rise on Stormwater Collection System Courtesy City of San Francisco

9 Impact of Sea Water Rise on Sewer System Courtesy City of San Francisco

10 Impact of Sea Level Rise on Stormwater Collection System Courtesy City of San Francisco

11 Climate Change: Impact of Intense Rainfall on Operation of WWTP

12 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

13 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

14 Impact of Storm Surges on Wastewater Management Infrastructure

15 Impact of Water Conservation and Drought: Solids Deposition, H 2 S Formation, and Downstream Corrosion due to Reduced Flows

16 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

17 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.

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19 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

20 New View of Wastewater: A Paradigm Shift WASTEWATER is a RENEWABLE and RECOVERABLE SOURCE of ENERGY (heat and chemical), RESOURCES, and POTABLE WATER

21 Use of Existing Collection System For Source Separated Resource Streams

22 Energy Content of Wastewater Heat energy Specific heat of water = 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) = C H O N S A

23 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 Primary sludge, dry MJ/kg TSS Secondary biosolids, dry MJ/kg TSS

24 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

25 Heat Recovery from Wastewater SOURCE : City of Vancouver, Sustainability website retrieved from FALSE CREEK ENERGY CENTER

26 Alternative Technologies for Primary Treatment and Energy Recovery

27 Urine separation New Concepts for the Future New treatment plant designs will be based on reduced energy usage Significant advances in treatment alternative technologies

28 Examples of Urine Separation Fixtures

29 Nutrients and Trace Organics in Domestic Wastewater: A Case for Urine Separation Greywater Feces Greywater Feces Greywater Feces Composition, % 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.

30 New Biological Treatment Processes Ambient Temperature Anammox Process

31 Conceptual Future WWTP Schematic Energy and product recovery Solids processing Preliminary treatment Primary Effluent treatment

32 Return flows contain nitrogen Impact of Recycle Flows on Nitrogen Removal

33 Recycling Through Direct Potable Reuse

34 Adapted from OCWD Typical Flow Diagram for the Production of Purified Water

35 Microfiltration, Cartridge Filters, Reverse Osmosis, and Advanced Treatment (UV), OCWD

36 Opportunities for the Future: The Southern California Example

37 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 Distribution Wastewater treatment 2,500 2,500 TOTAL 3,950 12,700

38 Wastewater Management Infrastructure

39 Integrated Wastewater Management With Decentralized, Satellite, Centralized Facilities

40 Satellite Systems for Reclamation and Reuse

41 Intercepted In-Building Self-Contained Water Recycle System Reclaimed water is used for toilet flushing, landscape irrigation, and cooling water

42 Offsetting Potable Water Demand for Irrigation (System has been in Operation for 25 Years, Upland, CA) Courtesy D. Ripley

43 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

44 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.

45 THANK YOU FOR LISTENING