Abel Wolman's The Metabolism of Cities Revisited. A Case for Water Reuse

Transcription

1 Abel Wolman's The Metabolism of Cities Revisited A Case for Water Reuse

2 Slav W. Hermanowicz Department of Civil and Environmental Engineering University of California at Berkeley Takashi Asano Department of Civil and Environmental Engineering University of California at Davis

3 Abel Wolman ( ) 1914 Maryland Department of Health worked on chlorination and filtration 1937 Department of Sanitary Engineering Johns Hopkins University chairman until 1962 President of AWWA major award named

4 "The Metabolism of Cities" "In the U.S. today attention is focused on shortages of water and the pollution of water and air. There is plenty of water, but supplying it requires foresight." "While New Yorkers were watching empty reservoirs, Californians were building aqueducts. Thanks to foresight people in California were watering lawns and filling their swimming pools, while in New York lawns were dying and pools stood empty. " Scientific American, September 1965

5 Past Solutions to Shortages: Water Transportation California aqueduct mi Owens Valley aqueduct mi Colorado aqueduct mi Columbia aqueduct mi

6 "The Metabolism of Cities" Scientific American, September 1965 fuels food air pollutants refuse water wastewater

7 Water as a Commodity Important Differences huge volume and mass limited delivery options absolutely required evolved as public service low value but... waste product still 99.98% pure very large potential for recycling

8 Water Resources at the Doorstep closing the hydrologic cycle

9 Metabolic Pathways gray water black water

10 Ups and Downs of Water Quality Water Quality user drinking water user repurified water downstream user drinking water unpolluted water source reclaimed water receiving water gray water treated effluent wastewater Time Sequence or Extent of Use

11 Water Resources at the Doorstep closing the hydrologic cycle

12 Water Resources at the Doorstep closing the hydrologic cycle

13 Water Resources at the Doorstep closing of hydrologic cycle reliability of supply local control smaller withdrawal and discharges

14 Why reclaim, reuse, recycle? drivers demand discharge limits politics sustainability infrastructure

15 South Bay Water Recycling San Jose-Santa Clara WWTP 170 mgd = m3/d tertiary treatment reclamation facility since customers 60 miles = 100 km pipelines design supply: 21 mgd = m3/d current demand: 2-7 mgd = m3/d future expansion: in mgd = m3/d reclaimed water rates - 23% less than drinking water

16 South Bay Water Recycling driving factors growing water demand currently met mostly by ground water and water transfers freshwater discharge limitations toxics discharge reduction copper political motivations sustainability

17 Discharge Limitations South San Francisco Bay estuary with limited freshwater drainage metropolitan region, industry drinking water supplied from wells treated wastewater - significant contribution San Jose - Santa Clara WWTP mgd = m3/d changing tidal mixing disappearing tidal (salt water) marshes endangered species

18 Why reclaim, reuse, recycle? drivers demand discharge limits politics sustainability infrastructure

19 Current Water Reclamation % Reclaimed > <10 0

20 Challenges institutional economic technical

21 Institutional Challenges water rights prior appropriation public trust beneficial use political and bureaucratic turf struggle central versus local control regional conflicts stakeholders = interest groups large water utilities = urban consumers small water utilities = rural consumers agricultural business industry environmental groups nuts and freaks

22 Economic challenges transportation dual distribution systems users - large and small treatment increasing regulatory requirements for some processes: no economy of scale

23 Water Distribution dual distribution systems alternate distribution

24 Urban Growth overall population increase growth patterns types of urban areas

25 Growth and Water Reuse Population Growth Rate % ( , adjusted) Population Density (cap/sq.mi) Western U.S. Circle area shows water reuse per capita (relative values) Population growth rate adjusted by subtracting avg. growth rate

26 Technical Challenges evolving water quality standards microbial gross organics TOC available and emerging technologies conventional processes membrane filtration process design and integration process selection to meet specific water quality requirements performance control reliability

27 Technical Challenges performance variability log virus concentration cumulative % Tanaka, Asano, Schroeder, Tchobanoglous, WER, 70:39

28 Water as a Commodity quantity currently a dominant factor quality one size fits all? - most restricted use California Use quality criteria Coliforms food crops, toilets, snow, unrestricted recreation & landscape irrigation, industrial process water surface irrigation of food crop, restricted impoundments pasture irrigation, nursery, boiler feed, dust control, road cleaning fodder & processed food irrigation, orchards & vineyards, sewer flushing cfu/100 ml 2.2 Treatment secondary, coagulation, sedimentation, filtration, disinfection 2.2 secondary, disinfection 23 secondary, disinfection no requirement secondary

29 Quality Must Match Use several levels of quality (and cost)

30 Treatment Technology appropriate use application scale - quantity adequate quality

31 What's in the Future? further closing the hydrologic cycle on smaller scales dual, multiple and alternate distribution systems quality matching the needs treatment matching the quality requirements