Wastewater use in irrigated agriculture: closing the rural-urban-rural water loop

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Wastewater use in irrigated agriculture closing
the rural-urban-rural water loop

• Presented at Departmental Seminar Series (Soil,
  Water Environmental Science), University of
  Arizona, 19 February 2007

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Wastewater Use in Irrigated Agriculture Closing
the Rural-Urban-Rural Water Loop Christopher
Scott Udall Center for Studies in Public Policy,
and Dept. Geography Regional Development Univers
ity of Arizona
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Scarcity Competition for Water

• Declining allocations of water to agriculture
• Rapid urban growth a global phenomenon
• Water productivity in agriculture rising (more
  crop per drop)
• Agriculture increasingly adapting to the use of
  poorer quality water for irrigation

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Sobering Demographics

• 880 million additional population by 2015,
  virtually all in developing countries.
• After 2015, all worldwide growth in population
  will take place in developing country cities.

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Urban Explosion

• India will soon cross the 50-50 urban-rural
  population threshold 750 million urban Indians
  by 2050.
• China is actively planning for cities each with
  more than 100 million population.
• Africas urban population growth rates among the
  highest in the world.
• Latin America has been predominantly urban for
  generations.

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Urban Water Supply Growth
Millennium Development Goals face resource
constraints (water, investment). Progress towards
sanitation goals lagging behind water supply
therefore, wastewater management is critical.
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Definitions

• Wastewater partially treated or untreated urban
  sewage
• Effluent treated to secondary or tertiary
  levels (with or without disinfection)

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Rural-Urban-Rural Water Loop

• Transfer of water from agriculture to cities
• Physically, often entails inter-basin transfers
• Water rights, property regime, economic issues
• Urban use, quality degradation depletion
• Salinity load, even with (because of?) treatment
• Public health risk (consumers and producers)
• Agricultural end use of wastewater/ effluent
• Adapt to quality (nutrients, salinity)
• Adapt to timing (uniform throughout year)

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Rural-Urban-Rural Loop Typology
Rural source Urban use Rural end use
Production irrigated ag. Multiple (w/ urban sprawl on ag.). Wastewater WW mixed source for in-formal urban periurb. ag. e.g. Hyderabad, India - Musi
Small-scale rural water Multiple use. Wastewater WW primary source for production irrigated ag. e.g. Mexico City - Mezquital
Production irrigated ag. Multiple use. Effluent Same ag. users as source water (i.e., water swap with treatment). e.g. Monterrey, Mex. Bajo Rio San Juan
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Hyderabad, India
Sampling Transects III rural (25 40 km) II
periurban (10 25 km) I urban (0 10 km)
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Hyderabad Water Footprint
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Hyderabad Water Supply/ Demand
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Wastewater Biogeochemistry

• Microbial attenuation and infection
• Coliform die-off
• Nematode (hookworm) egg deposition
• Heavy metals attenuation ( uptake?)
• Deposition, re-suspension
• Nutrient attenuation plant uptake, eutrophicn.
• Dissolved solids concentration, deposition
• Irrigation diversion, evaporation, return flow

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40 Km
Hyderabad
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Coliforms in WastewaterDec. 03 Jan. 05 (red
squares mean value)
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Nematode Eggs in Wastewater
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Nematode Prevalence in Farmers
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Sediment Sampling
Mean egg load per 1 kg of sediment 410,000 (SD
240,000)
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Heavy Metals in Sediment
Source Gerwe, Caroline. An Assessment of Heavy
Metals Contamination in the Wastewater-Irrigated
Area of the Musi River
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Dissolved Nitrogen
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Dissolved Oxygen
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Total Dissolved Solids
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TDS Seasonal Variation
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TDS Conceptual Model
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Irrigation Adapts to Constant Flow
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Mexico City Water Footprint
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Mexico City Wastewater Sources/Fate
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Tula Irrigation District
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Nutrient Uptake, Salt Concentration
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Monterrey-Bajo Río San Juan Swap
Falcon Reservoir
Marte R. Gómez Reservoir
McAllen, Texas
Bajo Río San Juan Irrigation District
Tamaulipas
El Cuchillo Reservoir
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El Cuchillo

• Constructed in 1993
• Supplies 5 m3/s to Monterrey (to be increased to

• 10 m3/s)
• MR Gómez reservoir impacts

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Negotiated Settlement

• 9 Oct. 1989 Monterrey, federal and Nuevo León
  governments agree to finance and construct El
  Cuchillo dam
• 6 Sept. 1990 Tamaulipas, federal and Nuevo León
  governments agree to rationalize water use,
  preserve multiple uses of BRSJ irrigation water

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Effluent the Bargaining Chip

• Federal CNA allocates 189 MCM (6 m3/s) of
  effluent from Monterrey to BRSJ irrigators
• Nuevo León assumes responsibility and cost of
  treatment in compliance with federal water
  quality standards
• Rehabilitation of the Anzaldúas-Rhode pumping
  station on the Río Bravo
• Relocation of downstream Tamaulipas urban water
  demand from MR Gómez reservoir (Rhode canal)

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BRSJ Irrigation Water Productivity
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BRSJ Irrigation Efficiency
But, growing upstream demand and capture of
wastewater will need to pipe it 100 km.
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Wastewater Use Conclusions

• Urban growth high tertiary treatment costs
  increasing agricultural reuse
• Promote beneficial agricultural reuse
• Mitigate health and environmental risk

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Risk Mitigation

• Secondary treatment (biosolids handling
  enforcement is essential)
• Application method to limit irrigators exposure
• Market wash water and handling
• Crop restrictions non-edible and fodder. Limit
  fresh produce irrigation, e.g.

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Treatment for Compliance

• WHO - 103 faecal coliforms/100 ml
• Cost of treating raw sewage used for direct
  irrigation to meet WHO standard is approx US125
  per case of infection (of hepatitis, rotavirus,
  cholera, or typhoid) prevented (Fattal, Shuval,
  Laempert, 2004).
• USEPA zero incremental risk
• Incremental cost of further treating wastewater
  from WHO to USEPA standard approx. US450,000 per
  case of infection prevented (Fattal, Shuval,
  Laempert, 2004).

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Policy Implications

• Planned reuse offers no easy solutions
• Key to success are
• coherent legal and institutional framework
• coordination of multiple government agencies
• flexible application of the polluter pays
  principle
• extension to farmers of appropriate practices for
  wastewater use
• public awareness campaigns to build social
  acceptability for reuse

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Wastewater Use in Irrigated Agriculture

• http//www.cabi.org/bk_BookDisplay.asp?PID1785
• http//www.idrc.ca/en/ev-31595-201-1-DO_TOPIC.html
  
• Introduction management challenges
• Typology and global assessment
• Livelihoods the key driver
• WHO health guidelines
• Cost of guidelines compliance

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Case Studies in the Book

• Kenya
• Ghana
• Vietnam
• Pakistan
• Senegal
• India

• Bolivia
• Mexico
• Jordan
• Tunisia

Formal programs of planned reuse with treatment
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Thank you.

• Christopher Scott
• cascott_at_email.arizona.edu
• 626-4393

• Acknowledgements
• Stephanie Buechler, UA Bureau of Applied
  Research in Anthropology
• Pay Drechsel, International Water Management
  Institute, Ghana
• Jeroen Ensink, London School of Hygiene and
  Tropical Medicine
• Naser Faruqui, International Development
  Research Centre
• Francisco Flores, Cornell University
• Jesús R. Gastélum, UA Dept. of Civil Engineering
• Liqa Raschid, International Water Management
  Institute
• Daan van Rooijen, International Water Management
  Institute, Ghana