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Deep Injection in Arizona: Disposal Options & Regulatory Compliance

Explore deep well injection as a concentrate disposal method in Arizona. Compare costs, regulations, and future options for sustainable management. Understand aquifer reclassification process and narrative standards policy implications. Get insights on technical considerations and concentrate management research for effective solutions.

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Deep Injection in Arizona: Disposal Options & Regulatory Compliance

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  1. Is Deep Injection a Disposal Option in Arizona? GATEKEEPER REGULATORY ROUNDUP 2011 February 16, 2011 Michele Robertson, PG

  2. Topics for Discussion Sources of TDS and concentrate Concentrate disposal options Cost comparison of concentrate disposal options Programs that regulate injection wells in Arizona Policy implications Conclusions

  3. Sources of Salt (Total Dissolved Solids) Water sources – Colorado River, Salt River, groundwater Expanded use of home water softeners Additional TDS increase during wastewater treatment (100 – 150 mg/L) Brine from salt cavern development for natural gas or compressed air storage

  4. Concentrate Sources (Treatment Residuals) Advanced wastewater treatment options (RO, EDR, MF) RO reject waters discharged to sewers concentrated in WWTP Water treatment for arsenic removal, etc. Desalination of brackish water sources resulting from development of poorer quality water

  5. Conventional Concentrate Disposal Options • Impoundments • Surface water discharges • Sewers • Land disposal (dust control) • Injection wells

  6. Future Concentrate Disposal Options • Pipeline to Sea of Cortez • Remote location of evaporation ponds • High recovery and Zero Liquid Discharge • Alternative uses of concentrate

  7. Relative Cost of Concentrate Disposal Options Evaporation Pond Brine Concentrator ZLD Spray Irrigation Capital Cost Deep Well Injection Surface Water Sewer Concentrate Flow Rate From Mickley, M., 2006

  8. Regulatory Programs – Injection Wells Underground Injection Control Program – implemented by EPA Aquifer Protection Permit Program – implemented by ADEQ

  9. Regulatory Programs • Underground Injection Control Program (EPA) • 6 classes of injection wells • Underground source of drinking water is ≤10,000 mg/l TDS • Numerous permits issued nationwide – 7 Class I permits issued in CA for wastewater disposal • Aquifer Protection Permit Program (ADEQ) • Injection wells are discharging facilities • All aquifers are protected for drinking water use • Permits for injection of reclaimed water, solution mining, LPG storage, CO2 sequestration

  10. Arizona Policy Issues Can disposal by injection be permitted in AZ? Does injection require reclassification of the receiving aquifer? Assuming TDS is pollutant of concern, can narrative standards policy be applied?

  11. Reclassification of an Aquifer Reclassification of aquifer requires public process Consultation with local GUAC if in AMA Demonstration: Hydrologic isolation Water not being used as drinking water Benefits of degradation outweigh costs to the public of reclassification

  12. Reclassification Process • Reclassification petition to ADEQ must include: • Proposed use and pollutant for reclassification • Hydrogeologic report that demonstrates hydrologic isolation • Documentation that aquifer is not used for drinking water • Cost-benefit analysis • ADEQ review of complete petition within 120 days • ADEQ must initiate rulemaking to adopt new AWQS • Lengthy process • What standard for TDS?

  13. The Use of Narrative AWQS to Develop Permit Conditions for APPs (Policy 3010.000) Narrative AWQS rule states that pollutant: Cannot endanger human health Cause or contribute to violation of SWQS Impair existing or foreseeable future uses of water Establish a UPL at nearest point of use downgradient of discharge Set AL at point of compliance to protect UPL and establish contingency plan

  14. Technical Issues • Finding right hydrogeologic setting: • Injection zone with sufficient porosity, permeability and thickness to accept volume and rate of injection • Lateral extent of geologic conditions • Upper confining layer of sufficient thickness to ensure protection of drinking water uses, lower confining layer • No faulting, fractures or seismic activity • Location close to concentrate source

  15. Concentrate Management Research: • Reduce volume • Improved recovery does not solve disposal problem • Reduce energy and other costs • Conventional ZLD is very energy intensive • Provide for beneficial reuse • Find new uses for concentrate • Overcome/address institutional barriers

  16. Conclusions • Regulatory framework exists to permit injection wells for wastewater disposal: • Reclassification of aquifers process is likely to be difficult and time intensive • Narrative standards policy provides a reasonable permitting approach • To date, no injection tests in AZ have demonstrated the suitable geologic conditions needed for injection

  17. Questions?

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