Michele Robertson, PG

Is Deep Injection a Disposal Option in Arizona?

GATEKEEPER REGULATORY ROUNDUP 2011

February 16, 2011

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

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

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

Conventional Concentrate Disposal Options

Impoundments

Surface water discharges

Sewers

Land disposal (dust control)

Injection wells

Future Concentrate Disposal Options

Pipeline to Sea of Cortez

Remote location of evaporation ponds

High recovery and Zero Liquid Discharge

Alternative uses of concentrate

From Mickley, M., 2006

Relative Cost of Concentrate Disposal Options

CapitalCost

ConcentrateFlow Rate

Sewer

SurfaceWater

Deep WellInjection

Deep WellInjection

SprayIrrigation

EvaporationPond

BrineConcentrator

ZLD

Regulatory Programs – Injection Wells

• Underground Injection Control Program – implemented by EPA

• Aquifer Protection Permit Program – implemented by ADEQ

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

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?

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

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?

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

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

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

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

Questions?