Kipp Scott, East Cherry Creek Valley Water and Sanitation District Doug Brown, P.E. CDM Navigating the Regulatory and Permitting Hurdles for Concentrate Discharge Multi-State Salinity Coalition February 18, 2011

Presentation Outline  Background on ECCV Project  Overview of Brackish Water Reverse Osmosis (RO) Treatment  Factors Affecting Residuals Disposal for Inland Facilities  Disposal Alternatives and Regulatory Issues

Southeastern Denver Has Limited Surface Water Supplies and Relies on Imported Water or Deep Non-tributary Groundwater

 ECCV initially relied on dozens of non-tributary groundwater for its water supply  The Arapahoe and Laramie/Fox Hills aquifers have less than 300 mg/L TDS and 100 mg/L hardness Existing ECCV Water Supply Is Being Depleted and Is Not Renewable

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 Non-potable Irrigation with Reclaimed Water  Denver Treated Water  Block Water Rates  Conservation Incentives Reduced Demand 30% from 1995 ECCV Is Diversifying and Conserving Its Water Supply

ECCV Water Well Production will Decrease 50% in 10 Years Requiring 377 New Wells

 Beebe Draw alluvial wells  Phase I water rights – 70 Ranch  Phase II water rights – Barr & Milton shares  Phase I facilities  Well field  Pump Stations  Waterline The Northern Project

Renewable Groundwater from Northern Project Being Blended with Other District Supplies

Water Treatment Planning Objectives  Consistent quality product  Free of objectionable taste and odors  Water quality meets end user requirements  Consistently meets drinking water standards  Specific water quality targets  Total Dissolved Solids < 300 mg/L  Total Hardness < 100 mg/L  Firm treatment and pumping capacity to meet peak demands  Reliable service  Reasonable operating costs

Selection of Water Treatment Process  High hardness and TDS required blending or reduction of these compounds  Blending is not a long-term solution  Lack of long-term blending sources  Reverse Osmosis selected  Most cost-effective for TDS  Only effective process to consistently meet water quality goals  Also eliminates almost all other potential contaminants from effluent dominated sources  The challenge is the disposal of the concentrate stream (brine) from the treatment process

ECCV Northern Water System 47 MGD Ultimate Capacity

Overview of RO Process and Concentrate Disposal  Typical low pressure RO operating at 85% recovery treating GW with 700 mg/L TDS & 300 mg/L hardness  6.7 MGD of permeate blended with 3.3 MGD of UV treated well water  1.2 MGD of concentrate with 5000 mg/L TDS

RO Concentrate Disposal Options 1. Discharge to Sanitary Sewer System or POTW Discharge 2. Surface Water Discharge through NPDES permit a. navigable waters b. irrigation ditches 3. Deep Well Injection 4. Beneficial Uses 5. Zero Liquid Discharge Using: a. thermal/mechanical evaporation systems b. enhanced evaporation system c. passive evaporation basins

Brine Concentration & Volume Vs. Recovery RO Concentrate TDS ppt (assume 1000 mg/L raw water) Recovery Percent Concentrate Volume % Mass of Salt Discharged is Constant

Potential Impacts of RO Concentrate on Wastewater Treatment Plant 1. Decreased hydraulic residence time and potential impacts on effluent BOD and TSS 2. Increase in effluent TDS 3. Potential Increase in Elements such as Radionuclides, heavy metals, nitrates 4. Potential Inhibitory Effect on Treatment Biology at High % of Concentrate 5. Potential Impact on WET Tests 6. Potential Impact on Equipment Corrosion

Brackish RO Concentrate Typically Does Not Exhibit Acute or Chronic Toxicity

Wastewater System Concentrate Management Options 1. Blend Concentrate with the Treatment Plant Effluent 2. Send Concentrate Through System During Off- Peak Times 3. Pre-treat Concentrate for Specific Contaminants of Concern: Heavy Metals, Nitrates, Radionuclides 4. Develop a Salt Balance for the Basin to Demonstrate No Impact on Total Salt Discharge

River Distribution System Sanitary Sewer Flow Irrigation Return Flow 10-mgd Existing Brackish 1,000 mg/L TDS POTW RO System 9.3 mgd 250 mg/L 10 tons/day 40 tons/day 2.5 mgd 7.5 mgd ,000 mg/L = 30 tons/day of salt 6.8 mgd Adding a RO System to an Existing Water Supply Results in a Neutral Salt Balance Salt M Blend

 Water softeners  Demineralization for labs, electronics manufacturing  Cooling tower blowdown  Boiler feedwater treatment  Beverage production  Laundry operations  pH adjustment A Wide Range of Commercial and Residential Activities Add TDS to the POTW Discharge

Summary of Potential RO Impacts on Wastewater Treatment Plants  Minimal Performance and Water Quality Impacts on Wastewater Treatment Plants Receiving a Small Percentage of RO Concentrate  Potential Hydraulic Impacts if RO Concentrate is a Significant Percentage of the Wastewater Treatment Flow  The Increase in Effluent TDS from a Brackish RO Concentrate Discharge Can Have an Impact on Effluent Reuse Options

Surface Water Discharge Options 1. Discharge to surface water 2. Secondary Recovery (Brine Minimization) to reduce concentrate volume to ~ 3% of RO flow  Enhanced evaporation and landfill of dry solids Use of blowers Pond sizing based on annual volume  Deep well disposal Initial stage w/o secondary recovery

Discharge to Surface Water Typically Avoided Since Daily Salt Discharge from a Brackish RO Project is Significant Daily Salt Discharge Tons / Day mgd mg/L Colorado Road Deicing 10 mgd Municipal WWTP 10 mgd Water 400 mg/L As CaCO 3 Daily Salt Discharge Tons / Day Courtesy of NYLCV Approx tons of Road Salt

NPDES Permit Can Be Based on Discharge Standards or Non-Degradation Criteria  TDS typically is not a discharge standard because wastewater treatment plant can’t remove it  Nitrate, metals, radionuclides are concentrated by RO and can exceed discharge standards  ECCV discharge permit to irrigation ditch was based on non-degradation of groundwater and controlled by Fluoride, uranium and gross alpha  Acute and chronic toxicity discharge standards can be impacted by common ion concentration and ratios

Zero Liquid Discharge (ZLD) Options  Thermal/mechanical evaporation systems: vapor recompression, spray dryers, crystallizers Photo courtesy GE Infrastructure  Low tech evaporation processes: passive solar evaporation basins, enhanced evaporation basins, misters, undulating film evaporators

Passive Evaporation Basins Require Extensive Land Even in Southwest Desert

High Recovery RO Using both WAC and SAC  Removes Ions That  Form Scale  Calcium  Magnesium  Barium  Strontium  Iron  Manganese  Aluminum Strong Acid Cation IX Weak Acid Cation IX Reverse Osmosis Conc. Brine Conc. Brine Conc. Brine Hardness Removal Polyvalent Cations High pH Separation High Purity Water Ground Water  Ambient pH RO Operation  Controls Silica Scaling  Eliminates NaOH Feed

A Low-Cost Solar Basin with an Air Sparger Can Increase Evaporation Rates Gravel Diffuser Layer Air Distribution Grid RO Concentrate Basin Liners

Deep Wells Can Be Used for Final Disposal of Concentrated Brine  23 operating injection wells in Adams and Weld Counties (47 permitted by the State O&G Div.)  ECCV well - EPA permit for a Class 1 well  Underground formations 9,000+ feet below drinking water aquifers and 1,400 ft. above Rocky Mountain Arsenal wells  Estimated injection rate of 200 to 400 gpm  Estimated cost of $2,280,000 per completed well + pipeline from plant to well

31 Brine Injected Below Potable Water Aquifers  Injection wells include outer casing and inner casing to create and annular space that can be monitored for leaks  Corrosion resistent materials compatible with salty brines  Chemical stability of brines during and after injection

32 Secondary concentration of RO concentrate using brine minimization to 3% of flow treated to minimize water rights loss and # of deep disposal wells Deep Well Disposal Option

ECCV Phase 1 Low Pressure RO and Brine Minimization System 7.8 MGD Ground Water 700 mg/L TDS 6.6 MGD Permeate 50 mg/L TDS 85% Brine Minimization 1.2 MGD Concentrate 4600 mg/L TDS 0.3 MGD 18,000 mg/L TDS 0.9 MGD Permeate 500 mg/L TDS 140 psi High Recovery 75% 10.8 MGD Blend 300 mg/L TDS Pre-treatment 3.3 MGD By-Pass Blend Residuals Deep Well Injection High pressure Injection Pump 10,000 ft. Deep Class I Injection Well Acid UV Disinfection

Total Estimated ECCV ZLD O&M costs per 1,000 gallons of net water production Secondary Recovery and Landfill of Dry Solids w/ Enahanced Evap. Deep Well Injection, No Secondary Recovery Deep Well Injection, With Secondary Recovery Secondary Concentration $0.58N/A$0.58 Enhanced Evaporation and Landfill of Dry Solids $1.74N/A Deep Well InjectionN/A$0.08$0.02 Total ZLD O&M Cost$2.32$0.08$0.60

Thank you, and Time for Questions  Doug Brown  direct  cell 