Kipp Scott, East Cherry Creek Valley Water and Sanitation DistrictDoug 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

1 mile

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 permita. navigable watersb. irrigation ditches

3. Deep Well Injection 4. Beneficial Uses5. Zero Liquid Discharge Using:

a. thermal/mechanical evaporation systemsb. enhanced evaporation systemc. passive evaporation basins

Brine Concentration & Volume Vs. Recovery

50 60 70 80 90 100

504540353025201510

50

RO C

once

ntra

te T

DS p

pt

(ass

ume

1000

mg/

L ra

w w

ater

)

Recovery Percent

504540353025201510

50

Conc

entra

te V

olum

e %

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 TDS3. Potential Increase in Elements such as

Radionuclides, heavy metals, nitrates4. Potential Inhibitory Effect on Treatment Biology

at High % of Concentrate5. Potential Impact on WET Tests6. 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

SanitarySewerFlow

IrrigationReturn Flow

10-mgdExistingBrackish

Wells@ 1,000

mg/L TDS

POTW

ROSystem

9.3 mgd250 mg/L

10 tons/day40

tons/day 2.5 mgd

7.5 mgd

0.8 mgd @ 10,000 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

MBlend

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 A Wide Range of Commercial and Residential Activities Add TDS to the POTW DischargeActivities 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 water2. 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

0

10

20

30

40

50

60

70

80

90

100

10 mgd BWRO@2000 mg/L

Colorado RoadDeicing

10 mgd Municipal

WWTP

10 mgd WaterSoftener @ 400 mg/L

As CaCO3

Daily Salt Discharge Tons / Day

Courtesy of NYLCV

Approx. 2400 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 AcidCation IX

Weak Acid Cation IX

Reverse Osmosis

Conc. Brine

Conc.Brine

Conc.Brine

HardnessRemoval

PolyvalentCations

High pHSeparation

High PurityWater

GroundWater

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 LayerAir 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

32Secondary 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 TDSLPRO @ 85%

Brine Minimization1.2 MGD Concentrate

4600 mg/L TDS

0.3 MGD Brine @ 18,000 mg/L TDS

0.9 MGD Permeate500 mg/L TDS

140 psi

High Recovery RO @ 75%

10.8 MGD Blend

300 mg/L TDS

Pre-treatment

3.3 MGD By-Pass Blend

Residuals

Deep Well Injection

High pressure Injection Pump10,000 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

$0.58 N/A $0.58

Enhanced Evaporation and Landfill of Dry Solids

$1.74 N/A N/A

Deep Well Injection N/A $0.08 $0.02

Total ZLD O&M Cost $2.32 $0.08 $0.60

Thank you, and Time for Questions

Doug Brown 303-383-2316 direct 303-915-3042 cell BROWNDR@CDM.COM