kipp scott, east cherry creek valley water and sanitation district doug brown, p.e. cdm navigating...
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Kipp Scott, East Cherry Creek Valley Water and Sanitation DistrictDoug Brown, P.E. CDM
Navigating the Regulatory and Permitting Hurdles for Concentrate Discharge
Navigating the Regulatory and Permitting Hurdles for Concentrate Discharge
Multi-State Salinity Coalition
February 18, 2011
Presentation OutlinePresentation 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 RenewableExisting 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 SupplyECCV Is Diversifying and Conserving Its Water Supply
ECCV Water Well Production will Decrease 50% in 10 Years Requiring 377 New WellsECCV 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 ProjectThe Northern Project
Renewable Groundwater from Northern Project Being Blended with Other District Supplies
Water Treatment Planning ObjectivesWater 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 ProcessSelection 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 DisposalOverview 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 OptionsRO 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. RecoveryBrine Concentration & Volume Vs. Recovery
50 60 70 80 90 100
504540353025201510
50
RO C
once
ntra
te T
DS
ppt
(ass
ume
1000
mg/
L ra
w w
ater
)
Recovery Percent
504540353025201510
50
Con
cent
rate
Vol
ume
%
Mass of Salt Discharged is Constant
Potential Impacts of RO Concentrate on Wastewater Treatment PlantPotential 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 ToxicityBrackish RO Concentrate Typically Does Not Exhibit Acute or Chronic Toxicity
Wastewater System Concentrate Management Options 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 BalanceAdding 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 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 OptionsSurface 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
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 CriteriaNPDES 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) OptionsZero 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 Passive Evaporation Basins Require Extensive Land Even in Southwest Desert
High Recovery RO Using both WAC and SACHigh 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 RatesA Low-Cost Solar Basin with an Air Sparger Can Increase Evaporation Rates
Gravel Diffuser LayerGravel Diffuser LayerAir Distribution GridAir Distribution Grid
RO ConcentrateRO Concentrate
Basin Liners
Deep Wells Can Be Used for Final Disposal of Concentrated BrineDeep 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 wellsSecondary 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 SystemECCV 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 productionTotal 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 QuestionsThank you, and Time for Questions
Doug Brown 303-383-2316 direct 303-915-3042 cell [email protected]