treatment of waste brine from a brackish reverse osmosis plant el paso water utilities and fort...
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Treatment of Waste Brine from a Treatment of Waste Brine from a Brackish Reverse Osmosis PlantBrackish Reverse Osmosis Plant
El Paso Water Utilities and Fort BlissEl Paso Water Utilities and Fort Bliss
Eastside Brackish Groundwater Eastside Brackish Groundwater Desalination FacilityDesalination Facility
Joel C. Rife, P.E., DEEJoel C. Rife, P.E., DEE
September 16, 2002September 16, 2002
CONFLUENCE OF CONFLUENCE OF OHIO AND OHIO AND MISSISSIPPI MISSISSIPPI RIVERSRIVERS
REAL BIG PIPEREAL BIG PIPE
HEAD WATERS OF COLORADO RIVERHEAD WATERS OF COLORADO RIVER
REAL BIG PUMPSREAL BIG PUMPS
Brackish Water Treatment Becoming FeasibleBrackish Water Treatment Becoming Feasible
Membrane Technologies More Affordable
Problem is What to do with the Waste Reject Water
– Direct Discharge Not An Option
– Activated Sludge Microbes Have No Interest In TDS
– Historically Hasn’t Been a Problem with Desalination Plants (Dump in Ocean)
Brackish RO Facility Design CriteriaBrackish RO Facility Design Criteria
Permeate Flow (Drinking Water to Storage) 18 MGD
Evaporation/Concentration Options
RO Plant Recovery 90 Percent
TDS in Reject 11,000 mg/L
Reject Flow 1.8 MGD
Deep Well Disposal Option
Recovery 85 percent (permitting constraints – max. allowable TDS)
TDS in reject 8,000 mg/L
Reject flow 3.2 MGD
Evaporation OptionsEvaporation Options
Full-Scale Evaporation Ponds
Turbo-Mist Evaporator and Pond System
TNRCC Pond Liner Requirements
- Clay w/permeability <1 x 107 cm/sec
- Plastic liner with leak detection
Full-Scale Evaporation PondsFull-Scale Evaporation Ponds
Designed for 5 Consecutive “Critical” Years Storage per TNRCC Requirements
5-Foot Depth
431 Acres
Compared Single Pond vs. 4-cell vs. 15-cell
Recommendation – 4-cell
60-mil HDPE Liner
Turbo-Mist Evaporator Turbo-Mist Evaporator and Pondand Pond
Proprietary Machine by Slimline Mfg. LTD
Nozzles in Ring at End of 100 MPH Wind
Pilot Test Found 15-20% Water Evaporated Through Turbo-Mist Units
Wind Must Remain Below 10 MPH to Prevent Excessive Drift
3000 Connected HP
Cost ComparisonCost ComparisonEvaporation OptionsEvaporation Options
Full-Scale Evaporation Pond
Capital Cost $25.42 Million
20-yr Present Worth $44.36 Million
Turbo-Mist and Pond
Capital Cost $13.8 Million
20-yr Present Worth $56.74 Million
Deep Well DisposalDeep Well Disposal
Evaluation Criteria
Depth
Confining Zone
Simplicity of Geological Structure
Risk of Inducing Seismicity
Injection Zone TDS
One-Hour Pressure Buildup
Distance Traveled After 30 Years
Deep Well DisposalDeep Well Disposal
Capital Cost $9.69 Million
20-yr Present Worth $27.69 Million
Cost Significantly Less Than Evaporation
Regulatory Requirements Are a Concern:
Well Classification Delay Until Hydrogeology and Water Chemistry are Characterized
Permit (Extensive Public Participation)
Authorization by Rule (Less of a Delay)
Solar Gradient PondsSolar Gradient PondsEvolved From Conceptual Zero-Discharge RO Plant Evolved From Conceptual Zero-Discharge RO Plant
Membrane Filtration
Product Water~96% of feed
ThermalDesalination
BrineConcentrator
~1% of feed
Permeate and Distillate
~20% of feed~75% of feed
Saturated Brine Slurry
Raw Water
Salinity Gradient Solar Pond
~5%of feed
Upper Convective Zone
Non-Convective Zone
Lower Convective Zone
Product Salt
Heat
~25%of feed
Membrane Filtration
Product Water~96% of feed
ThermalDesalination
BrineConcentrator
~1% of feed
Permeate and Distillate
~20% of feed~75% of feed
Saturated Brine Slurry
Raw Water
Salinity Gradient Solar Pond
~5%of feed
Upper Convective Zone
Non-Convective Zone
Lower Convective Zone
Product Salt
Heat
~25%of feed
RO Evaporator Concentrator
Product
Water
Solar Gradient PondsSolar Gradient Ponds
Effective for Seawater RO Brine Disposal – 60 Installations World-Wide
Thermal Energy Can Be Used For Heating or To Produce Electricity
Capital Cost $35.2 Million
Cost Comparison per 1000 Gallons Delivered
RO With Full-Scale Evaporation $1.95
RO With Deep Well Disposal $1.46
RO With Solar Gradient Ponds $2.04
Membrane Concentrator SystemMembrane Concentrator System
Goal: Decrease Reject Volume While Deep Well Permitting Process is Completed
Challenge: “Treat the Untreatable”
Solution: Pretreatment Prior to Further Concentration by Reverse Osmosis
Pretreatment Options Investigated:
Lime Softening
High-Rate Nanofiltration
Lime Softening PretreatmentLime Softening Pretreatment
Objective is to Reduce Silica and Carbonate Hardness Back to Original Brackish Reject Water Concentrations
Use of Magnesium Salts for Silica Removal Common Practice for Boiler Feed Water
Lack of Data for Treatment of High Silica Concentrations
Jar Testing Required to Prove Out Silica Removal and Determine Dosage Requirements
Results of Lime Treatment Jar TestingResults of Lime Treatment Jar Testing
Silica and Hardness Removal Goals Achieved with Lime Only
Recirculated Lime Floc Critical
Further Reductions of Silica with Magnesium Salt Addition
Polymer Required to Achieve Acceptable Silt Density Index (<3)
Barium Still a Problem – Final RO Recovery of 60% Due to High Barium
Lime Softening Pretreatment / RO ProcessLime Softening Pretreatment / RO Process
Lime MgO Polymer CO2
Microfiltration Reverse Osmosis98% Recovery 62% Recovery
Solids Contact Basin1.76 MGD 1.72 MGD 1.07 MGD
Brackish RO Reject RO Permeate1.79 MGD Recarbonation Recycle
to ProductWater
Reject Reject40,000 gpd 653,000 gpd
Filtrate and Thickener Overflow 35,000 gpd To storage forfinal disposal
Total wastewater to storage = 728,000 gpd Lime Sludge To On-site Dewatering 28,800 lbs/d - 69,000 gpd @ 5% solids
50% sludge cake Filter Press to landfill Dewatering Thickener
High-Rate NF Softening OptionHigh-Rate NF Softening Option
Suggested by Osmonics Based on Successful Oil Field Experiments
Concept is to Remove Cations (Ca, Mg, Fe, Ba) That Act as Nucleating Sites for Silica, While Passing Silica
“Slick” Single Pass Membrane is Key to Prevent Silica Buildup On Membrane
Successful Bench Scale Experiment Conducted on Simulated Reject
X-Ray Analysis of NF MembraneX-Ray Analysis of NF Membrane
NF Pretreatment / RO ProcessNF Pretreatment / RO Process
Sulfuric Acid to pH 5.8 AntiscalantNanofiltration Membrane Softening Reverse Osmosis95% Recovery 95% Recovery
Brackish RO Reject pH adjustment tanks to 1.7 MGD 1.62 MGD Recycle1.79 MGD off-gas CO2 and Nanofilter Permeate RO Permeate to Product
equalize RO reject flow Water
89,500 gpd Reject 85,000 gpd
To Evaporation Ponds To Evaporation Ponds
Total Reject to Evaporation Ponds = 174,500 MGD
Summary of CostsSummary of Costs
Disposal Option Capital
Cost Annual O&M
Total Present Worth
20 Year Water Production (AF)
PW$/AF
85% Recovery
Deep Well Disposal $9,696,200 750,000 27,696,200 617680 $45
Evaporation Ponds Alone $40,668,300 $995,000 $71,011,000 617680 $115
Lime Softening/RO/Evap $21,864,800 $1,777,200 $61,432,000 662160 $93
NF/RO/Evap $13,564,000 $1,160,200 $39,869,900 682380 $55
90% Recovery
Evaporation Ponds Alone $23,132,400 $657,000 $42,179,400 617680 $68
Lime Softening/RO/Evap $16,201,900 $1,152,011 $43,260,800 641720 $67
NF/RO/Evap $8,636,579 $837,400 $26,032,900 645080 $40
Costs include 15% engineering