Arsenic Removal from OU Water. Sami Karam Randy Goll Ross Chaffin Roman Voronov

Transcription

1 Arsenic Removal from OU Water Sami Karam Randy Goll Ross Chaffin Roman Voronov Arrsseeni icc Reemovvaal l ffrrom OU Waatteerr

2 OBJECTIVES To find an economical solution to the Arsenic problem on the OU campus To make the OU campus self-sufficient sufficient and compliant with the new 2006 EPA rule of 10 ppb instead of 50 ppb As. minimum

3 EFFECTS of ARSENIC Skin alterations and lesions Repeated exposure may lead to cancerous mutations Nervous & Vascular system degenerative diseases

4 GEOGRAPHY

5 GEOLOGY

6 Well Data Average ph ~8.97 Sulfate content 40 ~ 55 mg/liter Arsenic 35 ~ 45 ppb

7 OU Situation Max production capacity: gallons / day Average daily usage: gallons / day Peaks around gallons / day Projected growth over 20yrs: 25 %

8 Previous Solutions and Available Options

9 Previous Studies CH2M-Hill Hill: : Colorado based consulting company (development, environmental solutions, design ) CH2M Hill Considered OU & the City of Norman as one problem CE 5244: : Class project to find optimal solution

10 CH2M-Hill Hill Report Options Drill new wells Coagulation/Filtration Ion Exchange Nanofiltration Blending water

11 CE 5244 Recommendations April 2001 Recommended reconfiguration, blending and Ion Exchange for Norman Recommended C/F for OU

12 Water Purchase Option OU buys water from City of Norman exclusively Cost between $0.85/1000 gallons and $1.14/1000 gallons of water Least work for OU May not be most economical option, lots of parameters

13 Nanofiltration Uses membrane separation Differences in pressure cause water to separate into 2 streams Very large waste stream (>35%) Membranes have high capital cost

14 Coagulation/Filtration FeCl 3 is added to water Precipitates Fe(OH) 3 Arsenic adsorbs to Fe(OH) FeOH is filtered from the water Fair amount of waste

15 Ion Exchange Water run through bed of resin Arsenic ions exchange with chloride Resin bed is regenerated by brine Very low capital cost!!! Very low operating cost!!!

16 Annual and Capital Costs Nanofiltration Coagulation/Filtration Water Purchase ($1.14/1000 gal) Water Purchase ($0.85/1000 gal) Ion Exchange Capital Costs over $10,000,000 $3,400,000 None None $1,870,000 NPC (after 20 years) over $10,000,000 $5,700,000 $5,565,000 $4,150,000 $3,600,000

17 Net Present cost ($millions) Solutions Comparison WP IX C/F Nano. CH2M-Hill CE5244 Our Group WP: Water Purchase, IX: Ion Exchange, C/F: Coagulation Filtration Nano: Nanofiltration

18 Preliminary Conclusion Ion Exchange most ideal solution!!! WHY? Economically Attractive Self Sufficiency Immediate Implementation

19 ARSENIC & ION EXCHANGE CHEMISTRY

20 Arsenic Chemistry Arsenic (III) -Non ionic form (H 3 AsO 3 ) -Arsenite Arsenic (V) -Ionic form (HAsO 2-4 ) -Arsenate

21 Arsenic/IX Chemistry Arsenite Arsenate -Sodium Hypochlorite pre-treatment Arsenate ion trades places with Chloride ion. - Resin has higher selectivity to sulfate. Bed causes ph to go down.

22 Arsenic/IX Chemistry Regeneration by Concentrated NaCl -Le Chatelier s Principle Arsenate goes to precipitation tank. ph lowered by H 2 SO 4 FeCl 3 added to precipitation tank to precipitate Fe(OH) 3

23 ION EXCHANGE PROCESS

24 Normal Back-Washing Regeneration Rinse Cycle Operation

25

26 Safety Process must be designed so that arsenic is not allowed to breakthrough.

27 Economic Evaluation (IX vs WP options)

28 Preliminary Findings $16,000,000 Previous Conclusions $14,000,000 Net Present Cost $12,000,000 $10,000,000 $8,000,000 $6,000,000 $4,000,000 $2,000,000 CH2M Hill CE Group Our Group $0 WP IX C/F NF WP: water purchase, IX: Ion Exchange, C/F: Coagulation Filtration, NF: Nanofiltration

29 Ion Exchange Plant Calculation Assume Constant Demand of 1.1 MGD CI = $2.1 million (based on capacity) OC = $110,000/year (labor, power, and chemical) Project Lifetime =20yrs Calculate NPC!

30 Water Purchase Calculation Assume Constant Demand of 1.1 MGD Constant Water Price = $1.14/1000gal Low Estimate! Project Lifetime = 20yrs Calculate NPC

31 Sources of Uncertainty Several Unknown Factors in Design: Future Water Price Future Water Demand Initial Plant Capacity Unforeseen Changes In Well-field Later Additions To Existing Plant

32 Calculation Complexity NPC for IX Initial Capacity Low Med High Future Plant Additions L M H L M H L M H Future Water Demand L M H L M H L M H L M H L M H L M H L M H L M H L M H

33 Mathematical Model Description Purpose Simulate OU As situation Goal Cheapest Solution (by minimizing NPC) Chooses between IX or WP Meets Water Demand Decides When/How Much to Build Expands Capacity As Needed Buys Wholesale or Emergency Borrows/Repays Money

34 Mathematical Model Parameters CI - $1.1 million ($428/1000gal per day of capacity) OC - $38,000 ($111/1000gal per day of capacity) Demand figures; 25% growth (OU Physical Plant) Water Price: $3.00/1000 gallons Demand Based $1.14/1000 gallons Whole Sale

35 Capital Investment and capacity Capital Investment ($MM) y = x Capacity (MGD) Fixed: Building, Feed Facility, Brine Unit Capacity Based: Number and Sizing of Columns

36 Water Consumption Projection Average Daily Consumption (1000 gal) August (Peak) Consumption Average Consumption Year Solution must meet the needs of OU by month

37 Significant Variables Capital Investment and Operating Cost per 1000 gallons/day should show significant variation. Wholesale water price should be shown for $1.14 (current) and $0.85 (possible) per 1000 gal / day. Water Demand is randomly generated.

38 Main Equations: C s Model in Math Language: = C yr = + yr yr yr 1 ( CI yr + OPyr + Pr ice yr * WPyr * (1 + i) Borrowed yr Repaid yr ) yr = a * z + b Cap Demand yr, mo, s = Q yr, mo, s + WPyr, mo, s CI * yr yr OP yr = α F zξ + β Qyr, mo, ξ = 1 mo s Pr iceyr s = WholeSalePr ice* y yr, s + EmergencyPr ice*(1 y yr,, s Finance Equations: Main Constraints: CapTot yr = ( Capξ + CapAdd ξ ) if ξ ξ CapTot yr Q yr, mo, s Finance Constraints: TotalCost Debt C yr yr = s ztot yr yr p s C s = z if ξ yr, s = 1+ i) * Debt yr 1, s ξ ξ yr ( + Borrowed yr, s Cap MaxCap * mo 20, s = yr, s 2 * i * Debt yr 1 s, s Budget Debt 0 Repaid, yr z yr WP yr, mo, s 1000 * y yr, s ) * df Repaid 0 yr yr, s

39 Mathematical Model Code:

40 Model Results Facility Built In Year 1 (1.6 MGD Capacity) Loan (Repaid Over 10 Yrs) Water Purchased In Peak Months No Facility Upgrades For 20 Year Period Net Present Cost Of $3.1 Million

41 Implications of Model Results 2600 ft 2 Facility Area 2000 Gallon Waste Brine Container Four 6ft Dia.. IX Columns Requires Purchase Of Ferric Chloride, Sodium Hydroxide, Sulfuric Acid And Salt. Highly Automated Labor requirement of less than $20,000/year (CH2M Hill)

42 GEOGRAPHY

43 Cost ($/yr) Yearly Cost With Loan Project Lifetime (yr) Water Purchase Facility Wholesale Water Price $1.14 Interest Rate = 9%

44 Yearly Cost Without Loan Cost ($/yr) Water Purchase Ion Exchange Wholesale Water Price $ Years Interest Rate = 9%

45 Savings per year Current Dollars Savings ($) $1,000,000 $800,000 $600,000 $400,000 $200,000 $0 $1.14/1000 gallons $0.85/1000 gallons Project Lifetime (yr) Savings Increase In Year 12!

46 Net Present Cost Comparison Net Present Cost($MM) Ion Exchange Plant Water Purchase $1.14 $0.85 $0.45 Price of water ($/1000 gal) Water Costs $0.60/1000gal to Produce

47 Risk Assessment

48 Maximum Field Capacity Net Present Cost ($mil) Maximum Field Capacity (1000 gal/day) NPC Shows decisions if capacity is lower

49 Water Price Sensitivity 3.3 Present Cost ($MM) NPC Linear (NPC) Price of high-rate water ($/1000 gal)

50 Uncertainty Analysis Operating Cost $/1000 gallons capacity Area of Water Purchase $1.14 $0.85 Area of Treatment Capital Investment $/1000 gal capacity

51 Doubled values within Treatment Area 400% (for $0.85) or 600% (for $1.14) cost increase required for WP to become favorable. Even with high variability of parameters, treatment is favorable. 35 O p e r a t in g C o s t $ / g a llo n s c a p a c it y $0.85 Area of Treatment $1.14 Area of Water Purchase Capital Investment $/1000 gal capacity

52 Net Present Cost Probability Distribution More $2,700,000 $2,800,000 $2,900,000 $3,000,000 $3,100,000 $3,200,000 $3,300,000 $3,400,000 $3,500,000 $3,600,000 Net Present Cost Frequency

53 Safety

54 Safety More Bed Volumes = Higher Number of Chemicals Required = Higher Operating Cost

55 Safety

56 Conclusion

57 Conclusion: At either price level of water, Ion Exchange treatment costs less Self-sufficiency and full utilization of natural resources via IX treatment By treating water, OU will not contribute as greatly to scarcity of water in the Central Oklahoma Area Waste produced roughly equivalent to one Norman-issued trashcan full of non-hazardous waste per day

58 Recommendations Explore waste dilution to reduce As content to < 0.5% solid concentration (TC) Water by-pass to reduce regeneration Permissible TBLL for Norman Dried precipitate concentration to meet TCLP

59 Conclusion: Net Present Cost($MM) Ion Exchange Plant Water Purchase $1.14 $0.85 $0.45 Price of water ($/1000 gal)