PRETREATMENT PROCESSES FOR POTABLE WATER TREATMENT PLANTS

Transcription

1 7 May 2014 PRETREATMENT PROCESSES FOR POTABLE WATER TREATMENT PLANTS JEFF LINDGREN ENGINEERING MANAGER B&V WATER

2 AGENDA Conventional Pretreatment Focus on Clarification (including Sedimentation) Theory/Goals of Clarification Review of High Rate Clarification Technologies Comparison of Technologies Project Examples 2

3 CONVENTIONAL PRETREATMENT Typically. Rapid Mix Flocculation Sedimentation Filtration Advantages Simplicity Widely used Handle varying water quality Familiarity (Regulatory, Operations) Disadvantages Large Footprint Higher cost, particularly with limited site Wind/algae growth/solids removal 3

4 THEORY/GOALS OF CLARIFICATION 4

5 THEORY/GOALS OF CLARIFICATION Clarification Part of pretreatment process Multiple goals turbidity/particles, Total Organic Carbon (TOC), etc. Remove solids prior to filtration maximize filtration processes Sizing often defined in hydraulic loading rate (gpm/sf or m/hr) translates to settling velocity 0.5 gpm/sf = 1.2 m/h = ft/min Vo = Depth/Detention Time = Q/A (gpm/sq. ft. or m/hr) 5

6 THEORY/GOALS OF CLARIFICATION Why consider something besides conventional clarification? Limited real estate available Cost advantages often site specific Raw water quality Algae Light floc Regardless of clarification process chosen: Coagulation/flocculation conditioning of floc is critical Settled turbidity is not end goal 6

7 REVIEW OF HIGH RATE CLARIFICATION TECHNOLOGIES 7

8 HIGH RATE CLARIFICATION OPTIONS Plate and Tube Settlers Upflow Solids Clarifiers (Pulsator) Solids Contact Clarifiers (Densadeg) Ballasted Flocculation Dissolved Air Flotation (DAF) Others: Contact Adsorption Clarifiers Direct Filtration 8

9 RELATIVE LOADING RATES Surface Loading Rate gpm/sq. ft. Conventional Tube Settler Super Pulsator Plate Settler DAF Densadeg Ballasted Flocculation Higher Loading Rate = More Capacity 9

10 CLARIFICATION TECHNOLOGIES CONDITIONS OF APPLICABILITY Coagulant Dose, mg/l DAF (Heavy Particles) DAF (Light Particles) Conventional Sedimentation Tube and Plate Settlers Solids Clarifiers Ballasted Flocculation 10 DF CAC Turbidity, NTU 10

11 INCLINED PLATE SEDIMENTATION Courtesy: JMS 11

12 1. PARTICLES FALL VERTICALLY THEREFORE SEE THE AREA = TO THE HORIZONTAL PROJECTED AREA 2. THE HORIZONTAL PROJECTED AREA OF ALL OF THE PLATES ARE ADDED UP Courtesy: MRI 3. AS A RESULT A BASIN WITH PLATES REQUIRES MUCH LESS AREA THAN A BASIN WITHOUT PLATES

13 INCLINED PLATE SEDIMENTATION 13

14 INCLINED PLATE SEDIMENTATION Effective surface loading rates without plates Surface water with Alum or Ferric gpm/ft 2 Presedimentation gpm/ft 2 Equivalent surface loading rates with plates: Courtesy: JMS 14

15 INCLINED PLATE SEDIMENTATION Advantages Small footprint area / easily covered Widely used Potential $ savings vs. conventional Disadvantages Deeper basin required Not always amenable to retrofits in existing basins Obstruct access and view of sludge collection equipment Considerations Consistency of floc size Sludge withdrawal Retrofits space beneath plates 15

16 TUBE SETTLERS Similar concept to plate settlers Shorter length can often more easily fit in existing basins Less $ than plates Less control of flow as compared to plates Where large solids volume, can be susceptible to re entrainment of solids Longevity 16

17 UPFLOW SOLIDS CLARIFIER (IDI SUPERPULSATOR) Sludge blanket clarifier (2 4 gpm/ft 2 ) Flocculation and sedimentation in one basin Pulsed flow through the basin created by vacuum pump Inclined plates with and without tube settlers 20+ Years of installed experience over 150 US installations 17

18 Superpulsator Clarifier Collection Channel Vent Valve Vacuum Pump Vacuum Chamber Blowdown Pipes Collection Laterals Concentrator Settling Plates Distribution Channel Distribution Laterals Courtesy: IDI 18

19 Superpulsator Type U Clarifier Vent Valve Vacuum Pump Collection Channel Vacuum Chamber Collection Laterals Lamellar Tubes Blowdown Pipes Concentrator Distribution Channel Distribution Laterals Settling Plates Courtesy: IDI 19

20 VENTING AND PULSING Vent Valve Open Vacuum Pump Vent Valve Closed Vacuum Pump Vacuum Chamber Vacuum Chamber Sludge Blanket Expansion Sludge Blanket Contraction Periodic sludge discharge 0.2 to 0.5% solids Venting: 8 to 12 seconds Pulling a Vacuum: 40 to 50 seconds Courtesy: IDI 20

21 UPFLOW SOLIDS CLARIFIER (IDI SUPERPULSATOR) 21

22 UPFLOW SOLIDS CLARIFIER (IDI SUPERPULSATOR) Advantages No moving parts below surface Ability to incorporate PAC in sludge blanket (T&O/TOC) Potential $ savings vs conventional Capable of high flocculation efficiency Proven performance / state acceptance Disadvantages Heavy solids can settle and require periodic removal Can be difficult to control when flow rate or water quality change Considerations Settling velocity of solids homogeneous and controlled Susceptible to upset with temperature change Need to manage blowdown 22

23 SOLIDS CONTACT CLARIFIER (IDI DENSADEG) High rate solids contact clarifier (8 12 gpm/ft 2 as compared to for traditional SCUs) Mixing, solids recirculation, clarification/ thickening Versatile clarification, softening, residuals handling Water and wastewater applications 20 Years of installed experience over 50 US installations and 150 installations worldwide 23

24 SOLIDS CONTACT CLARIFIER (IDI DENSADEG) Turbine Draft Tube Rapid Mix Reactor Reactor Turbine Drive Clarifier / Thickener Launder Assembly Recirculation Cone Lifting Assembly Settling Tube Assembly Coagulant Polymer Settling Tube Support Flow Splitter Sludge Recycle Pump Sludge Recirculation Sludge Blowdown 24

25 DESIGN CRITERIA REACTOR RETENTION: 8-10 min LOADING RATE: 8 to 10 gpm/ft 2 (clarification) 10 to 15 gpm/ft 2 (softening) CAPACITY per UNIT: 1 to 22 MGD (concrete) 0.15 to 14 MGD (steel) RAPID MIX RETENTION: 2 to 3 min (clarification) SLUDGE RECYCLE: 3% to 6% CLARIFIER RETENTION: 23 to 28 min SLUDGE BLOWDOWN: 2% to 4% (clarification) 5% to 20% (softening) 25

26 SOLIDS CONTACT CLARIFIER (IDI DENSADEG) 26

27 SOLIDS CONTACT CLARIFIER (IDI DENSADEG) Advantages Small footprint area Ability to incorporate PAC Potential $ savings vs. conventional Disadvantages Pilot testing requirements Lot of steel internals maintenance Needs sludge inventory longer startup times Considerations Needs polymer effect on filterability Need to manage blowdown Susceptible to upset with temperature change 27

28 BALLASTED FLOCCULATION ACTIFLO Kruger Actiflo Traditional Kruger Actiflo Turbo 28

29 BALLASTED FLOCCULATION High rate ballasted flocculation clarifier (15 30 gpm/sq.ft) Use of microsand to ballast flocs makes particles sink faster micron effective size (smaller sand tends to work better) Use of hydrocyclones microsand recovery from the sludge Dilute solids 15 Years of installed experience over 120 US installations 29

30 BALLASTED FLOCCULATION 30

31 BALLASTED FLOCCULATION Coagulation (Flash Mix) Injection (Flash Mix) Maturation (Flocculation) Settling (20 gpm/sf): : Total Detention Time 1-2 minutes 1-2 minutes 4-6 minutes 2 minutes 8-12 minutes 31

32 BALLASTED FLOCCULATION Advantages Small footprint area Quick response to adjustments Potential $ savings vs. conventional Disadvantages Higher power consumption Pilot testing requirements Low solids content in sludge More process elements to control and optimize Considerations Needs polymer effect on filterability Sand is consumed (loss) ~ 8 lbs/mg Sand pumps/piping need special design 32

33 DISSOLVED AIR FLOTATION Reaction Zone Float Separation Zone Sludge Weir Aerated Layer Waste Solids Baffle Clarified Layer Effluent Collection Compressor Saturated Recycle Receiver Air Saturator Recycle Pump Recycle 33

34 DISSOLVED AIR FLOTATION Float solids instead of settle Primarily for low turbidity/low solids applications Excellent for algae removal (algae likes to float) and waters with thermal variation Options Conventional (2 5 gpm/ft 2 ) Stacked DAF Filtration (4 6 gpm/ft 2 ) High Rate DAF (6 20 gpm/ft 2 ) 34

35 DISSOLVED AIR FLOTATION 35

36 DAF DESIGN PARAMETERS Recycle stream pressure: psi Flocculation time: 5 20 minutes Flotation zone detention time 5 15 Minutes Surface Loading Rate: 2 6 gpm/ft 2 High rate: 6 20 gpm/ft 2 36

37 DISSOLVED AIR FLOTATION Advantages Small footprint area Generally not polymer dependent (less likely to reduce filter runs) Ideal for light solids High sludge solids concentration (2 5%) w/mechanical scraping Disadvantages High power costs Pilot testing requirements Considerations Definition of loading rates (basin area, recycle) Raw water DO Sludge transport w/mechanical scraping Heavy solids can create difficulties 37

38 COMPARISON OF TECHNOLOGIES 38

39 COMPARISON OF ALTERNATIVE CLARIFICATION PROCESSES Each case needs to be evaluated on its own individual circumstances Water quality Treatment goals Regulations Existing infrastructure/personnel Space availability Cost sensitivity So let s look at some examples No space limitations Warm weather/water 39

40 SPACE/VOLUME RELATES TO CONCRETE Conventional 31,500 sq ft Plates 9,600 sq ft DAF 6,000 sq ft Actiflo 4,000 sq ft 40

41 EVALUATION OF DIFFERENTIAL CAPITAL COSTS (24 MGD WTP) $6,000,000 $5,000,000 $4,000,000 $3,000,000 Equipment Cost Concrete $2,000,000 $1,000,000 $0 Conv Plates DAF Actiflo Concrete matters but equipment does too 41

42 EVALUATION OF OPERATING COSTS, EXCLUDING LABOR (24 MGD WTP) $80,000 $70,000 $60,000 $50,000 $40,000 $30,000 $20,000 Additional Polymer Microsand Electrical Cost ($.10/kWh) $10,000 $0 Conv Plates DAF Actiflo Power is a major variable to consider 42

43 COMPARISON OF TECHNOLOGIES SUMMARY Many choices for high rate sedimentation Available for new plants, retrofits Selection is site specific based on Water source Existing facilities Space availability Enhanced coagulation needs/dbp reduction Weather Cost Pilot testing may be needed Include filtration Effective coagulation still critical 43

44 PROJECT EXAMPLES 44

45 EWEB Hayden Bridge Water Treatment Plant 45

46 EWEB Contact Basin No. 2 (of 3) 46

47 EWEB Contact Basin No. 3 (of 3) 47

48 UNITED WATER 20 mgd Lake DeForest WTP Retrofit Clarkstown, New York 48

49 InsightH2O High-Rate Clarification Alternatives 26 March 2013 INITIAL PROCESS FLOW DIAGRAM 49

50 InsightH2O High-Rate Clarification Alternatives 26 March 2013 REVISED PROCESS FLOW DIAGRAM 50

51 InsightH2O High-Rate Clarification Alternatives 26 March 2013 ORIGINAL SITE PLAN 10 MGD Sedimentation Flocculation Aerator Filter Building Control Building 51

52 InsightH2O High-Rate Clarification Alternatives 26 March 2013 REVISED SITE PLAN 20 MGD Sedimentation Flocculation DAF Control Building Filter Building 12 gpm/sf design 15 gpm/sf pilot tested and permitted Filters Rerated from 10 to 20 mgd 6,000 sq. ft. pre engineered building 52

53 BALLASTED FLOCCULATION PRETREATMENT AT THE CHANDLER, AZ PECOS WTP VICTORIA SHARP CITY OF CHANDLER CHANDLER PECOS WTP SUPERINTENDENT

54 PROJECT OVERVIEW 30 mgd Conventional 30 mgd Ballasted Flocculation 54

55 FWPS2 FWPS1 A HYBRID PLANT Conv Basin 1 Res 2 Res 1 Conv Basin 2 Presed Basins Filters 1-8 Filters 9-12 BF Basin 4 BF Basin 5 Conv Basin 3 RWPS1 RWPS2 Kept existing 30 mgd of conventional pretreatment. Added 30 mgd of new ballasted flocculation pretreatment. PROJECT OVERVIEW Operate both in parallel upstream of anthracite monomedia filters. Section Heading optional 55

56 WHY BALLASTED FLOCCULATION? PILOTING STUDY Resulted in longer filter runs. Less tendency for turbidity breakthrough. Much smaller footprint than conventional basins. Shorter detention times allowing changes in water quality to be apparent quicker. Positive feed back from the operations and maintenance group during a tour of the Passaic Valley Water Commission plant in New Jersey. 56

57 OPERATIONAL OBSERVATIONS Handles turbidity changes well. Changes in water quality show up in 20 minutes, rather than hours in a conventional basin. Uses more chemicals. Less sand is needed than was original assumed by operations. 57

58 30 mgd BF Basins 30 mgd Conventional Basins 58

59 PASSAIC VALLEY WATER COMMISSION 110 mgd Little Falls WTP Retrofit Clifton, New Jersey 59

60 InsightH2O High-Rate Clarification Alternatives 26 March 2013 LITTLE FALLS WTP PROCESS SEQUENCE Filter Building Existing Basins 3 & 4 Control Building Existing Basins 1 & 2 Existing Chemical Building 60

61 InsightH2O High-Rate Clarification Alternatives 26 March 2013 LITTLE FALLS WTP PROCESS SEQUENCE Filter Building Existing Basins 3 & 4 Control Building Existing Basins 1 & 2 New ACTIFLO Building Four Trains at 40 gpm/sf 61

62 InsightH2O High-Rate Clarification Alternatives 26 March 2013 LITTLE FALLS WTP PROCESS SEQUENCE Filter Building Residuals Storage New Chemical Storage Control Building New Ozone Facilities New ACTIFLO Building 3,600 ppd Ozone 3.5 mg/l dose 62

63 InsightH2O High-Rate Clarification Alternatives 26 March 2013 LITTLE FALLS WTP PROCESS SEQUENCE GAC Filter Building Residuals Storage New Chemical Storage Control Building New Ozone Facilities New ACTIFLO Building Converted from anthracite/sand to 42 GAC 63

64 CALIFORNIA WATER SERVICE COMPANY NE BAKERSFIELD, CA WTP PRETREATMENT

65 PROJECT DESCRIPTION CAPACITY: 22 MGD START UP: JUNE 2003 RAW WATER SOURCE KERN RIVER PREOXIDATION & COAGULATION TWO STAGE FLOCCULATION HIGH RATE SEDIMENTATION MEMBRANE FILTRATION

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67 KERN RIVER SOURCE DESCRIPTION NORMAL CONDITIONS TURBIDITY: 3 TO 6 NTU TOC: COLOR: EXTREME CONDITIONS TURBIDITY: NTU TOC: 6+ COLOR: 500+

68 PROCESS DESCRIPTION RAPID MIX TWO STAGE FLOCCULATION HIGH RATE CLARIFICATION PARKSON PLATE SETTLERS 0.32 GPM / SQ FT LOADING RATE TRACK GUIDED SLUDGE REMOVAL SYSTEM

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70 NORTH TEXAS MUNICIPAL WATER DISTRICT 900 mgd Wylie WTP Retrofit 70

71 InsightH2O High-Rate Clarification Alternatives 26 March 2013 NTMWD WYLIE WTP Plant III 328 mgd Plant IV 164 mgd Plant II 328 mgd Plant I 82 mgd 71

72 InsightH2O High-Rate Clarification Alternatives 26 March 2013 INTEGRATING OZONATION Ozone Contactors North Ozone Building South Ozone Building Ozone Contactors 72

73 InsightH2O High-Rate Clarification Alternatives REPLACED TWO OF EIGHT BASINS WITH PLATES 26 March 2013 Flocculation Plates Ozone Contactors Flumes Two basins of 41 mgd each 0.4 gpm/sf 73

74 QUESTIONS? 74

75 Black & Veatch 3 June 2014 CONTACT INFO Jeff Lindgren, P.E.*, P.L.S.** Engineering Manager Black & Veatch 5885 Meadows Rd, Suite 700 Lake Oswego, OR LindgrenJM@BV.com *Licensed in *OR, WA, & CA **OR 75

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