Presented by: Brent Bode, P.E., Tetra Tech, Inc. Low Energy, Non Shear WAS Thickening Alternatives and Design for Grand Rapids, MI WWTP

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1 Presented by: Brent Bode, P.E., Tetra Tech, Inc. Low Energy, Non Shear WAS Thickening Alternatives and Design for Grand Rapids, MI WWTP

2 PRESENTATION AGENDA Project Background and Goals for GR WWTP WAS Thickening Preliminary Design Evaluation, Technology Selection Pilot Testing and Performance Expectation Design Features Construction

3 City s Clean Water Management Secondary Treatment with UV Disinfection Two Parallel Processes Referred to as North and South Plants Secondary Treatment Capacity of 90 MGD South Secondary Upgraded in 2005 North Secondary Upgrade Almost Complete Recent Improvements Include Aeration, Bio-P removal, Clarifier Upgrades WAS Thickening Improvement the Next Secondary System Upgrade

4 Biosolids Management Program Un-thickened WAS Co-settled with Primary Primary/Secondary Pumped to Holding Tank at GVRBA Facility Combined Biosolids to Dewatering Dewatered Cake to Landfill

5 Grand Rapids WAS Handling History Existing Thickening was done by Centrifuges Centrifuge Technology from Mid-90 s 2 units w/ 200 hp Drives and 40 hp Back Drives Abandoned Operation to Save Energy Co-settled WAS in Primary Tanks

6 Program Goals Replace Existing 200 HP Centrifuge Thickeners Utilize Low Energy Technology Minimize O&M Requirements Unattended Operation Improve Pumping Hydraulics of TWAS Capitalize on Process Benefits for WAS Thickening

7 Benefits of WAS Thickening Reduced Volume of Biosolids to Dewatering Eliminate WAS Solids Load to Primary Treatment Improved Dewatering with Thicker Feed Sludge Reduced Polymer Use for Dewatering Reduce Odor Potential for Primary Treatment Energy Reduction for Sludge Pumping

8 Why No/Low Shear Technology? City Mandate Based on Experience Thickened WAS Characteristics Concern Better Integration with Subsequent Dewatering Process Synergy with Polymer Use Between Thickening and Dewatering TWAS Pumping Concerns

9 Existing Facility Challenges Compact Building Footprint Proximity of WAS Building to Dewatering Facility Transfer Pumping Distance for TWAS Existing Piping System for TWAS Pumping Transfer of Centrifuge TWAS was Difficult Existing Transfer Pump Capability Limited

10 Thickened WAS Transfer Route

11 PRELIMINARY DESIGN EVALUATION

12 Basis of Design for WAS Thickening Improvements Design Condition Current Day Design Average Day Design Max Day Flow (gpm) Solids (Dry lbs/day) Solids (Dry lbs/hr) ,160 1,800 1,000 54,040 2,250 1,200 64,550 2,690

13 WAS Thickening Performance Requirements Installed Capacity to Process 1,200 GPM Raw WAS at 0.5% Solids Thickened WAS Range of 4% to 6% Max Multiple Thickener Units for Process Redundancy Design Parameter Influent WAS Solids (0.5%) Influent WAS Flow (GPM) Thickened WAS Flow (GPM) Design Average Design Max Day ,

14 City s Preferred Approach Fit New Equipment to Existing Building Installed Capacity to Match Peak WAS Design Production Achieve Substantial Energy Reduction for WAS Thickening Improve Transfer Pumping Capability Minimize O&M Examine Technology Options for Low Energy- Low Shear Select Technology with Best Fit for Goals

15 Low Energy, Low Shear Technology Options Gravity Belt Thickener Rotary Fan Press Rotary Screen Disk Thickener Rotary Drum Thickener Volute/Screw Thickener

16 Gravity Belt Thickener

17 Rotary Fan Press

18 Rotary Screen

19 Disk Thickener

20 Rotary Drum Thickener

21 Volute/Screw Thickener

22 Workshop to Select Preferred Technology City Experience and Research Engineering Team Experience Vendor Community and Site Specific Proposals Developed Consensus Regarding Two(2) Competing Technologies Rotary Drum (RDT) and Volute/Screw Thickener (VT) Testing, Evaluation, Research Followed

23 Rotary Drum Technology Standard Unit Configuration Thickened WAS Discharge

24 Volute/Screw Technology Screw Press Type Process Unique Dewatering Drum Design Dewatering Drum Comprised of Fixed and Moving Rings Around a Screw Conveyor Conveyor can Achieve Either Thickening or Dewatering Introduced by PWTech to US Market in 2008

25 Dewatering Drum Components Fixed Rings Held with Rods to Form Cylinder Internal Screw Conveyor Moving Rings Between Each Fixed Ring Water Drains Between Gaps

26 Drum Assembly

27 Multiple Drum Assembly Sections

28 Dewatering Drum End Plate

29 Sludge Conditioning Configuration 2-stage flocculation tanks Adjustable mixing energy Independent of flow Visual flocculation performance Adjustable VFD driven mixers

30 Preventative Maintenance Weekly - Check unit performance Monthly - Inspection of motors, pumps, sensors For Dewatering Applications - Replace moving rings in the dewatering section of the dewatering drum casing every 10,000-15,000 hours For Thickener Applications- No required maintenance for 30,000-50,000 hours

31 PILOT TESTING FOR SITE PERFORMANCE VALIDATION

32 Testing Considerations Representative WAS Source for Testing Utilize RAS Active Channel Secondary Influent Channel Return TWAS, Filtrate

33 Rotary Drum Thickener Site Test

34 Volute/Screw Site Test

35 Thickener Performance Expectation Type of Thickener Rotary Drum Volute Screw Unit Capacity Full Scale Model Solids Loading Rate (lbs/hr) 400 gpm 450 gpm 1,000 1,125 Hp per Unit Flush Water Rate 60 gpm 30 gal/hr Solids Capture Rate 93% 99% Max Thickening 5% 7% Polymer Usage 18 lbs/dry ton 18 lbs/dry ton Unit Dimensions 6'x22'-9" 6'x13'-9" Cost per Unit $275,000 $280,000

36 Present Worth Analysis Cost Item Rotary Drum Thickener Volute Thickener Equipment $ 885,000 $ 834,300 Installation $ 32,750 $125,145 Mechanical and Electrical (20%) $ 203,550 $191,890 General Overhead (8%) $ 97,700 $ 92,110 Contingencies (15%) $ 197,850 $ 186,520 Total Capital $1,517,000 $ 1,430,000 Total Present Worth of Annual O&M $6,200,932 $5,463,009 Total Present Worth of Thickener $7,717,932 $6,893,010

37 Equipment Layout ROTARY DRUM THICKENER LAYOUT VOLUTE THICKENER LAYOUT

38 Preferred Technology Selection Capital Cost Similar for Competing Technologies Polymer/Power Costs Similar No Major Maintenance Difference Water Consumption Big Difference Operational Cost Edge for Volute/Screw City Team Consensus for Volute Technology Smaller Footprint, Much Lower Water Use Validate Choice with Site Visits

39 Field Visit Validation Journey to New York Three Facility Locations Unattended Operations Very Clean and Reliable Performance Observed Team Consensus Validated

40 DESIGN

41 Volute/Screw Thickener Design Basis Parameter Design Basis Number of Units 3 Peak Feed Rate per Unit 450 GPM Influent Solids Concentration 0.5% Maximum Discharge Concentration 5.0% Solids Loading Capacity 1,125 lbs/hr Polymer Range lbs/dry ton solids Solids Capture Efficiency 98%

42 Thickened WAS Pumping Considerations Transfer Distance 1,500 Feet Existing Piping System, Not Direct Line Previously Experienced Pumping Difficulty at 5% Increased Pump Discharge Pressure Design Pressure to Pipe Rating of 125 PSI 5% TWAS Transfer Max, 4% Average Rotary Lobe Pumps Selected

43 Polymer Feed System Emulsion Polymer Planned as Same for Dewatering Dedicated Feed for Each Thickener Supply/Integration by Thickener Manufacturer

44 Process Schematic

45 Floor Plan Layout

46 Section Layout Drawing

47 WAS Building Under Construction Main Thickener Process Lower Level Pump Room

48 New Volute/Screw Thickener Unit Three Stage Screw Configuration, Ready to Ship

49 Performance of New System How does it perform? Manufacturer Responsible for Process Performance System Responsibility for Component Integration

50 Summary Eliminated Co-Settling WAS with Primary Selected Volute/Screw Thickener Technology Low Energy Solution Low O&M Consistent Thickened Product Process Will Provide Return on Investment

51 Questions?