1. Evaluation of Filtration Technologies and Upgrade of the Filtration System at the Cadillac Wastewater Treatment Plant
Presenter: Walid Al-Ani, P.Eng, P.E., BCEE, LEED® AP Project Manager for Stantec Consulting Michigan Inc.

2. Presentation Overview
Overview of the Cadillac WWTP
Background Information
Filtration Technologies Evaluation & Selection
Design Highlights
Construction Highlights
Post-Construction Performance
Questions and Answers

3. Overview of the Cadillac WWTP
Plant Rated for 3.2 MGD Average Daily Flow and 4.5 MGD Maximum Daily Flow
Influent Pump Station – Screw Pumps
Equalization Basin
Preliminary Treatment
Primary Treatment
Secondary Treatment – Activated Sludge/Chemical Addition for Phosphorous Removal
Rotating Biological Contactors
Tertiary Filters
UV Disinfection
Anaerobic Digestion
Biosolids Land Application

4. Aerial View of the Cadillac WWTP

5. Background Information
Project plan prepared in 2006 to address overall plant needs – Requirement for seeking State Revolving Funds (SRF)
Tertiary Treatment major needs identified:
Replacement of the sand filters that were nearing the end of their useful life
Replacement of the sampling pumps
Replacement of the samplers
Design completed in the summer of 2007
Construction completed in the early spring of 2008
Overall construction cost approximately $3,800,000
Construction cost for Tertiary Treatment Improvements approximately $1,000,000
Construction cost for the installed filters approximately $620,000

6. Filtration System Before Implementing Improvements
Three sand filters (Hydroclear) commissioned in 1977
Some rehabilitation work performed over the years including replacement of filter media, valves, and control system
Deteriorating performance and extensive backwashing necessary

7. Filtration Technologies Preliminary Options
Traveling Bridge Filters
Traveling Hood Filters
Disc Cloth Media Filters
Synthetic Media Filters
Deep Sand Filters
Membrane Biological Reactors (MBRs)

8. Traveling Bridge Sand Filters
Continuous downflows, automatic backwash, low head, granular medium depth filter.
Filter bed is divided into independent filter cells.
Treated wastewater flows through the medium by gravity and exits to the clearwell plenum via a porous-plate, polyethylene underdrain.
Each filter cell is backwashed individually by an overhead traveling – bridge assembly, while the other cells remain in service.
During the backwash cycle, wastewater is filtered continuously through the cells that are not being backwashed.
Example is the US Filter Davco Products – Gravisand.

9. Traveling Bridge Sand Filters
Source Aqua-Aerobics Systems, Inc.

10. Traveling Hood Sand Filters
Similar to the Traveling Bridge Sand Filter.
Uses a pneumatically driven self – propelled hood instead of a conventional rail-mounted traveling bridge.
Simpler, more compact installation, lower equipment cost compared to the Traveling Bridge Sand Filter.
Example is EIMCO Water Technologies.

11. Traveling Hood Sand Filters
Source Water Online

12. Disc Cloth Media Filters
Filter tank contains a series of circular disk elements covered with a specialized cloth media.
The cloth media traps particulates within its interior as well as forming a particulate layer upon its outer surface.
Backwash cycle begins at a predetermined water level.
During the backwash cycle, the center tube rotates while a centrifugal pump draws filtered water through a suction header from the clean side of the filter cloth.
Examples are the Aqua-Aerobic Aqua Disks and the Kruger Hydrotech Disc Filter.

13. Disc Cloth Media Filters
Source Aqua-Aerobic Systems, Inc.

14. Synthetic Medium Filters
Filters use highly porous synthetic medium.
Porosity modified by compressing the filter medium.
Wastewater flows through medium; not around filtering medium as in conventional sand and anthracite filters.
Wastewater introduced in bottom of filter and flows upward through filter medium, which is retained by two porous plates.
Upper porous plate raised mechanically in backwash. Flow to filter continues and air introduced below lower porous plate causing medium to move in a rolling motion.
Example is Schreiber’s Fuzzy Filter.

15. Synthetic Medium Filters
Source: Schreiber
Source Schreiber

16. Deep Bed Upflow Continuous Backwash Sand Filters
Wastewater introduced into bottom of filter where it flows upward through a series of riser tubes.
Wastewater then flows upward through downward moving sand and exits filter.
Sand particles and trapped solids are drawn downward into the suction of an airlift pipe. A small volume of compressed air draws sand, solids, and water upward.
At the top of the airlift, the dirty slurry spills over into a central reject compartment. Sand settles and is cleaned further as it moves down through a washer.
Example is Parkson’s DynaSand Filter.

17. Deep Bed Upflow Continuous Backwash Sand Filters
Source: DynaSand
Source DynaSand

18. Membrane Biological Reactors (MBRs)
MBRs combine secondary & tertiary treatment into one process.
Integrated bioreactor uses membranes immersed in bioreactor; re-circulated MBR in which mixed liquid circulates through a membrane module located outside the bioreactor.
In the integrated bioreactor wastewater is drawn through the membranes using vacuum. Compressed air is used to scour the membrane surfaces.
In the re-circulated MBR wastewater is pumped into the membranes where solids are retained inside the membranes and wastewater passes through to the outside. The membranes are backwashed systematically to remove solids.
Examples are MBRs manufactured by Zenon, US Filter Memcor, and Envirogroup.

19. Membrane Biological Reactors (MBRs)
Source: Memcor

20. Evaluation of Filtration Technologies - Performance
Required performance based on NPDES effluent limitations for the summer months listed in the Cadillac WWTP permit:
30-Day Average BOD mg/L
30-Day Average TSS mg/L
30-Day Average Ammonia Nitrogen (N) 0.9 mg/L
30-Day Average Phosphorous mg/L
Evaluation of all technologies indicated that the effluent limitation for TSS could be met.

21. Evaluation of Filtration Technologies Cost
Filter Type
Budgetary Price *
Traveling Bridge Sand Filter
$200,000
Traveling Hood Sand Filter
$300,000
Disc Cloth Media Filter
$500,000
Synthetic Media Filter
$700,000
Deep Bed Sand Filter
$800,000
Membrane Biological Reactor
$2,400,000
* 2006 Prices – Based on equipment cost from manufacturers

22. Evaluation of Filtration Technologies Footprint and Required Modifications to Existing Facilities
Filter Type
Remarks
Traveling Bridge Sand Filter
Does not fit into the existing building.
Traveling Hood Sand Filter
Does not fit into the existing filter footprint but may fit into existing building with structural modifications.
Disc Cloth Media Filter
Fits into the existing filter footprint but requires removal of the mud well.
Synthetic Media Filter
Deep Bed Sand Filter
Membrane Biological Reactor

23. Evaluation of Filtration Technologies - Summary
Filter Type
Remarks
Warrants Further Consideration
Traveling Bridge Sand Filter
Does not fit into existing building No
Traveling Hood Sand Filter
Does fit into existing filters footprint
Disc Cloth Media Filter
Fits into existing filters footprint
Yes
Synthetic Media Filter
Deep Bed Sand Filter
Membrane Biological Reactor
Does not fit into existing building and is too costly

24. Evaluation of Filtration Technologies
Filter Type
Installations in MI and other Surrounding States as of early 2007
Remarks
Warrants Further Consideration
Disc Cloth Filter Media (Aqua – Aerobic)
Several nationwide including MI
Will not require pilot testing due to sufficient experience in MI
Site visit to Sutton Bay WWTP, MI
Conference call with Superintendent of Champagne Sanitary District WWTP
Yes
Disc Cloth Filter Media (Kruger)
One in MI one in Ravenna, OH
May require pilot testing due to limited experience in MI
Site visit to Ravenna WWTP, OH
Synthetic Media Filter (Schreiber)
One in MI
Likely to require pilot testing due to limited experience in MI and high loading rates due to small footprint No

25. Evaluation of Filtration Technologies
Item of Comparison
Cloth Media Disc Filter
(Aqua-Aerobic)
Cloth Media Disc Filter (Kruger)
Equipment Cost
$547,000
$500,000
Structural Modifications
Demolition of Mud Well
Columns and beams remain
Partial demolition of mud well
Significant concrete work required to accommodate open channel flows
Access Into Existing Building
Requires demolition of building exterior wall
Experience in Michigan
Several Installations
Pilot testing not required
One installation only as of early 2007
Pilot testing likely required
Experience at Similar Installations
Sutton Bay WWTP
In Operation since 2006
No Mechanical Problems
Good Workmanship
Urbana-Champagne Sanitary District WWTP
In Operation since 2005
Good responsiveness during construction, start-up, and post construction
Decision to install same type of filters at the larger District’s WWTP
Peak flows of 17 MGD were handled with no reported problems
Ravenna WWTP
Difficulty meeting the 2 MGD peak flow with one filter out of service
Belt supporting the discs has failed
Major rigging required for belt replacement

26. Final Selection of Filtration Technology
Decision was to adopt the cloth media filter technology (Aqua-Aerobic) based on the following:
Established experience nationwide including Michigan
Ease of Maintenance
Demonstrated ability to handle peak flows
Ability to meet the project’s strict milestones since no pilot testing would be required

27. Design Highlights Limitations
Limitations on when construction could occur had to be established, due to the NPDES Limitations
Higher SS discharge limits allowed December 1 through April 30 (30 lbs/day on a monthly basis compared to 20 lbs/day for rest of the year)
Therefore, taking the existing filters off-line and completing installation of the new filters was allowed for December 1 through April 1

28. Design Highlights Demolition Work
Structural integrity had to be confirmed to allow partial demolition of the walls and slab
Existing piping arrangement had to be confirmed to allow bypass of the filters to the disinfection process
Demolition of existing exterior walls had to be addressed to verify access issues

29. Design Highlights New Work
Hydraulic calculations had to be performed to ensure new filters would not be a bottleneck
Filters, piping, platforms, and controls had to be fitted into the existing space

30. Construction Highlights Challenges
Entire work (demolition, installation, start-up, on-line) had to be completed in three months

31. Construction Highlights Challenges
Access limited through existing building wall

32. Construction Highlights Demolition Work
Filters demolished and removed

33. Construction Highlights Demolition Work
All piping in gallery removed

34. Construction Highlights Demolition Work
“Mud Well” slab demolished

35. Construction Highlights New Work
New Floor

36. Construction Highlights New Work
Filter concrete support pads

37. Construction Highlights New Work
New filter piping

38. Construction Highlights New Work
Filters installed on concrete pads

39. Construction Highlights New Work
New piping in gallery

40. Operation and Controls Highlights
Filters in operation

41. Operation and Controls Highlights
Filter Control Panels

42. Operation and Controls Highlights
Backwash and Sludge Valves

43. Operation and Controls Highlights
Back Wash Cycle
Back Wash Initiation:
Water level exceeds specified level
Time interval elapses
Manual back wash cycle
High level float switch activates
Back Wash Set Points:
Back Wash interval, time between automatic backwash cycles
Back Wash duration, wash time for each collection manifold
Back Wash level, water level that triggers a back wash cycle
Sludge Cycle
Sludge Removal Initiation:
Time interval elapses
Back wash counts elapse
Manual sludge cycle
Sludge Cycle Set Points:
Sludge interval, time between automatic sludge cycles
Backwash count, number of back washes between automatic sludge cycles
Sludge duration, duration of the sludge cycle

44. Operation and Controls Highlights
Filters are operating successfully and meeting the NPDES requirements

45. Questions & Answers