presenter: walid al-ani, p.eng, p.e., bcee, leed® ap project manager for stantec consulting...
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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.
Overview of the Cadillac WWTP
Background Information
Filtration Technologies Evaluation &
Selection
Design Highlights
Construction Highlights
Post-Construction Performance
Questions and Answers
2
Presentation Overview
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 Application3
Overview of the Cadillac WWTP
4
Aerial View of the Cadillac WWTP
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
5
Background Information
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
6
Filtration System Before Implementing Improvements
Filtration Technologies Preliminary Options
Traveling Bridge Filters
Traveling Hood Filters
Disc Cloth Media Filters
Synthetic Media Filters
Deep Sand Filters
Membrane Biological Reactors
(MBRs)
7
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.8
Traveling Bridge Sand Filters
9
Source Aqua-Aerobics Systems, Inc.
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.
10
Traveling Hood Sand Filters
11
Source Water Online
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.
12
Disc Cloth Media Filters
13
Source Aqua-Aerobic Systems, Inc.
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.
14
Synthetic Medium Filters
15
Source SchreiberSource: 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
Required performance based on NPDES effluent limitations for the summer months listed in the Cadillac WWTP permit:◦ 30-Day Average BOD5 7 mg/L◦ 30-Day Average TSS 20 mg/L◦ 30-Day Average Ammonia Nitrogen (N) 0.9 mg/L◦ 30-Day Average Phosphorous 0.5 mg/L
• Evaluation of all technologies indicated that the effluent limitation for TSS could be met.
20
Evaluation of Filtration Technologies - Performance
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
21
Evaluation of Filtration Technologies
Cost
* 2006 Prices – Based on equipment cost from manufacturers
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 Fits into the existing filter footprint but requires removal of the mud well.
Deep Bed Sand Filter Does not fit into the existing building.
Membrane Biological Reactor Does not fit into the existing filter footprint but may fit into existing building with structural modifications. 22
Evaluation of Filtration Technologies Footprint and Required Modifications to
Existing Facilities
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
No
Disc Cloth Media Filter Fits into existing filters footprint
Yes
Synthetic Media Filter Fits into existing filters footprint
Yes
Deep Bed Sand Filter Does not fit into existing building
No
Membrane Biological Reactor
Does not fit into existing building and is too costly
No
23
Evaluation of Filtration Technologies - Summary
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
Yes
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
24
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 •Columns and beams remain•Significant concrete work required to accommodate open channel flows
Access Into Existing Building
•Requires demolition of building exterior wall
•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
25
Evaluation of Filtration Technologies
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
26
Final Selection of Filtration Technology
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
27
Design Highlights Limitations
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 28
Design Highlights Demolition 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
29
Design Highlights New Work
Entire work (demolition, installation, start-up, on-line) had to be completed in three months
30
Construction Highlights Challenges
Access limited through existing building wall
31
Construction Highlights Challenges
Filters demolished and removed
32
Construction Highlights Demolition Work
All piping in gallery removed
33
Construction Highlights Demolition Work
“Mud Well” slab demolished
34
Construction Highlights Demolition Work
New Floor
35
Construction Highlights New Work
Filter concrete support pads
36
Construction Highlights New Work
New filter piping
37
Construction Highlights New Work
Filters installed on concrete pads
38
Construction Highlights New Work
New piping in gallery
39
Construction Highlights New Work
Filters in operation
40
Operation and Controls Highlights
Filter Control Panels
41
Operation and Controls Highlights
Backwash and Sludge Valves
42
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
43
Operation and Controls Highlights
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
Filters are operating successfully and meeting the NPDES requirements
44
Operation and Controls Highlights
45
Questions & Answers
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