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Evaluation of Filtration Technologies and Upgrade of the Filtration System at the Cadillac Wastewater Treatment Plant

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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. Presentation Overview. Overview of the Cadillac WWTP

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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.

presentation overview
Presentation Overview
  • Overview of the Cadillac WWTP
  • Background Information
  • Filtration Technologies Evaluation & Selection
  • Design Highlights
  • Construction Highlights
  • Post-Construction Performance
  • Questions and Answers
overview of the cadillac wwtp
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
background information
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
filtration system before implementing improvements
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
filtration technologies preliminary options
Filtration Technologies Preliminary Options
  • Traveling Bridge Filters
  • Traveling Hood Filters
  • Disc Cloth Media Filters
  • Synthetic Media Filters
  • Deep Sand Filters
  • Membrane Biological Reactors (MBRs)
traveling bridge sand filters
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.
traveling bridge sand filters9
Traveling Bridge Sand Filters

Source Aqua-Aerobics Systems, Inc.

traveling hood sand filters
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.
traveling hood sand filters11
Traveling Hood Sand Filters

Source Water Online

disc cloth media filters
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.
disc cloth media filters13
Disc Cloth Media Filters

Source Aqua-Aerobic Systems, Inc.

synthetic medium filters
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.
synthetic medium filters15
Synthetic Medium Filters

Source Schreiber

Source: Schreiber

deep bed upflow continuous backwash sand filters
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’sDynaSandFilter.
membrane biological reactors mbrs
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.
evaluation of filtration technologies performance
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 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.
evaluation of filtration technologies cost
Evaluation of Filtration Technologies Cost
  • * 2006 Prices – Based on equipment cost from manufacturers
final selection of filtration technology
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
design highlights limitations
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
design highlights demolition work
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
design highlights new work
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
construction highlights challenges
Construction Highlights Challenges
  • Entire work (demolition, installation, start-up, on-line) had to be completed in three months
construction highlights challenges31
Construction Highlights Challenges
  • Access limited through existing building wall
construction highlights demolition work
Construction Highlights Demolition Work
  • Filters demolished and removed
construction highlights demolition work33
Construction Highlights Demolition Work
  • All piping in gallery removed
construction highlights demolition work34
Construction Highlights Demolition Work
  • “Mud Well” slab demolished
construction highlights new work36
Construction Highlights New Work
  • Filter concrete support pads
construction highlights new work38
Construction Highlights New Work
  • Filters installed on concrete pads
operation and controls highlights42
Operation and Controls Highlights
  • Backwash and Sludge Valves
operation and controls highlights43
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
operation and controls highlights44
Operation and Controls Highlights
  • Filters are operating successfully and meeting the NPDES requirements