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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

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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

  • Background Information

  • Filtration Technologies Evaluation & Selection

  • Design Highlights

  • Construction Highlights

  • Post-Construction Performance

  • Questions and Answers

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

Aerial View of the Cadillac WWTP

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

  • 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

  • Traveling Bridge Filters

  • Traveling Hood Filters

  • Disc Cloth Media Filters

  • Synthetic Media Filters

  • Deep Sand Filters

  • Membrane Biological Reactors (MBRs)

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 Filters

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.

Traveling Hood Sand Filters

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.

Disc Cloth Media Filters

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.

Synthetic Medium Filters

Source Schreiber

Source: Schreiber

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.

Deep Bed Upflow Continuous Backwash Sand Filters

Source: DynaSand

Source DynaSand

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.

Membrane Biological Reactors (MBRs)

Source: Memcor

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

  • * 2006 Prices – Based on equipment cost from manufacturers

Evaluation of Filtration Technologies Footprint and Required Modifications to Existing Facilities

Evaluation of Filtration Technologies - Summary

Evaluation of Filtration Technologies

Evaluation of Filtration Technologies

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

  • 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

  • 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

  • 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

  • Entire work (demolition, installation, start-up, on-line) had to be completed in three months

Construction Highlights Challenges

  • Access limited through existing building wall

Construction Highlights Demolition Work

  • Filters demolished and removed

Construction Highlights Demolition Work

  • All piping in gallery removed

Construction Highlights Demolition Work

  • “Mud Well” slab demolished

Construction Highlights New Work

  • New Floor

Construction Highlights New Work

  • Filter concrete support pads

Construction Highlights New Work

  • New filter piping

Construction Highlights New Work

  • Filters installed on concrete pads

Construction Highlights New Work

  • New piping in gallery

Operation and Controls Highlights

  • Filters in operation

Operation and Controls Highlights

  • Filter Control Panels

Operation and Controls Highlights

  • Backwash and Sludge Valves

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 Highlights

  • Filters are operating successfully and meeting the NPDES requirements

Questions & Answers

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