Genesee County Drain Commissioner
Water and Waste Services Division
District #3 Linden WWTP
Digester Improvements Project, Phase I
Joe Goergen, GCDC - WWS
Tom Grant, HRC
INTRODUCTION
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Hubbell, Roth and Clark is assisting the Genesee
County Drain Commissioner with improvements to the
digesters at the Linden WWTP.
The project includes:
 Adding vortex mixing equipment to two anaerobic
digesters
 Sludge and gas piping improvements
 Two new heat exchangers
 Replacement of existing air actuated diaphragm
pumps with new rotary lobe pumps.
FUNDING AND COSTS
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The approximate construction cost is $1.3 Million, which
is being funded with an MDNRE SRF loan and 40%
ARRA principal forgiveness.
Mr. Matt Raysin, P.E., Division Engineer and Mr. Joe
Goergen, Division Superintendent is overseeing the
construction for the County.
Also involved are Jeffrey Wright, Drain Commissioner,
and John F. O’Brien, P.E., Director of Water and Waste
Services.
Sorensen-Gross Construction Services is the General
Contractor.
DISTRICT #3, LINDEN WWTP
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Plant was originally constructed in 1963 and provides
influent pumping, primary settling, secondary treatment
(activated sludge) and settling, and UV disinfection prior
to discharge into the Shiawassee River.
Currently is rated for 11 MGD average flow and 16
MGD peak flow.
Solids handling facilities consist of anaerobic digesters
for primary sludge, sludge thickening via dissolved air
flotation (DAF) for secondary sludge, sludge storage
vaults, and a loading station for hauling sludge off-site
for land application and or landfill.
BACKGROUND, PHASE I
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Phase I Project Scope:
 Digesters:
 New vortex mixing
 Sludge and gas piping improvements
 Two new sludge-to-sludge heat exchangers
 Sludge pump replacements
 New instrumentation and controls
BACKGROUND, PHASE II
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Phase II Project Scope:
 Under consideration for increased energy efficiency
and utilization without adding maintenance demands
DIGESTER MIXING
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The existing Primary Digester No. 1 gas mixing
equipment did not efficiently mix the digester contents.
The existing Primary Digester No. 2 was not equipped
with any mixing.
The new vortex liquid mixing system improves the
digesters’ operational efficiency, resulting in increased
volatile solids destruction and gas generation.
The new system includes four jet nozzles and a
1,500 gpm centrifugal chopper pump at each digester.
VORTEX MIXING SYSTEM
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System selected was the Vaughan “Rotamix”
 Multiple fixed nozzles allow effective mixing energy
distribution without the need for rotating equipment.
 Can mix tanks after long periods of storage, and
allows intermittent operation, reducing energy costs
 Chopper pumps reduce clogging problems due to
fibrous material and other debris
 System operates without liquid level dependency
 No scheduled nozzle maintenance required, and no
rotating equipment within the process.
VORTEX MIXING SYSTEM
VORTEX MIXING SYSTEM
MIXING PUMP (CHOPPER)
TEMPERATURE MANAGEMENT
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The solids pumped from the Primary Clarifiers to the
Digester No. 1 caused heat loss and occasional upsets
due to the temperature differential.
Two new spiral heat exchangers now pre-warm the
solids for better efficiency.
Solids from Digester No. 1 pass through the heat
exchanger as they are pumped to Digester No. 2 to
warm the primary solids from the clarifiers.
A flow control valve is used to match the flow rates,
keeping the level in Digester No. 1 tank constant.
SPIRAL HEAT EXCHANGERS
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Project included two Alfa-Laval Spiral
Heat Exchangers, each 150 gpm
Utilizes a single channel that allows for
fully counter-current flow. Channels are
curved with uniform cross-section that
causes a spiraling motion within the fluid.
The spiraling motion keeps the fluid fully
turbulent, keeping solids in suspension
and produces a “self-cleaning” action.
Side cover opens to expose entire
surface.
Images from Alfa-Laval
HEAT EXCHANGERS
PUMP REPLACEMENT
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Existing air diaphragm
and “plunger” pumps
that were beyond useful
life were replaced with
rotary lobe pumps
Variable Frequency
Drives (VFDs) were also
added to some pumps
to allow for more
efficient operation
PROJECT COORDINATION
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Project required significant planning and support from
Plant personnel to ensure the day-to-day operation
would not be impacted by the construction.
ADDITIONAL PHOTOS
ADDITIONAL PHOTOS
ADDITIONAL PHOTOS
ADDITIONAL PHOTOS
ADDITIONAL PHOTOS
 Thank
you!!!
 Questions???