The Screw Press Advantage - Goodwyn | Mills | Cawood

THE
The official
magazine of
Alabama’s Water
Environment Association
VOLUME 35 • NO. 3 • FA LL 2014
THE
SCREW PRESS
ADVANTAGE
Address Service Requested
AWEA • 4700 Highway 69 North, Northport AL 35473
GADSDEN’S APPROACH
TO SOLIDS HANDLING
2015
BUYERS’
GUIDE
Inside:
Alabama’s Water Policy Update • Megan Lange Participates in SJWP • AWEA Scholarships
BOARD OF Directors
AWEA BOARD OF DIRECTORS
President
Brian Shannon
Garver Engineers
One Chase Corporate Center Ste 400
Birmingham, AL 35244
Phone: 205-313-6464
[email protected]
PWOD
Mike Lankford
Gadsden WW&SB
PO Box 800
Gadsden, AL 35902
Phone: 256-543-2884
[email protected]
Vice-President
Patrick Wootton
Nixon Power Solutions
1440 Lakes Parkway Ste 600
Lawrenceville, GA 30043
Phone: 770-448-6687
[email protected]
Executive Secretary
Kimberly Polifka
The Cassady Company, Inc.
4700 Highway 69 North
Northport, AL 35473
Phone: 205-330-0098
[email protected]
Treasurer
Wheeler Crook
Goodwyn, Mills & Cawood
2660 EastChase Lane Ste 200
Montgomery, AL 36117
Phone: 334-271-3200
[email protected]
Delegate
Matt Dunn
City of Auburn
1501 W Samford Avenue
Auburn, AL 36830
Phone: 334-703-8945
[email protected]
Secretary
Michael Sims
MAWSS
Post Office Box 2368
Mobile, AL 36652
Phone: 251-378-3503
[email protected]
Past President
Rob Coleman
Morrow Water Technologies, Inc.
7440 Cahaba Valley Road
Birmingham, AL 35242
Phone: 205-821-2511
[email protected]
2014 – 2015 AWEA Board Meeting Dates*
*All dates are tentative.
All board meetings are open to any AWEA member. What better way to stay informed about what’s happening at
YOUR AWEA? If you wish to attend or call in, please contact any Board Member. STAY INVOLVED, BE INFORMED!
8
Date
Time
Meeting
Date
Time
Meeting
October 21, 2014
10:00 AM
Regular Meeting
February 17, 2015
3:30 PM
Conference Call
10:00 AM
Regular Meeting
November 18, 2014
10:00 AM
Regular Meeting
March 17, 2015
December 16, 2014
3:30 PM
Conference Call
April 10 – 15, 2015
January 20, 2015
10:00 AM
Regular Meeting
THE
Wave | Fall 2014
2015 Annual Conference
THE SCREW PRESS
ADVANTAGE
EFFECTIVE ENGINEERING AND OPERATIONS
SOLUTIONS FOR GADSDEN’S SOLIDS HANDLING
BY: MIKE LANKFORD & WHEELER CROOK, P.E.
I
n the summer of 2009, the Gadsden
Water Works & Sewer Board (GWW&SB)
was evaluating its wastewater treatment
facilities and preparing to make some
big decisions about the future. The water
and sewer utility serves nearly 13,000
households, over 120 restaurants,
numerous commercial establishments,
and several industries. The City of
Gadsden is home to approximately
37,000 people, with the majority of the
populace served by the GWW&SB.
The collection system is composed of
more than 300 miles of sewer collection
piping and utilizes two (2) treatment
facilities. The treatment facilities,
known as the East River WWTP and
the West River WWTP, have treatment
capacities of 6.18 MGD and 11.32 MGD
respectively. One of several critical
components of their wastewater
facilities that required attention was its
solids handling process.
In the fall of 2009, the GWW&SB
began exploring options for wastewater
treatment due to several constraints. The
previous year, the Alabama Department
of Environmental Management (ADEM)
released the final Total Maximum Daily
Load (TMDL) for the Coosa River, including Neely Henry Lake, which is the water
body that runs along-side the City of
Gadsden. The TMDL addressed nutrient
levels in the basin and established a 30%
reduction to phosphorus loads into the
Coosa River. This reduction regulated
major point source dischargers to a numeric, total phosphorus limitation of 1 mg/L
during the growing season. GWW&SB
considered the possibility of regionalized wastewater treatment to reduce the
burden on others in Etowah County, while
also evaluating the available life remaining
in its process equipment and structures.
The assessment of the wastewater
treatment facilities’ infrastructure, along
with the TMDL, forced the GWW&SB
into further evaluation of processes for
solids handling that would meet the existing and future needs of the POTWs. The
GWW&SB made the decision to maintain
its existing trickling filter process and utilize chemical precipitation for seasonal
phosphorus removal. The decision came
after beneficial conversations with ADEM
regarding water quality in the Coosa River
and the evaluation of other biological
processes that indicated significantly
higher operating expenses that were
not necessary to meet the water quality
requirements in the discharge stream.
The capital expense of biological treatment was also difficult to assume, thus
the operators and engineers focused on
making needed changes to the existing
process, which included screening, grit
removal, chemical precipitation, disinfection, and solids handling improvements.
The treatment facilities, constructed
in 1963, utilized numerous gravity drying
beds for solids dewatering. The initial
design provided beds sufficient for
the process, but the dependency on
weather plagued operators. The process
also consumed a sizeable portion of
the available land at the treatment sites.
Process calculations also indicated a
substantial increase in solids due to the
required chemical precipitation of phosphorus during the growing season.
While preparing for the phosphorus
limits in their NPDES permit, the GWW&SB
and Chief Operator, Randall Wood,
acknowledged that anaerobic digester
capacity would be critical. Maintenance in
the digesters and the experience with the
collection system indicated that the utility
would need to control its grit problems to
reduce the space that it was occupying
in the digesters. The GWW&SB decided
immediately upon review that the first step
toward improved solids handling was a
capital improvement project to improve
screening and reduce grit in the biological
process. The project bid in February of
2011 and was completed in March of
2012. The approximately $2.5 Million
project included Hydrodyne Engineering, Inc. Triden screens and Hydro International’s Eutek grit removal system at
both of GWW&SB’s wastewater facilities.
This phase I of the wastewater treatment
plant improvements enabled operators to
more efficiently operate the digesters and
reduce the inert and trashy materials in
the sludge.
Alabama’s Water Environment Association
| www.awea-al.com
17
With the headworks being renovated
to reduce inert solids, the GWW&SB
concentrated on Phase II of its wastewater improvements - the phosphorus
removal and the sludge handling necessary to meet the compliance schedule
granted by ADEM.
Jar testing revealed that the most
beneficial and cost effective way for the
two POTW’s to remove phosphorus
during the growing season is chemical
precipitation using aluminum sulfate
(alum) as a coagulant. Engineers moved
forward in developing a design for chemical feed and precipitation. During this
design, the GWW&SB, including Randall
Wood and Superintendent of Environmental Services, Mike Lankford, evaluated
various sludge dewatering processes and
equipment. All of the typical dewatering
methods were reviewed by GWW&SB
operators, staff, and engineers. Belt filter
presses, centrifuges and screw presses
were evaluated for their effectiveness in
dewatering, their operational characteristics, rate of sludge production, and their
costs both capital and life-cycle.
The GWW&SB team was familiar with
belt filter presses, as several sites were
toured. The typical belt presses yielded
20-22% dry solids. The systems are
known for their forgiving nature when
treating sludge with debris. The systems
are user friendly such that good operators are able to troubleshoot problems
and make repairs. However, they also
have numerous bearings that must be
maintained along with the belt and other
guides and rollers. These dewatering
mechanisms are not enclosed, and from
a housekeeping standpoint, these systems are the least clean.
Centrifuges from multiple manufacturers were piloted by the GWW&SB team.
These units all performed very well and
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Technical Support
Testing
Polymers
Microbiological Control
Epa Approved Products
BOILER AND COOLING WATER
INDUSTRIAL & MUNICIPAL WASTEWATER
Langelier and Ryzner Index Calculations
Corrosion Coupon Studies
Fouling Determinations
Energy and Water Saving Recommendations
Inspections of Towers
Sludge Dewatering
Suspended Solids/Bod Control
Operator Training
Dechlorination Service
Algae Control
Phone: 225-654-4955 - 800-762-9104 • Fax: 225-654-9533
PO Box 181 Zachary, LA 70791-0181
Contacts: David Thornton ([email protected]) | Randy Bush ([email protected]) | David Oliver ([email protected])
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18
THE
Wave | Fall 2014
similarly. The typical centrifuge yielded dry
sludge solids between 27% and 33%. Due
to the units’ susceptibility to trash in the
sludge, the units required a grinder/macerator prior to dewatering. The centrifuges
piloted rotated at speeds upwards of 3,500
RPM and required total horsepower of 50
to 120 for the volumes of sludge predicted
for dewatering. A high-pitched noise of the
fast rotating internals of the centrifuges
was present, but the machines are relatively clean and contained.
Next, the GWW&SB team evaluated and piloted a couple of dewatering
devices new to the municipal market – the
screw press. Both of the piloted screw
presses worked exceptionally well and
were extremely efficient. The typical dry
solids produced were between 25% and
34%. The units required macerators for
protection of the equipment, yet were
more forgiving than the centrifuges in this
respect. The screw press units rotated
between 0.7-2.3 RPM, and required a total
horsepower of less than 7.5. The screw
press was unusually quiet, as well as very
contained and clean.
After months of analysis, discussion
with engineers, site visits, and pilots, the
GWW&SB team determined that the
dewatering equipment that best met the
needs of the POTW was the screw press.
The screw press provided the necessary
solids yield, consumed the least amount
of power and was estimated to be the
most economical capital expenditure.
The pilot produced an average capture
rate of 96.5% with Gadsden’s sludge, and
capture rate improved with increased
polymer consumption. Thus, the staff and
the engineers were able to determine
the optimal settings to produce consistently high results. The capture rate of 96%
could be produced with a polymer consumption rate of between 16 and 21 lbs.
active/ton of dry solids.
The Huber Screw Press, in particular, became the basis of design for
GWW&SB’s dewatering facilities due to
its relatively small size, clean features and
robust stainless steel design. Each POTW
was to be fitted with a combined sludge
dewatering and control building, which
would house the two required Huber
Screw Presses, with additional space
for future expansion as warranted. The
footprint of the designs required approximately 60% of the existing drying beds be
demolished for construction purposes,
which posed a temporary sludge handling problem.
The expected construction time for the
Phase II improvements to the POTW was
greater than 12 months. Thus, the staff
knew that temporary sludge handling
would be difficult with limited drying beds
and the potential for wet weather. The first
option considered was liquid hauling. The
projected cost for liquid hauling exceeded
$25,000 per month and equated to over
$375,000 for sludge handling for both
facilities through the construction period.
The second option considered for temporary dewatering was the rental of dewatering equipment during construction for
GWW&SB staff to operate. The sludge
would then be disposed at the landfill, as
it had prior to construction. Equipment
rental had a projected cost of $15,000 per
month, plus landfill tipping fees and polymer use. Furthermore, the staff would be
required to rent and operate two such belt
presses, one for each POTW.
While meeting the demands of
temporary sludge handling, these two
options were not favorable due to their
high costs and low reward. None of the
monies spent on these options would be
spent on capital investment for the future.
Another option had to be available!
After much consideration, a new
idea was conceived by the GWW&SB.
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Alabama’s Water Environment Association
| www.awea-al.com
19
Frank Eskridge, the staff contacted
Goodywn, Mills & Cawood, Huber USA,
and Pump & Process with a proposal to
pre-purchase two (2) screw presses and
have them installed in a shipping container
for temporary sludge dewatering. The
plan was solid, as all of the necessary
components, including the feed pump,
pneumatic controls, electric control
panels and accessories fit in the footprint
of the temporary container. The screw
presses could be utilized for temporary
sludge dewatering, then removed and
mounted for permanent installation upon
the completion of the dewatering building.
The temporary screw press units
would need several simple components for startup at each prospective site:
power, polymer, liquid sludge from the
digester, discharge for filtrate, and access
for dewatered sludge removal. With the
known requirements for setup of the units,
the GWW&SB staff knew exactly where to
locate the temporary units to provide the
necessary components. The temporary
sites not only supplied the units with the
power, sludge and other necessary components, but also allowed construction
accessibility for the contractor that would
be on site.
Bid documents, inclusive of the temporary storage units, were put together
20
THE
Wave | Fall 2014
and advertised for bidding. The Huber
Rotamat® Model 440, configured in an
intermodal shipping container, was submitted and approved. The Huber screw
presses arrived, one at each POTW, in their
respective shipping containers, with all
of the specified equipment pre-installed.
The two ends of the shipping containers
opened fully to allow access for operators
and for conveyance of the solids into a
transportable container for disposal.
The GWW&SB staff also found another
major cost savings for the temporary
dewatering system with the polymer
system. A more costly polymer system
was recommended for the temporary
installations, as it was proven in the field
with pilot testing and existing installations.
Gadsden was willing to take a calculated
risk based upon their knowledge of polymers and chemical systems. The project team was already proceeding in an
unprecedented manner by using permanent equipment in the temporary application. GWW&SB staff used their knowledge
and operations expertise to design and
build temporary polymer systems for
much less, including the day tank, pumps,
and accessories. A system costing less
than $1,000 was put together for polymer
dosing, and the screw press units were
delivered, set up and ready to operate!
After temporary installation, the screw
presses averaged flow rates of 25-30 GPM
with solids of 3.5-5.0% of anaerobically
digested sludge. The resulting dry solids
yield was 28-34% during the 4-7 hour run
times, five days per week. The presses are
designed for 1,000 pounds of solids per
hour. However, the GWW&SB, knowing
that they must understand the limits of the
equipment, have pushed 50 GPM of ~ 4%
solids through the press with results of up
to 26% dry solids. The equipment should
not be designed for these conditions, but
extreme conditions must always be considered by engineers and operators.
In the extended 465 day construction
time of the Phase II improvements projects,
the temporary screw press installations
provided an excellent method for dewatering solids. The operators and engineers
also gained confidence in the equipment,
as the construction period provided an
excellent long-term, training activity. In the
spring of 2014, the Huber equipment was
moved to its final and permanent location
in a shared building space with treatment
plant operations and controls. The permanent installation of the dewatering equipment at both POTWs was performed by
Max Foote Construction Company and
included the Huber Screw Presses, Acrison
polymer feed systems, Netzsch rotary lobe
feed pumps, Kaesar duplex compressors,
and a Huber conveyor system.
Prior to the installation of the dewatering
equipment in its temporary and permanent
locations, GWW&SB was often unable
to keep up with the demands of sludge
production and dewatering using its conventional drying beds due to inclement
weather and its effects on the operation.
The Huber screw presses have enabled
the utility to continuously sustain dewatering operations along with the sludge production. The notable feat is the ability of the
project to meet these needs on a temporary basis using the permanent equipment.
As Superintendent of Environmental
Services, Mike Lankford stated, “Sometimes thinking outside the box means putting something inside the box.” x