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VLR® SYSTEM FOR BIOLOGICAL TREATMENT
FORT DODGE, IOWA WPCF
True simultaneous nitrification/denitrification allows nutrient removal using minimum energy in an efficient footprint
Economic development has its price and sometimes calls for major upgrades to a
community’s wastewater treatment facilities. In Fort Dodge, Iowa, that was the case
where expansion of new Cargill and CJ Bio America plants in a nearby industrial
park required additional capacity and BOD and TKN removal capabilities at the Fort
Dodge Water Pollution Control Facility (FDWPCF).
The two agricultural production plants added about 5 MGD flow to the FDWPCF
and increased BOD and TKN loadings by 100 to 300 percent, respectively.
To meet the new treatment requirements, Fort Dodge chose to expand the
biological treatment technology it had been using for several years—the Evoqua
VLR® System. Essentially an oxidation ditch tipped on its side, the system not
only saved on construction costs and footprint requirements when compared to
conventional treatment, it gave the Fort Dodge plant the ability to simultaneously
nitrify and denitrify.
“We selected VLR systems back in 1998 when we faced new ammonia limits,”
explains Mike Trotter of McClure Engineering Co., Fort Dodge, the design firm
on the project. “We decided to install suspended growth biological technology to
replace our old two-stage trickling filters.
“We looked at several biological processes, and the VLR systems offered more
flexibility,” he says, noting that the design team and the city were looking ahead to
anticipated nutrient removal requirements in the future.
Industry
Municipal Wastewater
Business Challenge
Industrial business development required
the city of Ft. Dodge, IA to increase
treatment capacity as well as improve BOD
and TKN removal.
Keys to Success
•
Increase treatment capacity to
meet an additional 5 MGD and
improve current and future nutrient
removal requirements
•
Provide a flexible biological treatment
process to improve operational
performance and control power usage
•
Meet a tight project deadline
to accommodate business
development needs
Two VLR systems were originally installed and a third has been added in the new
project, which also includes a new final clarifier, pumping stations, aerobic
digester, and blower and chemical building, plus rehabilitation of the existing
UV disinfection system.
The total project cost was $23 million to increase primary treatment capacity to
12.0 MGD and secondary treatment to 18.6 MGD. The schedule for the project
was very tight. McClure Engineering completed the plant design at the end of
2011. Bidding was completed in late 2012. Plant start-up was mid-2014. The
contractor was Gridor Construction of Buffalo, Minn. The plant is operated for
the city by US Water.
True simultaneous nitrification-denitrification
achieved through use of Evoqua VLR® System.
(McClure Engineering photo).
www.evoqua.com
VLR® SYSTEM
Each VLR system train includes four tanks. In the first two tanks, Envirex® disc
aerators provide mechanical aeration, which is closely controlled to create anoxic
conditions (zero dissolved oxygen) and maintain the desired ORP (oxidation
reduction potential). These aerated anoxic conditions facilitate true simultaneous
nitrification-denitrification in the same tank. In the third and fourth tanks, aerobic
conditions are maintained by disc speed, which is typically constant, and addition
of oxygen through course bubble diffusers. Contents from the fourth tank in each
VLR system are recycled to the first and second tanks to supplement total nitrogen
removal. Overall, up to 90-95 percent removal is achieved.
Trotter points to the flexibility of the process, noting that the plant can control power
usage on each of the three VLR systems, and can split, block or proportionately
distribute RAS according to wastewater characteristics and treatment objectives.
He says that normally, the plant operates at 2 mg/L DO out of the final tank, with
additional DO added as the water passes over the finger weirs in the UV system.
A new “smart” biological nutrient removal (BNR) control system, supplied by
Evoqua, uses DO and ORP monitors in each tank to control the operation of the
discs, blowers, and internal recycle pumps.
Results
•
Expansion of the existing VLR system
increased treatment capacity to
12.0 MGD for primary treatment and
18.6 MGD for secondary treatment
•
Able to achieve total nitrogen removal
up to 90-95 percent, with the
flexibility to distribute RAS based on
the wastewater characteristics and
treatment objectives
•
Expansion plans along with engineering
design and start-up occurred within a
24–36 month time period
Solutions/Services
Evoqua VLR® System.
For more information visit www.evoqua.com
and search for VLR.
Customer’s Primary Business:
DISC AERATORS
The Fort Dodge, Iowa WPCF serves more
than 25,000 residents and local businesses.
Customer Location
Fort Dodge, Iowa
COARSE BUBBLE
DIFFUSER GRID
HORIZONTAL BAFFLE
AIR RELEASE SYSTEM
Evoqua VLR® Systems provide treatment process flexibility to
achieve nutrient removal limits with less power and space.
READY FOR THE FUTURE
Trotter also notes that the VLR system installation will enable the plant to remove
phosphorus biologically (if required in the future) without having to add any more
tanks. At the moment, it’s not clear whether more production facilities will be
added to the industrial park, but if they are, the FDWPCF will be prepared. “The
VLR system is the best application for dealing with total nitrogen and phosphorus
limits in the future,” Trotter says.
4800 North Point Parkway, Suite 250, Alpharetta, GA 30022
+1 (866) 926-8420 (toll-free)
+1 (978) 614-7233 (toll)
www.evoqua.com
Envirex and VLR are trademarks of Evoqua, its subsidiaries or affiliates, in some countries.
All information presented herein is believed reliable and in accordance with accepted engineering practices. Evoqua makes no
warranties as to the completeness of this information. Users are responsible for evaluating individual product suitability for
specific applications. Evoqua assumes no liability whatsoever for any special, indirect or consequential damages arising from the
sale, resale or misuse of its products.
© 2014 Evoqua Water Technologies LLC
Subject to change without notice
BC-FORTDODGE-CS-0814

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