United States
tPkrhwlBI Environmental Protection
§ % Agency
Office of Water
EPA 820-F-20-003
June 2020
KENTUCKY OPERATORS TAKE THE LEAD IN REDUCING NUTRIENTS
Model results provide a framework for better performance
When the Kentucky Division of Compliance Assistance said
the EPA wanted to help the Lawrenceburg Sewage Treatment
Plant (STP) reduce nutrient pollution while saving energy,
Superintendent Mitch Hudson was a little skeptical. "We had
already had two energy audits, mainly looking at equipment
upgrades. Most of those recommendations were either impossible
from an operational standpoint or came with a 20-year payback.
We maybe had low expectations, but we decided to give it a fair
shake."
In 2017, Hudson and the chief operator, Jason Ransdell,
participated in a pilot partnership targeting low- or no-cost
operational changes to improve nutrient removal and save energy.
Hudson and Ransdell worked with the project team to model
ILawrenceburg's 3.3 MGD Orbal ditch process with a free tool
called Bio-Tiger, developed by Dr. Larry Moore at the University
of Memphis. The Bio-Tiger model uses readily available treatment
parameters and equipment information to develop a steady-state
model and estimate potential energy savings. The model showed
that aerators in the ditch supplied about 20% excess oxygen and
inhibited denitrification. Hudson and Ransdell experimented with
idling one 75-horsepower and two 25-horsepower aerators up to
24 hours/day to lower the dissolved oxygen (DO) concentration in
the basin.
It was not a new idea, Ransdell says, but the discussion helped
move things forward. "There are those ideas where you wonder
'what would happen if...' but are hesitant to try. Being able to talk
to someone like Dr. Moore who has that depth of knowledge gave
us some leeway to experiment."
Two years later, that experiment has paid big dividends. Effluent
total nitrogen (TN) concentrations are down 63%. The three
aerators remain mostly turned off, even with a 25% increase in
BOD loading. This saved about $25,000/year. Lawrenceburg also
discharges 39% less phosphorus and alum demand dropped with
the new protocol, saving Lawrenceburg $4,500/year.
Lawrenceburg STP
Parameter
Before
Optimization
August 2018-
July 2019
Effluent TN (mg/L)
11
4
Effluent Nil. (mg/L)
0.2
0.4
Effluent TP (mg/L)
1.1
0.67
Changes in average effluent total phosphorus at the
Lawrenceburg POTW after optimizations
1.1 mg/L
0.7 mg/L 0.7 mg/L
5/2015
to
4/2016
5/2016
to
4/2017
5/2017
to
4/2018
5/2018
to
4/2019
5/2019
to
4/2020
L
J
Before Optimization
L
J
After Optimization
The changes were simple, but Hudson says, "You need to have the
'want-to' kind of attitude. This work represents you." The "want-to"
attitude is in abundance at plants around Kentucky. At Princeton
STP's 1.57 MGD oxidation ditch plant, the Bio-Tiger model showed
potential to improve denitrification. William Brown, the chief
operator, shut off all rotors in all three ditches for eight hours each
night and ran one of two rotors in each ditch the rest of the day.
Effluent TN has decreased 55%, while effluent total phosphorus
(TP) has decreased by 9% without additional chemicals. Princeton
has also reduced electricity usage by 13%,
mm
National Study of Nutrient Removal and Secondary Technologies
Nutrient removal through optimizing plant operations

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m
Brown says the project has changed the culture at the plant.
"I've turned into my dad, running around and shutting off
lights," he says. He credits his superintendent, James Noel,
for trusting him to get the job done. "He's given me the
latitude to make changes and run the diagnostics I need to
get the best from the plant."
Princeton STP
Parameter
Before
Optimization
August 2018-
July 2019
Effluent TN ( mg/L)
22
9.7
Effluent NH, (mg/L)
0.4
0.3
Effluent TP (mg/L)
0.76
0.69
Changes in average effluent total nitrogen amount at the
Princeton POTW after optimizations
Average:
180 Ibs/d
Average:
90 Ibs/d
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXJ
1/2017 7/2017 1/2018 7/2018 1/2019 7/2019
J L
Before Optimization
After Optimization
In Greenville, superintendent Gary Russ and his team eliminate
excess aeration and create anoxic conditions in their 1.3 MGD
activated sludge system for a short time each day. Operators
shut down the blowers from 6 a.m. to 9 a.m. every weekday for
denitrification. The plant operates at high MLSS concentrations in
winter, and there were some initial concerns that suspended solids
would settle and clog the flexible membrane diffusers, but Russ
says it hasn't been a problem.
Since the new aeration schedule began in August 2018, effluent
IN concentrations have dropped 33% and electrical usage is down
13%. The average monthly electric bill has decreased from about
$4,700 to $3,850.
Greenville STP
Parameter
Before
Optimization
August 2018-
Juiy 2019
Effluent TN (mg/L)
15
10
Effluent NHj (mg/L)
0.3
0.3
mm


C3 1
Optimization Opportunities and Benefits
While every facility is unique, these three
plants aren't unusual in design. Many others
may have similar opportunities to save
energy and improve nutrient removal. Any
facility with excess treatment capacity, high
effluent nitrates, and an aeration system
that can operate intermittently or at reduced power
might be a candidate for optimizing treatment processes.
These three plants might see future growth that would
require their aerators to run more, which could reduce
the long- term benefits of these optimization efforts. For
now, though, their operators are using their ingenuity to
pursue what is possible—and reaping the rewards.
Summary of Results
STP
Annual
Energy Cost
Savings
TN
Reduced
By
TP
Reduced
By
Lawrenceburg
$25,000
63%
39%
Princeton
$23,000
55%
33%
Greenville
$10,000
33%
N/A
Acknowledgements
This factsheet was prepared in collaboration with EPA's Brendan Heid and is an adaptation of the article "Piiot Partnership for Optimization Pays
Off" published by Clean Water Professionals of Kentucky and Tennessee in the December 2019 issue of Streamlines.

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