Increasing Energy Efficiency
at the Allegan WWTP
MWEA/AWWA Joint
Annual Conference
August 19, 2010
Project Background



Current treatment plant built in
the early 70’s
Headworks, manual 1 ½” bar
screen, grit removal system has
not been operation for 25 years.
Freezing at headworks during
winter months.
Project Background



Aeration basin 2 inoperable due
to failed air header, failing air
header and extensive weed
growth the in grit and sludge in
basin.
Fine bubble diffuser in aeration
basins and underground sludge
storage tank added in 1992
Aeration basin 3 and clarifier
added in 1995 for addition BOD
capacity.
Project Background





(3) 150Hp Hoffman blowers for
3 aeration basins.
No auto controls on blowers to
track D.O.
Blowers and motors were in
needed new bearings.
Aeration basin 3 utilized
existing blower designed for
basin 1/3 its size.
(2) 75hp centrifugal blowers
were used on the aerobic
digester, no timer or automated
controls.
Project Background



Centrifugal wasting pumps held
together with wooden wedges,
pumped 50gpm above rated
capacity.
Centrifugal sludge transfer
pumps were unable to move
thickened sludge over 3%
solids.
Significant Industrial flow from
Perrigo Corporation with no
pretreatment other than pH
adjustment.
Project Goals/Constraints



Rehabilitate/replace existing process equipment
Modify/improve activated sludge process to
improve performance, increase efficiency and add
organic treatment capacity for Perrigo
Accomplish improvements on existing site which
is surrounded by floodplain, old municipal dump
and Rockwell Superfund site (utilize existing
tankage or build structures primarily above
grade).
Aeration Energy Efficiencies
Diffusers
1.

Replaced fine bubble
diffusers with new,
more efficient diffusers
in aeration basins 1
and 2.
Aeration Energy Efficiencies

Energy Savings from Diffuser Replacement
Aeration Energy Efficiencies

Energy Savings from Diffuser Replacement
Aeration Energy Efficiencies

Energy Savings from Diffuser Replacement
Aeration Energy Efficiencies
Sensors
2.

Dissolved oxygen sensors were installed at the
end of aeration tanks 1 and 2 to provide
automatic feedback/control of blower inlet
valves based on operator set D.O. control
point.
Aeration Energy Efficiencies

Energy Savings from Automatic Blower Control

Savings of just over $5,000/yr for every 10 HP reduced
Design Point: 114 HP
Operating Point: 70 HP
Aeration Energy Efficiencies
3. Biological Nitrogen Removal



If nitrification is occurring in the aeration basins,
nitrates (NO3) can be returned to the anoxic zone (no
or low dissolved oxygen).
Bugs utilize oxygen in nitrates.
Nitrogen (N2) is released as a gas and oxygen needs
are reduced in aeration basin.
Aeration Energy Efficiencies


Basin configuration made
returning nitrates very
simple, and anoxic zone
was already in place due
to new divider wall.
External carbon source is
sometimes required (in
addition to raw sewage)
for de-nitrification
reaction to be optimal.
Aeration Energy Efficiencies


We may not optimize this
process, just get some
added benefit at a low upfront cost.
After system is more fully
loaded will test BNR
process to determine if
further optimization is
desired.
Septage/Treatment Energy Efficiency




Mix septage in aerated
tank with waste-activated
sludge.
Pump contents to sludge
storage tank.
Decant from sludge tank
back to liquid end of plant
is treated in liquid process.
Load to the aeration
system is reduced due to
less flow and lower
organic loading.
Septage/Treatment Energy Efficiency

Energy Savings from Septage Treatment System



Sludge Decant: 140 mg/l CBOD
Septage: 4,550 mg/l CBOD
Estimated Annual Septage: 3,000,000 gallons
Miscellaneous Efficiencies


Biological phosphorus
removal system results in
less sludge produced (less
chemical deliveries).
Automatic flow control
system for high flows
routes flows to either the
EQ tank or aeration tank 3
(standby tank) to maintain
treatment efficiency of
main treatment tanks.
Miscellaneous Efficiencies

New Headworks



¼” automatic fine screen
Self-cleaning wet well
High efficiency grit removal
Miscellaneous Efficiencies


New clarifiers with energy
dissipating influent well and
stamford baffles
New RAS pumps with
VFDs
Miscellaneous Efficiencies

Replaced gaseous
chlorine disinfection
system with Ultraviolet
Disinfection (no more
chlorine gas or sodium
bisulfite deliveries).
Building Systems Efficiencies


New natural gas fed Pulse Boiler
Indoor lighting




Replaced all fluorescent bulbs (T12 to T8)
Occupancy sensors installed in new areas of building
Option to control multiple bulbs in each fixture
Outdoor lighting

Replace mercury vapor lights with 2 stage induction
lighting with motion detector (10 pole mounted
fixtures)
Treatment Results

Average effluent results:




Septage receiving:




CBOD: 8 mg/l
SS: 17 mg/l
T. Phos. .6 mg/l
250,000 gallons per month
CBOD: 4,500 mg/l
SS: 20,000 mg/l
Decant from aerated
sludge storage:


CBOD: 140 mg/l
SS: 218 mg/l
Operational Efficiencies

New SCADA system provides full automation of plant






Automatic sludge wasting
Automatic sludge pumping
PD Sludge Blower control
UV control pacing
Automated headworks (fine screen control, grit collection, raw
sewage pumps)
Personnel requirements



More duties (e.g. septage operation), less personnel
1990’s: total of 5 staff
Present: total of 3 (possibly 4) staff
Original POTW Found


The wastewater plant that
was built in the 1930’s was
located during construction.
It was supposed to have been
removed and filled.
Increasing Energy Efficiency
at the Allegan WWTP
MWEA/AWWA Joint
Annual Conference
August 19, 2010