Learn how the City of Asheboro is meeting government regulations, reducing power consumption, saving on chemical cost by using the proper instrumentation equipment. This leads to real-time data, better monitoring and control methods, cost savings and more for the city.

1. The presentation that follows was given during
Carotek’s Fifth Annual Process Solutions Summit in
Charlotte NC September 24 – 25, 2014.
Used with Permission.

2. Adapting to Change
with Instrumentation
Michael R.
Wiseman
Plant Manager

3. Asheboro WWTP
 Rated for 9 MGD
 Extended aeration (Schreiber System)
 BOD limit 5mg/l : 10mg/l
 NH3 limit 2mg/l : 4mg/l
 Monitor only for total N and Phosphorus
 2010 AWWA NC Central Region O&M
award winner
 2010 (John Stake) & 2013 (Chris
Schadt) NC Operator of the year award
winners
 TPO magazine article in 9/2014 issue

4. What is instrumentation and can
it help me?
 Sensors, transmitters, PLCs, VFDs and
SCADA that are used to monitor and/or
operate your system.
 Evaluate your application.
 What do you want to look at?
 What do you want to do with new
information?
 Do you need to plan for upgrades or
expansion?
 How precise does info have to be?
 How much can you spend?
 Who is going to install and wire?
 Who is going to maintain equipment?

5. Changes Effecting Asheboro
From 2005 to Present
 Major industrial users shut down
 Went from 70% industrial to 70% domestic
 Lost 3 MGD in daily average flow
 Plant Manager Retires after 30 years
 Press Filtrate disrupting aeration basins
 High solids and NH3 in effluent
 Permit Renewal in 2011, in 2016
 Detention Time too long through plant
 Diurnal Flow
 Shrinking Budgets!!!

6. Press Filtrate
 2 Ashbrook 1.5M Belt Presses
 Filtrate NH3 >200 mg/l
 Influent flow has been cut in half
 Diurnal flow
 Batch feeding creating slug loads
 Filtrate piped to only go to head of the
plant

7. Press Building

8. Primary #7

9. Bypass Pump

10. Primary Splitter Box

11. Filtrate Feed Pump

12. Associated Instrumentation

13. Tied to PLC communicating with
SCADA

14. Instrumentation Used and
Why
 VFD, Flow Meter, PLC, SCADA
 VFD added to control pump
speed/flow
 Meter installed to be able to adjust
flow accurately based on diurnal flow
and tank level.
 PLC and SCADA used to monitor
process with the option to automate
later

15. Results
 We have control of press filtrate
 No more slug loads
 No more huge spikes in air demand
from aeration basins
 Air demand goes down, so does
power bill !
 NH3 is fed at a slow constant rate
 Chemical usage down, not needed as
much for pH control… Saving Money!

16. Aeration Basins
 2011 Permit requires us to monitor
total Nitrogen and Total Phosphorus.
 We have been promised that 2016
Permit will have Total N and Total P
limits.
 In 2010 we started evaluating our
system to see how much we could
reduce these parameters with existing
equipment.

17. What we are working with

18. What we found out
 Our existing equipment is capable of
removing total N and Total P
 It has to have some help
 Current system performs Nitrification only
(NH3 NO2 NO3)
 Now we need to perform Denitrification
(NO3 N )
 In order to do this we have to turn the air off
and add a carbon source
 If you leave air off an additional 30 minutes,
phosphorus will also be consumed(luxury
uptake)

19. What we did
 We obtained a carbon source from a
local cereal manufacturer (sugar
water)
 Air on for 2 hrs/ air off for 2 hrs
 Before Total N avg was 20mg/l, After
it is 5mg/l
 Before total P avg was 1.0mg/l, After
it is 0.2mg/l
 Lowest Total N 2.8mg/l, Total P
.07mg/l

20. Process Control
 Purchased a 12,000 gallon tank, 2
tanker trailers, feed pump, coriolis flow
meter, nitrate sensor, and ammonium
sensor.
 Added a new card and programming
to PLC , updated SCADA to reflect
changes

21. pH Sensor

22. Dissolved Oxygen sensor

23. Nitrate, Ammonium, and pH
sensors

24. Sugar Water Feed Room

25. Sugar Water Tanks

26. Blowers

27. Air Gauges

28. PLC

29. SCADA

30. Historical Trending-NO3 &
NH4

31. D.O. in Aeration Tanks 1 & 2

32. SW Feed Pump, Flow, and
Brix

33. Results
 Successfully converted to BNR, close
to meeting expected permit limits
 Air on for only 12 hrs instead of 24
hrs, huge savings
 Saving in chemical costs because
denitrification process recovers pH
and alkalinity
 We know what is happening in real
time and can react accordingly

34. Future Changes
 Lift Station Flow Meters
 More accurate control of Aeration Basins
 Thermophylic Digestion
 Class “A” biolsolids
 Feed grease, fats, and oils directly to
digester. Also excess sugar water.
 Increase methane production
 Use methane to fuel generator, which will
supply power for entire plant.
 Zero carbon footprint??
 Endless possibilities for sensors and
instrumentation for monitoring and control

35. Pros and Cons of
Instrumentation
 Pros
 Real-time data
 Monitoring
 Control
 Automation
 Historical Trending
 Wireless
Technology
 Money Savings!
 Cons
 Cost Money
 Perform
maintenance
 Keep calibrated
 Suspect to
lightning?
 Keeping system
tuned
 Makes Lazy
Operators??

36. Questions ?