Presentation by Sacramento Regional WWTP engineers about $200,000 a year savings, improved Nocardia control and improved effluent quality by SRTmaster operation

1. Automating Control in
Biological Reactors for
Diurnal Loading
Joshua Nurmi, Jeremy Boyce, Mick Berklich
Sacramento Regional Wastewater Treatment Plant

2. Sacramento Regional Wastewater
Treatment Plant
•Came online in 1982 replacing 22 existing
wastewater treatment plants.
•Service area of more than 250 sq miles with
roughly 1.3 million residents.
•SRWTP treats approximately 150 MGD ADWF and
is capable of treating up to 400 MGD peak hour
flow.
•Plant effluent is discharged into the Sacramento
River.
•Largest Treatment Plant in Northern California

3. Dry Weather Influent Flow (MGD)
200
180
160
Influent Flow (MGD)
140
120
100
80
60
40
20
0
0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00
Wet Weather Influent Flow (MGD)
450
400
350
Influent Flow (MGD)
300
250
200
150
100
50
0
0:00:00 2:24:00 4:48:00 7:12:00 9:36:00 12:00:00 14:24:00 16:48:00 19:12:00 21:36:00 0:00:00
Time

4. Process
Overview
High Purity Oxygen
Secondary Treatment
Plant

5. Secondary Process
• High Purity Oxygen
Facility
• Carbonaceous Oxidation
Stage 4 Stage 3 Stage 2 Stage 1
T8
T7
(CO) Tanks T6
– 8 North Tanks, 4 South
T5
T4
South CO Deck Stage 1 Stage 2 Stage 3 Stage 4
T
12
• Secondary Clarifiers North CO Deck
T
T3
11
T
T2
10
T
– 24 total clarifiers
T1
9
SOI
NOI
• On-site oxygen generation PE1 PE2
facility

6. Secondary Wasting
• RAS Classifying Selectors
• Classifying Selector draws off surface flow from the
return activated sludge (RAS) stream prior to reentering
the COTs.
• Waste activated sludge (WAS) is conveyed to the
solids handling process by a dedicated set of variable
speed pumps.
• Mixed Liquor and Secondary Scum wasting
• Mixed liquor surface foam waste and SST scum tie into
waste lines downstream of WAS pumps.

7. Activated Sludge Control
• Previous Method
• Secondary Process was previously controlled by
regulating the amount of sludge wasted each day
based on a Mean Cell Residence Time target.
• Waste set point was only adjusted once per day, diurnal
loading was not taken into consideration.
• Grab samples unable to accurately represent
secondary process.
• Solids “snap shot” of solids inventory
• Taken by different operators each shift and from
day to day
• Some samples analyzed in lab, some in the field

8. Historical Annual MLSS
2,150
Daily MLSS Concentrations
1,950
1,750
TSS (mg/L)
1,550
1,350
1,150
950
750

9. Nocardiaform Problems
• SRWTP has historically been subject to
Nocardia blooms during warmer summer
months.
• Due to the design of the CO tanks Nocardia
can become entrapped on the water surface.
• Past studies have shown that the most
effective method for controlling Nocardioform
populations at SRWTP is to increase the food
to microorganism ratio (F/M) as influent
temperature increases.

10. Nocardioform Impacts
• Digester Impacts:
• Foam on digester covers
• Trash/Debris short circuiting digestion and
sent to SSBs
• Secondary Treatment Impacts:
• Pump shutdowns
• CO Tank overflows
• Excess suspended solids in the effluent

11. Study Objective
• Phase I: TSS Analyzer Field Test
– Purpose: Determine if total suspended solids analyzers
can provide accurate data to the SRT Control software
• Phase II: SRT Control
– Purpose: Use a stream of online data to adjust the
waste activated sludge set point in real time

12. Phase I: TSS Analyzer Field Test
• Investigate following parameters:
– Maintenance: minimum cleaning
and calibration requirements.
Optimum settings for self cleaning
systems.
– Accuracy: validate the relative
accuracy of the analyzers while
operating at optimal cleaning and
calibration intervals.
– Response Time: determine how
quickly the analyzers respond to
significant concentration changes.

13. Phase I: Conclusions
• Three of the four meters tested provide
accurate data when properly cleaned and
calibrated and adequately respond to sudden
process changes.
• When cleaned/calibrated 2x week the
analyzers consistently read within +/- 100 mg/l
for MLSS and +/- 300 mg/l for RAS.

14. Phase II: SRT Control Pilot
• Objective: Employ and evaluate an SRT
Control system to automate the activated
sludge flow.
• Benefits:Under steady state conditions
controlling SRT can control F/M which can
prevent:
• High F/M ratios: poor effluent quality
• Low F/M ratios: Nocardia, increased
aeration demand per pound destroyed

15. SRT Control Setup
• Five TSS Meters
• RAS, WAS and 3 MLSS Channels
• Flowmeters (8 total)
• 6 WAS Thickeners (existing), 2 WAS lines (new)
• New FMs needed to account for ML and scum
flows.
• SRT Master
• Takes values from all the flowmeters and
suspended solids meters and calculates a waste
set point (based on an SRT set point) every 15
minutes.

16. Average Daily SRT – Previous Control Method
2.5
2
SRT (Days)
1.5
1
0.5
0
Average Daily SRT - with SRT Control
2.5
2
SRT (Days)
1.5
1
0.5
0

17. Daily BOD F/M Ratio – Previous Control Method
3.5
3
2.5
2
F/M
1.5
1
0.5
0
Daily BOD F/M Ratio – with SRT Control
3.5
3
2.5
2
F/M
1.5
1
0.5
0

18. Daily Variations in F/M
90
80 78
F/M 2010 F/M 2008
70
60
51
Frequency (%)
50
40
33
30
20
20
12
10
2 3 2
0 0 0 0
0
0 0.2 0.4 0.6 0.8 1
Daily Swings in F/M

19. Intraday SRT – with previous control strategy
2.5
2
SRT (Days)
1.5
1
0.5
0
0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00
Time
Intraday SRT – with SRT Control
2.5
2
SRT (Days)
1.5
1
0.5
0
0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00
Time

20. Intraday F/M
1400 230
MLSS w/o SRT Control
210
1300 MLSS w/SRT Control
190
PE BOD Loading F/M1 F/M0
1200 170
Total Suspended Solids (mg/L)
PE BOD Loading (Klbs/day)
150
1100
Δ=10%
130
1000 110
90
900
70
800 50
0:00:00 4:48:00 9:36:00 14:24:00 19:12:00 0:00:00 4:48:00

21. Operational Performance
• Effluent Turbidity
• Nocardia Prevention
• Lessons Learned

22. Average Intraday Turbidity
12
Effluent Turbidity - SRT Control
10
Effluent Turbidity - Previous Control Method
8
Turbidity (NTU)
6
4
2
0
0:00:00 2:24:00 4:48:00 7:12:00 9:36:00 12:00:00 14:24:00 16:48:00 19:12:00 21:36:00 0:00:00
Time

23. Nocardia
6000
Pre-SRT Nocardia
Nocardia w/SRT Control
5000
4000
Nocardia Count (x1000)
3000
2000
1000
0
18-Nov 7-Jan 26-Feb 17-Apr 6-Jun 26-Jul 14-Sep 3-Nov 23-Dec 11-Feb
Date

24. SRT Pilot Test Conclusions
• Variability in daily average SRT and F/M
were decreased significantly.
• Intraday SRT is more stable with the
controller
• Secondary effluent quality less variable.
• Better Nocardia bloom control.

25. Lessons Learned
• Meter Problems
• All meters need to be monitored closely to ensure
that they are providing accurate data. Meter errors
(Primarily Flow) could cause the controller to over or
under calculate the wasting.
• High BOD loads
• In addition to variable diurnal loads the plant is
occasionally subject to high BOD loads. The SRT
controller does not directly measure BOD and the
high load will result in elevated F/M values.

26. Acknowledgments
• Alex Ekster, SRTMaster
• SRWTP Operations Staff
• Mike Mulkerin, SRCSD
• Glenn Bielefelt, SRCSD
• Steve Ramberg, SCRSD

27. Questions?

28. Cleaning/Calibration Frequency
Auto Days Between
Auto Cleaning
Test Cleaning Manual
Analyzer Frequency
Period Duration Cleaning/Calibra
(minutes)
(seconds) tion
Analyzer 1 (continuous) (continuous) 4
Period
Analyzer 3 30 15 4
1
Analyzer 4 30 15 4
Analyzer 1 (continuous) (continuous) 3
Period
Analyzer 3 30 10 3
2
Analyzer 1 30 10 4
Analyzer 1 n/a n/a 3
Period
Analyzer 3 30 30 3
3
Analyzer 4 30 30 3

29. 1400
Analyzer Accuracy
1300
1200
1100
TSS (mg/L)
1000
900
Sample
800
Analyzer 1
700 Analyzer 3
Analyzer 4
600
1 2 3 4 5 6 7 8 9 10 11 12
Days

30. MLSS Variability Comparison
180
160
140
120
Variability in MLSS (ppm)
100
+160 ppm
80
60
+80 ppm
40
20
0
Avg MLSS Range w/o SRT Control Avg MLSS Range w/SRT Control