Welcome to the May Edition of the 2021 M&R Seminar Series
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Welcome to the May Edition of the 2021 M&R Seminar Series
NOTES FOR SEMINAR ATTENDEES • All attendees’ audio lines have been muted to minimize background noise. • A question and answer session will follow the presentation. • Please use the “Chat” feature to ask a question via text to “All Panelists”. • The presentation slides will be posted on the MWRD website after the seminar. • The ISPE has approved this seminar for one PDH, and the IEPA has approved this seminar for one TCH. Certificates will only be issued to participants who attend the entire presentation.
Belinda Sue McSwain Sturm, Ph.D.
Associate Vice Chancellor for Research
Professor of Civil, Environmental & Architectural Engineering
The University of Kansas
Lawrence, Kansas
Dr. Belinda Sturm is a Professor in the Department of Civil,
Environmental & Architectural Engineering at the University of Kansas.
She also serves as an Associate Vice Chancellor for Research. Belinda
currently serves as Vice-Chair of the Water Environment Federation’s
Municipal Design Symposium and as Chair of the International Water
Association’s USA National Committee Executive Board. Belinda
earned her bachelor of science in Public Health from the University of
North Carolina at Chapel Hill and her Ph.D. in Civil Engineering and
Geological Sciences from the University of Notre Dame.
Recent Advances in Aerobic Granular Sludge Processes Belinda Sturm, PhD University of Kansas
Steady Progression of Design for Settleability
Selector zone concept
introduced to control
DO shown to impact
bulking
selection of filaments
(Choduba et al. 1973) SVI correlations for Selector zone design
versus flocs (Palm et al.
settling curves became became more formal Is aerobic granular
1980)
Filaments shown to more standardized sludge the natural
(Marten and Daigger,
dominate based on (Wahlberg and Keinath, 1997) and better evolution of good
bioreactor design and 1998; Daigger, 1995; understood (Martins et settling sludge
operation (Eikelboom, Ozinsky and Ekama, al, 2004) development?
1975) 1995)
WE&RF report on
Unified theory of filaments selector zone design
developed (Sezgin et al, guidelines (Gray et al,
1978) 2008)
1970s 1980s 1990s 2000s 2010s
2
Five decades of settling theory evolution has been summarized in
one key manual for operations
• Focus: settleability
• Select for good settling
•Low SVI
•Larger floc
•Limit filamentous growth
• Operating parameters
•SRT control
•F/M gradients
•Selector zones and plug flow
IWA Granule Workshop 2004
Granules making up aerobic granular
activated sludge are to be understood as
aggregates of microbial origin, which do not
coagulate under reduced hydrodynamic shear,
and which subsequently settle significantly
faster than activated sludge flocs.
• SVI30 < 60 mL/g
• SVI5 = SVI30 or SVI5 / SVI30 = 1
• Settling velocities > 9 m/hr
• Particle diameter > 200 µm
How Does Densified Activated Sludge Compare with
Granular Sludge?
Compact AS Densified AS Densified AS
(non-granular) (non-granular) (granular)
SVI30 80 to 120 mL/g SVI30 < 80 mL/g SVI30 < 50 mL/g
non-patented AS non-patented AS* AquaNEREDA™
Conventional Selector inDENSE™
Design
Different types of aerated granules have been formed
Parameter NIT OHO NDN-OHO NDN-PAO
Granules Granules Granules Granules*
Processes Nitrification COD oxidation Nitrification + Nitrification +
(low COD/N feed) (and possibly Denitrification Denitrification +
Nitrification) EBPR1
Feeding Aerobic Aerobic Anoxic Anaerobic
condition
Denitrifying N/A OHOs2 OHOs2 PAOs3 and GAOs4
bacteria
Nitrogen N/A Assimilation Sequential Simultaneous
removal method w/ limited anoxic and nitrification and
denitrification aerobic periods denitrification (SND)
in aerobic period
Demonstrated Lab-scale Lab-scale Lab-scale Lab- and Full-scale
1. EBPR – Enhanced biological phosphorus removal
2. OHOs – Ordinary heterotrophic organisms
3. PAOs – Phosphorus accumulating organisms
4. GAOs – Glycogen accumulating organisms – may also grow
Figdore, B.A., Stensel, H.D., Winkler, M.K.H., Neethling, J.B. (2017) Aerobic Granular Sludge for Biological Nutrient Removal.
Project No. NUTR5R14h. Water Environment and Reuse Foundation: Alexandria, VA.
Implementation of Aerobic Granular Sludge in Continuous Flow Activated Sludge (CFAS) Plants Aerobic granular sludge SBRs Conventional activated sludge • Sequencing batch operations • Continuous flow • High anaerobic F/M Ratio • Can have high anaerobic F/M with selector • Short settling time • No settling selection Image Copyright Royal HaskoningDHV Image Copyright King County
Densifying Activated Sludge Is Key to Increasing Capacity at WRRFs
Lawrence WWTP
Granular Sludge Pilot (70 L)
Flocculent Sludge Granular Sludge
– 5 mins Settling – 5 mins Settling
WERF U1R14 Project Flocculent Sludge Granular Sludge
– 30 mins Settling – 30 mins SettlingLawrence WWTP AGS Pilot Results - ( - K × X TSS )
Settling Parameters
VS = V0 × e
14
100% GS y = 19.4e-0.000413x SVI = 56 mL/g
12
70% GS, 30% FS y = 17.6e
-0.000397x
SVI = 63 mL/g
Initial Settling Velocity (m/h)
10
8
50% GS, 50% FS y = 15.1e-0.000395x SVI = 61 mL/g
6 -0.000471x
25% GS, 75% FS y = 12.6e SVI = 80 mL/g
4
100% FS y = 9.8e-0.000459x SVI = 100 mL/g
2
0
0 2000 4000 6000 8000 10000 12000 14000
MLSS Concentration (mg/L)
100%GS 100%FS 25%GS,75%FS 50%FS,50%GS
70%GS,30%FS Expon. (100%GS) Expon. (100%FS) Expon. (25%GS,75%FS)
Expon. (50%FS,50%GS) Expon. (70%GS,30%FS)Flux Curves for different levels of granulation
500
450
400
350
Flux (kg/m2/d)
300
250
200
150
100
50
0
0 2000 4000 6000 8000 10000
MLSS Concentration (mg/L)
100% FSFlux Curves for different levels of granulation
500
450
400
350
Flux (kg/m2/d)
300
250
200
150
100
50
0
0 2000 4000 6000 8000 10000
MLSS Concentration (mg/L)
100% FS 50% GS,50% FSFlux Curves for different levels of granulation
500
450
400
350
Flux (kg/m2/d)
300
250
200
150
100
50
0
0 2000 4000 6000 8000 10000
MLSS Concentration (mg/L)
100% GS 100% FS 50% GS,50% FSClarifier Capacity Modeling
Performed by Dr. José Jimenez
and Dr. Alonso Griborio
Note: Modeling assumed equal biomass
concentrations for all ratiosSludge Densification extends the same principles we learned from preventing bulking sludge
Five decades of settling theory evolution has been summarized in
one key manual for operations
• Focus: settleability
• Select for good settling
•Low SVI
•Larger floc
•Limit filamentous growth
• Operating parameters
•SRT control
•F/M gradients
•Selector zones and plug flowFloc Selection Theory and Filament Out-Selection
What are our key parameters for selecting for good settling
activated sludge?
300
SSVI3.5 , mL/g
200
100
N = 101
0
0 10 20 30 40 50
Number of Equivalent Tanks, N
From E. J. Tomlinson and B. Chambers, The effect of
longitudinal mixing on the settleability of activated
sludge. Technical Report TR 122, Water Research
Centre, Stevenage, England, 1978. Reprinted by
permission of the Water Research Centre.)
1. Plug Flow Conditions
Slide courtesy of Dr. Leon Downing,
Black & Veatch 18What are our key parameters for selecting for good settling
activated sludge?
300
SSVI3.5 , mL/g
200
100
N = 101
0
0 10 20 30 40 50
Number of Equivalent Tanks, N
From E. J. Tomlinson and B. Chambers, The effect of
longitudinal mixing on the settleability of activated
sludge. Technical Report TR 122, Water Research From Gray et al (2006) Develop and Demonstrate
Centre, Stevenage, England, 1978. Reprinted by Fundamental Basis for Selectors to Improve Activated
permission of the Water Research Centre.) Sludge Settleability
1. Plug Flow Conditions 2. Anaerobic/Anoxic feed
Slide courtesy of Dr. Leon Downing,
Black & Veatch 19What are our key parameters for selecting for good settling
activated sludge?
300
SSVI3.5 , mL/g
200
100
N = 101
0
0 10 20 30 40 50
Number of Equivalent Tanks, N
From E. J. Tomlinson and B. Chambers, The effect of
longitudinal mixing on the settleability of activated
sludge. Technical Report TR 122, Water Research From Gray et al (2006) Develop and Demonstrate From Sezgin et al (1978) A Unified theory of activated
Centre, Stevenage, England, 1978. Reprinted by Fundamental Basis for Selectors to Improve Activated sludge bulking, Journal of Water Pollution Control
permission of the Water Research Centre.) Sludge Settleability Federation 50(2)
1. Plug Flow Conditions 2. Anaerobic/Anoxic feed 3. Loading rate matters
Slide courtesy of Dr. Leon Downing,
Black & Veatch 20High F/M and Metabolic Selection
Decreasing substrate concentration
From Sezgin et al (1978) A Unified theory of activated sludge bulking, Journal of Water Pollution Control Federation 50(2)
Martins et al. (2003) Water Research 37, p.2555–2570
From Sezgin et al (1978) A Unified theory of activated sludge bulking, Journal of Water Pollution
Control Federation 50(2)A high F/M anaerobic feeding regime is important to drive
diffusion into granule and achieve metabolic selection
Contacting with high rbCOD drives diffusion to granule
interior Treated
effluent
displaced
-Allows interior to be biologically active
Anaerobic feeding selects for PAOs for EBPR
Slow upflow feeding widely used in lab and full-scale
Slow upflow
SBRs plug-flow feeding
through settled
sludge bed
Slug feeding has also been used in lab systems
Figdore, B.A., Stensel, H.D., Winkler, M.K.H., Neethling, J.B. (2017) Aerobic Granular Sludge for Biological Nutrient
Removal. Project No. NUTR5R14h. Water Environment and Reuse Foundation: Alexandria, VA.Substrate Utilization in SBR vs Plug Flow
rbCOD (mg/L)
Feeding Sludge Bed Height
Continuous Flow configuration with high F/M selector
Anaerobic
Selectors
Aerobic
Anx
rbCOD (mg/L)
HRT
23Effect of F/M on EPS Formation
Scale = 100 µm
Cells – Red Polysaccharides - Blue Proteins Green
McSwain et al. (2005). Applied and Environmental Microbiology, 71(2), 1051-1057.Effect of substrate utilization on EPS and granulation Jimenez (2015). Water research, 87, 476-482.
Sludge densification may utilize a combination of biological and physical selection mechanisms
WRF Study Purpose: Granule Application in
Continuous-Flow Systems
Granule selection
performed separate from
reactor and clarifier
Plug flow conditions
create necessary
substrate selectionLiquid-solids separation design must retain granules
Sludge feed
Favor retention of larger, faster-settling
granules over flocs Return
sludge
. . Screen
. .
Short settling timesWater Research Foundation Project Overview Particle Particle Selection Substrate Substrate Selection Cyclones installed at full-scale Selection & Settling Pilot Selection
WRF Study Purpose: Granule Application in
Continuous-Flow Systems
Granule selection
performed separate from
reactor and clarifier
Plug flow conditions
create necessary
substrate selectionPilot Studies Manipulating F/M with Wasting
Substrate Substrate &
Selection North South Particle
Only: Reactor Reactor
Selection:
A target F/M is Daily biomass
maintained by wasting is performed
wasting mixed liquor through a 0.2 mm
daily (both granules sieve, and granules
and flocs wasted) are retained
A mixture of granules Mainly granules are
and flocs are maintained in the
maintained in reactor reactorEffect of F/M on EPS and Granule Formation
230
0.30
210 0.28
Total EPS (mg COD / g VSS)
190 0.26
Ave Diameter (mm)
170 0.24
150 0.22
0.20
130
0.18
110
0.16
90
0.14
70
0.12
50 0.10
0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24
0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24
F/M (g rbCOD / g VSS-d) (3 day ave) F/M (g rbCOD / g VSS-d) (3 day ave)Effect of substrate utilization on EPS and granulation
200 0.5
Total EPS mg COD/g VSS
Mean diameter mm
0.4
150
0.3
100
0.2
50
0.1
0 0
0.13-0.15 0.15-0.20 0.20-0.25 0.25-0.30
Substrate utilization rate (g sCOD/g VSS-d)
EPS Mean diameterAnaerobic or Metabolic Selectors
230
210 Anaerobic F/M –
Total EPS (mg COD /
190 Assuming COD Uptake in First Selector Zone
170
g VSS)
150 250 90
Diam.
Diameter (um) / EPS (mg COD / g VSS)
130 80
110 200 70
90
60
70 EPS
SVI (mL/g)
150
50 50
0.10 0.15 0.20 0.25 40
F/M (g rbCOD / g VSS-d) (3 day ave) 100
30
SVI 20
50
10
0 0
< 5.20 5.20 - 5.94 5.94 - 6.68 6.68 - 7.42 > 7.42
rbCOD (mg/L)
F/M (g COD / g MLSS-d)
Series1 EPS (mg COD/g VSS) Series3
Feeding Sludge Bed HeightExperimental Plan Aug. 15, 2015 Mar. 25, 2016 to Mar. 25, 2016 to Oct. 1, 2016 Granule formation External selector and development implementation
Selective Wasting
Granule selection through
selective wasting of flocs Retained fraction
0.2 mm screen
Sludge Floc wasting
Granule retaining Wasted fractionPilot Studies Manipulating F/M with Wasting This graph shows the transition to mainly granule particles as the F/M > 0.21 Increasing F/M Floc à Granule transition
Impact of Selective Wasting on Sludge Structure
5.5 mg/L H2S found
in feed bucket
50 100
45 90
External selector
40 80
35 70
Ammonia Removal %
SRT fraction d
30 60
25 50
T n
u le S R et e n tio
ie r s r
20 40
G ran i t r i f
15 30 N
10 20
5 10
0 0
6
6
31 6
15 6
30 6
15 6
6
16 6
16 6
1
1
01
01
01
01
01
01
01
20
20
/2
/2
/2
/2
/2
/2
/2
1/
1/
17
4/
5/
3/
4/
5/
5/
6/
6/
7/
>0.2 mmImpact of Selective Wasting on Sludge Structure
4
Eff PO4-P
3.5
5-10L 15-20L
3
wasting wasting
2.5
Conc (mg/L)
2
1.5
1
0.5
0
16 16 16 01
6
01
6
01
6 16 01
6
20 20 20 /2 /2 /2 20 /2
1/ 1/ 0/ 0 0 9 9 / 9
3/1 3/3 4/2 5/1 5/3 6/1 7/ 7/2
Date (MM/DD/YY)
Granule retention PAOs accumulation and phosphate removal improvementMicrobial Community Selection through Wasting
Wasted fraction
Selectively Wasted
Selectively Retained
Retained fractionSubstrate Utilization in SBR vs Plug Flow
rbCOD (mg/L)
Feeding Sludge Bed Height
Continuous Flow configuration with high F/M selector
Anaerobic
Selectors
Aerobic
Anx
rbCOD (mg/L)
HRTSelection Factors Leading to Granule Growth at CFAS
HE1 80%
ID2 68%
HE2 62% F/M Ratio
ID1 51% 14
HW 35%
Puy1 29%
CrC 18%
7 Stage 1
CM 17%
ClC 15%
R2 = 0.72 Puy2 10%
WB 10% 0
Stage 2
SP 5.6% Stage 3
Dur 3.3%
Poc 1.3%
Kal 0.7%
BM 0.5%
SVI = Sludge 0.0 1.0 2.0 3.0 4.0
Volume Index Anaerobic Stage HRT (hr) 42Anaerobic or Metabolic Selectors
Anaerobic F/M – HE1 80%
ID2 68%
Assuming COD Uptake in First Selector Zone HE2 62% F/M Ratio
250 90 ID1 51% 14
Diameter (um) / EPS (mg COD / g VSS)
Diam. 80 HW 35%
200 70 Puy1 29%
CrC 18%
60
EPS 7 Stage 1
SVI (mL/g)
150 CM 17%
50
ClC 15%
40 Puy2 10%
100
30 WB 10% 0
Stage
50
SVI 20 SP 5.6% 2Stage 3
10 Dur 3.3%
Poc 1.3%
0 0
< 5.20 5.20 - 5.94 5.94 - 6.68 6.68 - 7.42 > 7.42 Kal 0.7%
BM 0.5%
F/M (g COD / g MLSS-d)
0.0 2.0 4.0
Series1 EPS (mg COD/g VSS) Series3
Anaerobic Stage HRT (hr)
Wei, S. P., Stensel, H. D., Nguyen Quoc, B., Stahl, D. A., Huang, X., Lee, P.-
H., Winkler, M-K.H., 2020. Flocs in disguise? High granule abundance found in
continuous-flow activated sludge treatment plants. Water ResearchSummary Metabolic selectors should be designed to achieve high rbCOD uptake rates, with virtually complete rbCOD removal An anaerobic F/M ratio greater than 5.2 gCOD/gVSS corresponded to higher EPS production; Anaerobic F/M greater than 7 has been associated with granulation Microorganisms subjected to high F/M may accumulate substrate as internal storage products It is possible to form granular sludge in continuous flow systems
Future Work As densification is achieved…. - How do existing clarifiers handle the additional solids loading rate? - Full-scale experience with fines will provide confidence - Implementation of hydrocyclones or screens to selectively waste flocs and retain granules has great potential - But operators need experience managing TWO sludge fractions separately
Administrative Experience
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