POLYMER OPTI TIMI MIZA ZATI TION ON FO FOR R CWEA Seminar Math th,, Operatio perations ns,, and Maint ainte enanc nance e for Biosoli Bio solids ds Systems Systems September Septem ber 13, 201 2011 1
Steve Walker Senior Operations Specialist
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Lea Le arn rnin ing g Obj Obje ect ctiv ive es • Why optimize • Dewatering basics
• Polymer considerations • Sludge considerations • Optimization approach 2 / x t p p . 1 s 0 1 5 w s
•
u ng op m za on n ac on
Dewatering Sludg lu dge e Dewatering waterin g • The removal of a portion of the water contained in sludge b means of a filter ress centrifu e or other mechanism.
• The discipline of adjusting a process so as to optimize a set of parameters without violating a constraint • The most common goals are minimizing cost, maximizing throughput, and/or efficiency • The goal is to maximize one or more of the process paramrters, while keeping all others within their 3 / x t p p . 1 s 0 1 5 w s
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Polymer Costs
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Dewatering Polymer Costs $137,038 $130,014
$16,222
$15,701
$465,220 $206,715
$466,391
57% $1,911,634
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Liquid Oxygen
Ferric Chloride
DAF Polymer
Cent Polymer
SBS
SHC
Carbon
Chlorine
Polymer – Raw Material Costs 40
35
e g n a h C e g a t n e c r e P y l h t n o M
30
25
Producer Price Index for Plastics Material and Resins Manufacturin g Source: Bureau of Labor Statistics http://stats.bls.gov/ppi
20
Index incl udes: Propylene Ac rylo ni t ril e Epichlorhydrin Methyl acrylate Methyl meth acrylate Formaldehyde
15
10
5
0
Month
6 5 4
US No. 2 Diesel Retail Sales
3 2 1
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0 1/1/2001
1/1/2002
1/1/2003
1/1/2004
1/1/2005
1/1/2006 $/gal
1/1/2007
1/1/2008
1/1/2009
1/1/2010
1/1/2011
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Dewatering Considerations • Centrifuge components • Centrifuge adjustments
• Throughput • Sludge makeup
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Water in Sludge Gallons of Water in 10 tons of Sludge , 500,000 r t a400,000 W f o 300,000 s n o l l a200,000 G
Focus Area
100,000 0 1
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3
5
7
9
1 1
3 1
5 1
7 1
9 1
1 2
3 2
5 2
7 2
9 2
1 3
3 3
5 3
Centrifuge Components Bowl Weir Plates
Scroll
Sludge Feed
SIEBTECHNIK GmbH
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Liquid Discharge
Solids Discharge
Centrifuge Factors Bowl speed •
us e
roug
e
• The faster the speed, the greater the shear actor on occu ate s u ge • Can impact cake dryness, centrate quality, and polymer dose
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Centrifuge Factors Conveyor (scroll) speed
• Modern centrifuges are controlled using a • To obtain the desired torque, the PLC adjusts e scro spee • Can impact cake dryness, centrate quality, and polymer dose 3 1 / x t p p . 1 s 0 1 5 w s
Centrifuge Factors Differential
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•
e erence e ween scroll speed
e ow spee an
•
e erent a c anges as t e the desired torque
ac eves
e
Centrifuge Factors Weir depth • •
ec an ca a us men o p a es a the bowl ets t e poo
e en o
ept w t n t e ow
• Can impact cake dryness, centrate quality, and polymer dose
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Operational Targets Criteria
Units
Importance
Cake dryness
%TS
Disposal costs Water equals weight and takes up volume
or TSS, mg/L
Re-treatment of solids (thickening, digestion and dewatering) sludge mass calculations
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Throughput
Pounds per hour
How centrifuges are sized and sold
Polymer dose
Active
Operating costs
dry ton
Throughput Calculation gallon x 8.34 pounds x %TS x 60 minutes = pounds min gallon hour hour gpm
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100
150
200
%TS 0.020 0.022 0.024
1001 1101 1201
1501 1651 1801
2002 2202 2402
0.026 0.028
1301 1401
1952 2102
2602 2802
0.030
1501
2252
3002
Notice the large change in throughput w sma c ange n ens y or ow
Impact of Sludge Density 4500 4000 3500
2250 lb/hr
r h / 3000 b l i 2500 t u p h 2000 g u o r h 1500 T
1500 lb/hr
1000 500 0 8 1 / x t p p . 1 s 0 1 5 w s
0.02
0.022
0.024
gpm
0.026
0.028
0.03
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Primary To Secondary Sludge Ratio • The ratio is determined by primary solids in pounds divided by secondary solids in pounds –
• There is a direct correlation between primary solids to dewatering
• An increased P/S ratio reduces the amount of polymer
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Primary to Secondary Solids Blend
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Economic Impact Product
Unit Cost
Usage mpac
$ per 1,000 ry ons
Emulsion A
$2.50/active lb
7.5 lb/ton
$18,750
Emulsion B
$2.30/active lb
8.0 lb/ton
$18,400
. Dry B
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$2.00/lb
. 10.5 lb/ton
, $21,000
Primary to Secondary Solids Blend Suggested operational considerations • • Optimize primary BOD removal efficiency • Plan for impacts when taking activated sludge basins or rimar clarifiers out of service • Understand impacts of secondary wasting
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Polymer Factors • Polymer types
• Batching considerations • Mixing considerations
• Purchasing flexibility
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Polymer Characteristics
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Type
Appearance
Primary Ingredients
Active Content
Liquid - emulsion
Opaque
Polymer, oil, inverting surfactant water
25% - 40%
Liquid - dispersion
White
Polymer, oil, inverting surfactant
40% - 75%
Liquid - mannich
Clear, highly viscous
Polymer, water
3% - 8%
Dry
White granules, spheres, or powder
Polymer, dry surfactant
50% – 98%
Polymer Characteristics Type
Charge
Typical Molecular Weight
Cationic
Positive
Medium to ver hi h
Anionic
Negative
Medium to very high
Non-ionic
Neutral
Medium to very high
• Higher charge = more active sites on a molecule • Molecular weight dictates the length of the molecule; higher = longer • Higher molecular weight = harder to get into solution and more viscous when in solution 7 2 / x t p p . 1 s 0 1 5 w s
Polymer Characteristics Solution Strength
0.3% +/- 0.1
• Calculated by dividing the pounds of polymer added to a water in a batch area
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Batching – Need enough time to allow the polymer molecules to uncoil – Water temperature can impact aging time
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Potable or Non-Potable Water • During aging, solids in non-potable water take up charge sites and can decrease polymer performance • of polymer performance •
a e own wa er empera ure – Warmer is better
• Chlorine residual – High chlorine content can decrease performance 0 3 / x t p p . 1 s 0 1 5 w s
Polymer Mixing Systems • nsu c ent m x ng energy causes po ymer to ge , an prevents effective polymer activation • - Increased polymer dosage - Decreased process performance
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Solution Injection Point • Before centrifuge feed pump – Blended with sludge feed – Mixed through travel time, in piping and elbows –
• Upstream of rotating assembly – Allows for some mixing
• – Injected at the splash plate and diffuses into sludge 2 3 / x t p p . 1 s 0 1 5 w s
ugges
es ng a erna e po n s occas ona y
Contract Flexibility • Establish Primary and Alternate supplies – Use two different suppliers rather than two different products from the same supplier
• alternatives – An emulsion polymer may be more cost effective in winter months – A dry polymer may be more cost effective in the other months
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Putting It All Together • Centrifuge adjustments • Throughput • • Polymer solution feed rates • Operational targets •
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Optimization - Premise • The readily apparent visual clue is centrate quality • Within an operating range, optimum dosage results in quality centrate • When in the optimal dosing range, the driest • With excessive dosages, both cake dryness and cen ra e qua y w ec ne 6 3 / x t p p . 1 s 0 1 5 w s
Goal is to determine guidelines to achieve the optimal range for a variety of conditions
Test Methodology – Phase 1 • Batch polymer at preferred solution strength • Set sludge feed rate • Enter typical torque setpoint and bowl speed • • Run for a standard time (i.e., 45 minutes) • Sample feed, centrate and cake for TSS. Feed TSS is used to calculate throughput. rates • 7 3 / x t p p . 1 s 0 1 5 w s
Performance Curve Dose v. % Recovery 35
100 98
30
96 94
T 25 % r o n o t / b l
92 90
24 lb/ton 86
15
84 82
10
80 1
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2
3
Dose, lb/ton
4
Cake
5
Recovery
6
Test Methodology – Phase 2 • Set sludge feed rate • Set polymer solution feed rate for the “ideal” polymer dose • With sludge and polymer feed rates “locked in”, adjust % torque setpoint • Run for a standard time i.e., 45 minutes • Sample feed, centrate and cake for TSS. Feed TSS is used to calculate throu h ut. • Run through sequence for at least 5 torque setpoint 9 3 / x t p p . 1 s 0 1 5 w s
• Plot results
Performance Curve 2 Torque v. % Recovery 50
100 98 96
40 94
e 35 q r o T r 30 o
92 90
T 25 %
86
20
39% Torque
84
15
82
10
80 1
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2
3
Torque
4
Cake
Recovery
5
6
Outcome • Determine what dose is effective under what conditions • Determine what torque is effective at what throughput • Provide general guidelines to “dial in” centrifuges •
us ng more an one po ymer, e erm ne un er what conditions each is most effective
• Forecast usage to establish budget projections
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ons er sc e u ng u range o es ng a eas every months
Operating Range
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Throughput Range
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Polymer Dose Rate
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Guidelines With Budgetary Impacts Polymer
Projected Throughput
Cake Dryness
Centrate Capture
lb/hr per machine
below target
target
lb/hr per machine
above target
target
or seasonally Polymer
Time of Year
Emulsion
~Dec 15 – Apr 15 ~
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–
Dewatering – Operating Targets
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What Was Covered • Why optimize dewatering polymer use • What impacts centri uge output • What impacts polymer batching • The impact of P/S blend •
me o o ogy o e ne opera ng ranges
• Putting optimization in action
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