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Examples of Work (1) Problem Solving
PCBWORKS
This presentation highlights work done as Tertiary Plant Team Chemist at the APS
Water Reclamation Facility at Palo Verde(examples contain no real plant data; values left out or altered)
. . . .
•The Water Reclamation Facility
provides water for the Palo Verde Nuclear
Generating Station– domestic & ultra pure water made from site
deep-well water– ‘process’ water made from City of Phoenix
sewage treatment effluent at Tertiary Plant
Goals
Major tasks as tertiary plant team chemist: – 1) Improve sludge acid digestions – 2) Explain phosphate removal problems – 3) Systematize chemical additions
Problem (1)
Acid digests of plant solids contained a gel that could not be removed. Such a gel could interfere with analyses.
•(FYI) Solids in 1st Stage Clarifier
Reaction zone solids (RZ)
Recycle solids / sludge(SL)
Effluentflow
slakedlime
influent effluent
Launderers gather effluent
Sludge outudge out
rake
Slaked
lime
Launderers gather effluent
influent
effluent
Approach
• Ran tests, consulted with chemists, lab techs• Did a literature search of digestion methods• Wrote program ‘Dgstcalc’ to do calculations
Scope
• Ran 22 digestions in 7 months • Accounted for up to 99% of plant sludge
Mechanics of DGSTCALC
• Input: sample mass/volume, ions • Output: assumed compounds, groups, ions
• Feedback/ QA: standard deviation, spike%, blank, digestion & analysis replicates, separations checks
Example: DGSTCALC OutputREACTION ZONE SUSPENDED SOLIDS DIGEST
Sample: FC3SL Temp: 22.00Date: 1/30 Type: grabTime: 08:00 Analysis: "limestone analysis"
average mass % rel std dev blank % rep(1)% rep(2)% spike %(assumed species)CaCO3 xxxxxxx 62.83 3.58 0.01 5.88 3.09 103.00Mg(OH)2 xxxxxxx 19.86 0.52 0.01 1.64 0.90 100.00SiO2 xxxxx 5.25 13.08 0.52 26.16 13.08
(ions)PO4 xxxx 3.85 0.87 0.00 3.15 1.55 101.00Fe xxxx 0.11 0.43 0.64 3.13 0.67 102.00SO4 xxxx 0.77 2.07 0.00 1.47 4.19 103.00
GROUPINGS ppm % QA ppm %TSS xxxxxx Cmpds xxxxxxx 87.85volatiles xxxxxx 12.36 Ions xxxxxxx 4.73Ca/Mg 1.84 Na Check 3.30Ca+Mg 82.68 SiO2 after 26.50
spike % transfer 100.72
Feedback Loops
Procedure checked four ways: – digestion by digest replicate (rep1) – analysis by analytical replicate (rep2)
– separations by Na and SiO2 checks
– matrix interference by spike recovery
Results and Benefits
• Coworker mentioned silicates often cause problems
• Found method that makes silicates acid insoluble • Filtered out silica, solving ‘gel’ problem and
ensuring better digestion numbers
Problem (2)
• The plant had had difficulty for some time (> ten years) controlling phosphate to specifications during the winter months. While many theories were advanced, what variables were involved was not known.
Approach • Worked closely with engineers, mechanics,
operators, and lab techs • Focused on entire system to include as man
many variables as possible• Did calculations, ran jar tests, used histor-ical
& current plant data & ran process tests to look at data from many points of view
•(FYI) Schematic Tertiary Plant System
Clarifier Feed Sump (FCIN)
1st Stage Clarifiers (FC1-6)
2nd Stage Clarifiers (FC7-12)
Gravity Filters
Trickling Filters (TF) (bacteria remove NH3, alkalinity,organics)
To Reservoir & Nuclear Units
Plant influent from Phoenix (WPIN)
(lime removes Ca, Mg, SiO2, PO4)
(CO2 & Soda Ash remove excess Ca)
Lines back from rest of plant
Scope
Spent >1 year gathering and analyzing data:– Trickling Filter performance– 1st Stage sludge chemical/physical characteristics
– 1st Stage effluents – Organics throughout plant
Graphing
• The following slides show different views of one graph: starting with the simplest, overall picture and adding details to expose the apparent causes of the problem . . .
Phosphates out of SpecSimplest View of Problem
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
phosphate in effluentvolatiles
in reaction zone
volatiles in sludge recycle change in
plant solids
phosphatespec
Immediate Cause Volatiles (Organics in Suspended Solid form) in Reaction Zone
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
phosphate in effluent
volatiles in reaction zone
volatiles in sludge recycle
change in plant solids
timeline: high (dissolved) organics in influent
key point: organics only become a problem when they interact with plant solids to form volatiles
Showing Data Points to Evaluate Goodness of Fit
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
phosphate in effluent
volatiles in reaction zone
volatiles in sludge recycle change in
plant solids
- emphasis on fit of 1/16 to 3/16 period- see next graph for view of fit of volatiles curves
Original, unsmoothed data (scaled to fit in same area of graph only)
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
phosphate in effluentvolatiles in
reaction zone
volatiles in sludge recycle
change in plant solids
What "Change in Solids" Represents
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
phosphate in effluent
volatiles in reaction zone
volatiles in sludge recycle
change in plant solids(summarizes many sludge physical parameters -- plum colored lines)
12/1
4/95
1/24
/96
3/6/
96
4/18
/96
5/28
/96
12/1
4
12/2
7 1/4
1/11 1/23 1/31 2/
9
2/21 2/29 3/12 3/21 3/28 4/10 4/24 5/
1 5/9
5/16 5/28 6/
4
-10
-5
0
5
10
15
20
phosphate peak
sl volatilespeak
rzvolatilespeak
hi wpinfgorganics
rz solidstransition
true timeline
virtual (control)timelines
change in solids matrix
3D View illustrates solids matrix
Change in Solids Due to a Larger Pattern,Temperature Induced Change in Density of Water
9/8 10/28 12/17 2/5 3/26 5/15
reaction zone temperature
phosphate in effluent
volatiles in reaction zone
volatiles in sludge recycle
change in plant solids
HYPOTHESIS
Phosphate removal problems caused by interaction of organics with plant solids to form volatiles during temperature induced change in density.
Towards a Practical Solution
• Substituting individual clarifier effluent data for average clarifer effluent phosphate shows that all clarifiers did not react the same way
Individual Clarifier Effluent Phosphates
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
cale
d va
lues
key point: clarifier 3 adjusted to volatiles more quickly than other clarifiers
clarifier 3 phosphate
What made clarifier 3 different?
– 1) on recal lime feed rather than purchased, pebble lime
– 2) higher viscosity of recycled solids– 3) higher cycling (ratio recycle to reaction zone
solids)
Clarifier 3 Compared to other Clarifiers
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
vario
us, s
caled
value
s
clarifier 3 cycling and viscosity
other clarifiers improved when they began to 'look more like' 3
average of all clarifiers(including 3)
TESTING
• With the aid of plant operators, a number of “process tests” were run to determine if other clarifiers could be made to “look like” clarifier 3
Testing on Clarifier 4 (Also on recal lime)
6/24 7/14 8/3 8/23 9/12 10/2 10/22
date
process test run by plant operator: 9/13
X
clarifier 3 cycling and viscosity
clarifier 4 cycling and viscosity
QUALIFICATIONS
• tests were not run during the winter season • other tests run on clarifiers on pebble lime
were not so successful • “process tests” are tests without real
controls, still . . .
Solution and Benefits
• The results suggest that solids control is the key to phosphate control in winter
• My friends at Palo Verde assure me that they no longer have a winter phosphate problem
• Benefit: extending the life of Nuclear Power Plant water systems $$$$$$$$$$$
•Problem (3)
• Chemical additions were determined largely by effluent quality.
Approach
• Focused on head of plant to eliminate variables, but later included rest of plant for completeness
• Wrote program, FC_Chem, to do calculations
Scope
• Ran program 67 times over 6 months• Accounts for up to 95% of 1st stage solids
Mechanics of FC_CHEM
• Inputs:• plant flows and chemical additions• lab data: influent, jar test, clarifier effluents
• Outputs:• lime demand, CO2 & soda ash demand• excess calcium, free carbonate & total solids
format: INPUT/analysis INPUT/computer/data STUFFED NUMBERdate: (hypothetical example)
PLANT FLOWS LIME ADDITION
flow:kgpm 60 LIME CONCENTRATION pumpstroke (count)time: 1 min A- mls 4.4 sta A 0.22 8vol/liters 227 B- mls 4 sta B 0.24 8
C- mls 4.3 sta C 0.29 9clarifier flows sta D 0.29 9fc1 10 normality 1.0123 sta E 0.27 10fc2 10 sta F 0.55 18fc3 10 A- spg 1.1100fc4 10 B- spg 1.1100 variance 0.1fc5 10 C- spg 1.1200fc6 10
FINFG/C LDT FC1EFF FC2EFF FC3EFF FC4EFF FC5EFF FC6EFF
pH xxx xxx xxx xxx xxx xxx xxx xxxp-alk/CaCO3 xxx xxx xxx xxx xxx xxx xxx xxxm-alk/CaCO3 xxx xxx xxx xxx xxx xxx xxx xxxPO4 xxx xxx xxx xxx xxx xxx xxx xxxMg as CaCO3 xxx xxx xxx xxx xxx xxx xxx xxxSiO2 xxx xxx xxx xxx xxx xxx xxx xxxCaCO3 xxx xxx xxx xxx xxx xxx xxx xxxNH3 xxx xxx xxx xxx xxx xxx xxx xxxTIC xxx xxx xxx xxx xxx xxx xxx xxxTOC xxx xxx xxx xxx xxx xxx xxx xxxTSS(rz) xxx xxx xxx xxx xxx xxx xxx xxx
Example: FC_Chem Output LIME DEMAND format: mg/l as CaCO3
Calculated-Influent Values & Chem Eqns. calc. 675
Lime Demand Titration calc. 666analysis 685
Lime Demand on Clarifiers calc analysisclarifier 1 698 667clarifier 2 700 650clarifier 3 705 668clarifier 4 668 705clarifier 5 650 700clarifier 6 667 698
average 681 681
Report Format
• Results calculated using: – influent data – jar test data – clarifier data
• Lab data presented with calculations
Feedback Loops
• Calculational methods may be compared for insights into system
• Lab analysis confirms calculated value (and vice versa) or signals need to investigate
Benefits
• Uses systems approach • Makes fine-tuning easier• Potential for huge chemical savings $$$$$$
$$$$$$$$$$$$$$$$$$$$$$$$$$$
Accomplishments
When I left APS after 3 years as Tertiary Team Chemist, I had – 1) achieved clean digestions – 2) resolved phosphate problem– 3) systematized plant chemical additions
Thank You!
• Thank you for viewing my presentation• Thanks to the members of WRF Tertiary
Treatment Team for their invaluable help and to APS for a wonderful job
Peter Charles Bierly