1. 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)
. . . .
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)
. . . .
2. •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
3. Goals
Major tasks as tertiary plant team chemist:
– 1) Improve sludge acid digestions
– 2) Explain phosphate removal problems
– 3) Systematize chemical additions
4. Problem (1)
Acid digests of plant solids contained a
gel that could not be removed. Such a
gel could interfere with analyses.
5. •(FYI) Solids in 1st Stage Clarifier
Reaction zone solids (RZ)
Recycle solids / sludge(SL)
Effluent
flow
slaked
lime
influent
effluent
Launderers gather effluent
Sludge out
udge out
rake
Slaked
lime
Launderers gather effluent
influent
effluent
6. Approach
• Ran tests, consulted with chemists, lab techs
• Did a literature search of digestion methods
• Wrote program ‘Dgstcalc’ to do calculations
7. Scope
• Ran 22 digestions in 7 months
• Accounted for up to 99% of plant sludge
10. 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
11. 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
12. 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.
13. 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
14. •(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
15. Scope
Spent >1 year gathering and analyzing data:
– Trickling Filter performance
– 1st Stage sludge chemical/physical characteristics
– 1st Stage effluents
– Organics throughout plant
16. 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 . . .
17. Phosphates out of Spec
Simplest View of Problem
12/7 12/27 1/16 2/5 2/25 3/16 4/5 4/25 5/15 6/4
date
various,scaledvalues
phosphate
in effluentvolatiles
in
reaction
zone
volatiles in
sludge
recycle change in
plant solids
phosphate
spec
18. 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
various,scaledvalues
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
19. 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
various,scaledvalues
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
20. 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
various,scaledvalues
phosphate
in effluentvolatiles in
reaction
zone
volatiles in
sludge recycle
change in
plant solids
21. 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
various,scaledvalues
phosphate
in effluent
volatiles
in reaction
zone
volatiles in
sludge
recycle
change in plant solids
(summarizes many
sludge physical
parameters -- plum
colored lines)
23. 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
24. HYPOTHESIS
Phosphate removal problems caused by
interaction of organics with plant solids to form
volatiles during temperature induced change in
density.
25. Towards a Practical Solution
• Substituting individual clarifier effluent
data for average clarifer effluent phosphate
shows that all clarifiers did not react the
same way
26. 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
various,scaledvalues
key point: clarifier 3 adjusted to volatiles more quickly than other clarifiers
clarifier 3
phosphate
27. 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)
28. 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
various,scaledvalues
clarifier 3 cycling
and viscosity
other clarifiers improved
when they began to 'look
more like' 3
average of all clarifiers
(including 3)
29. 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
30. 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
31. 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 . . .
32. 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 $$$$$$$$$$$
34. Approach
• Focused on head of plant to eliminate
variables, but later included rest of plant for
completeness
• Wrote program, FC_Chem, to do calculations
35. Scope
• Ran program 67 times over 6 months
• Accounts for up to 95% of 1st stage solids
36. Mechanics of FC_CHEM
• Inputs:
• plant flows and chemical additions
• lab data: influent, jar test, clarifier effluents
• Outputs:
• lime demand, CO2 & soda ash demand
• excess calcium, free carbonate & total solids
39. Report Format
• Results calculated using:
– influent data
– jar test data
– clarifier data
• Lab data presented with calculations
40. Feedback Loops
• Calculational methods may be compared for
insights into system
• Lab analysis confirms calculated value
(and vice versa) or signals need to
investigate
41. Benefits
• Uses systems approach
• Makes fine-tuning easier
• Potential for huge chemical savings $$$$$$
$$$$$$$$$$$$$$$$$$$$$$$$$$$
42. 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
43. 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
