1. Evaluating Coagulants for Water Treatment
Kari Duncan – City of Lake Oswego
&
Doug Wise – Eugene Water & Electric Board
PNWS-AWWA Section Conference
May 2, 2008

2. Overview Varieties of Coagulants: Common Uses Case Studies:
Inorganic – Organic
Common Uses
Case Studies:
EWEB – City of Lake Oswego
The notes fill this space.

3. Entrance Strategy 1. Jar Test 2. Pilot Filter Evaluation
3. Cost Evaluation
4. ½ Plant Scale Test
The notes fill this space.

4. Entrance Strategy cont….
5. Plant Scale Trial
6. Calculate “Real” Cost
7. Evaluation Step
Operational Effectiveness
Look for Unintended Consequences
The notes fill this space.

5. Aluminum Sulfate (Al2(SO4)3 · 14 H2O
Inorganic coagulants  aluminum sulfate, aluminum chloride and ferric compounds
React with alkalinity to form positive ions which remove contaminants by adsorption.
Increasing turbidity  higher (sometimes dramatically higher) feed rates.

6. PACL (Polymeric Inorganic Coagulants)
“Generic” name that encompasses ACH, Sumaclear, Pass-C and others
Product variables:
Basicity 50%  80+%
Al:Cl ratio
Al2O3 content

7. PACL
A highly charged species that require little or no alkalinity to precipitate floc.
Due to the high charge of the PACL’s dose may not increase as much during increasing contaminant loading

8. PACL : ACH PACL formula: Al2(OH)(X)Cl(6-x)
Al:Cl ratio increases as basicity increases
ACH ‘special type of PACL’
Al:Cl ratio of 2:1
Basicity of 83%
Al2O3 content of 23%

9. Molecular Weight Comparison
Alum : max MW of 1,000
PACL: MW of 500 – 2,500
ACH: 4,000 – 5,000 (some up to 10,000)

10. Floc Size
Inorganic coagulants (Alum), and low basicity PACL form more voluminous, fragile floc.
With increasing charge, PACL tend
to form smaller floc with greater density
ACH forms a very tight, dense floc

11. Typical dosages
Product sales advisors often quote an “Aluminum percentage ratio”
For example, if the Al in the PACL is 4x that of Alum, they will cite an expected 25% of alum dosage.
50% basicity PACL; approx 80% of alum dosage
ACH: approx 33% of alum dosage.

12. Coagulation Control Jar Mix Pilot Filters Stream Current Monitors
Zeta Potentiometers

13. Coagulant Control: Jar Test

14. Coagulant Control: Control Filters

15. Coagulant Control: Current Monitor

16. Coagulant Control Jar Test: Remember to look for smaller
denser floc due to high basicity
when using high molecular
weight products
Control Filters
Streaming Current Monitor

17. Benefits Increased filter runs Reduced sludge generation
Sludge compacts / dewaters better
Greater turbidity removal capacity
Effective in low water temperatures
PACL does not lower pH

18. Check With Friends Drinking Water Program Bay Hills Water Association
City of Creswell
Garden Valley Water District
City of Lowell
City of Myrtle Point
City of Waldport
City of Yachats

19. What is in the “magic” elixir?
Cautions
What is in the “magic” elixir?

20. More Cautions!
PACL products range in grade and composition; test product(s) extensively before committing to their use.
Some products are sensitive to chlorine.
Products which form a suspension or generate sludge after only six months of storage are very low grade.

21. Case Study #1 Eugene Water & Electric Board’s
Hayden Bridge Filtration Plant

23. EWEB 72 MGD Raw Water Flow (108 MGD in 2009) McKenzie River Source
Direct Filtration (summer)
Conventional Filtration (winter)
Alum coagulant
Pre-chlorinate Cl2 gas
50% Caustic: corrosion control

24. EWEB 7 month trial of “Sumaclear 1000” from Summit Research Lab
Used Sumaclear predominantly through 2006.
Trial examined cost and filter run times while maintaining existing filtered water turbidity goal of NTU.

26. EWEB Field Results
Sumaclear 1000 dose was approximately 1/3 of Alum with low raw water turbidity.
With raw water turbidity above 4 ntu, Sumaclear 1000 was approximately 1/2 of Alum dose.
Experienced longer filter runs with Sumaclear.
Sumaclear resulted in an overall economic benefit (chemicals, wash water, sludge management) of approximately 20%.

27. EWEB Concerns
Some changes in distribution water quality coincided with Summaclear 1000 trials.
* Apparent DBP increase
* Small Lead and Copper increase (may no longer be “optimized)

28. EWEB Finds Fault A: We changed coagulant.
B: Our system water quality changed.
Therefore: the coagulant change made the system water quality change.

29. EWEB Review of JAWWA Article
on Cl- / SO4 Ratio Edwards & Triantafyllidou – July 2007
“…as the relative concentration of chloride to sulfate increased in a water supply, a utility was more likely to have a higher 90th-percentile lead concentration.”

30. PACL : ACH PACL formula: Al2(OH)(X)Cl(6-x)
Al:Cl ratio increases as basicity increases
ACH ‘special type of PACL’
Al:Cl ratio of 2:1
Basicity of 83%
Al2O3 content of 23%

31. EWEB
Not so fast….

32. There Are Other Considerations (EWEB)
Multiple changes in treatment variables at the time of test:
Added 15 MG Clearwell (May 2003)
Changed chlorination practice (May 2004)
Switched from Lime to Caustic (July 2004)
Switched from Alum to Sumaclear 1000 ( )

33. EWEB – Next Steps Continue Monitoring. Special Monitoring.
Make Gradual Treatment Changes.
Wait and Measure.

34. Case Study #2
City of Lake Oswego
Water Treatment Plant

35. City of Lake Oswego Water Treatment Plant
16 MGD
Clackamas River Source
Direct Filtration Plant
Alum (Coagulant)
Pre-chlorinate with Hypochlorite
Lime: corrosion control

36. City of Lake Oswego Feeds Alum alone during low turbidity.
Feeds a combination of Alum and Pass-C (Hydortech product) during high turbidity events.
Pass-C:
Al = 5/4 % ??
Al2O3: 10.3%
Basicity: 55%

40. City of Lake Oswego Field Results
The use of Pass-C at 3 to 11 mg/L decreases Alum use by up to (75%)* during periods of high raw water turbidity.
The use of Pass-C at high turbidity prevents the need for Operators to add additional alkalinity.
Improves ease of operation
Cost differences appear to be nominal
* Rough number

41. City of Lake Oswego Summary
Wide variety of products available.
Trial runs are very important.
Control your variables.
Perform a cost analysis.
Shop around and do your research.

42. Lessons Learned From Coagulant Trials
Intuitive expectations
may be erroneous.

43. Lessons Learned
Changes in the distribution system may result from changes in treatment at the plant.

44. Unknown, unreported and / or undocumented consequences may be common.
Lessons Learned
Unknown, unreported and / or undocumented consequences may be common.

45. Change only ONE thing at a time.
Lessons Learned
Change only ONE thing at a time.

46. Lessons Learned
Wait
Measure
Interpret

47. Acknowledgements
Kari Duncan for her work in documenting these results.
Randy Prock for developing the data at Hayden Bridge.
The Operators at both plants for their patience and persistence.

48. Questions?