not so long ago at a water treatment plant far ... - pnws-awwa · –filter backwash design...
TRANSCRIPT
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Not so long ago at a water treatment plant far,
far away…
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Treatment Plant WashwaterRecovery to Achieve Zero Liquid DischargeAlex Mofidi PE
Jim Passanisi, Neil Essila, Bill Taylor (PID)
Bill Clunie PE, Joe Huang PE (AECOM)
Paradise
Irrigation
District
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Discussion Topics
– Project Introduction and Key Issues
– WTP Process Overview
– Pilot Testing Plan
– Testing Results and Summary
– Recommendations and Next Steps
Page 3
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Discussion Topics
– Project Introduction and Key Issues
Page 4
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Introduction
Page 5
CA
OR
NVParadise Irrigation District,
Paradise, CA
– Paradise Irrigation District
• Surface water supply
oParadise Lake
oMagalia Reservoir
• 19 MGD Paradise WTP
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Introduction
Page 6
– Paradise Irrigation District
• Surface water supply
oParadise Lake
oMagalia Reservoir
• 19 MGD Paradise WTP
– WTP Washwater Discharge
• NPDES permit challenges
oTotal aluminum
oDichlorobromomethane (DCBM)
CA
OR
NVParadise Irrigation District,
Paradise, CA
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Key Project Issues
Page 7
– WTP Washwater Discharge
• NPDES permit challenges
• Washwater discharge to Magalia Reservoir (CA Toxics Rule)
oTotal aluminum (0.077 mg/L month avg; 0.123 mg/L max day)
oDCBM (0.56 µg/L month avg; 1.12 µg/L max day)
• Permit Time Schedule Order (TSO): Discharge Treatment Required
– Large Volume of Low-TSS Washwater
– Way Forward?
• Implement washwater treatment
• Discontinue discharge
0.350.9 3.61.3
Jul 2010 – Jul 2014
Jan 2008 – Nov 2009
PID Washwater Results
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Discussion Topics
– Project Introduction and Key Issues
– WTP Process Overview
Page 8
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– Alternative Treatment
• Upflow ContaClarifier
oRoberts Filter (3 ea.)
oNon-buoyant coarse media
• Filtration
oDual media filtration (6 ea.)
oAnthracite over sand
Paradise Water Treatment Plant
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Paradise Water Treatment Plant
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– Alternative Treatment
• Upflow ContaClarifier
oRoberts Filter (3 ea.)
oNon-buoyant coarse media
• Filtration
oDual media filtration (6 ea.)
oAnthracite over sand
– Very Low Chemical Feed & Residual Production
• Alum (0.8 to 3.3 mg/L): destroys ~1.5 mg/L Alkalinity
• ACH (0.6 to 1.8 mg/L)
• Cationic polymer (0.6 to 1.7 mg/L)
• Anionic filter aid polymer (0.009 to 0.023 mg/L)
• Estimated 30-40 lb/MG solids produced
2015 Raw Water Quality
Alkalinity, tot: 29-38 mg/L
pH: 7.3-7.6 units
Temperature: 45-67 oC
Turbidity: 0.3-2.7 NTU
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Paradise Water Treatment Plant
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Paradise Water Treatment Plant
Page 12
– ContacClarifier Washwater Design Considerations
• Approximately 80,000 gallons/flush
o60-80 NTU in the first 2 minutes
oRemaining turbidity <20 NTU (~15 minutes total)
o<50 pounds of solids/flush (TSS between 0.006% to 0.007%)
• Up to 12 flushes/day (from 160,000 to 1,200,000 GPD)
– Filter Backwash Design Considerations
• Approximately 1 backwash every two days
• Three filters operating in winter
• Six filters operating in summer
• 140,000 gal/backwash (TSS between 0.002% to 0.005%)
oFilter backwash water
oFilter to waste water
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– Project Introduction and Key Issues
– WTP Process Overview
– Pilot Testing Plan
Page 13
Discussion Topics
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Pilot Testing Plan
Page 14
– Goal: Zero Discharge
• Treat all washwater from clarifier and filters
• Process solids on-site
• Assess liquid-solid separation of lamella plates
• Determine thickening capability of lamella-settled solids
– Lamella Plate Settling
• Recycling of supernatant to the head of the WTP
• Possible use of supernatant as clarifier flush water supply
• Suitability of separated solids to be thickened and meet proper
consistency for efficient mechanical dewatering
• Simulate failure mechanisms (high HLR and/or improper
polymer/coagulant dose) to characterize process upsets
• Obtain HLR / sizing, design criteria
HLR = Hydraulic
Loading
Rate
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Pilot Testing Plan, continued
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– Operations and Regulatory Requirements
– USEPA Filter Backwash Recycling Rule
• Supernatant return to head of WTP
• Flow restriction
• Turbidity restriction
– DBPs
• Will levels rise during recycling/reuse practice?
– Supernatant and Solids
• Supernatant turbidity targets: ≤2 NTU (90th percentile)
• Supernatant flow target (for design): 10% instantaneous
• Solids thickening goals: >20% solids
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Pilot Testing Plan, continued
Page 16
– Preliminary Bench-Scale Screening
• Anionic and Cationic polymers tested
• Anionic polymers were not able to reduce turbidity <2 NTU
• Cationic polymers best (based on settling, final supernatant turbidity)
Minutes Minutes
Jar
Inte
rfac
e H
eig
ht
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Pilot Testing Plan, continued
Page 17
* SuperFloc and AE212 are polyacrylamide polymers; requiring a
maximum WTP dosage of 1 mg/L (based upon full WTP flow)
– Testing Matrix
• Lamella
oHLR: 0.2 – 0.6 GPM/sf
oThickener Blowdown Rate: 3 – 30 % of feed flow
oSolids Recirculation Rate: 0 – 3 % of feed flow
• Chemical Dosing
oCoagulant (Aluminum Sulphate): 0 – 7.5 mg/L
oCationic Polymer (ZetaFloc): 0.5 – 100 mg/L
oCationic Polymer (SuperFloc*): 0.001 – 5 mg/L
oAnionic Polymer (AE212*): 0.02 – 6 mg/L
• Simulate process upset
oWashwater return causing turbidity spike
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– Project Introduction and Key Issues
– WTP Process Overview
– Pilot Testing Plan
– Testing Results and Summary
– Recommendations and Next Steps
Page 18
Discussion Topics
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Pilot Plant Setup
Page 19
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Full-Scale Design Representation
Page 20
Lamella
Plate Settler
Supernatant
Return
Solids to
Dewatering
Feed
Washwater
Solids
Return Thickening
& Dewatering
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Actual Process Tested
Page 21
Turbidity
TSSSettleabilityDewaterability
Turbidity
DBPFP
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Actual Process Tested
Page 22
SolidsRecirc
ChemMix
Tank
Lamella
Blo
wdow
nT
hic
kener
Lamella
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Pilot Test Results
Anionic Polymer & Alum
Page 23
No Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
Zetafloc Cationic Polymer & Alum
Page 24
No Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
4 mg/L SuperFloc Cationic Polymer & 3 mg/L Alum
Page 25
No Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
5 mg/L SuperFloc Cationic Polymer & 3 mg/L Alum
Page 26
No Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
3 mg/L SuperFloc Cationic Polymer
Page 27
With Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
1 mg/L SuperFloc Cationic Polymer
Page 28
With Recycle
Tu
rbid
ity (
NT
U)
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Pilot Test Results
Summary of Test Conditions
Page 29
SuperFloc Cationic Polymer
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Pilot Test Results
DBP Bench Testing
Page 30
1. Duplicate tests, collected after lamella
2. Stored in the lab in amber, Cl2- demand-free glass
3. Tests at 7 & 14 days storage
1. Starting residual at ~0.25 mg/L
2. No residual Cl2 after 14 days
3. DBPs not considered to be an issue (will only become a small portion of treated water)
CONDITIONS
RESULTS
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Pilot Test Results
Dewatering Bench Testing
Page 31
Poor Cake (Pin Floc)
Good, Non-Sticky Floc(31% TS)
1. Jar testing to generate flocculated, solid mass2. Solids squeezed through filtration cloth3. Dewatered cakes tested for %TS
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Recommendations and Next Steps
Page 32
– Lamella Results
• Several conditions met 2 NTU goal
oHLR can operate from 0.4-0.5 GPM/sf
o1 – 3 mg/L SuperFloc Cationic Polymer
oAlum not required
• DBPs not an issue
o<60 TTHMs & <40 HAA5
oRecirculated volume with these values is very, very a small portion of flow
– Dewatering Results
• 30% TS achievable with anionic polymer
• Confirm results and optimize polymer dose at full-scale
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Recommendations and Next Steps, continued
Page 33
– Operations and Regulatory Conditions
• Allowed to increase flow above 10% instantaneous (for short periods)
• Allowed to recycle to head of WTP (meeting 2 NTU goal)
• Allowed to use as ContaClarifier washwater
– Design Moving Forward
• Flow equalization is a major focus of design & future operations
• Prevention of hydraulic surges
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Recommendations and Next Steps, continued
Page 34
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Thank You!
Alex Mofidi PE