sizing criteria for inclined plate settlers - e-ht.com · what are plate settlers? •for...
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Sizing Criteria for Inclined Plate Settlers
Theory, Current TCEQ Rules, and Full-Scale
Operating Data
Jordan Hibbs, P.E.
Jennie Kessler, E.I.T.
Enprotec / Hibbs & Todd, Inc.
April 16, 2014
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Agenda
• Background and Technical Information
• Advantages
• Sizing Criteria
• Uprating: Missouri City Case Study
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BACKROUND INFORMATION FOR PLATE SETTLERS
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What are plate settlers?
• For clarification/sedimentation
• A.k.a. lamella clarifiers
• Flexibility in type of basin
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How Plates Work
• Large settling area in small volume
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Sludge Collection
• Many options: existing clarifier, chain and flight, sludge scraper, hose vacuum…
• Hoseless vacuum is a low-maintenance option
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Plate settlers are rapidly gaining popularity
• Installations in Texas:
– MRI – 8
– JMS – 5
– Parkson – (Waiting)
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ADVANTAGES OF PLATE SETTLERS
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Advantages of Plate Settlers
• Plates require less space than conventional clarifiers
• Often less costly overall
Footprint Water Quality Coagulant Usage O&M
Straight-flow / Up-flow
Conventional Clarifiers
Solids-Contact / Sludge Blanket
Conventional Clarifiers Plate
Settlers
~5x the area of plate settlers
~3x the area of plate settlers
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Advantages of Plate Settlers
• Plates typically boost settled water quality
Footprint Water Quality Coagulant Usage O&M
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Advantages of Plate Settlers
• Plates typically allow modest reduction in coagulant dosage
Footprint Water Quality Coagulant Usage O&M
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Advantages of Plate Settlers
• O&M is straightforward – Only moving parts are in sludge collection mechanism – Hosing down typically needed monthly
Footprint Water Quality Coagulant Usage O&M
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SIZING CRITERIA
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From settling theory, capacity is proportional to horizontal surface area
Capacity = Loading Rate x Horizontal Surface Area gpm gpm/sf sf
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But horizontal surface area is not the same as footprint
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For plate settlers, capacity is based on Surface Loading Rate (SLR)
• Calculated over horizontally projected area
• Typically 0.3 gpm/sf
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TCEQ currently grants capacity based on Surface Overflow Rate (SOR)
• Calculated over footprint of equipment (including troughs and support equipment)
• 3.0 gpm/sf (vs. 1.0 gpm/sf per TAC 290)
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Available pilot data appears to support higher loading rates
Missouri City pilot study approach:
• Initial SLR of 0.3 gpm/sf; later 0.6 gpm/sf (using efficiency multiplier of 90%)
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Missouri City Pilot Study Results
• Increased SLR did not increase settled water turbidity.
334 NTU
103 NTU
1.35 NTU 1.31 NTU
1
10
100
1000
0.3 gpm/sf 0.6 gpm/sf
Average Turbidity
(NTU)
Surface Loading Rate (SLR)
Raw Water
Settled Water
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UPRATING IS AN OPTION: MISSOURI CITY CASE STUDY
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Missouri City Surface Water Treatment Plant
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Typical Turbidity
Average Turbidity (NTU)
Month Raw Water Settled Water
April 2013 33 0.70
May 2013 33 0.72
June 2013 43 0.75
July 2013 33 0.84
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Draft full-scale challenge test protocol has been submitted to TCEQ
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Proposed Goal: 0.6 gpm/sf while maintaining turbidity below 3.0 NTU 95% of time
• If approved, Missouri City plate settler capacity will double (11 mgd to 22 mgd)
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RECAP
• Plate settlers offer multiple advantages
• Sizing is based on Surface Loading Rate (SLR)
– However, TCEQ grants capacity based on Surface Overflow Rate (SOR)
• Uprating is an option, like Missouri City case
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QUESTIONS, COMMENTS
Thank you for attending