secondary clarifiers
DESCRIPTION
diseño de clarificadoresTRANSCRIPT
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS in activated sludge process
Jiri Wanner Institute of Chemical Technology, Prague
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• Separation of activated sludge in secondary clarifiers
• Construction of modern secondary clarifiers
• Examples from Czech WWTPs
• Design criteria used in the Czech Rep.
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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1. EFFLUENT QUALITY
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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2. THICKENING OF RAS and WAS
• PROBLEMS WITH ΘX
• OVERLOADING OF SLUDGE HANDLING FACILITIES
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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BASIC CLARIFIER CONFIGURATIONS
• CIRCULAR, RADIAL FLOW („DORR“)
• RECTANGULAR, HORIZONTAL FLOW:
• LONGITUDINAL FLOW
• TRANSVERSE FLOW
• CIRCULAR or RECTANGULAR, VERTICAL FLOW
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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DEGASIFICATION OF ACTIVATED SLUDGE MIXED LIQUOR
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CIRCULAR, RADIAL FLOW,
according to Albertson
• INLET STRUCTURE
• EFFICIENT SLUDGE
SCRAPER
• SCUM SKIMMER
• OUTLET STRUCTURE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
(Q+Qr), X QR+QW; XR = XW > X
Q-QW
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FLOW DIAGRAM OF CIRCULAR CLARIFIER
(IAWQ STR No.6)
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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INLET STRUCTURE
INFLUENT, ENERGY
DISIPATING WELL
„CLARIFLOW“ PORTS
FOR TANGENTIAL
FLOW (questionable)
FLOCCULATION ZONE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
WHAT HAPPENS IN CLARIFIERS WITH
FLOCCULATION ZONE
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FLOCCULATION ZONE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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No
flocculation
zone
Flocculation
zone
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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Scum
accumulation
with
tangential
inflow Unprotected weirs of effluent launder
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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FLOCCULATION ZONE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
• New construction of flocculation zone
• upper deflector preventing the
accumulation of scum
• lower deflector preventing the
disturbances in the separation and
thickening zones
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FLOCCULATION ZONE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
deflector
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
COVER
INLET
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
FOR LARGE CLARIFIERS …
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
… AND FOR SMALL CLARIFIERS (10.5 m total Ø)
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
STAMFORD BAFFLE – DEFLECTOR (SEE LATER)
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OUTLET STRUCTURE • PREFERABLY PERIPHERAL
LAUNDER AND WEIR
• LAUNDER SOMETIMES
COVERED (against algae growth)
• SCUM BAFFLE
• STAMFORD BAFFLE
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CONTROL OF ALGAE
GROWTH
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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THE IMPORTANCE OF SCUM BAFFLES WITHOUT BAFFLES:
FLOATING BIOMASS ESCAPES TO
THE EFFLUENT
WITH BAFFLES:
• CLEAR EFFLUENT
• PROBLEMS WITH
COLLECTED SCUM
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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THE IMPORTANCE OF SCUM BAFFLES
Floating
sludge
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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EFFLUENT PIPES INSTEAD OF SCUM BAFFLES
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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EFFLUENT PIPES INSTEAD OF SCUM BAFFLES
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION OF SCUM
classical scum box - low efficiency
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION OF SCUM
classical scum box - low efficiency
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION OF SCUM
classical scum box - often overloaded with scum
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION
OF SCUM
“travelling scum
box”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION
OF SCUM
“travelling scum
box”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION
OF SCUM
“pneumatic
systems”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
AIR
SCUM
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COLLECTION OF SCUM
“pneumatic systems”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
VENTILATOR SCUM SKIMMER
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COLLECTION OF SCUM “pneumatic systems”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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COLLECTION OF SCUM “pneumatic systems”
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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THE ROLE OF STAMFORD BAFFLE
Turns the sludge flow back to
the separation zone
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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Stamford baffle with peripheral launders
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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no need of Stamford baffle with internal launders
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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REMOVAL OF THICKENED SLUDGE
MOST COMMON TODAY
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
SPIRAL SCRAPERS
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CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
SPIRAL SCRAPERS
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REMOVAL OF THICKENED SLUDGE
combined shape of scraper
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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RECTANGULAR CLARIFIERS
• inlet baffle: energy dissipation, mixed liquor distribution
• flocculation zone: mechanical or hydraulic mixing
• effluent launders at side walls
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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FLOW REGIME IN RECTANGULAR CLARIFIERS
Infl.
Effl.
Effl.
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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effluent launders at side walls
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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effluent launders at side walls
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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hydraulic removal of thickened sludge
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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SKIMMERS AND SCRAPERS ON ENDLESS CHAIN
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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SKIMMERS AND SCRAPERS ON ENDLESS CHAIN
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS
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CLARIFIER DESIGN PARAMETERS ACCORDING
TO CSN 75 6401
• hydraulic loading v = Q/A
1.6 m/h for Qmax; 0.7-1.2 for Q24
• HRT 1.8 h
• solids flux NA = (Q x X)/A 6 kg/(m2.h)
• hydraulic loading of the effluent weir
< 10 m3/(m.h)
• R = QR/Q < 1.5 and SVI < 150 ml/g
CONTEMPORARY DESIGN AND OPERATION OF
SECONDARY CLARIFIERS