Procedure for the design and sizing of an Inclined Plate
Clarifier (parallel plate, lamella) for the removal of settleable
suspended solidsTable of Contents1. Inclined Plate Clarifier
(parallel plate, lamella) Theory of Operation2. General
Considerations3. Inclined Plate Clarifier Decision - Flow
DiagramDetermining ifyour process requires a clarifier or
clarification system4. Inclined Plate Clarifier Design - Flow
DiagramBasic process in the design of an oil water separator or
separation system5. The Impact of Settling Rate on Inclined Plate
Clarifier Design6. Sizing the Clarifier or Clarification
SystemInputting the accumulated data to the Hydro-Flo Clarifier
Sizing Spreadsheet to accurately size a clarifier or clarification
system for your application7. Comparing and Evaluating Clarifiers
and Clarification Systems from Different SuppliersReviewing and
filling out the Hydro-Flo Technologies, "Application Questionnaire"
will also help you gather pertinent information required for the
proper design and application of inclined plate clarifiers and
clarification systems.Inclined Plate Clarifier(parallel plate,
lamella) Theory of OperationBasic concepts and theories of
clarificationIf you are unfamiliar with basic inclined plate
clarifier (plate settler, parallel plate clarifier, lamella plate
settler, etc.) design principles, a review of the "Inclined Plate
Clarifier (parallel plate, lamella) Theory of Operation" might
prove helpful.This basic document covers Stokes' law and other
basic separation concepts.General ConsiderationsInclined plate
clarifiersare typically considered very simple devices. However,
several factors that could potentially affect safety, efficiency,
and proper management must be given careful consideration prior to
the installation or modification of any clarifier or clarification
system:1. Flow RateIn general, clarifiers are sized by the flow
rate verses the separation chambers "effective" surface area (or,
as it is more commonly called. the "projected" surface area).
Therefore, the effectiveness of any clarifier is affected by the
flow rate. The slower the flow, the better the results.2. Design
CapacityA clarifier has upper limits to the amounts of suspended
solids that can effectively accumulate while it is in operation. If
too much "sludge" or settled suspended solids accumulate on the
plates, it may carry over into the wastewater outlet chamber and
end up being discharged to the environment. Proper clarifier design
will take the plate spacing into consideration and also allow for
the removal and storage of accumulated sludge from the clarifier to
ensure that the accumulated products do not effect the operation of
the clarifier.3. Maintenance PracticesThe ability of any clarifier
to function properly depends upon the timely performance of
required service and maintenance. Clarifiers must be monitored and
maintained by competent personnel who understand how the systems
operate. Clarifiers should be given the same close attention shown
to any other important piece of equipment. The operators, users,
and maintainers of the clarifier must be clear on who will be
responsible for monitoring, inspecting, maintaining, and servicing
the system. Frequent inspections should be made of the system and
all associated piping, valves, etc. to prevent operational and
mechanical failures or inefficiencies. Sludge needs to be regularly
removed from the clarifier to keep it operating properly.
Additionally, leaks from clarifiers can result in environmental
pollution, which can trigger costly investigative studies and
cleanups. Rigorous implementation of a clarifier inspection and
maintenance plan can prevent discharges from the clarifier that may
contaminate the environment.4. Suitability of Inclined Plate
Clarifier System to ProcessA clarifier designed and installed to
meet a past process requirement may no longer be suitable when
process requirements change and/or the original maintenance plan is
no longer followed. A clarifier that is put to a use for which it
was not originally designed may be damaged or may not function
properly, and could become an environmental liability. For example,
a clarifier designed to receive the wastewater discharge from a
small heavy metal precipitation system will not be able to properly
treat larger wastewater volumes for removing chrome from a tannery
effluent. Process changes can also result in changes to the
physical/chemical makeup of the wastewater being treated by a
clarifier.5. Contaminants Contained in the Wastewater
StreamMetallic particles in the wastewater will settle into the
sludge at the bottom of the clarifier. Solvents or fuel compounds
may also be entrained in the clarifier's sludge. This sludge could
require management under the Resource Conservation and Recovery Act
(RCRA) as a hazardous waste, if it exhibits certain toxicity
characteristics. Therefore, it is important to prohibit the
discharge of certain types of potential contaminants into a
clarifier, and to regularly analyze sludge samples to determine
toxicity prior to disposal. General improvements in spill/drip
control and containment of hazardous materials and solvents will
also reduce the amount of contamination in clarifier
discharges.Inclined Plate Clarifier Decision - Flow
DiagramDetermining if your process require a clarifier or
clarification systemWhy ChooseHydro-Flo Technologies
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ClarifierSizing informationInclined Plate Clarifier Design
ParametersDetailed information on the design and sizing of inclined
plate clarifiers and clarification systems
Dissolved Air Flotation SystemDesign & Sizing
informationDissolved Air Flotation Design ParametersDetailed
information on the design and sizing of dissolved air flotation
separators and separation systems
Oil Water SeparatorDesign & Sizing informationOil Water
Separator Design ParametersDetailed information on the design and
sizing of oil water separators and separation systems
Misc Info, Data, Spreadsheets & CalculationsEPA Non-Polar
Oil Test MethodsFluid MechanicsReynolds Number CalculationsWater
Hammer Calculations
HFT Quality ControlHFT QualityAssurance PlanSteel
FabricationsLeak Test CertificationInterior CoatingsExterior
CoatingsControl Panels
Chemical / Material Compatibility DataChemical
PumpDosingRatesChemical CompatibilityChartProperties of Plastic
Coating / Materials DataSurface PrepDefinitionsStandard Internal
CoatingStandard External Base CoatingStandard External
TopCoatingFRP Resin Cut SheetsGel Coat Cut Sheet
STEP 1:Identify Wastewater SourceBuildings and areas, as well as
ALL activities and processes within the buildings and areas, that
generate wastewater
STEP 2:Institute Pollution Prevention and Source Elimination /
Reduction ProceduresCan the processes that generate the wastewater
be eliminated? Can the process be converted to a dry process?
STEP 2-A:Process altered or eliminated, no further
dischargeSTOPNo Further Action Required
STEP 3:Source DiversionCan the process be moved to an area that
has existing clarification equipment in place? Can the existing
equipment handle the increased flow? Is moving the process,
diverting the flow, economically feasible?
STEP 3-A:Process relocated or discharge divertedSTOPNo Further
Action Required
STEP 4:Wastewater Compliance Evaluation
Identify permit limits on ALL pollutants generated at the site.
Characterize raw wastewater prior to any treatment, if appropriate.
Characterize treated wastewater if existing treatment equipment is
in place.
STEP 5:Discharge & Pretreatment Requirements
Does the raw wastewater meet permit limits and environmental
requirements? Does the treated wastewater meet permit limits and
environmental requirements?
STEP 5-A:Discharge meets requirements,STOPNo Further Action
Required
STEP 6:New Clarifier or System Upgrades Required. Proceed to
Inclined Plate Clarifier Design - Flow Diagram
Inclined Plate ClarifierDesign - Flow DiagramBasic process in
the design of a clarifier or clarification system
STEP 1:Conduct a Wastewater Characterization StudyThe engineer /
designer may conduct a wastewater characterization study to
establish clarifier or clarification system design parameters.The
first step in a wastewater characterization study is to conduct the
"Clarifier Settling Velocity" test. This bench test will help
determine the clarifier's "TARGET" effluent quality at a specific
particle settling rate. If possible, you should conduct this test
numerous times to allow for variances in your overall process.
STEP 2:Determine the Type of Clarifier or Clarification System
Necessary for Your ProcessEvaluate the results of the
characterization study and determine the category of suspended
solids to be removed. Decide what type of clarifier or
clarification system to use.NOTE:Hydro-Flo ClariMax clarifiers are
an excellent separation solution for complex, evolving processes.
The Hydro-Flo ClariMax clarifiers are designed to evolve with your
growing, expanding process requirements. These robust clarifiers
can be retrofit with a variety of plate packs, increasing the
efficiency of the separator as your process or discharge
requirements change. Surface drag skimmers for processes, vapor
tight lids, etc. are simple bolt on modifications.
STEP 3:Do You Havean Existing Clarifier at Your FacilityIf there
is an existing clarifier on site, evaluate if it may be upgraded to
accept the total flow or partial flow from the proposed source to
reduce loadings.
STEP 3-A:Will Upgrading the Existing Clarifier Bring the
Discharge into ComplianceCan the existing system be upgraded (by
the installation of alternate plate packs, etc.) or adding
additional treatment capabilities, etc.
STEP 4:Review Concerns and Requirements of the New Clarifier or
Clarification System with the Engineer / DesignerList all
provisions that need to be considered to ensure the new system will
be accessible for maintenance, will meet site specific area
classifications (i.e.: seismic and explosion proof area
classifications, etc.) and will meet all regulatory and effluent
discharge requirements.
STEP 3-B:Can the Existing Clarifier be Used to Pre-treat the
Wastewater Prior to the New ClarifierEven if the existing clarifier
is not capable of handling the proposed load, it may be useable as
a form of pre-treatment or used in conjunction with the proposed
upgrades.
STEP 5:Write the Specifications for the New or Upgraded
Clarifier or Clarification SystemsWrite specifications for the new
clarifier, the clarifier upgrade or the new clarification system
required to meet all the above listed concerns and
requirements.STEP 3-C:Incorporate existing clarifier into
design
STEP 3-D:If determined that the existing clarifier is no longer
suitable for its current use or is unusable in the new system,
incorporate the closure of the existing clarifier into the
specifications
STEP 3-E:Design the upgrade of the existing clarifier
The Impact of Settling Rate on Inclined Plate Clarifier
DesignDetermining the hydraulic loading ratio required to meet your
effluent requirements (ppm, mg/l) is an important step in the
design and sizing of any clarification system. A small change in
the hydraulic loading ratio can result in a large change in the
size of the specified clarifier. For example look at the following
spreadsheets.Input
What is the Process Flow Rate100.00
What is the Desired Hydraulic Loading Ratio0.25
What is the Desired Plate Spacing2.00
Output
Required PSA400
Available ModelsCross Sectional VelocityIn Ft/MinTotal Effective
PSAActual HydraulicLoading Ratio
139-10-1-ST OR PB1.025590.18
139-10-2-ST OR PB1.025590.18
129-8-1-ST OR PB0.875120.20
129-8-2-ST OR PB1.024390.23
127-6-1-ST OR PB0.684790.21
139-6-2-ST OR PB0.615320.19
MODEL NOT AVAILABLE0-4-1-ST OR PB#DIV/0!0#DIV/0!
120-4-2-ST OR PB0.513990.25
Required Cubic Feet of MediaOverall Plate LengthNumber of
Influent TroughsSludge ThickeningorPyramid Hopper
EXAMPLE ONEInput
What is the Process Flow Rate100.00
What is the Desired Hydraulic Loading Ratio0.40
What is the Desired Plate Spacing2.00
Output
Required PSA250
Available ModelsCross Sectional VelocityIn Ft/MinTotal Effective
PSAActual HydraulicLoading Ratio
104-10-1-ST OR PB1.533730.27
139-10-2-ST OR PB1.025590.18
86-8-1-ST OR PB1.223660.27
86-8-2-ST OR PB1.532930.34
81-6-1-ST OR PB1.023190.31
92-6-2-ST OR PB1.023190.31
74-4-1-ST OR PB0.762660.38
74-4-2-ST OR PB0.762660.38
Required Cubic Feet of MediaOverall Plate LengthNumber of
Influent TroughsSludge ThickeningorPyramid Hopper
EXAMPLE TWOThe only change in the above spreadsheets was the
"Hydraulic Loading Ratio". All other variables remain the same.On
the first spreadsheet the "Hydraulic Loading Ratio" was input at
.25. On the second spreadsheet the "Hydraulic Loading Ratio" was
input at .40. You will note that the model #'s (which represent the
total cubic feet of media required) changed from a high of 139
cubic feet to a low of 74 cubic feet. That is a 46% change in the
total size of the separator.Both examples are suitable for 100
gallons per minute. Both examples will remove the targeted
suspended solid. The real world difference between all the listed
clarifiers is overall clarifier efficiency.This example should
reinforce the importance of accurately conducting the "Test for
Determination of Clarifier Hydraulic Loading Ratio" and
the"Clarifier Settling Rate" studies. If you size a clarifier
without knowing the target "Hydraulic Loading Ratio", you will have
to greatly over size the clarifier, because erring on the safe
side, you will have to size the clarifier for maximum
efficiency.Sizing the Clarifier or Clarification SystemInputting
the Accumulated Data to the Hydro-Flo Clarifier Sizing Spreadsheet
to Accurately Size a Clarifier or Clarification System for Your
ApplicationThe final step is to insert the data into the "clarifier
sizing spreadsheet".NOTE:ALWAYS SPECIFY THE "SHORTEST" PLATE LENGTH
FEASIBLE FOR YOUR INSTALLATION.This isVERYimportant.All things
being equal (projected surface area and plate spacing), a clarifier
with 4' long plates will generate better results than a clarifier
with 8' long plates.A clarifier with 4' long plates (as opposed to
a clarifier with 8' long plates) will accumulate 1/2 the amount of
sludge on the surface of the plates. Lower accumulation of sludge
per plate helps prevent sludge re-entrainment and clarifier
fouling.Also, shorter plates will lower cross sectional velocities
and improve overall laminar flow conditions.The trade off is that
clarifiers with short plate lengths take up more floor space. A
clarifier with 8' long plates will take up half the floor space
that a comparable clarifier with 4' long plates.Comparing and
Evaluating Clarifiers and Clarification Systems from Different
SuppliersIf you go to ten different clarifier manufacturers and ask
them to size a clarifier for a specific application (even when
giving them a written specification), you will get ten different
answers. Everyone bases the efficiency of their clarifier on their
clarifier's projected surface area. But, other design variables are
all over the map. Plate spacing will vary from 3/4" to 2", and
more. The angles and configurations of the plates are vastly
different from manufacturer to manufacturer. Overall clarifier
volume, from the largest to the smallest designs, can fluctuate as
much as 150%, or more.When comparing one manufacturer to another,
it is best to compare the volume of the separation chamber (or size
of the plate pack) in cubic feet verses the sell price. This ratio
should give you the clarifiers cost per cubic foot of plate pack.
This is important because the physical size of the clarifier is the
greatest factor in the cost, as well as the efficiency, of the
device. The published projected surface area has a much smaller
impact on the clarifier's overall cost and performance.NOTE:DO NOT
COMPARE CLARIFIERS BASED SOLELY ON THE AMOUNT OF PROJECTED SURFACE
AREA!This isVERYimportant.Many clarifier manufacturers use the
smallest plate spacing possible in their clarifiers. This allows
them to post the largest projected surface area numbers possible,
giving the customer the impression that they are purchasing the
most efficient separator available.Unfortunately, using the
smallest possible plate spacing is not the answer. Care must be
taken when specifying plate spacing. If the plate spacing is too
narrow, the results will be excessively high cross sectional
velocities and unacceptably high Reynolds numbers, improper plate
pack distribution and short circuiting issues, as well as sludge
re-entrainment and high volumes of floc carry over.There are many
clarifiers in the field built with 8 foot long plates and 3/4"
plate spacing that are only capable of operating at 30% of the
designed flow rate! There are also many clarifier manufacturers who
specify 1" plate spacing, but in fact, they are actually less than
that because they do not account for the plate thickness in their
calculations.Make sure that, when you are talking about plate
spacing, you are talking about the distance between the plates -
not the distance from plate center to center. On smaller
applications, the difference does not amount to much, but on large
projects, the difference can be substantial.Also, many
manufacturers claim that their clarifiers are 100% efficient.
Current fluid dynamic studies have shown that even the best designs
are 85% efficient at best and that some are even as low as 50%
efficient. We rate our clarifiers at a conservative 80% efficiency
rating. Make sure that you receive confirmation of the clarifier's
total projected surface area as well as the clarifier's
