Lamella Clarifier for Industrial Wastewater Treatment

 A lamella clarifier is an industrial clarifier that uses inclined settling plates to increase the effective settling area available for separating solids from water.

The basic principle is gravity separation.

Suspended particles that are heavier than water naturally settle. A conventional settling tank requires those particles to travel a relatively long vertical distance before reaching the bottom.

A lamella clarifier changes that geometry.

Multiple inclined plates create closely spaced settling surfaces throughout the clarifier. Suspended particles only need to travel a short distance before contacting one of these plates.

Once solids collect on a plate, they combine with other particles, become heavier, and slide down the inclined surface into the sludge collection cone below.

Meanwhile, clarified water continues upward through the plate pack and exits from the top of the clarifier.

This allows a lamella clarifier to provide a large projected settling area without requiring the footprint of a large conventional settling tank.

 Several terms are commonly used to describe this type of equipment.

You may encounter:

• Lamella Clarifier
• Lamella Settler
• Inclined Plate Clarifier
• Inclined Plate Settler
• Parallel Plate Clarifier
• Plate Settler
• Slant Plate Clarifier
• Industrial Clarifier

Although there can be differences between individual equipment designs, these terms generally describe clarification systems that use inclined settling surfaces to increase the available settling area.

Met-Chem uses an inclined parallel plate design for industrial wastewater clarification.

 The inclined plate pack is what makes a lamella clarifier different from a simple settling tank.

The plates provide many settling surfaces within the same tank footprint.

Imagine replacing one large settling surface with numerous parallel settling surfaces stacked vertically.

That is essentially what the lamella plate pack accomplishes.

The result is a much larger effective projected settling area within a relatively compact piece of equipment.

Met-Chem's standard lamella clarifier design uses plates positioned at approximately 60 degrees.

This angle provides an effective balance between projected settling area and the ability of accumulated sludge to slide down the plates.

If the angle becomes too shallow, solids may have greater difficulty moving down the plates and can accumulate within the pack.

 One of the most important concepts in lamella clarifier design is projected settling area.

The physical surface area of an inclined plate is not the same as its effective horizontal projected area.

For a basic inclined plate:

Projected Area = Plate Length × Plate Width × cos(θ)

where θ is the plate angle measured from horizontal.

For multiple plates:

Total Projected Settling Area = Number of Plates × Plate Length × Plate Width × cos(θ)

This helps explain how a relatively compact lamella clarifier can provide substantial settling area.

However, plate area should not be the only consideration when selecting an industrial lamella clarifier.

Hydraulics, wastewater chemistry, solids loading, retention time, floc formation, sludge storage, and sludge removal also influence real-world performance.

 Met-Chem considers retention time an important part of industrial clarifier design.

Industrial wastewater does not always enter a treatment system under perfectly constant conditions.

Flow, pH, solids concentration, contaminant concentration, and floc characteristics can change during production.

Providing sufficient tank volume and retention time can help stabilize these variations.

Met-Chem lamella clarifiers are designed with approximately 50–60 minutes of retention time in standard configurations.

Adequate retention time can help:

• Reduce hydraulic disturbances
• Allow additional floc development
• Improve solids separation
• Reduce the chance of solids carryover
• Provide additional sludge storage
• Accommodate variations in wastewater flow
• Provide more consistent treatment performance

A lamella clarifier should therefore not be selected solely because a plate pack is theoretically rated for a particular flow.

The entire clarification system matters.

 Another important design consideration is the relationship between flow and settling area.

A simplified surface loading relationship can be expressed as:

Surface Loading Rate = Flow ÷ Effective Settling Area

or:

SLR = Q ÷ A

Where:

Q = wastewater flow rate

A = effective projected settling area

Lower surface loading provides more settling area for a given flow.

However, surface loading is only one part of lamella clarifier sizing.

Met-Chem also evaluates:

• Average flow
• Peak flow
• Suspended solids concentration
• Type of solids
• Wastewater temperature
• Wastewater chemistry
• Precipitation requirements
• Coagulant requirements
• Polymer requirements
• Floc settling characteristics
• Plate spacing
• Plate angle
• Sludge production
• Sludge storage
• Retention time
• Downstream treatment requirements

Two facilities treating the same number of gallons per minute may therefore require very different clarification systems.

 A well-designed lamella clarifier cannot compensate for poor chemical treatment.

This is particularly important in industrial wastewater treatment.

Very small suspended particles may settle extremely slowly. Dissolved contaminants will not settle at all until they are chemically converted into insoluble solids.

A typical treatment sequence may therefore include:

pH Adjustment → Coagulation → Flocculation → Lamella Clarification

Coagulants can help destabilize fine particles.

Polymer can then help these particles combine into larger floc.

The larger floc enters the lamella clarifier where gravity separation takes place.

For this reason, Met-Chem can incorporate a flocculation compartment and mixer into the clarification system.

One of the most common uses for an industrial lamella clarifier is the removal of metals from industrial wastewater.

A common misconception is that the clarifier itself removes dissolved metals.

The treatment process actually occurs in stages.

For many metal-bearing wastewaters, pH is adjusted to convert dissolved metal ions into insoluble metal hydroxides or other precipitates.

These newly formed particles can then be coagulated and flocculated.

The resulting solids enter the lamella clarifier, settle onto the inclined plates, and eventually collect in the sludge cone.

The clarifier is therefore the solids separation stage of a larger chemical wastewater treatment process.

 Removing sludge is just as important as settling it.

As solids move down the inclined plates, they accumulate in the bottom cone of the clarifier.

If this sludge is allowed to build excessively, the sludge level can rise toward the plate packs and interfere with clarification.

Met-Chem therefore recommends establishing a regular sludge removal procedure.

For many applications, an automatic sludge blowdown system is preferable.

Instead of waiting for the cone to fill with a large volume of sludge, smaller quantities can be removed frequently.

This helps maintain available sludge storage volume and provides more consistent clarifier operation.

Clarifier sludge still contains a significant amount of water.

For many industrial applications, the next step is sludge dewatering.

A common Met-Chem process is:

Lamella Clarifier → Sludge Holding/Thickening Tank → Filter Press

The sludge holding tank provides storage between clarifier blowdown cycles and filter press batches.

The filter press then applies pressure to remove additional water from the sludge and produce a substantially drier filter cake.

Filtrate from the filter press can often be returned to the beginning of the wastewater treatment system

 Lamella clarifiers and filter presses work particularly well together because they perform complementary functions.

The lamella clarifier is generally a continuous separation device.

The filter press is a batch dewatering device.

The clarifier continuously removes suspended solids from the wastewater stream and concentrates those solids into a smaller sludge stream.

The filter press periodically processes that concentrated sludge.

This arrangement allows an industrial wastewater system to continuously treat water while producing a dewatered filter cake for disposal.

 The plate pack is one of the most important components of the clarifier.

Met-Chem plate packs use multiple inclined parallel plates to create the settling area required for clarification.

Standard Met-Chem plate packs can include:

• 60-degree inclined plates
• PVC settling plates
• Structural outer frame
• Closely spaced parallel flow channels
• Lifting points for removal and maintenance

Alternative materials can be considered when required by wastewater chemistry or operating conditions.

Met-Chem also manufactures replacement lamella clarifier plate packs for industrial clarification equipment.

 A Met-Chem lamella clarifier can be equipped with an automatic sludge blowdown system.

The system can periodically open the sludge discharge valve and activate the sludge pump.

The timing is adjusted according to the amount of solids generated by the wastewater treatment process.

Automatic blowdown can:

• Reduce operator involvement
• Prevent excessive sludge accumulation
• Maintain available cone volume
• Provide consistent sludge removal
• Reduce the chance of solids reaching the plate pack
• Improve overall system consistency

During startup, sludge production should be monitored so the blowdown frequency can be adjusted for the actual application.

Lamella clarifiers are relatively simple mechanical systems, but proper operation and maintenance are still important.

Operators should periodically inspect:

• Plate packs
• Effluent weirs
• Sludge cone
• Sludge discharge valves
• Sludge pumps
• Mixers
• Polymer system
• pH controls
• Floc formation
• Effluent clarity

The plate packs should remain open enough for wastewater and solids to move through the channels as designed.

Excessive solids accumulation should be investigated rather than simply allowed to continue.

Possible causes include:

• Poor pH control
• Insufficient chemical precipitation
• Incorrect coagulant dosage
• Incorrect polymer dosage
• Poor floc formation
• Excessive hydraulic flow
• Excessive solids loading
• Sludge accumulation

The first step should be determining whether the problem is chemical or hydraulic.

Solids carryover may indicate that the clarifier is overloaded, floc is not settling properly, or excessive sludge has accumulated in the bottom of the unit.

Possible causes include poor sludge removal, excessive solids loading, inappropriate plate spacing, or solids that do not readily slide from the plate surfaces.

Increase sludge removal frequency rather than allowing the cone to remain full for extended periods.

 A properly designed Met-Chem lamella clarification system can provide:

• Large effective settling area
• Compact footprint
• 60-degree inclined plate design
• Approximately 50–60 minute retention time
• Integrated flocculation
• Automatic sludge blowdown
• Multiple construction materials
• Standard and custom flow capacities
• Integration with Met-Chem filter presses
• Complete wastewater treatment system capability

Most importantly, Met-Chem can evaluate the entire treatment process rather than selecting the clarifier based solely on a theoretical flow rating.

 Met-Chem designs and manufactures lamella clarifiers, inclined plate clarifiers, clarifier plate packs, filter presses, and complete industrial wastewater treatment systems.

Our goal is not simply to provide a tank with inclined plates.

The chemical treatment, flocculation, clarification, sludge removal, and dewatering processes must work together as a complete system.

If you are considering a new lamella clarifier, provide Met-Chem with as much information about your wastewater as possible, including:

• Average GPM
• Maximum GPM
• Hours of operation
• Wastewater source
• Suspended solids
• Dissolved contaminants
• Wastewater analysis
• Required discharge limits
• Existing chemical treatment
• Available floor space

Met-Chem can use this information to help determine the appropriate treatment process and clarifier configuration.

Contact Met-Chem for lamella clarifier sizing, equipment pricing, replacement plate packs, or a complete industrial wastewater treatment system.