Lamella Clarifiers Versus Conventional Clarifiers for Wastewater Treatment Plants?
Published on by Michael Haig in Technology
Why would the majority of activated sludge treatment works employ conventional clarifiers as opposed to lamella clarifiers?
Is it merely the limitation of the incoming solids concentration being too high for lamella use or are there other process or maintenance challenges?
Taxonomy
- Solid Waste Treatment
- Treatment Methods
- Industrial Wastewater Treatment
- Sludge Treatment
- Waste Water Treatments
- Wastewater Treatment
- Water Treatment Solutions
- Waste Water Treatment
- Clarifier
8 Answers
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Followings are few reasons
MLSS in activated sludge is biomass.
It settles as zone.
It does not slide down easily in inclined tube or plate.
After some time surface of Tube or plate may promote attached growth which will further hinder the sliding down of the sludge.
Sludge draw for circulation can cause turbulence in the Lamella.
Rajendrakumar V Saraf
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Lamella tubes and plates can only be used as a supporting agent in case of troubleshooting like shock load.. However I found that many vendors use the surface area of lamella plates in the calclulation of Surface Overflow rate (SOR), which is the key design parameter in Secondary clarifier design.
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Well, when we think of Secondary clarifier, it is always the Conventional clarifiers and the reason being the MLSS volume and The conventional clarifier are to be designed based on the solids loading rate, and solids needs plan area, it cannot be replaced with tubes/plates. Hence its always the conventional clarifiers, further, if we provide Lamella clarifier then we need to realize that there would be a greater upward thrust because of the biomass and the MLSS and plates/tubes get easily lifted up, and hence poor clarifications. Lamella can be used when we are treating phosphorous chemically, as a tretiary clarifier as the phosphorous loading will always be on the lower side and Lamella can still maintain the same.
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Primary reason is high concentration of incoming solids. If the sludge removal is not able to match the removal of separated solids then the unit goes solids critical and results in carry over of floc. However at some places Lamella and Tube Settlers are adopted for conventional process too. It is observed that short length settlers (Tubes with length of 600 mm and 60 degree inclination) do not have much problem with biomass growth.
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lamellae are a good option for upgrading = increasing capacity, without civil works, mostly in hopper type clarifiers, or if not sufficient space is available for conventional design settling, like in industries. But they need some maintenance: regular water jet cleaning. Covering against light helps to reduce biological growth.
1 Comment
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Can you give the figure like at what % we can increase the capacity?
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There are two considerations that work against the notion of using lamella plates or tubes in activated sludge secondary clarifiers. The primary concern is that bacteria and biofilms will grow on the lamella surfaces, both impeding flow (plugging) but also creating the potential for anaerobic activity in the attached biofilm that can release methane and H2S. The methane bubbles may attach to the solids which would tend to float, causing a deterioration in effluent turbidity. H2S is a concern primarily for odors.
Another concern is that the high concentration of mixed liquor suspended solids from the aeration zone may exceed the maximum concentration that lamella plates could handle. Perhaps the best candidate for addressing this issue is a configuration similar to what is used in the Suez Superpulsator for water treatment, i.e. deep, widely spaced, lamella plates. Lamella tube settlers for polishing on top of lamella plates below for bulk solids separation may be the best approach, if the biological growth problem can be solved.
The biological growth problem possibly could be solved by impregnating the lamella surfaces with "quorum sensing" disruption chemicals that interfere with biofilm formation, thus preventing biogrowth on the surface. Such chemicals are used in surgical instruments and its been a topic in water and wastewater discussions for at least 15 years.
2 Comments
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I tend to agree with this comment, biofilm development attaching to the lamella plates in biological treatment processes, and particularly those with high sludge yield, tend to get clogged with biomass growth or high sludge accumulation
accurate and regular desludging therefore becomes critical,
seems to be less of a problem on RBC installations where sludge production is less, therefore less solids load
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Joseph,
I think this is the best explanation given as to why a Lamella style clarifier is not utilized in biological treatment units. I have personally seen a lamella clarifier clog with debris and biological growth on an INFLUENT water stream that did not dose bleach into the raw river water it was treating. The spaces between the plates and tubes are perfect environments for bacteria to attach and grow even without mixed liquor flowing through them. You add that to the mix and the plates will plug so rapidly that I do not know if you will ever get proper flow through them
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The resoonses to date date provide a description of the technology, but not of its use. The primary reason for the continued use of sedimentation basin clarifies versus Lamella clarifies is cost. Lamella clarifies can also be operationally problematic if the separated solids do not pass out of the plates but, instead, clog the system and interfere with hydraulic conditions - reducing separation efficiency.
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A lamella clarifier or inclined plate settler (IPS) is a type of settler designed to remove particulates from liquids. They are often employed in primary water treatment in place of conventional settling tanks. They are used in industrial water treatment . ... The inlet stream is stilled upon entry into the clarifier .A lamella clarifier also typically known as an inclined plate clarifier is designed to remove particles from liquids. They are usually employed in the primary water treatment such as places with conventional settling tanks. They are also used in industrial water treatments. Unlike the conventional clarifiers, they utilize a series of inclined plates. These inclined plates seemingly provide a large effective setting area for a relatively small foot print. The inlet stream is stilled upon entry into the clarifier. Solid particles will then begin to settle onto the plates and begin to accumulate in collection hoppers at the bottom of the clarifier unit. The sludge is then drawn off at the bottom of these hoppers and the clarified liquid proceeds to exit the unit at the top by the weir.
https://thewaternetwork.com/question-0-y/lamella-clarifier-design-hgUf9JFJ9NPUeYB4CbGTDA