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Solids Contact ClarifiersSolids Contact Clarifiers

E-mail : answers@smithandloveless.com • Phone: 913.888.5201 • FAX: 913.888.2173E-mail : answers@smithandloveless.com • Phone: 913.888.5201 • FAX: 913.888.2173S m i t h & L o v e l e s s I n c . S y s t e m I n n o v a t o r s f o r g l o b a l p u m p i n g , w a t e r a n d w a s t e w a t e r t r e a t m e n t

Understanding the Application of CLAR-I-VATOR® Solids Contact ClarifiersClarification and sedimentation involves several basic

approaches from a design and process point of view. Froma design angle, there are conventional center feed clarifiers,higher rate Lamella Separators and conventional clarifiersequipped with tube settlers.

From a process point of view, the achievement of sedimentationwith an economical use of chemicals, or where influentsuspended solids are relatively low for sedimentation unitoperations, or where a chemical reaction is taking place, isusually best achieved in one operation by the use of a solidscontact clarifier such as the Smith & Loveless CLAR-I-VATOR®.

From a design point of view, it’s desirable to create anenvironment where the settling time is minimized byshortening the settling distance yet minimizing turbulenceand short-circuiting. If this environment is achieved, it willoptimize clarification. In many instances, the use of chemicalsand flocculating techniques are not important so aconventional center feed clarifier will do the job. In somecases though, clarifier performance can improve, or space canbe limited in which the process is achieved either by using aconventional clarif ier equipped with tube settlers or aLamella-type separator equipped with plates. Both the tubesettlers and the plate separators essentially reduce turbulenceand shortening of the settling distance, thereby achieving thedesired results.

With chemical utilization, the concept of flocculation or thedevelopment of a more readily settleable particle becomes aconsideration; therefore, a flocculating clarifier which performsthe solids agglomeration step in one tank along withsedimentation may be preferred. Otherwise, a separate chemicaladdition and flocculating step will be required before theconventional clarifier, a clarifier equipped with tube settlers, ora Laminar plate-type settler.

However, a sludge blanket clarifier and a solids contact clarifiercan both perform the chemical conditioning function andsedimentation function in one tank, yet do it in a more effectivemanner than in the case of the flocculating clarif ier.(generally,there are always some exceptions to the rule).

In a sludge blanket clarifier, chemicals are added internallywith some form of flocculating mechanism such as a horizontalpaddle or a vertically mounted re-circulator. Chemicals are

added, the fluid mixed, and flocculation occurs in a particularzone of the tank. These materials are then directed toward thebottom and then will eventually rise towards the surface andform a sludge blanket. The sludge blanket exhibits a densitygradient where the particles closer to the bottom have a lessdiscrete form, and the particles near the top become discreteand increase in size where they eventually drop out of thesludge blanket and settle. It is by contact between a settlingparticle and the sludge blanket that sedimentation occurs.

This can be an efficient form of sedimentation. However, withthe sludge blanket clarifier, the device is readily upset byflow and process changes; if the sludge blanket is disturbedin any way, it will collapse, and the necessary exchangephenomena for removal by chemical means and bysedimentation due to growing and size of a particle will bealtered unfavorably.

A CLAR-I-VATOR® solids contact clarifier overcomes someof the problems exhibited in the sludge blanket clarifier. Itbasically controls the chemical reactions taking place,flocculation, and the sedimentation phenomena more positivelythan in a sludge blanket clarifier and is not as readily affectedby changes and flows or by process.

In the CLAR-I-VATOR® solids contact clarifier, the liquidstream enters into a central detention zone where chemicals

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The Smith & Loveless CLAR-I-VATOR® is a solids contact clarifier.

S M I T H & L OV E L E S S I N C.

® smithandloveless.comContact us via e-mail at answers@smithandloveless.com or through project inquiry at our website14040 Santa Fe Trail Drive • Lenexa, KS 66215 USA • Phone: 913.888.5201 • Fax: 913.888.2173

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continued from front sidecan be added. Within this zone, there is a re-circulator paddlewhich is activated by a variable speed drive. This paddlecreates a pressure differential within this zone and essentiallypumps previously settled material from a central settling coneinto the re-circulation zone and positively contacts it with theincoming waste. In so doing, the incoming waste can beflocculated with chemicals added at that point. The incomingsolids create a thermodynamically favorable environment tobring a chemical reaction to completion, conserve chemicalsand provide a more favorable settling characteristic to thesolid. These contacted materials are then brought into adetention zone where true flocculation can occur. At this point,the materials fall out and settle into the clarifier. It is not theintent of a CLAR-I-VATOR® solids contact clarif ier tomaintain a sludge blanket, although they are periodicallyoperated in that fashion.

In addition, to the enhanced settling characteristic imparted bythe CLAR-I-VATOR®, chemical reactions can occur and takeplace in a more ideal environment. Not only can we achievesimple sedimentation in an enhanced manner, but reactions suchas the removal of phosphates by precipitating calciumphosphate, or the removal of arsenic by the addition of iron in acomplexation reaction, can be maintained as well as others.Activated carbon could also be added to the CLAR-I-VATOR®

for absorption.

In summary, the CLAR-I-VATOR® solids contact clarifier canenhance sedimentation by improving the physicalcharacteristics of the material to be removed, can remove materialsby utilization of chemical reactions because of ideal reactingenvironment, can maximize the use of chemicals as previouslysettled material can be used as a source of these reactants andchemicals, and chemicals can be added in both the re-circulationand flocculating zones.

One other consideration should be made for use of a solidscontact clarifier over a conventional clarifier. Because of the

efficiencies described above, a CLAR-I-VATOR® solids contactclarifier might often use a smaller space than a conventionalclarifier. However, it is not uncommon to have relatively lowsolids concentration applications where conventionalclarification simply will not do the job. Typically, dependingupon the nature of the liquid to be treated, do not expect aclarifier to put out less than 10 PPM suspended solids — oftenthe range is 10 to 30 PPM. When treating a flow that has lessthan 200 PPM suspended solids, that’s demanding a lot in termsof percentage reduction with a conventional clarifier. In thesecases, chemical enhancement may be required — thus, a solidscontact clarifier can do a much better job.

When considering applications with several hundred orthousands of PPM suspended solids, the conventional clarifiermay be the better choice. In the case of low influent suspendedsolids, create an environment where sufficient particles contacteach other so that sedimentation can occur. Of course, if theparticles are sufficiently large and discrete that they settlerapidly, this is not a problem — but it is the exception, not therule. When re-circulated sludge contacts with an influent stream,a crystallization effect occurs where settleable material is created.This parallels the concept behind adding a chemical additivesuch as lime to an influent waste just for the matter of adding“weight” to the settleable material. Improving the settlingefficiency is the result.

In water treatment applications, the CLAR-I-VATOR® can beeasily applied because without the re-circulation and contactingof the solids, the high rates required for economy are notavailable for settling nor will the necessary chemical reactionsbe carried out very effectively.

There are a host of applications in water and wastewatertreatment that employ a variety of clarif ication andsedimentation techniques. However, in many cases, theCLAR-I-VATOR® solids contact clarifier is by far the moreefficient unit process available.

Flocculation ZoneEffluent Launder

Raw Water Inlet

Scraper ArmClarification Zone

Draft Tube(Mixing Zone)

Draft Tube Inlet Cone Recirculation ImpellerSludge Thickener

Flocculation Hood

Clarified Water Outlet

Variable SpeedRecirculation Drive

Scraper Drive