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Sludge treatmentEfficient solutions for wastewater treatment plants

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Handling large amounts of sludge is an expensiveand complex operation. As treatment plants becomelarger and more sophisticated, problems become evenmore complex and costly. That is why it is important tomake the right configuration and equipment choicesduring the initial planning stages. Flygt has the provenexperience and equipment that can provide reliable,efficient solutions for handling sludge in the treatmentprocess.

Efficient pumping

Depending on varying sludge characteristics, thecorrect duty point can be a difficult challange to meet.For environmental reasons, there is at the same time aneed to reduce the volume of sludge by thickening it.This too puts high demands on pumping ability.

The unique design of the N pump has proved veryeffective in general sludge treatment applications.Clogging-related downtime and subsequentmaintenance costs are being dramatically reduced andefficiency is being secured, thanks to Flygts solutions.

With the addition of a large range of ProgressiveCavity (PC) pumps we can offer a self-priming rotarydisplacement pump for challenging sludge situations.The design is very resistant to clogging and produces aconsistent, accurate flow.

Dependable mixing solutions

Submersible mixers are indispensable in the moderntreatment plant because they can be easily positionedand oriented to maximize efficient mixing in any sizetank. In thick sludge, good mixing results can beobtained by using the Flygt hydro ejector.

Most customers dealing with sludge treatment wanta pump/mixer solution or configuration rather than aspecific unit. Flygt's know-how in applications and fluiddynamics is the defining factor here.

Choose a reliable sludgetreatment solution

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A system tailored to

your needs

Cost-saving aeration systems

Aeration systems are in general very energy consuming.Therefore fine tuning of the system is essential.

For instance, the best choice can be the Flygt coarsebubble ejector, Flo-Get, because of its simplicity,

efficient mixing and good oxygen transfer in theaerobic sludge stabilisation processes. On the otherhand, the Sanitairerange of fine bubble systems withmembrane and ceramic discs offers an efficient andcomplete floor covered aeration system.

Systems engineering for optimal solutions

Flygt engineers can recommend and design the mostefficient system on the basis of data provided by thecustomer. We are able to predict accurate outcomesfor both pumping and mixing applications based onyears of research to define the behavior of sludge in

all aspects of treatment. This efficiency translate intolower operational costs in the long run.

With Flygt's global network of facilities, we are nearbyto assist in providing accurate and efficient solutionsfor any pumping, mixing or aeration problem.

Preventive medicine is the best cure

The consequences of systems failure are often drastic.If equipment in a biological treatment process breaksdown the restart can take weeks, involving potentiallyenormous costs. The same occurs when treatment

becomes non-functional due to equipment failure.This is why professionals turn to Flygt as the inventorand market leader of reliable system solutions.

Should problems arise, you can count on the Flygtservice network which reaches into more than 130countries around the world. And you never have to

worry about spare parts availability. We provide sparesfor a minimum of 15 years after manufacturing isstopped on a particular unit. The level of maintenanceand support required from us is always tailored toyour needs, on your terms.

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Sludge treatment

1. Removal ofprimary sludgeSettable solids arepumped to the sludgetreatment.

2. Removal of secondary sludge (RAS & WAS)Return activated sludge (RAS) is continuously pumpedback to the reactor. An excess part of the settled sludge,waste activated sludge (WAS), is pumped away forfurther treatment.

3. Pumping of imported sludgeSludge from septic tanks, industries andother wastewater treatmant plants isbrought to a storage tank. Then it ispumped to the sludge treatment or to theplant inlet.

As wastewater plants becomelarger and more sophisticated, thedemands for cost-effectiveness andreliability grow too.

In order to apply the correctsolution, it is essential to understandthe requirements of each individualplant. This is why we do not sell onestandard solution, but offer a widerange of customised applications, to

ensure optimisation.

The plant shown here is a compositeillustration of sludge treatment withanaerobic digestion as stablilisation.It explains how our products can beused in numerous applications.

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6. Pumping of mechanically thickened sludgeThe dry solids content and the viscosity of the further thickenedsludge can become very high and may hardly be poured out ofa bucket. This puts high demands on the pump.

7. Mixing in the anaerobic digesterTo achieve a large active reactor volume in the stabilisationprocess, efficient mixing is required.

4. Withdrawal of gravity thickened sludgePrimary, secondary and imported sludge is thickenedseparately or mixed. The character of the thickened sludgediffers widely and pumps have to be choosen depending onorigin and possible addition of polymers.

5. Crushing of solids in sludgeTo avoid clogging and wear of mechanicalunits the macerator takes care of ragsand fibers that have managed to passthrough the screens.

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11. Pumping of dewatered sludgeWhen the sludge has been dewatered, the drysolids content is very high which requires a lotfrom the pump for further transportation.

9. Mixing of stored sludgeTo avoid settling in the storagetanks, mixers are required.

10. Pumping of stabilised sludgeThe sludge is fed to the dewatering unit bypumps suitable for the installed dewateringunit.

12. Dosing of polymerAs polymer has been prepared, itis pumped to the thickening anddewatering units.

8. Recirculation of sludge in theanaerobic digesterTo keep the biological process alive in the digester,the temperature has to be kept elevated by re-circulating the sludge through a heat exchanger bypumps.

13. Removal of reject waterFrom mechanical thickeners andcentrifuges, the reject water is collectedand pumped away for treatment.

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1. Aerobic stabilisation

Conventional aerobic digestion is performed at theambient temperature where both intermittent andcontinuous feeding is seen.

Auto-thermal thermophilic aerobic digestion (ATAD)can be achieved with a properly thickened sludge, andinsulated tanks, where a temperature of 60 C can bereached.

For both processes an efficient aeration and mixingfor a long period of time is required to achieve thedesired degree of solids stabilisation and pathogeninactivation.

Alternative stabilisation processesStabilisation is the process of converting organic matter in the sludge into stable products that are resistantto further biological activity.

In the picture of the treatment plant on the previous page, anaerobic digestion is used as a stabilisationprocess. However, there are also other ways of stabilising sludge:

2. Lime stabilisation

Lime is added to the untreated sludge in sufficientquantities to raise the pH to 12 or higher. The high pHcreates an environment that makes it impossible formost micro-organisms to survive. Consequently, thesludge will then not have any biological activity, norpose a hygenic risk as long as the pH is maintained atthis level.

This requires good mixing and proper equipment forsuch a tough and demanding environment.

De-sludging as an alternative treatment

When using aerated, facultative or anaerobic lagoonsfor wastewater treatment, the lagoons will eventuallyhave to be de-sludged. De-sludging is achievedeither by pumping or excavation. When pumping theapplication puts high demands on pumps because ofthe high amount of grit and rags, as no de-gritting orscreening of the water is performed.

De-sludging is also considered when sludge-lagoonsare full and for some reason must be emptied.

Flo-Get Mixer

Hydro ejector

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Our wide range of solutions and equipment for sludgetreatment ensures that you will get the best resultswhether upgrading and refitting an older installationor designing and constructing a new one. Theequipment will perform efficiently, require minimum

maintenance and offer the lowest possible cost overthe life of the application.

N-pumps

This range of units can be usedpractically everywhere in sludgetreatment for transporting water aswell as sludge of all types (beforedewatering). This type of pump canbe operated either submerged on adischarge connection with guide barsor non-submerged on a stand in a drypit. N-pumps can handle dry solidscontents up to at least 6%.

Progressive cavity pumps

Our range of PC pumps includes polymer dosingpumps and sludge pumps where the hopper pumpcan handle up to 45% dry solids content. Dependingon the application, we can supply pumps with stators

of different geometries, to provide low noise levels,low risk of clogging and stable flow characteristics.

The PC pumps can handle viscosities up to 1,000,000mPas (cP).

Hydro ejector

The hydro ejector is a liquid jet generating ejectorwhich creates a powerful bulk flow. The hydro ejectorconsists of a cast iron nozzle that can be used byitself or together with a stainless steel ejector pipe.It is available in three sizes and is designed to fit theFlygt N-pump series.

Meeting your specific needs

when building or upgradingan installation

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Macerator

To avoid clogging problems and disturbance in thesludge-treatment processes, a macerator can be fittedupstream of a PC pump. This grinding device crushesrags and fibres into manageable sizes for pumping in

liquid. Solids including wood, textiles, plastic, boneand fur are crushed by the rotating impeller againstthe fixed cutting ring.

The crushing stages result in grain sizes down to 3.5mm or fibre sizes of 1.5 cm2, depending on type ofsolids.

Compact mixers

Our range of compact mixersprovides cost-efficient mixingsolutions for solids suspensionand sludge blending. These

direct drive, stainless steelmixers have motor capacitiesof up to 30 kW (40 hp) anddeliver thrust up to 7000N.Various propeller angles areavailable for optimised duty.The optional jet ring can reducepower consumption still further, byup to 15%.

Aeration systems

We offer a wide range of efficient aeration products

that fulfil a variety of oxygen requirements inwastewater applications.The Flygt Flo-Get ejectoroperates together with a submersible pump, and isthe natural choice where flexible and reliable aerationis essential. The Flo-Get provides efficientaeration combined with good mixing. Thealternative Sanitairesystem has a uniformair distribution, using pressurised air throughhigh porous discs mounted on pipes attachedto the tank floor.

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Everything you need for reliable processpumping solutions

As the worlds leading manufacturer of submersiblepumps and provider of fluid handling technology,Flygt can provide you with complete pumping

solutions. From planning and delivery, throughinstallation and after sales service, Flygts competenceis at your service.

Through our products and services, engineers,planners and consultants have access to more than100 years of experience, assuring the most reliableand cost-effective operation. Flygt service and salesfacilities are found in more than 130 countriesworldwide.

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