Degrémont Water Treatment Handbook Factsheets N°2 - Compakblue


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The Degrémont Compakblue process is an immersed disc filter recommended for the abatement of SS and the associated pollutants in tertiary filtration of urban waste water, as an alternative to filtration on granular media. This process is particularly adapted to reuse or discharge in sensitive zones.

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Degrémont Water Treatment Handbook Factsheets N°2 - Compakblue

  1. 1. Degrémont has a tradition of sharing its Degrémont Water Treatment employees’ passion for water treatment with Handbook Factsheets the public. To supplement the Water Treatment Handbooks, Degrémont has issued the «Handbook Factsheets» to promote a better understanding of the different techniques available and discovery of the new products and major technological changes. Re-use CompakblueTM Wastewater Tiertiary Clarification Mechanical filtrationISSUES OF WATER RE-USEPopulation growth, water stress and unequal distribution ofwater resources are all factors that induce many countries touse new supply sources to meet their demand for water.In this context, wastewater can undergo prolonged use or be Irrigate Cultivate Clean Restock Sprinkle Produceused to reconstitute resources. Rather than being dischargedinto the natural environment, it is treated and cleaned to be re-used (re-use). PHYSICAL PRINCIPLES OF FILTRATION Filtration consists of separating a liquid phase from a solid phase by means of a mechanical barrier. That barrier, called a filter, has sufficiently small meshes to retain solids and let the liquid pass through. Three principal mechanisms intervene successively: capture, fixation and detachment. Their importance depends on the characteristics of the particles to be retained and the filtering material that is used. The solid particles contained in a liquid and the more or less flocculated colloidal particles do not have the sameÎÎ Prolong water uses characteristics and do not react in the same proportion to these various mechanisms.In regions where water quantities are regulated, while agricultural,urban or industrial needs are substantial, re-use will relieve the ÎÎ Capture mechanismtraditional resources by fostering a reduction in water drawnfrom natural resources. This primarily takes two forms: • echanical screening: occurs when are retained the mÎÎ Reconstitute the natural resource particules larger than the mesh of the filter or larger than the elements already deposited, these last ones formingIn regions where natural resources are drying up, regeneration themselves a filtering material. The finer the mesh of theof wastewater can accelerate the natural cycle and be used to filtering material is, the greater this phenomenon is: it is ofreplenish aquifers or reconstitute water reserves. little importance for a filter bed composed of relatively coarse material. However, it is preponderant in filtration on a fineÎÎ Preserve the environment support: screen, filtering sleeve… • eposit on filtering material: the particle in suspension dIn regions where tourism is the main economic activity, re-use follows a current line in the liquid; its size compared to that ofwill help to preserve the natural setting of tourist sites because the pores, could enable it to cross the filtering material withoutthere will be no discharges. being stopped and yet, at the time of its tortuous trajectory in the bed, particle/material contacts will cause it to be captured.Many countries, and particularly those that are experiencing the That is a very important mechanism in in-depth filtration.greatest water stresses, have set up standards or regulations toincrease the re-use of cleaned wastewater. ÎÎ Fixation mechanism The fixation of the particles on the surface of the filtering material is fostered by a low flow rate that is due to forces of physical origin (wedging, cohesion, etc.) and forces of adsorption, primarily Van der Waals forces.
  2. 2. ÎÎ etachment mechanism DUnder the action of the two preceding mechanisms (capture and CompakblueTMfixation), there occurs a reduction in space between the wallsof the material covered by particles already deposited. There isthen an increase in the rate of intergranular flow, that furtherson in the filtering material (progression of the “filtration front”)or even in the filtrate (“breakthrough”) the deposits alreadycaptured, which can be partially detached.CLOGGING AND WASHING OF FILTERINGMATERIAL ÎÎ Presentation of the processClogging refers to the gradual obstruction of the interstices of thefiltering material. Clogging causes an increase in head loss and, if The Degrémont CompakblueTM process is an immersedthe supply pressure remains constant, a drop in the flow rate of disc filter recommended for the abatement of SS and thethe filtrate (declining-rate filter). associated pollutants in tertiary filtration of urban waste water, as an alternative to filtration on granular media. This process isTo function with constant flow, it is necessary to: particularly adapted to reuse or discharge in sensitive zones.• ither increase the pressure applied to the filtering bed as the e clogging occurs (e.g., “constant rate variable-head” filter); Principle of filtering discs• r keep that pressure constant and place a regulation system o at the outlet of the filter that exerts an additional head loss, which decreases as the bed clogs. These so-called “clogging compensation” filters are used in water treatment.The clogging speed depends on:• he matter to be captured: the more loaded the liquid is with t suspended solids (SS), the greater the cohesion of those solids is and the more susceptible they are of proliferating (algae, bacteria), then the greater the clogging will be; CompakblueTM is a mechanical constant rate variable-• the filtration speed; head filter. Filtration is done by filtering materials mounted on• he characteristics of the filtering element: size of the t plastic supports. pores, homogeneity, roughness, shape of the material. In the filtration cycle, water crosses the filtering material of the discs, which capture the SS once their size is greater thanThe filter is clogged when it has reached the maximum head 8 μm. Depending on the intended use, it is possible to chooseloss planned by the manufacturer. It is then important to restore a type of filter and cloth with a wider cut off. The filtrate thenit to its initial state by an effective washing; the wash method returns to the output channel of the facility through the supportis related to the type of filter and the nature of the elements tube of the discs.captured. The operating time elapsed between two successive It is a mechanical constant rate variable-head gravity filter withwashings is called a filtration cycle. no level regulation. During operation of CompakblueTM, with no interruption inCHOICE OF FILTRATION MODE filtration, part of the filtering material is automatically washed at regular intervals by suction or water jet, depending on theThe choice among the various types of filtration on support or version installed, with no chemical reagents. During filtration,granular bed depends on several criteria: the level of filtered water downstream is constant while the• haracteristics of the liquid to be filtered, its impurities and their c level of water to be filtered upstream rises as clogging occurs. change over time; Washing starts when it rises above a water mark level upstream• quality of the filtrate to be obtained and tolerances allowed; or by timer.• installation conditions; The specificity of CompakblueTM lies in the standardization of its• capabilities and means available for washing. manufacture and its compactness. It is available in two versions: a version with filtration by micro-strainer, developed byThe possibility of an easy, effective and economic wash is as Nordic Water, and a version by cloth filtration, developed byimportant in the choice of the filter as obtaining the best filtration Mecana.quality. The filtration quality is preserved over time only if thewash makes it possible to restore the characteristics of a clean • iltration on micro-strainer (Nordic Water) Ffilter at the start of each cycle. The water to be filtered enters the central cylinder, then the discs and crosses the filter media affixed onto the faces of the discs. Filtration is In/Out: it is done from the inside towards the outside of each disc. The entire unit is partially immersed in a tank made of concrete (standard version) or steel (for smaller plants).
  3. 3. Degrémont Water Treatment Handbook Factsheets treatment and a secondary clarifier.Filtration is done continuously; there is no stoppage during the • Compactnesswash. The principal asset of this technology is the compactness, madeThe slurry water resulting from the wash is collected in a chute possible by the use of the filtering media. It offers performance similar to traditional filtration on granular media for a footprint one quarter its size. • Set-up and assembly The slight head loss of CompakblueTM facilitates its set-up in a treatment system. It is generally not necessary to lift the effluent to be filtered in order to feed the filter. CompakblueTM is delivered fully assembled; it is easily installed in the facility.inside the central cylinder.This version is adapted for installations of 40 to 9,000 m3.h-1• Filtration on cloth media (Mecana Umwelttechnik AG)Each filtering disc 2.1 m in diameter is covered with a specificcloth media. Filtration is Out/In, from the outside towards theinside of the discs. The filtered water is recovered in a collectorattached to the discs.Each filter can be equipped with 2 to 15 discs. • Simplified operationCompletely immersed in a tank, the process avoids biological Since the design of the filters is simple, the operation requires nodevelopment on the fabrics. special attention. The washing system is activated by the variation in the level in the tank. Thus, the daily operation is reduced. ÎÎ Performance The quality of the water produced allows re-use or discharge in sensitive zones. The water cleaned by CompakblueTM has a helminth egg content lower than 0.1 per liter, in compliance with WHO recommendations. Treatment goal Abatement of SS and particulateThe washing of the discs is very brief and pollutionfrequent. It is done disc by disc. During the Secondary clarifier SS 35 mg.L-1washing procedure, the fibers are briefly exitstraightened in the suction device, so thatthe selected solids are easily evacuated. Water treated after • Mecana: between 3mg.L-1 of SS on The filtration is done continuously; there is CompakblueTM average (6 in 95%ile) and 5mg.L-1no stoppage during the wash. of SS (10 in 95%ile) • Nordic Water : 5 mg.L-1 of SS on This version is adapted for installations of average (10 in 95%ile)70 to 9,000 m3.h-1ÎÎ Implementation ÎÎ Sustainable development• CompakblueTM in the system The CompakblueTM solution is energy-efficient. It uses no pumpIn a treatment system, CompakblueTM is placed after a biological for its supply, no tank, no air blower, or pump of reagents for cleaning the discs. The process does not require chlorination and does not require any chemical reagent for its cleaning.
  4. 4. Degrémont Water Treatment Handbook FactsheetsA few Degrémont REFERENCES• Caleppio di Settala (Italie) (capacity 2,000 m3.h-1) • Palmela Terciaro (Portugal) (capacity 900 m3.h-1)• Auxi-Le-Château (France) (capacity 60 m3.h-1) • Pavia (Italy) (capacity 3,200 m3.h-1)• Le Moule (Guadeloupe-France) (capacity 250 m3.h-1) • Sacy-le-Grand (France) (capacity 40 m3.h-1)ÎÎ Filtration on micro-strainer• ocus on the wastewater treatment plant in Lagoinha (Portugal) 30,000 PE, which will be operational in 2012 FDischarge in sensitive zone - Treatment line = aeration ditch - secondary clarifier - CompakblueTM filter - UV disinfection from Ozonia - 2 filters with 8 filtration discs on micro-strainer - Diameter of discs = 2.40 m - Total filtering surface = 89 m² - Treated flow = 700 m3.h-1ÎÎ Filtration on cloth media• Focus on the wastewater treatment plant in Auneuil (France) 4,400 PE, operational since 2010Discharge in sensitive zone - Treatment line = activated sludge tank – secondary clarifier – CompakblueTM filter - 1 filter with 2 cloth filtration discs - Diameter of discs = 2.20 m - Total filtering surface = 10 m² - Treated flow = 100 m3.h-1 Feuillets Mémento Degrémont n°2 - Juillet 2011 - Crédit photos : Degrémont, Mecana, Nordic Water Contact: CompakblueTM : DEGRÉMONT S.A. WWW.DEGREMONT.COM