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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Re-use
CompakblueTM
Wastewater Tiertiary Clarification Mechanical filtration
ISSUES OF WATER RE-USE
Population growth, water stress and unequal distribution of
water resources are all factors that induce many countries to
use new supply sources to meet their demand for water.
In this context, wastewater can undergo prolonged use or be Irrigate Cultivate Clean Restock Sprinkle Produce
used to reconstitute resources. Rather than being discharged
into 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 same
ÎÎ 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 mechanism
traditional resources by fostering a reduction in water drawn
from natural resources. This primarily takes two forms:
• echanical screening: occurs when are retained the
m
ÎÎ Reconstitute the natural resource particules larger than the mesh of the filter or larger than
the elements already deposited, these last ones forming
In regions where natural resources are drying up, regeneration themselves a filtering material. The finer the mesh of the
of wastewater can accelerate the natural cycle and be used to filtering material is, the greater this phenomenon is: it is of
replenish aquifers or reconstitute water reserves. little importance for a filter bed composed of relatively coarse
material. However, it is preponderant in filtration on a fine
ÎÎ Preserve the environment support: screen, filtering sleeve…
• eposit on filtering material: the particle in suspension
d
In regions where tourism is the main economic activity, re-use follows a current line in the liquid; its size compared to that of
will help to preserve the natural setting of tourist sites because the pores, could enable it to cross the filtering material without
there 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 to
increase 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. ÎÎ etachment mechanism
D
Under the action of the two preceding mechanisms (capture and
CompakblueTM
fixation), there occurs a reduction in space between the walls
of the material covered by particles already deposited. There is
then an increase in the rate of intergranular flow, that furthers
on in the filtering material (progression of the “filtration front”)
or even in the filtrate (“breakthrough”) the deposits already
captured, which can be partially detached.
CLOGGING AND WASHING OF FILTERING
MATERIAL
ÎÎ Presentation of the process
Clogging refers to the gradual obstruction of the interstices of the
filtering material. Clogging causes an increase in head loss and, if The Degrémont CompakblueTM process is an immersed
the supply pressure remains constant, a drop in the flow rate of disc filter recommended for the abatement of SS and the
the filtrate (declining-rate filter). associated pollutants in tertiary filtration of urban waste water,
as an alternative to filtration on granular media. This process is
To 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 than
The filter is clogged when it has reached the maximum head 8 μm. Depending on the intended use, it is possible to choose
loss planned by the manufacturer. It is then important to restore a type of filter and cloth with a wider cut off. The filtrate then
it to its initial state by an effective washing; the wash method returns to the output channel of the facility through the support
is 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 with
washings is called a filtration cycle. no level regulation.
During operation of CompakblueTM, with no interruption in
CHOICE OF FILTRATION MODE filtration, part of the filtering material is automatically washed
at regular intervals by suction or water jet, depending on the
The 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 by
The possibility of an easy, effective and economic wash is as Nordic Water, and a version by cloth filtration, developed by
important in the choice of the filter as obtaining the best filtration Mecana.
quality. The filtration quality is preserved over time only if the
wash makes it possible to restore the characteristics of a clean • iltration on micro-strainer (Nordic Water)
F
filter 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. Degrémont Water Treatment Handbook Factsheets
treatment and a secondary clarifier.
Filtration is done continuously; there is no stoppage during the • Compactness
wash. The principal asset of this technology is the compactness, made
The 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 specific
cloth media. Filtration is Out/In, from the outside towards the
inside of the discs. The filtered water is recovered in a collector
attached to the discs.
Each filter can be equipped with 2 to 15 discs. • Simplified operation
Completely immersed in a tank, the process avoids biological Since the design of the filters is simple, the operation requires no
development 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 particulate
The washing of the discs is very brief and pollution
frequent. It is done disc by disc. During the Secondary clarifier SS 35 mg.L-1
washing procedure, the fibers are briefly exit
straightened in the suction device, so that
the 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-1
no 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-1
ÎÎ Implementation ÎÎ Sustainable development
• CompakblueTM in the system The CompakblueTM solution is energy-efficient. It uses no pump
In 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. Degrémont Water Treatment Handbook Factsheets
A 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
F
Discharge 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-1
ÎÎ Filtration on cloth media
• Focus on the wastewater treatment plant in Auneuil (France) 4,400 PE, operational since 2010
Discharge 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 : innovation.mailin@degremont.com
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