Ultragreen is a Degrémont wastewater treatment process that combines pollution degradation with biological activity and clarification by ultrafiltration flatsheet membranes.

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.
Urban WasteWater
UltragreenTM
Biological process Clarification Membrane filtration
MEMBRANE CLARIFICATION OF URBAN treated water is not dependent on changes in hydraulic heads.
WASTEWATER Flux
During membrane clarification, at
constant concentration and pressure, a
Re
Similar to water treatment procedures to produce drinking water,
ve
r
sib
flux reduction can occur over time, which
l e
the membrane separation technique used in urban wastewater
flo
w
can lead to the complete blocking of the
los
treatment is a real physical barrier to impurities and pathogenic
s
germs. membrane: a phenomenon known as
To achieve the same water quality objective, membranes can be clogging. Backwash
used to replace several stages of conventional treatment. The Time
compactness of membrane processes allows the construction Clogging is due to the formation of a colloid deposit on the
of small-sized plants and modular processes can be installed in membrane surface, the adsorption of varied solutes in the pores,
a wide range of plant sizes. but also the formation of precipitates on the membrane (ferric
sulphate, for example). The former is essentially reversible by
means of backwashing (operation that entails reversing the
ÎÎ Ultrafiltration membranes
pressures to send the produced water through the membrane
and loosen the deposit) or by a surface sweep («relaxation»)
Any material that has a thin film shape (0.05 mm to 2 mm) and
of the membrane without filtration. However, backwashing
the property of providing selective resistance to the transfer of
or increased sweep speed has often no effect on adsorption
different constituents of a liquid or gaseous fluid is a membrane
or the formation of precipitates; only an appropriate chemical
that can be used to separate elements (particles, solutes, or
treatment will then «clean» the membrane.
solvents) present in a fluid.
Ultrafiltration membranes, with pore sizes between 1 and
100 nm, allow mineral salts and organic molecules of small ÎÎ Membrane structure
molecular weight to pass; they stop only the largest solutes
(macromolecules) and specific elements such as viruses, In ultrafiltration membrane separation, the separation units,
bacteria, and colloids. They ensure the total elimination of called «modules», that are used in membranes are designed to
suspended solids (SS) that cause turbidity without modifying the attain two essential goals:
salt composition of the water. - roup the membranes together into compact modules, that
g
is, to provide a maximum exchange surface per unit volume;
- nsure sufficient circulation of the liquid to be treated to the
e
membrane in order to limit particle deposits.
In the case of wastewater clarification, there are two main types
of modules:
Air Permeate
• Hollow fibre membrane modules inlet oulet
Hollow fibres, with a diameter of 0.6
to 2 mm, are produced by extrusion of
This process leads to high rejection rates that meet the strictest membrane material through annular dies.
regulatory requirements, particularly for «bathing water» Their structure allows them to stand up to
(European directive) and allows anticipation of future the internal or external pressures required
changes. for their use. These fibres are then grouped
The physical barrier created by membranes makes it possible into modules that are easy to backwash.
to control filtration and the quality of rejected suspended solids, During wastewater treatment, the fluid to
contrary to dynamic separation in a clarification tank where there be treated circulates outside of the fibres
is always the possibility of a «leak» from suspended solids, and and the permeate is collected at one or Vertical fibre
therefore the risk of denitrification. In addition, the quality of the both ends of the fibres. The modules are Air outlet
bundle

2. directly immersed in the water to be treated, and the filtrate
sucked through the fibre by being placed under a partial vacuum Classical activated sludge line
(0.2 to 0.6 bar, or 20,000 to 60,000 Pa).
Raw
water
Pretreatment Activated sludge Clarifier Sand filter Disinfection
• Flatsheet membrane modules
In this case, the membrane Membrane Membrane Bio Reactor (MBR)
support plate
presses down on the two Treated water
Membranes
(to suction intake) Permeat
sides of a planar structure Drainer Raw
serving as the central plate water
«process» «membrane»
Excess sludge
Pretreatment
support. The fluid to be Felt air air
treated circulates through the Permeat
outlet Membrane
membranes of two adjacent
UltragreenTM
PLATE
plates. The liquid layer
between the plates is about MODULE
7 mm thick. The permeate is
collected under a vacuum in the grooves of the plates. The plates
provide mechanical support to the membranes and drainage
of the permeate. The plates supporting the membranes are
also assembled in compact modules. The arrangement of the
modules allows parallel circulation. Accordingly, groups of units
of up to 140 m2 surface area can be formed.
ÎÎ pplication of Membrane BioReactors (MBR)
A
Ultrafiltration membranes can replace suspended or attached ÎÎ Presentation of the process
growth, aerobic or anaerobic clarifiers to separate flocs and non-
flocculated bacteria from treated water. Ultragreen™ is a Degrémont wastewater treatment process
The application of Membrane Bioreactors allows the that combines pollution degradation with biological activity
combination of pollution degradation through biological and clarification by ultrafiltration flatsheet membranes.
activity and thorough filtration in the compact units. In addition
to its exceptional rejection quality, the highly compact size of After straining through a fine mesh, the water to be purified
MBR units is a decisive advantage for this technology, especially is sent to a reaction tank where it enters into contact with a
in situations of overwhelming location and civil engineering purifying bacterial mass. The membranes are immersed into the
problems. biological liquor in a separate tank. The biological liquor is filtered
by suction through the ultrafiltration membranes with the use of
a pump or simply through the hydraulic head on the membrane.
MBR clarification has the following advantages:
The membranes thus replace traditional clarification
• he certainty of obtaining perfect clarification regardless
t and any tertiary filtration. The biological liquor is circulated
of the state of the sludge and its sludge index since the between the two tanks.
membranes can retain even non-flocculated bacteria and
produce an effluent with no suspended material (turbidity Ultragreen™ works by cycles of filtration/relaxation.
1 NTU);
• he disinfection of the effluent (absence of pathogens such as
t
helminthes eggs, bacteria, or certain viruses;
• he possibility of increasing the concentration of purifier
t
biomass between 6 and 12 g.L-1 (since the clarifier is no longer
needed). This therefore causes, at equivalent mass load, the
possibility of reducing the aerator by a factor of 2 to 4 with
respect to a traditional aerator in activated sludge;
• he absence of a clarifier and a small-sized aerator means
t
lower civil engineering cost and much smaller footprint;
• he membrane blocks the passage of certain macromolecular
t The Ultragreen™ membranes have
metabolites which leads to their gradual degradation, resulting
a cutoff threshold of 0.08 µm, which
in a significantly lower final COD (chemical oxygen demand)
makes them a powerful physical
than that which is obtained by traditional activated sludges.
barrier for eliminating bacteria,
helminthes eggs and for reducing
fecal coliform. The quality of the
treated water is excellent in terms of
suspended solids and turbidity.

3. Degrémont Water Treatment Handbook Factsheets
The membranes They are assembled Ultragreen™ up during clarification. Compared to the traditional activated
used in this in modules. The functions by sludge, the required reactor volume is reduced by 50% at least,
process are assembly can be suction on the because of the high sludge concentration;
mechanically horizontal and/or principle of Out/ • he high concentration of suspended solids has an unfavourable
t
reinforced vertical. The vertical In filtration, that is, influence on oxygen transfer. This leads to a specific electrical
flatsheet two-module assembly via filtration from consumption, expressed in kWh.kg-1 BOD, obviously higher
membranes leads to optimum the outside of the than conventional activated sludge;
manufactured by unclogging aeration. plate towards the • ltration within the tank containing the modules causes an
fi
TORAY. inside of the plate. overconcentration of the mixed liquor. The latter should be
controlled by continuous recirculation from the tank where the
modules are immersed in the aerobic and/or anoxic tank. The
recirculation rate is normally set between 200 and 500% of feed
flow.
ÎÎ Performance
The sizing calculated to ensure thorough nitrification also leads
to very low concentrations of COD, BOD, and N-NH4.
Filtration is done by suction, by action of a transmembrane
The table below is a summary of the expected values with this
pressure of less than 0.2 bars. Continuous aeration («membrane
type of urban wastewater facility.
air» function) creates a flux of ascending air along the plates, and
generates a mixed solution current in the area.
Parameter Concentration
As a curative measure, the membranes are regenerated one to Suspended Solids (mg·L–1) 2
three times a year by a regeneration washing.
This involves injecting a chemical solution into the membrane Turbidity (NTU) 1
pocket; leaving the solution to act for 2 to 4 hours, then rinsing COD (mg.L ) –1
50*
the membrane by filtration.
BOD (mg.L ) –1
8
ÎÎ Implementation N-NH4 (mg.L–1) 1
NT (mg.L )
–1
10
Ultragreen™, like most membrane bioreactors is characterized
Escherichia Coli (number per 100 mL) 100
essentially by:
• highly concentrated mixed liquor of 8 to 10 g.L-1, which
a * depends on the hard COD of raw water
allows a significant gain in reactor volume;
• he presence of membranes immersed in the mixed liquor.
t Ultragreen™ is appropriate for treating urban and industrial
waste water and helps to obtain an effluent that can meet
These specific features require certain precautions and/or the most stringent waste standards in sensitive or very
constraints on the design and sizing of this type of facility. sensitive environments. Generally Ultragreen™ guarantees the
bathing water quality (European directive). The effluents can
• Pretreatment be recycled for reuse.
This is a fundamental stage for the proper functioning of the In addition, because of the small size of the basic element
filtration unit. comprising the membrane system, its flexibility, and modularity,
Straining is required to supplement careful degreasing and Ultragreen™ is ideal for small plots of land and can also be
desanding. The minimum required is filtration through a grid with easily integrated into an existing plant.
a hydraulic diameter of 2 mm.
• Biological reactor
The configuration of the reactors remains, with few exceptions,
similar to the traditional treatment by activated sludge.
The activated sludge tank generates an effluent favourable for
membrane filtration.
The higher concentration of sludge and the use of membranes
however, introduce significant differences into the sizing.
• n order to obtain interstitial water with good filterability,
i
the size of the reactor must ensure total elimination of
interstitial COD under the most restrictive conditions of load
and temperature. In contrast, barring mandatory standards
in total nitrogen, denitrification is optional, because unlike
the conventional process, there is no risk of sludge backing

4. Degrémont Water Treatment Handbook Factsheets
A few Degrémont references
• Siepam, Val d’Arly (France) = 29 000 EH
• Saint-Barthélemy (France) = 3 500 EH
• Focus on the Cogolin (France) wastewater treatment plant 45,000 PE scheduled for commissioning by mid-2011
Water line
Raw water
Discharge
Fine screening (6 mm)
Parameter Guarantees
Desanding / Degreasing (Daily average)
SS (mg.L-1) 5
Distribution
COD (mg.L ) -1
50
Straining (200 µm) BOD (mg.L-1) 10
NGL (mg.L-1) 10
Biological basins
(Anaerobic, Anoxic, Aerated) Ptot (mg.L )
-1
1
Ultragreen™ membrane bioreactor
=
Toray flatsheet membranes
Vtot = 3,000 m3, Smembrane, tot = 11,200 m2
Treated Water
The solution chosen by the Syndicat Intercommunal d’Assainissement de Gassin will allow the town to discharge quality effluents into
the Giscle sensitive area and to reuse 40% of the treated water for watering parks and gardens.
The possibility of superimposing Toray flatsheet membranes has enhanced the highly compact size of the facility and allowed the town
to design a low-profile plant that blends into the environment.
Degrémont Handbook Factsheets No. 1 - April 2011 – Photo credits: Degrémont
Contact Ultragreen™: innovation.mailin@degremont.com
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