CA2010088A1 - Process and installation for biological treatment, e.g. by nitrification and/or denitrification, of an effluent including nitrated pollution - Google Patents
Process and installation for biological treatment, e.g. by nitrification and/or denitrification, of an effluent including nitrated pollutionInfo
- Publication number
- CA2010088A1 CA2010088A1 CA 2010088 CA2010088A CA2010088A1 CA 2010088 A1 CA2010088 A1 CA 2010088A1 CA 2010088 CA2010088 CA 2010088 CA 2010088 A CA2010088 A CA 2010088A CA 2010088 A1 CA2010088 A1 CA 2010088A1
- Authority
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- Canada
- Prior art keywords
- granular material
- zone
- installation according
- water
- mixing zone
- Prior art date
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- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/08—Aerobic processes using moving contact bodies
- C02F3/085—Fluidized beds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/0039—Settling tanks provided with contact surfaces, e.g. baffles, particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/0039—Settling tanks provided with contact surfaces, e.g. baffles, particles
- B01D21/0045—Plurality of essentially parallel plates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/0039—Settling tanks provided with contact surfaces, e.g. baffles, particles
- B01D21/0057—Settling tanks provided with contact surfaces, e.g. baffles, particles with counter-current flow direction of liquid and solid particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/24—Feed or discharge mechanisms for settling tanks
- B01D21/2488—Feed or discharge mechanisms for settling tanks bringing about a partial recirculation of the liquid, e.g. for introducing chemical aids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/26—Separation of sediment aided by centrifugal force or centripetal force
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/34—Treatment of water, waste water, or sewage with mechanical oscillations
- C02F1/36—Treatment of water, waste water, or sewage with mechanical oscillations ultrasonic vibrations
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
- C02F1/385—Treatment of water, waste water, or sewage by centrifugal separation by centrifuging suspensions
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/10—Packings; Fillings; Grids
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/28—Anaerobic digestion processes
- C02F3/2806—Anaerobic processes using solid supports for microorganisms
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Microbiology (AREA)
- Mechanical Engineering (AREA)
- Biodiversity & Conservation Biology (AREA)
- Analytical Chemistry (AREA)
- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
- Biological Treatment Of Waste Water (AREA)
Abstract
TITLE OF THE INVENTION
Process and installation for a biological treatment, e.g. by nitrification and/or denitrification, of an effluent including nitrated pollution.
ABSTRACT TEXT
A process for the biological treatment of an effluent to be treated, including nitrated pollution includes the following steps :
- an incident flow of this water is brought into a mixing zone with at least one compartment in which, by turbulent mechanical agitation, a little consumed and slightly soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, and is maintained at a more or less constant mass concentration;
- this water and this granular material in suspension are circulated in a separation zone from which is extracted on the one hand clarified water, and on the other hand biomass loaded granular material; and - almost all of the: active biomass fixed on said granular material is brought back by forced recycling to the mixing zone.
Process and installation for a biological treatment, e.g. by nitrification and/or denitrification, of an effluent including nitrated pollution.
ABSTRACT TEXT
A process for the biological treatment of an effluent to be treated, including nitrated pollution includes the following steps :
- an incident flow of this water is brought into a mixing zone with at least one compartment in which, by turbulent mechanical agitation, a little consumed and slightly soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, and is maintained at a more or less constant mass concentration;
- this water and this granular material in suspension are circulated in a separation zone from which is extracted on the one hand clarified water, and on the other hand biomass loaded granular material; and - almost all of the: active biomass fixed on said granular material is brought back by forced recycling to the mixing zone.
Description
2~
The invention relates to the biological treatment of domestic or industrial effluent, and of water to be made drinkable.
As is known, sewage and sometlmes also water to be made drinkable, contain materials in ~uspension, not only mineral but also organie and nitrated. This sewage contains in addition dissolved or colloidal materials (particles of 1QSS than one mieron).
~ iological treatment processes have been developed aecording to which biomass is developed, that is eolonies of bacterla intended to feed on the organie or nitrated materials eontained in the sewage to be treated.
The biologieal treatment proeesses of sewage ean be dlvided into two major eategories.
A first eategory of biologleal treatment proeesses lnvolves aetivated sludges after a pre-treatment. Thus, in a so-ealled "aetivated sludges" tank where the untreated water arrives, sultable aeration eonditions are maint~ined to supply oxygen to the ~iero-organisms and to maintain the expansion of the sludges due to an ; 20 appropriate aeration deviee sueb as, for exa~ple, piereed tubes in the bottom of the tank, or an aeration turbine situated on the suraee.
The ~fluent whieh eomes from this tank passes into a elarifier at the bottom o whieh some of the sludge is drawn o~ in order to recycle it into tne tank and maintain biological life therein , the excess sludge is eliminated. If y designates the content of biomass in the water, this quantity is maintained generally in the aetivated sludges tank at a value normally eomprised between 2 and 6 g/l., for example equal to 5 g/l..
In general, the thiekening of the sludges is e~eeted without intervention of any granular Faterial. In fact, the so-called "activated sludge"process dea~s in principle with free b~cteria or microorganisms Aeeordlng to one Varla~loa, l~ nas, however, already been ~ proposed to add powdered aetivated chareoal as a purification adjuvant. This is ; dPscribed for example in patent CH-545.254 or in the article "PAC Process" of Mr. John A. MEIDL in WATER/ENGIN~ERING AND MANAGEMENT, June 1982, pp 33-36. Charcoal is there used mainly because of its adsorption capacities, allowing it to adsorb non-biodegradable toxics~ Taking into account the high price of activated charcoal, it is important to envisage the most efficient regeneration cycles possible, which in practice are complex and energy~consuming(in ;
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particular it is necessary to take into account heating Lhe charged or loaded activated charcoal to 200C).
According to other variations it was proposed to use calcium carbonate as a sludge adjuvant eVQn flue dust which is expected to be lost ln the excess sludge that is evacuated.
The per~ormances of such a process by activated sludges depends on the ratio of the mass load of incidental pollution (ueasured in kg/l.) expressed as the biological oxygen demand for a given period, to the biomass quantity present in the activated sludges tank (generally one is interested in the parameter B.o.D.5 which corresponds to the biological oxygen demand of a given weight of biomass for 5 days). The ratio, which readjusts the supply of nourishment to the consumption capacity of the biomass, is measured in kg/kg per day or in d . The higher it is the more significant the flo~ of water supply to be treated can be, and the lower the investment needs to be. In practice it varies between 0.1 and 1.
, The processes by activated sludges also aim so~etimes to treat nitrated pollution; the pertinent parameter is then the weight of ~treated nitrogen per kllogram o~ biomass and per day; this parameter -20 is of the same dimension as previously.
The activated sludge techniques are limited by the suitability of the activated sludges, loaded or not, to decantation, which ls usually characterized by the MOHLMANN index which corresponds to the volume occupied by 0~2 gram of sludge: the lower the index, the better tha decantation. In practice the indices recorded vary between a value of 1000 (very bad) and a value of 100 tvery good). It is understood that the treatment process can be maintained with contents ~ of biomass as high as the corresponding MOHLMANN index is low.
In order to increase the performances of an installation, it is sought a priori to keep the biomass content,in a steady state,that is as high as possible, i~ possible reaching or even exceeding 10 g/l., but the known processes hardly allow 5 to 6 g/l. to be exceeded. A
priori, it is also sought to reduce the MOHLMAWN index.
A seco~d category of treatment processes involves fixed bacteria, for example on ~he ~ranular material of a fluidized hed through which the crude effluent is passed from bottom to top. The maintenance of the bed in a fluidizedstate without material outflow requires .. . . . .
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r 2~3~0088 _ 3 very strict constraints with regard to the supply of the effluent, which may turn out to be incompatible with the siæe of fluctuations in volume of water to be treated daily. In addition, these fluidized-bed processes present starting difficulties. Finally, the regeneration of the granular material of the bed requires a partial recycling between two levels of the bed, which is energy-consumin~.. Examples of such process are given by US-3,855,120 or by the article on the OXITRON system ~ublished in CHEM-ING-TECH, vol 51, n 6, June 1979, pp 549-559 Verlag Chemie Gm~h Weinheim - Germany The object of the invention is to overcome the previously-mentioned inconveniences and to improve the performances of the treatment, main~y ln ~é casë o~ ni~rated pallut~on such as ammonium hydroxide, of-..
reducing the spaced required while bringing about a flexibility of use compatible with the fluctuations of the entry flow of the crude effluent, all for investment costs (even running costs) which are lower than in the past for a comparable level of performance.
To this effect, it puts forward a process for the biological treatment of sew~ to be treated~ including at.lea~t a nitrated pollution, accor-ding to which : ~
- an Lncident flow of this water is brought into a mixing zone with at least one compartment in which, by turbulent mechanical agitation, a little consumable and~ soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, ~nd ls maintained at a substantially constant mass concentration ;
- this water and this granular material in suspension are circulated in a separation zone from whlch is extracted on the one hand clarified water, and on the other hand ~iomass loaded granular material; and - al~ost the whole of the active biomass f ixed to the said granular material is brought back by forced recycling to the mixing zone.
It is to be noted that in the mixing zone an integral agitation is produced which is véry different from the linear supply that is observed for the effluent supply in processes employing a fluidized bed. In addition all of the granular material passes, in principle, into the separation zone.
Thus the strict operating constraints connected with fluidized beds are obviated, while obtaining purification yields greatly superior to those which could be found for equivalent mass loads in the absence of granular material(activated sludges),all for a moderate investment :.
and operating cost, and the granular material can be a cheap mineral material, for .
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: - 4 -example sand, which is easy to recover without excessive energy : expenditure.
According to preferred arrangements, possibly combined to each other :
when said nitrated pollution comprises a~monium hydroxide, in addition oxygen iS injected into the mixing zone for example in the form of air in an appropriate supply t~a~ eunances the aeveloplllent of a nitrificating biomass, Cixed on the granular material, - in the case where the nitrated pollution is in the form of nitrates, a source of organic carbon is also injected into this mixing zoaa,which is an anaerobic environment (that is without the injection of free oxygen), - in the case where the nitratea pollution is in an organic form or in the form of am~onium hydroxide, this mixing zone is composed of two zones, one of nitriication taerobic3, then one of denitrification (anaerobicl, or conversely with recycling of the sludges and granular material between these two zones, - the granular material that is put in homogeneous suspension is of mineral :type, preferably fine sand~.
. - the granular material contained in a non-recyc.led residual part of the"sludges"
is recovered through a sep~ration step of.physical.or (bio)chemical type (non ~kermical) ~nd re-injected,togethel with active biomass which sticked thereto into the mixing zone whilst poorly adhering sludge separated from this granular matet~lealcioSceevn~cruaaltleod~ of granular m te i l i th i i maintained approximately at a value between 5 and 100 g/l., or between 5 and 50 g/l. , .25 - if the granular material is fine sand, its concentration is : maintained at a value of between 5 and 50 g/l., for example approximatively 20 g/l., - the turbulent agitation induces an internal recycling between 5 and 100 times the incident supply, preferably between 10 and 50, or between 10 and 30 times the incident supply, - *he gra~ular material carrying the fixed biomass is returned to the mixing zone ~y forced recycling in a supply amounting to between 10 and 500% of the incident water supply, - said almost whole of the biomass loaded granular material in the incident supply is returned upstream of the mixing zone, or directly in the latter, - the homogeneous suspension is left to degas before entering the ~: ,~ : :
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separatioa ~one. ~ 8~
It will be noted that in the case (an important one in practice) of a ~ , ~ater containing a nitrated pollution in the form of ammonium ~yd~oxide?with or without any derivation of a residual part of the sludge~ in excess to beevacuated there is kept the whole (at least approximatively) of the nitrificating bacteria, which develop only slowly but are strongly adherent and which are not separated during the separation step, even in the case of a i-strong one, with hydrocyclones for example.
The invention also puts forward an installation for the biological treatment of pre-treated sewage containing a nitrated pollution com-p sing a mixing zone with at least one compartment into which a pipe opens, for admitting water to be treated, which is fitted with mechanical means for turbulent agitation and which contains a little consuma~le~: and soluble granular material loaded withfixed biomass, forming a homogeneous suspension of given concentration;
- a separatlon zone downstream of the mixing zone, fitted with a drainage channel for the clarified water and a drainage channel ~or loaded granular material ;
- a pipe for biomass loaded granular material recycling fitted with pumping means, star~ing from the sludge drainage ehannel and ending at the mixing zone or upstream of the latter.
According to the pre~erred arrangements:
- the mlxing zone co~prises at least one mixing reactor (or compartment) containing oxygenation means, - the oxygenation means are formed by an oxygenation manifold, - the mixing zone eomprises, in series, an aerobic nitriieation reaetor containing an oxygen supply an~ an ano~ic denitrification ;~ reaetor eontaining an organic carbon supply, .~ ~
- the mixing zone comprises, in series,~-an ~anoxic denitrification -` reaetor, then an aerobie nitrification reactor itted with an oxygen supply, a recyeling pipe being eonneeted between the exit of the ` 25 aerobi~ nitrifieation reaetor and the anoxic denitrifieation reactor, - the mechanieal means for turbulent agitation eomprise an agitator, - this agitator comprises blades offset along a drive shaft and shaped ; in sueh a way that they cause flows in opposite directions along this shat, - this agitator is positioned vertically, ;; - the granular material is of ~ineral type, for example fine sand?
- the granular material has, in the mixing zone, a concentration of between 5 and 100 g/l., or between 5 and 50 g/l., - the granular material has a granulometry o between 20 and 500 ~m, ... .
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- the granular material is sand of granulometry of between 80 and 200 ym, _ the installation co~.prises a line o~ physical (for example of mechanical type) sep~ra~ion star~in~ from th~ loa~ed ~ra~ ar materlal dralna~ge channei in parallel wlth the recycling pipe and ending at a biomass loaded gran~lar n~a~erial reinjection ~iPe ending at the mixing æone or upstream of the latter, - this installation comprises a degassing zone between the mixing zone and the separation zone, - the separation ~one is a decanter, which can contain laminar decantation elements; the separation can also be effected by any other appropriate means such as centrifugation, sieving, or filtration in particular over a membrane.
The characteristics and advantageous subjects of the invention emerge from the description which follows, given as a non-limitative example, with regard to the attached drawings on which:
- figure 1 is a simplified schematic view of a biological treatment installation in accordance with the invention;
- figure 2 is a partial schematic view o~ an embodiment variation of this installation;
- figure 3 is a slmpli~ied schematic view of yet another embodi-ment variatlon of an installation in accordance with the invention, corresponding to a combined nitrification/denitrification treatme~t ;
and - ~igure 4 is an e~bodiment variation of the installation of figure 1, corresponding as in figure 3 to a nitrification/denitrification treatment.
The biological treatment installation represented in figure includes principally a mixing zone A and a separation zone B.
The mixing zone A contains at least one mixing reactor 1 (here one) containing a granular material loaded with biomass and into which opens a supply pipe 2 for water to be treated, and a recycling pipe 3 for almost the whole of biomass loaded granular material, whil,st the separation ~one B comprises a chamber 4 communicatiag with the mixing reactor 1, here by the inter-mediary of a vertical degassing corridor 5; this chamber 4 is fltted with collection ~recovery) means 6 ending at a drainage pipe 7 for : clarified water, as well as means 8 for the extraction o the granular . materlal loaded w;th blomass :,;
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ending at a drainage pipe 9 for loaded granular material. A derivation control avlve is provided on this pipe 9 from where the above mentioned recycLing channel 3 starts. This is in practice fitted with pumping means I1.
In a ~referred case (nitrated pollution i~ the form of am~onium hydroxide or even B0~) aeratlon means are also provlded m the mixing reactor 1, here constituted by an aeration manifold comprising pierced tubes 12 positioned at the bottom of the reactor, which are connected to an air or oxygen supply pipa. As a variation which is not represented, these aeration means are constituted by a surface aeration turbine. The air injection supply is advantageously chosen in such a way as to transfer into the water between 4 and 5 kg of oxygen per kg ~N-NH4), for nitrification, and between 0.5 and 1.5 kg of oxygen per kg ~B.O.D.), for the elimination of B.O.D.~
In a fashion which is also preferred, a pipe 14 for the in~ection of granular material also goes into this reactor, the granular material advantageously obtained by ~recovery of the granular material loaded -wit~ (active) biomass contained ln a possible non-recycled fraction of the loaded material ~ranular ~eaving the separation chamber 4 by the pipe 9. To this effect, the ; said non-recycled fraction circulates via the valve 10 in a20 recovery/separation line here comprising a container C for the reception o~ loaded granular material fitted with an agitator 1~ and a recovery/separation device D.
A pipe 16 comes from the reception container C, and is fitted with pumping means 17, which ends at the device D: this comprises in practice hydrocyclones 18 at the exit of which sludges without granular material are drained off via a pipe 19, and the biomass lo~de~ ~ranular material is drained off via pipe 14, in an appropriate physical state to allow it to be re-injected into the mixing reactor 1~ As a variation which is not represented, ~he re~overy can be brought about, in particular, by sieving, by moderat po~er ultrasound,by centri~uging, by chemical or biological means (for example by leaving loaded g~a~ular material to rest for a certain time without nourishment and/or oxygenation).
In the mixing reactor 1 are provided mechanical means 20 for h turbulent agitation, here constituted by an agitator comprising a ; vertical shaft 21 carrying blades 22 and turned by a motor 23.
In the separation chamber 4 are provided separating means 25, here of static type, for example constituted by laminar decantation ' . , ~ ,~ . . . ..
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blocks 26.
In the example represented in ~igure 1, the supply pipe 2 for water to be treated opens out approximately half-way up in the reactor. However, taking into account the turbulent agitation brought about by the agitator, the position of the water supply can be of any height.
Also it is only as a preferred example that the supply Nhich leaves the reactor goes into the upper part of the degassing corridor whilst this supply then goes into the lower part of the separation chamber; as a variation which is not r~presented the flow into the degassing corridor can be achieved from bottom to top, or horizontally on the side o~ the reactor 1 and the chamber 4. This corridor 5 can even be omitted in certain cases.
The water to be treated biologically, arriving via the pipe 2, has in practice undergone a standard physical pre-treatment in order to eliminate at least the large particles (~, 1 mm) in suspension tin practice of size greater than or equal to that of the granular material). This pr~-treatment comprises a screening, or a sieving, and a de-sanding advantageously completed by a de-oiling, or by a primary decantation. Except in certain cases (in particular dephos-phatation) this pre-treatment does not include complete che~ical treatment before the water enters the reactor; however there may be, if necessary, an injection of additives just before the entrance of this reactor.
In a preferred fashion the granular material contained in the mixing reactor has a granulometry of between 20 and 500 jum. It is preferably find sand, a material which constitutes, or a reasonable -investment cost, a suitable support for the fixation and development of a biomass;
the granulometry of this sand is preferably chosen between 80 and 30 200 ,um.
The concentration of this material in the reactor 1 is maintained in a pre-determined range, for example chosen between 5 and 100 gJl., preferably chosen between 5 and 50 ~/l- (for example about 20 g/l.), in particular in the case of sand.
The turbulent agitation effected by the mechanical agitator 20 aims to maintain this granular material in suspension according to a - :
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more or less homogeneous distribution.
The blades 22 of the agitator are advantageou51y distributed at several levels and are preferably shaped in such a way that they cause vertical flows in opposita directions along the shaft 21.
This turbulent agitation is in practice suitable for bringing about, inside the reactor, an internal re-circulation of about 5 to 100 times the incident supply of water to be treated.
The biomass which develops on the granular material is of a nature which depends on the organic load contained in the water to be treated and on the existence or not in the reactor of an oxygenation source. In the case where there is an oxygenation (see figure 1), the presence of a large organic load (B.O.D.) in the incident water encourages the development of bacteria whlch consume organi~ particles to the detriment of bacteria which are able to consume ammonium hydroxide; if on the other hand the organic load is low,bacteria especially develop (slow to develop but they are stro~gly adherent) which can covert ammonium hydroxide into nitra~es.
Finally, lf the organic load is not zero, but there is no oxygenation, there is a third type o~ bacteria which pr~ferably develop, suitable to convert the nitrates into nitrogen. Taking into account the inconveniances connected with the formation o~ nitrates, it may be advantageous, as will be seen further on, to provide two successive mixing rea~tors to degrade the ammonium hydroxide into nitrogen. In fact, one can select the prepondera~t type of bacteria thanks to an appropriate preliminary seeding;
one can also,in a view for exampleto enhance nitrifi~ation, doping the waterby injection of ammonium hydroxide). It is there to be noted that nitrificating bacteria keepbeing fixed on the granular material oven during recovery/separation~
Taking into account that, after the time spent by the water to be treated in the reactor 1 which is on average more or less constant, 2~ all of this water passes into the separation chamber, there is no significant accumulation of granular material in the reactor; so that the concentration of this granular ~aterial can remain more or less constant in the reactor, with an approximately constant concentration of biomass, almost all of the granular material leaving the separation chamber via the pipe 9 must be re-injected into the reactor 1 via the recycling pipe 3, the pipe 14 only bringing about a booster injection.
In practice, at least three-quarters, if not 90% (or even more), of the granula~
material leaving the chamber 4 via the pipe 9, is re-injected;
taking into account the suitability of this "sludge" to be pumped (fluidity), it appears that it is necessary to re-inject this loaded mate~ial with a supply amounting to batween 10 and 500% of the incident supply : .
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00~38 of water to be treated, this recycling rate being lower the more ~oncentrat~
the granular material suspension is. In practice this rate is defined as a function of the maximum concentration which can be envisaged.
Instead of ending in the reactor, the recycling pipe can, as a variation which is not represented, rejoin the pipe 2 just upstream of the reactor 1.
The use of the degassing corridor 5 is to free the mixture in suspension from air bubbles which could have been trapped during the turbulent agitation and which would tamper with the gravitational separation which is produced in the chamber 8 with loaded granùlar material which isheavier than the water.
Table 1 includes the numerical information corresponding to two systems of nitrification of ammonium hydroxide ~ere after elimination of the B.O.D.) obtained successively in the same pilot installation in accordance with that of figure 1 and such that:
- the mixing reactor is of cylindrical form with a capacity of 30 litres for a height of 1 m;
- the supply of untreated water to this reactor is controlled by a pump with a supply variable between 10 and 30 l./hr, the supply of which varies with time as a function of the volume of water to be treated;
- there is a supply of about 20 to 150 l./hr for the recycling pump 11, that is 100 to 500% of the supply pump flow;
- the decanter 25 is inclined at 60 (simulating a laminar ~5 decantation~, and supplied via the bottom, the water treated being drained off by an overflow.
The incident ~ater is at "E" level, according to the French norms, that is that lt has a maximum content of Matter In Suspension (MIS) of 30 mg/l. for a Chemical Oxygen Demand (C.O.D.) of 90 mg/l., For the tests, the content of ammonium hydroxide of this water was increased by doping with 30 to 90 mg/l. of N-NH4.
The figures of Table 1 correspond to -the established system obtained with an incident load of 0.8 kg of N-NH4 per cubic meter of reactor and per day. Two series of figures are given for each system of use, each series containing, if appropriate, the input and output values respectively.
. .
,, . ~, , ~0~0~8 The two successive systems of use have in common the fact that they brin~ into the reactor a content of granular material in suspension of 40 g/l., a biomass content of 0.7 g/l. - marked VMS
(volatile matter in suspension) -, for a total air supply of 0.5 m /hr which could be reduced, in an installation of true size, to about 0.1.
In the first mode of use the supply of water to be treated is 11 l./hr; this water is highly loaded with ammonium hydroxide (between 83 and 89 mg/l. of nitrogen) for a C~O.D. of 42 to 50 mg/l., less than mg/l. of MIS and an N03 content o 24 to 26 mg/l. expressed in N-10NO30 The system o use is defined by a recycling rate of 400 to 500%, a time o 3 hours spent in the reactor, a speed of 20 m/hr in the decanter and a HAZEN speed (characteristic o the decantation process) of 0.26 m/hr. A reduction rate of 66 to 72% in ammonium hydroxide is observed~
15In the second mode of use, the supply of water to be treated is higher (28 l./hr); the content of ammonium hydroxide is half as much (40 or 56 mg/l. of nitrogen) as in the irst case (no doping), for comparable C.O.D. and MIS contents. The recycling rate is less (200%) as well as the time spent in the reactor (one hour). The rate of reduction of ammonium hydroxide is also better (75 and 85%) than inthe first case.
It can be seen from the results of these two systems that the invention allows very high levels Of nitrated pollution load eliminated per unit of volume o~ the reactor (0.7 to 1 kg (N-NH4)/m ).
As a comparison, an installation based on the principle o~ activated sludges results in values at the most equal to about 0.2 kg (N-NH4)/m ; tremember that the fluidi~ed-bed principle is hardly used taking into account the strict operating constraints which are connected with it).
It is important to note that the invention arrives at these results by departing from the prejudice o the expert who, in order to increase the performances, sought to achieve higher and higher biomass (~) contents: according to the invention, this content is here lower , :
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Furthermore, the MOHL~ANN index here is lower than 50, which corresponds to excellent values.
Figure 2 represents a biological treatment installation constituting an embodiment variation of that of figure 1 (the recovery sequence is not represented here because it is not necessary in case of a pollutio~l of only the nitrated type (N-NH4 in particular) ). This ins~allation is distinguished from that of ~igure by the fact that the mix~ng zone A' communicates directly with the separation zone B', without a degassing corridor; in addition, the recycling is carried out internally.
The mixing æone A' is quite similar to that of figure 1 (with addition of the "primary" index to the reference figures designating the elements similar to those o ~igure 1). The injection of water to be treated is effected in the upper part of the reactor 1' whilst the communication with the separation zone is effected in the lower part, by an underflow. The water-granular material separation is effected here by simple gravity. The ~ottom of the separation chamber 4' is inclined towards the reacto~ and is fitted with raking means 8' which tends to force the loaded gran~lar~material into a recovery chute 9' sit~ated under the communication zone by an underflow between the zones A' and B'. This chute 9' is`fitted with an extraction nozzle 9'A communicating through a valve 9'B ~ith a line 3' for loaded granular material recycling fitted as previously with pumpin~ ~eans 11'. An optional injection 13' of booster granular material is advantageously effected into this recycling nozzle downstream (or upstream) of the previously-mentioned pump which is not represented.
This installation can also be used to degrade simultaneou~ly the organic load of the water to be treated: then abundant sludges are formed which in practice makes it very useful to proceed to a recovery by separation of the granular material and to a draining of of the excess biomass.
The installation o figure 2 has the advantage of being very compact.
It can be noticed that, in this example of figure 2, the recycling nozzle is attached, not to the reactor 1', but to the pipe 2 for admitting water to be treated.
Figure 3 is a variation (schematic), with several reactors in series, of the installation of figures 1 or 2, suitable for a nitrificatiOn --denitrification treatment of the water to be treate~, combined with BOD treatment This installation comprises a first reactor l"A similar to that of figures 1 and 2 and including an oxygenation manifold 12": it establishes an aeroblc system whlch encourages bacterla whlch convert the ammonium hydroxide into nitrates. (they can be enhanced through initial seeding). ~his reactor 1"A ,cjommunicates, here by an over-flow,,With a second mlxing reactor 1 B whlch lS
distinguished from that of flgures 1 and 2 by the absence of any source of oxygenatlon (anaerobic environment). A source of organic carbon (for example ln the form of methanol, molasses, acetic acid ...) is injected into it here at position 30; by this injection of ~ ubstrate the development o~ bacteria is encouraged which convert the nitrates formed in the mixing reactor l"A into gaseous nitrogen~ This second reactor communicates by an underflow with a degassing chimney 5" then enters the separation zone 4". As previously, most of the loaded granular material collected in the decantation zone B" are recycled.
According to an e~bodiment variation ~not represented) solely dedicated to denitrification ~the first reactor l"A is done away with.
Figure 4 is a variation of figure 1 which comprises two mixing reactors l"'A and l"'B which correspond to the reactors l"A and l"B of figure 3, but the liquid to be treated passes through them in a reverse order to that of figure 3: in effect, the liquid to be treated first passes through the reactor 1" ~B which is maintained in an anaerobic condition and then through the reactor l"'A which is maintained in an aerobic condition. A pipe 40 fitted with pumping means which are not represented allows the liquid, loaded with granular material, to be recycled rom the exit o the reactor l"'A
towards the reactor l"'B. Conse~uently, the nitrates for~ed in the reactor l"'A are re-injected into the reactor 1"'B there to be converted into gaseous nitrogen by bacteria feeding on the organic carbon contained in the liquid to be treated. In practice, the supply for recycling between the exit of reactor l"'A and the entrance of reactor 1" 'B is pre~erably chosen between 1 and 6 times (preferably between 2 and 4 ti~es) the incident supply of water to be treated.
As previously, there is recycling of the g~anular material co~ming from the separation zone 4"' towards the mixing zone tpreferably towards ., ~ :. , :
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This installation of figure 4 can sometimes be preferred for the treatment of effluent whilst the installation of figure 3 can some-times be preferred for the preparatioll of drinking water.
It goes without saying that the above description has been put forward only as a non-limitative example and that numerous variations can be put forward by an expert without departing from the scope of the invention.
Thus, for example, the granular material preferably of natural (mineral) type, instead of ine sand, can be chosen from the following materials : clay or clinoptilolite, pumice, kaolinite...
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The invention relates to the biological treatment of domestic or industrial effluent, and of water to be made drinkable.
As is known, sewage and sometlmes also water to be made drinkable, contain materials in ~uspension, not only mineral but also organie and nitrated. This sewage contains in addition dissolved or colloidal materials (particles of 1QSS than one mieron).
~ iological treatment processes have been developed aecording to which biomass is developed, that is eolonies of bacterla intended to feed on the organie or nitrated materials eontained in the sewage to be treated.
The biologieal treatment proeesses of sewage ean be dlvided into two major eategories.
A first eategory of biologleal treatment proeesses lnvolves aetivated sludges after a pre-treatment. Thus, in a so-ealled "aetivated sludges" tank where the untreated water arrives, sultable aeration eonditions are maint~ined to supply oxygen to the ~iero-organisms and to maintain the expansion of the sludges due to an ; 20 appropriate aeration deviee sueb as, for exa~ple, piereed tubes in the bottom of the tank, or an aeration turbine situated on the suraee.
The ~fluent whieh eomes from this tank passes into a elarifier at the bottom o whieh some of the sludge is drawn o~ in order to recycle it into tne tank and maintain biological life therein , the excess sludge is eliminated. If y designates the content of biomass in the water, this quantity is maintained generally in the aetivated sludges tank at a value normally eomprised between 2 and 6 g/l., for example equal to 5 g/l..
In general, the thiekening of the sludges is e~eeted without intervention of any granular Faterial. In fact, the so-called "activated sludge"process dea~s in principle with free b~cteria or microorganisms Aeeordlng to one Varla~loa, l~ nas, however, already been ~ proposed to add powdered aetivated chareoal as a purification adjuvant. This is ; dPscribed for example in patent CH-545.254 or in the article "PAC Process" of Mr. John A. MEIDL in WATER/ENGIN~ERING AND MANAGEMENT, June 1982, pp 33-36. Charcoal is there used mainly because of its adsorption capacities, allowing it to adsorb non-biodegradable toxics~ Taking into account the high price of activated charcoal, it is important to envisage the most efficient regeneration cycles possible, which in practice are complex and energy~consuming(in ;
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particular it is necessary to take into account heating Lhe charged or loaded activated charcoal to 200C).
According to other variations it was proposed to use calcium carbonate as a sludge adjuvant eVQn flue dust which is expected to be lost ln the excess sludge that is evacuated.
The per~ormances of such a process by activated sludges depends on the ratio of the mass load of incidental pollution (ueasured in kg/l.) expressed as the biological oxygen demand for a given period, to the biomass quantity present in the activated sludges tank (generally one is interested in the parameter B.o.D.5 which corresponds to the biological oxygen demand of a given weight of biomass for 5 days). The ratio, which readjusts the supply of nourishment to the consumption capacity of the biomass, is measured in kg/kg per day or in d . The higher it is the more significant the flo~ of water supply to be treated can be, and the lower the investment needs to be. In practice it varies between 0.1 and 1.
, The processes by activated sludges also aim so~etimes to treat nitrated pollution; the pertinent parameter is then the weight of ~treated nitrogen per kllogram o~ biomass and per day; this parameter -20 is of the same dimension as previously.
The activated sludge techniques are limited by the suitability of the activated sludges, loaded or not, to decantation, which ls usually characterized by the MOHLMANN index which corresponds to the volume occupied by 0~2 gram of sludge: the lower the index, the better tha decantation. In practice the indices recorded vary between a value of 1000 (very bad) and a value of 100 tvery good). It is understood that the treatment process can be maintained with contents ~ of biomass as high as the corresponding MOHLMANN index is low.
In order to increase the performances of an installation, it is sought a priori to keep the biomass content,in a steady state,that is as high as possible, i~ possible reaching or even exceeding 10 g/l., but the known processes hardly allow 5 to 6 g/l. to be exceeded. A
priori, it is also sought to reduce the MOHLMAWN index.
A seco~d category of treatment processes involves fixed bacteria, for example on ~he ~ranular material of a fluidized hed through which the crude effluent is passed from bottom to top. The maintenance of the bed in a fluidizedstate without material outflow requires .. . . . .
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r 2~3~0088 _ 3 very strict constraints with regard to the supply of the effluent, which may turn out to be incompatible with the siæe of fluctuations in volume of water to be treated daily. In addition, these fluidized-bed processes present starting difficulties. Finally, the regeneration of the granular material of the bed requires a partial recycling between two levels of the bed, which is energy-consumin~.. Examples of such process are given by US-3,855,120 or by the article on the OXITRON system ~ublished in CHEM-ING-TECH, vol 51, n 6, June 1979, pp 549-559 Verlag Chemie Gm~h Weinheim - Germany The object of the invention is to overcome the previously-mentioned inconveniences and to improve the performances of the treatment, main~y ln ~é casë o~ ni~rated pallut~on such as ammonium hydroxide, of-..
reducing the spaced required while bringing about a flexibility of use compatible with the fluctuations of the entry flow of the crude effluent, all for investment costs (even running costs) which are lower than in the past for a comparable level of performance.
To this effect, it puts forward a process for the biological treatment of sew~ to be treated~ including at.lea~t a nitrated pollution, accor-ding to which : ~
- an Lncident flow of this water is brought into a mixing zone with at least one compartment in which, by turbulent mechanical agitation, a little consumable and~ soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, ~nd ls maintained at a substantially constant mass concentration ;
- this water and this granular material in suspension are circulated in a separation zone from whlch is extracted on the one hand clarified water, and on the other hand ~iomass loaded granular material; and - al~ost the whole of the active biomass f ixed to the said granular material is brought back by forced recycling to the mixing zone.
It is to be noted that in the mixing zone an integral agitation is produced which is véry different from the linear supply that is observed for the effluent supply in processes employing a fluidized bed. In addition all of the granular material passes, in principle, into the separation zone.
Thus the strict operating constraints connected with fluidized beds are obviated, while obtaining purification yields greatly superior to those which could be found for equivalent mass loads in the absence of granular material(activated sludges),all for a moderate investment :.
and operating cost, and the granular material can be a cheap mineral material, for .
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According to preferred arrangements, possibly combined to each other :
when said nitrated pollution comprises a~monium hydroxide, in addition oxygen iS injected into the mixing zone for example in the form of air in an appropriate supply t~a~ eunances the aeveloplllent of a nitrificating biomass, Cixed on the granular material, - in the case where the nitrated pollution is in the form of nitrates, a source of organic carbon is also injected into this mixing zoaa,which is an anaerobic environment (that is without the injection of free oxygen), - in the case where the nitratea pollution is in an organic form or in the form of am~onium hydroxide, this mixing zone is composed of two zones, one of nitriication taerobic3, then one of denitrification (anaerobicl, or conversely with recycling of the sludges and granular material between these two zones, - the granular material that is put in homogeneous suspension is of mineral :type, preferably fine sand~.
. - the granular material contained in a non-recyc.led residual part of the"sludges"
is recovered through a sep~ration step of.physical.or (bio)chemical type (non ~kermical) ~nd re-injected,togethel with active biomass which sticked thereto into the mixing zone whilst poorly adhering sludge separated from this granular matet~lealcioSceevn~cruaaltleod~ of granular m te i l i th i i maintained approximately at a value between 5 and 100 g/l., or between 5 and 50 g/l. , .25 - if the granular material is fine sand, its concentration is : maintained at a value of between 5 and 50 g/l., for example approximatively 20 g/l., - the turbulent agitation induces an internal recycling between 5 and 100 times the incident supply, preferably between 10 and 50, or between 10 and 30 times the incident supply, - *he gra~ular material carrying the fixed biomass is returned to the mixing zone ~y forced recycling in a supply amounting to between 10 and 500% of the incident water supply, - said almost whole of the biomass loaded granular material in the incident supply is returned upstream of the mixing zone, or directly in the latter, - the homogeneous suspension is left to degas before entering the ~: ,~ : :
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It will be noted that in the case (an important one in practice) of a ~ , ~ater containing a nitrated pollution in the form of ammonium ~yd~oxide?with or without any derivation of a residual part of the sludge~ in excess to beevacuated there is kept the whole (at least approximatively) of the nitrificating bacteria, which develop only slowly but are strongly adherent and which are not separated during the separation step, even in the case of a i-strong one, with hydrocyclones for example.
The invention also puts forward an installation for the biological treatment of pre-treated sewage containing a nitrated pollution com-p sing a mixing zone with at least one compartment into which a pipe opens, for admitting water to be treated, which is fitted with mechanical means for turbulent agitation and which contains a little consuma~le~: and soluble granular material loaded withfixed biomass, forming a homogeneous suspension of given concentration;
- a separatlon zone downstream of the mixing zone, fitted with a drainage channel for the clarified water and a drainage channel ~or loaded granular material ;
- a pipe for biomass loaded granular material recycling fitted with pumping means, star~ing from the sludge drainage ehannel and ending at the mixing zone or upstream of the latter.
According to the pre~erred arrangements:
- the mlxing zone co~prises at least one mixing reactor (or compartment) containing oxygenation means, - the oxygenation means are formed by an oxygenation manifold, - the mixing zone eomprises, in series, an aerobic nitriieation reaetor containing an oxygen supply an~ an ano~ic denitrification ;~ reaetor eontaining an organic carbon supply, .~ ~
- the mixing zone comprises, in series,~-an ~anoxic denitrification -` reaetor, then an aerobie nitrification reactor itted with an oxygen supply, a recyeling pipe being eonneeted between the exit of the ` 25 aerobi~ nitrifieation reaetor and the anoxic denitrifieation reactor, - the mechanieal means for turbulent agitation eomprise an agitator, - this agitator comprises blades offset along a drive shaft and shaped ; in sueh a way that they cause flows in opposite directions along this shat, - this agitator is positioned vertically, ;; - the granular material is of ~ineral type, for example fine sand?
- the granular material has, in the mixing zone, a concentration of between 5 and 100 g/l., or between 5 and 50 g/l., - the granular material has a granulometry o between 20 and 500 ~m, ... .
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- the granular material is sand of granulometry of between 80 and 200 ym, _ the installation co~.prises a line o~ physical (for example of mechanical type) sep~ra~ion star~in~ from th~ loa~ed ~ra~ ar materlal dralna~ge channei in parallel wlth the recycling pipe and ending at a biomass loaded gran~lar n~a~erial reinjection ~iPe ending at the mixing æone or upstream of the latter, - this installation comprises a degassing zone between the mixing zone and the separation zone, - the separation ~one is a decanter, which can contain laminar decantation elements; the separation can also be effected by any other appropriate means such as centrifugation, sieving, or filtration in particular over a membrane.
The characteristics and advantageous subjects of the invention emerge from the description which follows, given as a non-limitative example, with regard to the attached drawings on which:
- figure 1 is a simplified schematic view of a biological treatment installation in accordance with the invention;
- figure 2 is a partial schematic view o~ an embodiment variation of this installation;
- figure 3 is a slmpli~ied schematic view of yet another embodi-ment variatlon of an installation in accordance with the invention, corresponding to a combined nitrification/denitrification treatme~t ;
and - ~igure 4 is an e~bodiment variation of the installation of figure 1, corresponding as in figure 3 to a nitrification/denitrification treatment.
The biological treatment installation represented in figure includes principally a mixing zone A and a separation zone B.
The mixing zone A contains at least one mixing reactor 1 (here one) containing a granular material loaded with biomass and into which opens a supply pipe 2 for water to be treated, and a recycling pipe 3 for almost the whole of biomass loaded granular material, whil,st the separation ~one B comprises a chamber 4 communicatiag with the mixing reactor 1, here by the inter-mediary of a vertical degassing corridor 5; this chamber 4 is fltted with collection ~recovery) means 6 ending at a drainage pipe 7 for : clarified water, as well as means 8 for the extraction o the granular . materlal loaded w;th blomass :,;
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ending at a drainage pipe 9 for loaded granular material. A derivation control avlve is provided on this pipe 9 from where the above mentioned recycLing channel 3 starts. This is in practice fitted with pumping means I1.
In a ~referred case (nitrated pollution i~ the form of am~onium hydroxide or even B0~) aeratlon means are also provlded m the mixing reactor 1, here constituted by an aeration manifold comprising pierced tubes 12 positioned at the bottom of the reactor, which are connected to an air or oxygen supply pipa. As a variation which is not represented, these aeration means are constituted by a surface aeration turbine. The air injection supply is advantageously chosen in such a way as to transfer into the water between 4 and 5 kg of oxygen per kg ~N-NH4), for nitrification, and between 0.5 and 1.5 kg of oxygen per kg ~B.O.D.), for the elimination of B.O.D.~
In a fashion which is also preferred, a pipe 14 for the in~ection of granular material also goes into this reactor, the granular material advantageously obtained by ~recovery of the granular material loaded -wit~ (active) biomass contained ln a possible non-recycled fraction of the loaded material ~ranular ~eaving the separation chamber 4 by the pipe 9. To this effect, the ; said non-recycled fraction circulates via the valve 10 in a20 recovery/separation line here comprising a container C for the reception o~ loaded granular material fitted with an agitator 1~ and a recovery/separation device D.
A pipe 16 comes from the reception container C, and is fitted with pumping means 17, which ends at the device D: this comprises in practice hydrocyclones 18 at the exit of which sludges without granular material are drained off via a pipe 19, and the biomass lo~de~ ~ranular material is drained off via pipe 14, in an appropriate physical state to allow it to be re-injected into the mixing reactor 1~ As a variation which is not represented, ~he re~overy can be brought about, in particular, by sieving, by moderat po~er ultrasound,by centri~uging, by chemical or biological means (for example by leaving loaded g~a~ular material to rest for a certain time without nourishment and/or oxygenation).
In the mixing reactor 1 are provided mechanical means 20 for h turbulent agitation, here constituted by an agitator comprising a ; vertical shaft 21 carrying blades 22 and turned by a motor 23.
In the separation chamber 4 are provided separating means 25, here of static type, for example constituted by laminar decantation ' . , ~ ,~ . . . ..
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In the example represented in ~igure 1, the supply pipe 2 for water to be treated opens out approximately half-way up in the reactor. However, taking into account the turbulent agitation brought about by the agitator, the position of the water supply can be of any height.
Also it is only as a preferred example that the supply Nhich leaves the reactor goes into the upper part of the degassing corridor whilst this supply then goes into the lower part of the separation chamber; as a variation which is not r~presented the flow into the degassing corridor can be achieved from bottom to top, or horizontally on the side o~ the reactor 1 and the chamber 4. This corridor 5 can even be omitted in certain cases.
The water to be treated biologically, arriving via the pipe 2, has in practice undergone a standard physical pre-treatment in order to eliminate at least the large particles (~, 1 mm) in suspension tin practice of size greater than or equal to that of the granular material). This pr~-treatment comprises a screening, or a sieving, and a de-sanding advantageously completed by a de-oiling, or by a primary decantation. Except in certain cases (in particular dephos-phatation) this pre-treatment does not include complete che~ical treatment before the water enters the reactor; however there may be, if necessary, an injection of additives just before the entrance of this reactor.
In a preferred fashion the granular material contained in the mixing reactor has a granulometry of between 20 and 500 jum. It is preferably find sand, a material which constitutes, or a reasonable -investment cost, a suitable support for the fixation and development of a biomass;
the granulometry of this sand is preferably chosen between 80 and 30 200 ,um.
The concentration of this material in the reactor 1 is maintained in a pre-determined range, for example chosen between 5 and 100 gJl., preferably chosen between 5 and 50 ~/l- (for example about 20 g/l.), in particular in the case of sand.
The turbulent agitation effected by the mechanical agitator 20 aims to maintain this granular material in suspension according to a - :
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more or less homogeneous distribution.
The blades 22 of the agitator are advantageou51y distributed at several levels and are preferably shaped in such a way that they cause vertical flows in opposita directions along the shaft 21.
This turbulent agitation is in practice suitable for bringing about, inside the reactor, an internal re-circulation of about 5 to 100 times the incident supply of water to be treated.
The biomass which develops on the granular material is of a nature which depends on the organic load contained in the water to be treated and on the existence or not in the reactor of an oxygenation source. In the case where there is an oxygenation (see figure 1), the presence of a large organic load (B.O.D.) in the incident water encourages the development of bacteria whlch consume organi~ particles to the detriment of bacteria which are able to consume ammonium hydroxide; if on the other hand the organic load is low,bacteria especially develop (slow to develop but they are stro~gly adherent) which can covert ammonium hydroxide into nitra~es.
Finally, lf the organic load is not zero, but there is no oxygenation, there is a third type o~ bacteria which pr~ferably develop, suitable to convert the nitrates into nitrogen. Taking into account the inconveniances connected with the formation o~ nitrates, it may be advantageous, as will be seen further on, to provide two successive mixing rea~tors to degrade the ammonium hydroxide into nitrogen. In fact, one can select the prepondera~t type of bacteria thanks to an appropriate preliminary seeding;
one can also,in a view for exampleto enhance nitrifi~ation, doping the waterby injection of ammonium hydroxide). It is there to be noted that nitrificating bacteria keepbeing fixed on the granular material oven during recovery/separation~
Taking into account that, after the time spent by the water to be treated in the reactor 1 which is on average more or less constant, 2~ all of this water passes into the separation chamber, there is no significant accumulation of granular material in the reactor; so that the concentration of this granular ~aterial can remain more or less constant in the reactor, with an approximately constant concentration of biomass, almost all of the granular material leaving the separation chamber via the pipe 9 must be re-injected into the reactor 1 via the recycling pipe 3, the pipe 14 only bringing about a booster injection.
In practice, at least three-quarters, if not 90% (or even more), of the granula~
material leaving the chamber 4 via the pipe 9, is re-injected;
taking into account the suitability of this "sludge" to be pumped (fluidity), it appears that it is necessary to re-inject this loaded mate~ial with a supply amounting to batween 10 and 500% of the incident supply : .
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the granular material suspension is. In practice this rate is defined as a function of the maximum concentration which can be envisaged.
Instead of ending in the reactor, the recycling pipe can, as a variation which is not represented, rejoin the pipe 2 just upstream of the reactor 1.
The use of the degassing corridor 5 is to free the mixture in suspension from air bubbles which could have been trapped during the turbulent agitation and which would tamper with the gravitational separation which is produced in the chamber 8 with loaded granùlar material which isheavier than the water.
Table 1 includes the numerical information corresponding to two systems of nitrification of ammonium hydroxide ~ere after elimination of the B.O.D.) obtained successively in the same pilot installation in accordance with that of figure 1 and such that:
- the mixing reactor is of cylindrical form with a capacity of 30 litres for a height of 1 m;
- the supply of untreated water to this reactor is controlled by a pump with a supply variable between 10 and 30 l./hr, the supply of which varies with time as a function of the volume of water to be treated;
- there is a supply of about 20 to 150 l./hr for the recycling pump 11, that is 100 to 500% of the supply pump flow;
- the decanter 25 is inclined at 60 (simulating a laminar ~5 decantation~, and supplied via the bottom, the water treated being drained off by an overflow.
The incident ~ater is at "E" level, according to the French norms, that is that lt has a maximum content of Matter In Suspension (MIS) of 30 mg/l. for a Chemical Oxygen Demand (C.O.D.) of 90 mg/l., For the tests, the content of ammonium hydroxide of this water was increased by doping with 30 to 90 mg/l. of N-NH4.
The figures of Table 1 correspond to -the established system obtained with an incident load of 0.8 kg of N-NH4 per cubic meter of reactor and per day. Two series of figures are given for each system of use, each series containing, if appropriate, the input and output values respectively.
. .
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(volatile matter in suspension) -, for a total air supply of 0.5 m /hr which could be reduced, in an installation of true size, to about 0.1.
In the first mode of use the supply of water to be treated is 11 l./hr; this water is highly loaded with ammonium hydroxide (between 83 and 89 mg/l. of nitrogen) for a C~O.D. of 42 to 50 mg/l., less than mg/l. of MIS and an N03 content o 24 to 26 mg/l. expressed in N-10NO30 The system o use is defined by a recycling rate of 400 to 500%, a time o 3 hours spent in the reactor, a speed of 20 m/hr in the decanter and a HAZEN speed (characteristic o the decantation process) of 0.26 m/hr. A reduction rate of 66 to 72% in ammonium hydroxide is observed~
15In the second mode of use, the supply of water to be treated is higher (28 l./hr); the content of ammonium hydroxide is half as much (40 or 56 mg/l. of nitrogen) as in the irst case (no doping), for comparable C.O.D. and MIS contents. The recycling rate is less (200%) as well as the time spent in the reactor (one hour). The rate of reduction of ammonium hydroxide is also better (75 and 85%) than inthe first case.
It can be seen from the results of these two systems that the invention allows very high levels Of nitrated pollution load eliminated per unit of volume o~ the reactor (0.7 to 1 kg (N-NH4)/m ).
As a comparison, an installation based on the principle o~ activated sludges results in values at the most equal to about 0.2 kg (N-NH4)/m ; tremember that the fluidi~ed-bed principle is hardly used taking into account the strict operating constraints which are connected with it).
It is important to note that the invention arrives at these results by departing from the prejudice o the expert who, in order to increase the performances, sought to achieve higher and higher biomass (~) contents: according to the invention, this content is here lower , :
..
:' , 2C~ 3088 than 1 g/l., that is lower than in the known processes.
Furthermore, the MOHL~ANN index here is lower than 50, which corresponds to excellent values.
Figure 2 represents a biological treatment installation constituting an embodiment variation of that of figure 1 (the recovery sequence is not represented here because it is not necessary in case of a pollutio~l of only the nitrated type (N-NH4 in particular) ). This ins~allation is distinguished from that of ~igure by the fact that the mix~ng zone A' communicates directly with the separation zone B', without a degassing corridor; in addition, the recycling is carried out internally.
The mixing æone A' is quite similar to that of figure 1 (with addition of the "primary" index to the reference figures designating the elements similar to those o ~igure 1). The injection of water to be treated is effected in the upper part of the reactor 1' whilst the communication with the separation zone is effected in the lower part, by an underflow. The water-granular material separation is effected here by simple gravity. The ~ottom of the separation chamber 4' is inclined towards the reacto~ and is fitted with raking means 8' which tends to force the loaded gran~lar~material into a recovery chute 9' sit~ated under the communication zone by an underflow between the zones A' and B'. This chute 9' is`fitted with an extraction nozzle 9'A communicating through a valve 9'B ~ith a line 3' for loaded granular material recycling fitted as previously with pumpin~ ~eans 11'. An optional injection 13' of booster granular material is advantageously effected into this recycling nozzle downstream (or upstream) of the previously-mentioned pump which is not represented.
This installation can also be used to degrade simultaneou~ly the organic load of the water to be treated: then abundant sludges are formed which in practice makes it very useful to proceed to a recovery by separation of the granular material and to a draining of of the excess biomass.
The installation o figure 2 has the advantage of being very compact.
It can be noticed that, in this example of figure 2, the recycling nozzle is attached, not to the reactor 1', but to the pipe 2 for admitting water to be treated.
Figure 3 is a variation (schematic), with several reactors in series, of the installation of figures 1 or 2, suitable for a nitrificatiOn --denitrification treatment of the water to be treate~, combined with BOD treatment This installation comprises a first reactor l"A similar to that of figures 1 and 2 and including an oxygenation manifold 12": it establishes an aeroblc system whlch encourages bacterla whlch convert the ammonium hydroxide into nitrates. (they can be enhanced through initial seeding). ~his reactor 1"A ,cjommunicates, here by an over-flow,,With a second mlxing reactor 1 B whlch lS
distinguished from that of flgures 1 and 2 by the absence of any source of oxygenatlon (anaerobic environment). A source of organic carbon (for example ln the form of methanol, molasses, acetic acid ...) is injected into it here at position 30; by this injection of ~ ubstrate the development o~ bacteria is encouraged which convert the nitrates formed in the mixing reactor l"A into gaseous nitrogen~ This second reactor communicates by an underflow with a degassing chimney 5" then enters the separation zone 4". As previously, most of the loaded granular material collected in the decantation zone B" are recycled.
According to an e~bodiment variation ~not represented) solely dedicated to denitrification ~the first reactor l"A is done away with.
Figure 4 is a variation of figure 1 which comprises two mixing reactors l"'A and l"'B which correspond to the reactors l"A and l"B of figure 3, but the liquid to be treated passes through them in a reverse order to that of figure 3: in effect, the liquid to be treated first passes through the reactor 1" ~B which is maintained in an anaerobic condition and then through the reactor l"'A which is maintained in an aerobic condition. A pipe 40 fitted with pumping means which are not represented allows the liquid, loaded with granular material, to be recycled rom the exit o the reactor l"'A
towards the reactor l"'B. Conse~uently, the nitrates for~ed in the reactor l"'A are re-injected into the reactor 1"'B there to be converted into gaseous nitrogen by bacteria feeding on the organic carbon contained in the liquid to be treated. In practice, the supply for recycling between the exit of reactor l"'A and the entrance of reactor 1" 'B is pre~erably chosen between 1 and 6 times (preferably between 2 and 4 ti~es) the incident supply of water to be treated.
As previously, there is recycling of the g~anular material co~ming from the separation zone 4"' towards the mixing zone tpreferably towards ., ~ :. , :
.
~` ` .
~ - ~ ~
;~0~ 38 reactor l"'B, or if not towards reactor l"'A) through a line 3"'.
This installation of figure 4 can sometimes be preferred for the treatment of effluent whilst the installation of figure 3 can some-times be preferred for the preparatioll of drinking water.
It goes without saying that the above description has been put forward only as a non-limitative example and that numerous variations can be put forward by an expert without departing from the scope of the invention.
Thus, for example, the granular material preferably of natural (mineral) type, instead of ine sand, can be chosen from the following materials : clay or clinoptilolite, pumice, kaolinite...
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`
Claims (39)
1) Process for biological treatment of an effluent to be treated containing a nitrated pollution, according to which :
- an incident flow of this water is brought into a mixing zone with at least one compartment (A, A', A") in which, by turbulent mechanical agitation, a little consumed and slightly soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, and is maintained at a more or less constant mass concentration;
- this water and this granular material in suspension are circulated in a separation zone (B, B', B") from which is extracted on the one hand clarified water, and on the other hand the granular material loadedwith active biomass; and - almost all of the active biomass-fixed to said granular material is brought back by forced recycling to the mixing zone (A, A', A").
- an incident flow of this water is brought into a mixing zone with at least one compartment (A, A', A") in which, by turbulent mechanical agitation, a little consumed and slightly soluble granular material, loaded with biomass, is put in homogeneous suspension in this water, and is maintained at a more or less constant mass concentration;
- this water and this granular material in suspension are circulated in a separation zone (B, B', B") from which is extracted on the one hand clarified water, and on the other hand the granular material loadedwith active biomass; and - almost all of the active biomass-fixed to said granular material is brought back by forced recycling to the mixing zone (A, A', A").
2) Process according to claim 1, characterized in that, the nitrated pollution being in form of ammonium hydroxide, oxygen is further injected into the miwing zone (A, A', A") in a supply likely to encourage the development of a biomass which consumes the pollution contained in the water to be treated.
3) Process according to claim 2, characterized in that this oxygen is injected in the form of air.
4) Process according to claim 1, characterized in that, in the case where the nitrated pollution being in the form of nitrate, a source of organic carbon is also injected into this mixing zone which is an anaerobic environment.
5) Process according to claim 1, characterized in that, in the case where the water to be treated contains a nitrated pollution in organic form or in the form of ammonium hydroxide, the mixing zone comprises in series an aerobic nitrification zone (1"A) into which oxygen is injected, then an anaerobic denitrification zone (1"B) into which a source of organic carbon is injected.
6) Process according to claim 1, characterized in that, in the case where the water to be treated contains a nitrated pollution in organic form or in the form of ammonium hydroxide, the mixing zone comprises in series an anaerobic denitrification zone (1"'B) then an aerobic nitrification zone (1"'A) into which the following are injected: oxygen and the liquid loaded with granular material leaving the aerobic nitrification zone that is being recycled towards the anaerobic denitrification zone with a supply at least equal to the incident supply of water to be treated.
7) Process according to any one of claims 1 to 6, characterized in that the granular material that is put in a homogeneous suspension is fine sand.
8) Process according to any one of claims 1 to 7, characterized in that the granular material contained in a non-recycled residual part of the sludges is recovered by separation and reinfected together with fixed biomass as into the mixing zone, whilst sludges separated from this granular material are drained off.
9) Process according to any one of claims 1 to 8, characterized in that the concentration of granular material in the mixing zone is maintained approximately at a value of between 5 and 100 g/l..
10) Process according to claim 9, characterized in that the concentration of granular material when it is fine sand is maintained at a value of between 5 and 50 g/l..
11) Process according to any one of claims 1 to 10, character-ized in that the turbulent agitation causes an internal recycling of between 5 and 100 times the incident supply.
12) Process according to any one of claims 1 to 11, character-ized in that the suspension is returned to the mixing zone by forced recycling in a supply amounting to between 10 and 500% of the incident supply of water.
13) Process according to any one of claims 1 to 12, character-ized in that almost all of the loaded granular material in the incident water supply is returned upstream of the mixing zone.
14) Process according to any one of claims 1 to 13, character-ized in that the homogeneous suspension is left to degas (5, 5") before being passed into the separation zone.
15) Installation for biological treatment of a pre-treated effluent containing a nitrated pollution comprising :
- a mixing zone (A, A', A", A"') with at least one compartment into which a pipe (2, 2', 2") for admitting water to be treated opens, which is fitted with mechanical means (20) for turbulent agitation and which contains a little consumed and slightly soluble granular material loaded with fixed biomass forming a homogeneous suspension of a given concentration;
- a separation zone (B, B', B") downstream of the mixing zone fitted with a channel (7, 7', 7") for draining off the clarified water and a channel (9; 9'A, 9'B; 9") for draining off the loaded-granular material ;
- a recycling pipe (3, 3', 3"A) fitted with pumping means (11), starting from the sludge and biomass loaded granular material drainage channel and emptying into the mixing zone upstream of the latter.
- a mixing zone (A, A', A", A"') with at least one compartment into which a pipe (2, 2', 2") for admitting water to be treated opens, which is fitted with mechanical means (20) for turbulent agitation and which contains a little consumed and slightly soluble granular material loaded with fixed biomass forming a homogeneous suspension of a given concentration;
- a separation zone (B, B', B") downstream of the mixing zone fitted with a channel (7, 7', 7") for draining off the clarified water and a channel (9; 9'A, 9'B; 9") for draining off the loaded-granular material ;
- a recycling pipe (3, 3', 3"A) fitted with pumping means (11), starting from the sludge and biomass loaded granular material drainage channel and emptying into the mixing zone upstream of the latter.
16) Installation according to claim 15, characterized in that the mixing zone (A, A', A") includes a mixing reactor (1, 1', 1") containing oxygenation means (12).
17) Installation according to claim 16, characterized in that the oxygenation means are formed by an oxygenation manifold.
18) Installation according to claim 15, characterized in that the mixing zone comprises in series an aerobic nitrification reactor (1"A) including an oxygen input (12") and an anaerobic denitrification reactor (1"B) including an organic carbon input (30).
19) Installation according to claim 15, characterized in that the mixing zone comprises in series an anaerobic denitrification reactor (1"'B), then an aerobic nitrification reactor (1"'A) fitted with an oxygen input, a recycling pipe (40) being connected between the exit of the aerobic nitrification reactor (1"'A) and the anaerobic denitrification reactor (1"'B).
20) Installation according to any one of claims 15 to 19, characterized in that the mechanical means (20) for turbulent agitation comprise an agitator.
21) Installation according to claim 20, characterized in that this agitator comprises blades (22) offset along a drive shaft (21) and shaped in such a way as to cause flows in opposite directions along this shaft.
22) Installation according to claim 20 or claim 21, character-ized in that this agitator is positioned vertically.
23) Installation according to any one of claims 15 to 22, characterized in that the granular material is fine sand.
24) Installation according to any one of claims 15 to 23, characterized in that the granular material in the mixing zone has a concentration of between S and 100 g/1..
25) Installation according to claim 24, characterized in that this concentration is between 5 and 50 g/l..
26) Installation according to any one of claims 15 to 25, characterized in that the granular material has a granulometry of between 20 and 500 µm.
27) Installation according to claim 26, characterized in that the granular material is sand of a granulometry of between 80 and 200 µm.
28) Installation according to any one of claims 15 to 27, characterized in that it includes a recovery/separation sequence (C, D)startir from the loaded granular material drainage channel downstream of the recycling pipe and finishing at a biomass loaded granular material reinjection pipe emptying into the mixing zone or upstream of the latter.
29) Installation according to claim 28, characterized in that the recovery line includes at least one hydrocyclone (D).
30) Installation according to claim 28, characterized in that the recovery line includes a means of separation by ultra-sound at a moderate power level.
31) Installation according to claim 28, characterized in that the recovery line includes a means of separation by sieving.
32) Installation according to claim 28, characterized in that the recovery line includes a means of separation by centrifug-ation.
33) Installation according to claim 28, characterized in that the includes a means of separation by chemical or biological means.
34) Installation according to any one of claims 15 to 33, characterized in that includes a degassing zone between the mixing zone and the separation zone.
35) Installation according to any one of claims 15 to 34, characterized in that the separation zone includes decantation means.
36) Installation according to claim 35, characterized in that the separation zone includes laminar decantation elements (26).
37) Installation according to any one of claims 15 to 34, characterized in that the separation zone includes centrifugation means.
38) Installation according to any one of claims 15 to 34, characterized in that the separation zone includes sieving means.
39) Installation according to any one of claims 15 to 34, characterized in that the separation zone includes means of filtration over a membrane.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8901886A FR2643065B1 (en) | 1989-02-14 | 1989-02-14 | METHOD AND INSTALLATION FOR BIOLOGICAL TREATMENT, INCLUDING NITRIFICATION AND DENITRATION, OF WASTE WATER TO BE TREATED |
| FR8901886 | 1989-02-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2010088A1 true CA2010088A1 (en) | 1990-08-14 |
Family
ID=9378758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2010088 Abandoned CA2010088A1 (en) | 1989-02-14 | 1990-02-14 | Process and installation for biological treatment, e.g. by nitrification and/or denitrification, of an effluent including nitrated pollution |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0383674B1 (en) |
| CA (1) | CA2010088A1 (en) |
| DE (1) | DE69000620T2 (en) |
| DK (1) | DK0383674T3 (en) |
| ES (1) | ES2036889T3 (en) |
| FR (1) | FR2643065B1 (en) |
| NO (1) | NO300838B1 (en) |
| TR (1) | TR24711A (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DK136092D0 (en) * | 1992-11-09 | 1992-11-09 | Cowiconsult A S | WASTE CLEANING PLANT AND PARAMETER |
| FR2706883B1 (en) | 1993-06-23 | 1995-10-20 | Degremont | |
| FR2719235B1 (en) * | 1994-05-02 | 1996-07-19 | Omnium Traitement Valorisa | Process and installation for clarifying biological sludge by decantation. |
| FR2720736B1 (en) * | 1994-06-02 | 1998-05-07 | Degremont | Process for the treatment of liquid effluents by activated sludge. |
| SI9400402A (en) | 1994-11-07 | 1996-02-29 | Megusar France Prof Dr | Method of waste water treatment in order to reduce nitrogen contents. |
| FR2751320B1 (en) * | 1996-07-18 | 1998-09-18 | Omnium Traitement Valorisa | FLUIDIZED BED WATER TREATMENT PLANT AND PHYSICO-CHEMICAL DECANTATION AND METHODS FOR IMPLEMENTING SUCH A PLANT |
| GB2312893B (en) * | 1996-10-21 | 2001-01-24 | Holding Company Belgie Nv | Zeolite composition |
| DE19644334A1 (en) * | 1996-10-25 | 1998-04-30 | Bernd Dr Ing Diering | Process for the biological and biological-chemical treatment of wastewater and plant for carrying out this process |
| EP0890553A3 (en) * | 1997-07-11 | 2000-09-27 | SHW Hölter Wassertechnik GmbH | Process for biological water purification and installation for carrying out the process |
| DE19828175A1 (en) * | 1997-10-30 | 1999-12-30 | Sued Chemie Ag | Process for the treatment of process wastewater highly contaminated with ammonium in the wastewater area |
| US6881339B1 (en) | 1997-10-30 | 2005-04-19 | Sud-Chemie Ag | Process for treating industrial and municipal waste water highly loaded with ammonium |
| ES2142738B1 (en) * | 1997-12-05 | 2000-12-01 | Depuracion Biolog Y Bacteriolo | INSTALLATION FOR THE PURIFICATION DEPURATION. |
| WO2008086010A1 (en) * | 2007-01-09 | 2008-07-17 | Cambridge Water Technology, Inc. | System and method for enhancing an activated sludge process |
| DE102007032125B4 (en) * | 2007-07-03 | 2016-05-25 | Stadt Bad Sachsa Bauamt Liegenschaften | Process for wastewater treatment with a wastewater treatment plant |
| PL2163524T5 (en) * | 2008-09-12 | 2018-12-31 | Demon Gmbh | Method for treating wastewater containing ammonium |
| IT201800002446A1 (en) * | 2018-02-06 | 2019-08-06 | Paolo Massimino | "PLANT FOR THE PURIFICATION OF CIVIL, DOMESTIC AND URBAN WASTE, ADAPTABLE TO VARIABLE LOAD FLOWS" |
| FR3132519A1 (en) * | 2022-02-09 | 2023-08-11 | Vinci Construction Grands Projets | Wastewater treatment process |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3855120A (en) * | 1971-07-09 | 1974-12-17 | P Garbo | Oxygenation of waste water |
| CH545254A (en) * | 1972-09-27 | 1973-12-15 | Ciba Geigy Ag | Process for purifying waste water |
| US4200524A (en) * | 1978-10-25 | 1980-04-29 | Biospherics Incorporated | Bio-surface separation process |
| DE3106465A1 (en) * | 1981-02-21 | 1982-09-09 | Menzel Gmbh & Co, 7000 Stuttgart | METHOD, DEVICE AND MEANS FOR WASTE WATER TREATMENT |
| US4693827A (en) * | 1986-03-20 | 1987-09-15 | Zimpro Inc. | Process for protection of biological nitrification systems |
| FR2604990B1 (en) * | 1986-10-01 | 1991-04-05 | Omnium Traitement Valorisa | PROCESS FOR THE PURIFICATION, BY A BIOLOGICAL WAY, OF WASTEWATER ON A BED OF GRANULAR MATERIAL |
| FR2627704B1 (en) * | 1988-02-25 | 1991-12-13 | Ile France Syndicat Eaux | METHOD AND PLANT FOR TREATMENT OF WATER BY DECANTATION USING FINE SAND |
-
1989
- 1989-02-14 FR FR8901886A patent/FR2643065B1/en not_active Expired - Lifetime
-
1990
- 1990-02-13 DK DK90400389T patent/DK0383674T3/en active
- 1990-02-13 EP EP19900400389 patent/EP0383674B1/en not_active Expired - Lifetime
- 1990-02-13 ES ES90400389T patent/ES2036889T3/en not_active Expired - Lifetime
- 1990-02-13 NO NO900696A patent/NO300838B1/en unknown
- 1990-02-13 DE DE1990600620 patent/DE69000620T2/en not_active Expired - Fee Related
- 1990-02-14 CA CA 2010088 patent/CA2010088A1/en not_active Abandoned
- 1990-03-12 TR TR16890A patent/TR24711A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO300838B1 (en) | 1997-08-04 |
| EP0383674B1 (en) | 1992-12-23 |
| NO900696D0 (en) | 1990-02-13 |
| DE69000620D1 (en) | 1993-02-04 |
| EP0383674A1 (en) | 1990-08-22 |
| FR2643065A1 (en) | 1990-08-17 |
| TR24711A (en) | 1992-03-01 |
| NO900696L (en) | 1990-08-15 |
| FR2643065B1 (en) | 1991-06-14 |
| DK0383674T3 (en) | 1993-02-01 |
| ES2036889T3 (en) | 1993-06-01 |
| DE69000620T2 (en) | 1993-07-29 |
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