Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
  • B01D61/04—Feed pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
  • B01D61/025—Reverse osmosis; Hyperfiltration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
  • B01D61/027—Nanofiltration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/145—Ultrafiltration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/147—Microfiltration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/16—Feed pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/08—Prevention of membrane fouling or of concentration polarisation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2311/00—Details relating to membrane separation process operations and control
  • B01D2311/04—Specific process operations in the feed stream; Feed pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
  • B01D2321/30—Mechanical cleaning, e.g. with brushes or scrapers
• • 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
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
  • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
• • 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
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
  • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
• • 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
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination
  • Y02A20/131—Reverse-osmosis

Definitions

• the invention relates to a method for reducing biofouling
• Membranes in the purification of aqueous medium by means of pressure-driven membrane separation process and an apparatus for performing the method.
• the permeability of the system of lining and membrane can reduce so much that in order to maintain a desired performance, that is, a certain volume flow rate per unit time, increasing operating pressures on the side of the water supply are necessary or desired volume flow rate of the membrane separation system can not be achieved at all. Such a loss of performance is called fouling.
• biofouling that is, associated with the formation of a deposit by attachment and growth of microorganisms such as microalgae, fungi, protozoa or bacteria
• Such a coating is called biofilm.
• the accumulated microorganisms can also be attached organic matter or in the partly use and metabolize entrained organic substances as nutrients in aqueous media.
• the metabolic products thereby formed have a very low permeability and strongly adhere to the membrane and are often difficult or impossible to remove from the membrane surface even by dry cleaning.
• Such irreversible deposit formation leads to a constantly decreasing permeability of the membranes, which ultimately requires an exchange of the membranes.
• biofouling is added to the water to be treated with biocides or biostats that are said to kill or inhibit growth of microorganisms.
• biocides or biostats that are said to kill or inhibit growth of microorganisms.
• biocidal chemicals such as in the chlorination of water, organic ingredients of aqueous media are oxidized, whereby their bioavailability as a nutrient for biofilms usually increases and that it is where the biocide is used up , even more biofouling comes.
• Another measure to avoid biofouling is the pretreatment of the water to be purified for the removal of biofilms as nutrient-serving organic substances and / or biofilms-building microorganisms.
• processes such as filtration with and without prior flocculation and sedimentation are used in the water treatment, or it is worked with sorptive process or with biologically active prefilters.
• This object is achieved by a method for reducing biofouling on membranes in the purification of aqueous medium by means of pressure-driven membrane separation processes.
• This process is characterized in that, in a first step, the ingredients causing the biofouling contained in the aqueous medium are at least partially removed from the aqueous medium, wherein the removal takes place by adding these ingredients to the filter material as it flows through one or more sacrificial filters, whereupon the first filtrate obtained by means of pressure-driven membrane separation process is further purified.
• the aqueous medium to be purified may be, for example, surface water such as sea or brackish water, dam or river water, but also municipal or industrial wastewater, process and process water such as boiler feed water, cooling water or emulsions. It can also be solvent or fruit juice.
• the pressure-driven membrane separation processes may be, for example, reverse osmosis (UO), nanofiltration (NF), ultrafiltration (UF) or microfiltration (MF).
• UO reverse osmosis
• NF nanofiltration
• UF ultrafiltration
• MF microfiltration
• the biofouling ingredients of aqueous media are removed in the first step by deposition in the sacrificial filters from the aqueous medium. Only then does the filtrate of the first step be purified in a pressure-driven membrane separation process. Due to the fact that the filtrate obtained in the first step contains less or no biofouling-causing ingredients, further purification by membrane separation processes is less or no longer hampered by biofouling. As a result, the diaphragms of the pressure-driven membrane separation process have a significantly longer service life and the performance of the system for performing the pressure-driven
• Membrane separation process can be obtained with less effort.
• biofouling-causing ingredients of aqueous media are to be understood microorganisms that can lead to the formation of a biofilm, their metabolites and of such microorganisms as nutrient-usable organic matter such as carbohydrates, polysaccharides, proteins or low molecular humic substances.
• sacrificial filters prevail at least equally good conditions for their attachment to the contained in the aqueous medium biofouling ingredients as on the membranes of the subsequent pressure-driven membrane separation process.
• the determining factors in the attachment of aqueous media ingredients to a surface are the likelihood of transporting the ingredients to the surface, as well as the likelihood that the surface-derived ingredients will adhere to the surface.
• the transport probability depends primarily on the flow conditions.
• the adhesion probability is primarily dependent on the surface properties of the ingredients and the surface area and the flow conditions that determine the release probability.
• the probability of detachment is the probability that a particle attached to a surface will be detached from the surface by a flow.
• An attachment to the sacrificial filter is usually due to mechanical and / or specific adhesion. Particularly in the specific adhesion, the electrostatic and van der Waals interactions between the aqueous medium ingredient and the filter material play an important role. The formation of hydrogen bonds leads to deposits.
• These mechanisms are determined by the surface properties of the aqueous media ingredients and the surface properties of the sacrificial filter material.
• a comparison of the affinity of the biofouling-causing ingredients of the aqueous medium to the sacrificial filter and to the membrane of the pressure-driven membrane separation process can be made, for example, by means of the following adhesion properties influencing the surface properties of the sacrificial filter and the membrane:
• affinity is to be understood as meaning the tendency of biofouling substances to adhere to a surface.
• the values of these surface properties for the sacrificial filter should not deviate more than 40% from the corresponding value of the membrane, preferably not more than 30%, more preferably not more than 20%, and most preferably not more than 10%. Even more preferred is that the values of these surface properties for the sacrificial filter be exactly the same as the corresponding properties of the membrane of the pressure-driven membrane separation process.
• the affinity of the biofouling ingredients of aqueous media to the sacrificial filter should correspond to the affinity to the membrane.
• a higher affinity of the biofouling causing ingredients to the sacrificial filter than to the membrane is preferable.
• the biofouling ingredients of aqueous media Flow conditions prevail that the biofouling ingredients of aqueous media, the probability of transport to the surface is at least as high and the separation probability is at least as low as at the membrane of the pressure-driven membrane separation process. If the biofouling constituents of aqueous media have an affinity to the sacrificial filter that corresponds or exceeds their affinity for the membrane, and flow conditions prevail at the sacrificial filter for addition than at the membrane of the membrane separation process, the contents are preferably deposited on the
• Victim filter on The greater the surface area of the sacrificial filters available for attachment, the more completely the biofouling-causing constituents are removed from the aqueous medium to be purified. Flow conditions are more favorable for an attachment, the slower the flow flows and narrower the space flowed through.
• the organic nutrients needed to build up a biofilm such as carbohydrates or polysaccharides, for example alginates, are removed from the sacrificial filter in the aqueous medium before they reach the membrane and become attached to it.
• the sacrificial filter in the aqueous medium As a result, due to lack of nutrients, no biofilm can build up on the membrane or develop a biofilm only very slowly due to a greatly reduced supply of nutrients.
• Filter material in the form of permeable synthetic collectors is used for the sacrificial filters.
• the permeable synthetic collectors consist of a porous polymer foam with a very high number of internal webs and thus a large inner surface. They can be made of different materials and in different shapes, such as polyurethane or polyamide. Usually, a single PSK particle is cylindrically shaped with a size of, for example, 2 ⁇ 5 mm. PSK are described in the literature, for example in "Lehr- und Handbuch
• a filter bed of a plurality of individual PSK particles they are not only flowed around but also flowed through, so that ingredients of the aqueous medium to be cleaned are deposited both on the outer surface and on the inner surface. Since the space between the individual PSK particles acts as a bypass to the pore space of the individual PSK in a filter bed of PSK, only a slight pressure loss occurs when flowing through the filter bed. As a result of the bypass guide, the flow velocity within the pores of the PSK is considerably lower than in the gap between the individual PSKs, whereby ideal conditions for the attachment of biofouling-causing constituents are present within the pores of the PSK.
• the sacrificial filter itself it comes to the formation of biofouling due to the attachment of the biofouling causing ingredients of aqueous media to form.
• the ingredients of aqueous media suitable as nutrients for the biofilm can also be adsorbed and metabolized directly from the aqueous medium on or in the biofilm.
• the sacrificial filter Due to the growth of biofilms and the filtration and accumulation of particles and dissolved constituents present in the aqueous medium, the sacrificial filter with increasing operating time leads to an increase in the operating pressure necessary for a certain power and to a reduction in the flow quality of the filtrate of the sacrificial filter.
• the effluent quality of the filtrate obtained in the first step of the process according to the invention shows the efficiency of the removal of the biofouling-causing constituents from the aqueous medium in the first step.
• Process quality can be measured in various ways, for example as turbidity according to ISO 7027, as dissolved organic ingredients of aqueous media (DOC) according to DIN EN 1484, as a specific absorption coefficient at 254 nanometers (SAK254) according to DIN 38404-3 or as SiIt Density Index (SDI) according to ASTM D-4189.
• SAK254 and the turbidity is preferably carried out online.
• the effluent quality of the filtrate of the first step of the method according to the invention no longer fulfills the desired minimum requirements, an exchange of individual or all sacrificial filters takes place against fresh sacrificial filters.
• the minimum requirements include, for example, the reduction of the initial removal performance and the haze.
• a 40% reduction of the initial removal performance preferably a 30% reduction, more preferably a 20% reduction, and most preferably a 10% reduction is used.
• the reduction in initial removal efficiency is measured as a corresponding reduction in effluent quality.
• a 10% reduction in the value of DOC or SAK 254 corresponds to a 10% reduction in removal performance.
• the turbidity should be kept below a limit, since the sacrificial filter in addition to the biofouling causing ingredients of aqueous media also retained in the aqueous media entrained particulate substances.
• the threshold for haze 1 is FNU (Formazine Nephelometry Unit), preferably 0.5 FNU and more preferably 0.1 FNU. If the turbidity of the filtrate is above the limit, replacement of the sacrificial filters is initiated.
• a monitoring of the effluent quality such as the turbidity and the reduction of the removal performance of the filtrate of each sacrificial filter takes place.
• the effluent quality of the filtrate of the first step of the method according to the invention does not meet the minimum requirements, all sacrificial filters can be exchanged, or there is only an exchange of individual sacrificial filters. If only a single sacrificial filter is used in the process, the effluent quality of its filtrate must meet the minimum effluent quality requirements for the first step of the process of the invention. When multiple sacrificial filters are used, it is acceptable that the filtrate of upstream sacrificial filters have a drain quality that is worse than the minimum first stage effluent requirement, as the following downstream sacrificial filters also meet the minimum effluent quality requirements for the first Step forward.
• the minimum requirements for the effluent quality of their filtrate can be set to different levels, but preferably they correspond to the minimum requirements for the first step of the method according to the invention. In any case, the filtrate of the downstream last victim filter must always meet the minimum requirements for the first step.
• the pressure loss on a sacrificial filter should be less than 1 bar, more preferably less than 500 mbar.
• Another object of the present invention is a device for carrying out the method according to the invention, comprising a feed line for aqueous medium to be purified, which leads to a pressure-driven membrane separation unit, characterized in that in the feed line at least one of the filtered by the aqueous medium to be filtered victim filter is arranged , and each sacrificial filter can be removed from the supply line, and in the supply line at least two devices for arranging a sacrificial filter in the supply line are present, wherein a sacrificial filter comprises a filled with permeable synthetic collector particles filter housing, wherein the affinity of biofouling causing ingredients of the aqueous medium to the permeable synthetic collectors at least exactly great is their affinity to the membrane of the pressure-driven membrane separation plant.
• a sacrificial filter includes a filter housing filled with PSK filter material.
• the filling of the filter housing, also called filter bed, consists of a plurality of individual PSK particles.
• Victim filters are arranged in the supply line in such a way that the entire aqueous medium to be purified has to flow through them on the way to the pressure-driven membrane separation plant.
• At least one sacrificial filter must be arranged in the supply line, but it is also possible for two, three, four or more individual sacrificial filters to be arranged behind one another or in parallel.
• the number of sacrificial filters depends, for example, on the load on the medium to be cleaned of biofouling-causing constituents or the desired performance of the subsequent pressure-driven membrane separation process.
• Each sacrificial filter can be easily removed from the supply line. If replacement of a sacrificial filter is necessary, remove it from the supply line and insert a fresh sacrificial filter into the supply line.
• the fresh sacrificial filter can be filled with previously unused, new PSK filter material. It can also be filled with PSK filter material from a previously removed sacrificial filter and cleaned.
• At least two devices for arranging a sacrificial filter in the supply line are present in the supply line. Therefore, the presence of at least one sacrificial filter in the supply line is guaranteed even when removing a sacrificial filter, which is flowed through by the entire aqueous medium to be cleaned.
• PSK are the filter material of a sacrificial filter.
• the material and the structure of the PSK are such that the flow conditions and the adhesion probability at the sacrificial filter at least correspond to the corresponding properties at the membrane of the subsequent pressure-driven membrane separation plant.
• the PSK are preferably made of the same type of material, more preferably of the same material as the membrane of the pressure-driven membrane separation plant.
• the PSK consist of carrier material coated with one or more such materials.
• Support material is for example a polyurethane, while the coating consists for example of polyamide, polyethersulfone, polyvinylidene fluoride, or polysulfone.
• sacrificial filters Due to the porous structure of the PSK, sacrificial filters result in a far-reaching filtration removal of the particulate contents of aqueous media. Thus, particulate fouling in the pressure-driven membrane separation plant is significantly reduced. It is possible to compress the PSK differently in the sacrificial filters and thus to change the flow conditions and the filtration effect.
• Devices can be provided between the sacrificial filter and the pressure-driven membrane separation plant, by means of which biocides or biostatics for disinfection can be metered into the permeate of the sacrificial filters, or devices for disinfection by ultraviolet light.
• Figure 1 exemplifies a device according to the invention for the purification of water and schematically.
• aqueous medium 1 in this case impure raw water
• a feed line 2 of a subsequent pressure-driven membrane separation unit 4 in this case a reverse osmosis system (UO)
• UO reverse osmosis system
• membrane permeate 6 is derived by a Membranpermeat-derivative and derived by a Membranretentat-derivative 7 Membranretentat 8.
• the directions of flow of the aqueous medium 1, the membrane permeate 6 and the membrane retentate 8 to be purified are indicated by arrows on the feed line 2, the membrane permeate discharge line 5 and the membrane retentate discharge line 7.
• a sacrificial filter 3 is arranged, which is filled with permeable synthetic collectors, which preferably consist of the same material as the membrane of the membrane separation unit 4.
• the sacrificial filter 3 is flowed through by the entire aqueous medium 1 to be purified on its way to the membrane separation plant 4.
• the sacrificial filter 3 is fixed by means of the holder 9 in the supply line 2.
• a second holder 10 is present in the supply line 2, in which, if necessary, a further sacrificial filter 3 can be used. Not shown are measuring devices for monitoring the turbidity of the filtrate of the sacrificial filter, the pressure loss at the sacrificial filters and the pressure drop and the permeability of the membrane separation plant.

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• Engineering & Computer Science (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Nanotechnology (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (2)

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Citations (2)

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• 2007
  • 2007-10-03 AT AT0155707A patent/AT505282B1/de not_active IP Right Cessation
• 2008
  • 2008-09-21 SA SA08290598A patent/SA08290598B1/ar unknown
  • 2008-09-23 CN CN2008801102753A patent/CN101861200B/zh not_active Expired - Fee Related
  • 2008-09-23 EP EP08804591A patent/EP2197569A1/de not_active Withdrawn
  • 2008-09-23 WO PCT/EP2008/062672 patent/WO2009043760A1/de active Application Filing
• 2010
  • 2010-04-05 TN TN2010000147A patent/TN2010000147A1/fr unknown

Patent Citations (2)

Non-Patent Citations (4)

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