Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2000-11-13
2003-07-15
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S641000, C210S650000, C210S651000, C210S600000, C210S607000, C210S610000, C210S612000, C210S175000, C210S195200, C210S257200, C210S903000
Reexamination Certificate
active
06592763
ABSTRACT:
The present invention relates to a method for treating aqueous flows in a bioreactor and alit ultrafiltration unit, wherein the effluent from the bioreactor is supplied to the ultrafiltration unit, in which it is separated into a permeate flow and a concentrate flow.
The present invention furthermore relates to a device for treating aqueous flows in a bioreactor, an ultrafiltration unit and a membrane filtration unit, which device is provided with the necessary pipes and pumps, whereby a separation into a permeate flow and a concentrate flow takes place in said ultrafiltration unit, which permeate flow is connected to a membrane filtration unit via a pipe. The present invention furthermore relates to the use of such a device.
Such a device is known from German Offenlegungsschrift No. 196 14 214. With the device which is known from said publication, waste water is first subjected to an ozone treatment or a similar catalytic decomposition process, for example by means of H
2
O
2
and UV radiation, and subsequently it is supplied to a bioreactor. In the bioreactor, a biological conversion takes place, wherein the effluent is led to an ultrafiltration unit, in which it is separated into a permeate flow and a concentrate flow. The permeate flow thus obtained is supplied to a buffer vessel. The effluent from the buffer vessel is then supplied to a nanofiltration unit, in which nanofiltration unit a separation into purified water and retentate takes place, which retentate is subsequently supplied to the bioreactor again together with the concentrate from the ultrafiltration unit. From the said German Offenlegungsschrift it can only be derived that the water which has been purified at the nanofiltration unit can be used as process water for industrial or agricultural purposes, for example.
Such a method is furthermore known from Japanese patent application JP 09 271771, which discloses a method for purifying water which is contaminated with volatile organic compounds, using a reverse osmosis type membrane. According to the method which is known therefrom, the contaminated water is led to a storage tank, after which it is pumped to an ultrafiltration membrane unit under pressure, whereby the concentrate flow produced in the ultrafiltration membrane unit is recirculated to the storage tank. The permeate flow which is also produced at the ultrafiltration membrane unit is then led to a reverse osmosis type membrane, S wherein the waste flow which is produced at said membrane is also recirculated to the storage tank. The product flow from the reverse osmosis type membrane unit is discharged. The use of the product flow produced at the membrane filtration unit is not known from said Japanese patent application. Moreover, no biological conversion takes place, as there is no bioreactor.
Such a method is also known from Japanese patent application JP 63 069598, which discloses a method for raising the phosphorous content in a dewatered sludge cake. Thus, waste water is subjected to a biological treatment step, wherein the sludge which is produced in said treatment step is supplied to an ultrafiltration membrane unit, in which it is separated into a slurry and a permeate water flow. Said permeate water flow is furthermore separated into a concentrated liquid flow and a product flow in a reverse osmosis type membrane, wherein the product flow is brought into contact with an adsorption agent for the purpose of removing phosphorous. The concentrated liquid flow is then mixed with the excess biological sludge from the biological treatment step, and with the sludge from the ultrafiltration membrane unit, whereby the mixture thus obtained is subsequently dewatered and the obtained water flow is recirculated to the biological treatment step. It is not known from said Japanese patent application to reuse the product flow, from which the phosphorous has been removed, in an advantageous manner. Moreover, the concentrated liquid obtained at the reverse osmosis type membrane must first be mixed with other liquid flows and then be dewatered, after which the recirculation to the biological treatment step is finally effected.
A similar method is known from International patent application WO 96/25368, wherein first solid constituents are removed from a strongly concentrated waste water flow, which flow is then heated to a temperature of 30-35° C. and subsequently subjected to an anaerobic fermentation process. The effluent obtained from said anaerobic fermentation is supplied to an ultrafiltration unit. According to this method, the aqueous waste flow is eventually separated into a substantially pure water flow, a methane-containing gas flow and a residual flow, in which organic and inorganic constituents are present, which residual flow serves as a starting material for liquid fertilizer. There is no recirculation of process flows in this method. One drawback of such a method for treating aqueous flows in a bioreactor and an ultrafiltration unit is that a residual flow is produced, which contains few useful constituents. Although such a residual flow can be used as a starting material for liquid fertilizer, it will have to be regarded as a waste product in practice. The costs of discharging such a residual flow will become higher, due to the increasing antipollution tax, which will have a negative effect on the total processing costs involved in the treatment of aqueous waste flows.
Accordingly, it is an objective of the present invention to develop a method and a device for treating aqueous flows, wherein the aforesaid drawbacks are avoided.
Another objective of the present invention is to develop a new method and a device wherein waste water is purified to such a degree that a substantial part of the purified water can be reused in the processing process.
Another objective of the present invention is to develop an essentially closed circuit water system, so that it is no longer necessary to pump up fresh ground water each time. The previously pumped-up ground water can be purified time and again after being used in the production process and subsequently be reused as process water.
According to the present invention, the method for treating aqueous flows as referred to in the introduction is characterized in that a separation into a product flow and a discharge flow containing dissolved substances takes place in the membrane filtration unit, which discharge flow is supplied to the bioreactor, wherein the product flow is recirculated to the aqueous flows to be treated so as to obtain an essentially closed circuit water system.
In practice it has become apparent that the discharge flow, which contains dissolved substances, can be reused in an advantageous manner by supplying said discharge flow to the bioreactor anew. Thus, an additional conversion of the useful materials in the discharge flow which are to be microbiologically converted takes place in the bioreactor.
According to the present method, the product flow which is produced in the membrane filtration unit is recirculated to the aqueous flows to be treated, in order to obtain an essentially closed circuit water system. The phrase “recirculated to the aqueous flows to be treated” is to be understood to mean that said recirculation takes place to the ground water, process water or to the ground water, process water that has thus been processed in the production process. The phrase thus comprises the embodiment wherein the ground water, process water has not been supplied to the production process yet as well as the embodiment wherein the ground water, process water has already been supplied to the production process. The use of an essentially closed circuit water system will reduce the need to pump up fresh ground water time and again, since the quality of the product flow that is obtained in accordance with the present invention is such that this product flow can be reused as process water.
In order to achieve high biological conversion rates in the bioreactor, it is preferred to recirculate the concentrate flow from the ultrafiltration unit to the
Benedictus Hendrik Rienk
Van Der Meer Walterus Gijsbertus Joseph
Van Winkelen Jacobus Cornelis
Fortuna Ana
N.V. Waterleiding Friesland
Seed IP Law Group PLLC
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