WO2009092821A1 - Traitement de boues biologiques - Google Patents

Traitement de boues biologiques Download PDF

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Publication number
WO2009092821A1
WO2009092821A1 PCT/EP2009/050862 EP2009050862W WO2009092821A1 WO 2009092821 A1 WO2009092821 A1 WO 2009092821A1 EP 2009050862 W EP2009050862 W EP 2009050862W WO 2009092821 A1 WO2009092821 A1 WO 2009092821A1
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Prior art keywords
sludge
concentrate
pressure
permeate
units
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PCT/EP2009/050862
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English (en)
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David Ulmert
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David Ulmert
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Publication of WO2009092821A1 publication Critical patent/WO2009092821A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • 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
    • B01D61/145—Ultrafiltration
    • B01D61/146—Ultrafiltration comprising multiple ultrafiltration steps
    • 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
    • B01D61/149—Multistep processes comprising different kinds of membrane processes selected from ultrafiltration or 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
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • 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
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/025—Thermal hydrolysis
    • 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
    • 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
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/06—Specific process operations in the permeate stream
    • 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
    • B01D2311/08—Specific process operations in the concentrate stream
    • 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
    • B01D2311/18—Details relating to membrane separation process operations and control pH control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2319/00—Membrane assemblies within one housing
    • B01D2319/02—Elements in series
    • B01D2319/025—Permeate series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2319/00—Membrane assemblies within one housing
    • B01D2319/04—Elements in parallel
    • 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
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/02—Temperature
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/03—Pressure
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/06—Controlling or monitoring parameters in water treatment pH
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/44—Time
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/06—Pressure conditions
    • C02F2301/066—Overpressure, high pressure
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/04—Disinfection
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage

Definitions

  • This invention pertains in general to the field of treatment of sludge, such as entirely or partly biological sludge. More particularly the invention relates to a method of treatment of sludge, such as entirely or partly biological sludge.
  • Sludge e.g. from industrial and municipal sewage water works, are usually treated in a digester.
  • the treated sludge is either a pure biological sludge or a mixed, partly biological sludge, i.e. from pre-sedimentation, biological purification and post- precipitation.
  • the sludge consists of biological material that is decomposed by the anaerobic treatment of the digester and to some extent transformed into methane gas.
  • the digestion process leads to smaller amounts of sludge and the methane gas is an environmentally friendly energy source.
  • sludge hydrolysis of the sludge before digestion gives a sludge that is more easily dewatered, such as by centrifugation. Also, the amount of sludge is decreased, in comparison with digestion without hydrolysis. In addition, the production of methane increases, since organic molecules and molecule complexes that are hard to break down, are decomposed into smaller molecule structures that are more easily broken down e.g. by bacteria.
  • the sludge can be hydrolyzed by lowering the pH with a strong acid, by heating the sludge, or by a combination of acid treatment and heating. Sludge from sewage plants, normally has a 1 to 3% content of dry substance. To decrease the amount of sludge that is to be treated thermally, it is common that a thickening of the sludge is first conducted. For example, this can be done by centrifugation of the sludge.
  • a coagulant in the form of a polymer such as polyacrylamid, sometimes needs to be added.
  • the need of such coagulants may be an undue economical stress to the user, and may also have an adverse effect on the environment.
  • the sludge After dewatering, the sludge is heated under pressure to the desired temperature and is then allowed to react (hydrolysis) at the elevated temperature for a period of about 30 minutes. Finally, the sludge is cooled wherein heat from the cooling process is usually recycled. The cooled sludge is then lead to be treated in a digester.
  • a known method of hydrolysis is thermal treatment of the sludge (the Cambiprocess) wherein the sludge is heated under pressure to about 15O 0 C for 30 minutes.
  • the sludge herein normally has a 1 to 3% content of dry substance. To decrease the amount of sludge that is to be treated thermally, a thickening of the sludge is first conducted.
  • the chemical sludge may thus contain e.g. precipitated aluminum or iron phosphate. In some cases, it may be desirable to separate the phosphor from the sludge.
  • Kemira AB and Alfa Laval AB have developed a method for separating phosphor from digested sludge (the Krepro process). In the Krepro process, digested sludge is dewatered through centrifugation. The dewatered sludge is made acidic, with for example sulfuric acid, to pH 1 to 2. Then, the sludge is heated to about 14O 0 C and is allowed to react in a tank for about 20 minutes. Low pH and high temperature leads to dissolution of the metal phosphates.
  • the sludge that is hydrolyzed through heat and acid treatment becomes easy to dewater.
  • the cold, hydrolyzed sludge is preferably dewatered by centrifugation. Reject water from the centrifugation step will comprise dissolved phosphate and the metal ion that has been a part of the salt that was used for precipitation of phosphate from the sewage water.
  • Trivalent iron is added to the reject water, e.g. in the form of iron chloride and the pH-value is adjusted to about 3 e.g. with lye, whereby sparingly soluble iron phosphate is precipitated.
  • the precipitated iron phosphate is separated. If the sewage water has been precipitated with an aluminum salt, the aluminum ions will still be dissolved at pH 3, whereby the phosphate free reject water can substitute "clean" aluminum salt as a precipitation agent.
  • the separation of phosphor from the sludge is performed after digestion of the sludge and subsequent dewatering, which renders the method dependent on several construction units, such as centrifuges, heating tanks, digesters, etc, which renders the method disadvantageous with regard to time and energy consumption.
  • Thickening the sludge by dewatering with centrifuges is, as indicated above, a treatment using considerable amounts of energy, which is costly and has a high environmental impact. Furthermore, use of polymers may also be costly and have an adverse effect on the environment.
  • the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above-mentioned problems by providing a method for treatment of sludge comprising elevating the pressure or temperature of the sludge; and filtrating the sludge in one or more ultra filtration and/or micro filtration units, whereby a concentrate and a permeate is obtained, said concentrate comprising substantially all said suspended biological matter and said permeate comprising substantially no suspended biological matter, said sludge having a pH between 5 and 9 during the whole process.
  • Fig. 1 is a process scheme according to one embodiment of theinvention
  • Fig. 2 is a process scheme according to another embodiment of the invention.
  • UF in combination with hydrolysis gives great energy savings in a wastewater treatment plant or in sewage plant works compared to conventional dewatering steps, such as e.g. centrifugation, since the energy consumed by UF may be recycled to a great extent in form of heat. This is thanks to the fact that the electrical energy that is added to the circulation pump(s) mostly is transformed into heat and may be used for heating the sludge and for the thermal hydrolysis. With traditional technology, where centrifuges normally are used for dewatering, a significant amount of energy is also used, but no part of this energy can be used for heating the sludge.
  • UF is working at temperatures well below 100 0 C, such as from 20 to 50 0 C.
  • sludge is viscous and its content of cells, proteins, fat and other macromolecules makes the flux low and the risk of fouling is therefore high.
  • the high temperature at which UF according to the present invention is working leads to sludge with low viscosity, which gives a high flux.
  • the high temperature makes cell walls burst, proteins coagulate and macromolecules disintegrate. This also contributes to a high flux and decrease the risk of fouling.
  • the heat formed in the UF step or steps according to embodiments of the present invention may also be advantageously heat exchanged with incoming sludge.
  • the technology with UF may thereby give significant energy savings, even considering that ultra filtration in many cases in itself is an energy demanding process.
  • the temperature of the sludge for ultra filtration may be in the interval of 100 to 250 0 C, and preferably in the interval of 100 to 200 0 C, such as in the interval of 140 to 165 0 C.
  • the present invention has the advantage over the prior art that it allows for a recycling of the energy that is used for sludge dewatering. Also, no thickening chemicals have to be added according to the invention.
  • a sludge such as a sludge entirely or partly consisting of biological suspended matter, is treated in accordance with the flow chart of Fig. 1.
  • the sludge has neutral or basic pH.
  • a pump 111 pumps incoming sludge 110 into the system and increase the pressure so that it, in all parts of the system, exceeds the pressure of evaporation of water at the specific working temperature.
  • the pressurized stream of sludge is distributed over two heat exchanges 112 and 113.
  • heat exchanger 112 the sludge is subject to heat exchange with hot UF permeate 122, exiting from UF units 115, 116, and 117.
  • heat exchanger 113 the sludge is subject to heat exchange with the hot UF concentrate 123, exiting from UF units 115, 116, and 117.
  • the UF units 115, 116, and 117 may be replaced by one single UF unit, or other combinations of UF units and/or micro filtration units, such as UF units connected in parallel and/or series as described below.
  • the concentrated flow from the UF units may intermediately be led to a tank 121, the purpose of which is described more carefully below.
  • the incoming flow of sludge may be distributed e.g. proportional to the flow of permeate and concentrate, respectively.
  • heat energy 114 may be added to compensate for possible heat loss of the system. This heat energy 114 may for example be the addition of hot steam.
  • the heated sludge is treated with ultra filtration (UF) and/or micro filtration.
  • UF ultra filtration
  • the three UF units 115, 116, and 117 are connected in series.
  • Pumps 118, 119 and 120 are pumping sludge through UF units 115, 116, and 117, respectively.
  • the sludge is put under elevated pressure in one or more pressurizing pumps, the effect of which will be describe more extensively below.
  • This pressure preferably exceeds or equals the pressure of evaporation of water in every point of the UF unit.
  • the flow rate through the membrane canals is preferably high.
  • the pumps 118, 119, and 120 may have significantly more capacity compared to pump 111. From each UF unit there is an outflow of permeate, whereby the concentration of the suspended matter, such as biological suspended matter, in the sludge is increasing in the concentrate.
  • the concentrate may be partly re-circulated over the membranes and partly transferred to the next membrane step, as illustrated in Fig. 1.
  • the concentrated sludge may be recycled under pressure in each UF step.
  • Start of hydrolysis of the sludge partly depends on sludge retention time and partly on the working temperature.
  • the hydrolysis of the sludge may start already in the UF step, i.e. the UF units, depending on the generated heat therein, and the heat added.
  • positioning a tank 121 in one of the particular UF steps further induces hydrolysis.
  • the concentrated flow from the last UF step is then led to the tank 121.
  • the hot concentrated sludge may get a retention time being sufficient for achieving optimal hydrolysis.
  • the sludge may be kept at an elevated temperature in tank 121, also for achieving optimal hydrolysis.
  • Such a retention time and temperature may preferably be in the interval of 15 to 45 minutes and a temperature in the interval of 100 to 250 0 C, and preferably in the interval of 100 to 200 0 C, such as in the interval of 140 to 165 0 C.
  • the UF permeate 124, exiting the UF units or heat exchanger 112 may then for example be used directly as a carbon source and the UF concentrate 125, exiting the UF units, tank 121, or heat exchanger 113, may be further digested.
  • Factors that may be used to characterize the UF is setup of the filter(s), operating pressure, operating temperature, membrane material, membrane characteristics and transmembrane pressure.
  • the method may be performed over one or more UF units and/or micro filtration units, such as ultra filtration membranes. More specifically, in one embodiment of the invention, the UF membranes are connected in series. In another embodiment of the invention, the UF membranes are connected in parallel. In yet another embodiment of the invention, the UF membranes are connected both in series and in parallel. In further embodiments according to the invention, one or more UF membranes of the abovementioned embodiments may be replaced by one or more micro filtration membranes.
  • the sludge is put under elevated pressure in one or more pressurizing pumps until a pressure is achieved.
  • the splitting of the elevation of pressure on several pumps, such as a pump before each UF unit may be beneficial in respect of the stress on the pumps.
  • other pumps may make up for the decrease in pump capacity, rendering the pressure on at least some of the UF units and/or micro filtration units satisfactory for achieving the demanded filtration effect.
  • this pressure exceeds or equals the pressure of evaporation of water in every point of the UF unit.
  • the flow rate through the membrane canals is preferably high, such as 6 m/s.
  • the flow rate through the membrane canals is in the order of 5 m/s.
  • the flux is partly depending on the transmembrane pressure.
  • the transmembrane pressure is preferably in the interval of 2 to 5 bar.
  • the average transmembrane pressure is about 3 bar.
  • the sludge is heated through heat exchange with e.g. hot UF permeate and concentrate, respectively, exiting from the UF unit(s). This is done to achieve a desired operating temperature.
  • the heat exchange means that most of the heat brought to the UF may be recycled. In order to compensate for systemic heat loss, energy may also be added to the sludge.
  • this energy addition is made by injecting hot steam 114.
  • the sludge may be lead to one or more UF steps.
  • the membranes used in the UF units and/or micro filtration units have to be able to withstand the heat and pressure produced. Suitable membranes, which satisfy these demands, are ceramic membranes.
  • each filtration step there is a production of permeate, which means that the sludge (concentrate) is having an increasingly higher content of dry substance (DS) after passing each filtration step.
  • the membrane surface in each UF step and the number of UF steps at a given flux may be adapted partly to the amount of sludge that is to be treated and partly to the content of DS that is desired after the final UF step.
  • the same content of DS may be achieved as in conventional dewatering equipment, i.e. 10 to 20%. Suspended substances and molecules in the sludge, larger than the membrane cut-off, cannot pass the membranes.
  • the cut-off of the membrane should preferably be 10 to 500 kD.
  • the hot sludge (UF concentrate) is lead to a reactor tank after concentration with UF, where it is retained for a retention time.
  • the total retention time for the sludge depends on the temperature and may vary from 15 to 60 minutes. In one embodiment of the invention, a retention time of 30 minutes at 165 0 C gives a good thermal hydrolysis.
  • the hydrolyzed sludge may be subject to heat exchanged with a part stream of the incoming cold sludge before it may be led to one of the process steps of the sewage treatment works.
  • the hot UF concentrate stream is lead to a flash tank 210.
  • the flash tank 210 may be provided with an overpressure.
  • the hot sludge concentrate stream may contribute to maintaining the working temperature of the digester.
  • Another advantage with this embodiment, comprising a flash tank is for example that the cells in the incoming hot UF concentrate stream to the flash tank will explode due to the pressure drop when entering the flash tank. Thus, the cell walls of the cells will rupture, whereby a higher degree of digestion of organic material in the subsequent digester may be obtained, which in turn may result in a higher degree of methane production.
  • Example 1 In an embodiment of the invention according to Fig. 1, one example of a setup for dewatering and hydrolysis of sludge according to the invention is described.
  • the pump 111 pumps incoming sludge 110, with pH between about 5 to about 9, into the system and increase the pressure so that it, in all parts of the system, exceeds the pressure of evaporation of water at the specific working temperature.
  • the pressurized stream of sludge, with pH between about 5 to about 9, is distributed over two heat exchanges 112 and 113.
  • the sludge, with pH between about 5 to about 9 is subject to heat exchange with the outward-bound, hot UF permeate 122 and in heat exchanger 113, the sludge is subject to heat exchange with the outward-bound, hot UF concentrate 123.
  • the incoming flow of sludge may be distributed e.g. proportional to the flow of permeate and concentrate, respectively.
  • heat energy is added 114 to compensate heat loss of the system, e.g. by addition of hot steam.
  • the heated sludge with pH between about 5 to about 9, is treated with ultra filtration (UF).
  • UF ultra filtration
  • three UF steps 115, 116 and 117 are connected in series.
  • the pumps 118, 119 and 120 are pumping sludge, with pH between about 5 to about 9, through one UF respectively.
  • the pumps 118, 119 and 120 have significantly more capacity compared to pump 111.
  • each UF step there is an outflow of permeate, with pH between about 5 to about 9, whereby the concentration of sludge, with pH between about 5 to about 9, is increasing in the concentrate that partly is re- circulated over the membranes and partly are taken to the next membrane step.
  • the concentrated flow from the last UF step is lead to a tank 121, where the hot concentrated sludge, with pH between about 5 to about 9, has a final retention time to achieve optimal hydrolysis.
  • the outward-bound cold UF permeate 124, with pH between about 5 to about 9, may then be used as a carbon source and the outward-bound cold UF concentrate 125, with pH between about 5 to about 9, may be further digested.
  • pH is between 5 and 9.
  • the hot UF concentrate stream 123 is lead to a flash tank 210.
  • the flash tank 210 may be provided with an overpressure.
  • the overpressure may for example be 0,1 to 0,5 bar, i.e. that the pressure in the flash tank 210 is 1,1 to 1,5 bar.
  • water vapor 211 is released when the hot UF concentrate stream 123 enters the flash tank 210, since the pressure in the hot UF concentrate stream 123 is well above 1,1 to 1,5 bar, such as 3 to 8 bars.
  • the level of sludge may be kept substantially constant, such that a flash tank sludge concentrate stream 212 may be drawn off from the bottom of the flash tank 210 while a flash tank water vapor stream 211 may be drawn off at the top of the flash tank 210.
  • the sludge concentrate stream 212 may then be led to a digester.
  • the flash tank water vapor stream 211 may be led to, and thereby mixed with, the incoming sludge stream 110.
  • the pump 111 is replaced by two pumps I l ia and 11 Ib, which are positioned in each of the part streams of the incoming sludge stream 110.
  • Mixing of the flash tank water vapor stream 211 with the incoming sludge stream 110 may be performed on the suction side of the pump 111b. According to another embodiment, said mixing may however also be performed in a setup with the pump 111 simply replacing the second heat exchanger 113. All of the incoming sludge stream 110 may be led to the first heat exchanger 112 and be subject to heat exchange with the hot UF permeate stream 122, or only a part of the incoming sludge 110 is subject to heat exchange in the first heat exchanger 112. The water vapor stream 211 may thus heat the incoming sludge stream 110, or a part of the incoming sludge stream 110. In the embodiment according to fig.
  • FIG. 2 an example of a setup is shown, wherein the water vapor stream 211 heats part of the incoming sludge stream 110 and part of the incoming sludge stream 110 is subject to heat exchange in the first heat exchanger 112.
  • the hot sludge concentrate stream 212 may contribute to maintaining the working temperature of the digester.
  • Another advantage with this embodiment, comprising a flash tank 210 is for example that the cells in the incoming hot UF concentrate stream 123 to the flash tank 210 will explode due to the pressure drop when entering the flash tank. Thus, the cell walls of the cells will rupture, whereby a higher degree of digestion of organic material in the subsequent digester may be obtained, which in turn may result in a higher degree of methane production.
  • Another advantage with this is that there is no need for low pH to rapture the cells. This is advantageous since there is no need for adjusting pH with expensive chemicals, in order to allow digestion. Another advantage is that materials used in the plant, such as piping, do not need to be as anti-corrosive, such as durable for low pH. Thus, cheaper materials may be used in the plant.

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  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Hydrology & Water Resources (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Treatment Of Sludge (AREA)

Abstract

L'invention concerne un procédé de traitement des boues issues des installations d’épuration d’eaux usées, lesdites boues comportant des matières biologiques au moins en partie suspendues. Le procédé selon l’invention comporte les étapes consistant à augmenter la pression des boues ; et à filtrer les boues dans une ou plusieurs unités d’ultrafiltration et / ou de microfiltration, un concentré et un perméat étant ainsi obtenus, ledit concentré comportant sensiblement la totalité desdites matières biologiques suspendues et ledit perméat ne comportant sensiblement aucune matière biologique suspendue.
PCT/EP2009/050862 2008-01-25 2009-01-26 Traitement de boues biologiques WO2009092821A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
SE0800183 2008-01-25
SE0800183-6 2008-01-25
SE0801328-6 2008-06-05
SE0801328 2008-06-05
SE0801523 2008-06-27
SE0801523-2 2008-06-27

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CN101948231A (zh) * 2010-10-14 2011-01-19 北京科技大学 对污泥进行机械预脱水的高浓度污泥厌氧消化处理工艺
CN106861436A (zh) * 2017-03-16 2017-06-20 安阳工学院 一种利用纳米陶瓷超滤处理烷基化废酸工艺
CN112023704A (zh) * 2020-08-13 2020-12-04 合肥禹王膜工程技术有限公司 一种钛酸钡超细粉体清洗的陶瓷膜设备

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NL1006100C1 (nl) * 1997-05-21 1998-11-25 Patrick Walthie Werkwijze en inrichting voor de verwerking van vloeistoffen die verontreinigd zijn met vaste, zwevende, opgeloste stoffen en emulsies.
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* Cited by examiner, † Cited by third party
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CN101948231A (zh) * 2010-10-14 2011-01-19 北京科技大学 对污泥进行机械预脱水的高浓度污泥厌氧消化处理工艺
CN106861436A (zh) * 2017-03-16 2017-06-20 安阳工学院 一种利用纳米陶瓷超滤处理烷基化废酸工艺
CN112023704A (zh) * 2020-08-13 2020-12-04 合肥禹王膜工程技术有限公司 一种钛酸钡超细粉体清洗的陶瓷膜设备

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