DE102007055563A1 - Method and device for treating sludge - Google Patents

Abstract

According to the invention, in at least one first process step, the sludge is subjected to a disintegration process in a disintegration process in which particles and / or aggregates contained in the sludge are at least partially disintegrated, and then in a second process step the sludge is added in a flocculant addition device with flocculant.

Description

The The invention relates to a method and a device for treating of sludge containing organic cells and aggregates of cells, especially biogenic sludge such as sewage sludge.

biogenic Sludges are of animal or human origin and are a mixture of liquid phase or liquid, mostly water, and solid phase or solid particles, include biogenic particles or organic solids and are like Cells and microorganisms, especially bacteria, and aggregates it. Additionally, in biogenic sludges also be dissolved organic and inorganic substances and also a gas phase, for example in the form of gas bubbles or dissolved Gas, be included, the gas in particular from decomposition processes or, in particular aerobic or anaerobic, degradation of organic Substances in the mud comes. A sewage sludge is one in the Wastewater treatment occurring biogenic sludge.

to Purification of waste water is used in sewage treatment plants, usually after a mechanical pre-cleaning have a primary clarifier, in which unresolved Deposits substances such as faeces and paper, etc. or on float up the surface. The corresponding pre-clarified wastewater is now fed to a biological stage in which Microorganisms and supply of atmospheric oxygen organic matter of the wastewater and inorganic substances are partially oxidized. A common procedure for this biological stage is an activated sludge process in an aeration tank with a downstream secondary clarifier. In the activated sludge process the biogenic ingredients of the wastewater are added by adding Activated sludge containing masses of flocculent aggregated bacteria, and by aerating in the aeration tank biotic oxidative aerobically degraded. As a result, aerobic bacteria become carbon compounds in wastewater mostly to carbon dioxide degraded and partially converted to biomass and the nitrogen from the organic compounds by other bacteria to nitrate transformed. The activated sludge process is operated continuously. In the secondary clarifier, the activated sludge is settled by settling separated from the wastewater and a part of the sludge is called Return sludge returned to the aeration tank, sufficient for the concentration of microorganisms in the aeration tank to hold up. The so-called excess sludge, which through the increase in biomass in the secondary clarifier has arisen, is for further treatment together with the primary sludge the Vorklärbeckens thickened in a Voreindicker and then pumped to an anerobic degradation in a digester. The sludge is then after passing through a Nacheindickers a Mud press fed for drainage and then disposed of. There are also known installations in which no primary sedimentation tank is available. Here then only the excess sludge from the secondary clarifier over the pre-thickener in usually fed without digester the sludge press and the drained sludge then disposed of.

To the Dewatering or drying of sewage or industrial sludge a method is known in which the sludge is passed through a filter unit, in particular a chamber filter system, or a centrifuge (decanter) which consists essentially of water Liquid portion of the mud squeezes out and the solid So it filters out ingredients from the mud. The mud is before dewatering a flocculant (flocculant), the polymer contains added to the degree of dehydration or to increase the degree of drying of the sludge, ie to drain the mud better. The mode of action of Flocculants can be thought of as such that the polymers Solid particles in the sludge in flakes or flocculation to bind together by electrical attractions and thereby helping or improving their separation from the water. The filtered dehydrated dry matter is also called Filter cake called. The polymers also improve the passage of the water through the filter cake at the subsequent sludge gene.

From the DE 198 08 156 A1 a device for conditioning conditioner for aqueous sludge is known with a dissolving chamber to which are supplied from a stock solution pump funded drug stock solution and under pressure inflowing additional water, a dissolving chamber downstream mixing chamber in which a rotating distributor head for mixing in the Dissolving chamber formed mixture of active substance stock solution and make-up water is arranged, and with a mixing chamber downstream buffer memory, which is connected via a metering pump with a seed device which emits the mixed in the mixing chamber drug solution as a conditioning agent to the flowing in a delivery pipe aqueous sludge. The distribution head has distributed about its axis of rotation substantially parallel to the axis of rotation extending longitudinal slots as fluid outlets for the approach of the dissolving chamber mixture and radially outward, and along the axis of rotation extending mixing vanes. The mixture then flows through the slit-shaped fluid outlets to the outside in the mixing chamber and is mixed there by the mixing blades. The speed of the distributor head is in a range between 700 U / min (revolutions per minute) and Operated at 2,500 rpm. The mixture of active ingredient stock solution and make-up water introduced from the dissolving chamber is guided from below into a shaft of the distributor head, then exits through the slots and, after being mixed by the mixing blades, is led out of the mixing chamber again directly through a lateral outlet.

The Effectiveness of the biological treatment stage in sewage treatment plants can be increased by using so-called homogenizers or disintegrators for treating the sewage sludge, in particular of the return sludge, primary sludge or excess sludge and also of the sludge. Through these homogenizers or Desintegrato ren on the one hand, the size the solid particles in the sludge reduced and homogenized and thus a larger effective surface provided for the dismantling, and on the other hand become attached to the cell walls of the cells adhering enzymes (exoenzymes) and biogenic particles detached and reintroduced into the fluid and also by at least partial destruction of the cell walls from the cells themselves released endoenzymes. All these measures increase the efficiency of biodegradation by the microorganisms in the sludge, especially biological activated sludge Degradation stage. For homogenization or disintegration of sewage sludge in the biological degradation stage of sewage treatment plants are different Methods and devices already known.

DE 100 40 546 A1 discloses a system for the mechanical disintegration of biogenic sewage sludge having a rapidly rotating head and head having radial apertures and radial vanes.

The DE 100 40 545 A1 also discloses a system for mechanical disintegration of biogenic sewage sludge in which the sewage sludge in an initial state comprises microorganisms in the form of cells and a solid essentially composed of aggregates of the cells and suspended matter and in which a disintegration process destroys aggregates and destruction of cells, wherein in a first disintegration process primarily the destruction of aggregates is caused and in a subsequent, separate second disintegration process primarily the destruction of cells is caused. In the first disintegration process, the sewage sludge is preferably claimed with separating parts such as strip-shaped wings and possibly additionally with slot-like openings of a rotary blade device and the cells are destroyed only to a very limited extent, but released by the destruction of aggregates enzymes that destroy cells. In the second disintegration process, the sewage sludge is preferably treated with an ultrasonic homogenizer or by means of high-power pulses, and cells are destroyed by the resulting cavitation directly and to a considerable extent.

The WO 2005/028375 A1 discloses a method for crushing or disintegrating particulate substances in suspensions of microorganisms in a carrier medium, in particular in effluents or sludges of biological sewage treatment plants, in which the support medium is pumped into a constructed in the manner of a Laval nozzle flow channel with narrowing and then widening cross section under pressure and It accelerates quickly and then decelerates again, causing hydrodynamic cavitation in the Laval nozzle.

Of the Invention is based on the object, a new method and a new device for treating sludge, the organic Contains cells and aggregates of cells, especially biogenic Sludge such as sewage sludge, to be specified.

The Invention is based on the consideration, when withdrawing from Liquid or liquid phase, in particular water (Dewatering), from such sludges before clogging of flocculant in an upstream disintegration step Aggregates of organic cells and the organic cells themselves at least partially disintegrate, so destroy, break up, unlock, dissolve and / or to crush.

The Disintegration, destruction or dissolution of the Cell aggregates or cell aggregates leads to a Separation of cells or smaller average cells or cell group size or particle size and thus to a larger surface which the flocculant can accumulate or which it can wet. The flocculant can now contain a larger amount of Water or general fluid molecules of displace the cells, which at the same added amount of flocculant per unit of sludge, the degree of dryness of the sludge clearly increased.

The disintegration or destruction or disruption or disruption of the cells, in particular their cell membranes in all cells and microorganisms such as bacteria, archaea and fungi or in plant cells of the (additional) cell wall, makes access to the cytoplasm or cell interior, in a percentage of typically 80 to 95% water. By this disintegration of the cells now not only the water from the cell interior can partially escape and be supported by the flocculant separated from the solid phase of the mud, son In addition, the flocculant may also bind or attach to the cell membrane and possibly the cell wall, as well as constituents of the cells contained in the cell interior or cytoplasm and attributable to the solid phase, and separate them from the water or the liquid.

It it was found that the upstream disintegration process with the resulting Zellaggregat- and cell disruption clearly the degree of drying of the subsequent with the flocculant offset sludge increased in a subsequent drying process.

In a preferred embodiment is when disintegrating Cavitation generated in the mud. Cavitation is the arising gas-filled cavities in a liquid, when the static pressure is below the vapor pressure of the liquid falls, which is typically a few millibars. It then forms by the local short-term evaporation of the liquid Gas bubbles that when the static pressure exceeds the vapor pressure again Implosion-like practically collapse at the speed of sound. Arise in the collapsed cavities thereby very high pressures of possibly thousands bar. Cavitation therefore arises when the flow velocity exceeds a corresponding value, so that the static pressure correspondingly below the vapor pressure drops. The cavitation leads to enormous inertial forces in the medium or Mud, which causes the disintegration of cell aggregates and cells.

For generating the cavitation in the sludge during disintegration, any method known per se can be used, for example the use of ultrasound or high-power pulses or stirred ball mills, for example as in DE 100 40 545 A1 described, or a hydrodynamic process such as in WO 2005/028375 A1 described, where, as described there each upstream of a further disintegration with a rotating rotor, so a two-stage disintegration can be provided.

In a particularly advantageous embodiment is for Disintegrating the sludge before flocculant addition at least a rotor is used, which in the sludge, in particular in a flow space, in which the mud flows, rotating about its axis of rotation becomes. Preferably, cavitation is also generated with the rotor by the rotor at a rotational speed or speed in the Mud is rotated, which depends on the texture and flow of the mud and the geometry of the rotor is set, controlled or regulated so that cavitation in the mud on the rotor, in particular on each rotor blade occurs, or, in other words, above the cavitation limit. The speed of the rotor is also dependent from the pressure in the sewage sludge, ie the static pressure, as well as from the flow rate of sewage sludge and thus the dynamic pressure of sewage sludge. print and flow rate of sewage sludge again depend on the delivery pressure of a conveyor, especially a pump, for the mud and the geometry the flow channel or space in which the sewage sludge flows and in which the rotor is arranged, and of the Viscosity of the sludge. From certain flow rates, correspondingly higher rotational speeds, the rotor occurs at the rotor surface, especially the rotor blades, a larger one stationary cavity, so a coherent Gas layer surrounding the rotor blades. One speaks then of full cavitation in comparison to partial cavitation, in which individual Gas bubbles arise on the surface. The full cavitation is clearly more advantageous from the slightly more uniform surface loading as a partial cavitation.

The for the occurrence of partial cavitation or full cavitation respectively required The speed of the rotor will be specific to each given system Sizes and parameters such as the geometry of the flow space and the rotor, the sludge properties, in particular viscosity, and the mud pressure or delivery pressure empirically or metrologically or theoretically or by simulation and during operation set. The speeds required for cavitation can be very different depending on the situation from the geometry of the rotor, in particular its diameter. In In practice, rotors with speeds between 3.300 and 4,500 rpm, but these values are not restrictive Limits dar.

In In one embodiment, the or each rotor at least one, in particular at least two, breakthroughs and / or Slits and / or recesses and / or elevations or protrusions, which project in particular from the axis of rotation to the outside, on. Preference is given to the rotor demolition edges and / or cutting edges and / or shear edges formed, in particular, contained in the sludge In particular, disrupt aggregates of cells or crush or split. In a particular embodiment the rotor has at least one, in particular at least two, Rotor blades on. It can also be tooth-like Projections in the manner of a gear or a saw blade be provided. In addition, in addition or only edges at breakthroughs or Slots may be formed in the rotor.

Furthermore, several rotors can be side by side, in particular star-shaped or parallel be arranged to each other.

For mixing or introducing the flocculant into the at least partially disintegrated sludge, any known apparatus or method may be used, for example according to DE 198 08 156 A1 , In particular, the flocculant is introduced or inoculated into the sludge via a rotating mixer or mixing head. Any flocculant suitable for the specific application and sludge may also be used as the flocculant, with the flocculant usually being introduced in the form of a solution of an active substance, in particular of an aqueous polymer solution, ie as a liquid flocculant.

In an advantageous combination of a disintegration rotor for Disintegrate and a mixing rotor or rotating mixing head for introducing the flocculant a modular system is proposed, which comprises a rotary drive, which from the outside to a wall a room in which the sludge is located, in particular one Flow space or a flow tube, fastened or attachable and at the drive shaft either either the disintegration rotor or the mixing rotor can be coupled or are fastened.

there is preferably a mechanical seal when coupling the disintegration rotor for sealing in the mud or flow space for the Mud arranged so that the sludge cools the mechanical seal. Preference is given to a disintegration unit which contains the disintegration rotor and the mechanical seal comprises, attached as a unit to the wall and the disintegration rotor on or to the drive shaft of the drive coupled or arranged and releasably attached rotatably, in particular by means of clamping screws.

at On the other hand, coupling of the mixing rotor becomes a feeding system with at least one feed channel for the flocculant coupled with and a mechanical seal for sealing in the Feeding arranged, so that the flocculant the mechanical seal cools. Preference is given to a mixing unit, which is the mixing rotor, the flocculant delivery system and the mechanical seal includes, attached as a unit to the wall and the interference rotor coupled or arranged on or to the drive shaft of the drive and releasably secured rotatably, in particular by means of clamping screws.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19808156 A1 [0005, 0021]
• - DE 10040546 A1 [0007]
• - DE 10040545 A1 [0008, 0016]
• WO 2005/028375 A1 [0009, 0016]

Claims (20)

Process for treating sludge, the organic Contains cells and aggregates of cells, especially biogenic Mud like sewage sludge, in which a) in at least a first step of the sludge a disintegration process is subjected to aggregates of cells contained in the sludge and cells themselves are at least partially disintegrated, b) then in a second process step, the sludge is added with flocculant. The method of claim 1, wherein the flocculant added sludge in a third step a mechanical Drying process is subjected, in particular a filter press, for example, a chamber filter press, or fed to a centrifuge becomes. A method according to claim 1 or claim 2, wherein the sludge added to the sludge means the separation of the liquid phase or liquid, especially water, of solids, including solidifying cells, of mud or reinforced. Method according to one of claims 1 to 3, wherein the solid particles and / or solid cell components of mud and flocculent flakes of various sizes be formed and liquid, especially water, the Mud is released. Method according to one of claims 1 to 4, where the flocculant attaches to the surfaces of cells and cell components of disintegrated cell aggregates and / or Cells attached. Method according to one of claims 1 to 5, in which at or by the disintegration of the cells, in particular the cell membranes and possibly the cell walls, cell fluid released from the cytoplasm or cell interior, especially cell water becomes. Method according to one of claims 1 to 6, in which the flocculant cell membranes and possibly cell walls and in the cell interior or cytoplasm, the solid phase attributable components of integrated cells binds or itself attached to it and this from the water or the liquid separates. Method according to one of the preceding claims, in which the disintegration process at least two disintegration steps wherein, in a first disintegration step, primarily the disintegration of aggregates is caused by cells, in particular by means of a rotor rotating in the mud, and in a subsequent, second Disintegration step primarily the disintegration of cells is effected. Method according to one of the preceding claims, in the disintegration process, cavitation in the mud is produced. The method of claim 9, wherein the cavitation in Mud by means of ultrasound or high-performance or high-pressure pulses or hydrodynamically, in particular by means of at least one cavitation nozzle is produced. The method of claim 9 or claim 10, wherein cavitation in the sludge by means of a rotor rotating in the sludge with a speed set above the cavitation limit or at a speed that depends on the condition and Flow of the mud and the geometry of the rotor is adjusted, controlled or regulated, that cavitation in the Sludge occurs on the rotor is generated. Method according to one of the preceding claims, wherein in the at least one first method step at least a rotor is rotated in the mud for performing a Disintegration process. A method according to claim 8 or claim 11 or Claim 12, wherein the rotor at least one, in particular at least has two rotor blades. A method according to claim 8 or claim 11 or Claim 12, wherein the rotor at least one, in particular at least two, apertures and / or slots and / or recesses and / or has projections or projections and / or demolition and / or cutting and / or shearing edges, in particular Rupture aggregates of cells and / or cells contained in the sludge or crush or split. Device for treating sludge, in particular biogenic sludge such as sewage sludge, with a) at least a disintegrator for disintegrating the sludge, b) at least one of the disintegration device in the flow direction the sludge downstream flocculant-mixing device for Mixing flocculant in the mud. Apparatus according to claim 15 with one of the flocculant mixing device in the flow direction of the sludge downstream filter press or Centrifuge for drying the sludge. Apparatus according to claim 15 or claim 16, wherein the at least one disintegrator means one in the mud having rotating or rotatable rotor. Apparatus according to claim 17, wherein the rotor at least one, in particular at least two rotor blades and / or wherein the rotor has at least one, in particular at least two, breakthroughs and / or slots and / or Having recesses and / or surveys or projections and / or has tearing and / or cutting and / or shearing edges, the particular contained in the sludge aggregates of cells and / or Tear or break up or break up cells. Apparatus according to claim 17 or claim 18, wherein the speed of the rotor of at least one disintegration device adjustable, controllable or adjustable above the cavitation limit is. Device according to one of claims 15 to 19 with a flow space through which the mud flows, wherein the disintegration means and the flocculent mixing means are arranged on or in the flow space.