FR2565580A1 - ORGANIC SLUDGE CONDITIONING PROCESS - Google Patents

Abstract

THE INVENTION RELATES TO THE CONDITIONING OF ORGANIC SLUDGE COMING FOR EXAMPLE FROM THE TREATMENT OF WASTE WATER WITH A VIEW OF IMPROVING THE BEHAVIOR TO DEHYDRATION, REDUCTION OF MASS AND VOLUME AND PREVENT OF ROTTING DURING SUBSEQUENT TREATMENTS. THE AIM OF THE INVENTION IS TO ACHIEVE THE PACKAGING WITH LOW ENERGY EXPENDITURE AND WITHOUT THE USE OF CHEMICALS. ACCORDING TO THE INVENTION, A SLUDGE CONTAINING AT LEAST 0.5 OF DRY ORGANIC MATTERS IS ACTIVATED CONTINUOUSLY OR AT PREDETERMINED INTERVALS AT A FREQUENCY OF AT LEAST 0.3 S, OXYGEN BEING INTRODUCED SIMULTANEOUSLY. FOR THE CREATION OF OSCILLATIONS, ONE MAY HAVE RECOURSE IN PARTICULAR TO ROTARY BODIES OR TO VIBRATORS. THE DRY MATTER IS THEN REDUCED TO OVER 80 AT ROOM TEMPERATURE. THE VOLUME OF THE MUD IS REDUCED TO LESS THAN 5.

Description

- 1 -

  The invention relates to the conditioning of sludge,

  containing an essential proportion of organic products

  ques. It is above all sludge from the treatment

  water and biotechnology. The process according to the invention is suitable in particular for improving

  behavior with regard to filtration,

  less rotting during the course of further processing and reduction in mass and volume of

mud.

  When treating organic sludge, the following goals should be achieved: 1. Increasing the concentration of sludge to save volume for subsequent treatment processes;

  2. Improvement of dehydrability with a view to obtaining

  tion of a solid product, for example for the preparation

  tion for treatment on dehydration areas

  mud tank, for artificial filtration or centrifugation; 3. Prevention of rotting during subsequent treatment or permanently (stabilization);

4. Mud disinfection.

  To increase the concentration of sludge, sedimentation is used above all in devices

  thickening or flotation.

  The mass of dry substance is then not reduced while the volume is reduced by about 50%. With the help of sedimentation, only contents can be reached

  in low dry matter. To increase the speed of

  thickening, it is known to have, inside the thickening device, devices of the maple type. It is also known to use vibrators. Thanks to this, an assembly of the solid products takes place and the water is separated. Others

  effects of this procedure are not known.

  Improved dehydration behavior

  is obtained alongside the additive stabilization processes

  tion of flocculating products and by heat treatment. It is also known to obtain a homogeneous colloidal mass

  dispersed, by treatment of a mud activated by oscillations-

  high frequency (ultrasonic). This process does not

  can be implemented only in conjunction with one of the

  following chemical-physical culations since after destruction of the activated sludge flakes, it is necessary

  to carry out a new formation of flakes.

  Currently, we are carrying out essential stabilization-

  aerobic or anaerobic process. A short

  significant reduction in processing time is obtained with

  of the enzymatic stabilization of mud developed by the applicants. The energy expenditure is then approximately

7.5 kWh / m3 of mud.

  Aerobic conditioning processes which are effective under psychrophilic and mesophilic conditions, have a duration of 10 to 17 days, and under conditions

  thermophilic we have reached durations of 3.5 to 5 days.

  The object of the invention is to find a method by which the conditioning time is greatly reduced

  sludge simultaneously with good dewaterability.

  The energy expenditure required must be low and we want to be able to give up the use of chemicals and enzymes. The mud must not rot during the subsequent dewatering stage and must increase its efficiency by a large reduction in volume

and mass.

  The object of the invention is to develop a process which, by creating optimal conditions for the development of microorganisms in a succession not yet known and by the combination of process steps - 3 - which hitherto: could not be combined technically, leads to a modification of the frequency distribution of the individual systematic groups of microorganisms and which, by elimination of the inhibitors which form under natural conditions makes it possible to achieve by overproduction an increase in the activity of these, leads a radical shortening of the whole process of aerobic stabilization of organic sludge and

  a significant decrease in the volume of simulated sludge

  simultaneously with a decrease in the mass of dry matter.

  By making the process take place under psychrophilic conditions (preferred temperature 285 ... 291 K) and by

  creation of marginal electrokinetic, physico-

  chemical and physico-macanic as well as by the influence

  of catalytic activators and by the elimination of inhibitors

  The aim is to make possible a significant saving of energy and a reduction in the volume of reactor required. The applicants have developed a process in which suspensions are caused to pass through a fine-grained filtration layer. Disposal of products

  separated by filtration is carried out continuously without inter-

  tuption of the filtration process using a dirty water pump from an apparatus delimiting a predetermined volume and creating in this volume a direction of

  current opposite to that of the water to be filtered for cleaning

  remove the filtration layer. With the help of a rotating drum, we assist the sand cleaning process, thanks to which we perform a mechanical-hydraulic regeneration of the filtration surface. In order to carry out the dehydration, the following procedure was followed when loading the filtration installation with mud containing organic substances: Excess mud from activation installations (alone and mixed with the untreated and pre-thickened primary sludge) was placed on the filter. This was regenerated at specified intervals

  by the cleaning drum which is driven by a movement

  back and forth. In doing so, a filtrate was removed from the sludge during filtration in an amount which was that which should be expected. The specific resistance to filtration did not change significantly, depending on the temperature of the

  mud, for the first 2 to 3.5 hours.

  At the end of this period, it was surprisingly found that the structure of the mud suddenly changed. Clearly visible flocculation of a structurally different kind occurred than that of the amorphous flakes of activated sludge. By carrying out a more detailed examination, we noted a very strong increase in the Redox potential of 300 ... 500 mV and a sudden decrease in the specific oxygen consumption of the microorganisms by 1.2 mg / (lmin) of oxygen. Then the Redox potential

  lowered quickly from 200 ... 400 mV to +10 mV.

  Despite the very short treatment time, there was no decay of the mud during the subsequent natural or mechanical dehydration. In

  continuing the treatment, these parameters became

  improved for the next 3 to 4 hours, after which the same effect again occurred from the sudden decrease in specific filtration resistance and

  the appearance of good dehydration properties.

  The described effect was presented in a particular way-

  intense when the activated sludge was subjected before treatment for a short period of time to

anaerobic conditions.

  It has also been found that the effect also occurs when the drum does not plunge into the layer.

  of sand and when no liquid is separated by wire-

  tration. It is true that the intensity then decreased.

-5-

  The effect also weakened when during the pro-

  cessus additional quantities of

  mud after the first 90 minutes.

  In the event that the drum did not act within the delimited volume, only one modification had occurred

  fication of the structure of the mud.

  It is on the basis of this discovery that the problem

  has been resolved by activating continuously, or at in-

  predetermined tervalas with a frequency of at least 0.3 s, mud containing at least 0.5% of material

  organic dry and simultaneously introducing oxy-

  uncomfortable. Activation and introduction of oxygen can take place simultaneously within the entire volume

  of reactor, but it's advantageous to operate whole-

  ment the discovered effect, to delimit for this purpose a partial volume, this area being moved at predetermined time intervals or continuously through the conditioning reactor. In doing so, we end up oscillating and aerating the entire volume of mud according to a determined cycle. After 2 to 5 hours of treatment, it is necessary to impose, outside the

  demarcated area, anaerobic conditions. By modifying

  cation of the location of this area delimited internally

  In the reactor, there is a constant alternation of aerobic and anaerobic conditions, which is necessary for the second phase of conditioning the sludge. It is planned to treat the sludge until a Redox potential rise of 300 ... 500 mV is obtained. At the end of a treatment period of 90 to 180 minutes, no other quantities of mud are introduced. In addition, and before aeration, the mud is brought for 30 to 120 minutes to an anaerobic state. The preferred frequency range is 0.6 to 1.25 s1 * The preferred content of organic dry matter is 16 to 40 g / l. The process is intensified by dewatering the mud continuously during the treatment. Metabolic products

  gases are eliminated from the mud, in particular by aeration.

  The dissolved products are removed continuously with the filtrate. In addition, there is a washing of the mud. The dewatering properties of the mud are significantly improved if a granular material is added to the mud during treatment.

  a density different from that of water.

  The creation of the oscillations can be carried out in various ways. To do this, we can use

  in particular to rotating bodies or vibrators.

  All the conditions of the process are particularly advantageously achieved when the mud

  is brought to a granular filtration pitcher.

  Activation is then produced by a rotating body.

  This is located inside a delimited space which is moved above the filtration surface. We then realize several additional effects:

  - regeneration of the filtration layer for de-

  hydration of the mud, - fluidization of the sand to improve the degree of dispersion,

  - ventilation inside an area bounded by locali-

variable position.

  The treatment according to the method according to the invention firstly leads to the use of energy sources

  exogenous, after which endogenous respiration begins.

  Due to the high concentration of organic substances, the above-average respiratory activity of microorganisms and the absence, due to the process, of natural inhibitors, the present mass of the population

  bacteria die suddenly, which makes them bio-

  The polymers formed, the high molecular weight protein compounds and the extracellular polymers adsorbed against the outer walls of the cells cause a flocculation process. Flocculation can be promoted by fluidizing the mud with a granular material (for example sand), whereby the mechanical effect of the activation on the degree

  dispersion of the mud is significantly reinforced.

  At this time, most pathogenic bacteria

  died due to the greatly increased Redox potential.

  The specific oxygen consumption suddenly drops to the value of endogenous respiration (AA = 1.2 mg 02 (1 x min), simultaneously with a decrease in the pH value. The mud is then technically stabilized, that is to say made permanently incapable of rotting, made odorless and dehydratable, at volumes of> 50% and the dry matter envisaged compared

  to the starting quantity is reduced by> 20%.

  When the process is continued beyond this stage in the same way, anaerobic conditions being imposed outside the defined area, within 3 to 4 hours a highly effective combined nitrification and denitrification of the

nitrogen compounds.

  After consumption of exogenous energy sources,

  we attack the internal reserves (polysaccharides, fats).

  Endogenous respiration consumes these products, after which

  finally the oxidation of the cellular protein occurs.

  At the same time the process of oxidation of ammonia begins.

  niac, released during the biochemical oxidation of

  organic substances in NO2 and NO3.

  Since this process consumes oxygen, it turns out that the specific consumption of oxygen

  strongly increase. If the oxygen supply is limited

  tee to a delimited space moving above the sur-

  face of liquid, there occurs in it intensive processes of nitrification leading to the. release of nitric acid. This acid causes, if it is not eliminated from the system, a lowering of the pH and, linked to this, braking

of the process.

  When the defined space, enriched in oxygen, continues to move, the dissolved oxygen is completely consumed in a few minutes due to the very high specific oxygen consumption of the nitrification processes. By

  due to the fact that denitrifying bacteria have the pro-

  please be optionally anaerobic microorganisms, they become active at this time. Using as

  organic substance bacteria killed during breathing

  endogenous organic substance that serves as a source of hydro-

  gene and using the nitric acid formed during ni-

  trification, we realize, thanks to these bacteria and under anaerobic conditions the dissimilative reduction of nitrate

  in N2. At the same time, the assimilation reduction takes place.

  lative of nitrate to organic nitrogen (cellular protein).

  After 3 to 4 hours, it occurs again

  suddenly changes the properties of the mud.

  It becomes easily dehydratable. The additional oxygen supply contributes to the fact that thanks to the

  newly formed microorganisms, organic substances

  Still present and biologically degradable niques are oxidized. At this time, the mud is reduced to approximately 9% of its initial volume and the mass of dry matter is reduced by 70%. After another 2 to 4 hours, the volume decreases to <5% and the dry matter mass to <20%, the properties

dehydration remaining good.

  Thanks to the property of bacteria to attack, during periods of shortage of vital elements (carbon, nitrogen, sulfur, phosphorus, oxygen), their own internal reserves, there is an intracellular depletion of important elements. If after these periods of shortage the bacteria arrive in areas in which there is a surplus

  in these elements, there is an overcompensation.

  - 9 - Thanks to the conduct, in accordance with the invention, of the process, one obtains an intensification hitherto unknown, of biotechnology without the addition of enzymes or chemicals, under psychrophilic conditions, thanks to which one realizes reaction times, including the thickening of the mud, from 4 to 12 hours compared to the 3, 5 to 5 days during the aerobic thermophilic and mesophilic stabilization of the mud and this for an energetic implementation and lower investment. Thanks to the reduction in mass and volume of the organic mud and the low specific filtration resistance, the subsequent dewatering is made more efficient by 300 to 500% and the mud thickening devices for the pre- and post -cleaning become totally

superfluous.

EXAMPLE

  In a wastewater treatment plant with a daily capacity of 210,000 m3 / d, 1,470 m3 / d of primary sludge is obtained having a dry matter content of 40 g / l (of which 65% is organic dry matter), 5,026 m3 / d of activated sludge having a dry matter content of 15g / l and 1470 m3 / d of activated sludge having a

dry matter content of 1%.

  In two storage containers, alternately

  The mud obtained after intensive aeration of 0.5 to 2 hours under anaerobic conditions. The aerobic / anaerobic psychrophilic stabilization of the mud takes place in open basins with a depth of 1.5 m. On the waterproofed bottom, there is a drainage layer with a thickness of 0.1 m, with a drainage pipe by

  running width of basin in granular sand

  metric from 0.6 ... 1.2 mm. Above this layer is

  placed a layer of 30 cm of fine granular sand

  lometry from 0.4 ... 0.63 mm. The free basin depth is 1.1 m. An installation that can be moved in the direction

- 10 -

  longitudinal is arranged on the basin in which, inside an enclosed space, a rotary drum which both fluidizes the upper layer of the fine sand filter, introduces oxygen into the mud and flushes out metabolic products in gaseous form formed simultaneously by microorganisms. In addition, it is

  possible to promote the introduction of oxygen into the

  tallation during the course of the process which need

  specific oxygen level is very high, by adding a-

additional rators.

  The sludge which is subjected to anaerobic conditions in the storage container is conveyed in 20 ... 60 min. passing through an intensive aeration installation in a quantity of 1 m3 / m2 of filtration surface, in the basins for aerobic / anaerobic psychrophilic stabilization

mud.

  At the start of filling, the installation is moved with a speed of 1.5 m / min. in the longitudinal direction above the basin, the drum rotating with a speed of 60 s-1 and plunging 4 ... 6 cm into the layer of

fine sand.

  The Redox potential increases from -200 mV to +100 ..

  400 mV and more. The specific oxygen requirement increases simultaneously to 1.8 ... 2.0 mg 02 / (1 x min), then suddenly decreases after 90 to 120 minutes to 1.2 ... 0.5 mg 02 / (1 x min.). The same trend is noted with regard to

the pH value.

  The installation realizes, next to the important introduction

  aunt of oxygen and the removal of inhibitors of the metabolic process, a very good mixing and dispersion of the mud, whereby very good living conditions are created for microorganisms which metabolize

organic substances.

  After 90 to 180 minutes, about 40% of the liquid phase has been removed in the form of a filtrate comprising, in the state

-.he -

  dissolved in this filtrate, substances which are difficult to metabolize from a biochemical point of view and others

dissolved compounds.

  The exogenous respiration of the mass population, present, tends towards its end. These bacteria die and it is then that begins the phase of endogenous respiration and nitrification of the ammonia formed. The capacity

  of water release from the mud then drops significantly

  ficative. At this point, the mud is unable to rot

  for a while and may be subject to composting,

  dehydration or other treatments.

  If the treatment is continued, the NH + is oxidized with NH + bacteria to HNO and HNO3. For 4 2 lN3. or avoid a sharp reduction in pH that normally occurs

  under these conditions and which is due to the formation of the acid

  of nitric, HNO2 and HNO3 are reduced parallel and simultaneously to the state nitrification process

  anaerobic in nitrogen gas using ana denitrifying agents

  erobes within the same volume of water.

  This process is made possible by the fact that in

  the installation, a technical oxygen saturation is adjusted

  only obtainable. Outside the installation, the dissolved oxygen is completely consumed in a few minutes due to the very high specific oxygen requirement

  (greater than 3 mg 02 (1 x min.)) of the nitrification process

  cation. During the anaerobic conditions then present, the nitric acid formed is immediately reduced. This process lasts until the installation brings in oxygen-saturated water again and until

  nitrification and denitrification take place.

  Thanks to the permanent fluidization of the filtration sand, there is besides the good dispersion of the mud a solid phase for the growth of bacteria, thanks to which we meet regeneration conditions

  significantly more favorable than in the body of water.

  - 12 After 4 to 5 hours, this process reaches its peak. The capacity to yield the mud water suddenly improves again, the specific filtration resistance of the starting mud decreasing at the same time from 2.66 x 101 l 'cm / g to 1.98 x 1011 cm / g. After 5 to 7 hours, 80 to 92% of the liquid phase of the mud is released in the form of a filtrate. The mass of the total quantities of dry substance introduced is reduced to 18%. Mud is incapable

rotting.

  - Pathogenic bacteria are no longer able to live due to the significant increase in Redox potential

  during treatment. The residual mud can be dewatered

  drated in additional steps, since it is then possible to achieve high efficiency due to the low specific resistance to filtration and due to the good dehydration properties, being

  given that the nitrogen compounds which interfere with the process of

  thickening and flocculation no longer act at this time and since a favorable pH range is reached

  for the colloidal system as well as an electro-

advantageous kinetics.

  As it goes without saying, and as already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more particularly envisaged, it embraces it, at

otherwise, all variants.

- 13 -

Claims (14)

  1.- Organic mud conditioning process,   in which the sludge is activated using metered energy   canic or oscillation, characterized in that a sludge containing at least 0.5% organic dry matter is activated continuously or at predetermined intervals at a frequency of at least 0.3 s, from l being oxygen introduced simultaneously.   2.- Method according to claim 1, characterized in that the activation and the introduction of oxygen take place inside a delimited area of the sludge which is then found in a conditioning reactor, this   field being moved through the conditioning reactor   ment at predetermined intervals or continuously.   3.- Method according to claims 1 and 2, charac-   terrified by the fact that after 2 to 5 hours of treatment, anaerobic conditions are established   outside the demarcated area.   4.- Method according to claims 1 and 2, character-   laughed at by the fact that the mud is treated until it is   tion of a Redox potential increase of 300 ... 500 mV.   5.- Method according to claims 1 and 2, character-   laughed at by the fact that after 90 ... 180 min. after the   at the start of the treatment, there is no longer any addition of mud.   6.- Method according to claims 1 and 2, charac-   terrified by the fact that the mud is brought before the intro-   oxygen duction, aerobic for 30 ... 120 min.   7.- Method according to claim 1, characterized in that the sludge containing 16 to 40 g / i of organic dry matter, is activated continuously or at predetermined intervals up to a frequency of 0.6-1 at 1.2 s 1.   8.- Method according to claims 1 and 2, character-   dried out by the fact that the mud is dehydrated continuously during treatment. - 14 -   9.- Method according to claims 1 and 2, charac-   terrified by the fact that metabolism products gases are removed from the mud.   10.- Method according to claims 1 and 2,   characterized by the fact that the mud is washed during treatment.   11.- Method according to claims 1 and 2,   characterized in that, during the treatment, a granular material is added to the slurry, the density of which is different from that of water.   12.- Method according to claims 1 and 2, charac-   terrified by the fact that the creation of oscillations is produced by a rotating body.   13.- Method according to claims 1, 2, 8, 11 and   12, characterized in that the sludge is brought to a granular filtration layer and that it is activated   by the rotary body, the rotary body realizing the fluidi-   sation of the upper part of the filtration layer at predetermined intervals, the filtration grain being   thus brought into contact with the mud.   14.- Method according to claims 1 and 2,   characterized by the fact that the creation of the oscillation is obtained using a vibrator.