DE3920539C1 - Nutrient and fertiliser compsn. prodn. - by aerobic thermophilic fermentation of liq. manures and aerobic mesophilic fermentation - Google Patents

Abstract

Prodn. of nutrient and fertiliser compsn. comprises aerobic thermophilic fermentation of liq. manures at above 50 deg.C to effect sterilisation, then aerobic mesophilic fermentation with minimised denitrification. Opt. nitrates and/or nitrates and/or other nutrient components are added. USE - The process provides valuable fertiliser and nutrients from waste manure liquors.

Description

The invention relates to a method for adjusting the nutrient content of liquid manure, as well as a plant for carrying out the process.

Liquid manure is the most common name for pumpable stable exits. The liquid manure will too today still largely without further preparation cultivation on arable or green areas. The manure However, recovery has been increasing in recent years of criticism, especially from an environmental point of view. This is particularly because of the risk of nitrate there is accumulation in the groundwater due to local over-fertilization. The risk of over-fertilization results in particular from that one in relation to agricultural use Disproportionate amount of manure is spread. This is especially true for farms, who have a high livestock in proportion small agricultural area.

In addition to the groundwater pollution (in particular a build-up of nitrates and sulfates) also counteracts the smell burden of increasing criticism.

Finally, a big problem is that with the spreading of slurry including pathogenic germs be introduced into the soil, which is an increasing ver Spread of so-called factor diseases in masses lead livestock stocks.  

From "Correspondence Wastewater", 31st year, 946 are aerobic thermophilic reactors for the treatment of liquids mist known from animal production plants. With this Circulation aeration process becomes a biological process triggered in the course of which by exothermic reactions the developing thermophilic bacterial flora tempera ture around 60 ° C. That way though partial disinfection of the manure. The nitrate content however, the manure is not significantly reduced, so that the over-thinning problems described at the beginning remain. The breakdown of organic substances is incomplete and the stench becomes corresponding substances only partially broken down.

In addition to the aerobic-thermophilic treatment, there is also one Anaerobic treatment in septic tanks is known, in particular for the production of high-energy biogas. Here too, the following applies Example the nitrogen and phosphorus compounds as well Potassium salts, i.e. the nutrients effective in fertilization obtained almost completely in the liquid residue stay, that is, this procedure also leads to one Fertilizer, the nutrient content of which is practically unchanged compared to natural liquid manure. At the Rhei nisch-Westphalian Technical University of Aachen recently a process for the precipitation of ammonium Sewage designed to reduce the nitrogen content from sewage to eliminate and then selectively as a fertilizer to be able to put. The ammonium is removed with the help of Phosphate and magnesium under certain process conditions involved and failed. It settles in crystalline Shape. The precipitated salt is known to farmers as Full fertilizer available.

Aside from the fact that this procedure is significant requires equipment, allows the known chemical precipitation processes no biological interference  the bacterial flora. In this respect, it also only provides one Partial solution available.

From DE-OS 34 20 433 a method for simultaneous Production of biogas and fertilizers in a three-stage Process known, the biomass in the first process level with growth conditions for mesophilic micro organisms converted aerobically to lower organic acids, the intermediates in the second stage with growth conditions for thermophilic microorganisms due to anaerobes converted to CH₄ and CO₂ and finally in the third Stage the now largely degraded biomass using anaerobes is fully fermented, with the fertilizer and additional biogas. An influence on nutrients the biomass is neither intended nor addressed.

In CH-Z: "Gas-Wasser-Abwasser", 67th year, 1987, No. 3, Pp. 139-148 describes a sludge stabilization process in which the sludge is pre-treated aerobically and thermophilically and then anaerobic-thermophilic digestion will throw. Here too there is an influence on nutrients the biomass is neither addressed nor intended.

The object of the present invention is a possibility the targeted adjustment of the nutrient content and at least to offer at least partial disinfection for liquid manure. The aim is to tailor the treatment process individually to be able to lead so that the liquid manure one the available agricultural area has the appropriate nutrient content and the content at least reduced in potential pathogens, if not eliminated.

The invention is based on the knowledge that a corresponding manipulation of the manure by means of a two stage process can be realized, the manure in the first treatment stage of an aerobic and in the second stage of treatment of anaerobic stabilization is subjected. Another differentiation from leg Flow of the nutrient content takes place to solve the task  in the method according to the invention for adjusting the nutrient content of liquid manure with at least partial decontamination in that

• - to maintain the nutrient content of the liquid manure in a first Level aerobic-thermophilic and without nitrification through self-heating at temperatures above 50 ° C until the liquid manure is decontaminated and then a second step under anaerobic-mesophilic Avoiding denitrification is dealt with wise
• - to reduce the nutrient content in a given Extent of liquid manure aerobic-mesophilic under nitrifying conditions through self-heating treated until the Nitrifi cation or the reduction of the nutrient content is completed before in a second stage to further reduce the nutrient content the liquid manure in the presence of nitrate respectively Nitrite and organic carbon compounds anaerobically thermophilic due to external heating to temperatures above is treated at 50 ° C under denitrifying conditions.

The terms "maintenance" and "Redu decoration "of the nutrient content are to be ver stand that in "maintaining" the nutrient salary either remains unchanged or low is reduced, while in a "reduction" by at least 50%, possibly down to zero becomes. The nutrient content of the processed end product can be within the ranges listed above can be set individually, including by a Variation of the following parameters:

• - In the aerobic first treatment stage: amount of oxygen, Type of introduction of oxygen, temperature, treatment duration,
• - in the anaerobic second stage of treatment: treatment duration, temperature.

The individual treatment stages and procedural steps are explained in more detail below, first  using the example of processing a manure to the greatest possible extent Elimination of the nitrogen content with simultaneous Decontamination.

For this purpose, the sludge material that may have previously been thickened (approx. 10 to 15% by weight dry matter) in one aerobic-mesophilic reactor of a first treatment level subject. The reactor contains a circulator fan, injected into the mud via the oxygen and the Sludge is circulated. The amount of oxygen, the intensity the upheaval and the treatment time is chosen so that maximum heating of the treated manure on 39 ° C takes place.

This leads to a breakdown of organic components the manure, at the same time reducing the stick material by nitrification, that is, the NH₄ portion the manure is with the help of microorganisms in NO₃-N (Nitrate nitrogen) or NO₂-N (nitrite nitrogen) converted. The management of the first aerobic treatment level in the mesophile area is important because the nitrifying bacteria are mesophilic bacteria, their activity optimum is around 30 to 35 ° C. At higher temperatures doors begin those involved in nitrogen oxidation Denature enzymes.

For the rest, the nitrification behavior becomes essential influenced by the proportion of oxygen. The nitrification will accelerated by increasing oxygen levels. The Sauer substance concentrations should be above 2 to 3 mg per liter lie to rapid and complete nitrification to guarantee.  

As soon as the nitrification to the desired extent is completed, the pre-treated manure from the Reactor of the first treatment stage in an anaerobic led reactor of the second treatment stage, in which the manure is subjected to a digestion process. The second stage of treatment under denitrifi ornamental (anoxic) conditions. Advance The setting for this is in addition to the absence of solved Oxygen the presence of nitrate respectively Nitrite as well as the presence of organic carbon links. Under this condition, a Denitri molecular nitrogen and thus another Reduction of the corresponding proportion of nutrients in the Manure can be reached. Is considered microbiologically the oxygen respiration of the corresponding organisms replaced by "nitrate breathing".

Digester gas (CH₄) is produced at the same time. The gas yield is depending on the degradation of the organic substance in the aerobic first treatment level and the lower, ever more mining has already been done there.

This anaerobic digestion process does not occur self-heating of the manure.

For this reason, the reactor is heated externally, and to temperatures above 39 ° C, preferably above 50 ° C and according to a preferred embodiment of Ver  driving above 60 ° C. This enables fiction according to the procedures used in aerobic stabilization biogenic heat released in the first treatment stage to be used as process heat in the second treatment stage, so that the process works quasi self-sufficiently thermally.

The residence times of the manure in the second treatment levels are to be determined on a case-by-case basis. At temperatures above 60 ° C, the decontamination is significantly accelerated and already with exposure times of, for example, 20 hours the pathogens in the manure mostly killed will. This is particularly about disposal Salmonella, but also roundworm, for example eggs, Picorna viruses, foot and mouth disease viruses or Swine vesicular disease viruses (in pig manure).

At the same time, in the second treatment stage Slurry stabilization completed.

By varying individual process parameters, the Nitrogen content of the slurry at the end of the second process level also set to certain predetermined values will. This can be done via an appropriate temperature influence, but especially by an early Abort the length of stay in the individual treatment reach levels.

Under certain circumstances it can also appear be a manure while maintaining as much as possible to prepare the nutrient content while doing the heavy work place particular emphasis on decontamination. This Fertilizer can either be in the prepared form - that is with more or less unchanged nutrient content - are applied, for example, if the one to be treated Soil is under-fertilized, but it can also be used  mixed with a nutrient-reduced fertilizer to to increase its nutrient content in an application-specific manner. In this way, the manure can be in any desired Prepare the mold.

The preparation of the manure with the most upright their nutrient content is maintained in the first Stage aerobic-thermophilic and in the second treatment level anaerobic-mesophilic. In the second treatment denitrification can be prevented. There denitrification only if nitrification has taken place beforehand can take place, comes the setting of thermophilic tempera structures (above 39 ° C) in the first treatment stage a special meaning too. In this way, the Nitrogen largely preserved as a nutrient in the manure. The setting of thermophilic temperatures in the first Treatment stage also ensures disinfection the manure, that is, killing the above Pathogens. The same applies here that the temperature increase in the aerated substrate of the aerobically guided first Treatment level should be carried out into areas, which is safe from an epidemic-hygienic point of view Guaranteed killing of the microorganisms. Preferably the temperature should again be above 60 ° C. By decontamination possible infection routes in subsequent slurry circuit can be eliminated. By aerobic-thermophilic slurry stabilization is about to take place early commitment or elimination of organic stench substances instead. The aerobic Stabilizing released biogenic heat is a function the amount of oxygen introduced and the treatment duration. The same applies here that the oxygen input is at least Should be 2 mg per liter, with the associated reactor  can be designed in the same way as above described.

The biological process becomes through the oxygen aeration initiated and accelerated in the further course, whereby during its course through exothermic transformation lungs of the developing thermophilic bacterial flora the desired thermophilic temperatures immediately adjust yourself.

With normal pig manure and oxygen Entry of 2 mg per liter is with a residence time from 1 to 6 days to be expected to be largely full carry out constant disinfection.

The liquid manure pretreated in this way is then anaerobically further processed in mesophile - as stated above leads - while avoiding denitrification. In this Organic substances, especially coal, become a stage Substance in the manure, eliminated or stabilized lized. The carbon from the microorganisms breathed so that the corresponding stench substances are broken down will.

Here, too, the anaerobic-mesophilic second treatment level releases significant amounts of fermentation gas, which to be immediately dissipated to them - as above described - for example as process heat in anaerobic thermophilic second treatment stage in manure treatment use to reduce the nutrient content.

It is particularly preferred to apply the liquid manure before each first treatment stage of sedimentation treatment subject and only the thickened sedimentation  then slurry up as described above prepare. This way the amount of behan manure significantly reduced. Can accordingly the plants are dimensioned smaller; at the same time becomes an intensification of those described above Reactions reached.

It is particularly advantageous for the respective reactors to design in container construction and together in one arrange portable unit that is easy to the respective Location can be transported. Although this is invented process according to the invention as a batch process or semi-continuous process is made possible light the described treatment of the manure in each two process stages based on the physical Framework conditions a high throughput rate. It can it may make sense on a case by case basis between the two Reactor stages to arrange a buffer tank in which the manure is stored temporarily. The buffer tank can also as a depot for targeted quantity control (mixing) the manure prepared in the first treatment stage serve for the subsequent after-treatment, depending on Set the range of application for very targeted nutrient levels to be able to.

The above statements show that the fiction procedures by a specific setting of the respective oxygen demand and the reaction temperature control the nutrient content and here ins special nitrogen content. At the same time the slurry is detoxified. The lazy won at the same time gas has a calorific value between 5000 and 6000 Kcal / m³ on. It can be used as an external energy source.

A corresponding system is characterized by the characteristics of Claims 3 to 7 described.

Claims (7)

1. Procedure for adjusting the nutrient content of Liquid manure with at least partial decontamination, at that for the greatest possible maintenance of the nutrient the liquid manure is aerobic in a first stage thermophilic and without nitrification through self-heating at temperatures above 50 ° C until decontamination of the liquid manure and then in a second Anaerobic-mesophilic stage avoiding denitrification cation is treated, or to reduce the nutrient content of the liquid manure to a predetermined extent aerobic-mesophile under nitrifying conditions Self-heating is treated until the nitri fication or the reduction of the nutrient salary is completed before in a second Step to further reduce the nutrient content the liquid manure in the presence of nitrate wise nitrite and organic carbon compounds anaerobic thermophilic through external heating to tempera structures above 50 ° C under denitrifying conditions is treated.   2. The method of claim 1, wherein the liquid manure before the first treatment stage of sedimentation subjected to treatment and the thickened sedimentation sludge is processed. 3. Appendix for adjustment of the nutrient content of liquid manure with at least partial de-waxing to carry out the method according to one of the Claims 1 or 2 with a first reactor for aerobic Stabilization of the liquid manure with one device for the introduction of oxygen into the to be treated Medium and a second reactor for anaerobic stabilization liquid manure. 4. Plant according to claim 3, wherein the device for Introduction of oxygen has a circulation aerator. 5. Plant according to claim 3 or 4, in which the or Reactors for the thermophilic treatment of liquid manure are thermally insulated. 6. Plant according to one of claims 3 to 5 with a rotie renden tool, which is arranged so that it the trained above the medium to be treated Foam smashed. 7. Plant according to one of claims 3 to 6 with a front the first reactor arranged sedimentation vessel for thickening the liquid manure to be treated.