WO2010060751A1 - Method for the hygienization of animal breeding premises - Google Patents

Abstract

The invention relates to a method for the hygienization of animal breeding premises, in particular pigs, that comprises processing liquids containing organic materials in suspension, such as effluents from a nitrification-denitrification biological processing plant, particularly preceded by centrifugation, characterised in that it comprises the steps of flocculation, coagulation, and settling during which the liquid effluent to be processed is subjected to a preliminary dilution, to the addition of lime, and to the addition of a ferric ion solution, after which a pasty phase and a strongly-basic liquid supernatant are recovered, and in that it comprises using at least partially said strongly-basic liquid thus obtained in order to flush animal dejections so as to ensure the hygienization of the environment in animal breeding premises.

Description

 METHOD FOR HYGIENIZING ANIMAL BREEDING ROOMS

The present invention relates to a method for treating liquids containing suspended organic materials, such as pig manure, cattle or duck or poultry, effluents or methanization sludges or denitrification stations, and then recycle the effluent resulting from this treatment to hunt manure in breeding rooms to improve breeding conditions and its effectiveness.

Slurry consists of all liquid and solid animal waste and possibly containing straw or other litter materials. This product is rich in nitrogenous matter, in organic or mineral form.

Generally, the manure is spreading thus giving off odorous odors, source of strong olfactory nuisances for the neighborhood.

A number of processes are known for treating a slurry, such as that described in document FR-2,808,792-A, comprising the following steps:

- Addition of quicklime or slime directly into the manure: this precipitates a part of the ammoniacal nitrogen, organic matter in suspension, phosphorus in the form of calcium and potassium salts.

- Decantation recovery of sludge that is removed and a liquid phase H ₁ . - Driving gaseous ammonia by a flow of air: the liquid phase H ₁ is treated by air entrainment so that the mineralizable nitrogen content volatilizes to gaseous ammonia driven by the air flow. The ammonia thus volatilized is neutralized with sulfuric acid in the form of ammonium sulphate.

Sodium chloride addition: the liquid phase resulting from the preceding stage is mixed with a sodium chloride and with sulfuric acid. These additions are intended to obtain a minimum conductivity value and a pH between 6 and 9. - Electroflocculation: this makes it possible to precipitate suspended matter and colloids in the form of flocs, to precipitate phosphorus and to oxidize organic matter. In addition, sodium chloride gives rise to hypochlorites with bactericidal characteristics.

- Flotation separation of the flocs then decantation to collect sludge and a purified liquid free of bacteria and containing hypochlorites.

Such a method has the particular disadvantage of obtaining low abatement rates, not be adapted to variations in manure composition and produce an output effluent unstable as rich in sulfide.

The document FR 2 903 096 describes a process for treating pig slurry comprising in particular a step during which ferric chloride and a milk of lime are added with stirring. But such a process has a lack of reliability thus rendering it unattractive on the industrial level.

Also, it is an object of the present invention to provide an improved process for treating any liquid containing suspended organic material such as pig, cattle or duck slurry, effluents or methanation sludges, sludge or sludge. denitrification station for example, which overcomes the disadvantages above. Another aim is to provide such a process which makes it possible to divide this liquid into three main categories of products: the first solid that can be used to fertilize the soil, the second liquid to be recycled to drive the slurry in the breeding rooms or for irrigation and the third being a solution of ammonium sulphate to fertilize soils.

A further object of the present invention is to provide such a method of hygienization which makes it possible, in particular in the case of pig manure, to reduce the odors of the piggery and the rate of ammonia in the atmosphere thereof and to reduce quantities of pathogenic microorganisms, this having a beneficial effect, on the one hand, on the personnel by suppressing in particular causes of pulmonary affections, and, on the other hand, on the pigs' performances by improving their health condition, in particular because of a better quality of the atmosphere prevailing in the pigsty.

These and other objects which will become apparent are attained by an improved process for treating any liquid containing suspended organic matter such as effluents from a biological nitrification treatment station denitrification, in particular preceded by a centrifugation, said process comprising flocculation, coagulation and decantation operations during which the liquid effluent to be treated is subjected to a prior dilution, an addition of lime, then an addition of a solution of ferric ions, and at the end of which a pasty phase and a strongly basic liquid supernatant are collected, and in that at least a portion of said strongly basic liquid thus obtained is used for the purpose of removing animal waste in order to hygienize the animal. atmosphere of the animal breeding rooms.

The invention also relates to a method for hygienising rooms for breeding animals, in particular pigs, involving a treatment of liquids containing suspended organic matter, such as slurry of pork, cattle or duck or effluents or methanation sludge, comprising:

A first step of homogenizing and reducing the amount of suspended matter in the liquid to be treated, in particular by centrifugation;

a second stage comprising the flocculation, coagulation and decantation operations, during which the liquid from the first stage is subjected to a prior dilution, addition of lime and addition of a solution of ferric ions, and at the end of which a pasty phase and a strongly basic liquid supernatant are collected; A third gaseous washing step of said supernatant during which the ammonia contained therein is exhausted to produce a strongly basic hygienized liquid, and using, at least in part, said highly basic hygienized liquid thus obtained to drive away animal waste to hygienize the atmosphere of the animal breeding rooms. Advantageously, the liquid subjected to the first step of decreasing the amount of suspended matter is homogenized beforehand.

According to a particular characteristic of the invention, the dilution operation prior to the addition of lime is carried out with a part of the highly basic liquid supernatant resulting from the prior treatment of a liquid containing organic matter in suspension, obtained by the setting implementation of the method of the invention.

According to a particular characteristic of the invention, the first step is carried out by centrifugation to obtain a solids concentration of less than 3 g / l.

According to a particular characteristic of the invention, after the first step, the collected liquid is diluted so that it has a solids concentration of less than 1500 mg / l.

According to a particular characteristic of the invention, during the first step, the liquid to be treated is added with a water-soluble cationic polymer, in particular a cationic polyacrylamide powder. The flocculation, coagulation and settling operations, in particular during said second stage, advantageously comprise three times:

* a first time during which lime is incorporated, under a slow stirring between 80 and 150 revolutions / minute for a tank having a diameter less than 3m, then a second time during which the solution of ferric ions, for example in the form of ferric chloride, is added with rapid stirring of between 200 and

250 rpm for a tank having a diameter of less than 3 m, and

"A third time which consists of a decantation to collect, on the one hand a pasty phase and, on the other hand a supernatant.

According to a particular characteristic of the invention, lime is added at a dose of 4 to 9 kg / m 3 of liquid to be treated.

According to a particular characteristic of the invention, the lime is added in the form of quicklime comprising at least 85% of quicklime (CaO) or a milk of such lime.

According to a particular characteristic of the invention, the addition of ferric ions is carried out in the form of addition of ferric chloride at a dose of 400 to 800 ppm / m3 of liquid to be treated.

The highly basic hygienized liquid obtained generally has a pH of between 11.5 and 12.5. According to a particular characteristic of the invention, the washing of the breeding rooms is carried out by flushing the droppings of the animals with the aid of said highly basic liquid in a plurality of gutters extending parallel to one another, preferably horizontally on the the floor of the breeding rooms, and placed under clumps.

According to an advantageous variant of the invention in post-weaning, flushing is carried out every two days on a daily basis.

According to a particular characteristic of the invention, during the fattening phase, one or two hunts per day are carried out.

According to a particular characteristic of the invention, the flushing is carried out after the gutter, in order to adapt the volume of liquid to the amount of dirt contained in each gutter. According to an alternative embodiment of the present invention, the method comprises a last step during which the liquid from the third stage is oxygenated, in order to obtain a water of recyclable quality, making it possible in particular to consider rejecting it in the natural environment.

The following description, which is not limiting in nature, will enable those skilled in the art to better understand the implementation and the advantages of the method according to the present invention, particularly in the light of implementation examples described in FIG. view of the annexed drawings, on which

FIG. 1 diagrammatically represents the operation of an installation for implementing the method according to the invention, involving the treatment of pig manure, and FIG. 2 similarly represents an installation involving the treatment of an effluent from biological treatment of denitrification of slurry.

Pig manure is a liquid that includes liquid and solid manure from pigs, and possibly straw or other litter material. It is therefore rich in organic nitrogen and generally comprises from 6 to 10% by weight of dry matter.

The method according to the invention therefore involves treatment of slurry and its hygienization, followed by washing of the breeding rooms. According to the present invention, the process for treating such slurry comprises a first step to reduce the amount of dry matter: this is for example done by centrifugation to collect the compostable solid fraction and a liquid whose dry matter content is further lowered by adding water or the liquid from the second stage of the process up to between 500 and 2500 mg / l of dry matter.

During the first centrifugation step, the raw slurry (10) is homogenized via a mixer in the pre-treatment tank (12). A water-soluble cationic polymer (14), for example FLOPAM FO 4350 SH, may be added at the inlet of the centrifuge (16) to improve phase separation. The polymer allows a better agglomeration of the colloids and a decrease of the suspended solids (MES) in the centrifuge outlet liquid and a stabilization of the rate of these MES at the dose of 110 to 150 g / m3 according to the content of MS to obtain the desired values.

This polymer can be removed 4 months a year, from June to September, the heat producing the same effect as the polymer and naturally allowing the agglomeration of colloids. The centrifugation, for example carried out in a Guinard D2L centrifuge, 4500 rpm, 1.5 m ³ / h, is controlled by optimizing the settings to obtain a solid (18) at the centrifuge outlet of 29 to 31% of MS and a liquid (20) whose MES level is between 2 and 3 g / 1. The solid part (18) will be used to make compost in a composting station (22). The liquid part goes to the tank or reactor (12).

The second stage of the process takes place in the reactor (12) comprising stirring or stirring means into which the liquid (20) from the first stage is introduced. This second step includes the following operations: Dilution:

The mixing tank (12) is a cylindrical tank HDPE (high density polyethylene), conical bottom. It is equipped with two mixers: a variable speed mixer for the incorporation of additives and a slow speed mixer (one revolution / min), placed in the base of the tank to concentrate the sludge. The tank (12) is placed on strain gauges to measure the inputs and outputs. Routinely, in the tank (12), 1 to 2 m ³ of supernatant (ie the liquid part at the end of decantation, step 3) is stored for 1 m ³ of centrifuge outlet liquid according to the concentration of MES (between 2 and 3 g / 1). This supernatant must advantageously be at a pH of between 12 and 12.5. The mixture :

In the tank (12) (where only the supernatant remains), the following successive times are observed: ^{1st stage} : addition of lime (CODECAL type) in the supernatant residue at a dose of 6 to 9 kg / m ³ of liquid centrifuge output (according to the rate of MES, the more the liquid is charged, the more lime is added) + agitation from 80 to 150 rpm for about 10 minutes to obtain a liquid of between 12 and 12.5.

^2nd time: Arrival of the centrifuge output of liquid in the vessel (12) + 80 stirring at 150 revolutions / min for 15 min which will cause the formation of flocs (flocculation).

^3rd time: Added ferric ions as ferric chloride at a dose of 400 to 600 ppm / m ³ centrifuge liquid outlet (to obtain a turbidity level of between 15 and 20) + rapid stirring of 200 to 250 rpm for about 15 minutes. This step will allow the magnification of the flocs by the agglutination of the colloids (coagulation) contained in the mixture slurry + lime.

Decantation :

When the flocculation and coagulation phases are complete, the agitation is stopped to allow the flocs to descend to the bottom of the tank (12). After one to two hours of settling, a clear supernatant (24) and sludge are obtained

(26) rich in lime.

The sludge will be sent to a filter press (28), or in a storage tank continuously agitated the supernatant will be sent to the stripper ie the tank (30). The equivalent of Im ³ to 2m ³ of supernatant per m ³ of centrifuge outlet liquid will be retained for dilution (second stage).

Stripping:

Stripping consists of extracting the maximum amount of ammonia contained in the liquid obtained after decantation. The stripping takes place in a tank of 8 m ³ , the bottom part containing the liquid, the upper part allowing it to be sprayed in a column of air. The meeting of the air and the countercurrent liquid allows the ammonia contained in the high pH liquid (between 12 and 12.5) to be discharged and sent to the gas scrubber (32). The stripping of a batch (3 m ³ of slurry input station) lasts approximately 2 hours. If a heat source is available, it is possible to heat the liquid slightly to facilitate extraction of NH ₃ . Once this step is completed, the liquid goes into the storage tank (34) to be used for hunting or irrigation. The washing of the gas:

The ammonia-laden air from the stripping, as well as the air recovered from the associated tanks and pits, is blown into the scrubber (32) through a mist of water and sulfuric acid. The chemical reaction between the acid and the base (ammonia) allows the formation of a salt, ammonium sulfate, and purified gases (36) (oxygen and hydrogen) that are released into the air. The ammonium sulphate (NH ₄ J ₂ SO ₄ thus obtained is stored in a tank (38) in the form of a solution at a concentration of 7% to 8%, in order to avoid the release of ammonia, the vessel ( 12), the centrifuge (16) and storage pits (general storage of upstream slurry, storage of centrifuged liquid, storage of sludge) are covered and the recovered gases (40) are sent to the scrubber (32). can also recover the air from the composting and send it to the scrubber.These operations make it possible to suppress all releases of gas (NH ₃ , methane, H ₂ S etc.).

Finally, the process of the invention may also comprise parallel steps for treating the solid parts obtained, such as: composting and the filter press.

Thus, the solid resulting from centrifugation can be sent to a composting station, where it will remain 3 months before being usable for spreading or marketing (28). The sludge is sent to a filter press and will produce cakes (42) and clear liquid (44) recycled in the station. These cakes (42) can be ground and used as a calcium amendment.

The lime added during the first stage comprises, in this embodiment example, at least 85% of quicklime or is a milk prepared from it.

The liquid resulting from the washing may be, in a fourth step, oxygenated for example by spraying in air, to complete the extraction of ammonia and cause a drop in the COD. The liquid resulting from the process according to the present invention can be used at least in part for washing the breeding rooms of pigs. This allows for the daily evacuation of animal waste and the elimination of releases of ammonia (NH ₃ ) and hydrogen sulphide (H ₂ S) in the breeding rooms. In addition, when washing with the liquid resulting from the process according to the invention, the very basic pH of this liquid makes it possible to obtain an effect of hygienization of the rearing premises.

In addition, this liquid having a strongly basic pH, it is therefore advantageous to use a portion to dilute the liquid from the first step. Because of this high pH, the liquid from the fourth stage, when used to wash the breeding rooms, plays a role in the fight against any pathogens that may be present. According to a particular embodiment, the dilution of the liquid resulting from the first step is carried out by a part of the supernatant which is left in the reactor.

Finally, the solid products resulting from the decantation, rich in calcium, can constitute an amendment either as such, or by mixing them with the compost obtained during the first stage. Example 1

1000 kg of pig slurry having the following composition were treated:

MES 38.8 g / 1 NH ₄ 3.31 kg / m ³

P ₂ O ₅ 1.46 kg / m ³

K ₂ O 1.75 kg / m ³

This slurry, whose solids content is between 2.8 and 3.8% by weight in general, is centrifuged so that after centrifugation its dry matter content is after dilution of 500 to 2500 mg / 1. This low dry matter content, of low variability, makes it possible not to have to vary the input of subsequent products.

As for the dry matter removed, it is composted and thus constitutes a natural organic fertilizer rich in phosphorus.

At the end of this preliminary step, 969 kg of a liquid product is collected which is subjected to the second step of the process according to the present invention.

9 kg of lime containing 85% by weight of quicklime and then 1.3 kg of a solution of commercial ferric ions at 41% by weight are incorporated for about 10 minutes, while stirring slowly (100 rpm). of iron with rapid stirring (200 rpm).

A supernatant is thus recovered: the ammonia released is washed with a sulfuric acid solution to obtain, on the one hand, purified gases and, on the other hand, a fertilizing solution rich in nitrogen and sulfur.

The final liquid is a technically recyclable water used to flush slurry in pig breeding rooms in this case. These results of the analyzes carried out on the co-products resulting from the process of the invention are recorded in the table below. Table 1 Compost

Table 2 Cakes

Table 3 Ammonium sulfate

Table 4: Technical water

N Iron Lime Nitrogen pH Copper Zinc BOD COD Potash Total Turbidity (CaO) ammonia kg / T g / kg kg / T kg / T mg / kg mg / kg mg / L mg / L kg / T

0.28 0, 4 1.16 0, 3 12.08 0.21 0.52 2955 4239 1.48 14.73 The method according to the present invention finally comprises a washing operation or "flushing" of the breeding rooms.

According to an advantageous embodiment, the washing consists in passing a hygienised liquid (pH between 11.5 and 12.5) in the gutters placed under the gratings of the pigs in order to expel their droppings.

This method makes it possible to eliminate the nauseating odors associated with the fermentation of manure (H ₂ S and mercaptans), as well as the release of gaseous ammonia (NH ₃ ). In addition, at each wash, the high pH liquid cleans and disinfects the gutters.

1. Technical data

Number of washes per day:

• in post weaning, 0 to 1 hunt are carried out per day.

• in fattening, 1 to 2 hunts are carried out per day.

The washes are made gutter gutter, not all together, to have sufficient pressure and adjust the amount of liquid depending on the degree of soiling of the gutter concerned. The duration of a wash is 6 to 10 seconds per gutter.

Amount of liquid used:

• in post-weaning, on average 240 liters / room / wash, for a room of 61 m ² housing 128 pigs (or 0.47m ² / pig), equipped with 8 gutters of 11 meters long.

• in fattening: on average 700 liters / room / wash, for a room of 120 m ² housing 144 pigs (or 0.83 m ² per pig), equipped with 16 gutters 15 meters long. Washing under maternity and under pregnancy can also be achieved. It will bring a better overall health status of the livestock.

Necessary material :

An automaton, a pump, pneumatic control valves and gutters whose characteristics are as follows: polyethylene gutters, from a depth of 30 to 35 cm, width at the top of 40 to 46 cm, at the bottom of 16 cm, slightly rounded at the bottom. The gutters are interconnected by a plastic slide in the form of an angle at the upper edges. Gutters should be placed on a flat, horizontal floor. The slope of the flanks is oriented at an angle of 55 to 65 °.

2. Zootechnical improvements and atmosphere At the level of the atmosphere

The data mainly concern ammonia and odors.

The establishment of the flushes with the effluent according to the invention allows a reduction of gas emissions in the building of:

• Ammonia: 70% • Methane: 75%

The washing with hygienised basic effluent allows a strong reduction of odors in the rooms.

A study was conducted in the post-weaning rooms with strips with hunts and strips without hunts and on an empty room serving as a control. It consisted of two components: sensory analysis by several juries (administrative staff and technical staff of the station, analysis of volatile compounds by micro-extraction in solid phase) The results of the sensory analysis show that for 82% of the respondents, the room without hunts presents very uncomfortable smells, whereas for the room with hunts it is only 20% of the people who are really embarrassed by the smells.

The differences in concentration of volatile organic compounds (VOCs) between the two farming methods are as follows:

• Room with hunts: VOC of 85 μg / m ³

• Traditional room: VOC of 441 μg / m ³ is a level 5 times higher.

Livestock results and health expenditure

Pregnant sows and cow-calf shops are not equipped with a hunting system.

In post-weaning:

The effect of the hunts with the strongly basic hygienized effluent on the piglets in post-weaning was quantified by comparing the performances obtained in rooms with or without evacuation of the fresh manure.

Les chasses ont permis une amélioration du gain de poids de 4,3% sans modification de l'efficacité alimentaire et une réduction des problèmes sanitaires qui étaient essentiellement, pour le lot sans chasse, respiratoires et digestifs.

The hunts allowed an improvement of the weight gain of 4.3% without modification of the food efficiency and a reduction of the sanitary problems which were essentially, for the batch without hunting, respiratory and digestive.

In fattening:

The effect of the hunt with the strongly basic hygienized effluent on pigs in fattening was quantified by comparing the performances obtained in rooms with or without evacuation of the fresh manure.

Hygienization of rooms:

Given its high pH (11.5-12.5), the effluent used for washing has no bacteria and no pathogenic virus for pork. The results of bacteriological analyzes conducted on the raw manure and on the hygienized liquid at the outlet of the treatment station according to the method of the invention are indicated in the table below.

* responsible for diarrhea in pigs and may cause enterotoxemia (death within 2 to 3 hours) A study was also conducted to enumerate faecal streptococci developed on contact boxes placed in various areas of the farm:

At the end of the post-weaning, once the room emptied (animals out), and

After washing the gutters of this same room with the basic effluent used and complete cleaning of the room with the hot water cleaner.

Interpretation:

(0-10 colonies) - »Very good

(11-30 colonies) - »Good

(31-100 colonies) - »Acceptable

(101-300 colonies) → Bad

(> 300 colonies) -> Very bad

This experiment shows that the gutters washed with the strongly basic effluent of the invention accompanied by a washing of the room with the hot water cleaner no longer have any fecal coliform when entering the new band. In breeding conditions, the conditions are very good at the bottom of the box, acceptable at the level of waterers and feeders, almost acceptable on the caillebottis and bad only in the gutters. According to a variant of the process of the invention as illustrated in the appended FIG. 2, in which the identical elements corresponding to those of FIG. 1 have been designated by the same reference numerals, the liquid containing the organic matter in suspension is constituted by effluents from water treatment plants by nitrification-denitrification (46), usually preceded by a centrifugation operation with a biological process. In such a case of coupling with a biological process, the treatment according to the invention is simplified as illustrated in FIG. 2. In fact, the nitrogen is already extracted, but the end goal remains the same: to have a hygienised liquid for be able to wash the breeding rooms. Most of the effluent from the biological treatment will have to be treated as previously described, by flocculation, coagulation and settling in the tank (12). The amount of liquid required for post-weaning and fattening washing is about 700 to 750 liters per pig. The quantities to be treated in a biological station are approximately doubled. However, the amount of nitrogen contained in slurry remains substantially the same, the station time will be reduced.

The hygienization process according to the invention thus makes it possible:

»Reduce the levels of NH ₃ and odors in breeding rooms and thus improve the breeding environment by reducing the lung problems of animals and their caregivers;

to induce a rupture in the infectious cycles transmitted by the excrement or favored by the contact between these excrements and the animals, and; to improve the hygienic conditions of the farms and in particular to improve the digestive physiology of the animals, to reduce the veterinary preventive and curative treatments, to reduce the intestinal sensitivity of the animals to the nature or the quantity of the bolus, to improve the zootechnical efficiency of food.

Claims

1. A method for hygienising rooms for breeding animals, in particular pigs, involving a treatment of liquids containing suspended organic matter, such as effluents from a biological nitrification treatment station denitrification, in particular preceded centrifugation, characterized in that it comprises flocculation, coagulation and decantation operations during which the liquid effluent to be treated is subjected to a prior dilution, an addition of lime, and then an addition of a solution of ferric ions, and at the end of which a pasty phase and a strongly basic liquid supernatant are collected, and in that at least a portion of said strongly basic liquid thus obtained is used for the purpose of expelling animal excrement to hygienize the atmosphere of the animal breeding rooms. 2. Process for the hygienization of breeding rooms of animals, in particular pigs according to claim 1, involving a treatment of liquids containing suspended organic materials, such as slurry of pork, bovine or duck or effluents or methanation sludge, characterized in that it comprises: A first step of homogenizing and reducing the amount of suspended matter in the liquid to be treated, in particular by centrifugation; a second stage comprising the flocculation, coagulation and decantation operations, during which the liquid from the first stage is subjected to a prior dilution, addition of lime and addition of a solution of ferric ions, and at the end of which a pasty phase and a strongly basic liquid supernatant are collected; a third gaseous washing step of said supernatant during which the ammonia contained therein is exhausted to produce a strongly basic hygienized liquid, and in that at least a portion of said hygienized liquid is used strongly basic to get rid of animal droppings to hygienize the atmosphere of animal breeding rooms. 3. A method of hygienization according to claim 2, characterized in that the liquid subjected to the first step of decreasing the amount of suspended matter is homogenized beforehand. 4. A method of hygienization according to one of claims 1 to 3, characterized in that the dilution operation prior to the addition of lime is carried out with a portion of the highly basic liquid supernatant from the prior treatment of a liquid containing organic matter in suspension, obtained by carrying out the method according to one of claims 1 to 3. 5. Method according to one of claims 2 to 4, characterized in that the first step is performed by centrifugation to obtain a solids concentration of less than 3g / l. 6. Method according to one of claims 2 to 5, characterized in that, after the first step, the collected liquid is diluted so that it has a dry matter concentration of less than 1500 mg / 1. 7. Method according to one of claims 2 to 6, characterized in that during the first step, the liquid to be treated is added with a cationic water-soluble polymer, in particular a cationic polyacrylamide powder. 8. Method according to one of claims 1 to 4, characterized in that the flocculation, coagulation and decantation operations, in particular during said second step comprise three times: »a first time during which lime is incorporated with a slow stirring of between 80 and 150 revolutions per minute for a vessel having a diameter of less than 3 m, then a second time during which the solution of ferric ions, for example in the form of ferric chloride, is added under rapid stirring between 200 and 250 rpm for a vessel having a diameter of less than 3 m, and "A third time which consists of a decantation to collect, on the one hand a pasty phase and, on the other hand a supernatant. 9. Method according to one of claims 1 to 8, characterized in that the lime is added at a dose of 4 to 9 kg / m3 of liquid to be treated. 10. Method according to one of claims 1 to 9, characterized in that the lime is added in the form of quicklime comprising at least 85% of quicklime (CaO) or a milk of such lime. 11. Method according to one of claims 1 to 10, characterized in that the addition of ferric ions is carried out in the form of addition of ferric chloride at a dose of 400 to 800 ppm / m3 of liquid to be treated. 12. Method according to one of claims 1 to 11, characterized in that the highly basic hygienized liquid obtained has a pH of between 11.5 and 12.5. 13. Method according to one of claims 1 to 12, characterized in that the washing of the breeding rooms is carried out by hunting animal waste with the aid of said highly basic liquid in a plurality of gutters extending in parallel between them, preferably horizontally on the floor of the breeding rooms, and placed under caillebottis. 14. Method according to one of claims 1 to 13, characterized in that in post-weaning, it performs a hunting every two days to a daily hunting. 15. Method according to one of claims 1 to 13, characterized in that in the fattening phase, it carries out one to two hunts per day. 16. Method according to one of claims 9 to 15, characterized in that the flush is performed gutter after gutter, to adapt the volume of liquid to the amount of dirt contained in each gutter.