Process for manure treating

Field of technology

The invention relates to a process for treating a fertilizer, wherein a liquid fertilizer and / or waste water containing kjeldahlizadni-N is subjected to nitrification in a first step and denitrification in a subsequent step in an aerated reactor containing activated sludge rich in nitrified bacteria used in the nitrified stage. if necessary, neutralizing chemicals are added to the reactor and it also relates to a very fast denitrification reactor containing compact biomass, capable of converting nitrate to nitrogen gas and to which the organic substrate used in the denitrification stage is added.

Prior art

A process of this type is generally known from Agrarisch Dagblad, March 14, 1988. In this way, the liquid component of the fermented semi-liquid fertilizer is treated. Biodegradable organic substances, nitrification-capable nitrogen and phosphorus, which are contained in the liquid component of the semi-liquid fertilizer, can be removed. The process essentially subsides at the junction of the nitrified stage in a nitrified reactor in which the feed is converted by bacteria to oxidized nitrogen with a denitrified stage in a denitrified reactor where the oxidized nitrogen is converted by bacteria to nitrogen gas, the phosphate present in the liquid is reactor. Oxidation of the feed results in a reduction in the pH value, which in this process can be reduced by measuring in lime and / or by measuring in the effluent from the denitrification reactor (recirculating) to the nitrification reactor. During the nitrification step, this process also removes some of the nitrogen and phosphate contained in the new activated sludge cells. This nitrogen and phosphate are released during the fermentation of the fertilizer, by breaking down substances with a proportion of CO2 and CH4. In this method, the nitration reactor (which may be either an intermittent operation reactor or an intermittent flow reactor) is operated intermittently. It is aerated until all the ammonia has been nitrified, after which the aeration is stopped for a time so that the sludge can settle. The nitrified liquid fertilizer is discharged to the denitrification stage while the active sludge remains in the nitrification reactor for the next cycle. In the denitrification stage, the effluent from the nitrification reactor is pumped upwards through a flow bed reactor. This reactor has a very compact biomass that is able to convert nitrates to nitrogen gas. In order for this process to take place, an organic substance, such as methanol, must be added to the reactor. During the denitrification step, acid is consumed and therefore the pH value in the bacterial bed increases. As a result of this increase, an insoluble phosphate precipitate is formed with the calcium ions contained in the liquid. Fertilizer processing consisting of fertilizer fermentation and separation of fermented fertilizer, followed by a method of processing the liquid fraction of fermented semi-liquid fertilizer as described above , is shown in Fig. 1. (Reference numerals from this and other figures are explained in Tab.A) .

At present, a number of methods of fertilizer processing have been developed, such as Promesy from Helmod. In these methods, the semi-liquid fertilizer evaporates to a dry product, which requires considerable energy because the semi-liquid fertilizer contains more than 90% water. Furthermore, this evaporation is a complex technology that really still needs to be developed for fertilizer application. The cost of obtaining dry granular or powdered fertilizer by this method of processing is very high.

The concept differs from the method described above in the processing of semi-liquid fertilizer in conventional processing plants. It is also commonly used to process liquid fertilizer from calves. The conventional method has the significant disadvantage that it produces a large amount of sludge (with an excessive amount of bacteria) and that it is not possible to remove the phosphate. This means that special measures must be taken to treat the sludge and remove the phosphate. The usual processing of fertilizer also has high space requirements.

This process, described in Agrarisch Dagblatt of 17 March 1988, has the advantage of being relatively inexpensive and can be carried out on a thickener. However, even in this case, a number of processing problems arise.

Installations for the treatment of fertilizers by concentration and fermentation of fertilizers or quenchers-N containing waste water may be operated and carried out only if:

a) the dosing of the fermented liquid fraction is adapted to the nitrification capacity of the nitrification reactor. The nitrification reactor must not be overloaded, but also must not operate unloaded.

b) the metering of methanol (or other carbon source) into the denitrification reactor is adapted to the nitrogen load of the denitrification reactor. In case of underdosing, not all nitrates are removed; however, in the event of an overdose, methanol (or another carbon source) is present in the discharged material.

c) the effluent recirculating from the denitrification reactor to the nitrification reactor is controlled to be optimal. Low recirculation leads to a nitrate concentration that has an inhibitory effect on bacteria; Excessive recirculation results in the reactor being filled mainly with liquid that has already been treated.

These conditions can be met by using special equipment, while it is necessary to perform some different operations manually. The results of different measurements cannot be integrated and transferred to control activities without the intervention of at least one operator. The effluent from the nitrification reactor may still contain organic matter which cannot later be degraded in the nitrification reactor. The organic material which passes into the diitration reactor can be converted to inorganic material in this reactor by releasing ammoniacal nitrogen, which is then (because it is not fed in the recirculating stream) discharged with liquid waste.

The task of European application 90.202728.3 is to eliminate this problem. It relates to the above process, the essence of which consists in that the filling of the nitrification reactor is controlled and the optimal nitrification and denitrification is achieved on the basis of one or more of the following data:

- total nitrogen input load,

- information from the WAZU respiratory meter (Dutch Patent Application No. 8600396, filed February 17, 1986),

- pH in the nitrification reactor, the scale of which is between 6 and 8.5,

- amount of air required,

- delay,

- temperature in both nitrification and denitrification reactors, the scale being less than 40 °,

- concentration of oxidised nitrogen from the liquid waste for the denitrification reactor, the measure being a concentration value between 0 and 4 g N / l,

- the concentration of oxidised nitrogen in the nitrification reactor, the measure being the concentration of the sludge / liquid mixture between 0 and 4 g N / l,

- concentration of carbon source in liquid waste from denitrification reactor,

- gas production in a denitrification reactor.

An aspect of this method is the possibility of using an instrument, a respiration meter (WAZU respiration meter), which can determine the moments when the processing process is completed and which can calculate both the concentration of kjeldahlizing N in the liquid fraction of processed fermented fertilizer and nitrate concentration in liquid waste from nitrification. reactor (= feed for denitrification reactor). However, it should be noted that the use of such a respiratory meter is not necessary. The other data mentioned are sufficient for proper process control. Fluid flow and control lines relative to the respiratory meter are shown schematically in Fig.2. The respirator can control the entire method automatically based on the data collected and calculated by this device. However, as already mentioned, this respiratory meter is not necessary.

Nitrification is followed by a denitrification process.

Furthermore, the optimal conditions for the treatment methods were investigated in both the nitrification and denitrification reactors. Biomass generates heat in both the nitrification reactor and the denitrification reactor. Due to the high concentration of biomass and the high conversion rates that take place in both reactors, there will be excess heat in both reactors if no meters are used. - Laboratory studies have shown that the optimal temperature for a nitrifying bacterial population is between 31 and 35 ° C and that the maximum temperature that can be tolerated is 40 °. Based on general scientific information, it can be expected that the same temperature limits can be applied to denitrifying bacterial populations. Thermophilic denitrifying bacteria are known. They operate at temperatures above about 50 ° C. However, for various reasons, it is not desirable to use thermophilic organisms in a denitrification reactor: the liquid waste to be discharged would be too hot and the recirculation stream must not be too hot. Both nitrification and denitrification reactors can only operate if they are provided with some means by which heat is removed from their contents.

In the present process, in a denitrification reactor, in order for the phosphate removal efficiency to maintain such conditions to be able to precipitate, the phosphate must depend on the pH and the ratio.

HCOa / CO2 in a denitrification reactor.

The desired pH can be obtained in the present process by using an organic carbon source for a denitrification reactor with a specific ratio of chemical oxygen demand (COC) to total organic carbon (TOC). The fact is that in a denitric reactor, alkalinity (bases, acid carbohydrates and carbohydrates) is produced due to the denitric acid reaction. The production of alkalinity depends on the COC / TOC ratio of organic source C in the denitrification reaction. Usually methanol is used as the source of organic C. Methanol has a high COC / TOC ratio and results in higher alkalinity production than, for example, glucose, which has a lower COC / TOC ratio. Research has shown that the COC / TOC ratio must be 3.75 or less.

As mentioned, the pH in the nitrification reactor depends on the oxidation of the effluent. In order to separate the acidification, the alkalinity can be measured or the liquid waste from the denitrification reactor can be recirculated to the nitrification reactor. It was found experimentally that the concentration of oxidized nitrogen in the nitrification reactor in the sludge / liquid mixture is between 0 and 1.5 g N / l. Furthermore, it has been found that the concentration of oxidized nitrogen in the liquid waste of the denitrification reactor is between 0 and 4 gN / l and preferably between 1.00 and 1.4 g N / l. To achieve this, the liquid waste from the denitrification reactor can be recycled. This recirculation causes the concentration of oxidized nitrogen at the inlet to the reactor to dilute. Furthermore, this recirculation achieves a higher flow rate in the denitrification reactor, which improves the contact between the biomass and the substrate in the reactor. Recirculation can be performed directly from the liquid waste to the stream entering the denitrification reactor. However, it is also possible (and indeed more advantageous for the whole process) to use liquid waste from the denitrification reactor for recirculation, this recirculation being carried out either completely or partially by means of a nitride reactor. The aim of this is to achieve both savings in the consumption of chemicals for pH control in the nitricade process and dilution of the contents of the nitricade reactor by 4 g N / l.

Another, so that the content of oxidized nitrogen is always lower than the aspect, is the use of separation, ie physical / chemical flocculation and flocculation separator or membrane technology after nitrification. The purpose of the reactor is to capture organic matter.

Separations carried out before denitrification are suspended and colloidally dissolved which would lead to it in the denitrification reactor and consequently ammoniacal nitrogen. The physical / chemical operation of the separation is shown in Fig.3. Residual organic is removed from the liquid waste and can be removed beforehand by separating the denitrification stage of the denitrification stage.

Mineralizing would be formed plus the flocculating agents can be used using flocculating agents from liquid waste. By placing it upstream, the organic matter is converted to inorganic matter and ammonia nitrogen is formed. Another advantage is that the carbonate content in the liquid waste from the nitrification reactor is low (lower than in the liquid waste from the denitrification reactor to which the organic substance is added). This is an advantage when using a flocculating agent which forms a precipitate with the carbonate. If a flocculating agent containing cations that precipitate with the sulfates is used, further removal of the sulfates occurs.

The parallel application also relates to a device for carrying out the method described above, and its essence consists in that it consists of:

- a nitrification reactor equipped with aeration, inlet of the liquid to be treated, inlet of chemicals for acid neutralization, active sludge, rich in nitrifying bacteria, sludge outlet, liquid waste outlet,

- piping through which liquid waste from the reactor can be fed to the denitrification reactor,

- a denitrification reactor equipped with a liquid waste feed from the nitrification reactor, a carbon source feed, an upstream floating bed column (USB), a very compact biomass capable of converting nitrate to nitrogen gas, a phosphate-rich sludge outlet, a liquid waste outlet, liquid waste from a denitrification reactor.

Example of an embodiment of the invention

In its simplest form, the plant (shown schematically in FIG. 2) consists of a combination of a batch reactor (into which the feed liquid 7 is fed once per cycle) or a batch reactor (batch feed) (into which the feed liquid is fed gradually or stepwise). per cycle) as a nitrification reactor 2 and a continuously fed upflow reactor (USB) as a denitrification reactor 12. · Both reactors operate connected in series, without bypass of nitrification reactor 2, but independently with back-mixing 33 from denitrification reactor 13 to nitrification reactor 2 ·

The use of a respiratory meter WAZU 18 (Dutch patent application ~ 86.00396, filed February 6, 1986), a measuring and control unit, which monitors the respiratory rate of biomass in reactor 2 is the essence of the device according to the co-pending application.

The nitrification reactor 2 of the plant is provided with aeration 10, a feed liquid inlet 7, a sludge outlet 11, a liquid waste outlet and a non-binding liquid waste inlet from the denitration reactor 33, all controlled by a WAZU respirator (Dutch patent application 86.00396, filed February 6, 1986). . This respiration meter also measures the nitrogen source 14 for the denitrification reactor 12. This denitrification reactor 13 is further provided with a nitrogen gas outlet 17 and a recirculation 33 of liquid waste or an outlet 16 (see Figures 2 and 5).

Another embodiment of the device according to the co-pending application (shown schematically in Fig. 4) is also provided with a line 32 through which liquid waste from the nitriitrification reactor 13 can be partially recirculated to liquid waste 12 from the nitriation reactor 2. and further provided this embodiment is provided with an inlet 8. of one or more acid neutralizing chemicals to the nitrification reactor.

and.

Furthermore, the device may consist of a combination of the two embodiments described above (Figs. 4 and 5), i.e. the embodiment of Fig. 6, which is provided with a pipe through which the liquid waste 16 from the denitrification reactor can be ± 3. partially recirculated (lines 32 and 33, respectively) to the nitration reactor 2 and which serves as the feed liquid for the denitrification reactor 13.

The last three embodiments described above, shown in Figures 4, 5 and 6, may include additional accessories (see Figure 7) in the form of a supply of 20 chemicals for phosphorus precipitation.

Furthermore, all these embodiments (from Figs. 4, 5, 6 and 7) can be provided with one or more separation or flocculation devices 19. The flocculation device as such is shown in Fig. 3.

The device according to the co-pending application, which has already been described, can be provided with a flocculation device in different places (Figs. 8, 9 and 10). In the embodiment of Fig. 8, the flocculation device is positioned so that the liquid waste 16 from the denitrification reactor 13 flows through the flocculation device 19 (Fig. 3) upstream of the recycle 34, 35 or outlet 22.

In the embodiment according to Fig. 9, the flocculation device 19 is positioned so that only the liquid waste 16 from the denitrification reactor 13 to be discharged flows through the flocculation device 19.

In the preferred embodiment of Fig. 10, the flocculation device 19 is positioned so that the liquid waste generated in the nitrification reactor 2 flows through the flocculation device 12 before entering the denitrification reactor 13.

The apparatus according to the co-pending application, in which the nitrification reactor 6 is provided with a liquid waste supply 23 or 34 from the denitrification reactor 13, may be provided with a shower device 25 by which the liquid waste can be sprayed into the nitrification reactor 9 to prevent foaming.

Furthermore, all embodiments according to the parallel application can be provided with buffer tanks 23 (Fig. 10).

In the above process, all the liquid waste passes through the separator 19, which means a high load on the separator 12 ·

It has now been found that an improvement can be achieved by partially recirculating the liquid waste 12 from the nitrification reactor 2 to the recirculation of the denitrification reactor 12, adding a carbon source to the liquid waste to flow to the recirculation of the denitrification reactor 13 and discharging part of the liquid waste stream. 12 from the nitrification reactor 2 to the sludge separation unit 12, the liquid waste 36 from the separation unit 19 is fed to another denitrification reactor 37. This additional denitrification reactor 37 will be referred to as the discharge denitrification reactor 37. If necessary, a carbon source can be added to the denitrification reactor 37. The liquid waste from the denitrification reactor 37 of the discharge line can be discharged to the waste.

Surprisingly, it has been found that the sludge present in the liquid effluent 12 recycled to the recirculation of the denitrification reactor 12 and later recirculated to the nitrification reactor 2 has no adverse effect on the process.

The above process can be improved by using two different types of denitrification reactors, a discharge line denitrification reactor 37 and a recirculation denitrification reactor 13. The liquid waste 22 from the nitration reactor 2 is partially recirculated from the nitrification reactor to the recirculation denitrification reactor 12. An organic carbon source can be added to the liquid waste of this denitrification reactor 12 to form a sufficient organic substrate for the denitrification reaction in this reactor 13.

For the arrangement of the device according to the invention, it is no longer decisive whether the liquid waste from the recirculating denitrification reactor 13 still contains a small amount of nitrates. This is because the liquid effluent 33 from this reactor 13 passes into the nitrate reactor 2. The measurement of the organic carbon source in this denitric reactor 13 is less critical than in the process of the co-pending application. Another part of the liquid waste 1.2 is fed to the denitries of the discharge reactor 37 of the discharge line.

The organic carbon source may also be added to the liquid effluent of the denitrification reactor 37 of the discharge line. However, it is not recommended to use part of the liquid waste for the treatment process according to the invention as a source of organic carbon, because the liquid waste 22 from this denitrification reactor 37 of the discharge line is to be discharged while still containing kjeldahlizadni nitrogen which must be removed. This embodiment, using a part of the liquid waste from the system, can only be used in the recirculating denitrification reactor 13. The block diagram is shown in Fig.12. As explained above, it can be used for the removal of phosphates and suspended and colloidally dissolved organic substances of the invention with recirculating separation. In this process, according to the denitrification reactor 13 and the denitrification reactor 37 of the discharge line, the separation stage 19 can be placed before the denitrification reactor 37 of the discharge line and behind the liquid waste 12 from the nitrification reactor 2 into the inlet stream 22. The hydraulic load of the separation stage 19 is much lower. than in the concurrent application. This is shown in Fig. 13. However, if the separation stage 19 is placed downstream of the denitrification reactor 37 of the discharge line, some ammonia and biodegradable soluble organics are still formed from the organic material in the recirculation denitrification reactor 13. it is discharged to waste.

By placing the separation stage 19 upstream of the denitrification reactor 37 of the discharge line, the organic substances are removed before passing through the reactor 37. so that no ammonium or soluble organic substances are formed there. This is shown in Fig.14.

The use of two different types of denitrification reactor also makes it possible to add liquid to the liquid effluent of the recirculation denitrification reactor 13, ie between the point where the liquid effluent stream 12 from its triitrification reactor 3 is divided into stream 13 and 39 and the stream to the recirculation denitrification reactor. reactor 13. In such an arrangement, an organic material can be used which is fed as a carbon source for the denitrification process, thus eliminating the need for a separate carbon source 14 prior to the recirculation denitrification reactor 13. Ammonium in the feed passes unchanged through the recirculation denitrification reactor 13 and will be added by recirculation stream 33 to the nitriles. Reactor reactor 3. Here, ammonium will be oxidized to nitrate. Most of the oxidizable organic substances in the feed stream will be used for denitrification. If any oxidizable organic substance still remains in the liquid waste stream 33 from the recirculation denitrification reactor 13, this substance will be oxidized in the nitrification reactor 9.

The liquid effluent 12 from the nitrification reactor 3 will be partially passed through a recirculation denitrification reactor 13. To this part of the liquid effluent 13 (intended for the recirculation denitrification reactor 13) a supply of organic matter and ammonium will be connected, so that the nitrates contained in this part of the liquid 12 from the nitrification reactor. 3 will be denitrified here. The rest of the liquid waste 12 from the nitrification reactor 3 passes through a separation stage 13 / if necessary from the point of view of the pollution requirement. The carbon source is added to the liquid waste 36 from the separation stage (e.g. methanol). This stream is then passed through a denitrification reactor 37 of the discharge line, where the nitrates are converted to nitrogen. The liquid waste 38 from this reactor is then discharged to the waste. This is shown in Fig. 15.

By connecting the recirculating liquid supply to the inlet to the recirculation reactor 13, the recirculation ratio (= amount fed to the recirculation denitrification reactor 13 without recirculation liquid divided by the amount of recirculation liquid) is determined by several points:

- the nitrate concentration in nitrification reactor 3 should be less than 1.5 g N / l,

- the alkalinity value in the liquid waste 33 from the recirculation denitrification reactor 13 should be sufficient to counteract the acidification in the nitrification reactor 9.

- the use of an external carbon source (eg methanol) is reduced,

- the hydraulic load of the nitrification reactor 2 and the recirculation denitrification reactor 13 should not be too great.

To meet these requirements, it may be necessary to add a portion of the recirculating liquid to the nitrification reactor 2 and a second portion to the feed to the recirculation denotriation reactor 13. In this case, it may also be necessary to add an external carbon source 14 such as methanol to the recirculation denitrification reactor 13. (shown schematically in Fig. 16). This process can be performed with or without a separation step.

Furthermore, this method can be performed with one or more buffer tanks. The buffer tank 23, in which the liquid waste from the nitrification reactor 2 is collected, can be formed as a settling tank, so that the excess sludge from the nitrification reactor 2 can settle there and can be removed. The liquid sludge from this buffer tank is passed partly to the recirculation denitrification reactor 13 and partly to the separation stage 19.

The liquid waste 33 from the recirculation denitrification reactor 12 can be collected in a buffer tank 23. This buffer tank can also be formed as a settling tank, so that the sludge still contained in the liquid waste 33 from the recirculation denitrification reactor 13 can settle there. This sludge 41 can be returned to the reactor or can be discharged as excess sludge. The liquid effluent from this buffer tank is fed to the nitrification reactor.

The liquid waste 33 from the outlet line of the denitrification reactor 13 can also be collected in a settling tank. The sludge still contained in the liquid waste 33 from the denitrification reactor outlet line may settle here and may be returned to the denitrification reactor 41 or may be discharged as excess sludge 42. The waste from this settling tank is discharged. This is schematically illustrated in FIG.

It will be appreciated that this different arrangement of the device may be used in all of the above embodiments.

According to a preferred embodiment, part of the liquid waste can be used as a carbon source.

According to the present invention, the separation unit 19 may use conventional separation methods such as centrifugation, settling and the like. , but the use of membrane technology is also possible. In this case, filtration is performed, followed by removal of the phosphates by precipitation.

Another way to remove organic material is by chemical oxidation using ozone or hydrogen peroxide.

The following example is for illustrative purposes only and does not limit the scope of the invention.

Example

The fermented fertilizer (ie the liquid fraction obtained by centrifugation of anaerobically fermented pig manure) is treated with the device of Fig.11.

The analysis of the fermented fertilizer shows a COD (chemical oxygen demand) concentration of 21000 mg / l, a nitrogen concentration of 6500 mg N / l in the useful reactors 13, and when all the ammonia is over and the activated sludge has a concentration of 275 mg P / l.

The device of FIG. 11 consists of a nitrification reactor 9 with a volume of 50 m³, two recirculating denitrifiers which are placed in parallel with each other and each has a sludge bed volume of 10 m³. a separator 19 comprising at least a tubular inoculator and a centrifuge and a denitrification reactor of the discharge line, having a useful sludge bed volume of 5 m³.

The nitrification reactor in this example is a batch reactor with gradual inlet (0.5 m³ for one step) of fermented fertilizer. Total amount 2 m³ is admitted in four steps.

8 m are fed in the entire cycle of the nitrification reactor³ of liquid waste 33 from the denitrification reactor by means of showers evenly distributed over time. After admitting the whole 2 m³ of the fermented fertilizer into the nitrification reactor, nitrogen is nitrified, aeration is allowed to settle for 60 minutes. After settling time, 10 m³ sludge water is discharged as liquid waste 12 from the nitrification reactor. Then another cycle begins when 2 m is fed again³ fermented fertilizer and 8 m³ liquid waste from denitrification.

The WAZU respirator (trademark RA-1000 designated Manotherm) is connected to a nitrification reactor to control the actual respiration rate. Furthermore, the oxygen concentration is controlled by an oxygen sensor.

The blower that is used to supply oxygen through the air is controlled by the oxygen concentration in the nitrification reactor. The oxygen concentration is maintained at 2.0 mg / l.

After adding 0.5 m³ of the fermented fertilizer, the actual respiration rate is increased and the blowing rate is also increased to maintain the oxygen concentration at 2.00 mg / l. When the ammonium supplied with the fermented fertilizer is nitrified, the actual respiration rate drops to a baseline value and the blowing rate also decreases. After falling below the set value of the respiratory rate and / or the set value of the blowing rate, another 0.5 m³ the fermented fertilizer is fed to a nitrification reactor. Fig. 18 shows the oxygen concentration

The average reactor charge was at

Lime milk and blowing speed as a function of time. fermented fertilizer in this nitrification test about 6 m³ per day.

The pH is also measured in the nitrification, provided that the pH drops below 6.5. The temperature is controlled and kept below 33 ° C by means of a heat exchanger.

The liquid waste 12 from the nitrification reactor £ has a nitrate concentration N of 1100 mg N / l and a phosphate concentration P of 125 mg Ρ / l. The nitrate N concentration is lower than would be expected based on the dilution of the reactor contents with liquid waste from the denitrification reactor. This is due to some denitrification in the nitrification reactor during the settling time and the nitrogen contained in the biomass.

The liquid waste 12 from the nitrification reactor is collected in a buffer tank 23. This tank is designed as a settling tank, so that the sludge still contained in the liquid waste 12 from the nitrification reactor can settle there.

Four-fifths of the contents of the buffer tank are passed through recirculation denitrification reactors 13, which are arranged in parallel. Methanol is added based on the concentration of nitrates N in the liquid waste stream from the recirculation denitrification reactors 13. The methanol dose is about 1.65 kg / m³ liquid waste from the reactor. The denitrification process is controlled on gas (1630 1 / h). The pH of recirculating denitrification reactors is between 9.0 and 9.3. The temperature is kept below 35 ° C by means of a heat exchanger.

The liquid waste 33 from these two denitrification reactors is collected in a buffer tank 23. 2 of this buffer tank, the liquid contents are pumped into showers located at the top of the nitrification reactor or in the nitrification reactor.

One fifth of the liquid waste 12 from the nitrification reactor 2 ^se denitrification base production is used as input stream 39 and is pumped by a separation system consisting of at least a tubular allocator. At the beginning of this inoculator, 38% by weight is dosed. FeCl3 solution (iron (III) chloride) in an amount of 10 l / m³ liquid waste from the nitrification reactor 2- Lime milk or sodium hydroxide is fed in the middle of the tubular inoculator until the pH value is

5.5. At the end of the tubular inoculator, the polyelectrolyte (180 mg per m 2) is metered in³liquid waste from nitrification reactor 2) ·

The liquid then passes through a centrifuge and is divided into a liquid stream 35 and a sludge stream 29. Production «

The concentration of nitrates N and the concentration from the centrifuged amount is up to 11ΟΟ mg N / l and 0.5 mg P / l, respectively.

The liquid waste 3A from the separation stage 19 is then passed through a denitrification reactor 37 of the discharge line. Methanol is added based on the concentration of N nitrates in the liquid waste stream. The denitrification process is controlled by gas production (408 1 / h). The pH is below 9.0. The temperature is kept below 35 ° C by means of a heat exchanger.

The liquid waste 38 denitrification 37 is passed through a settling tank and discharged.

sludge is about 0.36 m³/ d. of phosphates P in waste