DE3402688A1 - Biological effluent treatment process having a nitrification zone - Google Patents

Description

GLAWE, DELFS, MOLL & PARTNER _: ':'":":: PATENTANWÄLTE

EUROPEAN PATENT TORNEYS

RICHARD GLAWE KLAUS DELFS DR-ING. DIPING. OIL QUANTITY WALTER MOLL DIPL-CHEM. DR. RER. NAT. DIPL-PHYS. DR. RER. NAT. HEINRICH NIEBUHR OFF. BEST. INTERPRETER DIPL-PHYS. DR. PHIL HABIL.

Passavant-Werke AG & Co. KG
Aarbergen 7

8000 MUNICH 26 2000 HAMBURG 13

PO Box 162 PO Box 2570

. LIEBHERRSTR. 20 ROTHENBAUM-

Bioloaisches Abwasserreiniaunas- ^{TEL (089) 226548} chausseess

Bioxuyiscries ADWdb & erhiniyungb telex6225osspez tel <O40) 4io2oo8

procedure with nitrification zone telecopier (089) 223938 telex21292ispez

MUNICH
A 05 / £> / G 1239

description

The invention relates to a biological wastewater treatment process with at least one nitrification zone, in which the wastewater with nibrifying microorganisms containing return sludge with supply of oxygen to Reaction is brought about to nitrogen compounds contained in the sewage to be converted into nitrate, with the sludge in a zone downstream of the nitrification zone separated and at least partially returned as return sludge to the nitrification zone.

10. In biological wastewater treatment, the conversion of organic carbon compounds into separable ones plays a role Solids (BOD breakdown) more and more the removal of nitrogen compounds also play a role. These

BANK: DRESDNER BANK, HAMBURG, 4030448 (BU 20080000) ■ POST CHECK: HAMBURG 147607-200 (BU 20010020) TELEGRAM: SPECHTZIES

is possible by means of two processes, called nitrification and denitrification, which take place under different conditions and with the participation of different types of bacteria. In nitrification, nitrifying bacteria convert ammonium ions into nitrite and then into nitrate under aerobic conditions. The nitrates formed in this way are decomposed by other bacterial species under anaerobic conditions through denitrification, whereby elemental nitrogen and possibly N ₂ O are formed, which escape as gaseous products that are only sparingly soluble in water.

With the full waste water purification process, the processes of BOD degradation, nitrification and denitrification in separate, from the wastewater one after the other flowed through stages each with its own return sludge circuit let it run off (so-called three-sludge process). Compliance with different, the respective process optimal adapted conditions in the individual stages with regard to the nature of the return sludge, oxygen concentration, Stress and length of stay is so special simply possible. But it is also possible to have BOD degradation and nitrification together or at least together Let the return sludge cycle run off

(Two-sludge process) or even a single return sludge circuit to be provided for BOD degradation, nitrification and immediately subsequent denitrification (single sludge process) (See Pöpel "Textbook for wastewater technology and Water protection "). It is also possible to precede the denitrification of the nitrification, which is then advantageous, for example is when the wastewater already carries higher levels of nitrates. Of the one leaving the nitrification In the other case, however, a considerable part of the wastewater must be returned to the upstream circuit Denitrification zone are returned to at least part of the nitrates formed during the nitrification to eliminate. The invention can in principle be used in all of these process variants familiar to the person skilled in the art.

There is a major problem with nitrification in that the nitrifying bacteria grow very slowly, so that the sludge only after a considerable time, which is at least 3 days, preferably and especially at low temperatures but also significantly more, reaches its optimal activity for the reaction with the nitrogen compounds of the wastewater. It must therefore for a sufficiently high sludge age for the nitrification zone can be ensured. This requires a very large pelvic

volume and / or a very high sludge concentration in the nitrification zone. It is also beneficial for nitrification if the sludge load, ie the ratio of the contaminants added with the wastewater (BOD) to the dry sludge substance, is kept as low as possible. This also speaks for a high sludge concentration in the nitrification zone. According to general doctrinal opinion and applicable dimensioning guidelines for sewage treatment plants, the volume load in the nitrification zone should be a maximum of 0.5 kg BODc / m ³ · d, the sludge _{load a maximum of 0.15 kg BOD 5} / kg dry sludge substance / d and the sludge age at least 9 days.

However, maintaining a correspondingly high sludge concentration in the nitrification zone leads to the difficulty that a proper separation of such a concentrated suspension does not occur in a subsequent final clarification stage is possible. One is therefore forced to dilute the suspension in the nitrification zone to such an extent that a secondary clarification is possible remains possible through sedimentation. The basin volume of the nitrification zone can therefore not be used optimally will.

The object of the invention is to reduce the effectiveness of the nitrification in a method of the type mentioned Sludge concentration in the nitrification zone

3402683

to improve.

According to the invention, this object is achieved in that the return sludge is fed to the nitrification zone before it is fed in an aging zone separate from the nitrification zone while one for the growth of the nitrifying ones Microorganisms are retained for sufficient time,

The invention thus provides for an aging of the return sludge separate from the nitrification zone, whereby it is achieved that the return sludge enters the nitrification zone with optimal nitrification activity μηα can develop an optimal and complete reaction interaction with the nitrogen compounds of the wastewater even at low sludge concentrations. Contrary to previous opinion, perfect nitrification is also possible if the volume load is significantly higher than 0.5 kg BOD / m ³ / d, e.g. up to 1.0 kg / m ³ / d and / or the sludge load is significantly higher than 0.15 kg BOD ₅ / kg sludge dry matter / d, e.g. up to 0.3 kg / kg / d. The volume of the nitrification zone can thus be reduced or a given volume can be better utilized. In the separate aging zone, the sludge can be kept at an extremely high concentration, preferably more than 5 kg / m ³ and up to

Can be 20 kg / m ^3. Only a relatively small additional volume is therefore required for the aging zone.

The residence time of the return sludge in the aging zone is preferably a multiple of its residence time in the nitrification zone and can at least three days, preferably at least seven days. Oxygen is preferably supplied in the aging zone essentially only to the extent that it is necessary to maintain basic breathing.

The invention also relates to a waste water purification system for carrying out the aforementioned method, which is characterized by an aging basin connected in the path of the return sludge, through which the wastewater does not flow .

Embodiments of the invention are explained in more detail with reference to the drawings:

1 shows the flow diagram of an embodiment of the process according to the three-sludge system;

Fig. 2 shows the flow diagram of an embodiment according to the single slurry system.

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According to FIG. 1, the wastewater flowing in at 1 first enters an aeration basin BB, in which it is normally used Wise brought into contact with activated sludge and also supplied with oxygen, so that in the activated sludge contained microorganisms break down the BOD, i.e. oxidize the organic carbon compounds, so that on the one hand Gaseous CO and, on the other hand, sedimentable solids arise. In a first post-clear stage 1NK the sludge is separated and used as return sludge to the Aeration basin BB returned. Then the wastewater arrives in a nitrification basin NB, where it is below Oxygen supply brought into contact with return sludge and the process conditions, including the sludge age, are adjusted to match those in the sludge contained nitrifying bacteria convert the existing nitrogen compounds into nitrate. The one for this Any sludge required is separated off in a second secondary clarification zone 2NK downstream of the nitrification tank NB and pumped back in the circuit to the nitrification basin NB, with an aging basin AB interposed is in which the sludge is retained until the required sludge age is reached. The dwell time of the sludge is preferably in

Aging pool AB approx. Nine days with a correspondingly high Schlairank concentration of more than 5, preferably more than 7 kg / m ³ .

From the second secondary clarification zone 2NK, the wastewater reaches the denitrification basin DNB, where the previously formed nitrates are decomposed under strictly anaerobic conditions, whereby the nitrogen can escape _{in the form of gaseous N 2} or N _{2 O.} In a third secondary clarification zone 3NK, the resulting sludge is separated by sedimentation and the treated wastewater is drawn off at 2, while part of the sludge is returned to the denitrification tank DNB and the rest is drawn off as excess sludge at 3, which is also carried out in the two upstream stages.

The embodiment according to FIG. 2 is a single sludge system with upstream denitrification. The one flowing in at 1 Wastewater first reaches a denitrification zone DN, in which under anaerobic conditions in contact with activated sludge the biological decomposition of the nitrates present he follows. The wastewater together with the sludge then reaches the activation zone BB, where the BOD degradation, i.e. the oxidation of the organic carbon compounds takes place. Eventually the wastewater gets in the nitrification zone N, where also under aerobic conditions

in contact with a sludge of sufficient Mud age the conversion of the still existing nitrogen compounds takes place in nitrate. All of the sludge is disposed of in the downstream secondary clarification zone NK separated and returned as return sludge to the denitrification zone DN, partly as excess sludge deducted at 3. Since the clarified wastewater withdrawn from the secondary clarification zone NK would still contain the nitrates formed in the nitrification zone N, a considerable amount must be Part of it is returned from the nitrification zone N via the circuit 4 to the denitrification zone DN will.

The one returned in the denitrification zone DN Sludge is in an aging basin AB during a sufficient aging time of preferably several Days so he was then in the nitrification zone N, an optimal activity for nitrification even at a relatively low sludge concentration can unfold.

It is also possible to modify the embodiment according to FIG. In such a way that the entire return sludge is only returned to the nitrification zone N and an aging basin AB ^{1 is connected} upstream of it, as shown in dashed lines in FIG.

9 -

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indicated / with then in the denitrification zone DN leading return sludge line with the aging basin AB can be omitted.

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Claims (6)

GLAWE1DELFS1MOLLStPARTNER--:::: PATENTANWÄLTE EUROPEANPATENTATTORNEYS 3ΑΠ2688 RICHARD GLAWE KLAUS DELFS DR-ING. DIPLHNG. ULRICH MENGDEHL WALTER MOLL DIPU-CHEM. DR. RER. NAT. DIPL-PHYS. DR RER. NAT. HEINRICH NIEBUHR ÖFF. BEST. INTERPRETER DIPL-PHYS. DR. PHIL HABIL. Passavant-Werke AG & Co. KG Aarbergen 7 8000 MÜNCHEN 26 2000 HAMBURG 13 Biological wastewater treatment SE ££ E »ESST1 process with Ni tr if i- tel. <089> 226548 chausseesb TELEX 522505SPEZ TEL (040) 4102008 TELECOPIER (089) 223938 TELEX212921SPEZ MÜNCHEN A 15 / P 1239 claims 1. Wastewater treatment process with at least one Nitrification zone in which the waste water with return sludge containing nitrifying microorganisms is below Oxygen supply is reacted in order to convert nitrogen compounds contained in the wastewater into nitrate, wherein in a zone downstream of the nitrification zones, the sludge is separated and at least partly returned as return sludge to the nitrification zone is, characterized in that the separated return sludge prior to its supply to the nitrification zone in an aging zone that is separate from the nitrification zone during one for the growth of the nitrifying microorganisms back enough time BANK: DRESDNER BANK. HAMBURG. 4030448 (BLZ 20080000) POST CHECK: HAMBURG 147607-200 (BLZ 20010020) TELEGRAM: SPECHTZIES 2. The method according to claim 1, characterized in that the volume of the aging zone for the production of an entire sludge age of min-r at least 4 days, preferably at least 7 days. 3. The method according to any one of claims 1 and 2, characterized - that in the aging zone a higher sludge concentration than in the nitrification zone is adhered to. 4. The method according to claim 3, characterized in that the sludge concentration in the aging zone is at least 5 kg / m ³ . 5. The method according to any one of claims 1 to 4, characterized characterized in that in the aging zone essentially only one for the maintenance of the Basic breathing required oxygen supply to the sludge takes place. 6. wastewater treatment plant for performing the method according to any one of claims 1 to 5, with one of Nitrification basin or nitrification reactor flowing through wastewater, a final clarification stage and a return sludge line from the secondary clarification stage to the nitrification basin or reactor, characterized in that that in the return sludge line to the manufacture a total mud age of at least three, preferably at least seven days is designed.