JPS60206498A - Treatment of excretion sewage - Google Patents

Abstract

PURPOSE:To efficiently perform biological nitration and denitrification at a low dilution ratio and high load, by adding a floculant to excretion sewage to separate a separated solution with a BOD/N ratio of 2.5-3.5 and applying biological nitration and denitrification treatment to said separated solution. CONSTITUTION:Excretion sewage is introduced into a reaction tank 1 and an inorg. flocculant and/or a cationic org. flocculant 8 are injected into said reaction tank 1 while a pH control agent 9 is injected thereinto if necessary to perform flocculation reaction under stirring. Next, a nonionic or anionic org. synthesis agent 10 is injected in a second reaction tank 2 if necessary to grow floc under stirring and the solid-liquid separation is performed by a solid-liquid separation means 3 such as a concentrator. Separated sludge 11 is discharged from the solid-liquid separation means 3 and the separated solution 12 is introduced into a denitrification tank 4 along with return sludge 13 and a return nitrated solution 14 and mixed with activated sludge containing denitriding bacteria in the tank while the resulting mixture is gently stirred in an oxygen blocked state to perform denitrification treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention relates to a method for treating human waste wastewater by coagulation treatment and nitrification-denitrification treatment.

[Prior art]

Biological treatment is the mainstream in human waste treatment, and nitrification and denitrification treatment is performed as a part of this, but there are problems such as lack of dilution water, land chicks,
Due to stricter discharge regulations, low dilution, high load, and advanced treatment are required. However, when nitrification and denitrification are carried out biologically at low dilution and high load, foaming and heat generation occur in the nitrification tank, and in order to prevent this and ensure normal nitrification and denitrification, defoaming is required. This method requires the addition of agents and a large-scale defoaming and cooling device, which complicates the maintenance and management of the device, and raises the COD of the treated water, making it impossible to perform stable treatment.

In order to solve these problems, a method has been proposed in which human waste is flocculated in an acidic region, and then the separated liquid is biologically nitrified and denitrified (Japanese Patent Application No. 336562).

However, according to this method, biological nitrification and denitrification of the separated liquid can be carried out at low dilution and high load without foaming or heat generation, but in order to stably maintain a high nitrogen removal rate, dissolved There was a problem in that oxygen and pH had to be maintained at appropriate values.

[Purpose of the invention]

This invention is intended to obtain a stable nitrogen removal rate in normal biological nitrification and denitrification, by coagulating and separating human waste wastewater so that the BOD/N ratio of the separated liquid falls within a predetermined range.
A method for treating night soil wastewater that can efficiently perform biological nitrification and denitrification with low dilution and high load by subjecting the separated liquid to biological nitrification and denitrification treatment, thereby increasing the COD removal rate and nitrogen removal rate. The purpose is to propose.

[Structure of the invention]

This invention involves adding a coagulant to human waste wastewater to perform coagulation separation, separating a separated liquid with a BOD/N ratio of 2.5 to 3.5, and subjecting this separated liquid to biological nitrification and denitrification treatment. This is a method for treating human waste wastewater.

In this invention, human waste-based wastewater refers to waste water that contains human waste, such as collected human waste, its removal, and mixtures thereof with other wastewater such as excess sludge.

The total nitrogen content of collected human waste is 3,000-5,000 m (5 IQ), most of which is ammonia and raw nitrogen.

The reason for the decrease in the nitrogen removal rate was investigated by separating such human waste in an acidic manner (as in the conventional method) and applying biological nitrification and denitrification treatment to the separated liquid. However,
It was found that this was because the BOD/Ni of the separated liquid obtained by coagulation separation was low.

That is, when coagulation separation is carried out in an acidic region, the SS properties and polymeric BOD of human waste "1-1" are removed, the BOD becomes low, and the BOD/N ratio becomes about 1.6.

Generally, the BOD/N ratio in the nitrification and denitrification treatment of night soil is about 3 for the nitric acid type and 1.8 for the nitrous acid type.

Since the separated liquid is mainly composed of soluble BOD, which is a low-molecular substance that is easily used by denitrifying bacteria, nitrification and denitrification can be carried out (although it is possible to do so, it is necessary to maintain the denitrification conditions in the nitrite type). :can be,
If the amount of aeration in the nitrification tank increases and the nitrogen becomes nitric acid, the nitrogen removal rate will decrease.

Therefore, in the present invention, instead of removing all SS properties and polymeric BOD in human waste wastewater by coagulation separation, SS in wastewater is added to the separated liquid side in an amount of approximately 1000 to 10000 mg/Q.
The BOD/N ratio of the separated liquid is 2.
Coagulation separation is performed so that the ratio is 5 to 3.5. In order to perform coagulation separation under such conditions, the addition rate of the flocculant used for coagulation separation is lower than the addition rate required for complete dehydration.

Generally, in the case of sludge dewatering treatment, there is an optimum addition rate of flocculant required for dewatering, and if the addition rate is lower than this, the SS recovery rate will be low and the dewatering performance will also deteriorate, making mechanical dewatering impossible. In the case of human waste wastewater, the SS content is 30-50%
Since it is fibrous, it was found that solid-liquid separation can be easily performed even with insufficient coagulation. The present invention takes advantage of this property, and due to insufficient coagulation, B in the separated liquid is
The sludge is coagulated so as to leak part of the OD, and the separated liquid is subjected to biological nitrification and denitrification treatment, and a flocculant is further added to the sludge for complete dewatering treatment.

The flocculant used in the flocculation treatment may be either a pyrolyzate coagulant or an organic flocculant, or both may be used in combination. Preferably, a cationic organic flocculant is used, and SS and BOD components can be effectively removed by adding a small amount. Rootless flocculants include aluminum chloride, polychlorinated aluminum 11, aluminum sulfate, iron chloride (n)
, iron (II) sulfate, iron chloride (m), iron sulfate (■), Kotsubarasu chloride, poly'45M iron chloride, polyferric sulfate, etc., and it is possible to use one or more of them.

As the organic flocculant, aminoalkyl acrylate or aminoalkyl methacrylate I~! lt homopolymers or copolymers with acrylamide or other monomers, Mannich modifications or Hofmann degradation products of polymers containing acrylamide or methacrylamide as a constituent unit, polyamide polyamines, polyvinylimidacillins, polyethyleneimines, polydialkyl diallyls Cationic organic condensing agents such as ammonium salts can be used, and one or more of these can be used.

When these inorganic flocculants and/or cationic organic flocculants are added to human waste and stirred in a neutral or acidic region, flocculation occurs and flocs are generated. At this time, in order to grow flocs, a nonionic or anionic organic flocculant may be added and stirred. Examples of the nonionic or anionic organic flocculant include polyacrylamide, polyacrylamide partial hydrolyzate, and mono- to lium-polyacrylate.

The addition rate of flocculant is 5 to 30% in case of inorganic flocculant.
Weight S, 1.3% by weight for cationic organic flocculants/
SS or less, preferably about 0.3 to 1 SS, and when both are used together, the addition rate is reduced depending on the ratio.

Although the pH of the aggregation treatment is not particularly limited, it is preferably in the neutral or acidic range (pH 4, 5 to 8). That is, human waste wastewater may be subjected to flocculation treatment without pH adjustment, but it may be adjusted to the above range by adding a pH adjuster. The stirring conditions and other aggregation conditions may be the same as those for normal aggregation treatment.

The flocs generated by coagulation are separated by solid-liquid separation. Examples of solid-liquid separation means include sedimentation tanks, pressurized flotation tanks, concentrators, etc., and concentrators such as rotary screens, wedge wire screens, and centrifuges are preferred. When using a centrifuge, reduce the centrifugal force G to reduce the S of the separated liquid.
The amount of S can be controlled.

The separated liquid separated by solid-liquid separation has good biodegradability and a BOD/N ratio of 2.5 to 3.5, so that biological nitrification and denitrification can be performed efficiently without dilution.

In this case, even without dilution, no foaming or heat generation occurs during aeration, and BOD and nitrogen are removed. Dilution here is intentionally industrial water.

It refers to the mixing of river water, seawater, treated water, etc. into a liquid, and is used as defoaming water during aeration, pump seal water, cooling water, etc.
Contamination of the system with miscellaneous water, etc., and return of sludge dewatering filtrate, dehydrator cleaning wastewater, etc. into the system are permitted.

The sludge separated by the solid-liquid separation is subjected to flocculation treatment without adding a coagulant or, preferably, with the addition of a flocculant, and then dehydrated.

The same flocculants as mentioned above can be used, but cationic organic flocculants are particularly preferred. The addition rate of the flocculant is 0.1 to 0.8% by weight/SS as a cationic organic flocculant.
(SS of raw human waste wastewater, below), preferably 0.2 to
It is about 0.4% by weight/SS.

The flocculation conditions are the same as for normal sludge dewatering. The aggregated flocs are concentrated if necessary, and then dehydrated using a dehydrator such as a bell 1 press, filter press, centrifugal dehydrator, screw press, vacuum dehydrator, or the like.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 are system diagrams showing another embodiment of the present invention, respectively, in which 1 is a first reaction tank, 2 is a second reaction tank,
3 is a solid-liquid separation means, 4 is a denitrification tank, 5 is a nitrification tank, and 6 is a solid-liquid separation tank.

In FIG. 1, human waste wastewater 7 is introduced into a first reaction tank 1, where an inorganic flocculant and/or a cationic organic flocculant 8 is injected, and if necessary, a pH adjuster 9 is injected and stirred. A flocculation reaction is carried out, and then a nonionic or anionic organic flocculant 1 is added as necessary in the second reaction tank 2.
0 is injected and stirred to grow flocs, and solid-liquid separation is performed in solid-liquid separation means 3 such as a concentrator.

The separated sludge 11 is discharged from the solid-liquid separation means 3, and the separated liquid 12 is
together with the returned sludge 13 and the returned nitrification liquid 14 into the denitrification tank 4.
and mixed with activated sludge containing denitrification seedlings in the tank.
Denitrification treatment is performed by gently stirring while blocking oxygen. Here, the denitrification shelf surface that uses BOD in the separated liquid as a hydrogen donor to reduce nitric acid or nitrite ions in the returned nitrified liquid to nitrogen becomes dominant, and the nitrogen component in the separated liquid is removed.

The denitrified mixed liquid is introduced into the nitrification tank 5, mixed with activated sludge containing nitrifying bacteria, and aerated to remove residual BOD and nitrify the nitrogen components to nitrate or nitrite ions. do.

A part of the nitrified mixed liquid is returned to the denitrification tank 4 as a return nitrification liquid 14, and the remaining part is subjected to solid-liquid separation in the solid-liquid fraction RIF'6. The separated liquid in the solid-liquid separation tank 6 is either discharged as it is as treated water 15 or is reused after being subjected to tertiary treatment such as coagulation Mco treatment. A portion of the separated activated sludge 16 is returned to the denitrification tank 4 as return sludge 13, and the remainder is discharged as surplus sludge 17.

The separated sludge 11 of the solid-liquid separation means 3 is introduced into the third reaction tank 18, and flocculation treatment is performed by injecting a flocculant 19 such as a cationic organic flocculant. The flocculated flocs are supplied to a dehydrator 20 for dehydration treatment, the separated liquid 21 is introduced into the denitrification tank 4, and the dehydrated cake 22 is subjected to post-treatments such as drying, incineration, and composting. Although the surplus sludge 17 and the tertiary treated sludge may be introduced into the third reaction tank 18, it is preferable to introduce them into the first reaction tank 1 and mix them with the human waste sewage 7.

In FIG. 2, after denitrification tank 4 and nitrification tank 5, second denitrification tank 4a, second nitrification tank 5a, third denitrification tank 4b, Except that an aeration tank 23 is provided, the separated liquid 12 is dispensed into the denitrification tank 4 and the second denitrification tank 4a, and the return nitrification liquid 14 is returned from the second nitrification tank 5a to the denitrification tank 4. The configuration is similar to that shown in FIG. Since nitrification and denitrification are performed in multiple stages here, the denitrification efficiency is high, and finally the third denitrification tank 4b
In the step, an organic substance 24 not containing nitrogen such as methanol is injected for denitrification, and the remaining organic substance is removed in a re-aeration tank 23.

In the above nitrification and denitrification process, the nitrification liquid is returned and denitrified by the denitrification process.
In order to use the BOD inside as a hydrogen donor, the denitrification tank 4 is placed in the front stage, and the nitrified liquid is returned from the nitrification tank 5 in the rear stage. Therefore, the apparatus may be configured to have a nitrification tank in the front stage and a denitrification tank in the rear stage. The treatment method shown in Figure 2 is suitable for removing nitrogen at a high removal rate, and can be modified depending on the treatment goal, such as increasing the number of nitrification and denitrification stages for more advanced treatment. It is. Further, nitrification and denitrification may be performed in a single tank.

In the above process, the star of the flocculant used is that the total amount of flocculant used in two stages is 1.2% by weight/SS or less in the case of a cationic organic flocculant, and complete flocculation is achieved in one stage. The addition rate is lower than the required addition rate of 2.0% by weight/SS for the case, and the moisture content of the dehydrated cake is also lower by about 4% than in the case of one-stage treatment. Furthermore, in the biological nitrification and denitrification treatment, there is no foaming in the nitrification tank 5 and no antifoaming agent is required, while the nitrogen removal rate is 90% or more, which is higher than when complete flocculation occurs in one stage. COD Mn of treated water is 300-400
mg/Q is slightly higher, but it is significantly lower than when directly nitrifying and denitrifying human waste water.

〔Effect of the invention〕

According to the present invention, biological nitrification and denitrification is performed by setting the BOD/N ratio of the separated liquid within a predetermined range by coagulation, so biological nitrification and denitrification can be performed efficiently with low dilution and high load, and CO
The D removal rate and the nitrogen removal rate can be stably increased.

[Embodiments of the invention]

Next, examples and comparative examples of the present invention will be described. In each example, % indicates weight %.

Example 1 Sludge removed human urine (BOD = 12000mg/Q, T-N
= 3130 rng/Q, BOD/N ratio = 3.8), iron sulfate (If) was added as Fe2+ at 1.3%/SS and stirred, and a cationic organic flocculant (methyl chloride quaternized product of aminoalkyl methacrylate and acryl chloride) was added and stirred. After flocculation, solid-liquid separation was performed using a rotary screen (60 mesh mesh).The same cationic organic flocculant was added to the separated sludge at 0.
When 13%/SS (SS of raw human waste removed) was added to perform flocculation and dehydration was performed using a Bell 1 to press dehydrator, the cake moisture was 60% and the filtration rate was 200 kg-DS/m-h. Ta. The properties of the mixture of this filtrate and the above separated liquid are B
OD=7810mgIQ, T-N=29L Orn
g/Q, BOD/N ratio = 2.7. When this mixed solution was subjected to nitrification and denitrification treatment according to the flow shown in Figure 1,
There was no foaming in the nitrification tank, and CC) D Nn of the treated water was 3.
50 +++ g/D, nitrogen removal rate was 90%.

Comparative Example 1 Iron (II) sulfate was added as Fe2+ at 3.3%/SS to the same filtered human urine as in Example 1, and stirred, and the same cationic organic flocculant was added at 1.9%/SS to achieve a pH of 6. , 8 After agglomeration, it was dehydrated using a belt press dehydrator, and the moisture content of the dehydrated cake was 62%, and the filtration rate was 150 kg-05/m-h.
Met. The properties of the dehydrated filtrate are B'C)D=5670mg/
Q, TN=2820wrg/Q, BODlN ratio=
When this was subjected to nitrification and denitrification treatment in the same manner as in Example 1, the COD rln of the treated water was 250mg/
Q: The nitrogen removal rate was 85%.

Comparative Example 2 When the same desalted human waste as in Example 1 was directly subjected to the same nitrification and denitrification treatment as in Example 1, foaming in the nitrification tank was so intense that an antifoaming agent was required, and the treated water was treated with c.

DMn was 780 mg/Q, and the nitrogen removal rate was 90%.

Example 2 To 10 volume of the removed human waste of Example 1, 1.5 volume of surplus sludge from the biological nitrification-denitrification process and 0.8 volume of flocculated sludge obtained by coagulating treated water from the nitrification-denitrification process as tertiary treatment were added. The cationic organic flocculant of Example 1 was added at 0.8%/to the mixed human waste.
SS was added, flocculation was performed using pl(6, 9), and the mixture was separated using a rotary screen.

The same flocculant was added to the separated sludge at 0.13%/SS ('a SS of combined human waste), and the first batch was dehydrated using a belt press dehydrator. The moisture content of the cake was 63%, and the degree of filtration was 18
It was 0 kg-DS/m-h. The properties of the mixed liquid of this dehydrated filtrate and the above separated liquid are SS=5290mgIQ, BO
D=707. Orng/Q, T-N=2250mg/
Q, B OD/N ratio = 3.1.

As a result of biological 61-denitrification treatment of this mixed liquid according to the flow shown in Figure 1, there was no foaming in the nitrification tank, and the CO of the treated water was
DMn is 3'OOmg/11, nitrogen removal rate is 90
%Met.

Comparative Example 3 The same cationic organic flocculant was added to the mixed human waste of Example 2 in 1.
When 6%/SS was added, the cake was flocculated at pH 6 and 9, and dehydrated using a belt press dehydrator, the cake moisture was 66%.
The filtration rate was 130 kHz-DS/m-h. When this dehydrated filtrate was subjected to nitrification and denitrification treatment in the same manner as in Example 2, the COD Mn of the treated water was 220 mg/Q, and the nitrogen removal rate was 8.
It was 4%.

Comparative Example 4 When the mixed human waste from Example 2 was subjected to nitrification and denitrification in the same manner as in Example 1, foaming in the circulation tank was intense, and the CO in the treated water was
D Kn is 560 mg/n, nitrogen removal rate is.

It was 90%.

From the above results, all of the examples used a small amount of flocculant, had excellent filtration and dehydration properties, had a low cake moisture content, and had no foaming in the nitrification tank, resulting in a high nitrogen removal rate. It can be seen that the COD of the treated water is also lower.

[Brief explanation of the drawing]

1 and 2 are system diagrams showing another embodiment of the present invention, respectively, in which 1 is a first reaction tank, 2 is a second reaction tank,
3 is a solid-liquid separation means, 4 is a denitrification tank, 5 is a nitrification tank, 6 is a solid-liquid separation tank, 18 is a third reaction tank, and 20 is a dehydrator. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Patent Attorney Sei Yanagihara Figure 1

Claims (5)

[Claims] (1) Add a flocculant to urine-based wastewater to perform flocculation separation,
A method for treating human waste wastewater, which comprises separating a separated liquid having a BOD/N ratio of 2.5 to 3.5, and subjecting this separated liquid to biological nitrification and denitrification treatment. (2) The method for treating human waste water according to claim 1, wherein the coagulation and separation of the human waste waste water causes SS in the human waste water to leak to the separation liquid side in an amount of 1,000 to 10,000 mgIn. (3) The method for treating human waste wastewater according to claim 1 or 2, wherein the flocculant is a cationic organic flocculant. (4) The method for treating night soil wastewater according to any one of claims 1 to 3, wherein the biological nitrification and denitrification treatment is performed without diluting the separated liquid. (5) The method for treating human waste wastewater according to any one of claims 1 to 4, wherein the biological nitrification and denitrification treatment is carried out repeatedly in multiple stages.