JPH0443717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus for treating human waste wastewater by coagulation treatment and nitrification and denitrification treatment.

[Prior art]

Biological treatment is the mainstream in human waste treatment, and nitrification and denitrification treatment is carried out as part of this treatment, but low dilution, high load, and advanced treatment are required due to lack of dilution water, land shortages, and stricter discharge regulations. ing. 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 necessitated the addition of a chemical agent and a large-scale defoaming and cooling device, making the maintenance and management of the device complicated, as well as raising 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. 1983-
No. 136562). However, according to this method,
Biological nitrification and denitrification of separated liquid can be performed at low dilution and high load without foaming or heat generation, but in order to stably maintain a high nitrogen removal rate, dissolved oxygen and
There was a problem in that the pH had to be maintained at a moderate value.

[Purpose of the invention]

This invention is intended to obtain a stable nitrogen removal rate in normal biological nitrification and denitrification, and is to coagulate human waste wastewater so that the BOD/N ratio of the separated liquid or an equivalent value falls within a predetermined range. By performing separation and biological nitrification and denitrification treatment of the separated liquid, biological nitrification and denitrification can be performed efficiently with low dilution and high load.
The purpose of this study is to propose a human waste wastewater treatment system that can increase the COD removal rate and nitrogen removal rate.

[Structure of the invention]

The present invention provides a coagulation separation device that performs coagulation separation by adding a coagulant to human waste wastewater, a biological treatment device that performs biological nitrification and denitrification treatment on the separated liquid of this coagulation separation device, and a method for measuring the SS of the separated liquid. Calculate the BOD/N ratio of the separated liquid or an equivalent value from the measurement device and the SS measurement value and nitrogen amount measured by this measurement device, and then calculate the BOD/N ratio of the separated liquid or a value equivalent to this, and adjust the aggregation in the coagulation separation device so that this value becomes a predetermined value. This apparatus is characterized in that it is equipped with an arithmetic and control device that controls the addition rate of the agent or the floc capture rate in solid-liquid separation.

In the present invention, human waste water is waste water containing human waste, such as collected human waste, its residue, and a mixture of these and other waste water such as excess sludge.

The total nitrogen content of collected human urine is 3000-5000mg/
Most of it is ammonia nitrogen. In a method in which such human waste is coagulated and separated in an acidic region as in the conventional method, and the separated liquid is subjected to biological nitrification and denitrification treatment,
When the cause of the decrease in nitrogen removal rate was investigated, it was found that it was due to a low BOD/N ratio of the liquid separated by coagulation and separation.

That is, when coagulation separation is performed in an acidic region, SS properties and polymeric BOD in human waste are removed, the BOD becomes low, and the BOD/N ratio becomes about 1.6. Generally, the BOD/N ratio in nitrification and denitrification treatment of human waste is approximately 3 for nitrate type and 1.8 for nitrite type. The above separated liquid has low molecular solubility that is easily utilized by denitrifying bacteria.
Nitrification and denitrification can be carried out because BOD is the main component, but it is necessary to maintain nitrite-type denitrification conditions, and if the aeration amount in the nitrification tank increases and the nitrate-type denitrification occurs, the nitrogen removal rate will decrease. It gets lower.

Therefore, in the present invention, instead of removing all the SS properties and polymer BOD in human waste wastewater by coagulation separation, the SS in the wastewater is transferred to the separated liquid side in a concentration of about 1000 to 10000.
The SS of the separated liquid is measured, and the BOD/N ratio of the separated liquid is set to a predetermined value, e.g.
The coagulation and separation conditions are controlled so that the ratio is 2.5 to 3.5, and the subsequent biological nitrification and denitrification treatment is performed efficiently. The above coagulation separation is an incomplete coagulation separation because a considerable amount of SS leaks to the separated liquid side, and the addition rate of the flocculant is lower than the addition rate required for complete dehydration.

Generally, in the case of sludge dewatering, there is an optimal addition rate of flocculant necessary 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, 30-50% of the SS component is fibrous, so it was found that solid-liquid separation can be easily performed even with insufficient coagulation. The present invention makes use of this property, and BOD is contained in the separated liquid due to insufficient coagulation.
The separated liquid is coagulated and separated so that a part of it leaks, and the separated liquid can be efficiently subjected to biological nitrification and denitrification treatment.

In the present invention, in order to perform the above treatment, a flocculation separation device that adds a flocculant to human waste and performs flocculation separation, and a biological treatment device that biologically nitrifies and denitrifies the separated liquid are provided in the above order, and the intermediate of the separated liquid
In addition to providing a measuring device to measure SS, the BOD/N ratio of the separated liquid or an equivalent value is calculated from the measured value, and the addition rate of the flocculant in the flocculant separation device is adjusted so that this value becomes a predetermined value. (And) A calculation and control device is provided to control the floc capture rate in solid-liquid separation.

In order to maintain the BOD/N ratio in the separated liquid at a value suitable for biological treatment, it is necessary to measure BOD and nitrogen, but since nitrogen in human waste water is a nearly constant value, it must be constantly measured. It is not necessary and can be measured manually. On the other hand, since BOD changes depending on the aggregation conditions, it is necessary to constantly check it.

By the way, measuring BOD is complicated and takes a long time, but in a separated liquid, BOD and SS are in a proportional relationship, so it was found that BOD can be measured by measuring SS. This is because the BOD of human waste wastewater consists of soluble BOD and SS BOD, and soluble
BOD is almost constant regardless of the coagulation separation conditions,
This is because SS-based BOD has a corresponding relationship with SS that is removed or leaked by coagulation and separation.

Therefore, by measuring the SS of the separated liquid,
The value of BOD can be measured, which allows
BOD/N ratio can be calculated. BOD／N
Since the ratio is an index of biological treatment, actual coagulation and separation conditions can also be controlled using a value equivalent to this.

As a method for controlling the coagulation and separation conditions, it is possible to control the addition rate of the coagulant or to control the solid-liquid separation conditions. The addition rate of flocculant directly affects the flocculation separation efficiency, so by controlling it,
SS leakage amount can be controlled. To change the addition rate, there are two methods: changing the amount of coagulant injected, and changing the amount of raw water supplied. Furthermore, controlling the solid-liquid separation conditions means controlling the floc capture rate in solid-liquid separation, which can be done, for example, by controlling the rotational speed of a centrifugal dehydrator.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to embodiments of the drawings.
FIG. 1 is a system diagram of the embodiment. In the drawing,
A is a coagulation separation device, which has a first reaction tank 1, a second reaction tank
It has a reaction tank 2 and solid-liquid separation means 3. P ₁ is a raw water pump, and P ₂ to _{P 4} are chemical injection pumps.

B is a biological treatment device, which has a storage tank 4, a denitrification tank 5, a nitrification tank 6, and a solid-liquid separation tank 7, and is arranged after the coagulation separation device A. P ₅ is the feed pump. C is a dehydration device, and a third reaction tank 8
and a dehydrator 9, which are arranged to dehydrate the separated sludge of the coagulation separation device A and send the separated liquid to the biological treatment device B.

A measuring device D is provided between the flocculation separation device A and the biological treatment device B to measure SS and ammonia in the separated liquid of the flocculation separation device A, and is arranged to send signals to the arithmetic and control device E. Based on the SS signal of the measuring device D, the arithmetic and control device E calculates the addition rate of the flocculant so that the BOD/N ratio of the separated liquid becomes a predetermined value, for example, 2.5 to 3.5, and determines the injection amount of the chemical injection pump P _2. It is arranged to control the solid-liquid separation means 3 by controlling or calculating the solid-liquid separation conditions, and to control the amount of liquid supplied by the liquid supply pump _P5 from the ammonia signal.

In the above configuration, in the coagulation separation apparatus A, the raw water pump P ₁ introduces human waste wastewater 10 into the first reaction tank 1, and the chemical injection pump P ₂ injects an inorganic flocculant and/or a cationic organic flocculant 11. At the same time, if necessary, adjust the pH using the chemical dosing pump P ₃ .
The conditioning agent 12 is injected and stirred to perform a flocculation reaction, and then in the second reaction tank 2, a chemical injection pump is added as necessary.
A nonionic or anionic organic flocculant 13 is injected by P ₄ and stirred to grow a floc, and solid-liquid separation is performed in a solid-liquid separation means 3 such as a concentrator.

The flocculant 11 used in the flocculation process may be either an inorganic flocculant or an organic flocculant, or both may be used in combination. It is preferable to use a cationic organic flocculant, which can effectively remove SS and BOD components with a small amount added. Examples of inorganic flocculants include aluminum chloride, polyaluminum chloride, aluminum sulfate, iron chloride (), iron sulfate (), iron chloride (), iron sulfate (), Kopparas chloride, polyferric chloride, polyferric sulfate, etc. The use of one or more species is possible.

Examples of organic flocculants include aminoalkyl acrylate or aminoalkyl methacrylate homopolymers or copolymers with acrylamide or other monomers, Mannitz modified or Hofmann decomposition products of polymers containing acrylamide or methacrylamide as a constituent unit, polyamides. Cationic organic flocculants such as polyamine, polyvinylimidazolyl, polyethyleneimine, and polydialkyl diallylammonium salt can be used, and one or more types 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 produced. At this time, in order to grow flocs, a nonionic or anionic organic flocculant 1 is added.
3 can be added and stirred. Examples of nonionic or anionic organic flocculants include polyacrylamide, polyacrylamide partial hydrolyzate, and sodium polyacrylate.

The addition rate of flocculant is 5 to 30 in the case of inorganic flocculant.
Weight%/SS, 1.3 for cationic organic flocculants
Weight %/SS or less, preferably 0.3 to 1 weight %/SS
If both are used together, the addition rate should be 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 (PH4.5 to 8). That is, human waste wastewater may be subjected to coagulation treatment without pH adjustment, but it can be adjusted to the above range by adding the pH regulator 12. The stirring conditions and other aggregation conditions may be the same as those for normal aggregation treatment.

As the solid-liquid separation means 3, there are settling tanks, pressurized flotation tanks, concentrators, etc., but rotary screens,
Concentrators such as wedge wire screens and centrifuges are preferred. When using a centrifuge, the amount of SS in the separated liquid can be controlled by reducing the centrifugal force G.

In the biological treatment equipment B, after temporarily storing the separated liquid 14 of the solid-liquid separation means 3 in the storage tank 4, the liquid supply pump
At this time, both return sludge ₁₅ and return nitrification liquid 16 are introduced into denitrification tank 5 and mixed with activated sludge containing denitrifying bacteria in the tank, with oxygen blocked. Stir gently to perform denitrification treatment. Here, denitrifying bacteria that reduce nitric acid or nitrite ions in the returned nitrification liquid to nitrogen using BOD in the separated liquid as a hydrogen donor become dominant, and the nitrogen component in the separated liquid is removed.

The mixed liquid subjected to denitrification treatment is introduced into the nitrification tank 6,
By mixing with activated sludge containing nitrifying bacteria and aerating it, residual BOD is removed and nitrogen components are nitrified to nitrate or nitrite ions. A part of the mixed liquid that has finished nitrification is returned to the nitrified liquid 16.
The remaining part is sent back to the denitrification tank 5 as solid-liquid separation tank 7 for solid-liquid separation. The separated liquid in the solid-liquid separation tank 7 is either discharged as it is as treated water 17 or is reused after being subjected to tertiary treatment such as coagulation treatment. A portion of the separated activated sludge 18 is returned to the denitrification tank 5 as return sludge 15, and the remainder is discharged as surplus sludge 19.

The processing conditions of the coagulation separation device A are
If the BOD/N ratio is set in advance to a predetermined value, for example 2.5 to 3.5, the resulting separated liquid 14 will have a BOD/N ratio within the above range in principle, and the BOD contained will be soluble. Since it is mainly biodegradable and has good biodegradability, biological nitrification and denitrification can be performed efficiently in biological treatment equipment B without dilution. In this case, even without dilution, no foaming or heat generation occurs during aeration, and BOD and nitrogen are removed. Dilution here refers to the intentional mixing of industrial water, river water, seawater, treated water, etc. with the separated liquid, and is used as defoaming water during aeration, pump seal water, cooling water, miscellaneous water, etc. Contamination within the system and return of sludge dewatering filtrate, dehydrator washing wastewater, etc. into the system are permitted.

In the dewatering apparatus C, the separated sludge 20 of the solid-liquid separation means 3 is introduced into the third reaction tank 8, and a flocculant 21 such as a cationic organic flocculant is injected to perform flocculation treatment. The flocs are supplied to a dehydrator 9 for dehydration treatment, the separated liquid 22 is introduced to a denitrification tank 5, and the dehydrated cake 23 is subjected to post-treatments such as drying, incineration, and composting.

Although the separated sludge 20 may be dehydrated without adding the flocculant 21, it is preferable to further add the flocculant 21 to perform flocculation and dewatering. 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 as a cationic organic flocculant.
SS (SS of raw human waste water, hereinafter the same), preferably 0.2
The flocculation conditions are about 0.4% by weight/SS, which is the same as for normal sludge dewatering. As the dehydrator 9, a belt press, filter press, centrifugal dehydrator, screw press, vacuum dehydrator, etc. can be used, and the water may be concentrated and dehydrated in advance. Although the surplus sludge 19 and the tertiary treated sludge may be introduced into the third reaction tank 8, it is preferable to introduce them into the first reaction tank 1 and mix them with the human waste sewage 10.

In principle, the above treatment can achieve the desired treatment effect if the coagulation separation conditions are set in advance so that the BOD/N ratio of the separated liquid 14 becomes a predetermined value. Of the top 10 human waste sewage
As SS changes over time, SS in the separated liquid also changes significantly, and the BOD/N ratio also changes accordingly.
Biological treatment efficiency decreases.

Therefore, SS and ammonia in the separated liquid 14 are measured by the measuring device D, and calculation control is performed by the calculation and control device E. Although only one measuring device D is shown in the drawing, one for SS and one for ammonia are provided separately. Measuring device D for SS
As a method, a sludge concentration meter such as a photoelectric turbidity meter using reflected light or transmitted light can be used. Second
The figure is a relationship diagram showing an example of the results of measuring SS and BOD of a flocculated separation liquid of human waste.
It can be seen that BOD is in a proportional relationship. Therefore, BOD can be measured by measuring the SS of the separated liquid.

Further, the measuring device D for measuring ammonia includes an ion meter, a colorimeter, etc., and the ammonia in the separated liquid can be measured using these, and the amount of nitrogen in the separated liquid can be obtained from this value. Since the amount of ammonia in human waste wastewater is approximately constant, it is not necessarily necessary to measure the amount of ammonia, but by measuring it, more accurate control can be performed.

The arithmetic and control unit E receives the signal from the measuring device D, calculates the BOD/N ratio from the measured value, compares it with the set value, and if it deviates from the set value, adds the necessary amount to return to the set value. The chemical injection pump _P2 or the solid-liquid separation means 3 is controlled by calculating the correction amount for the ratio or solid-liquid separation conditions. In these cases, the calculation unit E calculates the BOD/N ratio, and in order to maintain this BOD/N ratio at the set value, the amount of liquid supplied to the pumps P ₁ and P ₂ or the amount of flocs captured by the solid-liquid separation means is adjusted. Feedback control is also possible. The raw water pump _P1 may be controlled to change the addition rate. Figure 3 shows the flocculant addition rate and separated liquid for the case of adding an organic flocculant alone and for the case of combined use of an inorganic and organic flocculant.
FIG. 2 is a relationship diagram showing an example of the relationship between SS and separated liquid BOD, and aggregation conditions can be calculated and controlled according to this relationship diagram.

If ammonia is measured with measuring device D, the coagulation conditions can be controlled based on the measured value, and if the amount of ammonia in the separated liquid fluctuates, the feed pump P can be adjusted to keep the load on biological treatment device B constant. Calculates and controls the amount of liquid supplied in _{step 5} . At this time, the liquid supply pump
If _P5 is not available, raw water pump _P1 may be controlled.

In addition, in the above explanation, calculation control using the BOD/N ratio was explained, but values equivalent to this may also be used, for example, SS/N ratio, BOD/NH ₄
-N ratio, and in some cases, the value of SS may be controlled by calculation to be constant. Also, coagulation separation device A,
The configuration of the biological treatment device B etc. can be changed arbitrarily.

Next, an example of operation will be explained.

Sludge removal urine (SS=12500mg/, BOD=12100
mg/, N = 2740 mg/) in the range of 0 to 200 mg/, and a cationic organic flocculant (a copolymer of methyl chloride quaternary product of aminoalkyl methacrylate and acrylamide) according to FIG. Solid-liquid separation was performed using a rotary screen, the separated liquid was subjected to nitrification and denitrification treatment, and the amount of flocculant injection was controlled so that the BOD/N ratio was 2.5 to 3.5.
COD _Mo was 250 mg/, and the nitrogen removal rate was 95%.

As a comparative example, the amount of the above flocculant added was 250mg/
When processing was performed without controlling as
COD _Mo of treated water is 210mg/, nitrogen removal rate is 80%
It was hot.

〔Effect of the invention〕

According to the present invention, the BOD/N ratio or an equivalent value is calculated from the SS and nitrogen amount of the separated liquid,
By controlling the flocculant addition rate in the coagulation separation device or the floc capture rate in solid-liquid separation so that this value becomes a predetermined value, the separation liquid
By keeping the BOD/N ratio constant, biological nitrification and denitrification can be performed efficiently and the COD removal rate and nitrogen removal rate can be increased.

[Brief explanation of drawings]

Figure 1 is a system diagram showing an embodiment of this invention, Figure 2 is a system diagram showing an embodiment of the present invention.
The figure shows the relationship between SS and BOD of the separated liquid, and Figure 3 shows the relationship between the flocculant addition rate, the separated liquid SS, and the separated liquid BOD, where A is a flocculation separation device, B is a biological treatment device,
C is a dehydration device, D is a measurement device, E is a calculation and control device, 1 is a first reaction tank, 2 is a second reaction tank, 3 is a solid-liquid separation means, 4 is a storage tank, 5 is a denitrification tank, 6 is a nitrification tank 7 is a solid-liquid separation tank, 8 is a third reaction tank, and 9 is a dehydrator.

Claims (1)

[Claims] 1. A flocculation separation device that performs flocculation separation by adding a flocculant to night soil wastewater, a biological treatment device that performs biological nitrification and denitrification treatment on the separated liquid of this flocculation separation device, and a measuring device that measures the SS of the separated liquid. Then, the BOD/N ratio of the separated liquid or an equivalent value is calculated from the SS measurement value and nitrogen amount measured by this measuring device, and the flocculant is added in the flocculation separation device so that this value becomes a predetermined value. What is claimed is: 1. A treatment device for night soil wastewater, characterized in that it is equipped with an arithmetic and control device that controls the rate or floc capture rate in solid-liquid separation.