JPS6242796A - Treatment of waste water and method for acclimatizing activated sludge - Google Patents

Abstract

PURPOSE:To efficiently remove eutrophic materials from waste water contg. the eutrophic materials by controlling and administrating the oxidation reduction potential (ORP) of a biochemical reaction vessel in the stage of treating the above-mentioned waste water with a batch-wise activated sludge method. CONSTITUTION:One cycle of the process of removing the eutrophic materials consists of the following 5 stages. The waste water is fed into the biochemical reaction vessel where the activated sludge exists and the ORP is controlled and administered to an optional value of -200--300mV by mechanically stirring the waste water in the 1st stage. The ORP is maintained for the prescribed period at +100--120mV by removing BOD and phosphorus compd. from the waste water and aerating the water in the stage of oxidizing the ammonia compd. to nitrogen oxide in the 2nd stage. The waste water is mechanically stirred and a hydrogen donator is fed to the water to decrease the ORP down to -50--150mV in the stage for reducing the nitrogen oxide to N2 in the 3rd stage. Aeration is executed to decompose the excess hydrogen donator and the ORP is adjusted to +50-+150mV in the 4th stage. The activate sludge is settled and about >=80% supernatant is released in the 5th stage.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to wastewater containing pollutants (hereinafter abbreviated as BOO) indicated by biochemical oxygen demand, ammonia compounds, nitrogen compounds, phosphorus compounds, etc. in sea areas, rivers, lakes and marshes. The present invention relates to a method for removing substances that cause eutrophication using a batch activated sludge treatment method.

The present invention also relates to a method for acclimatizing activated sludge produced in a continuous activated sludge process by oxidation-reduction potential (ORP) management control so that the aforementioned eutrophic substances can be removed by a batch activated sludge process.

The present invention can be applied to wastewater containing a large amount of eutrophic substances, such as urban sewage, underground water, and processing industrial wastewater from livestock, fishing, and other industries.

Conventional technology Many methods have been proposed to remove the above-mentioned eutrophic substances by batch or continuous activated sludge treatment.For example, BOO from industrial wastewater, urban sewage, etc.
JP-A No. 55-84896 and JP-A No. 54-2 show that the amount of aeration can be efficiently removed by controlling the amount of aeration using RP as an index.
2955, Water Treatment Technology vol 23, No. 7. P5
5 (+982) etc.

In addition, the method for biochemically removing ammonia compounds from wastewater is to first nitrify the ammonia compounds into nitrate and nitrite compounds using an aerobic biochemical method, and then convert these nitrogen oxides into nitrates using an aerobic biochemical method. A common chemical method is to add a hydrogen donor such as methanol to reduce it to nitrogen gas. The involvement of ORP in removing ammonia compounds by biochemical methods is as shown below.

In other words, in the process of oxidizing ammonia compounds to nitrogen oxides, ORP is involved, as disclosed in JP-A-54.
-152351 and Japanese Patent Publication No. 52-22918 that it is appropriate to control the ORP of a denitrification tank when reducing nitrogen oxides to nitrogen gas.

Although the principle of removing phosphorus compounds from wastewater is not well established, the following is generally accepted.

In other words, if activated sludge is placed alternately in an aerobic environment and a mono-aerobic environment, stress will occur in the activated sludge, and in the aerobic environment, phosphoric acid in wastewater will be taken into cells excessively, and it will be converted into polyphosphoric acid. Activated sludge stored in a zero-order sickle environment releases polyphosphoric acid stored within the cells. When such conditions are repeated, activated sludge takes up phosphorus into cells in an aerobic environment, resulting in a decrease in the concentration of phosphorus discharged in the biochemical reactor. These properties of activated sludge are used to remove phosphorus compounds from wastewater.

As mentioned above, the method of removing eutrophic substances such as ROD, ammonia compounds, nitrogen oxides, and phosphorus compounds from wastewater solely by biochemical methods can be said to be an almost established technology. However, with the batch activated sludge method, BOD
It is difficult to remove all eutrophic substances such as , ammonia compounds, nitrogen oxides, and phosphorus compounds using only the combination of the known methods described above.

In other words, in the batch activated sludge method, it is difficult to remove the aforementioned eutrophic substances all at once, and it is necessary to combine processes that sequentially remove each eutrophic substance. , ORP, PH1 dissolved #element concentration, treatment time, etc.) and the residual amount of eutrophic substances from the previous step, etc., need to clarify the influence they have on the removability of eutrophic substances in the next step. In particular, removal conditions for phosphorus compounds are not clearly presented.

In other words, it is said to be an aerobic environment or an anaerobic environment, but no specific conditions are specified.

It is therefore clear that all eutrophic substances in wastewater cannot be removed by a simple combination of known techniques;
It can be said that the technology for removing eutrophic substances using the batch activated sludge method has not been established.

Problems to be Solved by the Invention When eutrophicating substances such as BOD, ammonia compounds, nitrogen oxides, and phosphorus compounds in wastewater are efficiently removed by the batch activated sludge method, the following problems arise. be.

(1) The order in which each eutrophic substance is removed is not clear.

(2) The conditions for removing each eutrophic substance, ie, aerobic and anaerobic conditions, are not specifically specified.

(3) When each eutrophic substance in wastewater is removed sequentially, the influence of the previous process on the subsequent process is uncertain. For example, the amount of eutrophic substance remaining in the previous process or the ORP
It is not clear how processing conditions such as dissolved oxygen concentration, pH, etc. affect the processability of subsequent processes.

(4) A method for gll-resistant activated sludge that can remove eutrophic substances using a batch activated sludge method has not been clarified. In other words, the activated sludge used in the batch activated sludge method is often the activated sludge of the continuous activated sludge method as the seed sludge.
A method for acclimating activated sludge that can remove the aforementioned eutrophic substances, especially phosphorus compounds, has not been established.

Means for Solving the Problems The present invention relates, as a first invention, to a method for removing eutrophic substances from wastewater by a batch activated sludge method.The features of the present invention are as follows.

(1) The process from injecting wastewater into the biochemical reaction tank of a batch-type activated sludge treatment equipment to discharging treated water from which eutrophic substances have been removed using activated sludge consists of a five-step treatment process. ing. Note that the present invention combines these five steps into one
Cycle.

(2) In each stage of the treatment process, the oxidation-reduction potential (ORP) of the biochemical reaction tank can be controlled and managed, and each eutrophication substance can be efficiently removed.

(3) Another effect of dividing one cycle into five processing steps is X! I! Using activated sludge with subsequent activated sludge treatment,
The batch activated sludge method can efficiently remove eutrophic substances from wastewater. The biochemical reaction tank (hereinafter abbreviated as reaction tank) of the batch type activated sludge treatment equipment used in the present invention includes an aeration device 1, a mechanical stirring device, and an OR
Sensors for measuring P, pH1, dissolved oxygen concentration, temperature, etc. are installed, and these sensors are connected to a control device and a recording device, making it possible to control, measure, record, and manage these inside the reaction tank. It should be noted that the best ORP sensor used for activated sludge treatment is a composite electrode made of gold or gold alloy and silver chloride/silver, and other sensors can hardly be used.

Next, the functions, actions, and characteristics of each step in one cycle of removing eutrophic substances according to the present invention will be explained. In the first step, a predetermined amount of wastewater containing eutrophic substances such as EIOD, ammonia compounds, nitrogen oxides, and phosphorus compounds is injected into a reaction tank containing activated sludge while stirring. At this time, the ORP of the reaction tank gradually decreases, and eventually the ORP decreases to -200 to -300 V, resulting in a markedly anaerobic state. When such an anaerobic environment is maintained for 30 minutes to 2 hours, phosphorus in the activated sludge is released into the waste water.

For example, the content of phosphorus compounds in activated sludge before wastewater injection is 3.
~5% (as phosphorus), and phosphorus compounds in wastewater are ~4%
6mg/g (as phosphorus) is injected with wastewater and the ORP is -200 to -300V in an anaerobic state.
．． When held for 5 to 2 hours, the concentration of 1) phosphorus compounds in the activated sludge decreases to 1 to 2 mg/g (as phosphorus), and the concentration of phosphorus compounds in the reaction tank increases to 7 to 9 mg/9.

As described above, the first stage is a step in which ORP is lowered, anaerobic stress is applied to activated sludge, and phosphorus compounds are released. Note that the ability to remove phosphorus compounds may vary depending on the ability of the activated sludge to take up phosphorus compounds in the subsequent process or the concentration of phosphorus compounds in wastewater.
In some cases, it may be desirable not to release a large amount of phosphorus compounds in this process, and in order to suppress the release of phosphorus from activated sludge, the ORP of the reaction tank is set at -100 to -300 mV.
Better yet -200 to -250mV control! ]! ! Delicious.

The second stage is the removal of Boll, the phosphorus compounds in the wastewater and the
The process involves making the activated sludge adsorb excess phosphorus compounds released by the activated sludge in the step, and oxidizing ammonia compounds, organic amine compounds, etc. into nitrogen oxides. Therefore, the second stage must be maintained in an aerobic environment, and the ORP suitable for performing all the above actions is +100 to +12.
It is 0 mV or more.

If the ORP of the reaction tank is controlled to +100 to +120 mV or more and aeration is performed, the reaction time will be 2 to 4 hours.
Niha after an hour, c7 during drainage) 100-30 (lsg/i
) BOD is less than 10 mg/i, Mf = 20 to 50
mg/fj (nitrogen) of ammoniacal nitrogen and Kjeldahl nitrogen are oxidized to 1-2 I1g/i
! while nitrate and nitrite nitrogen increase to 20-30 g/i or more.

In the first stage, the phosphorus compounds in the waste water of the reaction tank are
9I1g/9 (as phosphorus) is reduced to 0.5mg/Q (as phosphorus) or less, and the phosphorus concentration of activated sludge is 3~
Increase to 5%. In this case, in order to adsorb phosphorus compounds to the activated sludge, rather than simply changing the aerobic environment and anaerobic environment alternately to apply stress, the activated sludge is activated in the aerobic environment following the anaerobic environment as in the present invention. When sludge is subjected to decomposition of 800 components or oxidation of ammonia compounds, etc., the amount of phosphorus compounds taken into activated sludge is significantly increased. This is because the activated sludge releases phosphorus compounds in the anaerobic environment in the first stage, and is starved for phosphorus compounds in the aerobic environment, which causes the decomposition of BOO components.
Phosphorus compounds are required as a nutrient source due to nitrification reactions, so it is thought that large amounts of phosphorus compounds are taken up in a reactionary manner.

The third stage is a step in which nitric acid or nitrite nitrogen oxides are reduced to nitrogen gas and removed.

In order to reduce this nitrogen oxide with activated sludge, aeration is stopped and mechanical agitation is performed. At this time, a hydrogen donor is required, but this hydrogen donor is used to transfer the used wastewater to the reaction tank. or methanol,
Organic substances such as isopropyl alcohol, molasses, and rice bran can also be used.

This third stage significantly affects the concentration of nitrogen compounds and phosphorus compounds in the treated water, which is discussed in the fifth stage, so the OR of one reaction tank is
Control of P and nitrogen oxide concentrations is important. In other words, when a hydrogen donor is added and mechanical stirring is performed, the O in the reaction tank is reduced.
RP drops to 0 to −30 hV. Especially ORP is -25
When the voltage decreases to 0 to -300 mV, phosphorus compounds are released from the activated sludge, and the phosphorus compounds in the reaction tank become high. Another problem is that when such an anaerobic environment is used, anaerobic decomposition of the activated sludge occurs and the nitrogen concentration of ammonia compounds, organic amine compounds, etc. in one reaction tank also increases. Therefore, in some cases, a phosphorus compound may be added in the next step.
Removal of nitrogen compounds, etc. is required, making the treatment process extremely complicated.

In order to prevent these problems from occurring, ORP of the reaction tank is
Management is important. In other words, there is a correlation between ORP and nitrogen remaining in the reaction tank 1; concentration of chemical resistant substances and release of phosphorus compounds of activated sludge, and anaerobic decomposition; nitrogen oxides are 0.2 ~0.3 mg/l (as nitrogen) or less, ORP becomes -200 to -300 mV, and O
When RP is in the range of -50 to -150 mV, the nitrogen oxide concentration in the reaction tank can be maintained at 0.5 to 1.0 mg/Q (as nitrogen), and in an anaerobic environment of this level, the nitrogen oxide concentration can be maintained at 0.5 to 1.0 mg/Q (as nitrogen). Release of phosphorus compounds from sludge and anaerobic decomposition of activated sludge can be suppressed. Therefore, the third
In the step, the ORP of the reaction tank is -50 to -150 mV.
It is necessary to control and manage within the range of However, it is difficult to control and manage the ORP within this range with only mechanical stirring, and when the ORP drops below -50 to -150 mV, air conditioning of the reaction tank is performed using the ORP control device to keep the ORP at -50 to -150 mV. maintained within the range for a predetermined period of time.

In the fourth stage, in order to remove the excess hydrogen donor used in the third stage, air conditioning is performed to maintain an aerobic environment. The ORP and retention time in this fourth stage vary by 1 depending on the type of hydrogen donor used and the regulatory value of the treated water discharged in the fifth stage. In other words, if the nitrogen regulation value of the treated water to be discharged in the fifth stage is very strict, and if wastewater containing ammonia compounds and organic amine compounds is used as a hydrogen donor, it must be subjected to nitrification and denitrification before being discharged. In such a case, in the fifth stage, it is necessary to oxidize ammonia compounds, organic amine compounds, etc. in the wastewater to nitrogen oxides, and the ORP will be +50 to +1.
It is necessary to maintain 50 mV, preferably +100 to +150 mV.

On the other hand, if the nitrogen regulation value of the treated water in the fifth stage is loose, or if a hydrogen donor that does not contain nitrogen is used, it is only necessary to remove the excess hydrogen donor or BOD component.
What is necessary is to control and manage ORP to +50 to +8 hV.

In the fifth stage, the air conditioner and mechanical stirring in the reaction tank are stopped, the activated sludge is allowed to settle, and about 80% or more of the supernatant water is discharged. In addition, if the nitrogen regulation value for effluent water is strict,
It is necessary to reduce the nitrogen oxides produced in the fourth stage,
When a hydrogen donor is added, the binary process is completed in a short time, but even if the hydrogen donor is not added, if the standing settling time of the activated sludge is prolonged, the ORP can be lowered and nitrogen oxides can be removed. Note that when the ORP in the reaction tank becomes an anaerobic environment of -200 mV or less, the phosphorus compounds taken into the activated sludge are released, and the concentration of phosphorus compounds in the treated water discharged in the fifth stage may increase. Therefore, the fifth stage OR
The limit for P is -50 to -150 mV, and it is necessary to control it within this range.
~1.0-8/inclusive (as phosphorus) or less.

ORP control management in this fifth stage cannot be performed by an air radio controller. That is, when air conditioning is performed, activated sludge does not settle and flows into the treated water. For this reason, it is best to manage the ORP u4 concentration based on the concentration of remaining nitrogen oxides, and in the fifth stage, the nitrogen oxides in the biochemical reaction tank should be controlled at 0.5 to 1. Omg/i! (
(as nitrogen) to reduce ORP from -50 to -150+
*Can be maintained at V. Nitrogen oxides from 0.5 to 1.0
In order to maintain +eg/i (as nitrogen), it is recommended to control and manage the ORP in the third stage to -50 to -150+sV.

In the third stage, if an ammonia compound is used as a hydrogen donor and wastewater containing amine compounds, such as sewage, is used, and if the ORP of the reaction tank is +100 to +120 mV or more in the fourth stage, nitrification will occur. A reaction takes place, forming nitrogen oxides. If this nitrogen oxide is not sufficiently removed in the fifth stage, it is carried into the first stage of the next cycle, and the nitrogen oxide in the first stage of the next cycle is reduced to 0.
If it is present in an amount of 5 mg/71 or more, the ORP may not be sufficiently reduced and the release of phosphorus compounds from activated sludge may not occur. To prevent this, increase the ORP of the 4th stage by +50~
It is necessary to control the voltage to +80 mV to suppress the production of nitrogen oxides, or to reduce the nitrogen oxides produced in the fourth stage to 0.5 tag/Q or less in the fifth stage.

Next, a method of acclimating activated sludge suitable for batch activated sludge treatment to activated sludge for continuous activated sludge treatment, which is the second invention of the present invention, will be explained. Even if activated sludge from continuous activated sludge treatment such as municipal sewage is used as activated sludge for the batch activated sludge method, it does not have the ability to immediately incorporate excessive phosphorus compounds from wastewater into activated sludge. Furthermore, the acclimatization method for giving activated sludge from continuous activated sludge treatment the above-mentioned functions has not been clarified. When applied, eutrophic substances in wastewater can be removed in a short period of 2 to 5 days by a batch activated sludge method.

Example 1 This shows an example of the method for acclimatizing activated sludge used in the batch activated sludge method of the present invention. Sludge mixed liquid (activated sludge mixed liquid 2500
20 mg/%) was collected and transferred to a biochemical reaction tank (effective volume: 301) of a batch-type activated sludge treatment experimental device, and the activated sludge was acclimatized.

The acclimatization method was as follows: aeration of the reaction tank and mechanical stirring were stopped, the activated sludge was left to settle, and most of the clear water was discharged into 6. This took about 1 hour as the first step, as shown in Table 1. The mixture was injected into urban sewage with mechanical stirring to bring the total volume to 20Q. Mechanical stirring was further performed for about 30 minutes, and the ORP in the reaction tank was controlled at -250 mV by aeration.

Next, as a second step, mechanical stirring and aeration were performed to maintain the ORP in the reaction tank at +100 to +120 fog V for 4 hours and 30 minutes.

In the third stage, aeration is stopped and only mechanical stirring is performed, and about 50% of the municipal sewage in Table 1 is injected over a period of 30 minutes, followed by mechanical stirring for about 2.5 hours. When the ORP became -130 mV or less, aeration was performed intermittently to control the ORP within this range.

In the fourth stage, aeration and mechanical stirring were performed for about 1 hour and 15 minutes so that ORP was +80 mV.

In the fifth stage, aeration and mechanical stirring are stopped, the activated sludge settles for about 45 minutes, and then the supernatant water is pumped for about 45 minutes.
It took a few minutes to drain the water, and after draining, it was allowed to stand still for about 15 minutes.

One cycle from the first stage to the end of the fifth stage takes approximately 12 hours. When this cycle experiment is carried out for 3 to 5 days, the water quality of the effluent water (treated water) is as shown in Table 1.
Total phosphorus was 0.4 tag/Q, and activated sludge that can remove eutrophic substances from urban sewage by the batch activated sludge method was able to be acclimated.

Table 1. Properties of urban sewage and treated water Example 2 Using the activated sludge acclimatized in Example 1, a treatment experiment was conducted for three cycles a day. The time allocation is as follows.

First, in the first step, the urban sewage shown in Table 1 was injected over a period of about 1 hour while mechanically stirring, and the total amount was about 20 tons.

Immediately perform the second stage of aeration for approximately 2 hours.
+140mV control management.

In the third stage, aeration is stopped, only mechanical agitation is performed, and 5fL of urban sewage water is injected in about 30 minutes, and OR
P was controlled at -150 mV. This time is about 2 hours. If ORP falls below -150mV, perform aeration intermittently and perform ORP control management.

The fourth stage is aeration for about 30 minutes to increase ORP.
Control and manage over 80 degrees.

Thereafter, aeration and mechanical stirring were stopped, and the activated sludge was allowed to settle, and the supernatant water was discharged for about 45 minutes.

After the water has been discharged for about 15 minutes, the next cycle of municipal sewage is injected. In this way, the quality of the treated water treated three times a day has BOD of approximately 3 to 511 g/q, Kjeldahl nitrogen of 5 to 7 g/2, and ammonia nitrogen of 4 to 5 g/q.
5 mg/immune, total phosphorus is 0.3 tag/Q. Note that both nitrate and nitrite nitrogen were below l tag/Ll.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention provides a batch activated sludge treatment in which wastewater is injected into a reaction tank and activated sludge is used to treat Boo,
By dividing the process from removing eutrophic substances such as ammonia compounds, nitrogen oxides, and phosphorus compounds to discharging wastewater into five stages, eutrophic substances can be efficiently removed. Furthermore, the present invention is an extremely effective method for acclimating activated sludge from continuous activated sludge treatment using a batch activated sludge treatment method.

Claims (5)

[Claims] (1) When treating wastewater containing eutrophic substances such as pollutants (BOD), ammonia compounds, nitrogen oxides, and phosphorus compounds as indicated by biochemical oxygen demand using the batch activated sludge method, biological A wastewater treatment method, characterized in that the eutrophic substances are removed by controlling and managing the oxidation-reduction potential (ORP) of a chemical reaction tank. (2) An ORP sensor made of gold or gold alloy, silver chloride, and silver is installed in a biochemical reaction tank, and the ORP value is controlled to be suitable for removing eutrophic substances. The wastewater treatment method described in (1). (3) The wastewater treatment method according to claim (1) or (2), wherein one cycle of the process for removing eutrophic substances consists of the following five steps. The first step is to place activated sludge in a biochemical reactor.
Inject wastewater with mechanical stirring and reduce ORP to -20
It is controlled and managed using an arbitrary ORP value in the range of 0 to -300 mV. In the second stage, aeration is performed to remove BOD and phosphorus compounds, and to oxidize ammonia compounds to nitrogen oxides, and the ORP is maintained at +100 to +120 mV or higher for a predetermined period of time. The third stage is the process of reducing the nitrogen oxides produced in the second stage to nitrogen gas, where mechanical stirring is performed, a predetermined amount of hydrogen donor is injected, and the ORP is reduced to -50 to -150 mV. The ORP control is performed for a predetermined period of time. In the fourth stage, aeration is performed, with the main purpose of decomposing excess hydrogen donor, and ORP is controlled and managed at an arbitrary value in the range of +50 to +150 mV. The fifth stage is to stop aeration and mechanical stirring;
The activated sludge is allowed to settle and approximately 80% or more of the supernatant is discharged. (4) In order to prevent the release of phosphorus compounds from activated sludge in the third stage, the ORP of the biochemical reaction tank is set to -50 to -
The nitrogen oxide concentration in the tank was controlled at 150 mV to 0.5
The wastewater treatment method according to claim 3, wherein the wastewater treatment method is maintained at 1.0 mg/l (in terms of nitrogen). (5) Activated sludge that is characterized in that activated sludge from continuous activated sludge treatment is acclimatized to remove eutrophic substances in wastewater by a batch activated sludge method in which one cycle consists of the following five steps. How to get used to it. The first step is to place activated sludge in a biochemical reactor.
Inject wastewater with mechanical stirring and reduce ORP to -20
It is controlled and managed using an arbitrary ORP value in the range of 0 to -300 mV. In the second stage, aeration is performed to remove BOD and phosphorus compounds, and to oxidize ammonia compounds to nitrogen oxides, and the ORP is maintained at +100 to +120 mV or higher for a predetermined period of time. The third stage is the process of reducing the nitrogen oxides produced in the second stage to nitrogen gas, using mechanical stirring and injecting a predetermined amount of hydrogen donor to reduce the ORP to -50 to -150 mV. The ORP control is performed for a predetermined period of time. In the fourth stage, aeration is performed, with the main purpose of decomposing excess hydrogen donor, and ORP is controlled and managed at an arbitrary value in the range of +50 to +150 mV. The fifth stage is to stop aeration and mechanical stirring;
The activated sludge is allowed to settle and approximately 80% or more of the supernatant is discharged.