JPH07116683A - Silicate adding activated sludge method - Google Patents

Abstract

PURPOSE:To remove phosphorus effectively by adding a silicate to waste water to propagate microbes such as diatoms and making the microbes ingest phosphorus in the waste water excessively in the case of waste water treatment by producing floc-like activated sludge by aerobic microbes. CONSTITUTION:Waste water of a raw water tank 1 in which waste water such as domestic waste water, industrial waste water, etc., is stored is sent to a flow rate controlling tank 3 through a screen 2 by a pump P1 and then sent to a recovery and treatment tank 4 by a pump P2. The recovering and treating tank 4 has functions as an aeration tank and a precipitation tank of a continuous activated sludge treatment apparatus and a reactor 7 which is filled with pumice stone and pellets consisting of mainly zeolite, silicate powder, and humus and purifies waste water while carrying out aeration is installed in the tank 4. Waste water is circulated in a flow route including the reactor 7 and during the circulation, silicate is added repeatedly to propagate microbes such as diatoms and phosphorus in the waste water is removed by making the microbes ingest phosphorus excessively.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention effectively adds the necessary amount of silicate to wastewater such as domestic wastewater and industrial wastewater having high BOD and COD to effectively remove the phosphorus contained in this wastewater. The present invention relates to a silicic acid-added activated sludge method that can be removed.

[0002]

2. Description of the Related Art Recently, eutrophication of the coastal waters of cities in Japan has become a big problem. This eutrophication means that when seawater reaches an excessive nutritional state, phytoplankton grows abnormally and causes oxygen deficiency, which kills seafood and plankton, resulting in an organic bottom called sludge on the seabed. That is, mud is generated. This eutrophication in the coastal waters of the city is caused by the inflow of wastewater such as domestic wastewater and industrial wastewater containing a large amount of nitrogen and phosphorus into the sea area. Effective removal of phosphorus is required. Biological nitrification and denitrification methods have been theoretically established as economical and effective methods for nitrogen removal, but there are various phosphorus removal technologies described below. The fact is that it has major drawbacks and no effective method has yet been established.

The conventional phosphorus removal techniques are roughly classified into those using a drug and those not using this drug. The former technique is to add metal salts such as aluminum salt and iron salt to raw water and react with metal salts to remove phosphorus by coagulant addition method, or phosphate ion and calcium ion in raw water. A typical example is a “crystallization method” utilizing a crystallization reaction of hydroxyabatite produced by the reaction of hydroxide ion. This "coagulant addition method" has the advantage of having a high phosphorus removal function, but has the disadvantage of increasing the amount of sludge generated and not being able to reuse the removed phosphorus. Further, the "crystallization method" has an advantage that the amount of generated sludge is small, but has a disadvantage that a new pretreatment facility such as a decarbonation tank and a sand filtration facility is required. On the other hand, the "biological dephosphorization method", which does not use drugs, releases phosphorus in the anaerobic state and takes in the phosphorus released in the aerobic state to increase the concentration of phosphorus and remove it. However, since the removal rate is low, there is a disadvantage that a drug must be used as a result. As described above, each of the conventional phosphorus removal techniques has advantages and disadvantages, and the disadvantages are particularly large.

From the viewpoint of "phosphorus removal", it is known in the field of fisheries science that diatoms have an ability to adsorb about 30 times as much phosphorus as necessary. . In addition, many of these diatoms are phytoplankton, but their life is supported by heterotrophs, and some of them are white species that do not have chlorophyll. It is also known that silicic acid is an essential substance in addition to nutrient salts such as nitrogen and phosphorus for the growth of this diatom.

[0005]

DISCLOSURE OF THE INVENTION The present invention is contained in wastewater such as domestic wastewater and industrial wastewater by the activated sludge method based on the knowledge of fisheries science that diatoms have an active phosphorus uptake action. The challenge is to effectively remove phosphorus.

[0006]

[Means for Solving the Problem] The means adopted by the present invention for solving this problem is to stir while injecting air into wastewater to generate floc-like activated sludge by the action of aerobic microorganisms. In the activated sludge method that treats sewage with sewage, the required amount of silicate is added to the sewage that is the raw water to be treated to generate microorganisms that have silicates such as diatoms as essential nutrients and are included in the sewage. The phosphorus is removed from the wastewater by causing the microorganism to excessively ingest the existing phosphorus.

[0007]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 is a conceptual diagram of a batch type activated sludge treatment device for carrying out the present invention. BOD in raw water tank 1
Wastewater, which is raw water to be treated such as COD, other domestic wastewater, and industrial wastewater, is stored, and the wastewater in the raw water tank 1 is regularly sent to the flow rate adjusting tank 3 through the screen 2 by the pump P ₁ . . The screen 2 removes coarse solids contained in the wastewater. The dirty water in the flow rate adjusting tank 3 from which the coarse solid matter has been removed is periodically sent to the batch processing tank 4 by the pump P ₂ .

This batch treatment tank 4 is used as both an aeration tank and a precipitation tank in a continuous type activated sludge treatment apparatus, and an aerator 5 for aeration is provided at the bottom of the batch treatment tank 4 for treating the internal wastewater. Is periodically aerated to supply oxygen. The aerator 5 has a blower (not shown).
Is supplied with low-pressure air and is ejected inside the wastewater to be treated, whereby the wastewater is stirred. Also,
If air continues to be supplied from the aerator 5 into the sewage, the dissolved oxygen concentration (DO) increases, so a DO controller 6 for detecting this is provided, and the dissolved oxygen concentration (DO) is automatically controlled. .

In the batch treatment tank 4, a wastewater inflow step of sending the wastewater to be treated from the flow rate adjusting tank 3 and an aeration step of ejecting air from the aerator 5 to supply oxygen into the wastewater are produced. The precipitation step of precipitating the activated sludge and the discharging step of discharging the supernatant water of the upper layer are continuously repeated. In addition, zeolite, calcium silicate,
Pellets mainly composed of silicic acid powders such as obsidian and shell fossil and humus are made, and the pellets and pumice are filled in a stainless steel container, and a reactor 7 having a structure that allows the passage of sewage while aeration is provided in the container. The waste water in the batch treatment tank 4 is sent to the reactor 7 by the pump P ₃ , and then part of the waste water is returned to the batch treatment tank 4 to circulate in the flow path including the reactor 7. In the meantime, silicic acid is repeatedly added to the wastewater. Of the wastewater to which the silicic acid has been added in the reactor 7, the wastewater that has not been returned to the batch treatment tank 4 is returned to the flow rate adjustment tank 3. In this way, silicic acid is repeatedly added to the wastewater while the wastewater circulates in the reactor 7. The reason for returning part of the wastewater to which the silicic acid has been added in the reactor 7 to the flow rate adjusting tank 3 is to add the silicic acid to the wastewater in advance before aeration. The reactor 7 is aerated only during the sewage inflow process and the aeration process, and the aeration is stopped during the other processes.

Then, only in the sewage inflow process and the aeration process, the pump P ₃ and the reactor 7 are operated to add silicic acid to the sewage in the batch treatment tank 4 to perform sewage treatment. Flocs (which are called "activated sludge") are formed, and in the precipitation process,
The flocs settle on the bottom of the batch processing tank 4, and the upper layer of the processing tank 4 is purified. After this precipitation step, the supernatant water purified in the upper layer portion of the batch treatment tank 4 is discharged and stored in the discharge adjusting tank 8, and the sludge settled at the bottom of the batch treatment tank 4 is pumped by the pump P ₄ . It is pumped out and stored in the sludge storage tank 9.

The above example is one in which the present invention is carried out in a batch type activated sludge method, but the aeration tank and the sedimentation tank are separated and the aeration tank is a continuous type which is always operating. It is also possible to carry out the invention. Also, regarding the method of adding silicic acid, if sewage is circulated in the aerator part of the aeration structure as described above, there is an advantage that the dissolution rate of silicate in the sewage increases, but simply add powdered one. However, the addition method itself is not limited at all.

The activated sludge method according to the present invention is characterized by adding silicic acid to the sewage which is the raw water to be treated, and FIG. 2 shows the continuous activated sludge method in which the aeration tank is constantly operating. The phosphorus removal data is shown, which is a monthly measurement of the quality of the treated wastewater according to the invention throughout the year. It can be seen that the phosphorus contained in the inflow water before the treatment was also removed at a high rate in the treated water, and the released water was also removed at a high rate close to 95% per year on average. Also in this continuous activated sludge method, the method of adding silicic acid to the wastewater was carried out using the same structure as the reactor 7 described above. Thus, phosphorus in sewage is removed by the addition of silicic acid, because the substrate of wastewater is changed by the addition of silicic acid, and diatoms that have this silicate as an essential nutrient in activated sludge microorganisms. This is probably because the diatoms were proliferated and excessively ingested (adsorbed) phosphorus contained in the wastewater raw water.

[0013]

INDUSTRIAL APPLICABILITY According to the present invention, in the activated sludge method, a required amount of silicate is added to the wastewater which is the raw water to be treated to generate a microorganism having silicate such as diatom as an essential nutrient. Since it is a purely biological dephosphorization method, which is characterized in that phosphorus contained in sewage is excessively ingested by the microorganisms, thereby removing phosphorus from the sewage, the following effects are exhibited. To be done. (1) In the coagulation method using chemicals, in addition to the original activated sludge produced by the action of microorganisms, sludge based on the use of the coagulant is separately generated, resulting in an increase in the amount of sludge generated. Therefore, since the present invention is a pure biological dephosphorization method without using any chemicals, there is no increase in the amount of generated sludge. (2) In the coagulation method using a chemical, phosphorus is caused by reacting and removing a metal salt such as an aluminum salt or an iron salt,
The removed phosphorus is strongly bound to this metal salt and is in a form that is difficult to be used as a fertilizer for plants, whereas phosphorus taken into diatoms in the present invention does not have such a phenomenon. Since it is a form that can be easily used by plants as fertilizer, the removed phosphorus can be reused. (3) Silicic acid, which is the main component of soil and is abundant on the earth, is used, so it is easy to implement and does not cause secondary pollution. (4) Diatoms generated in sewage water by the addition of silicic acid have an inorganic shell and are larger than the main activated sludge microorganisms, so when dewatering the generated sludge, it clogs the filter cloth. Is less likely to occur, and as a result, improvement in dewaterability during sludge dewatering can be expected. (5) Since silicic acid may be added in some form to the sewage raw water to be treated, it can be easily carried out with existing equipment.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a batch type activated sludge treatment device for carrying out the present invention.

FIG. 2 is a diagram showing measurement data of dephosphorization according to the present invention.

[Explanation of symbols]

 1: Raw water tank 2: Screen 3: Flow rate adjusting tank 4: Batch processing tank 5: Aerator 6: DO controller 7: Reactor 8: Discharge adjusting tank 9: Sludge storage tank

Claims (1)

[Claims] 1. An activated sludge method for treating sewage by agitating while blowing air into the sewage to generate floc-like activated sludge by the action of aerobic microorganisms. The required amount of acid salt is added to generate microorganisms such as diatoms that have silicate as an essential nutrient, and phosphorus contained in wastewater is excessively ingested by the microorganisms to remove phosphorus from wastewater. The activated sludge method with addition of silicic acid, characterized in that