JPS6174698A - Waste water treatment - Google Patents

Abstract

PURPOSE:To progress efficiently dephosphorization and denitrification without being interfered by the other in respective anaerobic tanks for dephosphorization and denitrification by disposing two anaerobic tanks in parallel so that the waste water can be respectively directly introduced therein unlike the conventional anaerobic and aerobic continuous treatment method. CONSTITUTION:The waste water W contg. BOD, nitrogen and phosphorus components is branched to two lines which are respectively introduced dividedly to the anaerobic tank 1 for dephosphorization and the anaerobic tank 2 for denitrification installed in parallel in the method for treating said waste water in the anerobic and aerobic stage. The waste water is treated together with return sludge in the former and together with circulating liquid for nitrifying in the latter and thereafter the treated water are joined. The joined water is treated in an aerobic tank 3 and is then conducted into a settling tank 4 where the water is separated to the sludge and the treated water. Part of the sludge is returned at the same time to the tank 1 and on the other hand part of the liquid treated in the tank 3 is circulated as the circulating liquid 5 for nitrifying into the tank 2. The dephosphorization and denitrification are thus efficiently executed in the tanks 1, 2 without being interfered by the other. As a result, the rate of removing phosphorus and nitrogen is improved as a whole even if the tank capacity is the same as in the conventional practive.

Description

[Detailed description of the invention] Industrial application field) The present invention is directed to wastewater contained in sewage, raw wastewater, and various industrial wastewater.
The present invention relates to a wastewater treatment method that biologically removes BO1'), nitrogen, phosphorus components, etc.

Prior art) As biological denitrification/dephosphorization methods, anaerobic, aerobic continuous methods, batch methods, etc. have been developed and are attracting attention as developments of the conventional activated sludge method.

These methods produce BOD, C! along with nitrogen and phosphorus! It is possible to remove organic components such as OD, there is no sludge swelling phenomenon due to bulking, and it has good settling properties.The surplus sludge has a high content of phosphorus, which has high utility value as fertilizer, etc., and the operating method is specially designed. It has many advantages such as not having any difficult aspects.

The flow sheet shown in Figure 2 is the conventional anaerobic and aerobic flow.

These are seven representative examples of continuous law. The following will be explained based on the ratio.

W is the raw water, (1) is the anaerobic tank for denitrification (2) is the anaerobic tank for denitrification (3) is the aerobic tank (4) is the settling tank (5) is the nitrification circulating fluid (
6) is a series of processes in which returned sludge (7), surplus sludge (8), and treated water are connected by arrow lines. Raw water (
Wastewater) W is led to the dephosphorization anaerobic tank (1) together with 7 parts of the sludge (return sludge (6)) separated in the settling tank (4),
The sludge is anaerobically stirred in this tank, and the phosphorus in the dirt and mud is released into the liquid by the power of bacteria in the returned sludge. Seven parts of the organic matter in the raw wastewater is also decomposed anaerobically. Next, the treated liquid is led to the aerobic tank 1 for denitrification in (2), and at the same time, 7 parts of the liquid treated in the aerobic tank (3) is also sent to the nitrification cycle 3.
11 e (5) and is circulated to the denitrification anaerobic tank (2). In this denitrification anaerobic tank (2), nitrite nitrogen (N
O2−) Nitrate nitrogen (N O”) causes a denitrification reaction using organic matter in the raw wastewater as a hydrogen donor, becoming a nitrogen gun, and nitrogen is removed at this stage. For denitrification in (2) &lI
The liquid treated in the aerobic tank is then led to the aerobic tank (3), where air is actively sent through an aeration device etc. to prevent the oxidation of organic matter in the liquid. -C'OD decreases, and ammonia nitrogen is oxidized to nitrate nitrogen or nitrite nitrogen.

On the other hand, the phosphorus released from the sludge in the air tank for dephosphorization in (1) and the phosphorus in the raw wastewater are excessively ingested into the sludge under aerobic conditions. Thus, phosphorus is absorbed and removed through the sludge. The treated liquid is then led to a sedimentation tank (4)K, where it is divided into sewage 1 and treated water (8), and 7 parts of the sludge are sent as return sludge (6) to the dephosphorization peripheral air tank (1). , the remainder is treated as surplus sludge (7) containing phosphorus.

In this way, treated water (8) from which phosphorus and nitrogen are removed and whose BOD is reduced is obtained.

What is important in this process is that it is more effective to release phosphorus from the sludge in the anaerobic tank for dephosphorization if the temperature of the organic components in the raw wastewater is higher.

The more phosphorus is released, the more excess phosphorus will be ingested into the sludge in the aerobic tank.

, 2) In an anaerobic tank for denitrification, the presence of an appropriate amount of organic matter is essential as a hydrogen donor for the denitrification tank.

3) Under anaerobic conditions, the coexistence of nitrate and nitrite nitrogen suppresses the release of phosphorus.

t) If the sludge in the system remains in an anaerobic state for a long time, the sludge will rot and its activity will decrease.

Considering the above and considering the previous process, if the dephosphorization anaerobic tank (2) is placed after the dephosphorization anaerobic tank (1), organic matter will decompose even in the dephosphorization anaerobic tank, so denitrification will occur. The drawback is that the denitrification reaction can be carried out in an insufficient manner due to the lack of organic matter as a hydrogen donor.

Furthermore, if dephosphorization and denitrification are performed in series 1c, denitrification and dephosphorization will inevitably be affected by the spacing between the tiles, resulting in a drawback that the overall problem cannot be avoided. Furthermore, if dephosphorization and denitrification are carried out in series, the residence time of sludge in the anaerobic system will inevitably become longer.
Decay of the sludge and decrease in activity occur.

Also, if the LFI air tank for dephosphorization and the anaerobic tank for denitrification are reversed for treatment, there will be a lack of organic matter in the anaerobic tank for dephosphorization, and the effects of residual nitrate nitrogen and nitrite nitrogen will be reduced. The release of phosphorus in the anaerobic i75 for dephosphorization is insufficient and causes a great deal of inconvenience.

(Problems to be Solved by the Invention) The present invention aims to improve some of the drawbacks of the conventional methods as described in the previous section, and at the same time provides a new processing method that takes advantage of the characteristics of the conventional methods. .

In other words, the present invention provides a method for treating wastewater containing BOD, nitrogen and phosphorus components through anaerobic and aerobic processes.
The system is divided into a de-O-phosphorus sickle tank and a denitrification anaerobic tank, each of which is installed in parallel.The former is used to return sludge, and the latter is treated with nitrification circulating fluid, and then this treated water is The sludge is combined and treated in an aerobic tank, and then separated into sludge and treated water in a settling tank. At the same time, 7 parts of the sludge is returned to the anaerobic tank for dephosphorization, and the sludge is treated in the aerobic tank. The wastewater treatment method is characterized in that 7 parts of the nitrification circulating liquid is circulated to the denitrification anaerobic tank.

The difference from the conventional method is that the anaerobic tank for dephosphorization (1) and the anaerobic tank for denitrification (2) are not installed in series, but are installed in parallel. Other points are the same as the conventional method.

The ratio is shown in a flow sheet as shown in Figure 1.

The raw water W is divided into two systems, one is an anaerobic tank for dephosphorization (1
) and others are introduced into the denitrification anaerobic tank (2). At the same time, the return sludge (6) generated from the latter stage is added to the former, and the nitrification circulating liquid (5), which is 7 parts of the treated liquid from the aerobic tank (3) in the latter stage, is added to the latter, and the dephosphorization and denitrification reactions are carried out. They are processed without being influenced by each other.

The reaction in the anaerobic tank is the same as the conventional method, but since the organic matter in the raw water directly enters each tank, the amount can be easily adjusted by 1C, which overcomes the drawbacks of the conventional method. It's solved. In the dephosphorization peripheral air tank (1), the presence of sufficient organic matter return sludge facilitates the release of phosphorus from the sludge. In the denitrification anaerobic tank (2), denitrification of nitrate nitrogen and nitrite nitrogen occurs by circulating the nitrification circulating fluid (5) and using sufficient organic matter as a hydrogen donor. After the reaction, the famous monk's processing liquid is combined into the aerobic tank (1 to (3), where U1
As with the conventional method, under aerobic conditions through air aeration, BoD is reduced.Ammonia is oxidized to nitrate nitrogen and nitrite nitrogen, while phosphorus and raw materials released in the anaerobic tank for dephosphorization in (1) are reduced. 12. Phosphorus content in wastewater. ．． - Excessive intake into sludge occurs. Here, 7 parts of the processing liquid is the nitrification circulating liquid (
5) is circulated to the denitrification anaerobic tank (2). The other treated liquid is sent to the settling tank (4) and divided into sludge and treated water (8). Seven parts of the sludge is sent as return sludge (6) to the dephosphorization anaerobic tank, and the rest is surplus sludge (7). ), dried and used as fertilizer, etc.The present invention solves the drawback of the conventional method mentioned earlier/) by installing each anaerobic tank in parallel. By doing so, the raw water can be distributed independently to the famous monks, so this issue has been resolved.

-2) If the dephosphorization anaerobic tank (1) and the denitrification anaerobic tank (2) are connected in series, the treated liquid in the dephosphorization anaerobic tank (1) will enter the denitrification anaerobic tank (2), so they can be interchanged. Although it is easy to be influenced by various things,
If you do it in parallel, you won't have to worry about this at all.

(3) Furthermore, since the residence time of wastewater in an anaerobic state can be adjusted independently if they are arranged in parallel, it is possible to prevent a decrease in the decomposition activity of the sludge.

0 effect) The present invention applies the following principle to remove BOD, nitrogen, and phosphorus components from wastewater, and rationally devises the arrangement of the device.

/) Reduction in BOD This was achieved using the conventional activated sludge method in an aerobic tank.

, 2) Removal of phosphorus In the present invention, phosphorus is released from the sludge in an anaerobic state in the presence of return sludge and organic matter, and then in an aerobic state, 1, when excessive phosphorus is taken into the sludge. Using this principle, phosphorus was absorbed into the excess sludge and removed.

3) Removal of nitrogen Ammonia is oxidized to nitrate nitrogen and nitrite nitrogen in an aerobic tank, and this is circulated to an anaerobic tank for denitrification, where organic matter is denitrified as hydrogen (It donor). I did it.

4t) The anaerobic tank for dephosphorization and the anaerobic tank for denitrification are arranged in parallel so that each hK raw wastewater is introduced, and the λ reactions are performed independently so that they do not interfere with each other, and this treated solution is Table 1 shows the results of wastewater treatment using a device similar to Step 1 in Figure 1.

Conditions: Synthetic sewage prepared in advance as wastewater 2 Processing amount
301/D - Anaerobic tank for denitrification in the tank io't/D Anaerobic tank for denitrification! θ
t/D 3 tank capacity Anaerobic tanks each have 31 aerobic tanks gt Long circulation/return amount Nitrification liquid circulation amount 301/D Return sludge amount /' Ot / D j Water temperature of each auxiliary tank Jt℃ Table 7 Effects of the invention) / ) Unlike conventional anaerobic and aerobic continuous methods, the present invention uses an anaerobic tank for dephosphorization and denitrification! By arranging the tanks in parallel and allowing raw water to be introduced directly into each tank, dephosphorization and denitrification can proceed efficiently in each tank without interference from the others.

, 2) As a result, even with the same capacity as the conventional method, the overall removal rate of phosphorus and nitrogen could be improved.

3) Unlike the conventional series method, anaerobic tanks are arranged in parallel, so
Since the residence time of sludge can be adjusted in each anaerobic tank, the residence time in an anaerobic state is shortened, preventing sludge from rotting and decreasing its activity.

[Brief explanation of the drawing]

Figure 1 shows an example of a flow sheet for the method of the present invention. Figure 2 shows seven examples of a flow sheet for a conventional method. Explanation of the symbols representing the main parts (1) Anaerobic tank for dephosphorization (2) Anaerobic tank for denitrification (3) Aerobic tank (4) Sedimentation tank (5) Nitrification circulating fluid (6) Returned sludge (7) Excess sludge (8) Treated water

Claims (1)

[Claims] In a method of treating wastewater containing BOD, nitrogen, and phosphorus components through anaerobic and aerobic processes, the wastewater is divided into two systems, each of which is divided into an anaerobic tank for dephosphorization and an anaerobic tank for denitrification, which are installed in parallel. In the former case, the sludge is returned.In the latter case, the treated water is treated with the nitrification circulating fluid.The treated water is combined, treated in an aerobic tank, and then led to a settling tank, where it is separated into sludge and treated water, and at the same time, a part of the sludge is A wastewater treatment method characterized in that a part of the liquid treated in the one-way aerobic tank is returned to the denitrification anaerobic tank as a nitrification circulation liquid and circulated to the denitrification anaerobic tank.