JPH0210718B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an oxidation pond type wastewater treatment device. More specifically, the present invention relates to an oxidation pond type wastewater treatment device filled with a reticulated contact base material. (Prior Art) Conventionally, the oxidation pond method has been implemented in general wastewater treatment, etc. This method uses paddle-type or rotor-type aeration to forcefully circulate pond wastewater and perform biological purification treatment using the action of bacteria and algae. Generally, the aeration time is 24 hours or more, and MLSS is 3000~5000mg/,
It is carried out under treatment conditions such as a BOD load of 0.05 to 0.06 Kg/Kg/HLSS/day and a return sludge ratio of 50 to 150%.The advantages include easy operation management and a small amount of surplus sludge. It has also been pointed out that it is suitable even when load fluctuations are quite large. (Problem to be Solved by the Invention) However, even if load fluctuations over a short period of time such as one day can be dealt with almost satisfactorily, load fluctuations over a long period of time such as a week or between seasons cannot be adequately dealt with. There were drawbacks that could not be addressed. In other words, if relatively large load fluctuations occur over a long period of time, suspended solids will disintegrate and no longer settle when the load becomes low, resulting in a significant drop in processing capacity when the load changes from low to high. The problem was that it could not be adequately addressed. The present invention was invented in view of these conventional drawbacks, and its purpose is not only to deal with load fluctuations over a short period of time such as one day, but also to deal with load fluctuations over a week or season. An object of the present invention is to provide an oxidation pond type wastewater treatment device that can sufficiently cope with load fluctuations over a long period of time and can always perform a good purification process. (Means for Solving the Problems) An oxidation pond type wastewater treatment device according to the present invention that achieves this object has a network-like contact base material group filled in the oxidation pond approximately parallel to the circulating water flow, and the following formula: It is characterized in that the required filling rate (X) is 10% to 30%. X=MV/Pv×100 Here, Mv is the number of sheets of the above-mentioned reticulated contact base material whose vertical dimension is l ₁ and horizontal dimension is l ₂ at equal intervals in the range of 50 mm to 200 mm over the entire length of the framework structure. When the width dimension of the base material unit that has been installed is l ₃ and the number of the base material units filled into the oxidation pond is n,
Indicates the apparent filling total volume (m ³ ) of the reticulated contact substrate determined by l ₁ ×l ₂ ×l ₃ ×n, and Pv indicates the total volume (m ³ ) of the oxidation pond. Hereinafter, the present invention will be specifically explained based on Examples. In FIG. 1, an oxidation pond 1 with the same volume
Rotors 2a and 2b are respectively disposed in a, 1b and 1c, and the wastewater supplied from the first water division tank 3 to each pond is forcedly circulated in the direction of the arrow in the figure by these rotors 2a and 2b so that it can be aerated. It is also provided so that wastewater can be sent from each pond to the second water division tank 5 via the pump 4. Each of the ponds 1a, 1b, and 1c is filled with a group of reticular contact base materials such that the filling positions are different from each other while maintaining the same filling rate, which will be described later. That is, in the oxidation pond 1a, as shown in FIG.
Three sets of base material units 8, which are fixed and formed into a unit, are filled in the linear water channel A on the rotor 2a side, and two sets are filled in the linear water channel B on the rotor 2b side. In addition, in the oxidation pond 1b, two sets of straight water channels A on the rotor 2a side are filled, and three sets of straight water channels B on the rotor 2b side are filled. Furthermore, in the oxidation pond 1c, one set is filled in each of the corner waterways C and D, one set is filled in the straight waterway A on the rotor 2a side, and one set is filled in the straight waterway A on the rotor 2a side.
Two sets are filled in straight water channel B on the b side. The base material units 8 filled in these ponds 1a, 1b, 1c are filled so that they are almost submerged in the water, and the reticulated contact base material 6 is filled almost parallel to the circulating water flow. , 1b, and 1c are set to one value selected from the range of 10% to 30%. The filling rate here is expressed as a percentage of the ratio of the total volume of the oxidation pond to the total apparent filling volume of the six groups of reticular contact base materials.For example, if the total volume of the oxidation pond 1a is Pv
(m ³ ), and the apparent total filling volume of the six groups of reticular contact base materials filled in this pond 1a is Mv (m ³ ), then the filling rate (X) is calculated as 100Mv/Pv,
Mv has the vertical dimension l ₁ shown in Fig. 2,
Multiple pieces of mesh contact base material 6 with horizontal dimension _l2 from 50mm
Frame structure 7 is placed at equal intervals with a pitch P within a range of 200 mm.
If the width dimension of the base unit 8 installed over the entire length is l ₃ , then the apparent total filling volume (mv) of the base unit 8 alone, which is determined by l ₁ × l ₂ × l ₃ , ^is ,
It is obtained by multiplying the solid number (n) filled into the oxidation pond 1a, that is, in this example, n=5. The present invention thus provides oxidation ponds 1a, 1b, and 1c.
It is essential to fill the reticulated contact base material 6 so as to obtain a filling rate in the range of 10% to 30%, and as a result, even in the oxidation pond, the reticulated contact base material 6 is always well maintained with biofilm. can be attached,
Furthermore, unlike the suspended sludge (MLSS) used in conventional methods, the biofilm has a property of high coagulation and does not disintegrate, so it can sufficiently cope with large load fluctuations and always provides stable treatment. It is possible. That is, it is treated in oxidation ponds 1a, 1b, 1c,
The sewage sent to the second water division tank 5 via the pump 4 is sent from there to the settling tank 9, where excess biofilm-based sludge is separated well, and then this separated sludge is sent to the oxidation tank 1.
A, 1b, 1c are returned to floating sludge, but by mixing this sludge with the biofilm sludge in the pond, sludge with relatively high settling properties can be obtained even under low load conditions. Therefore, stable processing can be performed even with wide load fluctuations. Note that even if a contact base material other than the reticulated contact base material, such as a general plate contact base material, is filled, sufficient biofilm cannot be attached, so that the effects of the present invention as described above cannot be obtained. In addition, the fixing pitch (P) of the mesh contact base material was set to 50 mm.
If it is less than 200 mm, the resistance will become large at the same time as it becomes anaerobic, and if it is more than 200 mm, the amount of biofilm will be insufficient, so it is necessary to keep it in the range of 50 mm to 200 mm. In the present invention, it is preferable to fill the reticulated contact base material 6 so as to be parallel to the circulating water flow in the pond. If it is not filled in this way, the circulating flow rate by the rotors 2a and 2b will be reduced and the contact between the biofilm and the wastewater will be reduced. The quality of the sludge deteriorates, the supply of dissolved oxygen becomes insufficient, and the returned sludge does not become floating sludge but settles in the pond, making it difficult to perform good treatment. Regarding the filling position, it is preferable to fill only the straight waterways A and B as in the oxidation ponds 1a and 1b rather than filling the corner waterways C and D as in the oxidation pond 1c. Also, if the filling rate (X) is set outside the range of 10% to 30%, it will be difficult to perform good processing. In other words, if the amount is less than 10%, sufficient biofilm amount cannot be obtained, and 30%
% or more, the circulation flow rate decreases significantly and, therefore, it becomes difficult to achieve good treatment. (Example) Artificial sewage was circulated in an oxidation pond 1c in which straight waterways A and B and corner waterways C and D were filled with base material units 8, at a flow rate v of 0.3 m/s to 2 m/s, during aeration (sewage residence time ) for 24 hours, the fixing pitch (P) of the synthetic resin net contact base material 6 in the base unit 8 is 50 mm to 200 mm, the mesh size of the base material 6 is 5 mm to 20 mm, and the wire diameter is 1 mm to 3
mm, and when the load is repeatedly varied such as 10 mg/day on Monday, Tuesday, Wednesday, and Thursday, 30 mg/day on Friday, and 50 mg/day on Saturday and Sunday, the filling rate is The relationship between (X) and treated water was as shown in Table 1.

[Table] Furthermore, when the entire set of base unit 8 was removed from the oxidation pond 1c and the same type of sewage was treated with the same circulation flow rate, aeration time, and load fluctuation, the treated water quality was 10 mg/~25 mg/ . As is clear from this, according to the present invention, even if the load fluctuates widely, it always remains at the specified value (20mg/
) can be processed as follows. In order to further confirm that such excellent effects can be obtained, two methods were used: a conventional method in which 960 mg of MLSS was allowed to settle naturally and concentrated 10 times using only suspended sludge, and a method in which MLSS of 960 mg/ml was concentrated 10 times using suspended sludge and returned suspended sludge in a pond as in the present invention. By mixing sludge with biofilm sludge of
A comparative study was conducted with the case where 985 mg of MLSS was concentrated 10 times, and it was found that the former took about 1 hour, while the latter took about 15 minutes. (Effect of the invention) As described above, according to the present invention, compared to the conventional method, the
Since the sludge can be concentrated in 4 hours, the separated sludge 10 can be returned from the settling tank 9 to the oxidation tanks 1a, 1b, and 1c in a short cycle, increasing the amount of sludge, which not only reduces the load but also increases the amount of separated sludge. In particular, it can perform good processing even under high loads, and can always perform good processing regardless of short-term or long-term load fluctuations. In addition, in the present invention, when the load is 0.02Kg/ ^m3・day to 0.06Kg/ ^m3・day, the filling rate (X)
15% to 20%, and 0.05Kg/m ³・day to 0.01Kg/
In the case of m ³ days, it is preferably 20% to 30%.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an oxidation pond type wastewater treatment apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a base material unit 8. 1a, 1b, 1c: oxidation pond, 6: reticulated contact base material.

Claims (1)

[Claims] 1. A system characterized by filling an oxidation pond with a group of reticular contact base materials substantially parallel to the circulating water flow, and setting the filling rate (X) determined by the following formula to 10% to 30%. Oxidation pond type wastewater treatment equipment. X=Mv/Pv×100 Here, Mv is a plurality of sheets of the above-mentioned reticulated contact base material having a vertical dimension of l ₁ and a horizontal dimension of l ₂ , arranged at equal intervals in the range of 50 mm to 200 mm over the entire length of the framework structure. When the width dimension of the base material unit that has been installed is l ₃ and the number of base material units filled into the oxidation pond is n, then l ₁
Indicates the total apparent filling volume (m ³ ) of the reticulated contact base material determined by ×l ₂ ×l ₃ ×n, and Pv indicates the total volume (m ³ ) of the oxidation pond.