JPH03123687A - Biological contact filter apparatus - Google Patents

Abstract

PURPOSE:To perform treatment from a stage of an acclimation period even when the moldy smell decompositing bacterial bonded to an activated carbon filter material are not yet acclimatized by packing a filter tower with columnar granular activated carbon having a specific diameter as a filter bed. CONSTITUTION:In a biological contact filter apparatus wherein bacteria are held to the filtered in a filter tower formed by packing the filter tower with a filter material 3 and raw water is passed through the filter bed. The filter tower is packed with columnar granular activated carbon having a diameter (d) of 2.0-4.0mm as a filter bed. Herein, the granular shape of activated carbon is not a rod shape low in strength but means a shape whose length L to the diameter (d) is about 0.5-2.0. The filter bed constituted of the filter material 3 is low in the trapping ratio of suspended matter and a moldy smell is adsorbed by the properties of the activated carbon itself of the filter material during about two months at the beginning of operation until moldy smell decomposing bacteria are acclimatized.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention uses river water as raw water and uses it in combination with a coagulation sedimentation device, a filtration device, etc. to treat the raw water and make it into clean water. This invention relates to a biological contact filtration device that removes odor and ammonia nitrogen.

<Conventional technology> -COD components and chromaticity components are adsorbed from secondary treated water obtained by treating organic sewage such as sewage and human waste using the activated sludge method, and these adsorbed components are decomposed and removed by microorganisms. Therefore, a biological contact filtration device in which a column is filled with granular or crushed bone char or activated carbon having a particle size of 3 to 15) is known from JP-A-57-1, No. 0382.

<Problems to be Solved by the Invention> Since the above-mentioned conventional device removes COD components and pigment components from secondary treated water such as sewage and human waste, the bone char and activated carbon used as filter media have a particle size of 3. ~15 mm appears to be preferred.

However, when the raw water is river water and a biological contact filtration device is used to remove mold odor and ammonia nitrogen from the water as in the present invention, if the capture rate of turbidity by filtration is high, differential pressure (pressure loss) will occur. The smell builds up quickly (it requires frequent cleaning, and since mold odor is removed by the direct biodegradation action of the microorganisms retained in the filter layer, it takes about half a month to two months for the microorganisms to get used to it). There are other problems, such as insufficient treatment being carried out during the period, and rapid fluctuations in the load due to the rapid increase in the ammonia nitrogen concentration in the raw water.

Therefore, the turbidity capture rate of the filter layer is not very high.
Musty odor can be completely treated even if the retained microorganisms are unaccustomed, and even if the ammonia nitrogen concentration in the raw water increases, it always retains enough microorganisms to treat it7. The material and dimensions of the filter medium must be selected to meet the above conditions.

<Means for Solving the Problems> Therefore, the present invention provides a biological contact filtration device in which a filter layer filled with a filter material is provided in a filter tower, microorganisms are retained in the filter layer, and raw water is passed through the filter layer. It is characterized by being filled with cylindrical granular activated carbon having a diameter of 2.0 to 4.0 mm.

<Example> In the illustrated example, 1 is a filter tower, and 2 is a filter bed having a bed height of about 0.5 to 4.0 m, which is constructed by filling the tower with a filter material.

The filtration tower can be installed either before or after the flocculation treatment equipment, but in order to prevent turbidity in the raw water and microorganisms such as bacteria from contaminating the final treated water, it is installed before the flocculation treatment equipment. It is preferable to install it.

The water flow direction in the sublayer 2 may be a downward flow method in which raw water is supplied to the filtration tower from above, or an upward flow method in which raw water is supplied to the filtration tower from below as shown in the figure. The upward flow method is preferable because it causes less increase in differential pressure due to trapping. In the case of the upward flow method, the water flow rate is determined so that the flow rate does not cause the filter medium to flow while air or oxygen gas is blown into the treated water to the extent that dissolved oxygen can be detected.

Now, the filter material for forming the filter layer 2 has attached mold odor-degrading bacteria that directly removes the mold odor in raw water through biodegradation, and nitrifying bacteria that oxidizes and removes ammonia nitrogen in raw water. The material is activated carbon, which uses its own adsorption properties to adsorb and remove mold odors in raw water until mold odor-degrading bacteria become accustomed to them.

If the size is large, the surface area is small (and the amount of nitrifying bacteria that oxidizes the ammonia nitrogen in raw water will be less attached), and conversely, if the size is small, the surface area will increase, but the turbidity trapping function will be reduced. and the differential pressure rises faster,
As a result, the frequency of washing increases, the amount of washing water increases, equipment becomes oversized, and the water recovery rate decreases, which increases operating costs. In addition to these considerations, considering the problem of strength so that there is less damage during cleaning, the activated filter medium 3 is made into cylindrical granules with a diameter d of 2.0 to 4.0 + nm as shown in Fig. 2. . In this case, granular means that the material is not rod-like, which has low strength, but has a length (5) of about 0.5 to 2.0 relative to the diameter.

The filter layer 2 composed of this filter medium 3 has a low capture rate of suspended solids (also, during the first two months of operation until the mold odor-degrading bacteria become accustomed to it, the activated carbon itself in the filter medium does not suppress the mold odor). Furthermore, since the filter medium has a moderately large surface area, even if the level of ammonia nitrogen in the raw water increases rapidly, it will attract the necessary amount of nitrifying bacteria to oxidize and remove it. then i
l! hold in m.

Fill a column with a diameter of 30mm and a height of 400mm with 200ml of various filter media to create a column with a diameter of 30mm and a height of 283m.
After aerating river water with air as raw water, ammonia and a musty-smelling substance (2-methylisoborneol) were added to adjust the concentration, and this was applied to the column at a flow rate of 2427 days (SV・Ammonia decomposition was carried out for 60 days while washing the river water by flowing it upward at a flow rate of 5.0'/hour) at a flow rate of the filter medium once every 1 to 2 days. Therefore, after acclimatization, the raw water was continuously passed through in an upward flow without washing, resulting in an increase in pressure loss and
When the treatment status of ammonia and 2-methylisoborneol was investigated, the results shown in the table below were obtained. The filter material packed in the column is as follows.

In addition, during the acclimatization process, mold-smelling substances are not detected in the treated water of the activated carbon filter from the start of acclimatization, and ammonia is sufficiently treated after 10 to 15 days after the start of acclimatization, and stable treated water is obtained thereafter. Ta.

The mold odor (methyl isoborneol) can be removed regardless of the size and shape of the activated carbon, and odorless treated water can be obtained. Also, when it comes to removing ammonium nitrogen, the smaller the diameter, the more effective it is.
There are differences depending on the shape; for cylindrical shapes, the particle diameter is preferably 3 mm or less, and for crushed particles, the particle diameter is 1 mm or less. Sand has the same performance as crushed activated carbon.

FIG. 3 shows the relationship between the increase in differential pressure and the average particle shape in the removal of ammonia nitrogen. As is clear from this, in the case of crushed activated carbon, the removal of ammonia nitrogen and the rise in differential pressure show the same tendency, whereas in the case of cylindrical activated carbon, the ammonia It has a good nitrogen removal effect, and there is no increase in differential pressure (both are satisfied.

<Effects of the Invention> According to the present invention, even if the mold odor-degrading bacteria attached to the activated carbon filter medium are unacclimated, the activated carbon adsorbs the mold odor in the incoming raw water, so treatment can be carried out during the acclimatization period. Further, even if the concentration of ammonia nitrogen in the inflow raw water changes to a high concentration, stable treated water with an allowable concentration of ammonia nitrogen of 0.5 mg/l can be obtained as raw water for tap water.

In addition, since the amount of washing waste water is small, the processing equipment can be made smaller, and since the filter medium is not crushed during washing, there is less loss due to fragments flowing out together with the washing waste water.

Furthermore, the surfactant in the incoming raw water can also be removed by activated carbon (adsorption and biodegradation action on the activated carbon), and troubles caused by foaming can also be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the biological contact filtration device of the present invention, FIG. 2 is a perspective view of the filter medium, and FIG. 3 is a diagram showing the diameter of the filter medium.
It is a graph showing the relationship between increase in differential pressure and removal of ammonia nitrogen. In the figure, 1 is a filter tower, 2 is a partial layer, and 4 is a filter medium.

Claims (1)

[Scope of Claims] A biological contact filtration device in which raw water is passed through a filtration layer filled with a filter material in a filtration tower, in which microorganisms are retained, and a cylindrical granular material with a diameter of 2.0 to 4.0 mm is used as the filtration layer. A biological contact filtration device characterized by being filled with activated carbon.