JPH0295490A - Method and apparatus for filtering sewage - Google Patents

Abstract

PURPOSE:To considerably reduce the amts. of nitrogen and phosphorus in sewage as well as the amts. of fine particles and microorganisms by passing the sewage through a bed of granules of a porous mineral such as cristobalite to remove pollutants in the sewage as a sediment or flocks. CONSTITUTION:A direct filtration type filtering apparatus 22 is composed essentially of a cristobalite vessel 23 as a first filtering vessel and a sludge filtering vessel 25 as a second vessel. The vessel 23 is packed with cristobalite granules 3 of about 5-20mm diameter and a pipe 18 for back washing is laid near the bottom of the vessel 23. Sewage (raw water) is introduced into the vessel 23 from an inflow pipe 9 and pollutants in the sewage are captured as a sediment or flocks in the bed of the cristobalite granules 3. The sewage purified through the bed is sent to the vessel 25 from an outflow pipe 10. In the vessel 25, sludge is separated and the resulting filtered water is discharged as purified water from the apparatus 22 through an outflow pipe 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for removing pollutants from wastewater by filtering or adsorbing them using granular materials of porous minerals such as cristobalite.

[Prior Art] Conventionally, filtration tanks used in sewage treatment, agricultural wastewater treatment, etc. are usually sand filtration tanks for tertiary treatment, floc separation after tertiary treatment, or calcium separation after calcium phosphate crystallization. It is used.

Sand filtration has the advantage of simple tank structure and operation and low running costs, but it can only filter out particles of several tens to hundreds of micrometers or more, and it is difficult to filter out fine particles smaller than that. Therefore, in the tertiary treatment of sewage, etc., the water may be coagulated and precipitated using a coagulant, and then passed through a sand filter tank. In the crystallization method, the precipitated material is separated by sand filtration. On the other hand, agricultural wastewater and J! : Field drainage contains a lot of fertilizer components, feed residue, dissolved organic and inorganic substances, and contains a considerable amount of algae and bacteria. However, the concentration of pollutants in these wastewaters is considerably lower than that in sewage, etc., and they are released in large quantities.
Due to cost considerations, it is generally discharged as is without any treatment.

In addition, domestic gray water (bath, laundry, cooking) also contains a considerable amount of food residue, detergent, and other dissolved organic and inorganic substances.
At most, large floating objects such as SS and sediments formed by standing still are removed, and the water is discharged as is.

[Problems to be Solved by the Invention] However, there are a considerable amount of pollutants that cannot be filtered through sand in the secondary treatment water of sewage. Nutrient salts such as phosphorus and nitrogen correspond to this. In addition, the coagulation-sedimentation method uses chemicals, which requires high running costs and laborious management.
Because the flocculant is used, the amount of precipitate is also large (and its treatment is difficult).

On the other hand, even if agricultural wastewater and domestic gray water are filtered with sand, not only the nitrogen and phosphorus content, but also most of the particulates and microorganisms are released as they are. Therefore, even if the concentration of pollutants is low, large amounts are released, resulting in considerable pollution of rivers in the basin. However, it costs a huge amount of money to precipitate or coagulate pollutants in various types of wastewater, and it is currently almost impossible to do so when considering management and treatment of filtered materials.

[Means for Solving the Problems] In view of the above-mentioned current situation, the present inventors have completed the sewage purification method and device of the present invention as a result of intensive research, and its characteristics are as follows. Wastewater is passed through a treatment tank (J*) filled with porous mineral granules such as Cristobalite to remove pollutants in the wastewater that cannot be separated by sand filtration alone, or that cannot be efficiently flocculated in the past. It adsorbs and traps pollutants and promotes sedimentation to create sludge that can be filtered through sand.
This is separated using a sludge filter tank filled with sand or the like. Therefore, sand filtration can be performed efficiently and filtration performance is improved.

That is, the present inventor focused on the adsorption effect of porous minerals for the removal of pollutants from wastewater, and added various porous natural minerals (sepiolai I, zeolite, Cristobalite, Kiryu sand) and porous artificial minerals to wastewater. (perlite) granules (5~
20 mmφ) was immersed in filtration, and granular materials such as cristobalite and theolide showed good purification ability. The experimental results for both of these are shown in Figure 1 (al~(dl), and as can be seen from the figure, stable values were shown for 60 to 120 minutes. Measurements were taken every 30 minutes.

Therefore, the present inventors continued experiments and arrived at the present invention.

The reason why Cristobalite showed good purification ability is probably due to its extremely large surface area compared to other minerals. That is, natural cristobalite (cristobalite)
is a mineral whose main component is silicon dioxide, which was created by depositing fossilized diatomaceous earth or depositing magma. And since the particles have ultra-fine pores of 10 to 30 ~ 30 μm in length and width, the surface area of the particles is 130n per gram. It also extends to the degree.

Therefore, it exhibits an excellent effect in adsorbing and trapping fine insoluble particles or organic/inorganic pollutant particles in a colloidal state (a mixture of sol and gel) on the surface, and in attaching nitrogen species, bacteria, and plankton. It seems that it was Since it is easy for bacteria and plankton to settle on the surface, the phosphorus content (mainly phosphate ions) that is used as a medium is removed along with the removal of bacteria and plankton, thereby enhancing the dephosphorization performance of cristobalite. As a result, organic N
etc. are also successfully removed, and the BOD is greatly reduced.

The effects that occur in these Cristobal stones are persistent, and the inventors conducted follow-up tests for more than two months, but no changes were observed in their behavior. It is thought that this is what was shown.

However, in the case of sewage, the COD may hardly decrease or may even slightly increase. In such a case, in order to reduce COD, it is desirable to add the following ideas to the structure of the filtration device. That is, the bacteria-containing water after biological treatment (aerobic treatment) first removes SS at the beginning of the filtration device, and then decomposes COD and BOD using the Cristobal stone layer, which is excellent as a grouper carrier. At this time, it is necessary to stimulate the aerobic bacteria, so some aeration is required. In addition, although the bacteria settle on Cristobalite well, due to the small pores mentioned above, the flocs grown on the surface tend to separate at t11, and some of them peel off and settle.

At the final stage of the device, a filtration tank (layer) is provided to capture sludge consisting of exfoliated flocs and other precipitates. The sludge filter tank is filled with sand (river sand) or a mixture of sand and balas. Alternatively, a layer of small grains of cristobalite may be provided on top of these layers. This is because the Chrismy Pal stone particles are light and always come to the top during backwashing, so if large sludge is captured there, cleaning by backwashing can be easily performed. If there is a biological treatment tank in the previous process, the sludge should be returned to the previous process along with the backwash water. In this way, there is no need to separately install a settling tank for sludge extraction.

Furthermore, it is recommended to diffuse air into the Cristobalite formation to remove soluble COD. If you do this, the COD removal rate of wastewater will be 60-80% after soaking for about 1-2 hours.
In some cases, it may be possible to reduce the severity.

On the other hand, zeolite crystals are also several to several hundred μm in size? It has many lI pores and adsorbs SS, ammonia nitrogen, heavy metals, etc. well. However, its surface area is only a fraction of that of Cristobalite, and its ability to adsorb and trap fine particles and bacteria is inferior. However, zeolite has excellent ion absorption ability,
In particular, the adsorption capacity for ammonia nitrogen is more than ten times that of cristobalite.

Therefore, before the Cristobal stone layer (a layer of granular Cristobal stone), there is a zeolite layer (a layer of zeolite granules).
When placed, N1 (4, etc.) is adsorbed.

In this way, the combination of the zeolite layer and the Cristobal stone layer can better purify wastewater.

However, when zeolite becomes saturated, it requires regeneration treatment, so it must be replaced regularly.

Incidentally, the Cristobal stone grains and the zeolite grains may be filled in separate tanks, or they may be mixed and filled in one tank. In this case, Cristobal stone grains (apparent specific gravity of approximately 1)
Since it is lighter than zeolite particles (apparent specific gravity of about 1.5), it can be separated by backwashing or the like. Therefore, it is easy to replace only the zeolite grains, and if you want to pass wastewater through the zeolite grains first, it is better to pass the water from below.

To summarize the above, the filtration device of the present invention can be said to be a combination of a treatment tank and a sludge filtration tank, and the treatment tank may include a Cristobal stone tank, a zeolite tank, and a mixed tank thereof. It is also conceivable that a pretreatment tank filled with small-diameter Cristobal stone particles or sand (river sand) is provided in front of the treatment tank. This is done by filtering out SS and relatively large sludge, and then cleaning the surface tθ of the granules in the next zeolite tank or Cristobal stone tank.
It is used to prevent this, and may be filled relatively thinly.

Zeolite tanks and pretreatment tanks are used depending on the nature of the wastewater to be treated.

Note that crushed Cristobal stone grains and zeolite grains are usually used. Although the examples of the present invention are all crushed products, it is also possible to use crushed products that have been shaped or powder that has been hardened with a binder. The smaller the size of the granules, the larger the contact area with water, but considering the filtration efficiency, Tsutomi 1
Those with a diameter of about 50 mmφ, especially 5 to 20 mmφ are often used.

The pretreatment tank used is one with a size of 1 to 4 ml/φ. sand(
River sand) is used in a normal size (1 to 4 mmφ).

Next, the wastewater to be treated in the present invention is not particularly limited, but includes polluted water such as secondary treated sewage water, tertiary treated water, agricultural wastewater, aquaculture pond wastewater, domestic gray water, and other mixed wastewater. Preferably, it has a relatively low concentration of substances and also contains bacteria and plankton.

In addition, the γη turbid substances to be removed include fine organic and inorganic water-insoluble substances (SS), hydrophilic substances (part of /8 degradable substances), algae, bacteria, plankton, etc.
These are TP, TN, [30D components, etc. contained in small living things and the like. Additionally, caps may be effectively removed in combination with aeration.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Cristobalite granules (5 to 201IIIllφ) 3 or zeolite were added to the first filter medium tank 2 (horizontal cylinder type, capacity 2.5/cm) of the sewage filtration experimental device 1 shown in FIG. 2(a) as a filter medium. Filled with granular materials (5 to 20 mmφ) 4 (porosity is approximately 50%), using a metering pump 5 at a constant flow rate (flow rate 10 to 20 m1/min: equivalent to a residence time of 60 to 120 minutes).
Raw water (sewage and muddy water) was passed through. Reference numeral 6 is a raw water tank. The treated water from this filter medium tank 2 is supplied to a second filter medium tank (sludge filtration tank) 7 to separate and remove sludge and take out filtered water. The filter medium tank 7 is a folding type, and is 18c.
A layer of sand (river sand) with a thickness of about 8 m is laid down.

In addition, the code|symbol 9 is a raw water inflow pipe to a 1st filter medium tank, 10 is a treated water outflow pipe, and 11 is a filtrate water outflow pipe from a 2nd filter medium tank.

Regarding the filtered water and raw water obtained in this way, turbidity was measured for muddy water, and organic N and ammonia N were measured for sewage.
, phosphorus content (TP), and PH were measured. The measurement results are shown in Table-1. The turbidity was determined by (JIS, kaolin standard method).

K jM feeling N, ammonia! The 3N and phosphorus contents were measured according to the JIS-Ni method, and the pH was measured using a ρ11 meter (Model D2 manufactured by Denki Kagaku Co., Ltd.).

From Table 1, it can be seen that the large surface area of Cristobal stone was fully utilized for muddy water filtration. In addition, there is no significant difference between zeolite and cristobalite in terms of removal of organic N among sewage pollutants, but it is clear that zeolite is extremely superior in removing ammonia N. Regarding the phosphorus content, it can be seen that the removal ability of Chris (-palstone) is extremely (worried).

Example 2 Next, regarding the phosphorus content in agricultural pond water and fish pond water where 14 large algal blooms are occurring, we will examine two cases: 1) filtered through a zeolite layer, and 1) grease 1 after filtration, and 1) filtered through a pallite layer. The results are shown in Table 2.The experimental device 12 was constructed as follows: 1. As shown in FIG. The other parts are the same as in Figure 2 (al).

Incidentally, each of these raw waters was initially suction filtered using a Niekuribore filter (0.1 μm), but the filtration was extremely difficult. Although GF-F (approximately 5 μm) glass filter paper was used instead, phosphorus could hardly be removed. Filtration using Cristobal stone grains or zeolite (- grains) was performed after filtration with this filter.

These results indicate that phosphorus in water containing plankton and bacteria exists in a colloidal state using these microorganisms as a medium. Furthermore, it was found that these were efficiently filtered out by high-speed filtration using Cristobalite.

Furthermore, using the same device as in Example 1 (Fig. 2(a)), a filter medium tank 2 was prepared.
Table 3 shows the measurement results when algae and bacteria (coliform bacteria) in the agricultural pond water and fish pond water were removed using a sample filled with Cristobal stone particles 3. As you can see, the number of algae and bacteria has decreased dramatically, and the excellent filtration ability of Cristobal stone has become clear.

Example 3 Using water after tertiary treatment (coagulation and precipitation treatment with sulfuric acid band) at a sewage treatment plant as raw water, T-N and T- before and after treatment
FIG. 3 shows the results of continuous measurement of the P value over about two months. This experiment was conducted using the apparatus 14 shown in FIG. 2(C), by continuously passing raw water through the water for 24 hours (20 ml/min: residence time: 70 minutes), and measuring the filtered water once a day at a fixed time.

By the continuous flow of raw water, pollutants adhered to the surface of the grease l-palstone and formed flocs, which were peeled off as the flocs grew. Therefore, the garden material function was maintained by backwashing with air (1 to 2 minutes) and water for 2 to 5 minutes once a day. The same raw water was used for 1 to 4 days, and when it got old, new raw water was collected and used.

The treatment results showed that the average T-P was 2.34 ppm for raw water and 0.67 ppm for filtered water. Also, the average T-N is 12 ppm for raw water and 6.7 ppm for filtered water.
pm, indicating a stable filtration (purification) effect as shown in the figure.

The experimental device 14 includes a first filter medium tank (cylindrical shape: capacity 3°51)
2. Add Cristobal stone grains 3 (5 to 20 φ) as a filter material to 2.57! (50% porosity) and fill the same (cylindrical second filter medium tank (sludge filtration tank) 7 with a lower layer consisting of 15 cm of river sand 8 and ballast 15 and 3 cm of Chris [~ Pal stone grains (
It is equipped with an upper layer of 2 to 5 mmφ)3. The reason why the filter medium of the sludge filter tank 7 is made into two stages 7 is to trap most of the sludge with light Cristobal stone particles and to improve the separation of the sludge during backwashing.

Also, there is a backwash water outlet 16.17 at the top of each filter media tank 2.7.
, backwash pipes 18.1 that send air and water to various lower parts.
9 is placed. Reference numerals 20 and 21 refer to pumps for sending backwash water and air, and other reference numerals are the same as in FIG. 2(a).

Equipment example Next, the sewage filtration device of the present invention will be explained.

The device of the present invention is a sewage filtration device that has multiple functions taking into consideration the above points, and various configurations can be considered taking into account the installation location and the sewage to be treated.

The devices shown below are examples, and FIGS. 4 and 5 show a combination of a Cristobal stone tank as a treatment tank and a sludge filter tank. These devices have a simple structure and are suitable for treating wastewater that is low in pollutants, especially SS and ammonia nitrogen.

Figure 6 shows a treatment tank using a zeolite tank and a Cristobal tank, which are combined with a sludge filtration tank.
η Suitable for water treatment. Other examples of this type of equipment include the 4th type, which has a separate zeolite tank and Cristobal stone tank.
It is also possible to install a zeolite tank similar to the Cristobal stone tank shown in the figure. Alternatively, in the apparatus shown in FIGS. 4 and 5, a mixture of zeolite grains and Cristobalite grains may be used.

The apparatuses shown in FIGS. 7 and 8 are examples of devices further equipped with a pretreatment tank, and are suitable for treating wastewater containing relatively large amounts of turbidity.

Of course, the present invention is not limited to those illustrated.

The filtration device 22 shown in FIG. 4 is of a direct filtration type.
5-2011 with the first filter medium tank as Cristobal stone tank 23
The tank 23 is filled with Cristobal stone grains 3 of about 1111, and a backwashing pipe 18 is arranged near the bottom, and the bottom of the tank 23 is tapered and a sludge drain 24 is provided at the lowest depth. Backwashing is performed for several to several minutes using water, air, or a combination thereof, as appropriate or periodically (for example, once a day). Aeration may be performed using the backwash pipe 18. The second tank is a sludge filtration tank 25, and is a funnel-shaped tank filled with small Cristobal stone particles 3 of 2 to 5 mm diameter in the upper layer and sand 7 and ballast 15 in the lower layer, and a backwashing pipe 19 is arranged near the bottom. . The water after backwashing overflows from the backwash water outlet 17.

The sewage (raw water) sent from the inflow pipe 9 to the Cristobal stone tank 23 is purified by collecting pollutants as precipitates or flocs in the layer of Cristobal stone particles, and is then sent from the outflow pipe 10 to the second tank for sludge filtration. The liquid is sent to tank 25. Here, the sludge is separated and discharged out of the system from the filtered water outflow pipe 11 as purified effluent water.

Fig. 5 shows a drum-shaped filtering device 26, in which the first tank, the Cristobal stone tank 23, is a rotating tram body, and approximately half of the tram is filled with slightly larger granules of listal stone (5 to 50 mmφ) 3. . Since the flocs are peeled off by the rotation of the Cristobal stone grains, the backwashing pipe 18 is not necessary.

Other structures are the same as in the previous example.

FIG. 6 shows a cartridge type filtration device 27 in which a first filter medium tank is a cartridge tank 28, and a large number of cartridges 29 are housed in the tank 28. This cartridge 29 is filled with granular materials 3 of about 2 to 2 b pieces of Cristobalite. Some of the cartridges 29, especially those near the front, are filled with zeolite grains 4. Then, the cartridge 29 is replaced as necessary. The backwash pipe 18 branches out so as to spray air and water in front of each curl ridge 29. The other parts are the same as those on each side.

The filter bag f1 ¥30 shown in FIG.
A small crystal grain (1.5 to 4 mmφ) filled with cristobalite was placed as a filler, and then a zeolite particle (5 to 8 mmφ) was placed.
) 4 filled with zeolite tank 32, Cristobal stone grains (
Cristobal tanks 23 filled with 5 to 7 mmφ) 3 are lined up, and a sludge filtration tank 25 is arranged at the end.

The pre-treatment tank 31 is for removing large pollutants such as SS, and the filter layer is thin (also, not only Cristobal stone grains but also sand 7 can be used. Also, in this example, the sludge filter tank 25 is filled with sand (river sand), but as in the previous example, balas 15 may be mixed in or a layer of Cristobal stone grains may be provided. A backwash water return pipe 35 is connected.The backwash air feed pipe 34 is also used for aeration.

Therefore, in this device 30, the water treated in each type 31, 32, 23 is transferred to the treated water outlet pipe 36, 37, 10, respectively.
The liquid is sent to the next tank by water pressure through the tank, but it may also be sent by a pump. The filtered water is stored in a filtered water tank 38 and sequentially discharged. This device has various easy-to-clean advantages.

In addition, when treating wastewater with low SS content, the apparatus shown in Fig. 7 without the pretreatment tank 31 can be used, or depending on the nature of the wastewater, the zeolite tank 32 and Cristobal stone tank 23 can be replaced. good.

The filtration device 39 shown in FIG. 8 has a structure similar to the device shown in FIG. ．．
Store 42.43.44. Cristobal stone grains 3 (sand 7 is also acceptable) of about 2 to 5IIIlφ are placed in the uppermost case 41 for pretreatment, zeolite grains (5 to 15 mmφ) are placed in the second case 42, and the third case 43
Cristobal stone grains (5 to 15 mmφ) are filled in the case 44, and river sand (balas and Cristobal stone grains are also acceptable) is filled in the lowermost case 44. Raw water inflow pipe 9, backwash water return pipe 35,
The backwash water pipe 33 and the backwash air feed pipe 34 (which can be used also as the pipe 33) are arranged one by one. The treated filtrate water is discharged from the top of the filtration tank 3 days later. This device has the advantage of requiring less installation space. In addition, the pre-treatment layer tank zeolite tank may be omitted or the zeolite tank and Cristobal stone tank may be replaced depending on the properties of the wastewater.

[Effects of the Invention] As detailed above, the sewage filtration method of the present invention uses porous minerals such as cristobalite to adsorb pollutants in ice water, and filters and removes flocs. It is.

Therefore, not only SS, fine particles, and microorganisms in wastewater, but also nitrogen and phosphorus, which cause eutrophication, can be significantly reduced.

Moreover, since no chemicals such as building blocks are used, the cost is low and there is no secondary pollution. Furthermore, the device has a simple mechanism, is easy to operate and manage, and can be used in small-scale areas such as households. Furthermore, since it is possible to process large volumes at low cost, it is ideal for large-scale projects such as the treatment of agricultural wastewater, and its effects are immeasurable.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between immersion time and measured values when Cristobal stone grains and zeolite grains are immersed in raw water (tertiary treated domestic wastewater), where (al is PH1 (bl is 1'-P
, (C1 indicates ammonia state N, (dj indicates COD). Figure 2 (al, (bl and (C1) are schematic cross-sectional views of different sewage filtration experimental equipment, respectively. Figure 3 shows raw water (sewage tertiary treatment). Graphs showing changes in TN and TP before and after treatment of water), and FIGS. 4 to 8 are cross-sectional views of different sewage filtration apparatuses, which are examples of the filtration apparatus of the present invention. 15...Balance 22, 26, 27, 30, 39...Filtering device 2
3... Cristobal stone tank 25... Sludge filtration tank 28... Cartridge tank 3I... Pretreatment tank 32... Zeolite tank 38. ...Filtering water tank 40...Filtering tower 1-12, 14...Sewage filtration experimental device 2, 2A
・2B・7... Filter media tank 3... Cristobal stone granules 4... Zeolite granules 8... Sand 9... Raw water inflow Pipe 1O・36・37... Treated water outflow pipe 11・
...Filtered water outflow pipe soaking time soaking time

Claims (1)

[Claims] 1. A method for filtering wastewater, which comprises passing wastewater through a layer of granular porous minerals such as cristobalite to remove pollutants in the wastewater as flocs and precipitates. . 2. The method for filtrating wastewater according to claim 1, wherein ammonia nitrogen in the wastewater is adsorbed and removed by a zeolite layer, and phosphorus contained therein, together with SS and organic substances, is removed by forming flocs in a Cristobal stone layer. . 3. The method for filtering wastewater according to claim 1 or claim 2, wherein sludge consisting of flocs and precipitates is removed by a sludge filtration layer. 4. The method for filtering wastewater according to claim 1 or 2, wherein the water is passed through a pretreatment layer filled with sand and/or Cristobal stone particles, and then passed through a zeolite layer and/or a Cristobal stone layer. 5. In front of the sludge filtration tank filled with sand or sand and ballast, a Cristobal stone tank or a Cristobal stone tank and zeolite tank is placed as a treatment tank, and a backwash pipe and a backwash water withdrawal or return pipe are installed. A sewage filtration device characterized by: 6. The sewage filtration device according to claim 5, further comprising a pretreatment tank filled with sand and/or Cristobal stone particles placed in front of the treatment tank.