JPH0227037B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a simple method for treating gray water, and more particularly to a method for easily treating gray water, excluding human waste, among domestic wastewater discharged from ordinary homes, restaurants, shops, hospitals, etc. Traditionally, domestic wastewater has had a major impact on water pollution in rivers, lakes, and sea areas, and organic pollution in urban rivers and eutrophication in closed water bodies such as lakes and inland seas are mostly caused by domestic wastewater. This is caused by drainage. By the way, about 3/4 of the pollutants in domestic wastewater are contained in gray water other than raw human waste, and there are methods to remove solids from gray water in each household using screens or by installing settling tanks. Attempts have been made to remove solids and suspended solids. However, although these methods require inexpensive equipment, they produce pollutants such as BOD and COD.
There was a problem that the removal rate was only about 10 to 30%. On the other hand, conventional methods for decomposing pollutants in domestic wastewater using microorganisms require expensive equipment, a large installation area, complicated installation work and maintenance, and are difficult to manage from large-scale living organisms. Although it is effective in treating domestic wastewater, it has the drawback that it cannot be used to treat gray water from small-scale living entities such as ordinary households. Therefore, the present invention was made in view of the current situation, and uses a small device to stabilize organic pollutants in gray water that does not contain human waste, regardless of extremely large fluctuations in water quality, water volume, water temperature, etc. It has the advantage of being particularly suitable as a small-scale domestic gray water treatment method. In other words, the simple method for treating gray water of the present invention is to stagnate gray water that does not contain human waste and have large flow rate fluctuations, separate solids to adjust the water quality, and collect this waste water into a container with a surface area of 1 m2 of filling volume. around ³
300 m ² or more, specific gravity 1.5 or less, and sinking porous granules are supplied as a microbial support as an upward flow, and air is blown from below the microbial support at a rate of 5 cm/min or more. While maintaining the microorganism concentration per tank at 5 to 15 g per tank, the microorganism support is repeatedly suspended and sedimented according to the fluctuation in the flow rate of the gray water, and the microorganism support is not washed. The method is characterized in that organic pollutants in the wastewater are decomposed by microorganisms. Hereinafter, the present invention will be explained based on the drawings. FIG. 1 shows the process of the present invention, in which gray water 1 containing no human waste is led to a regulating tank 2. Adjustment tank 2
has the function of removing solid matter and equalizing water quality. Preferably, the gray water 1 is passed through a screen tank 3 in advance to remove large solids, hair, etc. Here, gray water refers to wastewater generated from household cooking, bathing, laundry, etc. that does not contain human waste, and similar wastewater from restaurants, shops, hospitals, etc.
Usually, it contains vegetables, rice grains and other foods, as well as their extractables, hair, detergents, fiber fragments, etc. Another characteristic of gray water is that its flow rate fluctuates significantly depending on the time of day. That is, the flow rate of wastewater increases significantly during the time from breakfast to washing, from dinner to bathing, and when draining the bath compared to other times. Most of the solid matter is separated from this domestic wastewater by retaining it in the adjustment tank 2. The average residence time varies depending on the quality of gray water, flow rate, etc., but it is normally 2 to 12 hours, and gray water from which solids have been removed as new gray water flows into the adjustment tank 2. It is supplied to the microbial treatment tank 4 as an upward flow. The entire microbial treatment tank 4 is filled with a microbial support, and air is blown from below the microbial support at a linear velocity of 5cm/
Delivered in minutes or more. As microbial supports, artificial lightweight aggregates, crushed stones, fibers, or plastic materials of various shapes can be used in any shape and size, but especially those with a surface area of 200 m ² / m ³ or more, and those with heavy weight in water where buoyancy acts. Preferably, the porous particles have a density of 0.5 g/cm ³ or less, that is, a specific gravity of 1.5 or less, and that sink in water. The amount of microbial support packed is usually more than 1/10 and less than 1/3 of the average daily wastewater volume, and the BOD load is 0.5.
〜1.5Kg/ ^m3・day. In addition, by supplying air at a linear velocity of 5 cm/min or more, the waste water is sufficiently agitated, improving the contact between the microorganism support and the waste water, and filling the gaps between the microorganism supports filled with air bubbles. Since the water rises through the water, it is possible to prevent the microorganism support from being clogged by suspended matter in the wastewater or grown microorganisms. In particular, using porous granules with a specific gravity of 1.5 or less and sinking in water as a microbial support, and allowing the microbial support to repeatedly float and settle in response to fluctuations in the flow rate of gray water, is an effective way to improve the microbial support as well as the air flow rate. It is effective in preventing blockage. Furthermore, in the present invention, it is important that the microorganism concentration in the microorganism treatment tank 4 is 5 to 15 g/. Here, the microorganism concentration refers to the dry weight of microorganisms per unit volume of the microorganism treatment tank 4, and compared to the microorganism concentration in the tank of 2 to 3 g/in the conventional domestic wastewater microbial treatment method, the present invention has a significantly higher microorganism concentration. It has a very high concentration. Such a high microbial concentration is achieved by filling the entire small microbial treatment tank 4 with an appropriate microbial support as described above, and by supplying wastewater to the support in an upward flow. be done. When the microorganism concentration is less than 5 g/min, the ability to decompose organic pollutants in wastewater decreases, and the treatment equipment becomes larger and more expensive, making it difficult to install in a general household. In addition, increasing the microorganism concentration to more than 15 g/g increases the risk of clogging and is unlikely to be realized. In the present invention, the microorganism concentration as described above,
Decomposition of organic pollutants in the wastewater is promoted by a dense and active microbial film formed on the surface of the microbial support by a variety of microorganisms, depending on the feeding direction of the wastewater and the linear velocity of the air. be done. Additionally, the amount of excess sludge generated can be extremely reduced.
Sedimentation and separation of sludge after microbial treatment is not required. In addition, clogging of the microbial support is prevented, and organic pollutants in the wastewater are decomposed by the microorganisms without special cleaning operations. The average residence time of wastewater in the microbial treatment tank 4 is usually 2 to 8 hours, and the treated gray water is discharged into a regular sewer or permeated into the soil. As a result, since the microorganism concentration per device is high, the device can be downsized, and a simple method for treating gray water, which is suitable for general household use, is inexpensive, and requires a small installation area, is provided. Figure 2 shows a case where a phosphorus removal step is added to the present invention, and after solid matter in wastewater is separated and organic pollutants are decomposed by microorganisms according to the above-mentioned invention, wastewater is phosphorus-removed. It is led to the removal tank 5. The phosphorus removal tank 5 is filled with a phosphorus removal agent, and phosphorus in the waste water is removed by physical adsorption or chemical reaction with the phosphorus removal agent. Here, as the phosphorus remover, aluminum,
Clay minerals containing iron, magnesium and calcium, such as allofen, aluminum, iron,
It is used by adding magnesium or calcium salt, etc., and granulating and molding it. Note that the shape of the phosphorus removing agent can be arbitrarily selected, and may be used in the form of granules, blocks, plates, or the like. Moreover, the filling amount of the phosphorus removing agent can also be appropriately determined according to the phosphorus content in the waste water, and the average residence time of the waste water in the phosphorus removal tank is usually 1 to 3 hours. Next, the relationship between water flow rate and BOD removal rate in the present invention described above is shown in Table 1 below. That is, glucose, peptone, corn staple liquor, and linear alkylbenzene sulfonate (abbreviated as LAS) are mixed in 10 small treatment tanks filled with 1.5 to 3 cm of artificial lightweight aggregate or fiber mat to produce approximately 150 mg of BOD/ What happens when model gray water adjusted to
We investigated the BOD removal rate.

[Table] From Table 1, it is clear that a sufficient BOD removal rate can be obtained even with a water flow rate of 3 to 10 times the capacity of the microbial treatment tank per day and a BOD load of 0.5 to 1.5 kg/ ^m2 /day, that is, effective A microbial treatment tank with a capacity of 1/10 to 1/3 of the average daily wastewater volume removes approximately 70% of organic pollutants.
It is clear that 90% can be removed. In particular, artificial lightweight aggregate, which is a porous granular material with a surface area of 300 m ² or more per 1 m ³ of filling volume, is particularly susceptible to the attachment of microorganisms and has superior pollutant removal performance compared to conventional microbial supports. . In addition, when artificial lightweight aggregates with a specific gravity of 1.1 to 1.2 and light weight are supplied with drainage in an upward flow, the aggregates repeatedly float and settle, which can be expected to have an aggregate cleaning effect and easily prevent blockages. This artificial lightweight aggregate is used as a building material, and can also be produced from sludge from sewage treatment plants, etc., and can be obtained at low cost. Next, 200 pieces were filled with artificial lightweight aggregate in the same way as above.
The above model gray water was added to the microbial treatment tank at a rate of 100 per hour between 6:00 a.m. and 11:00 a.m. and from 6:00 p.m. to 9:00 p.m., and at other times. 20 every hour, total for the day
The removal rate of BOD and COD was investigated while flowing at 1200 ml. The results are shown in Table 2 below. The linear velocity of the air in the cylinder was 10 cm/min. The microorganism concentration in the microorganism treatment tank was 7 g/, and the suspended solids concentration in the treated water was 5 to 20 mg/.

[Table] From Table 2, it can be seen that a good BOD and COD removal rate can be achieved even in a household that generates a total of 1200 effluents per day. In addition, in order to investigate changes in the water quality of gray water, especially the effects of the inflow of highly concentrated detergents, we similarly filled 200 microbial treatment tanks with artificial lightweight aggregate and
While aerating at a rate of 10 cm/min, artificial gray water was flowed in the same manner as above, and water containing LAS with a different concentration was flowed in at 120 times per 10 minutes once a day, and the BOD removal rate and foaming status were measured 60 minutes after the flow. Examined. The results are shown in Table 3.

[Table] From this result, it is considered that the LAS concentration needs to be 40mg/or less. By the way, the maximum concentration of LAS in washing waste water in ordinary households is about 250 mg/kg, and the capacity of the washing tank is reduced to 30 mg/kg.
If this is the case, it would be sufficient to install at least about 200 regulating tanks per household. This capacity is 5
It corresponds to 1/5 of the average daily wastewater discharge of a household, and in the case of a large household, it is equivalent to 1/2, i.e.
It is preferable to provide about 500 adjustment tanks. If wastewater from several households is to be treated together, a regulating tank with a capacity of about 1/10 of the average daily wastewater volume will suffice, since all households will not discharge concentrated washing water at the same time. This capacity corresponds to 1/3 to 1/20 of the capacity of the adjustment tank in conventional microbial treatment of domestic wastewater. Next, a similar test was conducted using artificial gray water at 12°C, and it was found that the BOD removal rate decreased by only about 2% during times of high water flow, indicating that sufficient treatment could be achieved even at low temperatures. Furthermore, in the present invention, wastewater after organic pollutants have been removed as described above can be brought into contact with a phosphorus removing agent. Now, add 1 to 2 parts of aluminum salt solution per 1 kg of clay mineral, for example, allofene, granulate and mold, fill this molded product 1 into a small phosphorus removal tank, and treat the above model gray water in the microbial treatment tank. After that, reduce the phosphorus concentration to about 4mg/
We ran water adjusted to the same amount at different flow rates to determine the number of days it could be used until the average daily phosphorus removal rate was 50% or less. The results are shown in Table 4 below.

[Table] From this result, 30% of the volume of phosphorus remover per day
Phosphorus can be removed for more than 60 days with less than twice the amount of water flowing through the tank, that is, by filling a small phosphorus removal tank with an effective capacity of 1/30 or more of the average daily water flow rate and bringing it into contact with wastewater. 50% of phosphorus in wastewater
It can be seen that the above can be removed for a long period of time. As an example of a simple treatment device used in the present invention, a gray water treatment device for a five-person household is shown in FIGS. 3A and 3B. Domestic gray water 1 is supplied from the upper part of the adjustment tank 2, and the regulated wastewater with solids removed is supplied to the microbial treatment tank 4 as an upward flow from below through the partition wall 6, where it is aerated. Device 7
Air bubbles are supplied from The microbial treatment tank 4 is entirely filled with a microbial support 8, and the wastewater from which organic contaminants have been removed is further led to the phosphorus removal tank 5, dephosphorized with a phosphorus removal agent 9, and then discharged. In addition, in FIGS. 3A and 3B, the units of numbers are mm. If a draining basket is placed in the adjustment tank 2, the solids accumulated in the basket can be easily taken out as needed. Alternatively, the phosphorus remover may be filled in a mesh plastic container and removed and replaced when performance deteriorates. As described above, according to the present invention, the specific gravity is 1.5.
Below and submerged porous granules are used as microbial supports. In addition, the microbial support is made to flow by utilizing the large flow rate fluctuations peculiar to gray water. Furthermore, in addition to these conditions, the surface area of the porous granules is 300 m ² or more per 1 m ³ of filling volume, the drainage is supplied as an upward flow, and the air is supplied at a rate of 5 cm / min or more. By simultaneously filling the
Wastewater is treated without washing the microbial support. That is, in the present invention, when the drainage flow rate is low, the microbial support tends to settle and forms a fixed bed, whereas when the drainage flow is large, the microorganism support repeatedly floats and settles, forming a fluidized bed. Such flotation and sedimentation of the microbial support, together with the action of air bubbles rising through the gaps in the microbial support, prevents blockage and clogging of the microbial support, and allows the microbial support to be drained without periodic cleaning operations. Therefore, according to the present invention, since the microbial support is not cleaned, there is no need for cleaning equipment or operations, and the equipment is small and inexpensive. , easy to maintain and manage. Therefore, the present invention is suitable as a simple method for treating gray water. Furthermore, as the proliferation of microorganisms is significantly promoted, bacteria, protozoa, metazoa, and many other types of organisms coexist in the microbial treatment tank at high concentrations, resulting in a large amount of surplus sludge being produced. There is no need to treat sludge that has been precipitated and separated as in the past. Therefore, the treated wastewater can be directly discharged into a sewage ditch, etc., and maintenance of the device does not require much effort. This proves that the method of the present invention is more preferable as a simple method for treating wastewater from small-scale living entities such as general households. Examples of the present invention will be described below. Example 1 An average of 980 grey-water wastewater generated per day from cooking, bathing, washing, etc. of a family of five people was treated using the wastewater treatment equipment shown in FIGS. 3A and B. The microbial treatment tank 4 was filled with artificial lightweight aggregate having a diameter of 1.5 to 3 cm, and the ventilation rate was 10 cm/min. As a result, the BOD in wastewater was 8 to 25 mg/,
COD was maintained at 7 to 15 mg/day, and approximately 83% of the daily BOD load and approximately 75% of the COD load could be removed. In this case, the concentration of microorganisms in the microorganism treatment tank was about 7.5 g/day, and the power consumption of the blower was only about 1 KWh per day. Example 2 When the wastewater from which organic pollutants were removed according to Example 1 was brought into contact with the phosphorus removal agent 30, which was prepared by adding aluminum salt to allofene as described above,
The total phosphorus concentration in the wastewater was maintained at less than 1.0 mg/day for 61 days, and approximately 60% of the daily phosphorus load was removed. Example 3 An average of 8.3 m ³ of kitchen wastewater per day at a restaurant was treated in a 1 m ³ regulating tank and a 2 m ³ microbial treatment tank filled with artificial lightweight aggregate by aerating at 14 cm/min. BOD in water less than 20mg, COD 15mg/
I was able to keep it below. Comparative Example 1 As a microorganism support, crushed stone, Raschig ring, honeycomb tube, whose properties are shown in Table 5 below, artificial lightweight aggregate A which is a porous granular material with a large specific gravity, and the same material as used in Examples 1 and 3 were used. 10 filled with artificial lightweight aggregate B, which is a porous granular material with a small specific gravity.
While supplying actual domestic gray water with a BOD of approximately 140 mg/day to a small treatment tank in an upward flow at 120/day,
Table 6 shows the microorganism concentration, BOD removal rate, and presence or absence of uneven flow due to blockage when ventilation was performed from below the microorganism support at a rate of 10 cm/min.

【table】

[Table] Tables 5 and 6 show that conventional microbial supports such as crushed stone, Raschig rings, and honeycomb tubes have a microbial concentration of only 5 g/or less, so the BOD removal rate is not high. It is clear that artificial lightweight aggregates A and B, which are porous granules with a surface area of 300 m ² /m ³ or more, have a particularly high microbial concentration compared to other microbial supports. In addition, crushed stone with a specific gravity of 2.8, Raschig ring with a specific gravity of 2.6, and 1.6
It is clear that artificial lightweight aggregate A with a specific gravity of 1.2 and artificial lightweight aggregate B with a specific gravity of 1.1 do not clog, although the flow of water and air is biased due to blockage. That is, the surface area is 300 m ² per 1 m ³ of filling volume.
Porous granular materials such as the above-mentioned artificial lightweight aggregates (artificial stones) are particularly susceptible to attachment of microorganisms, and the microorganism concentration can be as high as 5 to 15 g/g. In particular, by using lightweight porous granules with a specific gravity of 1.5 or less, such as artificial lightweight aggregate B, wastewater is supplied in an upward flow, and air is supplied from below the microbial support at a speed of 5 cm/min or more. By supplying the water, the microorganism support is washed by repeatedly floating and settling as the flow rate of the waste water changes, and clogging can be easily prevented.

[Brief explanation of drawings]

Figure 1 is a process diagram of the present invention, Figure 2 is a process diagram showing the case where a phosphorus removal process is added to the present invention, and Figure 3 is a process diagram of the present invention.
Figures A and 3B are explanatory diagrams of a wastewater treatment device used in the second invention. 1... Gray water, 2... Adjustment tank, 4... Microbial treatment tank, 5... Phosphorus removal tank.

Claims (1)

[Claims] 1. Domestic wastewater that does not contain raw human waste and has large fluctuations in flow rate is retained, solids are separated to adjust the water quality, and this wastewater is divided into areas with a surface area of 1 ^m3 of filling volume.
300 m ² or more, specific gravity 1.5 or less, and sinking porous granules are supplied as a microbial support as an upward flow, and air is blown from below the microbial support at a rate of 5 cm/min or more. While maintaining the microorganism concentration per tank at 5 to 15 g per tank, the microorganism support is repeatedly suspended and sedimented according to the fluctuation in the flow rate of the gray water, and the microorganism support is not washed. A simple method for treating gray water, characterized in that organic pollutants in the wastewater are decomposed by microorganisms.