JPH01155998A - Method for removing fat and oil component in waste water - Google Patents

Abstract

PURPOSE:To substantially completely decompose and remove the fat and oil components in waste water so that the residues such as sludge thereof are not formed at all by adding fat splitting bacteria to the waste water and supplying air to the waste water thereby allowing the water to flow and oscillating the water surface thereof. CONSTITUTION:The fat and oil component-contg. water water to be treated is introduced into a raw water tank 1 and the air is blown into this waste water by an aerator 6 in this raw water tank 1, by which the waste water to be treated is fluidized and swirled in the tank 1. After the fat splitting bacteria are added to the swirling and flowing waste water, the waste water is lifted by a lifting pump 2 and is sent to a flow rate regulating tank 13 of a high water level. The waste water sent to said tank is partly sent to an ejector 4 and the water surface of the raw water tank 1 is vigorously beaten by the discharge pressure of the ejector 4. A large quantity of the air is incorporated into the water discharged from the ejector 4 by the air suction effect generated by the pressure reduction which takes place when the water is discharged from the ejector 4. This air promotes the activity of the bacteria and accelerates the formation of the fat and oil components to the fine segments by the oscillation of the water surface of the raw water tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for removing oil and fat from domestic wastewater.

[Conventional technology, problem 3 Domestic wastewater discharged from people's daily activities includes, for example, general household sewage, wastewater from hotels, restaurants, various buildings, and kitchen wastewater from school lunch centers. These wastewaters contain vegetable oils such as salad oil and sesame oil, and animal fats and oils such as lard.

Conventionally, these domestic wastewaters are often treated by the activated sludge method, which decomposes fluorescent matter, carbohydrates, etc. very well, but it is difficult to decompose fats and oils. Oils and fats form an oil film and obstruct air circulation, which may inhibit microbial activity in some cases.For example, in the rotating disk activated sludge treatment method, which is a typical domestic wastewater treatment method, an oxidizing atmosphere caused by oils and fats is used. Due to the deterioration of the activated sludge, the activity of microorganisms declines, and the filtration membrane on the disc that performs the function of activated sludge loses its vital function and falls off, which not only fails to remove BOD, which is the original purpose of activated sludge. Since the filter membrane that falls off becomes slime and makes the treated water turbid, it is necessary to install a sedimentation tank or filter after the rotating disk treatment device to remove the turbidity. is the reality. Furthermore, recently, a method of installing a permeable membrane such as a semipermeable membrane in an activated sludge treatment apparatus has become popular for the purpose of reusing wastewater treated in buildings, condominiums, hotels, etc. However, in this case, oil and fat in the wastewater, which is difficult to treat with activated sludge, adheres to the permeation membrane, which significantly impairs the permeation function of the membrane and shortens its lifespan. Removal of fats and oils in biochemical wastewater treatment is essential for maintaining the healthy wastewater treatment function of microorganisms, but until now there has been no method that can do this. For example, there is a method of removing fats and oils using adsorption activity of aluminum hydroxide, iron hydroxide, etc., but a large amount of sludge remains after processing the fats and oils, and concentrating and dehydrating the sludge is time-consuming and costly. becomes expensive,
It is shunned. Another method is to use a flotation device to float the oil and fat as scum and remove it by scraping it off with a schema, but the disadvantage is that it is not easy to dispose of the scraped scum, and the flotation device is large and occupies a large area. There is.

Furthermore, there is also the disadvantage that the floating scum scatters outside the device and damages the surrounding environment. There is also a method of removing oil by adding enzymes such as lipase, which propagate by breaking down and ingesting oil, to oil-containing wastewater, but adding fungi only takes a long time to remove all of the oil in wastewater. Oil in the corner of the wastewater sump, which has long been floating and stagnant on the surface, forms an oil film that resists fungal activity and is not easily decomposed. Alternatively, even if it decomposes, a pitch-like 9% substance is formed in the process, which becomes a deposit and causes problems such as clogging the pump suction for conveying waste water.

[Means for solving problems]

In view of the current situation, the present invention is a method for removing fat and fat bones from wastewater, which is characterized by adding fat-decomposing bacteria to wastewater containing fat and oil, aerating the wastewater to make it flow, and shaking the water surface.

The purpose of deoiling is not achieved simply by adding fat-degrading bacteria that break down oil and fat to wastewater; instead of just making the wastewater flow while or after adding fat-degrading bacteria, it is necessary to pound the surface of the wastewater. Vigorous shaking is used to finely disperse fats and oils not only in the wastewater but also on the surface of the wastewater.

Only by promoting contact with decomposing bacteria can the purpose of oil removal be fully achieved.

The present invention involves adding to wastewater fungi such as mutant bacteria that decompose fats and oils in wastewater (animal and vegetable fats and fats such as salad oil, sesame oil, and lard), and fluidizing the wastewater to which the fungi have been added. This is a method for treating oil-containing wastewater that consists of shaking the water surface violently, and unlike conventional methods, it utilizes the simple adsorption effect of polyvalent metal hydroxides (flocs). Unlike a single operation using oil-degrading enzymes or a simple oil-degrading enzyme, this method adds the flow of wastewater and the vibration of surface water to the action of oil-degrading fungi (including enzymes), and removes oils and fats from wastewater through the interaction of these. This method differs greatly from conventional methods in terms of the multiple operations involved.

Next, a method for removing oil and fat from wastewater according to the present invention will be explained in detail with reference to FIG.

An aerator 6 is installed in the raw water tank 1 into which wastewater containing oil and fat to be treated is introduced, and the wastewater introduced into the raw water tank 1 has a specific gravity difference due to the air blown by the aerator 6, causing a difference in the specific gravity inside the tank. Flowing and swirling. Fat and oil decomposing bacteria are added to this swirling wastewater.

The fungi used in the present invention include enzymes or bacterial enzyme condensates that hydrolyze oily substrates, or mutant bacteria that secrete such enzymes.

Any enzyme that hydrolyzes oily substrates and bacteria that secrete such enzymes can be used, but
If the fat or oil contained in the wastewater is a substrate with a high melting point, such as beef tallow, it is desirable to use a substrate that is reactive and heat-resistant at high temperatures and works above its melting point, such as Shutomonas cepacia. The mutant bacteria used in the present invention are collected from nature, cultured and grown, and after colony formation, selectively isolated and confirmed decomposition ability. Ultraviolet rays, radiation, or mutagenic agents are added to the bacterial species to create a plasmid. A mutant bacterium is created by changing the gene sequence of the . Micrope Masters Inc
Products such as Perth Bio-Mix, manufactured by , are made by repeating this series of operations to improve the ability to decompose oil, mass culturing, and freeze-drying, and in addition to various nutrients and supplementary enzymes, microbial carriers are also added. Contains wheat bran, etc. For example, if the total number of bacteria per gram is 3 billion (e.g., commercial product Perth Bio Mix), the amount of these fungi added is initially 5.
~200mg/j! , preferably 5 to 50 μ/l, and after that, continue to add while monitoring the decline in the effectiveness of the bacteria, but approximately once a week 0.5 to 100 μ/2, preferably 0.5 to 51 g /P. Oil-degrading bacteria are usually in the form of dry powder, so before adding them, add approximately 5 times the weight of water to the oil-degrading bacteria and knead them into a paste for several hours (
(approximately 4 hours or more) before adding to the wastewater.

The wastewater to which oil-degrading bacteria have been added is pumped up by a pump 2 and sent to a flow rate adjustment tank 3 at a high water level. The pump 2 has a pump head of at least 3 m (discharge pressure of 0.3 kg).
/ ci or more), a portion of the water is sent to the ejector 4 using a water supply amount that is more than 5 times the amount of treated water, and the discharge pressure of the ejector 4 violently hits the water surface of the raw water tank 1. At this time, the water discharged from the ejector 4 contains a large amount of air due to the suction action caused by the reduced pressure accompanying discharge from the ejector 4, and this air supports the vitality of the bacteria and causes the water surface of the raw water tank 1 to fluctuate. Promotes the subdivision effect of fats and oils through motion. At the initial stage of operation of the flow rate regulating tank 3, the valve 8 at the outlet of the tank 3 is closed, and the entire amount of water sent by the pump 2 is returned to the raw water tank 1 using the overflow pipe 5. The overflow water having a water level difference promotes the subdivision effect of the oil and fat content due to the fluctuation of the water surface of the oil-containing wastewater in the raw water tank.

The oil-containing wastewater to which bacteria have been added is pumped up by the pump 2, sent to the high-level flow rate adjustment tank 3, and the entire amount is returned to the raw water tank 1 again as an initial operation, which is repeated for several hours, during which time the ejector 6 is activated. As a result, the bacteria become active and the oil content in the wastewater decreases. When the oil content decreases, the valve 8 at the outlet of the flow rate adjustment tank 3 is opened while adjusting the flow rate to sequentially send out the treated water and continue operation. After continued operation, the aerator 6 is operated while replenishing bacteria intermittently, and the ejector 4 and overflow are used to replenish air and flow the wastewater, and the water surface is violently shaken to eliminate blind spots. Hold it so that it doesn't.

Dissolved oxygen in the wastewater in the raw water tank is 0. Close 0°3~3
．． It is sufficient to operate the aerator 6 and ejector 4 to maintain 0 mg/1, and this value is determined by the aerator 6 swirling the water in the tank, the ejector 4 hitting the water surface, and the blind spot (stationary water surface). This is a sufficient value that can be obtained even when the function of preventing the occurrence of damage is achieved with the minimum (bare line). The aerator 6 and the ejector 4 are preferably operated so that their respective purposes are achieved within the limits; excessive operation results in energy loss and is meaningless.

As is clear from the above description of the specific treatment method, the present invention involves: ■ Adding bacteria (for example, mutant microorganisms, trade name Perth Bio Mix, etc.) that have the ability to decompose fat and oil substrates to wastewater; This is a method for deoiling wastewater containing oil and fat, which has the following three elements: (1) making the wastewater to which has been added flow, and (1) preventing the water from violently undulating on the water surface to create dead spots.

■Since fats and oils are removed by substrate decomposition, it works more fundamentally against oils than the conventional deoiling method using coagulation and adsorption, and there are no leaks or residues.

(2) In conventional coagulation and adsorption methods, both sedimentation and flotation separation methods produce sludge and scum, which is difficult to dispose of, but the present invention does not produce sludge or scum.

■The device of the present invention in front of the activated sludge treatment device (see Figure 1)
If installed as a pre-treatment facility, the functionality of the activated sludge treatment equipment will improve as oil and fat will be removed.In particular, in rotating disc-type activated sludge treatment equipment, the filtration membrane will no longer fall off the disc, making it easier to install as a post-treatment facility. The coagulation sedimentation tank or solid-liquid separation clarification tank that was previously used can also be significantly reduced in size.

■When activated sludge treatment equipment is combined with the equipment of the present invention, a food chain of enzymes, bacteria, and protozoa is established, and the biochemical sewage purification effect is further improved, compared to the case of activated sludge treatment alone. The amount of surplus sludge generated due to the sewage purification effect is extremely small.

■With conventional physical deoiling equipment, the oil content extracted with normal hexane is 0.1mg/I! , it is difficult to do less.

In the present invention, since the oil content can be reduced to 0.1 mgzl or less, there is no caking phenomenon of the fat content.

Example 1 The water quality of artificial sewage made with the mixing ratio shown in Table 1 is as shown in Table 2.

Table 1 Composition of artificial sewage 48.9 g of the composition shown in Table 1 was dissolved in 12 water and diluted 70 times. Diluted water 70I! Add 10.5 g of salad oil to the mixture and stir thoroughly. The analytical values of the artificial sewage thus obtained are as follows.

Table 2 Water quality of artificial sewage Treatment capacity 2I of the configuration shown in Figure 1! The experiment was conducted using a batch method using a 7-minute experimental apparatus. First, 60ffi of artificial sewage with the water quality shown in Table 2 was put into a raw water tank L with a diameter of 42 CIlΦ and a height of 65 C1, and the aerator 6 (a device for swirling the water in the tank using pressurized air) in the raw water tank L was activated. Fluidize wastewater. In addition, the pump 2 is operated to pump up raw water at a rate of 202/min, and a part of the waste water is separated at a rate of 51/min by opening the branch pulp 7 placed at a position 1.5 m from the rising pipe. Run the water, activate the ejector 4 with the water,
At the same time as sucking air with negative pressure (5 ai of water column),
5I per minute! The amount of water is slammed onto the water surface of the raw water tank 1 to generate waves on the water surface. By operating the ejector 4 and the aerator 6, the wastewater in the raw water tank 1 flows sufficiently so that no dead space (place where there is no movement or no wave motion) is created either in the water or on the water surface. ! M! The pumped wastewater (151/min) after branching the water volume per minute to the ejector 4 is sent to the flow rate adjustment tank 3 2.5 m above the ground, but the outlet (treated water sending valve) of the flow rate adjustment tank 3 is closed. Therefore, the total amount of pumped wastewater (15'j!/m) sent into the flow rate adjustment tank 3 returns to the raw water tank 1 through the bar flow pipe 5 as it is.

Since the water level difference is approximately 2 m, the overflow water that falls into the raw water tank 1 returns to the raw water tank 1.
The wastewater inside is further agitated and disturbed. In this state, fat-degrading bacteria (trade name: Perth Bio-Mix) contains mutant Pseudomonas bacteria, wheat bran as a microbial carrier, and various nutrients.

The total number of bacteria is 3 billion per 1 g of product) and 6 g of the waste water is added to 60ffi of raw water tank 1. 6g of fat-degrading bacteria (product name Perth Bio Mix) is 30c in advance.
The mixture was added to the water in step c, stirred to sufficiently disperse it in the water, and left to stand for 5 hours before use. The oil removal rate of the overflow water (sampled at the outlet of the flow Mm adjustment tank) when the operation was continued after adding bacteria was as shown by the solid line in FIG. 2. Until 4 hours when the bacteria start to become active, no oil removal phenomenon can be observed, but after 5 hours, the oil removal rate improves rapidly, reaching 95% in 12 hours and almost 100% in 16 hours.
% of oil was removed, and the remaining oil amount was reduced to just a trace.

Comparative Example 1 In Example 1, the same amount of oil-degrading bacteria as in Example 1 was added, while the aerator and ejector were operated as in Example 1, and overflow from the flow rate adjustment tank was carried out by taking advantage of the water level difference. The experiment was carried out under the condition that the oxygen required for the growth of bacteria (3 to 5 μ/fl as dissolved oxygen) was blown into the raw water tank 1 using an aeration pipe without any cultivation.
As shown by the dotted line in Figure 2, the oil removal effect was considerably inferior to that of Example 1, and even after 24 hours, the oil removal rate was 30%.
% was not reached. Particularly on the water surface, oil and fat-degrading bacteria combine to form pitch-like floats, and as a result, the fat-degrading bacteria are sealed in an oil film and become inactive. This point greatly affected the oil removal effect (if the oil film is dispersed by stirring,
The oil removal reaction progressed rapidly). In addition, in Example 1, if the bacteria were added, the aerator 6 was operated, and air was added while stirring, and the waste water was not circulated to the ejector and flow rate adjustment tank, the bacteria would not be removed. The start time of the oil activity is one hour later than in the case of Example 1, and the time required for complete oil removal is almost 1 hour later than in Example 1.
It was a huge delay, 36 hours instead of 6 hours. From this, it is possible to eliminate the dead face (static surface that does not move) caused by waves on the water surface of the raw water tank due to the ejector and overflow with a water level difference, and the water containing air falls to the water surface with a water level difference, finely dispersing the oil film and preventing bacteria. It has been found that preventing pitch travel, which is caused by the bonding of oil and oil, is an essential factor in oil removal operations that use bacteria.

Example 2 Table 3 shows the oil and fat content in wastewater according to the menu at the school lunch center.
It was as follows.

Table 3 □ 60ffi of these menu-specific wastewaters were put into the raw water tank of the experimental equipment used in Example 1, which had a treatment capacity of 22/min and had the configuration shown in Figure 1, and an experiment was conducted in the same manner as in Example 1. I got a grade of 4.

Table 4 The types of fats and oils used vary depending on the menu, but when processed according to the present invention, regardless of the type of fats and oils, the amount of fats and oils remaining after treatment is 0.1■/j2 in all cases.
It was below.

Comparative Example 2 The results of treatment using the conventional method of pressurized flotation using caustic soda to adjust the pH to 10.5 and using ferric chloride as a flocculant are shown in Table 5. In both cases, the oil and fat content remaining after treatment was 0. 1■/
I1. Above, the wastewater (wastewater from the kitchen) especially in the case of salad and fried rice was 31g/1 or more.

Table 5 Note that in the pressurized flotation method, 0.0021 scum was generated per 12 scum of waste water, and the treatment was very troublesome compared to the case where no scum is generated as in the present invention.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, fats and oils are almost completely decomposed and removed, so there is no residue such as sludge, and no scum is generated. Therefore, post-processing as in the conventional method is not necessary. Furthermore, the biochemical purification effect is further improved when combined with an activated sludge treatment device because it can be processed efficiently.The system uses air to remove oil instead of relying solely on chemicals (such as enzymes) as in the conventional method. Therefore, the practical economic effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for implementing the method of the present invention, and FIG. 2 is a graph showing the relationship between elapsed time and oil removal rate in Example 1 and Comparative Example 1. Patent applicant Takashi Kumazawa Joint Hiroo Yakuai・～1゛-7・

Claims (1)

[Claims] A method for removing fats and oils from wastewater, which is characterized by adding fat-decomposing bacteria to wastewater containing fats and oils, aerating the wastewater to make it flow, and shaking the water surface.