JPH0531492A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To enhance the disposal efficiency of waste water, to shorten fermentation treatment time and to miniaturize a treating equipment by irradiating waste water mixed with methane fermentation bacteria with light or mixing methane fermentation bacteria with waste water, and furthermore, interposing an optical semiconducter therein and then irradiating this waste water with light. CONSTITUTION:Water 1 to be treated which contains organic waste water is introduced into a reaction tank 5 made of glass wherein methane fermentation bacteria 3 and an optical semiconductor 4 are present though an inlet 2. Light is irradiated from a light source 6 provided to the outside of the reaction tank 5. Treated water 7 digested in the reaction tank 5 is discharged from an outlet 8 and also the produced gas is recovered or discarded through a gas outlet 9. Outflow of the methane fermentation bacteria 3 and the optical semiconductor 4 is prevented by the filters 10 provided to the inlet 2 part and the outlet 8 part. Further, the inside of the reaction tank 5 is agitated by an agitator 11 having an agitation rod made of polytetrafluoroethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater with methane-fermenting bacteria, and more particularly to a method for treating wastewater that efficiently performs methane fermentation in the process of treating wastewater and sewage discharged from factories and households. Involve

[0002]

2. Description of the Related Art A water treatment method using microorganisms treats sewage, human waste, and industrial wastewater at a lower cost than conventional technology by a high-concentration bioreactor, and makes it possible to reuse the wastewater. Various technologies have been developed. Among them, the methane fermentation method using anaerobic microorganisms does not require aeration power, produces a small amount of sludge, and can recover energy as methane gas, so it is more energy-saving than aerobic treatment such as the activated sludge method. It is evaluated as an effective wastewater treatment method.

However, the conventional methane fermentation method is carried out at a medium temperature (around 37 ° C.) to a high temperature (around 60 ° C.), and it is necessary to heat the methane fermentation method in order to prevent the temperature of the waste water from decreasing and the methane fermentation to decrease in the winter. There is. Therefore, a large amount of energy is lost due to heating.

Further, compared with aerobic microorganisms, anaerobic microorganisms such as methane-fermenting bacteria have a remarkably small cell yield per substrate and a slow growth rate. Methane fermentation may stop.

In order to solve these problems, the concentration of methane-fermenting bacteria can be apparently sought by methods such as searching for methane-fermenting bacteria that are active even at low temperatures, attaching the methane-fermenting bacteria to a carrier, or allowing them to self-granulate. Attempts have been made to increase the number, to improve chemical engineering in terms of hardware such as a bioreactor, and the like. However, the present situation is that none of the methods have obtained satisfactory results.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and includes sewage, human waste,
It is intended to provide a method for efficiently and economically treating industrial wastewater and the like by using methane-fermenting bacteria.

[0007]

The present invention is a method for treating wastewater using methane-fermenting bacteria, which comprises irradiating the wastewater containing the methane-fermenting bacteria with light. .. Examples of the waste water include urban sewage,
Examples include wastewater containing organic substances such as domestic effluent, factory effluent, and agriculture, forestry and livestock effluent.

Examples of the microorganisms related to the methane-fermenting bacteria include Clostidium genus and Bac, which are involved in the process of lowering the molecular weight of high molecular weight organic compounds in wastewater.
illus genus, Staphylococcus genus, and other carbohydrate-degrading bacteria, also Plectridium spum
genus arum, Caduceus cellosaehy
Clostr, a fibrinolytic bacterium of the genus Dogenicus, etc.
genus idium, genus Proteus, bacterium
Proteolytic bacteria such as m genus and Bacillus genus; Clos
lipolytic bacteria such as tridium Kluyveri genus,
Etc. are mentioned as microorganisms in the process of acid production. Examples of microorganisms involved in the process of gasifying low molecular weight organic compounds include Mazei, d of the genus Methanococcus
eltae, vannielie, voltae, Me
methanoica, b of the genus Tanosarcina
arkeri, acetivorans, Methan
fomimicum, ome of the genus Obacterium
lianskii, propionicum, sohn
genii, subboxydans, Methano
genus caraci, marinsnigr
i, arb of the genus Methanobrevibacterium
Examples include methanogens such as oriphylicus and smithin. In addition, as a microorganism having a symbiotic relationship with the methane-fermenting bacterium, the genus Desulfovrio,
Desulfomonas sp., Desulfococ
cus genus, Desulfobacter genus, Desul
genus fobulbus, Desulfosarcina
Genus, Desulfonema, Desulfomac
Sulfur-reducing bacteria such as Ulum.

The light source for irradiating the light may be any one that emits light in the visible or ultraviolet region, for example, a mercury lamp,
A hydrogen discharge tube, a halogen discharge tube, a xenon discharge tube, a Lyman discharge tube, or the like can be used. These light sources
You may use individually or in combination of 2 or more. In addition,
The lamp, which is a light source, may be installed outside the reaction tank containing the methane-fermenting bacterium, or may be installed inside the reaction tank. In addition, various methods such as continuous, intermittent, or fixed period irradiation may be adopted for the light irradiation. In addition, the treatment method according to the present invention permits irradiation of the wastewater in which the methane-fermenting bacteria are mixed and the photo-semiconductor is interposed, with light.

The optical semiconductor is not particularly limited as long as it can effectively accelerate the decomposition / conversion pathway of a substance by microorganisms by light irradiation. As the material of the optical semiconductor, for example, a simple substance such as Si or Ge;
InP, GaP, Zn ₃ P ₂ and other metal phosphide; Al
Metal arsenides such as As and GaAs; CdS, ZnS,
Metal sulfides such as Cu ₂ S; metal selenides such as CdSe and ZnSe; metal tellurides such as CdTe and ZnTe; metal oxides such as TiO, ZnO and SrTiO ₃ ; and ternary or quaternary elements made of these semiconductors. Mixed crystals such as GaAlAs, InGaAs, ZnSSe,
InGaAsP, GaAl-AsP, CuInS ₂ , C
Examples thereof include uInSe ₂ . You may use these materials individually or in combination of 2 or more types.
The optical semiconductor may be used in the form of particles, or may be used in the form of a thin film immobilized on the wall surface of a carrier or a reaction tank in consideration of economical aspect. When the optical semiconductor is used in the form of particles, the amount used is 0.001 to 10 relative to the inflowing wastewater
%, More preferably 0.01 to 1%.

The optical semiconductor thin film layer is formed by a vacuum vapor deposition method, a sputtering method or a CVD method. The thickness of the thin film layer is preferably about 500 to 10,000 angstroms. When the optical semiconductor is unstable in an aqueous solution, the surface of the thin film layer may be covered with a protective film. As the protective film, it is desirable to use, for example, a metal thin film or a conductive polymer film such as polypyrrole.

[0012]

According to the present invention, by irradiating the wastewater containing methane-fermenting bacteria with light, the pathways such as the enzymatic reaction, hydrogen transfer and electron carrier, which are the metabolic systems of the methane-fermenting bacteria, are stimulated, The reaction process of methane fermentation is accelerated. As a result, it becomes possible to treat sewage, night soil, industrial wastewater, etc. efficiently and economically even in a low temperature range.

Further, by mixing the methane-fermenting bacteria and irradiating the wastewater containing the photo-semiconductor with light,
Since the protons and carriers supplied only by the enzymatic reaction can be obtained from the optical semiconductor, stable methane fermentation can be performed.

[0014]

Embodiments of the present invention will be described below with reference to the wastewater treatment apparatus shown in FIG. Example 1

As shown in FIG. 1, treated water 1 containing organic wastewater is introduced from a treated water inlet 2 into a glass reaction tank 5 having a capacity of 5 liters in which methane-fermenting bacteria 3 and optical semiconductors 4 are present. It is introduced and processed while being irradiated with light from a light source 6 installed outside the reaction tank 5. The reaction tank 5
The treated water 7 digested in step 1 is discharged from the treated water outlet 8, and the generated gas is recovered or discarded through the gas outlet 9. In such a treatment step, the outflow of the methane-fermenting bacteria 3 and the optical semiconductor 4 is performed by the filter 10 having a pore size of 20 to 30 μm provided in the treated water inlet 2 portion and the treated water outlet 8 portion of the reaction tank 5. To prevent. The inside of the reaction tank 5 is stirred by a stirring rod made of polytetrafluoroethylene of a stirring device 11.

Specifically, as the methane-fermenting bacterium 3, one prepared in an anaerobic glove box is used to store about 4.5 liters in the reaction tank 5, and the optical semiconductor 4 has a 325 mesh pass. 25 g of titanium dioxide powder was stored in the reaction tank 5. Under such conditions, the synthetic substrate 13, which is the treated water having the composition shown in Table 1 below, in the tank 12 was supplied by the roller pump 14 into the reaction tank 5 placed at 20 ° C. in a dark room, and then the stirring was performed. The light source 6 (halogen lamp; illuminance 100,000 lux) was continuously turned on while stirring the inside of the reaction tank 5 with the apparatus 11 under the condition of 60 rpm. The amount of methane gas and the amount of carbon dioxide in the produced gas after 75 hours were measured. The results are shown in Table 2 below. In addition, Table 2 also shows each gas amount when the halogen lamp is not turned on.

[0017]

[Table 1]

[0018]

[Table 2] Example 2

In the processing apparatus having the configuration shown in FIG. 1, a photoflash (guide number 45) is used as the light source 6 without using an optical semiconductor, and is set to emit light once every 30 seconds. The synthetic substrate 13 which is the treated water having the composition shown in Table 1 was darkened by a roller pump 14 in a dark room, 20
It was continuously supplied into the reaction tank 5 kept at 0 ° C. for 7 days at a flow rate of 0.005 ml / min. The changes in the amount of methane gas and the amount of carbon dioxide in the produced gas at this time are shown in Table 3 below. In addition, Table 3 also shows the respective gas amounts when no light emission by strobe was performed.

[0020]

[Table 3]

[0021]

As described above in detail, according to the wastewater treatment method of the present invention, in the anaerobic fermentation treatment for purifying domestic wastewater or industrial wastewater, is it possible to irradiate the wastewater mixed with methane-fermenting bacteria with light? By mixing the methane-fermenting bacteria and irradiating the wastewater with the optical semiconductor interposed between them, the wastewater can be treated more efficiently, the fermentation treatment time can be shortened, and the treatment equipment can be downsized. Play.

[Brief description of drawings]

FIG. 1 is a schematic view showing a wastewater treatment device used in an example of the present invention.

[Explanation of symbols]

1 ... Treated water, 3 ... Methane fermenting bacteria, 4 ... Photo semiconductor, 5 ... Reaction tank, 6 ... Light source, 11 ... Stirrer, 13 ... Synthetic substrate.

Claims (1)

What is claimed is: 1. A method for treating wastewater using methane-fermenting bacteria, which comprises irradiating the wastewater containing the methane-fermenting bacteria with light.