Deodorizing method of drainage water and deodorizing purification unit, making use of electrolysis

Abstract

To address the following situations that health of neighboring residents or plant workers has been damaged by foul odors arising from a foul odor-causing substance discharged from a plant, etc., as countermeasures against them, ones by activated-sludge process have been principally taken, yet although measures using electrolysis as electric method have been recently taken, a method using hypochlorite by adding chlorite is often taken, and a method called as slight acidic electrolytic water also uses slight hypochlorite.SOLUTION: A method includes: subjecting a foul odor-causing substance such as methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide included in drainage water from a food plant, etc., to solid-liquid separation by using coagulant, not through decomposition by microorganisms or without adding chloride nor using ozone generator; and then deodorizing and purifying the foul odor-causing substance by directly oxidizing the substance with fine oxygen bubbles obtained by electrolysis.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to the deodorization and purification of malodor-causing substances such as methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide in wastewater. [Background technology]

[0002] There are various methods for reducing organic compounds in wastewater, including biological decomposition methods such as the activated sludge method, treatment methods using ozone oxidation, and methods that utilize hypochlorous acid produced by electrolysis.

[0003] In particular, the commonly used biodegradation method requires a long processing time, a large facility area, and proper management of microorganisms at all times (Patent Document 1).

[0004] Ozone is a highly reactive substance with strong oxidizing power, and therefore has a high rate of oxidation of organic matter, but is highly toxic when its concentration is high. (Patent Document 2)

[0005] In addition, because it is not easily absorbed by water, if it enters the respiratory system it can reach deep into the lungs and cause respiratory disorders (pulmonary edema, etc.).

[0006] The mainstream method of decomposing and deodorizing organic matter by electrolysis uses chlorine, such as hypochlorous acid electrolyzed water, obtained by electrolyzing chlorides that are already present in wastewater or that have been added separately (Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6490774 [Patent Document 2] Patent No. 6905236 [Patent Document 3] Patent No. 7298784 Summary of the Invention [Problem to be solved by the invention]

[0008] The bad odors emitted from factories and other facilities have been harmful to the health of local residents and workers.

[0009] As a countermeasure, the activated sludge method has been mainly used.

[0010] In recent years, electrical methods such as electrolysis have been used as a countermeasure, but the most common method is the use of hypochlorous acid by adding chlorides.

[0011] In addition, a method called slightly acidic electrolyzed water also uses slightly hypochlorous acid. [Means for solving the problem]

[0012] This method does not involve decomposition by microorganisms, the addition of chlorides, or the use of ozone generators. It instead involves performing solid-liquid separation using a flocculant to deodorize odor-causing substances such as methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide contained in wastewater from food factories and the like, and then directly oxidizing the substances with fine oxygen bubbles obtained by electrolysis to deodorize the substances. Effect of the Invention

[0013] The activated sludge method is often used to break down and deodorize odor-causing substances such as methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide contained in wastewater from food factories, but the treatment time is long and the facilities required are large-scale.

[0014] In the present invention, since the flocculation solid-liquid separation and electrolysis are carried out in the same tank, the treatment facility can be significantly reduced in size and the treatment time can be significantly shortened.

[0015] In addition, by shortening the distance between the electrodes in the electrolysis device and arranging the electrodes in a stack, the device itself can be made smaller, power consumption can be reduced, and the amount of oxygen generated can be secured.

[0016] When the treatment shown in Figure 1 was carried out, wastewater samples A to D were collected at each measurement point to verify the effectiveness.

[0017] When the chlorine content was measured, no chlorine was detected in any of samples A to D.

[0018] When total phosphorus was measured, the BOD value was 75 mg / L in sample A, and was below the measurement limit in samples B to D.

[0019] Total nitrogen was measured as 9 mg / L in sample A, and below the measurement limit in samples B to D.

[0020] The odor was examined by three testers using the odor judgment method, and all three testers found that sample A had a very strong odor, sample B had a slight odor, and samples C and D were almost odorless.

[0021] Sample C was aerated for 12 hours, and sample D was treated with finely-bubbled oxygen produced by electrolysis for 12 minutes. The odor was significantly improved in both cases, but there was a large difference in the treatment time. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a process flow chart showing a comparative experiment between the present invention and biological treatment. [Diagram 2] 1 shows a coagulation electrolysis cell of the present invention. [Diagram 3] 1 shows a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In FIG. 2, raw water that has been roughly filtered in advance using an electric sieve is taken in through raw water supply pipe a and stored in tank b.

[0024] After the water has been stored, the stirring blade f is rotated by a motor attached to the top, generating a water current within the tank.

[0025] Coagulant is added through supply pipe c. The amount to be added varies depending on the target water, so the amount should be determined in advance.

[0026] When flocculation is observed in tank b, the stirring blade f is rotated at a slow speed by the motor attached to the top.

[0027] The electrolysis device g is operated to simultaneously carry out direct oxidation and flotation separation using fine oxygen bubbles.

[0028] Convection currents generated within tank b promote the oxidation process by repeatedly passing between the electrodes of device g.

[0029] In addition, air bubbles generated by device g cause the aggregates to float to the water surface and accumulate.

[0030] The flocculants that rise to the surface of the water are removed by a rotating belt conveyor e connected to a motor.

[0031] The purified water remaining in tank b is discharged through discharge pipe h. [Industrial Applicability]

[0032] Wastewater from food factories and other facilities contains a lot of organic matter, and in the past, reservoirs or water storage facilities were built on large tracts of land and the organic matter was decomposed using the activated sludge process. By using the present invention, processing can be completed in a short period of time with a minimum of facilities. This will enable effective use of the site while preventing health hazards to workers and nearby residents. [Explanation of symbols]

[0033] aRaw water supply pipe b Water tank c Coagulant supply pipe d Stirring blade support rod E-belt conveyor f stirring blade gElectrolysis device

Claims

1. This deodorization method and deodorization purification device uses a flocculant to separate odor-causing substances such as methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide contained in wastewater from food factories, etc., into solid and liquid form, and then decomposes and deodorizes the resulting waste liquid by contacting it with oxygen generated by electrolysis.

2. 2. The deodorizing method and deodorizing purification apparatus according to claim 1, wherein the solid-liquid separation tank by coagulation reaction and the electrolysis tank are the same tank, and the tank for floating and separating the coagulated matter using fine bubbles generated by electrolysis is provided.

3. 3. A deodorizing method and deodorizing / purifying apparatus according to claim 1 or 2, wherein the distance between the anode and cathode which generate fine bubbles by electrolysis is set to 1.5 mm to 3 mm.

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