JPH0777601B2 - Method for removing adhered microorganisms - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing adhered microorganisms in a gas-liquid contact tower, and more particularly in a deodorizing tower for malodorous gas using a packing material or a cooling tower for high temperature gas. The present invention relates to a method for removing adhered microorganisms.

[Prior Art] A malodorous gas containing ammonia and hydrogen sulfide, using a commercially available filling material such as peat or a sponge filling material, in the method of biologically deodorizing, the pressure loss of the packed bed hardly increases, It doesn't matter.

However, when the above malodorous gas contains an organic gas, for example, a volatile fatty acid such as acetic acid, microorganisms significantly grow in the packed bed, resulting in an increase in pressure loss.

Also, even in a scrubber type cooling device whose purpose is to reduce temperature rather than deodorizing, the same applies when the inflowing high-temperature gas (dry exhaust gas or exhaust gas from composting treatment) contains organic gases such as volatile fatty acids. At the same time, microorganisms grow in the packed bed and pressure loss increases.

Conventionally, in such a case, the filler is taken out of the system to mechanically remove the adhering microorganisms with a water stream or the like, or sodium hypochlorite or sodium hypochlorite and caustic soda are filled with the filler. We were carrying out chemical cleaning to be used together.

[Problems to be Solved by the Invention]

As described above, the related art has the following problems.

(1) In the mechanical peeling method, the filler is taken out, washed,
Refilling work is troublesome and workability is poor.

(2) The chemical cleaning method requires the use of dangerous chemicals, and requires waste liquid treatment after use.

Therefore, an object of the present invention is to provide a method for safely and efficiently peeling and removing microorganisms adhering to a packed bed in order to prevent an increase in pressure loss in the packed bed of a gas-liquid contact tower.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, in a gas-liquid contact column having a packed bed filled with a filler to which microorganisms are adhered, characterized in that the inside of the tower or the packed bed is anaerobic conditions This is a method for removing microorganisms.

The above gas-liquid contact tower can be particularly effectively applied to a deodorizing tower for a malodorous gas caused by microorganisms or a scrubber tower for reducing the temperature of a high temperature gas.

Specifically, the present invention specifically stops a gas flowing into a gas-liquid contact tower such as a deodorizing tower or a cooling tower, and then preferably adds a reducing agent to the liquid circulating in the apparatus (hereinafter, circulating liquid), and if necessary, By heating, the packed bed and the circulating liquid are brought into an anaerobic state, so that the adherent microorganisms are peeled off from the packing material and removed.

The present invention will be described in detail below.

INDUSTRIAL APPLICABILITY The present invention can remove microorganisms attached to the packing material by the same method in any gas-liquid contact device such as a biological deodorizing device for malodorous gas, a water cleaning device, and a cooling device for high temperature gas. .

First, the gas flowing into the apparatus is shut off, and the supply of air or oxygen to the packed bed is stopped. Although it is only necessary to form an anaerobic state in a sealed state, after that, a reducing agent is added to the circulating liquid to make the circulating liquid anaerobic, and this circulating liquid is supplied to the packed bed on which microorganisms adhere to thereby make the entire packed bed. Can also be anaerobic.

The pH of the circulating fluid is preferably 6-8.

Although any known reducing agent can be used,
Particularly preferred is sodium bisulfite, which has a low pH drop and is inexpensive.

The amount of the reducing agent added is usually about 1 w / v% with respect to the total circulating fluid. The anaerobic properties of the circulating fluid may be controlled by the redox potential (ORP). Sodium bisulfite is appropriately added to the circulating liquid so as to maintain the ORP of the circulating liquid at −50 mV to −300 mV (internal liquid: saturated KC1, reference electrode: Amano electrode).

Further, by heating the circulating liquid to 30 ° C to 50 ° C, the anaerobic state is promoted for the microorganisms adhering to the circulating liquid and the packed bed.

A heater or the like may be used for heating, but continuous operation of the circulation pump for watering the packed bed increases the water temperature of the circulating liquid and makes it possible to secure the temperature required to promote the anaerobic state. Become.

After confirming that the whole system has become anaerobic by ORP etc., stop the circulation pump. If the water temperature is 30 ° C or higher, leave it for 30 minutes, and if it is lower than 30 ° C, leave it for 1 to 5 hours.
The circulating fluid in the circulating water tank is discharged to the outside of the system and at the same time, the packed bed is washed with water. The packed bed is washed with SS-free wash water such as well water and industrial water to remove microorganisms that have become easy to peel off. The wash water containing the separated microorganisms is immediately discharged to the outside of the system and is not reused.

Next, the present invention will be described with reference to FIG. 1 showing a schematic sectional view thereof.

The damper 1 of the raw gas inflow pipe is closed. While constantly operating the circulation pump 8, 1 w / v% of sodium bisulfite as a reducing agent is added to the circulating water tank 10 as a reducing agent.

After that, the circulation pump is operated for about 30 minutes and then stopped. If the temperature of the circulating fluid is 30 ° C or lower, continue operating the circulation pump to warm the circulating fluid. It is also possible to heat with a heater or the like.

The circulation pump is stopped, and after 30 minutes, the discharge valve 7 of the circulation pump is closed, the drain valve 9 is opened, and the washing water line valve 6 is opened to wash the packed bed 2.

Wash with water continuously until SS is no longer recognized in the wash drain. The water washing method is temporary extruded water washing.

[Action]

The cause of the increase in the pressure loss of the packed bed is that the volatile fatty acids and the like in the raw gas are assimilated by the heterotrophic bacteria and the bacteria grow. Heterotrophic bacteria have a large amount of microbial cell growth per substrate and, in addition, produce a highly viscous extracellular polymer.

Under aerobic conditions, this extracellular polymer strongly binds the microorganisms to the packing material or the microorganisms, but under absolute anaerobic conditions, the heterotrophic bacteria cannot operate without oxygen,
The binding force of the extracellular polymer disappears.

For this reason, the individual microorganisms are in a fine particle-like and non-sticky state, and are naturally separated from the surface of the filler. Further, the separated microorganisms are discharged to the outside of the system together with the water flow of the washing water without being reattached to the packing material and re-captured.

〔Example〕

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A slime removal experiment was conducted using a polyethylene filler (trade name: 74 mm in diameter 74 mm) collected from a temperature reducing tower used for the purpose of reducing the temperature and deodorizing the dry exhaust gas of a sludge dryer.

The amount of slime attached to the filler used in the experiment was 0.5 g-dry
SS / piece-filler. Ten fillers were used in the experiment.

In the present invention, the filling material was placed in a closed container 4 and 1% aqueous sodium hydrogen sulfite solution 4 was injected and left at 40 ° C. for about 8 hours.

In the conventional method, a mixed solution 4 of 0.1% Cl ₂ (using NaOCl) and 3% NaOH was poured in place of the aqueous sodium hydrogen sulfite solution of the present invention, and left at 40 ° C. for 8 hours in an open system.

After 8 hours, the filler was gently removed and the amount of slime adhered was measured. The slime removal amount was obtained by subtracting the adhesion amount after the experiment from the adhesion amount before the experiment. The amount of slime removed in the present invention was 0.48 g-dry SS / piece-filler (average value), and in the conventional method 0.4 g-dry SS / piece-filler (average value).

The slime peeled from the filler according to the present invention was in the form of fine particles.

Example 2 Polypropylene (Hilex brand name) as a filler
Using the deodorizing device (FIG. 1) which was filled with 1 m (outer diameter 30 mm) and biologically deodorizes malodorous gas containing mainly volatile fatty acids, the microbial exfoliation experiment according to the present invention was conducted.

After closing the damper of the raw gas inflow pipe, 2 kg of sodium bisulfite was added to the circulating water tank (holding water amount about 200).
The circulating pump was operated and the circulating liquid containing sodium bisulfite was sprinkled on the packed bed at 150 / min for 30 minutes. Circulating fluid p
H was adjusted to 6-8 with NaOH. The water temperature was 30 ° C.

Drain the circulating fluid from the circulating water tank and use well water after 30 minutes.
The packed bed was washed with water / min for 30 minutes.

As a result, the pressure loss of the packed bed was 100 mmH ₂ O at LV 0.4 m / sec and L / G 30 / m ³ before the experiment, but after the experiment, the pressure loss was up to 25 mmH ₂ O under the same conditions. Diminished.

〔The invention's effect〕

The present invention provides a method for removing microorganisms attached to a packing material in order to prevent an increase in pressure loss of the packed bed due to the growth of microorganisms. According to the invention, in a very simple way,
It is possible to easily and safely remove and remove microorganisms.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a gas-liquid contact device according to an embodiment of the present invention. 1 ... Damper for raw gas inflow pipe, 2 ... Filling material, 3 ...
Gas-liquid contact tower, 4 ... Sprinkler, 5 ... Gas outlet, 6 ...
Wash water line valve, 7 ... Circulation pump discharge valve, 8 ... Circulation pump, 9 ... Drain valve, 10 ... Circulation water tank, 11 ... NaHSO ₃
Injection line

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/77 C02F 1/00 ZAB U F28C 1/00

Claims (2)

[Claims] 1. A method for separating adhered microorganisms, characterized in that in a gas-liquid contact tower having a packed bed packed with a packing material to which microorganisms adhere, the inside of the tower or the packed bed is subjected to anaerobic conditions. 2. The method for removing adhered microorganisms according to claim 1, wherein the gas-liquid contact tower is a deodorizing tower for offensive odor gas by microorganisms or a scrubber tower for reducing the temperature of high temperature gas.