JPS61274724A - Treatment of malodor - Google Patents

Abstract

PURPOSE:To inexpensively deodorize a malodor without requiring large scale equipment, by using the ferric sulfate solution obtained by oxidizing a ferrous sulfate solution by iron oxidizing bacteria as an absorbing solution to absorb ammonia being a malodor source. CONSTITUTION:A FeSO4 solution acidified by sulfuric acid is flowed in an oxidizing tank 1 in which iron oxidizing bacteria cultured in a ferrous sulfate- containing solution such as waste water from non-ferrous metal mine and acid resistance porous particles such as diatomaceous earth as a carrier were received and a nutrient such as ammonium phosphate is added to said FeSO4 solution and air is blown therein to oxidize the same to a Fe2(SO4)3 solution. The Fe2(SO4)3 solution overflowed from the oxidizing tank 1 is introduced into a second iron supply tank 3 through a separation tank 2. Next, the Fe2(SO4)3 solution is guided to the aspirator 4 of an absorbing process and single gas or a gaseous mixture of NH3, SOx or H2S coming to a malodor generation source is sent into the aspirator 4 to be absorbed. The FeSO4 solution generated by absorptive reaction is returned to the oxidizing tank 1. A necessary amount of the ferrous salt becoming deficient by reaction is added to the oxidizing tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field The present invention relates to ammonia, a sulfur compound, which is a malodor-generating gas,
This relates to a method for absorbing and separating hydrogen sulfide, etc., and more specifically, it involves producing a ferric sulfate solution from a ferrous sulfate solution using iron oxidizing bacteria, and absorbing gases that generate a bad odor using the ferric sulfate solution. , the first sulfuric acid produced by reduction
The present invention provides a method for treating malodors in which an iron-containing solution is used as it is or by adding a ferrous sulfate salt, and then subjected to bacterial oxidation and then used repeatedly as a ferric sulfate solution to absorb the aforementioned malodor-generating gas.

(b) Background technology Currently, the only way to deodorize bad odors is to use high-concentration methods.

Combustion deodorization method (direct combustion, catalytic combustion) for medium concentration odors
, chemical cleaning deodorization method (oxidizing agent such as alkaline solution 9 sodium hypochlorite, etc.), use of physical adsorbent (activated carbon, zeolite, etc.) or chemical adsorbent (ion exchange resin, acidic adsorbent, alkaline adsorbent, etc.) Various methods have been provided, such as a biological deodorization method (soil deodorization method, activated sludge method, etc.), an ozone method, etc.

Among these treatment methods, combustion deodorization methods and chemical cleaning methods are generally used to remove bad odors from gas, but at present they have the drawback of high cost.

(C) Disclosure of the Invention The present invention provides a method that can inexpensively process ammonia, sulfur oxides, hydrogen sulfide, etc. that are the causes of bad odor in gas.

That is, in the method of the present invention, in the first step, an acidic sulfuric acid solution containing ferrous sulfate is introduced into an oxidation tank, a small amount of inoculum of iron oxidizing bacteria (hereinafter simply referred to as bacteria) is added, and air is blown into the tank to quench the bacteria. and simultaneously oxidize ferrous sulfate to ferric sulfate.

In this case, nonferrous metal mine drainage, smelting drainage, factory drainage, etc. can be used as the ferrous sulfate-containing liquid, and Fe2+
If the concentration is in the range of 1 to 50 g/1, it will be sufficiently oxidized by bacteria.

The pH is adjusted to 3.0 or less by adding sulfuric acid if necessary, while taking into consideration oxidation efficiency and without causing precipitation in the oxidation tank.

In addition, when the liquid does not contain the above-mentioned bacteria or their nutrient sources, such as smelting wastewater, it is preferable to add nutrients (salt to N, P, etc.) to make the bacteria grow.

Furthermore, in order to trap the grown bacteria without letting them escape, it is preferable to add acid-resistant porous material particles as a carrier agent to increase the bacterial cell concentration in the oxidation tank. and,
After the acid-resistant porous material particles are separated in a separation tank, they are repeatedly used in an oxidation tank.

Here, acid-resistant porous material particles refer to porous materials with a large surface area on which iron-oxidizing bacteria can settle and inhabit as many bacteria as possible. Zeolite, activated carbon, Fuller's earth, asbestos cotton, and other particles have the property of easily settling under standing conditions, but it has been confirmed that diatomaceous earth is particularly excellent.

In addition, - instead of the above acid-resistant porous material, the PH during the absorption reaction
to hydrolyze ferric sulfate in the absorption liquid by increasing the
The produced iron precipitate can also be used as a carrier agent.

Next, the ferric sulfate solution that has been oxidized by bacteria in the oxidation tank is used as an absorption liquid to absorb the malodorous gas (second step).

As the absorption method, the malodor-generating gas may be diffused from the bottom of the tank filled with the ferric sulfate solution, or it may be sprayed from the L side. Incidentally, in Kizuna MM, an aspirator or an absorption tower is used depending on the target gas, but the method is not limited to these.

The reaction in the absorption process differs depending on the target gas as described below.

l) In the case of ammoniaa) NH, + H20+NH, (OH)b) 6
NH& (DH)2 +Fet, (SOa) a→
2 Fe(OH)a + 3 (NHa) 2 SO
4, and ferric hydroxide and ammonium sulfate are produced.

2) For sulfur compounds SO9, +Fe2 (SO4) 2 +2H20+2
It becomes FeSO4+ 2 H2SO4, and ferrous sulfate and sulfuric acid are produced.

In this case, the pH value decreases, so calcium carbonate is added, and the resulting gypsum is extracted from the system using a centrifuge and recovered.
The iron is repeated in the oxidation tank of the first step.

3) For hydrogen sulfide H2S +Fe2 (SO,a) a -2FaSO
,+)I2SO,+S.

Thus, H2S is oxidized to produce SO and ferrous sulfate is regenerated.

In this case, since fine colloidal sulfur is present in the reaction liquid, yellowish-white sulfur milk is produced. For this, by adding a seed sulfur slurry.

The produced colloidal sulfur is aggregated and separated and recovered as simple sulfur with good sedimentation and separability, and the separated liquid is repeated to the oxidation tank of the first step.

The ferrous sulfate solution obtained in this way, either as it is or after adding ferrous sulfate, is repeatedly transferred to the bacterial oxidation tank of the first step, and the bacteria that have been sufficiently cultured and have obtained activity are It is oxidized again to ferric sulfate and used to absorb these malodorous gases.

The bacteria used in the present invention are known rThio-ba
cillus Ferrooxidance J, etc., and the iron-oxidizing bacteria in the treated mud were cultured in a solution containing a high concentration of ferrous ions, etc., using wastewater mud as a seed.

The oxidizing ability of the iron-oxidizing bacteria cultured by this method is 2 to 5 times higher than that of normal oxidizing ability (Deposit number: FEIKEN Bacteria No. 7443, No. 7444)
No. 7555, No. 7556).

Embodiments of the method of the present invention will be described below with reference to the accompanying drawings.

(d) Examples Example 1 As shown in Fig. 1, an oxidation tank 1 with a capacity of 500 tons was filled with 20 tons of iron oxidizing bacteria cultured at the K mine wastewater treatment plant and 100 tons of quartz algae with a pulp concentration of 15%. Add sulfuric acid to pH 2.0
Fe5D4 adjusted to (Fez + concentration 5 concentration 5 ~ 2
0g of liquid was continuously introduced at a rate of 2 times per minute, and ammonium phosphate was added as a nutrient at a rate of 50mg per minute.
JL and air blowing was performed at 80 v/min.

The overflow liquid from the oxidation tank 1 was introduced into a separation tank 2 with a capacity of 300 liters, and then introduced into a ferric supply tank 3 with a capacity of 400 liters. The overflow liquid contains almost completely oxidized Fe.
2 (so a ) 8 solution.

Next, the ferric sulfate solution is introduced into the 7 spirator 4 of the absorption process at a flow rate of 2 cubic meters per minute, and about 1000 ppm
Concentrated ammonia gas was introduced at a rate of 4 KL/min and absorbed. When the absorbed gas was tested using a Kitagawa detector tube, no ammonia was detected.

The ferric hydroxide generated in this reaction was periodically extracted from the oxidation tank.

In addition, the ammonium sulfate produced acts as a nutrient for bacteria, making it possible to reduce the amount of ammonium phosphate that was initially added.

The required amount of ferrous iron, which was insufficient due to the reaction, was added to the oxidation tank 1.

Example 2 As shown in Figure 2, under the same conditions as Example 1, about 5%
A concentration of I(2S) gas was introduced at a rate of 4 g/min and absorbed.

When the absorbed gas was tested using a Kitagawa detector tube, it was not detected for 3 minutes.

Next, the absorbed liquid is introduced into a coagulation tank 6 with a capacity of 170 tons,
Approximately 120 g/liter of seed sulfur slurry was added at a ratio of 2θ% to the liquid and stirred with a stirrer.

Next, the treated liquid is led to a sedimentation tank 7 with a capacity of 170 tons to cause precipitation, solid-liquid separation is carried out, and the overflow liquid has a capacity of 3.
After leading to the cushion tank 9 of 00J1, the capacity is 300
The ferrous iron solution was introduced into the ferrous iron supply tank 10 of No. 1, and the ferrous iron solution was repeatedly introduced into the oxidation tank I.

On the other hand, a seed sulfur slurry was recovered from the underflow in the sulfur recovery tank 8, a part of which was recycled to the flocculation tank, and the remainder was recovered as elemental sulfur.

Example 3 As shown in Fig. 3, sulfuric acid was added to an oxidation tank 1 with a capacity of 500Q containing 20 bacteria of iron oxidizing bacteria cultured at the K mine wastewater treatment plant and a 15% bulb concentration of oxidation tank 1 to adjust the pH to 2. 0
FeSO4 (Fe20 concentration 20g/KL) solution adjusted to
The mixture was added so that the amount of air was blown at a rate of 80 blows/min.

The overflow liquid from the oxidation tank 1 was introduced into a separation tank 2 with a capacity of 390 tons, and then introduced into a ferric iron supply tank 3 with a capacity of 3B5fL. The overflow liquid is a nearly completely oxidized ferric sulfate solution.

Next, this ferric sulfate solution is introduced into the second-stage absorption tower 12 in the absorption process at a flow rate of 5/min, and the 502-containing gas (
so9: about 0.05%) was introduced and absorbed at a rate of 200 m''/Hr.

When the absorbed gas was analyzed, no S02 gas was detected.

Next, the absorbed liquid is transferred to a neutralization tank 1 with a capacity of 600J1.
5, and about 20% calcium carbonate is added from the charcoal feeder 13 so that the pH value becomes about 1.8,
After stirring, the mixture was introduced into a sedimentation tank 7 having a capacity of 940 tons, and the underflow was collected in a centrifugal separator 17 as gypsum.

On the other hand, the overflow liquid and the centrifuged separated liquid were introduced into an iP liquid tank 16 having a capacity of 385 cm, and then returned to the bacterial oxidation tank 1.

The conditions of this example are shown in Table 1, and the results are shown in Table 2.

(Left below) (E) Effects of the present invention As described above, the method of the present invention can reduce ammonia, which is a source of bad odor,
This is a method of treating single gases such as sulfur compounds and hydrogen sulfide, or a mixture of these gases by absorbing them into a ferric sulfate solution oxidized by iron-oxidizing bacteria.
Compared to conventional methods, it is cheaper and does not require large equipment, etc.
It also has a great cost advantage.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of the method of the present invention when ammonia is treated, FIG. 2 is hydrogen sulfide, and FIG. 3 is a sulfur compound. Symbol explanation 1 - Oxidation tank 2 - Separation tank 3 - Ferric supply tank 4 - Aspirator - 5 - Absorption tank 6 - Coagulation tank 7 - Sedimentation tank 8 - Sulfur recovery tank 9 - Cushion tank 10 - Ferrous iron supply tank 11-Blower-12-Absorption tank 13-Charcoal feeder 14-Emulsification tank 15-Neutralization tank 16-5 liquid tank 17-Centrifugal separation machine Patent Applicant: Dowa Mining Co., Ltd.

Claims (3)

[Claims] (1) The first step is to oxidize the ferrous sulfate solution to ferric sulfate using iron-oxidizing bacteria, and the ferric sulfate solution obtained in the first step is used as an absorbing liquid to contact ammonia gas, which is a source of bad odor. A method for treating bad odors, comprising a second step of absorbing it, and a third step of adding a ferrous salt to the overflow liquid from the second step. (2) Ferrous sulfate solution is oxidized to ferric sulfate using iron-oxidizing bacteria, and the resulting ferric sulfate solution is used as an absorption liquid to contact and absorb the odor-generating gas, thereby producing ferrous sulfate. A method for treating bad odors, characterized in that the iron solution is repeated in the first step. (3) The method for treating malodors according to claim 2, wherein the malodor-generating gas is a sulfur compound or hydrogen sulfide.