JPH08243594A - Method for deodorizing sludge with ozone and sludge deodorizing device - Google Patents

Abstract

PURPOSE: To make the sludge itself oderless, to facilitate the storage, transportation and handling of the sludge and to freely utilize the sludge as resources by mixing the sludge mixed with a dehydrating agent consisting essentially of lime and ozone, and deodorizing. CONSTITUTION: Sludge is mixed with a dehydrating agent consisting essentially of lime and ozone, and the sludge is deodorized by the ozone, lime and their interaction. Namely, the dehydrating agent is introduced into a mixing part 4 from a silo 1, the sludge from a hopper 2 and the ozone from an ozonizer 3, and the mixture is heated by a rotary kiln 5. At this time, since the heat is supplied by the heat of hydration of the lime, external heat is not needed. The waste gas from the kiln is scrubbed in a tower 6. Further, ozone is supplied to the cleaning water, and the waste cleaning liq. is remixed with untreated sludge in the sludge hopper 2. Consequently, the sludge itself is made odorless, and the sludge is easily stored, transported and handled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to deodorizing sludge generated in sewage, septic tanks and the like.

[0002]

2. Description of the Related Art Sewage treatment and disposal of sludge generated in septic tanks have become increasingly difficult due to increasing environmental problems.
For this reason, various methods for dehydrating sludge and reusing it as fertilizers and building materials have been sought, but the solution has not been solved yet. The odor of sludge is a particular problem in the use of sludge. Generally, odors in treatment equipment and facilities are removed by collecting odor components with adsorbents and water, or by oxidizing and decomposing with oxidants, but it is difficult to deodorize the sludge itself. Its use is restricted because it hinders storage and handling.

[0003]

DISCLOSURE OF THE INVENTION The present invention intends to facilitate sludge storage, transportation, and handling by achieving deodorization of sludge itself, which has been difficult in the past, and enable free utilization of sludge as a resource. To do.

[0004]

In the present invention, a sludge is mixed with a dehydrating agent containing lime as a main material and ozone, and the sludge is deodorized by the ozone, lime, and their interaction.

[0005]

Function: Ozone is a gas containing three oxygen atoms and is a strong oxidant. Industrially manufactured by silent discharge,
Used at a concentration of about 3 to 6% in air or dissolved in water. Excessive ozone after use spontaneously decomposes and returns to oxygen, and since it does not produce harmful compounds, it is attracting attention as an environmentally friendly oxidant. It is widely known that ozone is effective for deodorizing indoors and drinking water, but in the case of sludge, even if ozone is directly applied, the effect is not sufficient, and if it is operated for a long time, a new odor substance is generated. You cannot achieve the purpose by creating it. As a result of research, it has been found that it is most effective to simultaneously apply a dehydration treatment agent containing lime as a main material and ozone. This effect is understood as follows. Calcium oxide, which is the main material of the dehydration treating agent, reacts with the water in the sludge to exhibit a dehydrating effect, but a part of the calcium hydroxide generated at that time is ionized to generate hydroxide ions. Hydroxide ions react with ozone to generate active oxygen such as OH radicals, which exert a strong oxidizing action to decompose and remove odorous components in sludge. At the same time, calcium ions form an insoluble salt with a fatty acid and the like generated by oxidation by ozone to suppress generation of bubbles and volatilization of odor associated with ozone treatment. In the examples of the present invention, after mixing sludge, a dehydration treating agent and ozone, they are introduced into a kiln and heated by the heat of hydration of lime. Further, since ozone is introduced into the exhaust gas cleaning water, the odor that has volatilized is decomposed by the ozone water, and the waste liquid is remixed with the raw material sludge, so the odor does not leak to the outside. In the treatment of human waste or the like, the generation of bubbles during aeration may hinder the treatment, but the present invention is also effective for such wastewater. In Document A, the effectiveness of a catalyst, hydrogen peroxide, ultraviolet rays, high pH treatment, etc. for generating active oxygen from ozone is mentioned, but as in the present invention, a special treatment effect was obtained by lime. No report is seen. Reference A: Hidetoshi Sugimitsu, Ozone and active oxygen, Journal of antibacterial and antifungal therapy, Vol. 22, 225-251 (1994).

[0006]

EXAMPLE A dehydration treatment agent containing lime as a main material was introduced into a mixing section 4 from a dehydration treatment agent silo of 1, a sludge to be treated was introduced from a sludge hopper of 2, and ozone was introduced from an ozone generator of 3 into a mixing section 4. Heat in Tally Kiln 5. Since the heat source is supplied from the heat of hydration of lime, no external heat source is required. Exhaust gas from the kiln is washed in a washing tower 6 Ozone is supplied to the cleaning water, and the cleaning waste liquid is remixed with the untreated sludge in the sludge hopper (2).

[0007]

The results of the deodorization test by the batch treatment showing the effects of the present invention are shown in Table 1. It is clear that ozone alone has insufficient deodorizing effect and that ozone can be effectively deodorized only by injecting ozone in the presence of a dehydrating agent. The effect of hydroxide ion itself can be observed because the odor reduction is observed even without ozone at high pH, but the interaction of hydroxide ion and ozone can be seen because the addition of ozone further reduces odor. Is confirmed. However, the action of the dehydrating agent does not only promote the reaction of hydroxide ion and ozone. When ozone and sodium hydroxide were used together, a large amount of bubbles were generated, but the dehydration treating agent completely suppressed this. The generation of bubbles was also observed in the treatment of night soil with ozone, and it was due to the surface active substances such as higher fatty acids generated by the oxidation.The calcium in the dehydration treatment agent was treated with these insoluble salts as in the case of using soap in hard water. It is considered that the formation suppresses foaming. This was confirmed by adding calcium oxide to the treated human waste water. Calcium hydroxide is solidified as calcium carbonate in the air and solidifies, but sodium salts are generally water-soluble, which has an unfavorable effect on the storage of dehydrated sludge, and the superiority of calcium ions is clear. The treated sludge obtained by the above treatment does not have a smell of night soil, etc., so that it does not become an obstacle to transportation, storage and handling. Therefore, for example, if the treated sludge is used as an admixture at the time of producing cement, the organic component in the sludge serves as a fuel and the inorganic component serves as a cement extender, so that the sludge can be utilized as a resource. Cement is mainly a mixture of clayey and calcareous raw materials, fired to a thousand and several hundred degrees, and ground, but the composition is essentially the same as that of the dehydration treatment agent. It is being burned.

[Table 1] Table 1 Deodorization test results ──────────────────────────────────── Pre-treatment odor Post-treatment Odor ──────────────────────────────────── 1 Untreated 10 2 Ozone 3 minutes 9 3 Ozone 5 minutes 5 Dehydration treatment agent 6 4 Sodium hydrogen carbonate 8 Ozone 3 minutes 3 5 Sodium hydroxide 3 Ozone 5 minutes 2 6 Dehydration treatment agent 4 Ozone 5 minutes 2 ──────────────── ───────────────────── 20 g of septic tank sludge with a water content of about 80% was taken, and 25 g of water was added to make an original sample. The composition of the dehydrating agent used is about 8
0% is calcium oxide, 10% is silicon oxide, and others are close to ordinary cement components. 25 g of this dehydrating agent was added to the original sample as a 10% aqueous solution. Ozone is generated from air as a raw material and has a concentration of 7300 ppm and an amount of generation of 440 mg per hour. The odor level of the untreated original sample was 10 by the olfactory test.
And When ozone was made to act on sludge, the odor level decreased from 10 to 9 in 3 minutes and from 10 to 5 in 5 minutes. However, even if the odor was allowed to act for 5 minutes or more, the odor did not decrease further, and qualitative changes in odor were observed. When sodium hydrogen carbonate was applied, the odor level at pH 10 was reduced to 8 and the odor level to which ozone was applied was reduced to 3. In the case of sodium hydroxide, the odor level was 3 at pH 13, and the odor level was reduced to 2 by adding ozone. In the case of the dehydration treating agent alone, the pH was 14 and the odor level was 4, but the nightmarine odor remained. When ozone was made to act on this, the odor level dropped to 2 and only cement odor was produced. Neither the combined use of ozone and hydrogen peroxide nor the application of chlorine dioxide was effective.

[Brief description of drawings]

 Explanatory drawing showing an embodiment of the present invention

[Explanation of symbols]

 1 is a dehydrating agent silo 2 is a sludge hopper 3 is an ozone generator 4 is a mixing section of dehydrating agent, sludge and ozone 5 is a rotary kiln 6 is a gas cleaning tower

Claims (2)

[Claims] 1. A method for deodorizing sludge, which comprises mixing ozone with sludge containing a dehydration treatment agent containing lime as a main material to deodorize the sludge. 2. A dehydrating agent containing lime as a main material from a dehydrating agent silo of 1, a sludge to be treated from a sludge hopper of 2,
Ozone was introduced from the ozone generator 3 into the mixing section 4, and
A sludge deodorization treatment device configured to heat ozone in the exhaust gas washing tower wash water 6 and mix a part of the wash liquid with untreated sludge in the sludge hopper 2 while heating in the tarry kiln 5.