JPH0710388B2 - Treatment method of wastewater containing organic matter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for treating organic matter-containing wastewater by the Fenton method.

[Conventional technology]

As one of the methods for treating organic matter-containing wastewater, the Fenton method in which hydrogen peroxide and iron salts are added to decompose organic matter is known. This method uses an iron salt as a catalyst to oxidize and decompose organic matter by the oxidizing power of hydrogen peroxide.

As an improved method of the Fenton method, hydrogen peroxide and iron salts are added to organic matter-containing wastewater to decompose the organic matter, ferric hydroxide flocs are formed to perform coagulation separation, and then filtration is performed. The filtrate is further treated with activated carbon,
A method of adsorbing and removing undecomposed organic substances such as chromaticity components has been proposed (Japanese Patent Publication No. 59-1120).

[Problems to be solved by the invention]

However, in such a conventional Fenton method for treating organic matter-containing wastewater, a long reaction time of 1 to 2 hours is required for decomposing the organic matter, and therefore a large-capacity reaction tank is required. In addition to the hydrogen peroxide remaining in the treated water to become COD, the oxygen gas generated by the decomposition of hydrogen peroxide in the process of precipitating and separating the iron salt used as a catalyst with neutrality or alkalinity In order to float the iron hydroxide, it was necessary to decompose the organic matter and then decompose excess hydrogen peroxide.

Also in the method of Japanese Patent Publication No. 59-1120, since filtration, activated carbon treatment and the like are merely added after the above treatment,
There were similar problems.

The present invention is intended to solve the above problems, and an object thereof is to propose a method for treating organic matter-containing wastewater which has a high decomposition rate of organic matter and has a small amount of residual hydrogen peroxide.

[Means for solving problems]

This invention is characterized in that an organic matter-containing wastewater is passed through an activated carbon packed column at SV ¹ to 20 hr ⁻¹ in the presence of hydrogen peroxide and an iron salt, and the organic matter is decomposed by contacting with activated carbon. Is the processing method of.

Examples of the organic matter-containing wastewater to be treated in the present invention include sewage, human waste, waste landfill treatment plant leachate wastewater, incinerator wastewater, organic factory wastewater, etc., and suspended matter is contained in the organic matter-containing wastewater. In the case of pretreatment, solid-liquid separation is carried out by precipitation separation, etc., and in the case of containing easily biodegradable organic matter, biological treatment such as activated sludge method, sprinkling filter method, rotary disk method, anaerobic digestion method, etc. It is desirable to reduce BOD by treatment.

The iron salt used in the present invention is an iron salt generally used in the Fenton method, and includes ferrous salts such as ferrous sulfate and ferrous chloride, ferric sulfate, ferric chloride, and polyferric sulfate. Second of etc.
Iron salts can be used.

The activated carbon is not particularly limited, and granular or powdered activated carbon generally used for water treatment can be used.

As for the treatment method, hydrogen peroxide and iron salts were added to organic matter-containing wastewater, and SV1 to 20 hr ^-1 was added to an activated carbon packed tower in the presence of these.
And then contact with activated carbon to decompose organic substances. A preferable method for contacting is a method of passing an iron salt and hydrogen peroxide into waste water while passing through an activated carbon packed column.

Hereinafter, this method will be described with reference to the drawings. FIG. 1 is a system diagram showing an embodiment of the present invention, in which 1 is a pH adjusting tank,
An activated carbon tower 2 has an activated carbon packed bed 3. 4 is a flocculation tank and 5 is a precipitation tank. As the treatment method, first, raw water is introduced into the pH adjusting tank 1 and an iron salt and a pH adjusting agent are added with stirring to adjust the pH.

The addition amount of iron salt can be determined by the type of organic substance, concentration, injection amount of hydrogen peroxide, reaction time, etc., but the effect increases as the addition amount increases, usually 10 to 100 mg as iron. It is added in the range of / l.

As the pH adjuster, any acid or alkali agent such as hydrochloric acid, sulfuric acid, sodium hydroxide, slaked lime can be used according to the pH of the raw water, and the pH is adjusted to 2.5 to 4.5, preferably 2.5 to 3.5. If the pH exceeds 4.5, iron hydroxide will be deposited in the packed bed of activated carbon and the replacement frequency of activated carbon will increase.

Hydrogen peroxide (H ₂ O ₂ ) is added and mixed in the course of sending the pH-adjusted liquid to the activated carbon tower 2 and then passed through the activated carbon packed bed 3. The amount of hydrogen peroxide added is about 3 to 10 times by weight the organic matter (CODcr) in the waste water, and about 10 to 100 times by weight the added iron. The liquid may be passed upward or downward,
The liquid passing rate is ¹ to 20 hr ^-1 , preferably ¹ to 10 hr ^-1 . The Fenton reaction occurs by using activated carbon as a medium by passing the liquid, and the organic matter is decomposed in a contact time of 5 to 10 minutes, and excess hydrogen peroxide is also decomposed.

The liquid after the reaction in the activated carbon tower 2 is added with an alkali and a polymer flocculant in the flocculation tank 4, mixed and stirred to perform flocculation treatment, and solid-liquid separated in the precipitation tank 5, and the separated liquid is discharged as treated water. .

In the present invention, since the Fenton reaction is carried out using activated carbon as a medium, the decomposition rate of organic matter is increased, and the decomposition of organic matter is completed in a short time of 5 to 10 minutes. Therefore, a decomposition reaction tank for organic substances is not required, and the processing time is significantly shortened. Further, since excess hydrogen peroxide is decomposed by activated carbon, it can be discharged as it is after separating the iron salt. The precipitated iron hydroxide can be dissolved in acid and reused.
When the added amount of iron salt is small, it may be separated with an ion exchange resin. Activated carbon does not need to be regenerated, but it can be replaced when long-term operation causes performance deterioration.

The reason why the decomposition time of the organic matter in the present invention is greatly shortened is that the activated carbon is adsorbed on the surface of the activated carbon and activated iron is adsorbed on the surface of the activated carbon in the reaction of organic matter-H ₂ O ₂ -Fe. It is presumed that the decomposition reaction is accelerated because the activated iron has a high concentration, and the activated carbon has a high density due to packing, and there are many opportunities for contact with activated iron. .

〔Example〕

 Examples of the present invention will be described below.

Comparative example Containing 20 mg / l each of tartaric acid and formalin, CODcr
49.2 mg / l, TOC 16 mg / l raw water, H ₂ O ₂ 500 mg / l and Fe
²⁺ 50 mg / l was added, Fenton treatment was performed at pH 3, and TOC after reaction for 15 minutes and 1.5 hours and residual H ₂ O ₂ after reaction for 1.5 hours were measured. Results are shown in FIG.

As is clear from Fig. 2, the degradability was poor at 15 minutes, and 1.
It can be seen that 200 to 300 mg / l of hydrogen peroxide remains even after the reaction for 5 hours. Further, it can be seen that the decomposition rate of organic matter is affected by the reaction time.

Example 1 Raw water of CODcr 59.2 mg / l containing 20 mg / l each of tartaric acid, isopropyl alcohol and formalin was adjusted to pH 3, and 400 mg / l hydrogen peroxide and Fe at the inlet of the activated carbon tower 2.
While adding a predetermined amount of ²⁺ , water was passed through the activated carbon tower 2 filled with 100 ml of activated carbon at SV 5 hr ^-1 . The activated carbon used was activated carbon Kuraray Coal KW (trademark, manufactured by Kuraray Co., Ltd.), which is used for organic matter adsorption treatment of wastewater. FIG. 3 shows the CODcr of the treated water when the amount of Fe ²⁺ added was changed.

Example 2 10 mg / l of Fe ²⁺ was added to the raw water of the comparative example, and 250 mg / l of hydrogen peroxide was added at the inlet of the activated carbon tower 2 at pH 3 while changing the liquid flow rate to change the contact time. FIG. 4 shows the treated water CODcr and residual hydrogen peroxide when water is passed through the activated carbon tower 2.

As is clear from FIG. 4, the decomposition rate when water is passed through the activated carbon tower 2 is extremely fast, and there is almost no difference when the water content is SV20 or less, but the residual hydrogen peroxide increases when the water content is SV10 or more.

Example 3 20 mg / l of Fe ²⁺ was added to the raw water of the comparative example, and 500 mg / l of hydrogen peroxide was added at the inlet of the activated carbon tower 2 while SV8h at pH 3
Water is passed to the activated carbon tower 2 at r ^-1 , and the amount of activated carbon filled is approximately 6000 times (6
000BV) was passed.

Treated water has pH 3.1-3.2, Fe10-15mg / l, TOC2.5-3.0mg / l
(Raw water 16mg / 1), hydrogen peroxide 0-5mg / 1, short decomposition time (SV8hr ^-1 residence time in activated carbon tower 2
It can be seen that the organic matter can be decomposed efficiently and the excess hydrogen peroxide can be decomposed almost completely regardless of (7.5 minutes).

〔The invention's effect〕

According to the present invention, in the presence of hydrogen peroxide and iron salts of organic matter-containing waste water, the activated carbon packed column is passed at SV ¹ to 20 hr ^-1 ,
Since it was made to contact with activated carbon to decompose organic matter,
Organic matter can be decomposed in a short time, processing time can be shortened, processing equipment can be downsized, and excess hydrogen peroxide can be decomposed almost completely. There is an effect that the processing of is unnecessary.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment, and FIGS. 2 to 4 are graphs showing processing results in the embodiment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 9/00 504 B 7446-4D D 7446-4D

Claims (4)

[Claims] 1. An organic matter-containing wastewater characterized by passing organic wastewater containing organic matter through an activated carbon packed column in the presence of hydrogen peroxide and an iron salt at SV ¹ to 20 hr ^-1 , and contacting with activated carbon to decompose organic matter. Waste water treatment method. 2. The treatment method according to claim 1, wherein the liquid is passed through the packed column of activated carbon while adding hydrogen peroxide and iron salt to the organic matter-containing wastewater. 3. The treatment method according to claim 1 or 2, wherein the liquid is passed through the packed column of activated carbon at a pH of 2.5 to 4.5. 4. The amount of hydrogen peroxide added is 3 to 10 times by weight with respect to the organic matter (CODcr), and 10 to 100 times by weight with respect to the added iron. The processing method according to any one.