JPS58174297A - Treatment of waste water from desulfurization of waste gas - Google Patents

Abstract

PURPOSE:To remove the COD component in waste water from desulfurization of waste gas thoroughly, by subjecting said waste water successively to an alkali flocculating and settling treatment, a biological treatment, a filtration treatment, and a treatment with a phenolic synthetic adsorptive resin and a specific weakly basic anion exchange resin. CONSTITUTION:The pH of waste water from desulfurization of waste gas is controlled to a high alkalinity region and a flocculating agent is added thereto to form floc which is settled and removed. The water is subjected to a biological treatment such as activated sludge treatment followed by a filtration treatment such as ordinary sand filtration or the like. In succession, the water is passed successively through a synthetic adsorptive resin such as a macroporous type resin consisting basically of phenol and a microporous type weakly basic anion exchange resin consisting basically of styrene-divinyl benzene, whereby the water is brought into contact with said resins. Order of the passage may be reversed in this case so as to pass the water first through the weakly basic anion exchange resin.

Description

[Detailed description of the invention] This invention relates to a treatment method for purifying wastewater.

When coal or heavy oil is burned in a boiler or the like, the exhaust gas is desulfurized by catalyzing it with an absorbing liquid such as an alkaline solution, and at this time, flue gas desulfurization wastewater is generated. Since such wastewater contains a large amount of suspended solids and organic matter, it cannot be discharged as is, so conventional treatments such as alkaline coagulation and sedimentation treatment and biological treatment have been carried out9.

However, even with such treatment, in reality, some COD components still remain in the treated water, and they cannot be removed due to wastewater regulations.
As it is, it is difficult to discharge the wastewater as it is, and the development of a treatment method that can minimize and efficiently suppress the content of such OOD components in flue gas desulfurization wastewater is a major issue in the industry.

Therefore, the present inventors investigated what causes COD components and found that sulfur contained in coal and heavy oil becomes various compounds and dissolves in wastewater to become COD components. In addition, since biological treatment was performed, it was found that OOD components derived from the organisms used at that time were present.

The inventors of the present invention have conducted intensive studies on a treatment method that should completely remove both the sulfur compound-derived and biologically-derived COD components. #1 The OOD component in the wastewater can be almost completely removed by contacting it with a styrene-divinylbenzene-based weakly basic ion exchange resin, or by contacting it in the reverse order. Heading: The present invention has been completed.

All in all, the present invention processes flue gas desulfurization wastewater through ■ a first step of performing alkali and potassium coagulation and precipitation treatment, ■ a second step of performing biological treatment, and ■
A third step of carrying out f-filtration; and (a) a fourth step of contacting a phenol-based synthetic adsorption resin and a styrene-divinylbenzene-based weakly basic anion exchange resin in this order or in the reverse order. This is a method for treating desulfurization wastewater.

The method of the present invention will be described in more detail below.

The so-called flue gas desulfurization wastewater generated when exhaust gas generated by burning coal or heavy oil is cleaned with an alkaline solution contains pollutants such as suspended solids, soluble inorganic substances, and soluble organic substances.

In the present invention, the flue gas desulfurization wastewater is first brought into contact with a dirt resin and a weakly basic anion exchange resin, which can be removed by conventional general purification methods, such as alkaline coagulation and precipitation treatment, biological treatment, and e-supertreatment. , CO, which was previously extremely difficult to remove.
This is a purification treatment method that almost completely removes component D.

The first step in the present invention, alkaline coagulation and precipitation treatment, involves adjusting the volume of normal wastewater to a high alkaline range, and adding an inorganic flocculant and a polymer flocculant to precipitate the 7Q. Most of the bank metals in wastewater can be removed by this treatment method. Especially Sumifloc HM-Lead r and Sumifloc HM-a (both manufactured by Sumitomo Chemical Co., Ltd.), 6A-.

increases significantly.

In addition, the second step, biological treatment, involves performing the usual activated sludge method and one-bed watering method, and its purpose is to remove OOD components in wastewater, but recently it has been It is possible to reduce dissolved oxygen and simultaneously perform denitrification through biological treatment, and this method can be used.

Next, the third step, r-overtreatment, is the usual -f-bread or sand-
Anthracite multi-layer filtration is carried out, and there is no problem whether it is gravity type or pressurized type.

The treated wastewater that has completed the third step is then sequentially passed through and brought into contact with a synthetic adsorption resin and a weakly basic anion exchange resin in the fourth step.

In this case, the order of water flow can be reversed, and the weakly basic anion exchange resin is passed first, and then the synthetic adsorption resin is passed through for contact.〇- As the synthetic adsorption resin used in the fourth step. is preferably a macroporous resin having phenol as a resin matrix, such as Duolite B-m, Duolite 5-76/
, Duolite 5-77/ (both manufactured by Diamond Jam Rock) are effective. These resins can completely adsorb and remove biologically derived 00D components.

In addition, as a weakly basic anion exchange resin, styrene-
Macroporous resins with divinylbenzene as the resin matrix are preferred, such as Duolite A-777, Duolitem-J75 (both manufactured by Diamond Raym Rock Co., Ltd.), Diaion W Mu-θ, and Diaion WA-J.
θ (both Mitsubishi Kasei products), Amberlight IR Mu-93
, Amber Rai) IR Mutada (both Organo products)
etc. are valid. These 11. By adsorbing and removing sulfur compounds with the resin, it is possible to almost completely adsorb and remove COD components derived from the sulfur compounds. - As described above, according to the method of the present invention, OOD present in flue gas desulfurization wastewater
The components can be almost completely removed.

When using the phenol-based synthetic adsorption resin and the styrene-divinylbenzene-based weakly basic anion exchange resin used in the fourth step, it is preferable to use hydrochloric acid as the exchange group, and more preferably SO rather than the Cl type. , type is preferred.

OH type resins are affected by high levels of chlorine ions, sulfate ions, etc. in wastewater, but salt wrinkle resins have far less of this effect and can efficiently remove COD components even from wastewater with high salt concentrations. It can be adsorbed well.

To regenerate these resins on which COD components have been adsorbed after passing through the resin, the COD components can be easily desorbed by passing an aqueous solution containing an alkaline agent such as thorium hydroxide through the resin. The regenerating agent used is an aqueous solution having a concentration equivalent to or more than the equivalent amount of the alkali consumed by the resin, usually /~/j% by weight.

The resin from which the COD component has been desorbed is washed by passing clear water such as treated water or industrial water to extrude and wash the remaining alkaline agent, and then washed with mineral acid to convert the exchange group of the resin into a salt type.

In these cases, the mineral acid used is, for example, hydrochloric acid or sulfuric acid, and the mineral acid at a concentration of /~/j% by weight is brought into contact with the resin to change the exchange group of the resin to C, Q type or 604 type. In order to remove the mineral acid remaining in the resin layer made into salt form with mineral acid, the resin layer is extruded and washed again with clear water such as treated water or industrial water.

The resin that has been regenerated in this way is used again for wastewater treatment.

Further, it is preferable to add sulfuric acid, hydrochloric acid, etc. to the wastewater flowing to these resin towers to adjust its quality. In particular, it is preferable to adjust i 041 with sulfuric acid when using the 804 type exchange group of the resin, and with hydrochloric acid when using the On type exchange group. The voice in this case is /~6, preferably 2~j
If 2 is lower than 7, the resulting treated water storage will drop significantly, which is not preferable. In addition, since carbonate and bicarbonate roots are present in flue gas desulfurization wastewater, if the wastewater exceeds 6 tsubo, carbon dioxide gas is generated when water passes through the salt-type resin layer and rises in the resin layer. It is preferable/unlikely to cause a channeling phenomenon.

Furthermore, as mentioned above, in the present invention, since a salt-type resin is used to remove COD, the pH of the outlet water can be maintained at approximately the adjusted value even if the wastewater whose pH has been adjusted is passed through the resin layer. , COD can be removed within an efficient range.The contact between wastewater and resin can be carried out by passing the wastewater through a resin tower filled with resin. It is possible to use only one column for each anion exchange resin, but if you connect a series of two or more columns and water is passed in a so-called merry-go-round method, water can be passed until the species is saturated with complete silkworms, and the treatment per unit amount of resin is reduced. This is preferable because the amount of water can be increased.

As described above, the present invention can almost completely remove COD components from flue gas desulfurization wastewater generated when treating gas generated by burning coal or heavy oil, which was completely difficult to treat using conventional treatment methods. It can be done.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the method of the present invention is not limited to the following examples as long as it does not go beyond the scope of the invention.

Example: Wet flue gas desulfurization wastewater from a coal boiler was normally treated using a heavy metal collector Sumifloc HM-Lead r, an inorganic flocculant ferric chloride, and a polymer flocculant Sumifloc Fmu-jθ (product of Sumitomo Chemical Co., Ltd.) Perform alkali coagulation precipitation treatment and remove this supernatant water.
Activated sludge treatment is carried out. Subsequently, the supernatant water from the activated sludge treatment tank was passed through a sand filter tower to remove suspended solids.

The pH of the hydrogen peroxide was adjusted to 41 with sulfuric acid, and then a resin tower filled with styrene-divinylbenzene-based weakly basic anion exchange resin DUOLY) A-37t as SO4 type was added. Light 8-317
These were sequentially brought into contact with a refill tower packed with type 804.

The resin tower has an inner diameter of 2 tons and a height of /! 001111 PVC column was filled with resin at jθθ−, and water was passed at a water flow rate of 5v=j(nr′). The COD concentration in the final resin tower outlet water was less than 1 ppm.

Regeneration of the resin was performed with wt% sodium hydroxide at a regeneration level of /, 2θp/It-R after back washing for both, and after washing with water, the resin was regenerated with jw weight sulfuric acid at a regeneration level of /θθf/It-R of 80%.
It was made into type 4. This was washed with water and then passed through water again.

Example - Water flow was carried out under exactly the same conditions as on the actual flow side except that the order of contact between Duolite A-371 and Duolite 8-87 was reversed, but the COD of the treated water was still 9 degrees. j
It was less than p%.

Comparative Example: Conducted under exactly the same conditions as Example, except that 37g of Duolite A-3 was filled in place of Duolite 8-317 during water flow, and Duolite A-j7ff was connected in series. However, the COD concentration in the treated water did not fall below /jp-. This is thought to be because biologically derived COD components were not removed.

Comparative example - When passing water, Duolite 8-5 7 was filled instead of Duolite A-371, and Duolite B-317 was filled with 2
The process was carried out under the same conditions as in Example except that the columns were connected in series. As a result, CODI in the treated water! If is /θpp
It did not fall below m. This is COD derived from sulfur compounds.
I think this is because it was not removed.

June 1981 J1-] Director General of the Office of the Chief Justice Shimada Tsumaikaku Tono 1 Incident Indication Show@+SN+ Special Application No. 68482 ゝ'' 2
Investigation Q) Name ZejN Exhaust Unbalanced Desulfurization Wastewater Treatment Method 3, hf+ +l: 4--"JR Address: Kita iQ51' [l15, Higashi-ku, Osaka City, '] Column 6 for detailed explanation of the invention in the specification, Details of the amendment (1) In the fourth line of 11I from the bottom of the specification, the word "contact" is corrected to "contact."

(2) On page 8, line 118, it says “adjust a” on page 1.
"Adjust H".

(3) Add the following Example 8 to the same No. tt -377
The desulfurization wastewater was treated under the same conditions as in Example 1 except that the C0D of the treated water was 5.
pp! It was below II. "that's all

Claims (1)

[Claims] The flue gas desulfurization wastewater is treated with ■the first step of alkaline coagulation and precipitation treatment, ■the second step of biological treatment, the third step of 01-cycle treatment, and ■phenol-based synthetic adsorption resin and styrene-divinylbenzene-based weak basic anion. Method 0 for treating flue gas desulfurization wastewater, characterized by sequentially carrying out the fourth step of contacting ion exchange resins in this order or in the reverse order.