CN100412011C - Coking Wastewater Treatment Method Combining Tetravalent Manganese Compound Oxidation, Chemical Precipitation and Biochemistry - Google Patents

Abstract

The coking wastewater treatment method of tetravalent manganese compound oxidation, chemical precipitation, and biochemical combination is characterized in that a tetravalent manganese compound is added to the coking wastewater. Manganese ions are oxidized to obtain recyclable and recyclable tetravalent manganese ions, and then phosphate is added to precipitate and remove ammonia nitrogen in the form of magnesium ammonium phosphate, which can be recycled as slow-release fertilizer; finally, the wastewater treatment is completed by biochemical methods , in the wastewater treatment process of the present invention, the manganese compound is recycled, and there is only a small loss, and the medicaments consumed are mainly sulfuric acid, magnesite and phosphate, so the treatment cost is relatively low.

Description

Coking Wastewater Treatment Method Combining Tetravalent Manganese Compound Oxidation, Chemical Precipitation and Biochemistry

Technical field:

The invention relates to a water treatment method, in particular to a treatment method for coking wastewater.

Background technique:

The commonly used methods for the treatment of coking wastewater mainly include biochemical degradation and chemical coagulation sedimentation after ammonia distillation and dephenol pretreatment. The biochemical method is to remove ammonia nitrogen and remove some phenolic substances through ammonia distillation and dephenol pretreatment, reduce the toxicity of phenolic substances to organisms, enhance the biodegradability of wastewater, and then undergo anaerobic/aerobic (A/O) biological treatment Discharge up to standard; chemical coagulation sedimentation method has low cost, but the removal of pollutants is limited and the effect is not good. It is generally used for pretreatment or advanced treatment of wastewater. Generally speaking, the content of ammonia nitrogen and phenolic substances in coking industry wastewater is high, and phenolic substances are highly toxic, and it is difficult for organisms to survive in a high-concentration phenolic environment. If it is not handled properly, it will endanger the environment and human health. At present, the methods of distilling ammonia and removing phenols are mainly distilling ammonia with alkali and extracting phenols. The cost of ammonia distillation is high and it will easily cause secondary pollution. However, the extraction recovery rate of phenols is not high, so that the content of phenols in wastewater cannot often be reduced to Within the range of biological tolerance, resulting in the failure of the biological treatment system. Coking wastewater is a typical representative of refractory biochemical and refractory wastewater. The pollutants in it decompose very slowly in nature and remain for a long time, which is extremely harmful to the ecological environment. Direct discharge will pose a great threat to the human living environment. It is one of the problems that urgently need to be solved in wastewater treatment. The biggest problem in the treatment of coking wastewater is the stability of the biochemical treatment system, and the high content of COD _Cr , phenols and ammonia nitrogen are the main factors affecting the biochemical treatment, so how to improve the pretreatment effect of coking wastewater dephenolization and deamination key to handling.

The methods currently being studied to treat coking wastewater mainly include catalytic wet oxidation, ozone oxidation, electrochemical method, chlorine and its derivative oxidant oxidation method, adsorption method, photocatalytic oxidation method, ultrasonic activated sludge method, plasma method, etc. , but due to the large consumption of chemicals, materials and energy in the above method for coking wastewater treatment, the treatment cost is high. Therefore, there are great difficulties in the widespread application of these technologies in practical wastewater treatment.

Invention content:

In order to avoid the shortcomings of the above-mentioned prior art, the present invention provides a tetravalent manganese compound oxidation and chemical precipitation method with low cost, simple process, small equipment investment, and suitable for wide application in actual coking wastewater treatment. , Biochemical combined coking wastewater treatment method.

The technical scheme that the present invention solves technical problem adopts is:

The coking wastewater treatment method of the present invention combines oxidation of tetravalent manganese compounds, chemical precipitation, and biochemistry, and its characteristics are:

a. Under acidic conditions, tetravalent manganese compounds oxidize and decompose organic pollutants that are difficult to biodegrade in coking wastewater, and reduce them to produce divalent manganese compounds; under weakly alkaline conditions, divalent manganese ions undergo hydrolysis, precipitation and oxidation. Recover tetravalent manganese for recycling and discharge pre-treated wastewater;

b. Introduce MG ²⁺ into the pretreated wastewater obtained in step a, add PO ₄ ^3- to make the NH ₄ ⁺ in the wastewater form MgNH ₄ PO ₄ and then precipitate; collect the sediment as a slow-release fertilizer, and discharge the supernatant;

d, performing anaerobic or aerobic biochemical treatment on the supernatant obtained in step b.

The inventive method operates as follows:

a. Waste water is injected into the oxidation reactor, and tetravalent manganese compounds are added in the oxidation reactor, and the tetravalent manganese compounds are natural manganese oxides or manganese hydroxides, including pyrolusite, duromanganese ore, manganese ore; or calcined Rhodochrosite, industrial manganese oxide; or tetravalent manganese formed by the reduction of high-valent manganate in wastewater;

b. Add acidic substances into the oxidation reactor, including sulfuric acid, hydrochloric acid, nitric acid or industrial waste acid, adjust the pH value of the wastewater to below 3, and the residence time of the wastewater in the oxidation reactor is 0.5-5 hours to complete the oxidation reaction:

CH ₂ O (organic matter)+Mn(IV)-O+H ⁺ →CO ₂ +H ₂ O+Mn ²⁺

c. The water after the oxidation reaction is injected into the neutralization reactor, and the alkaline substance magnesite or sodium hydroxide is added to the neutralization reactor to make the pH value of the effluent 6-10; there are two ways of neutralization reaction :

One is to aerate and oxygenate the neutralization reactor, while the materials in the neutralization reactor are uniformly mixed and the divalent manganese is oxidized and regenerated to tetravalent manganese; the water containing the regenerated tetravalent manganese enters the sedimentation tank and solidifies liquid separation, discharge the supernatant, and reclaim the precipitate containing the hydroxide of tetravalent manganese;

One is to use mechanical agitation in the neutralization reactor. After the materials are uniformly mixed, they are directly injected into the sedimentation tank, the supernatant is discharged, and then the sediment containing divalent manganese in the sedimentation tank is oxygenated to recover the regenerated tetravalent manganese. manganese hydroxide;

D, the hydroxide of the tetravalent manganese of regeneration is returned to oxidation reactor;

E, the supernatant discharged after the neutralization reaction is injected into the magnesium ammonium phosphate reaction tank, and phosphate is added to the reaction tank to form magnesium ammonium phosphate precipitation, ammonia nitrogen in the water is removed, the precipitate is collected, and the supernatant is discharged;

f. The supernatant obtained in step e is first injected into an anaerobic tank for anaerobic reaction, and then aerobic biochemical treatment is carried out in an aerobic tank.

The feature of the method of the present invention also is that described step a can adopt batch method, arrange two reaction tanks to use alternately, after each reaction tank is full of waste water, add tetravalent manganese compound, and add acid to make the pH of water in the reaction tank If the value is less than 3, stir and react for 2-4 hours to oxidize the organic pollutants; then add magnesite to the reaction tank to make the pH of the water in the reaction tank 7-9, aerate and oxygenate for 1-3 hours, Oxidize the divalent manganese ions produced by the reduction to form tetravalent manganese hydroxide precipitates, stop the aeration and let the precipitation stand for 1-5 hours, collect the precipitates, and discharge the supernatant.

In the present invention, an appropriate amount of tetravalent manganese compounds and acidic substances are added to the wastewater treatment reactor, and under acidic conditions, the organic pollutants react rapidly with the tetravalent manganese compounds, thereby achieving the purpose of purifying the organic pollutants; Manganese ions are hydrolyzed, precipitated, and oxidized under weakly alkaline conditions, and tetravalent manganese is recovered to obtain tetravalent manganese, thereby realizing the recycling of tetravalent manganese compounds in water treatment; after wastewater is neutralized, in the presence of phosphate ions, it will form Magnesium ammonium phosphate is precipitated to remove ammonia nitrogen, while magnesium ammonium phosphate is recovered as slow fertilization, and combined with anaerobic/aerobic biochemical treatment methods to make the wastewater meet the discharge standard.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The present invention is applicable to the treatment of waste water in the coking industry, and the treated waste water fully meets the industrial discharge standard.

2. The process of the present invention is simple and the investment is small; the tetravalent manganese compound as the oxidizing agent can be recycled in the waste water treatment process, and the medicaments consumed are mainly commonly used acids and alkalis, such as sulfuric acid, magnesite, sodium hydroxide, phosphoric acid Salt, etc., cheap chemicals, low waste water treatment cost, good effect, and the precipitate formed by deamination can be recycled as slow-release fertilizer.

3. For coking wastewater, it is difficult to achieve effective purification by using biochemical methods alone. After oxidation of manganese oxide and magnesium ammonium phosphate precipitation treatment, phenol, S ^2- , NH ₃ -N and some other organic substances in coking wastewater are basically eliminated. The inhibitory effect of pollutants on organisms improves the biodegradability of coking wastewater and the stability of the treatment system.

Description of drawings:

Fig. 1 is a process flow of aeration and oxygenation in the neutralization reaction tank of the present invention, and regeneration of tetravalent manganese compounds.

Fig. 2 is the aeration and oxygenation in the sedimentation tank of the present invention, and the process flow of tetravalent manganese compound regeneration.

Fig. 3 is a system diagram of the experimental device of the method of the present invention. It is used to test the removal efficiency, influencing factors, optimal parameters and oxidation regeneration efficiency of refractory biodegradable organic pollutants.

Fig. 4 is the specific implementation process flow diagram of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings by way of specific embodiments:

Detailed ways:

The wastewater to be treated in this embodiment is coking wastewater.

Specifically, follow the steps below:

a. The waste water enters the oxidation reactor. Add excess tetravalent manganese compound in the reactor as an oxidant for organic matter purification reaction. The added tetravalent manganese compound can be pyrolusite, hydromanganese ore, pyrolusite, calcined rhodochrosite or industrial manganese oxide, and the preferred material is natural manganese oxide ore or calcined rhodochrosite. The chemical reaction formula of the tetravalent manganese compound in the oxidation reactor is:

Mn ⁴⁺ +2e→Mn ²⁺

b. Adding acid to the oxidation reactor to adjust the pH of the waste water to <3, and the preferred pH value condition is 1.0-2.0. The acid to be added can be sulfuric acid, hydrochloric acid, nitric acid or industrial waste acid, and the preferred acid is sulfuric acid, which can not only reduce the cost, but also avoid the formation of chlorinated organic compounds. The preferred hydraulic retention time is 2-4 hours.

c. The effluent from the oxidation reactor is injected into the neutralization reactor. Add alkaline substance magnesite to the neutralization reactor. The pH of the effluent is controlled to be 6-10, and the pH of the effluent of the neutralization reactor is preferably 8-10. On the one hand, the pH value of the wastewater after oxidation treatment meets the requirements of wastewater discharge; on the other hand, the dissolved manganese ions are hydrolyzed to form hydroxide precipitates, and aeration and oxygenation are required to oxidize divalent manganese ions to tetravalent manganese weakly alkaline condition. While neutralizing in the neutralization reaction tank, aeration and oxygenation can play a role of mixing on the one hand and oxygenation at the same time, so that the divalent manganese produced by reduction can be oxidized and regenerated into tetravalent manganese. The reaction of the manganese compound in the neutralization reaction pool is:

Mn ²⁺ +2OH ^- → Mn(OH) ₂ ↓

The reaction of manganese compound in the sedimentation tank is:

Mn(OH) ₂ +1/2O ₂ +H ₂ O→Mn(OH) ₄ ↓

After the neutralization reaction and oxidation regeneration are completed, the water enters the sedimentation tank, where the solid-liquid separation is completed to achieve the purpose of recovering tetravalent manganese hydroxide (accompanying drawing 1). It is also possible to use mechanical stirring in the neutralization reaction tank without an oxygenation device, and to install an oxygenation device in the sludge storage tank after the sedimentation tank, and use the sludge storage tank as an oxidation regeneration reaction tank, which can improve the oxygenation efficiency , reduce energy consumption (accompanying drawing 2).

d. The tetravalent manganese hydroxide sludge formed by oxidation and regeneration flows back to the oxidation reactor through the reflux device to supplement the consumed tetravalent manganese compound, so that the redox reaction continues.

e. The effluent from the sedimentation tank is first treated with ammonia distillation, and then enters the magnesium ammonium phosphate (MAP) reaction tank. Add phosphate to the MAP reaction tank, control the molar ratio of PO ₄ ^3- : NH ₄ ⁺ : MG ²⁺ to 1.2: 1.0: 0.9, so that the ammonia nitrogen in the water will be released in the form of MgNH ₄ PO ₄ precipitation, and reduce the impact of ammonia nitrogen on biochemical treatment. impact load, and MgNH ₄ PO ₄ can be recycled as a slow-release fertilizer. The reaction of ammonia nitrogen in the MAP reaction pool is:

NH ₄ ⁺ +Mg ²⁺ +PO ₄ ^3- →MgNH ₄ PO ₄ ↓

f. The supernatant of the sedimentation tank first enters the anaerobic tank for anaerobic reaction, and then enters the aerobic tank for aerobic biochemical treatment.

Example:

Taking the coking wastewater of the coking workshop of the iron and steel complex as the object, the concentration of pollutants in it is phenols (calculated as phenol) 1262mg/L, COD 6821mg/L, NH ₄ -N 4177mg/L, S ^2- 64.3mg/L. Wastewater is treated according to the experimental device in Figure 4, the concentration of pollutants in the effluent is regularly measured, and the removal rate of pollutants is calculated.

The coking wastewater is injected into the oxidation reactor, and excessive natural manganese oxide-pyrolulusite is added to the oxidation reactor.

Sulfuric acid is added to the oxidation reactor to adjust the pH value of the wastewater to 1.5, and the residence time of the wastewater in the oxidation reactor is 2 hours.

The water after the oxidation reaction is injected into the neutralization reactor, and magnesite is added to the neutralization reactor to make the pH value of the effluent 9. During the neutralization reaction, the neutralization reactor is aerated to promote uniform mixing of the materials in the neutralization reactor, and at the same time, the divalent manganese is oxidized and regenerated into tetravalent manganese due to oxygenation.

Water containing regenerated tetravalent manganese enters the sedimentation tank for natural precipitation for 2 hours, solid-liquid separation, and recovery of tetravalent manganese hydroxide, mainly Mn(OH) ₄ or a mixture of Mn(OH) ₄ and Mn(OH) ₂ .

The regenerated tetravalent manganese hydroxide passes through the reflux device and returns to the oxidation reactor.

The effluent after precipitating tetravalent manganese hydroxide is first treated with sodium hydroxide and then injected into the MAP reaction tank, and disodium hydrogen phosphate is added to the MAP reaction tank to form magnesium ammonium phosphate precipitation. Let stand and settle for 2 hours, and the precipitate will be recycled as a slow-release fertilizer.

The precipitated water enters the anaerobic tank for anaerobic reaction, decomposes the macromolecular pollutants that have not been oxidized in pyrolusite into small molecular substances that are easily oxidized, and then enters the aerobic activated sludge tank for aerobic biochemical treatment.

The effluent water quality obtained under the optimal conditions is: phenol<0.5mg/L, NH ₄ -N<15mg/L; total phosphorus<0.5mg/L;COD<200mg/L, S ^2- <1mg/L.

Claims (3)

1. the coking waste water treatment method of tetravalent manganese compound oxidation, chemical precipitation, biochemical associating is characterized in that:

A, under acidic conditions, tetravalent manganese compound will be difficult to the organic pollutant oxygenolysis of biochemical degradation in the coking chemical waste water, reduction produces manganous compound; Under weak basic condition, divalent manganesetion reclaims the tetravalence manganese that is used to recycle after hydrolysis, precipitation and oxidation, discharges pretreated waste water;

B, in step a gained pretreated waste water, introduce Mg ²⁺, add PO ₄ ^3-Make the NH in the waste water ₄ ⁺Form MgNH ₄PO ₄Postprecipitation; The collecting precipitation thing is discharged supernatant liquor as slow-release fertilizer;

D, step b gained supernatant liquor is carried out anaerobism or aerobic biochemical handle.

2. method according to claim 1 is characterized in that operating as follows:

A, waste water inject oxidation reactor, add tetravalent manganese compound in oxidation reactor, and described tetravalent manganese compound is natural Mn oxide or manganese oxyhydroxide, comprises pyrolusite, psilomelane, manganite; Or for calcining rhodochrosite, industrial Mn oxide; Or be the high price manganate in waste water, reduce formation tetravalence manganese;

B, add acid in oxidation reactor, comprise sulfuric acid, hydrochloric acid, nitric acid or industrial waste acid, the pH value of regulating waste water is below 3, and waste water residence time in oxidation reactor is 0.5-5 hour, finishes oxidizing reaction:

C, the water after oxidizing reaction inject neutralization reactor, add alkaline matter magnesia or sodium hydroxide to neutralization reactor, make water outlet pH value be 6-10; The mode of neutralization reaction has two kinds:

A kind of is aeration aerating in neutralization reactor, and material is a tetravalence manganese by mixed uniformly while bivalent manganese oxidation regeneration in the neutralization reactor; The water that contains regeneration tetravalence manganese enters in the settling tank solid-liquid separation after the natural sedimentation, discharges supernatant liquor, reclaims the throw out of the oxyhydroxide that contains tetravalence manganese;

A kind of is to adopt mechanical stirring in neutralization reactor, and material directly injects settling tank after by uniform mixing, discharges supernatant liquor, again the throw out that contains bivalent manganese in the settling tank is carried out oxygenation, the oxyhydroxide of the tetravalence manganese of reclaiming;

The oxyhydroxide of d, regenerated tetravalence manganese is back to oxidation reactor;

The supernatant liquor of discharging after e, the neutralization reaction is handled through ammonia still process earlier, and the magnesium ammonium phosphate reaction tank that reinjects adds phosphoric acid salt in described reaction tank, forms magnesium ammonium phosphate sediment, removes ammonia nitrogen in the water, and the collecting precipitation thing is discharged supernatant liquor;

F, step e gained supernatant liquor is injected earlier anaerobic pond carry out anaerobic reaction, in Aerobic Pond, carry out aerobic biochemical then and handle.

3. method according to claim 1, it is characterized in that described step a adopts interrupter method, arrange that two reaction tanks are used alternatingly, each reaction tank is after being full of waste water, add tetravalent manganese compound, and add pH value that acid makes water in the reaction tank less than 3, stirring reaction 2-4 hour, make the organic pollutant oxidation; Adding magnesia again in this reaction tank makes the pH value of water in the reaction tank be 7-9, aeration aerating 1-3 hour, the divalent manganesetion oxidation that reduction is produced generates the precipitation of hydroxide of tetravalence manganese, stops to staticly settle 1-5 hour behind the aeration collecting precipitation thing, discharge supernatant liquor.

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