A method for autotrophic denitrification of wastewater using desulfurization waste liquid as electron donor

Abstract

The invention discloses a wastewater autotrophic denitrification method using desulfurization waste liquid as an electron donor, and belongs to the field of coking desulfurization waste liquid resource utilization and wastewater denitrification. It uses thiosulfate and thiocyanate in the desulfurization waste liquid as electron donors to carry out sulfur autotrophic denitrification to remove nitrate nitrogen in the wastewater. The invention uses reduced sulfur in the desulfurization waste liquid as an electron donor for sulfur autotrophic denitrification to remove nitrate nitrogen in the wastewater so that the effluent meets the discharge standard or improves the purity of product salt in zero discharge of wastewater (such as coking wastewater). It has the characteristics of not requiring an external organic carbon source, being able to use a variety of sulfur sources, having low operating costs, high denitrification efficiency, and low sludge production, and realizes waste treatment with waste, and reduces the cost of pollutant disposal and wastewater denitrification.

Description

Technical Field

[0001] The invention belongs to the technical field of coking desulfurization waste liquid resource utilization and wastewater denitrification, and specifically relates to a wastewater autotrophic denitrification method using desulfurization waste liquid as an electron donor. Background Art

[0002] Coking coal contains 0.5% to 1.2% sulfur. 20% to 45% of the sulfur enters the coal gas in the form of sulfide and forms impurities in the coal gas together with NH3 and HCN. In order to avoid H2S corrosion on equipment pipelines, coking coal gas desulfurization must be carried out. At present, coking enterprises widely use HPF method (using hydroquinone, PDS bicyclic phthalocyanine cobalt sulfonate and ferrous sulfate as catalysts), ammonia as alkali source and PDS method (using sodium carbonate as alkali source) and other wet oxidation technologies for desulfurization. This technology mainly removes H2S from coal gas. After absorption, catalytic oxidation and regeneration processes, elemental S can be recovered as the main product. However, waste liquids such as sulfate, thiosulfate and thiocyanate will be generated during the desulfurization process. When these salts accumulate to a certain level (≥250 g / L), the desulfurization efficiency will be seriously reduced. In order to ensure that the desulfurization process continues to proceed efficiently, fresh desulfurization liquid must be added and some high-concentration desulfurization liquid must be discharged at the same time, resulting in a large amount of coking desulfurization waste liquid.

[0003] The COD in the above HPF desulfurization wastewater is > 68×10 3 mg / L, thiocyanate greater than 19×10 3 mg / L, thiosulfate greater than 13×10 4 mg / L, the COD, ammonia nitrogen and salinity of desulfurization wastewater are extremely high, and it cannot be directly treated biochemically. It is a pollutant with great harm. Traditional desulfurization wastewater treatment methods include evaporation recrystallization, high-temperature combustion acid production, etc. These methods need to be implemented under high temperature and high pressure conditions, and the operating costs are extremely high. At the same time, the salts produced are difficult to sell and reasonably use due to their low purity. 2 / O The effluent from the biochemical process contains 80~100 mg / L of nitrate nitrogen, which exceeds the discharge standard. It is necessary to install a post-denitrification unit and add expensive organic carbon sources (such as sodium acetate trihydrate) to meet the standard. Summary of the invention

[0004] The object of the present invention is to provide a method for autotrophic denitrification of wastewater using desulfurized waste liquid as an electron donor, which applies the desulfurized waste liquid to the deep denitrification of wastewater, improves the efficiency of autotrophic denitrification of wastewater and reduces the operating cost of wastewater denitrification, and ensures the stable operation of the sulfur autotrophic denitrification system by optimizing various process parameters.

[0005] To achieve the above-mentioned purpose, the technical solution of the present application is: a wastewater autotrophic denitrification method using desulfurized waste liquid as an electron donor, which utilizes reduced sulfur (mainly including thiosulfate and thiocyanate) in the desulfurized waste liquid as an electron donor to carry out sulfur autotrophic denitrification; specifically comprising:

[0006] Pretreatment step: remove solid impurities in the desulfurization waste liquid, make the desulfurization waste liquid an ideal electron donor for autotrophic denitrification, and improve the denitrification efficiency;

[0007] Influent adjustment step: introduce nitrate wastewater with a NO3--N concentration of 80-100 mg / L into the regulating tank, and the effluent from the regulating tank enters the sulfur autotrophic reactor;

[0008] Dosing and adjustment step: the pretreated desulfurization waste liquid is placed in a mixed dosing box, stirred evenly, and sent to the sulfur autotrophic reactor to provide denitrification electron donors;

[0009] pH adjustment step: an acid and alkali dosing box containing sodium hydroxide and sulfuric acid is used to prepare alkali solution and acid solution with concentrations of 8-10 mol / L and 1-2 mol / L, respectively, and send them to the sulfur autotrophic reactor;

[0010] The sulfur autotrophic denitrification step is as follows: the sulfur autotrophic denitrification sludge after acclimation is placed in the sulfur autotrophic reactor, the thiocyanate content in the sulfur autotrophic reactor is controlled to be below 2-2.5 mM, the temperature is 15-25° C., the dissolved oxygen is controlled to be below 0.05 mg / L, the pH is 6.6-7.5, and the hydraulic retention time is 2-10 h;

[0011] The precipitation step is as follows: the sewage treated by the sulfur autotrophic reactor enters the sedimentation tank for solid-liquid separation, and the precipitated sludge is returned to the sulfur autotrophic reactor to maintain the sludge concentration, so as to ensure that the sludge on the wall of the sedimentation tank is removed while the effluent meets the standard or improves the purity of the salt of the zero-discharge product of coking wastewater.

[0012] Furthermore, the specific implementation method of the pretreatment step is: first remove solid particle impurities with relatively large density (ρ>1) in the desulfurization waste liquid through an inclined plate sedimentation tank, and then remove suspended solid particles (ρ≤1) in the desulfurization waste liquid through a multi-media filter.

[0013] Furthermore, the regulating tank monitors the nitrate-nitrogen concentration of the inlet water through the NO3--N detector in the tank, and the sedimentation tank monitors the nitrate-nitrogen concentration of the outlet water through the NO3--N detector in the tank.

[0014] Furthermore, a desulfurized waste liquid agitator is provided in the mixing and dosing box, and the desulfurized waste liquid after being evenly stirred is sent to the sulfur autotrophic reactor through a dosing variable frequency pump.

[0015] Furthermore, a rotary scraper is provided at the upper part of the sedimentation tank (to scrape off the sludge at the upper part of the sedimentation tank), a sludge agitator is provided at the lower part, and the lower part of the sedimentation tank is a conical structure with a slope set at 60°~70°.

[0016] Furthermore, the sulfides in the desulfurization waste liquid mainly include sulfate, thiosulfate and thiocyanate, and the ratio of thiosulfate: thiocyanate: influent nitrate nitrogen is 30:5:7~36:4:7.

[0017] Furthermore, the sulfur autotrophic denitrification sludge is taken from anaerobic digestion sludge or activated sludge, and the sludge concentration is 3000-5000 mg / L. After cultivation and domestication, it can completely remove NO3 in a hydraulic retention time of 2-10 h. - -Wastewater with N concentration of 100 mg / L.

[0018] Furthermore, the sulfur autotrophic reactor is provided with a pH meter, a temperature meter and a sulfur autotrophic denitrification agitator, the stirring blade of the agitator is a three-blade plug flow type, the ratio of the stirring blade radius to the sulfur autotrophic reactor radius is 0.6 to 0.65, and the mechanical stirring intensity is 3 to 8 w / m 3 within the range.

[0019] As a further step, when the pH in the sulfur autotrophic reactor is lower than 6.6, the acid-base dosing pump automatically adds alkali solution, and when the pH is higher than 7.5, the acid-base dosing pump automatically adds acid solution.

[0020] As a further step, the inlet NO3--N detector, pH meter, temperature meter, outlet NO3--N detector, desulfurization waste liquid dosing frequency conversion pump, acid and alkali dosing pump are all connected to the PLC controller, and the PLC controller is connected to the industrial control computer to display the parameter information.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention utilizes reduced sulfur in the desulfurization waste liquid as an electron donor to carry out sulfur autotrophic denitrification to remove nitrate nitrogen in the wastewater. The device used has a simple structure, a high degree of automation, and strong operability.

[0023] 2. The present invention applies the difficult-to-treat coking desulfurization waste liquid to wastewater denitrification treatment, thereby achieving waste treatment with waste; it has the characteristics of not requiring an external organic carbon source, being able to utilize a variety of sulfur sources, having low operating costs, high denitrification efficiency, and low sludge production, thereby greatly reducing the cost of pollutant disposal and wastewater denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the wastewater autotrophic denitrification system in the embodiment.

[0025] Description of the numbers in the figure: 1. Regulating tank, 2. Influent NO3 - -N detector, 3. Wastewater pump, 4. Acid and alkali dosing box, 5. Acid and alkali dosing pump, 6. Mixing dosing box, 7. Dosing frequency conversion pump, 8. pH meter, 9. Temperature meter, 10. Sulfur autotrophic reactor, 11. Sludge return pump, 12. Outlet NO3 - -N detector, 13. sedimentation tank, 14. PLC controller, 15. industrial computer, 16. inclined plate sedimentation tank, 17. filter pump, 18. multi-media filter. Specific implementation methods

[0026] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application, that is, the embodiments described are only part of the embodiments of the present application, not all of the embodiments.

[0027] like Figure 1 As shown, the present invention provides a wastewater autotrophic denitrification method using desulfurized waste liquid as an electron donor, the method is implemented in a wastewater autotrophic denitrification system, the wastewater autotrophic denitrification system comprises a pretreatment system and a main reaction system; the pretreatment system comprises an inclined plate sedimentation tank and a multi-media filter, the inclined plate sedimentation tank is connected to the liquid inlet of the multi-media filter through a filter pump; the main reaction system comprises a regulating tank, a mixing dosing box, an acid and alkali dosing box, a sulfur autotrophic reactor, a sedimentation tank and a PLC controller; the regulating tank is provided with a nitrate wastewater inlet, and its wastewater outlet is connected to the water inlet of the sulfur autotrophic reactor through a wastewater pump The liquid inlet of the mixed dosing box is connected to the liquid outlet of the multi-media filter, and the liquid outlet of the mixed dosing box is connected to the liquid inlet of the sulfur autotrophic reactor through a dosing frequency conversion pump; the acid and alkali dosing box is connected to the dosing inlet of the sulfur autotrophic reactor through an acid and alkali dosing pump, and the water outlet of the sulfur autotrophic reactor is connected to the water inlet of the sedimentation tank, and the mud outlet of the sedimentation tank is connected back to the reflux port of the sulfur autotrophic reactor; the PLC controller adjusts the desulfurization waste liquid dosing frequency conversion pump and the acid and alkali dosing pump according to the parameters of the inlet NO3--N detector, pH meter, temperature meter, and outlet NO3--N detector, and displays the parameter information on the industrial computer. Example

[0028] The method of the present invention is used to treat nitrate wastewater, and the specific water quality of the nitrate wastewater is: pH: 7.0±0.5, COD: 200±6 mg / L, nitrate nitrogen: 100±1.2 mg / L, nitrite nitrogen: 0 mg / L; the specific implementation case is as follows:

[0029] The domesticated sulfur autotrophic denitrification sludge is put into the sulfur autotrophic reactor to make the inoculated sludge concentration reach 3000-5000 mg / L, and the nitrate wastewater in the regulating tank is introduced into the sulfur autotrophic reactor;

[0030] The temperature of the sulfur autotrophic reactor is maintained between 15 and 25 °C, depending on the influent NO3 - -N concentration controls the dosage of desulfurization waste liquid, so that the mass ratio of thiosulfate: thiocyanate: nitrate nitrogen entering the reactor is 44:7:10; turn on the sulfur autotrophic denitrification agitator, and its mechanical stirring intensity ranges from 3 to 8 w / m 3 , so that the sulfur autotrophic sludge and the desulfurization waste liquid are fully mixed; the pH in the sulfur autotrophic reactor is maintained between 6.6 and 7.5, when the pH is lower than 6.6, the acid and alkali dosing pump automatically adds alkali solution, and when the pH is higher than 7.5, the acid and alkali dosing pump automatically adds acid solution;

[0031] The sewage treated by the sulfur autotrophic reactor enters the sedimentation tank for solid-liquid separation, and the precipitated sludge flows back to the sulfur autotrophic reactor through a reflux pump.

[0032] The experimental results show that the COD (mainly contributed by thiosulfate and thiocyanate) and nitrate nitrogen in the influent were 288 mg / L and 100 mg / L respectively; the nitrate nitrogen in the effluent of the sedimentation tank was 1.29 mg / L, and the nitrite nitrogen, thiocyanate and thiosulfate were all below the detection limit, and the COD was 12 mg / L; the removal rates of nitrate nitrogen and COD were 98.6% and 95.8% respectively, and thiosulfate and thiocyanate acted as electron donors for sulfur autotrophic denitrification.

[0033] Table 1 Concentration of various substances in effluent (mg / L)

[0034] <![CDATA[NO 2- -N]]> <![CDATA[NO 3- -N]]> <![CDATA[SO4 2- ]]> <![CDATA[SCN - ]]> <![CDATA[S2O3 2- ]]> COD pH Water Intake 0 100 1685 70 440 288 8.15 Water 0 1.29 2555 0 0 12 6.89 Removal rate / 98.6% / 100% 100% 95.8% /

[0035] The above description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is obvious that the above invention can be subjected to many changes and variations. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor, characterized in that: The method uses reduced sulfur in desulfurized waste liquid as an electron donor to carry out sulfur autotrophic denitrification, wherein the sulfide in the desulfurized waste liquid includes sulfate, thiosulfate and thiocyanate, and the ratio of thiosulfate: thiocyanate: influent nitrate nitrogen is 30:5:7-36:4:7; specifically comprising: Pretreatment step: removing solid impurities from desulfurization waste liquid; Influent adjustment step: introduce nitrate wastewater with a NO3--N concentration of 80-100 mg / L into the regulating tank, and the effluent from the regulating tank enters the sulfur autotrophic reactor; Dosing adjustment step: the pre-treated desulfurized waste liquid is placed in a mixed dosing box, stirred evenly, and sent to the sulfur autotrophic reactor to provide denitrification electron donors; a desulfurized waste liquid agitator is provided in the mixed dosing box, and the desulfurized waste liquid after stirring evenly is sent to the sulfur autotrophic reactor through a dosing variable frequency pump; pH adjustment step: an acid and alkali dosing box containing sodium hydroxide and sulfuric acid is used to prepare alkali solution and acid solution with concentrations of 8-10 mol / L and 1-2 mol / L respectively, and send them to the sulfur autotrophic reactor; The sulfur autotrophic denitrification step comprises: placing acclimated sulfur autotrophic denitrification sludge in a sulfur autotrophic reactor, wherein the thiocyanate content in the sulfur autotrophic reactor is controlled to be below 2-2.5 mM, the temperature is 15-25° C., the dissolved oxygen is controlled to be below 0.05 mg / L, the pH is 6.6-7.5, and the hydraulic retention time is 2-10 h; the sulfur autotrophic denitrification sludge is taken from anaerobic digestion sludge or activated sludge, and the sludge concentration is 3000-5000 mg / L; The precipitation step is as follows: the sewage treated by the sulfur autotrophic reactor enters the sedimentation tank for solid-liquid separation, and the precipitated sludge is returned to the sulfur autotrophic reactor to maintain the sludge concentration, so as to ensure that the sludge on the wall of the sedimentation tank is removed while the effluent meets the standard or improves the purity of the salt of the zero-discharge product of coking wastewater.

2. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: The specific implementation method of the pretreatment step is: firstly remove the solid particle impurities with high density in the desulfurization waste liquid through the inclined plate sedimentation tank, and then remove the suspended solid particles in the desulfurization waste liquid through the multi-media filter.

3. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: The regulating tank monitors the inlet nitrate nitrogen concentration through the inlet NO3--N detector in the pool, and the sedimentation tank monitors the outlet nitrate nitrogen concentration through the outlet NO3--N detector in the pool.

4. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: The upper part of the sedimentation tank is provided with a rotary scraper, the lower part is provided with a sludge agitator, and the lower part of the sedimentation tank is a conical structure with a slope set at 60°~70°.

5. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: The sulfur autotrophic reactor is provided with a pH meter, a temperature meter and a sulfur autotrophic denitrification agitator. The stirring blade of the agitator is a three-blade plug flow type, the ratio of the stirring blade radius to the sulfur autotrophic reactor radius is 0.6-0.65, and the mechanical stirring intensity is 3-8 w / m 3 within the range.

6. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: When the pH in the sulfur autotrophic reactor is lower than 6.6, the acid-base dosing pump automatically adds alkali solution, and when the pH is higher than 7.5, the acid-base dosing pump automatically adds acid solution.

7. The method for autotrophic denitrification of wastewater using desulfurization waste liquid as an electron donor according to claim 1, characterized in that: The inlet NO3--N detector, pH meter, temperature meter, outlet NO3--N detector, desulfurization waste liquid dosing frequency conversion pump, and acid and alkali dosing pump are all connected to the PLC controller, which is connected to the industrial control computer to display various parameter information.

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