Resourceful treatment method and treatment system for sludge pyrolysis water

Abstract

The invention discloses a resourceful treatment method and a resourceful treatment system for sludge pyrolysis water, and relates to the technical field of wastewater treatment. Comprising the following steps: removing insoluble impurities and oil from the sludge pyrolysis water to obtain a solid phase and a water phase; after the water phase is subjected to electrocatalytic oxidation treatment, a water body is aerated to be balanced, sediment is obtained through sedimentation, and in the electrocatalytic oxidation treatment, a BDD electrode is used as an anode, and a metal electrode is used as a cathode; carrying out low-temperature evaporation on the effluent to obtain a concentrated solution, and preparing the concentrated solution into a biological carbon source; and carrying out biochemical treatment and / or membrane filtration treatment on the effluent subjected to low-temperature evaporation treatment. According to the resourceful treatment method disclosed by the invention, toxic and harmful substances can be removed through electrocatalytic oxidation treatment, the COD (Chemical Oxygen Demand) of sewage is reduced, and the B / C ratio is increased; meanwhile, the ammonia nitrogen content is reduced through low-temperature evaporation and concentration, and B / C of a biological carbon source can be larger than or equal to 0.64; the COD and ammonia nitrogen content are further reduced through biochemical treatment and / or membrane filtration treatment, so that the effluent is purified until the emission requirement is met.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically, to a resource treatment method and treatment system for sludge pyrolysis water. Background Art

[0002] Sewage contains organic matter and pollutants, and has the dual attributes of "pollution" and "resources". If it is not effectively treated, it will cause serious environmental pollution and waste of resources. In view of the difficulties in sludge treatment and disposal, we aim to make harmless treatment and use resource utilization as a means to make up for the shortcomings of sludge disposal. The recycling of energy and materials in sludge is an important way to achieve synergistic efficiency in reducing pollution and carbon emissions in sewage treatment plants.

[0003] Pyrolysis carbonization technology is a green thermal treatment technology without secondary pollution. It has high energy utilization rate, high volume reduction rate, low operating cost, and is significant for CO2 emission reduction. During the pyrolysis process of sludge, sludge charcoal, tar and gas products will be produced. After condensation and gas-liquid separation, the gas product is obtained as an oil-water mixture, and after further oil-water separation, brown sludge pyrolysis water with a strong odor is obtained. The chemical composition of sludge pyrolysis water is complex, COD (chemical oxygen demand) is high, and it contains toxic and harmful substances such as phenols, aldehydes, soluble tar, high ammonia nitrogen concentration, and extremely poor biodegradability. It is difficult to directly biochemically treat sludge pyrolysis water. Conventional pretreatment such as micro-electrolysis, ozone, coagulation and sedimentation operations cannot effectively improve the B / C (BOD5 / COD) value of sewage and remove ammonia nitrogen to achieve biochemical treatment in actual engineering applications.

[0004] Chinese patent CN116332392A discloses a method for resource treatment of municipal sludge pyrolysis water. After the municipal sludge pyrolysis water is treated with oil and water separation, it is sequentially treated with alkalization pretreatment, deammoniation treatment, mechanical vapor recompression treatment (MVR), membrane treatment and / or biochemical treatment, and can be directly connected to the sewage treatment plant. During the treatment process, oil products, ammonia nitrogen and biological carbon sources are separated, thereby realizing the resource treatment of municipal sludge pyrolysis liquid. However, the biodegradability of the product obtained is poor, with a B / C value of only 0.38. When used as a biological carbon source, the proportion of biodegradable organic matter still needs to be improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects and shortcomings of low B / C of biological carbon sources prepared by sludge pyrolysis water in the prior art, and to provide a resource treatment method for sludge pyrolysis water.

[0006] Another object of the present invention is to provide a resource processing system for sludge pyrolysis water.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for recycling sludge pyrolysis water, comprising the following steps:

[0009] S1, removing insoluble impurities and oil from sludge pyrolysis water to obtain a solid phase and a water phase;

[0010] S2, after the aqueous phase is subjected to electrocatalytic oxidation treatment, aeration is performed to balance the water body, and the pH is adjusted to 5.5-6.5, and sedimentation is performed to obtain a precipitate; in the electrocatalytic oxidation treatment, a BDD (boron-doped diamond) electrode is used as an anode, a metal electrode is used as a cathode, and an operating voltage is 4-10V;

[0011] S3, evaporating the effluent treated in step S2 at a low temperature, wherein the evaporation temperature is 35-40° C. to obtain a concentrated solution, and the obtained concentrated solution is used as a biocarbon source.

[0012] The treatment method of the present invention can realize resource treatment of sludge pyrolysis water, effectively remove toxic and harmful substances, reduce COD, reduce ammonia nitrogen content, and obtain a high B / C biological carbon source.

[0013] Among them, in step S1 of the present invention, insoluble impurities and soluble tar are removed, impurities entering the electrocatalytic oxidation system are reduced, and the electrocatalytic oxidation efficiency is improved.

[0014] In step S2 of the present invention, electrochemical oxidation technology is used to effectively remove toxic and harmful components in pyrolysis water. In the electrocatalytic oxidation, electrodes are used to generate hydroxyl radicals, and refractory organic matter is decomposed and oxidized to achieve chain breaking, converted into small molecule organic matter, and refractory COD is converted into easily degradable BOD; preferably, a BDD electrode is used as an anode and a metal electrode is used as a cathode. The BDD electrode has an extremely high oxygen evolution potential and the widest electrochemical window. The operating voltage is controlled to be 4-10V, which can significantly improve the B / C of pyrolysis water; at the same time, aeration is used to increase the oxygen content of the water body, balance the water body, and facilitate the subsequent reduction of COD; the pH is controlled to be 5.5-6.5. Under slightly acidic conditions, chlorine gas is generated after the electrolysis of chloride ions in the water, and the oxidation capacity is enhanced, which can effectively coordinate the reduction of COD and ammonia nitrogen.

[0015] The cathode is a metal electrode. Preferably, the metal electrode includes but is not limited to a titanium electrode, a zinc electrode, and a zinc-manganese electrode.

[0016] Preferably, the alkaline agent used to adjust the pH is one or more of sodium hydroxide, lime, and sodium carbonate; the acidic agent is one or more of hydrochloric acid, sulfuric acid, and citric acid.

[0017] In step S3 of the present invention, the sewage is evaporated at low temperature to effectively achieve the enrichment of organic matter and the utilization of ultra-low-grade heat sources for the preparation of biological carbon sources, and ammonia nitrogen and bicarbonate in the wastewater can be removed at the same time. The evaporation temperature is 35-40°C, which can ensure the evaporation treatment efficiency and avoid a large amount of organic matter escaping at high temperature as much as possible, causing environmental pollution. At the same time, the concentrated solution is made into a biological carbon source for resource utilization, and the obtained biological carbon source can achieve COD ≥ 300,000 mg / L and B / C ≥ 0.6.

[0018] In some embodiments, in step S2, the electrocatalytic oxidation treatment is performed at a working current of 10-100 mA cm -2 , the temperature is 10 ~ 50 ℃.

[0019] In some embodiments, the concentrated solution obtained in step S3 can be used as a liquid fertilizer as a biocarbon source, and the concentrated solution can also be formed into a solid fertilizer under low temperature evaporation.

[0020] In some embodiments, in step S2, the aeration rate of the aerated equalization water body is 10-30m 3 / min; the retention time is not less than 6h. Balanced water body can balance water quality and improve the stability of water treatment.

[0021] In some embodiments, in step S1, a flocculant is used to remove insoluble impurities and remove oil.

[0022] Specifically, in step S1, the process is divided into four functional zones, including: zone one for pH adjustment, zone two for flocculation, zone three for coagulant aid, and zone four for buffering.

[0023] Preferably, the acid used to adjust the pH is one of hydrochloric acid, sulfuric acid, phosphoric acid and citric acid, so that the pH is ≤ 6.5.

[0024] Preferably, a flocculant or a combination of a flocculant and a coagulant aid is used for removing turbidity and soluble tar, and the flocculant includes but is not limited to: one or a combination of two or more of polyaluminium chloride, polyaluminium sulfate, polyferric sulfate or ferric chloride. The coagulant aid is selected from polyacrylamide and / or gelatin.

[0025] In some embodiments, in step S3, the concentration ratio of the low-temperature evaporation is greater than 75%.

[0026] In some embodiments, the effluent from the low-temperature evaporation treatment in step S3 is subjected to biochemical treatment and / or membrane filtration treatment, and the obtained water is discharged and / or reused. The biochemical treatment and / or membrane filtration treatment of the effluent from the low-temperature evaporation can further reduce the COD and ammonia nitrogen content, so that the effluent is purified to meet the discharge requirements.

[0027] Preferably, the biochemical treatment is carried out by an aerobic-anoxic process.

[0028] Preferably, the membrane filtration treatment is RO membrane (reverse osmosis membrane) treatment.

[0029] Preferably, the system operating pressure in the above RO membrane treatment is 0.8-1.5Mpa.

[0030] In some embodiments, a sludge treatment step S5 is further included, and the sludge treatment step S5 is: mixing the solid phase obtained in the step S1 and the precipitate obtained in the step S2 and performing filter pressing treatment.

[0031] In some embodiments, the COD of the sludge pyrolysis water is 50,000-60,000 mg / L, the ammonia nitrogen content is 1,000-3,000 ppm; and the B / C is 0.7-0.9.

[0032] Another object of the present invention is to provide a resource processing system for sludge pyrolysis water, comprising:

[0033] (1) a pretreatment unit for removing insoluble impurities and oil from sludge pyrolysis water;

[0034] In some of the embodiments, the functional areas of the pretreatment unit are divided into four zones, namely pH adjustment zone 1, flocculation zone 2, coagulant zone 3 and buffer zone 4; a mechanical stirring device is also provided in the pretreatment unit, and the material of the stirring device is any one of carbon steel, 316L, and 2205.

[0035] (2) an electrocatalytic oxidation unit connected to the water outlet of the pretreatment unit and used to perform electrocatalytic oxidation treatment on the water phase treated by the pretreatment unit;

[0036] In some of the embodiments, a filter is provided at the front end of the electrocatalytic oxidation unit, and the filter pore size is 450-550 mesh, which is mainly used to intercept suspended particulate matter.

[0037] The cathode of the electrocatalytic oxidation unit uses a titanium electrode and the anode uses a BDD electrode. The anode current carrying density is 200-800A / m 2 .

[0038] The equipment is made of any highly corrosion-resistant material including PP, PVC, PE, polytetrafluoroethylene, and carbon steel.

[0039] The electrocatalytic oxidation unit can be configured in multiple stages in series, in a continuous configuration, or in a batch configuration.

[0040] A plate heat exchanger is arranged inside the electrocatalytic oxidation unit, and the cooling water source is a low-temperature evaporation system.

[0041] (3) a homogenization regulating unit connected to the electrocatalytic oxidation unit, wherein an aeration device is provided inside the homogenization regulating unit for balancing the water body and adjusting the pH;

[0042] (4) a low-temperature evaporation unit connected to the water outlet of the homogenization adjustment unit and used for evaporating and concentrating the sewage;

[0043] In some embodiments, the heat source of the low-temperature evaporation unit is 80-90° C. hot water.

[0044] The low-temperature evaporation unit is made of any one of 316L, 2205 and titanium.

[0045] (5) a biochemical / membrane treatment unit connected to the water outlet of the low-temperature evaporation unit and used for biodegradation and / or membrane filtration treatment of the sewage;

[0046] (6) A sludge treatment unit connected to the sludge discharge end of the pretreatment unit and / or the homogenization adjustment unit, and used for filter pressing the sludge.

[0047] In some embodiments, the sludge treatment unit is a sludge thickening tank, a plate and frame filter press system, and a polymer dosing device connected in sequence, and the mud cake filtered by the plate and frame filter press system is transferred to a carbonization device for disposal.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention provides a resource treatment method for sludge pyrolysis water, which can remove toxic and harmful substances through electrocatalytic oxidation treatment, reduce the COD of sewage, and improve the B / C ratio; at the same time, low-temperature evaporation and concentration are used to reduce the ammonia nitrogen content, and organic matter is concentrated to prepare a biological carbon source, which can achieve COD≥300,000 mg / L and B / C≥0.6; COD and ammonia nitrogen content are further reduced through biochemical treatment and / or membrane filtration treatment, so that the effluent is purified to meet the discharge requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The present invention is a process flow chart of a method for resource recovery treatment of sludge pyrolysis water. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0052] Example 1

[0053] A method for recycling sludge pyrolysis water, the process flow is as follows Figure 1 As shown, the following steps are included:

[0054] S1, removing insoluble impurities and oil from sludge pyrolysis water to obtain a solid phase and a water phase;

[0055] Specifically: the pH of the sludge pyrolysis water is adjusted to 7.5, and then flocculants and coagulants are used to remove turbidity and soluble tar, and the solid phase and the water phase are obtained by sedimentation; wherein, the acid used to adjust the pH is hydrochloric acid, the flocculant is polyaluminum chloride, and the coagulant aid is polyacrylamide.

[0056] S2, after subjecting the aqueous phase to electrocatalytic oxidation treatment, aeration is performed to balance the water body, the pH is adjusted to 6.0, and sedimentation is performed to obtain a precipitate;

[0057] Specifically: In the electrocatalytic oxidation treatment, the aqueous phase is filtered through a filter with a pore size of 500 mesh and then enters the electrocatalytic oxidation system for treatment, wherein the cathode uses a titanium electrode and the anode uses a BDD electrode, and the anode current carrying density is 500A / m 2 ; Water temperature is controlled at 30℃, working voltage is 8V, working current is 55mAcm -2 .

[0058] The aeration volume in the aerated balanced water body is 20m 3 / min; the residence time is 6h.

[0059] The alkaline reagent used to adjust the pH is sodium hydroxide, and the reagent is hydrochloric acid.

[0060] S3, evaporating the effluent treated in step S2 at a low temperature, controlling the evaporation temperature to 37° C., evaporating to a concentration ratio of 85% to obtain a concentrated solution, and using the concentrated solution as a biocarbon source.

[0061] S4, subjecting the effluent from the low-temperature evaporation treatment in step S3 to biochemical treatment and membrane filtration treatment, and the obtained water is discharged and / or reused.

[0062] The biochemical treatment adopts conventional activated sludge aerobic-anoxic process. The membrane filtration treatment is a primary RO membrane system, and the operating pressure of the membrane system is 1.2Mpa.

[0063] S5, mixing the solid phase obtained in step S1 and the precipitate obtained in step S2 and subjecting them to filter pressure treatment.

[0064] Example 2

[0065] A method for recycling sludge pyrolysis water is basically the same as Example 1, except that the aeration rate is 30m 3 / min, and the residence time is 7h.

[0066] Example 3

[0067] A method for resource recovery of sludge pyrolysis water is basically the same as Example 1, except that: in the electrocatalytic oxidation treatment, the operating voltage is 6V.

[0068] Example 4

[0069] A resource processing system for sludge pyrolysis water, comprising:

[0070] (1) a pretreatment unit for removing insoluble impurities and oil from sludge pyrolysis water;

[0071] The functional areas of the pretreatment unit described in this embodiment are divided into four areas, namely pH adjustment area 1, flocculation area 2, coagulant aid area 3 and buffer area 4; a mechanical stirring device is also provided in the pretreatment unit, and the material of the stirring device is 316L.

[0072] (2) an electrocatalytic oxidation unit connected to the water outlet of the pretreatment unit and used to perform electrocatalytic oxidation treatment on the water phase treated by the pretreatment unit;

[0073] The electrocatalytic oxidation unit described in this embodiment is a multi-stage series structure. The equipment is made of polytetrafluoroethylene material. A plate heat exchanger is arranged inside the electrocatalytic oxidation unit, and the cooling water source is a low-temperature evaporation system. A filter is arranged at the front end of the electrocatalytic oxidation unit, and the filter aperture is 500 mesh, which is mainly used to intercept suspended particulate matter. The cathode of the electrocatalytic oxidation unit adopts a titanium electrode, and the anode adopts a BDD electrode, and the anode current carrying density is 500A / m 2 .

[0074] (3) a homogenization regulating unit connected to the electrocatalytic oxidation unit, wherein an aeration device is provided inside the homogenization regulating unit for balancing the water body and adjusting the pH;

[0075] (4) a low-temperature evaporation unit connected to the water outlet of the homogenization adjustment unit and used for evaporating and concentrating the sewage;

[0076] The heat source of the low temperature evaporation unit in this embodiment is 85° C. hot water. The material of the low temperature evaporation unit is 316L.

[0077] (5) a biochemical / membrane treatment unit connected to the water outlet of the low-temperature evaporation unit and used for biodegradation and / or membrane filtration treatment of the sewage;

[0078] (6) a biocarbon source preparation unit, connected to the concentrated liquid end of the low-temperature evaporation unit, for concentrating the concentrated liquid to prepare a biocarbon source;

[0079] (7) A sludge treatment unit connected to the sludge discharge end of the pretreatment unit and / or the homogenization adjustment unit, and used for filter pressing the sludge.

[0080] The resource treatment system for sludge pyrolysis water of the present embodiment adopts the resource treatment method for sludge pyrolysis water described in Example 1 for water treatment when in use.

[0081] Comparative Example 1

[0082] A method for recycling sludge pyrolysis water is basically the same as Example 1, except that:

[0083] In step S2: In this comparative example, the water phase is not subjected to electrocatalytic oxidation treatment, and the water phase obtained in step S1 is directly aerated to balance the water body, and the aeration volume in the aerated balance water body is 20m 3 / min; the residence time is 6h, the pH is adjusted to 6.0, and the precipitate is obtained by sedimentation.

[0084] Comparative Example 2

[0085] A method for resource treatment of sludge pyrolysis water is basically the same as Example 1, except that: the anode is a platinum electrode.

[0086] Comparative Example 3

[0087] A method for resource recovery of sludge pyrolysis water is basically the same as Example 1, except that in the electrocatalytic oxidation treatment, the operating voltage is 12V.

[0088] Performance Testing

[0089] The present invention adopts the resource treatment method of sludge pyrolysis water of Examples 1-2 and Comparative Examples 1-3 to treat sludge pyrolysis water. The indicators of the sludge pyrolysis water sample are: COD 56700 mg / L, ammonia nitrogen 2000 ppm, B / C 0.18; and the performance test is carried out by the following test method.

[0090] 1. Test methods

[0091] The test method for chemical oxygen demand (COD) is determined according to the potassium dichromate test method of standard GB11914-89.

[0092] The test method for ammonia nitrogen is the Nessler's reagent colorimetric method.

[0093] The test method for five-day biochemical oxygen demand (BOD5) is based on the method of GB / T 7488-1987.

[0094] The B / C is the ratio between the five-day biochemical oxygen demand (BOD5) and the chemical oxygen demand (COD).

[0095] 2. Test results

[0096] The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] As can be seen from the above table, the COD of the concentrated solution with a concentration ratio of 85% obtained by the present invention is above 312000 mg / L, the ammonia nitrogen is below 50 ppm, and the B / C is above 0.64. The obtained biocarbon source has the effects of high B / C ratio and low ammonia nitrogen content.

[0101] Compared with Example 1, in Comparative Example 1, the aqueous phase is not subjected to electrocatalytic oxidation treatment, the B / C ratio of the biocarbon source is relatively low, the ammonia nitrogen content is too high, and it is not suitable as a biocarbon source. In Comparative Example 2, the anode is a platinum electrode, and its electrocatalytic oxidation treatment effect is not good, and toxic and harmful substances cannot be effectively removed. The ammonia nitrogen content is high, and the B / C ratio of the product decreases. In Comparative Example 3, the voltage is too high, the reaction is uncontrollable, a large amount of foam is generated, the reaction is inhibited, the B / C ratio of the product decreases, and the concentrated solution is not suitable as a biocarbon source.

[0102] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for recycling sludge pyrolysis water, characterized in that: The following steps are involved: S1, removing insoluble impurities and oil from sludge pyrolysis water to obtain a solid phase and a water phase; S2, after the aqueous phase is subjected to electrocatalytic oxidation treatment, aeration is performed to balance the water body, and the pH is adjusted to 5.5-6.5, and precipitation is performed to obtain a precipitate; in the electrocatalytic oxidation treatment, the BDD electrode is used as the anode, the metal electrode is used as the cathode, and the operating voltage is 4-10V; S3, evaporating the effluent treated in step S2 at a low temperature, wherein the evaporation temperature is 35-40° C., and the obtained concentrated solution is used as a biocarbon source.

2. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: In step S2, the temperature of the electrocatalytic oxidation treatment is 10-50°C.

3. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: In step S2, the aeration volume of the aerated water body is 10-30m 3 / min; residence time is not less than 6h.

4. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: In step S3, the effluent from the low-temperature evaporation treatment is subjected to biochemical treatment and / or membrane filtration treatment, and the obtained water is discharged and / or reused.

5. The method for recycling sludge pyrolysis water according to claim 4, characterized in that: The biochemical treatment adopts an aerobic-anoxic process.

6. The method for recycling sludge pyrolysis water according to claim 4, characterized in that: The membrane filtration treatment is RO membrane treatment.

7. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: The method further comprises a sludge treatment step S5, wherein the sludge treatment step S5 comprises: mixing the solid phase obtained in the step S1 and the precipitate obtained in the step S2 and subjecting the mixture to filter pressure treatment.

8. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: In step S1, a flocculant is used to remove insoluble impurities and remove oil.

9. The method for recycling sludge pyrolysis water according to claim 1, characterized in that: The COD of the sludge pyrolysis water is 50000-60000 mg / L, the ammonia nitrogen content is 1000-3000 ppm; and the B / C is 0.7-0.

9.

10. A resource processing system for sludge pyrolysis water, characterized in that: include: A pretreatment unit is used to remove insoluble impurities and oil from sludge pyrolysis water; An electrocatalytic oxidation unit, connected to the water outlet of the pretreatment unit, for electrocatalytically oxidizing the water phase obtained by the pretreatment unit; A homogenization regulating unit is connected to the electrocatalytic oxidation unit, and an aeration device is provided inside the homogenization regulating unit for balancing the water body and adjusting the pH; A low-temperature evaporation unit, connected to the water outlet of the homogenization regulating unit, for evaporating and concentrating the sewage; A biochemical / membrane treatment unit, connected to the water outlet of the low-temperature evaporation unit, for biodegrading and / or membrane filtration treatment of sewage; The sludge treatment unit is connected to the sludge discharge end of the pretreatment unit and / or the homogenization adjustment unit, and is used for performing filter pressing treatment on the sludge.

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