Method for deeply treating silicon-containing wastewater by activated sludge process

Abstract

The invention relates to a method for deeply treating silicon-containing wastewater by an activated sludge process, which comprises a treatment system and is characterized in that firstly, activated sludge is generated by an activated sludge process unit, the activated sludge enters a secondary sedimentation tank, and meanwhile, the silicon-containing wastewater enters a silicon removal mixing tank through a pipeline to form a silicon-containing mixed solution; the silicon-containing mixed liquid automatically flows into the primary sedimentation tank, the upper layer is wastewater, and the lower layer is sludge; wastewater on the upper layer enters the activated sludge process unit, and sludge on the lower layer enters the sludge drying and dewatering unit through the second sludge pump; new activated sludge automatically flows into the secondary sedimentation tank to be settled, and settled clear liquid is discharged through a water outlet; one part of the remaining sludge flows back to the activated sludge process unit through the reflux pump, and the other part of the remaining sludge enters the silicon removal mixing tank for use through the first sludge pump. By means of the method, the problem that the medicament cost is high is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, in particular to a method for deep treatment of silicon-containing wastewater using an activated sludge method. Background Art

[0002] In coal chemical industry or petrochemical industry, since the raw materials contain silicon, the downstream wastewater is also silicon-containing wastewater. Silicon easily accumulates in the wastewater system to form silicon scale, causing blockage of system equipment and pipelines, and is difficult to clean. This type of silicon-containing wastewater needs to be deeply treated to reduce damage to the system and equipment pipelines. The existing methods for treating silicon-containing wastewater mainly use biochemical treatment. The dehydration of residual activated sludge is a major problem that is difficult to treat in activated sludge. The residual activated sludge contains a large number of microorganisms and extracellular polymers. These substances usually contain a large amount of bound water. In the sludge dehydration process, in order to improve the dehydration efficiency, lime needs to be added to destroy the activated sludge structure and make the bound water easy to precipitate. Aluminum salts or iron salts are then added to settle the sludge flocs, which increases a lot of chemical costs in the wastewater treatment process. Summary of the Invention

[0003] In view of this, the present application provides a method for deep treatment of silicon-containing wastewater using an activated sludge method, which can achieve deep treatment of silicon-containing wastewater, enhance the dewatering performance of excess activated sludge, and reduce the cost of reagents.

[0004] 1. The method of claim 1, wherein the sludge treatment plant is a sludge treatment plant comprising a sludge treatment plant, a sludge treatment plant, and a sludge treatment plant. The sludge treatment plant comprises a sludge treatment plant, a sludge treatment plant, a sludge treatment plant, and a sludge treatment plant. The sludge treatment plant comprises a sludge treatment plant, a sludge treatment plant, and a sludge treatment plant. The sludge treatment plant comprises a sludge treatment plant, a sludge treatment plant, and a sludge treatment plant. The sludge treatment plant comprises a sludge treatment plant, a sludge treatment plant, and a sludge treatment plant. The activated sludge is fed into the secondary sedimentation tank; the silicon-containing wastewater enters the silicon removal mixing tank; the activated sludge is fed from the secondary sedimentation tank into the silicon removal mixing tank via the first sludge pump; the activated sludge and silicon-containing wastewater in the silicon removal mixing tank are stirred and mixed by an agitator to form a silicon-containing mixed liquid; the silicon-containing mixed liquid flows by gravity into the primary sedimentation tank for static sedimentation, and after sedimentation, the upper layer is wastewater and the lower layer is sludge; the wastewater in the upper layer enters the activated sludge process unit via the lifting pump, and the wastewater in the upper layer is assimilated by microorganisms in the activated sludge process unit to obtain new activated sludge; the new activated sludge flows by gravity into the secondary sedimentation tank for sedimentation, and the precipitated clarified liquid is discharged through the outlet; the sludge in the lower layer enters the sludge drying and dehydration unit via the second sludge pump, is dehydrated, and then discharged to the outside; after the clarified liquid is discharged, part of the remaining sludge in the secondary sedimentation tank is returned to the activated sludge process unit via the reflux pump, and the other part enters the silicon removal mixing tank for use via the first sludge pump.

[0005] In a possible implementation, the suspended solids concentration of the silicon-containing mixed solution is 2000 to 20000 mg / L.

[0006] In a possible implementation, the ratio of the silicon concentration in the silicon-containing mixed liquid to the sludge concentration in the mixed liquid is 1:20-100.

[0007] In a possible implementation, an external agitator stirs and mixes the activated sludge and silicon-containing wastewater in the desiliconization mixing tank to form a mixed liquid, and the stirring time is 0.5 to 2 hours.

[0008] In a possible implementation, the process of the activated sludge process unit is one of the AO process, the AAO process, and the SBR process.

[0009] In one possible implementation, the upper layer of wastewater enters the activated sludge process unit through the lifting pump, and the upper layer of wastewater is assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge. The upper layer of wastewater includes COD, nitrogen, phosphorus and silicon, and the COD, nitrogen, phosphorus and silicon are assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge.

[0010] In one possible implementation, the silicon-containing wastewater is 30-300 mg / L and has a pH of 4-11.

[0011] In a possible implementation, the activated sludge process unit is an aerobic aeration tank or an oxidation ditch process.

[0012] In one possible implementation, the water outlet of the desiliconization mixing tank is connected to the water inlet of the primary sedimentation tank by a pipeline, the bottom of the primary sedimentation tank is connected to the top of the sludge drying and dehydration unit by a pipeline, the water outlet of the primary sedimentation tank is connected to the water inlet of the activated sludge process unit by a pipeline, the water outlet of the activated sludge process unit is connected to the water inlet of the secondary sedimentation tank by a pipeline, and the bottom mud outlet of the secondary sedimentation tank is connected to the mud inlet of the desiliconization mixing tank by a pipeline.

[0013] In one possible implementation, the method is also beneficial for dewatering activated sludge.

[0014] The present invention has the following beneficial effects: Through the above-mentioned method, excess activated sludge is used as an adsorbent for silicon-containing wastewater, and the activated sludge system is used to grade and reduce the silicon content in the wastewater, preventing silicon from accumulating within the biochemical system due to sludge circulation. Furthermore, silicates in the wastewater are used as a conditioning agent for activated sludge dewatering, enhancing sludge dewatering performance. By combining the properties of the wastes, the addition of silicon removal agents and activated sludge dewatering conditioning agents is eliminated, reducing disposal costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A wastewater treatment process diagram according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0017] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0020] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," "fixed," "joined," and "hinge" should be understood in a broad sense. For example, these terms may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0021] This method is applied to coal chemical industry or petrochemical industry. Since the raw materials contain silicon, the downstream wastewater is also silicon-containing wastewater. Silicon easily accumulates in the wastewater system to form silicon scale, causing blockage of system equipment and pipelines, and is difficult to clean. This type of silicon-containing wastewater needs to be deeply treated to reduce damage to the system and equipment pipelines. This application is a method for deep treatment of silicon-containing wastewater using an activated sludge method, which can achieve deep treatment of silicon-containing wastewater and enhance the dewatering performance of the remaining activated sludge. It should be noted here that this method is suitable for silicon-containing wastewater with a silicon concentration of 30 to 300 mg / L and a pH of 4 to 11.

[0022] In one specific embodiment, the activated sludge method for deep treatment of silicon-containing wastewater uses the following treatment system to treat silicon-containing wastewater. Figure 1 As shown, the wastewater treatment system includes a desiliconization mixing tank 100, a primary sedimentation tank 200, a sludge drying and dehydration unit 300, an activated sludge process unit 400, and a secondary sedimentation tank 500. The desiliconization mixing tank of the wastewater treatment system is provided with a wastewater inlet for the inflow of silicon-containing wastewater to be treated, and the other end of the treatment system is provided with a water outlet for discharging the treated water.

[0023] In this embodiment of the present application, a pipeline connects the desiliconization mixing tank 100 to the primary sedimentation tank 200, a pipeline connects the primary sedimentation tank 200 to the activated sludge process unit 400, and a pipeline connects the activated sludge process unit 400 to the secondary sedimentation tank 500. The wastewater to be treated sequentially passes through the desiliconization mixing tank 100, the primary sedimentation tank 200, the activated sludge process unit 400, and the secondary sedimentation tank 500. Furthermore, a pipeline connects the secondary sedimentation tank 500 to the desiliconization mixing tank 100, and a first sludge pump is provided between the secondary sedimentation tank 500 and the desiliconization mixing tank 100 to discharge some of the newly activated sludge into the desiliconization mixing tank 100.

[0024] The treatment system is further provided with a sludge drying and dehydration unit 300, and a pipeline is connected between the primary sedimentation tank 200 and the sludge drying and dehydration unit 300. The sludge drying and dehydration unit 300 is used to dry and dehydrate the sludge after the first treatment.

[0025] A return pump is provided between the secondary sedimentation tank 600 and the activated sludge process unit 400 to output another portion of new sludge to the activated sludge process unit 400. A second sludge pump is provided between the primary sedimentation tank 200 and the sludge drying and dewatering unit 300 to output the sludge in the primary sedimentation tank 200 to the sludge drying and dewatering unit 300. A lift pump is provided between the primary sedimentation tank 200 and the activated sludge process unit 400 to output the wastewater in the primary sedimentation tank 200 to the activated sludge process unit 400.

[0026] The left end of the desiliconization mixing tank 100 is equipped with an inlet for connecting to a pipeline. Silicon-containing wastewater enters the desiliconization mixing tank 100 through the pipeline. A primary sedimentation tank 200 is connected to the right side of the desiliconization mixing tank 100. The primary sedimentation tank 200 primarily serves to precipitate the mixed liquor in the primary sedimentation tank 200, separating the wastewater and sludge. The upper layer is wastewater, and the lower layer is sludge. The outlet of the desiliconization mixing tank 100 is connected to the inlet of the primary sedimentation tank 200 via a pipeline. An activated sludge process unit 400 is then connected to the right side of the primary sedimentation tank 200. The activated sludge unit is primarily used to produce activated sludge. The outlet of the primary sedimentation tank 200 is connected to the inlet of the activated sludge process unit 400 via a pipeline. A sludge drying and dewatering unit 300 is connected below the primary sedimentation tank 200 to process the sludge in the lower layer of the primary sedimentation tank 200 before discharge. A secondary sedimentation tank 500 is connected to the right side of the activated sludge process unit 400. The outlet of the activated sludge process unit 400 is connected to the inlet of the secondary sedimentation tank 500 by a pipeline, and is used to precipitate the activated sludge produced by the activated sludge process unit 400 and precipitate the clarified liquid. An outlet is opened on the right side of the secondary sedimentation tank, and the clarified liquid is discharged through the outlet. The top of the secondary sedimentation tank 500 is connected to the top of the desiliconization mixing tank 100 by a pipeline, and the bottom of the secondary sedimentation tank 500 is connected to the mud inlet of the desiliconization mixing tank 100 by a pipeline. A portion of the remaining activated sludge enters the desiliconization mixing tank 100 to treat the silicon-containing wastewater. The bottom of the secondary sedimentation tank is connected to the bottom of the activated sludge process unit 400, and the remaining activated sludge is returned to the activated sludge process unit 400 for further wastewater treatment.

[0027] In order to make the overall structure more perfect and enable the entire method to be implemented, multiple pumps are also set up, as follows: a first sludge pump is set between the secondary sedimentation tank and the silicon removal mixing tank 100, a return pump is set between the secondary sedimentation tank and the activated sludge process unit 400, a second sludge pump is set between the primary sedimentation tank 200 and the sludge drying and dehydration unit 300, and a lifting pump is set between the primary sedimentation tank 200 and the activated sludge process unit 400. This arrangement facilitates the sludge to enter the next step.

[0028] The method comprises the following steps:

[0029] The activated sludge process unit 400 produces activated sludge, which enters the secondary sedimentation tank 500;

[0030] The silicon-containing wastewater enters the silicon removal mixing tank 100;

[0031] The activated sludge is fed from the secondary sedimentation tank 500 to the desiliconization mixing tank 100 via the first sludge pump;

[0032] The activated sludge and silicon-containing wastewater in the desiliconization mixing tank 100 are stirred and mixed by an agitator to form a silicon-containing mixed liquid;

[0033] The silicon-containing mixed liquid flows by gravity into the primary sedimentation tank 200 for static sedimentation. After sedimentation, the upper layer is wastewater and the lower layer is sludge.

[0034] The wastewater in the upper layer enters the activated sludge process unit 400 through the lifting pump, and the wastewater in the upper layer is assimilated by the microorganisms in the activated sludge process unit 400 to obtain new activated sludge;

[0035] The new activated sludge flows by gravity to the secondary sedimentation tank 500 for sedimentation, and the precipitated clarified liquid is discharged through the outlet;

[0036] The sludge in the lower layer enters the sludge drying and dehydration unit 300 through the second sludge pump, and is discharged to the outside after being dehydrated;

[0037] After the clarified liquid is discharged, part of the sludge remaining in the secondary sedimentation tank 500 is returned to the activated sludge process unit 400 through the reflux pump, and the other part enters the desiliconization mixing tank 100 for use through the first sludge pump.

[0038] Through the above steps, the excess activated sludge is used as an adsorbent for silicon-containing wastewater, and the activated sludge system is used to grade and reduce the silicon content in the wastewater, preventing silicon from accumulating within the biochemical system due to sludge circulation. Furthermore, the silicate in the wastewater is used as a conditioning agent for activated sludge dewatering, enhancing sludge dewatering performance. By combining the properties of the wastes, the addition of silicon removal agents and activated sludge dewatering conditioning agents is eliminated, reducing disposal costs.

[0039] It should be noted that the suspended solids concentration of the mixed liquor is 2000-20000 mg / L, and the ratio of the silicon concentration in the mixed liquor to the sludge concentration in the mixed liquor is 1:20-100.

[0040] The activated sludge process unit 400 may be an AO process, an AAO process, or an SBR process. The activated sludge process unit 400 may be an aerobic aeration tank or an oxidation ditch process. These processes can produce activated sludge.

[0041] This method can also be used for activated sludge dewatering. Specifically, the steps are as follows: the activated sludge process unit 400 produces activated sludge, which enters the secondary sedimentation tank 500; silicon-containing wastewater enters the silicon removal mixing tank 100; the activated sludge is pumped from the secondary sedimentation tank 500 to the silicon removal mixing tank 100 via the first sludge pump; the activated sludge and silicon-containing wastewater in the silicon removal mixing tank 100 are stirred and mixed by an agitator to form a silicon-containing mixed liquid; the silicon-containing mixed liquid flows by gravity into the primary sedimentation tank 200 for static sedimentation. After sedimentation, the upper layer is wastewater and the lower layer is sludge; the sludge in the lower layer enters the sludge drying and dewatering unit 300 via the second sludge pump, where it is dehydrated and discharged to the outside.

[0042] The principles of this application are as follows:

[0043] This method uses excess activated sludge as an adsorbent for silicon-containing wastewater and employs a graded activated sludge system to reduce silicon content in the wastewater, preventing silicon from accumulating within the biochemical system due to sludge circulation. Furthermore, silicates in the wastewater are used as conditioning agents for activated sludge dewatering, enhancing sludge dewatering performance. This complementary treatment approach eliminates the need for silicon removal agents and activated sludge dewatering conditioning agents, reducing disposal costs and demonstrating excellent application value.

[0044] Silicon-containing wastewater from the coal chemical and petrochemical industries often exists in the form of silicates, which are alkaline. Activated sludge is primarily composed of microorganisms, which aggregate to form flocs, exhibiting excellent adsorption and settling properties. When silicon-containing wastewater is mixed with high-concentration activated sludge, the alkalinity of the water decreases, allowing silicates to readily combine with calcium and magnesium ions to form calcium and magnesium silicate colloids. These colloids, upon encountering the flocs in the activated sludge, further combine to form flocs, which are then incorporated into the activated sludge, effectively removing silicates from the wastewater.

[0045] Silicates can enhance the settling properties of activated sludge and improve sludge dewatering performance. Silicates chemically break down extracellular polymeric substances (EPS) in sludge, which typically contain a large amount of bound water. By disrupting the EPS structure, silicates help release bound water in the sludge, thereby improving dewatering efficiency. Furthermore, when silicates are used in combination with other dewatering agents (such as iron and aluminum salts), they can enhance the effectiveness of these agents. Silicates can form complexes with these metal ions, further promoting the coagulation and settling of sludge flocs and enhancing dewatering effectiveness. Furthermore, silicates can, to a certain extent, adjust the pH of the sludge, making it more suitable for the dewatering process. A suitable pH helps enhance the effectiveness of dewatering agents and further improves the dewatering performance of sludge. By improving the dewatering performance of sludge, silicates help reduce sludge volume and lower the costs of sludge treatment and disposal.

[0046] The following is a more detailed description using examples and comparative examples:

[0047] Example 1

[0048] This method is applied in the wastewater treatment system of a coal chemical enterprise to treat silicon-containing wastewater. The activated sludge process unit used by the enterprise selects silicon removal pretreatment-AO biochemical method to treat silicon-containing wastewater, with a treatment capacity of 10m 3 / h, the specific steps are as follows:

[0049] S1: First, activated sludge is produced through the AO process unit (activated sludge process unit), and the activated sludge enters the secondary sedimentation tank;

[0050] S2: The activated sludge is pumped from the secondary sedimentation tank to the desiliconization mixing tank through the first sludge pump, and the silicon-containing wastewater enters the desiliconization mixing tank through the pipeline;

[0051] S3: The activated sludge and silicon-containing wastewater in the desiliconization mixing tank are stirred and mixed by an external agitator to form a mixed liquid;

[0052] S4: Afterwards, the mixed liquid formed in the above steps flows into the primary sedimentation tank by gravity for static sedimentation. After sedimentation, the upper layer is wastewater and the lower layer is sludge;

[0053] S5: The wastewater from the upper layer enters the activated sludge process unit through the lifting pump. The wastewater from the upper layer is assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge. The sludge from the lower layer enters the sludge drying and dehydration unit through the second sludge pump, is dehydrated, and then discharged to the outside.

[0054] S6: The new activated sludge obtained in the above step flows by gravity to the secondary sedimentation tank for sedimentation, and the precipitated clarified liquid is discharged through the outlet;

[0055] S7: After the clarified liquid is discharged, part of the new activated sludge remaining in the secondary sedimentation tank is returned to the activated sludge process unit through the reflux pump, and the other part enters the silicon removal mixing tank through the first sludge pump for use.

[0056] Among them, 80% of the sludge in the secondary sedimentation tank is returned, and the sludge discharge is intermittent, with an average sludge discharge volume of 2m 3 / h, resulting in a residual activated sludge concentration of 15,000 mg / L. The sludge concentration in the desiliconization mixing tank was adjusted to 5,000 mg / L by adjusting the sludge discharge rate. The agitator in the desiliconization mixing tank was set at 60 r / min, and the mixing residence time was 60 min. The effluent then entered the AO treatment, where its residence time was 8 h. Water quality measurements were taken from the untreated wastewater, the effluent from the desiliconization mixing tank, and the effluent from the AO secondary sedimentation tank. The results are shown in Table 1.

[0057] Table 1. Water quality results

[0058] index pH COD Ammonia nitrogen Total nitrogen Total phosphorus <![CDATA[Silicon (calculated as SiO2)]]> unit mg / L mg / L mg / L mg / L mg / L Untreated wastewater 9.26 1861 168 203 3.2 152 Desiliconization mixing tank effluent 8.63 1827 159 199 3.0 46 AO secondary sedimentation tank effluent 8.28 123 0.66 49 0.08 6.2

[0059] Water quality testing results show that after pre-silicon removal, the effluent silicon content was 46 mg / L, with a removal rate of 69.7%. The final effluent silicon content dropped to 6.2 mg / L, with a removal rate of 95.9%. The residual activated sludge concentration after silicon removal was 18,600 mg / L, while the concentration of the unremoved precipitated activated sludge was 15,000 mg / L, a 24% increase in sludge concentration.

[0060] Example 2

[0061] This method is applied in the wastewater treatment system of a petrochemical enterprise to treat silicon-containing wastewater. The activated sludge process unit adopted by the enterprise is silicon removal pretreatment-aerobic activated sludge method for silicon-containing wastewater treatment, with a treatment capacity of 6m 3 / h, the specific steps are as follows:

[0062] S1: First, activated sludge is produced through the aeration tank (activated sludge process unit), and the activated sludge enters the secondary sedimentation tank;

[0063] S2: The activated sludge is pumped from the secondary sedimentation tank to the desiliconization mixing tank through the first sludge pump, and the silicon-containing wastewater enters the desiliconization mixing tank through the pipeline;

[0064] S3: The activated sludge and silicon-containing wastewater in the desiliconization mixing tank are stirred and mixed by an external agitator to form a mixed liquid;

[0065] S4: Afterwards, the mixed liquid formed in the above steps flows into the primary sedimentation tank by gravity for static sedimentation. After sedimentation, the upper layer is wastewater and the lower layer is sludge;

[0066] S5: The wastewater from the upper layer enters the activated sludge process unit through the lifting pump. The wastewater from the upper layer is assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge. The sludge from the lower layer enters the sludge drying and dehydration unit through the second sludge pump, is dehydrated, and then discharged to the outside.

[0067] S6: The new activated sludge obtained in the above step flows by gravity to the secondary sedimentation tank for sedimentation, and the precipitated clarified liquid is discharged through the outlet;

[0068] S7: After the clarified liquid is discharged, part of the new activated sludge remaining in the secondary sedimentation tank is returned to the activated sludge process unit through the reflux pump, and the other part enters the silicon removal mixing tank through the first sludge pump for use.

[0069] Among them, 70% of the sludge in the secondary sedimentation tank is returned, and the sludge discharge is intermittent, with an average sludge discharge volume of 1.5m 3 / h, resulting in a residual activated sludge concentration of 13,000 mg / L. The sludge concentration in the desiliconization mixing tank was adjusted to 7,000 mg / L based on the sludge discharge rate. The agitator in the desiliconization mixing tank was operated at a stirring speed of 60 r / min, and the mixing residence time was 90 minutes. The effluent was then treated in an aerobic activated sludge tank for 12 hours. Water quality measurements were taken from the untreated wastewater, the desiliconization mixing tank effluent, and the secondary sedimentation tank effluent. The results are shown in Table 2.

[0070] Table 2. Water quality results

[0071] index pH COD Ammonia nitrogen Total nitrogen Total phosphorus <![CDATA[Silicon (calculated as SiO2)]]> unit mg / L mg / L mg / L mg / L mg / L Untreated wastewater 9.86 857 28 29 0.02 204 Desiliconization mixing tank effluent 8.16 765 29 31 0.2 68 Secondary sedimentation tank effluent 8.12 88 1.16 9.7 Not detected 8.6

[0072] Water quality testing results show that after pre-silicon removal, the effluent silicon content was 68 mg / L, with a removal rate of 66.7%. The final effluent silicon content dropped to 8.6 mg / L, with a removal rate of 95.8%. The residual activated sludge concentration after silicon removal was 19,400 mg / L, while the concentration of the unremoved precipitated activated sludge was 13,000 mg / L, a 50.8% increase in sludge concentration.

[0073] Comparative Example 1:

[0074] A coal chemical enterprise uses chemical precipitation to remove silicon from its silicon-containing wastewater. Sodium metaaluminate is added to the wastewater to make the concentration 300mg / L, acid is added to adjust the pH to 8.5, and stirred for 30 minutes. PAC is then added to make the concentration 20mg / L, and PAM is added to make the concentration 2mg / L. After stirring evenly, the solution is allowed to settle for 30 minutes, and the upper layer is discharged. The wastewater treatment capacity is 10m 3 / h, the silicon content was 152 mg / L, and the water quality parameters before and after silicon removal are shown in Table 3.

[0075] Table 3. Water quality results

[0076] index pH COD Ammonia nitrogen Total nitrogen Total phosphorus <![CDATA[Silicon (calculated as SiO2)]]> unit mg / L mg / L mg / L mg / L mg / L Untreated wastewater 9.26 1861 168 203 3.2 152 Wastewater after silicon removal 8.50 1974 169 195 1.1 34

[0077] Calculated from the test results, the silicon removal rate was 77.6%.

[0078] Based on the above data, Comparative Example 1 and Example 1 are from the same coal chemical enterprise, with the same wastewater quality. Compared with activated sludge silicon removal, Comparative Example 1 has three shortcomings: 1. Poor silicon removal efficiency; 2. Increased costs due to the addition of chemicals; and 3. The generation of sediment, which causes secondary pollution. In this comparative example, if the effluent silicon content is less than 10 mg / L, the amount of silicon removal chemical required would increase by 5-8 times.

[0079] In summary, this method has high silicon removal efficiency and can achieve deep silicon removal. The total removal rate can reach more than 90%, the silicon content in the effluent is less than 10 mg / L, and most of the silicates directly enter the residual sludge, avoiding the impact on the subsequent activated sludge system. At the same time, it also saves the cost of silicon removal agents, improves the dewatering performance of the residual activated sludge, and saves dewatering agents.

[0080] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for deep treatment of silicon-containing wastewater by an activated sludge process, characterized in that: treatment using a wastewater treatment system; The treatment system includes a desiliconization mixing tank, a primary sedimentation tank, a sludge drying and dehydration unit, an activated sludge process unit and a secondary sedimentation tank; The desiliconization mixing tank is connected to the primary sedimentation tank via a pipeline, the primary sedimentation tank is connected to the activated sludge process unit via a pipeline, the activated sludge process unit is connected to the secondary sedimentation tank via a pipeline, the secondary sedimentation tank is connected to the desiliconization mixing tank via a pipeline, and the primary sedimentation tank is also connected to the sludge drying and dehydration unit via a pipeline; A first sludge pump is provided between the secondary sedimentation tank and the desiliconization mixing tank, a reflux pump is provided between the secondary sedimentation tank and the activated sludge process unit, a second sludge pump is provided between the primary sedimentation tank and the sludge drying and dehydration unit, and a lift pump is provided between the primary sedimentation tank and the activated sludge process unit; The method comprises the following steps: The activated sludge process unit produces activated sludge, and the activated sludge enters the secondary sedimentation tank; The silicon-containing wastewater enters the silicon removal mixing tank; The activated sludge is input from the secondary sedimentation tank into the desiliconization mixing tank through the first sludge pump; The activated sludge and silicon-containing wastewater in the desiliconizing mixing tank are stirred and mixed by an agitator to form a silicon-containing mixed liquid; The silicon-containing mixed liquid flows into the primary sedimentation tank by gravity and undergoes static sedimentation. After sedimentation, the upper layer is wastewater and the lower layer is sludge; The wastewater in the upper layer enters the activated sludge process unit through the lifting pump, and the wastewater in the upper layer is assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge; The new activated sludge flows by gravity into the secondary sedimentation tank for sedimentation, and the precipitated clarified liquid is discharged through the outlet; The sludge in the lower layer enters the sludge drying and dehydration unit through the second sludge pump, and is discharged to the outside after being dehydrated; After the clarified liquid is discharged, part of the remaining sludge in the secondary sedimentation tank is returned to the activated sludge process unit through the reflux pump, and the other part enters the desiliconization mixing tank through the first sludge pump for use.

2. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claim 1, characterized in that: The suspended solid concentration of the silicon-containing mixed liquid is 2000-20000 mg / L.

3. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claim 2, characterized in that: The ratio of the silicon concentration in the silicon-containing mixed liquid to the sludge concentration in the mixed liquid is 1:20-100.

4. The method for deep treatment of silicon-containing wastewater by the activated sludge method according to claims 1-3, characterized in that: The external agitator stirs and mixes the activated sludge and silicon-containing wastewater in the desiliconization mixing tank to form a mixed liquid, and the stirring time is 0.5 to 2 hours.

5. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claim 4, characterized in that: The process of the activated sludge process unit is one of the AO process, the AAO process and the SBR process.

6. The method for deep treatment of silicon-containing wastewater by the sludge method according to claim 5, characterized in that: The upper layer of wastewater enters the activated sludge process unit through the lifting pump, and the upper layer of wastewater is assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge. The upper layer of wastewater includes COD, nitrogen, phosphorus and silicon, and the COD, nitrogen, phosphorus and silicon are assimilated by the microorganisms in the activated sludge process unit to obtain new activated sludge.

7. The method for deep treatment of silicon-containing wastewater by the sludge method according to claim 6, characterized in that: The silicon content in wastewater is 30-300 mg / L, and the pH is 4-11.

8. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claim 5, characterized in that: The process of the activated sludge process unit is an aerobic aeration tank or an oxidation ditch process.

9. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claims 1-3, characterized in that: The water outlet of the desiliconization mixing tank is connected to the water inlet of the primary sedimentation tank by a pipeline, the bottom of the primary sedimentation tank is connected to the top of the sludge drying and dehydration unit by a pipeline, the water outlet of the primary sedimentation tank is connected to the water inlet of the activated sludge process unit by a pipeline, the water outlet of the activated sludge process unit is connected to the water inlet of the secondary sedimentation tank by a pipeline, and the bottom mud outlet of the secondary sedimentation tank is connected to the mud inlet of the desiliconization mixing tank by a pipeline.

10. The method for deep treatment of silicon-containing wastewater by an activated sludge process according to claim 9, characterized in that: This method is also beneficial for dewatering activated sludge.

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