Start-up method of AnDMBR dynamic membrane for sludge anaerobic digestion

Abstract

This invention discloses a startup method for an AnDMBR dynamic membrane for sludge anaerobic digestion. During the startup phase, by adjusting the solids retention time, hydraulic retention time, biogas circulation intensity, and membrane flux in the membrane zone, the sludge operating concentration is rapidly increased and the dynamic membrane layer is rapidly formed, so that the transmembrane pressure difference in the membrane zone reaches the expected value in a short time, thereby improving the production efficiency of the reactor.

Description

Technical Field

[0001] This invention belongs to the field of sludge anaerobic digestion technology, and relates to a method for starting up an AnDMBR dynamic membrane for sludge anaerobic digestion. Background Technology

[0002] Anaerobic dynamic membrane bioreactor (AnDMBR) is a water treatment technology that combines membrane separation technology with the activated sludge process. When applied to anaerobic sludge digestion, the sludge undergoes anaerobic digestion in the main reaction zone, then enters the membrane zone. After being concentrated and separated by the dynamic membrane module, it is returned to the main reaction zone for further anaerobic digestion. During anaerobic digestion, the dynamic membrane module uses a large-pore, inexpensive substrate as a support layer. As the sludge liquid passes through the substrate, a biomass layer, i.e., the dynamic membrane layer, gradually forms on its surface, thus performing a retention function similar to traditional filter membranes and achieving sludge-water separation. Currently, anaerobic sludge digestion AnDMBR systems typically operate in a constant flux mode. As biomass deposits on the membrane surface, the membrane pressure continuously increases, and the dynamic membrane layer becomes increasingly dense; however, this process usually requires a long cycle.

[0003] In conventional AnDMBR processes, the startup of dynamic membranes is generally achieved by designing solid residence time, hydraulic residence time, biogas circulation intensity, daily sludge discharge, membrane effluent flux, and biogas circulation rate, so that the reactor operates under the above conditions until the membrane pressure and effluent turbidity stabilize within a certain range. However, in the above processes, the reactor usually needs to consume a long time in the early stage to form an ideal dense dynamic membrane layer, resulting in a high time cost for reactor startup and hindering the reactor from quickly reaching its full potential.

[0004] In view of the above, in order to effectively shorten the start-up cycle of the AnDMBR system and generate an ideal dynamic membrane layer in a short time, it is necessary to develop a start-up method for the AnDMBR dynamic membrane so that the reactor can be put into operation efficiently. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a startup method for an AnDMBR dynamic membrane for sludge anaerobic digestion. During the startup phase, by adjusting the solids retention time, hydraulic retention time, biogas circulation intensity, and membrane flux in the membrane zone, the sludge operating concentration is rapidly increased and the dynamic membrane layer is quickly formed, enabling the transmembrane pressure difference in the membrane zone to reach the expected value in a short time, thereby improving the reactor's production efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for starting up a dynamic AnDMBR membrane for sludge anaerobic digestion, comprising the following steps:

[0008] S1, during the start-up phase of the AnDMBR, the hydraulic retention time in the membrane zone is controlled to be 10–15 days, the solids retention time to be 30–50 days, and the biogas circulation intensity in the membrane zone is controlled to be 0–10 m³ / s. 3 / (m 2 •h), promotes the rapid formation of dynamic films;

[0009] S2, during the stable operation phase of AnDMBR, after the dynamic membrane layer is formed, the circulation intensity of biogas is increased, and cross-flow of biogas on the membrane surface is used to control the transmembrane pressure difference to 5-10 kPa.

[0010] Preferably, in step S1, during the start-up phase of the AnDMBR, the membrane flux is 2–8 LMH.

[0011] Preferably, in step S1, the dynamic film layer is rapidly formed within one day.

[0012] Preferably, in step S2, during the stable operation phase of the AnDMBR, the sludge concentration in the main reaction zone is 30–50 g / L, and the sludge concentration in the membrane zone is 35–60 g / L.

[0013] Preferably, in step S2, the biogas circulation intensity is 25-35m. 3 / (m 2 ·h).

[0014] Preferably, in step S2, the cross-flow velocity of the biogas on the membrane surface is 0.1 to 0.3 m / s.

[0015] Preferably, in step S2, during the stable operation phase of the AnDMBR, the total solids content (TS) of the effluent from the membrane zone is 2–10 g / L.

[0016] The start-up method for the AnDMBR dynamic membrane in sludge anaerobic digestion provided by this invention also has the following beneficial effects:

[0017] 1. The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention achieves rapid increase in sludge operating concentration and rapid formation of dynamic membrane layer by adjusting the solid residence time, hydraulic residence time, biogas circulation intensity and membrane flux in the membrane zone during the start-up stage, so that the transmembrane pressure difference in the membrane zone reaches the expected value in a short time, thereby improving the production efficiency of the reactor.

[0018] 2. The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention adopts a shorter hydraulic retention time, a longer solids retention time and a smaller biogas circulation intensity in the early stage of start-up, which realizes the increase of sludge operating concentration and rapid formation of dynamic membrane, so that the transmembrane pressure difference in the membrane zone reaches the expected value in a short time. Then, the hydraulic retention time, solids retention time and biogas circulation intensity are adjusted according to the design conditions to maintain the transmembrane pressure difference in the membrane zone and realize the long-term stable operation of the reactor.

[0019] 3. The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention is simple to operate and can achieve the increase of sludge operating concentration and the formation of dynamic membrane in a short time, reducing the time cost of reactor start-up. It can also obtain a relatively dilute digested sludge liquid or clarified digested liquid according to the process target, which is convenient for resource recycling and improves the production efficiency of the reactor. It can be promoted.

[0020] 4. The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention can achieve a transmembrane pressure difference of 5-10 kPa and a membrane flux of 2-8 LMH in a short time, and maintain the stable operation of the AnDMBR system for more than 50 days. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0022] Figure 1 The AnDMBR system used in the start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention;

[0023] Figure 2 In the diagram, (a) is a cross-sectional schematic diagram of the dynamic membrane module in the membrane region before the AnDMBR starts up, (b) is a schematic diagram of the dynamic membrane layer formation process in the membrane region during the AnDMBR start-up stage, and (c) is a schematic diagram of the interface of the dynamic membrane layer in the membrane region during the AnDMBR stabilization stage.

[0024] Among them, 10 is the main reaction zone, 11 is the agitator, 12 is the biogas collection device, 20 is the membrane zone, 21 is the aeration pipe, 30 is the dynamic membrane module, 31 is the membrane frame, 32 is the flat sheet membrane, 33 is the membrane outlet, 34 is the sludge granules, 35 is the dynamic membrane layer, and K is the biogas direction. Detailed Implementation

[0025] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0026] This invention provides a method for starting up an AnDMBR dynamic membrane for sludge anaerobic digestion, using an AnDMBR system such as... Figure 1As shown, before the AnDMBR system is started, region 30 of the dynamic membrane module is as follows: Figure 2 As shown in (a), the dynamic membrane module 30 includes a membrane frame 31 and multiple flat sheet membranes 32 arranged parallel and equidistantly within the membrane frame 31. A membrane outlet 33 is provided above the flat sheet membranes 32. The sludge undergoes anaerobic digestion in the main reaction zone 10 of the AnDMBR. The digested sludge enters the membrane zone 20 through the sludge outlet. After being concentrated and separated by the dynamic membrane module 30, the digested sludge is returned to the main reaction zone 10 through the circulating sludge inlet to continue anaerobic digestion. A sludge inlet is provided at the bottom of the membrane zone 20, and a circulating sludge outlet is provided at the top, thereby establishing a sludge circulation pipeline that flows in the opposite direction to the sludge in the main reaction zone 10. A membrane outlet 33 and a biogas circulation pipeline are provided at the top of the membrane zone, and a conical sludge discharge outlet is provided at the bottom. Several aeration pipes 21 are arranged equidistantly at the bottom of the dynamic membrane module. The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention achieves rapid increase in sludge operating concentration and rapid formation of dynamic membrane layer 35 by adjusting the solid residence time, hydraulic residence time, biogas circulation intensity and membrane flux in the membrane zone during the start-up stage. This allows the transmembrane pressure difference in the membrane zone to reach the expected value in a short time, thereby improving the production efficiency of the reactor.

[0027] Combination Figure 2 As shown in (b) and (c), the start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion of the present invention includes the following steps:

[0028] S1, during the start-up phase of the AnDMBR, the hydraulic retention time in the membrane zone is controlled at 10–15 days, the solids retention time at 30–50 days, and the biogas circulation intensity in the membrane zone is controlled at 0–10 m³ / s. 3 / (m 2 •h), promoting rapid formation of dynamic films (see Figure 2 (as shown in (b));

[0029] The specific process is as follows: The method of this invention is applicable to systems with a sludge concentration of 30-50 g / L in the main reaction zone of an AnDMBR. During the start-up phase of the AnDMBR, it is necessary to control the biogas circulation intensity of the aeration at the bottom of the dynamic membrane module within a low range, while setting a shorter hydraulic retention time and a longer solids retention time, so that the dynamic membrane layer 35 can form rapidly and the transmembrane pressure difference in the membrane zone 20 can reach a higher level. Therefore, during the start-up phase of the AnDMBR, the hydraulic retention time in the membrane zone is controlled to be 10-15 days, the solids retention time to be 30-50 days, and the biogas circulation intensity in the membrane zone is controlled to be 0-10 m³ / s. 3 / (m 2·h), thereby forming a dynamic membrane layer 35 with a transmembrane pressure difference of 5 to 10 kPa on the surface of the flat membrane 32 of the membrane module in a short period of time (e.g., within 1 day). During the formation of the dynamic membrane layer 35, the membrane flux is stable at 2 to 8 LMH, and the daily sludge discharge depends on the volume of the reactor.

[0030] S2, during the stable operation phase of AnDMBR, after the dynamic film layer is formed (see...). Figure 2 As shown in (c), the circulation intensity of biogas is increased, and cross-flow of biogas is generated on the membrane surface to control the transmembrane pressure difference to 5-10 kPa.

[0031] The specific process is as follows: After the dynamic membrane layer is formed, the AnDMBR enters the stable operation stage. At this time, in order to maintain the transmembrane pressure difference at a predetermined value, it is necessary to aerate the biogas (i.e., the biogas at the bottom of the dynamic membrane module) to the desired value. Figure 2 (b)(c) In the biogas movement along the K direction from bottom to top, the circulation intensity is at a high level, thereby controlling the deposition of sludge particles 34 in the dynamic membrane layer and reducing membrane fouling. Therefore, during the stable operation phase of AnDMBR, the biogas circulation intensity is increased to 25-35 m 3 / (m 2 •h) The cross-flow generated by biogas on the membrane surface slows down the deposition of sludge on the membrane surface, wherein the cross-flow velocity of biogas on the membrane surface is 0.1-0.3 m / s; during the stable operation phase of AnDMBR, the sludge concentration in the main reaction zone is 30-50 g / L, and the sludge concentration in the membrane zone is 35-60 g / L; at this time, after continuous filtration by the dynamic membrane, a relatively dilute membrane effluent (i.e., digested sludge liquid or clarified digested liquid) can be obtained, wherein the total solids content (TS) of the membrane effluent is 2-10 g / L, and in a further preferred embodiment, the total solids content (TS) of the membrane effluent is 2-8 g / L.

[0032] Using the above-mentioned start-up method for the AnDMBR dynamic membrane of sludge anaerobic digestion, the AnDMBR system can be maintained in continuous and stable operation for more than 50 days without cleaning.

[0033] The following section provides a specific example to further illustrate the start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion according to the present invention.

[0034] Example 1

[0035] The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion in this embodiment is as follows:

[0036] For the AnDMBR system with an influent sludge concentration of 22.8 g / L, the biogas circulation intensity is controlled at 10 m³ / s during the start-up phase. 3 / (m 2By adjusting the membrane flux to 4.7 LMH and setting a shorter hydraulic retention time of 10 days, and by adjusting the daily sludge discharge to 23 L / d and setting a shorter solids retention time of 30 days, the TMP of the dynamic membrane rapidly reached 5–10 kPa within 1 day. Since a lower concentration of digested sludge is required subsequently, the hydraulic retention time and solids retention time are maintained at 10 days and 30 days respectively, and the biogas circulation intensity is increased to 30 m³ / h. 3 / (m 2 ·h), so that TMP is stabilized at around 5kPa, and digested sludge with a total solids content (TS) concentration of 7.5g / L is obtained by continuous filtration through dynamic membrane. At this time, the TS size in the main reaction zone is 36.5g / L and the TS size in the membrane zone is 43.3g / L. AnDMBR can operate stably for more than 50 days without cleaning under this condition.

[0037] Example 2

[0038] The start-up method of the AnDMBR dynamic membrane for sludge anaerobic digestion in this embodiment is as follows:

[0039] This implementation is largely the same as Example 1, with the following differences: the membrane flux is adjusted to 5.3 LMH, the daily sludge discharge is adjusted to 17.5 L / d, the solids retention time is adjusted to 40 days, and the biogas circulation intensity is increased to 35 m³ / d. 3 / (m 2 After continuous filtration through a dynamic membrane, a digested sludge with a total solids (TS) concentration of 8.5 g / L was obtained. At this time, the TS (total solids) in the main reaction zone was 41.6 g / L, and the TS in the membrane zone was 51.0 g / L. The AnDMBR operated stably for more than 50 days under this condition without cleaning.

[0040] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for starting up a dynamic AnDMBR membrane for sludge anaerobic digestion, characterized in that, Includes the following steps: S1, during the start-up phase of the AnDMBR, the hydraulic retention time in the membrane zone is controlled to be 10–15 days, the solids retention time to be 30–50 days, and the biogas circulation intensity in the membrane zone is controlled to be 0–10 m³ / s. 3 / (m 2 •h) promotes rapid formation of dynamic films. The specific process is as follows: The start-up method is applicable to systems with a sludge concentration of 30-50 g / L in the main reaction zone of the AnDMBR. During the start-up phase of the AnDMBR, the biogas circulation intensity of the aeration at the bottom of the dynamic membrane module is controlled within a low range, while a shorter hydraulic retention time and a longer solids retention time are set to enable rapid formation of the dynamic membrane layer and a higher transmembrane pressure difference in the membrane zone. During the start-up phase of the AnDMBR, the hydraulic retention time in the membrane zone is controlled to be 10-15 days, the solids retention time to be 30-50 days, and the biogas circulation intensity in the membrane zone is controlled to be 0-10 m³ / s. 3 / (m 2 •h) A dynamic membrane layer with a transmembrane pressure difference of 5-10 kPa is formed on the flat membrane surface of the membrane module within 1 day, wherein the membrane flux is 2-8 LMH during the formation of the dynamic membrane layer; S2) During the stable operation phase of AnDMBR, after the dynamic membrane layer is formed, the circulation intensity of biogas is increased, and cross-flow of biogas on the membrane surface is used to control the transmembrane pressure difference to 5-10 kPa. The specific process is as follows: After the dynamic membrane layer is formed, the AnDMBR enters the stable operation stage. At this time, the transmembrane pressure difference is maintained at a predetermined value, and the biogas circulation intensity of the aeration at the bottom of the dynamic membrane module is set at a high level to control the deposition of sludge particles in the dynamic membrane layer and reduce membrane fouling. During the stable operation stage of the AnDMBR, the biogas circulation intensity is increased to 25-35 m³ / h. 3 / (m 2 •h) The cross-flow generated by biogas on the membrane surface slows down the deposition of sludge on the membrane surface, wherein the cross-flow velocity of biogas on the membrane surface is 0.1 to 0.3 m / s; during the stable operation phase of AnDMBR, the sludge concentration in the main reaction zone is 30 to 50 g / L, and the sludge concentration in the membrane zone is 35 to 60 g / L; at this time, after continuous filtration by the dynamic membrane, a relatively dilute membrane effluent is obtained, wherein the total solids content (TS) of the membrane effluent is 2 to 10 g / L.

2. The start-up method for the AnDMBR dynamic membrane for sludge anaerobic digestion according to claim 1, characterized in that, In step S2, during the stable operation phase of the AnDMBR, the total solids content (TS) of the effluent from the membrane zone is 2–8 g / L.

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