A Pretreatment Process for Anaerobic Digestion Sludge in the Digester of an Urban Sewage Treatment Plant

Abstract

A pretreatment process for anaerobic digestion sludge in a municipal sewage treatment plant, comprising the following steps: Step 1, slurry distribution; Step 2, static thickening; Step 3, slurry flora cultivation; Step 4, primary slurry dewatering; Step 5, secondary slurry dewatering; Step 6, aerobic treatment of slurry; Step 7, alkali treatment of slurry; Step 8, slurry mixing; Step 9, slurry heating; In the present invention, the slurry produced by the sewage treatment plant is divided into two portions. One portion is used to cultivate anaerobic flora in the sludge through a flora cultivation device. The cultivation of anaerobic flora can reduce the sludge digestion gas production time in the digestion tank. The other portion undergoes two-stage dewatering, and the slurry dewatered by the centrifuge undergoes an aerobic reaction to allow the rapid growth of aerobic microorganisms, enabling more microbial cells to be dissolved in the subsequent alkali treatment. The sludge after pretreatment has increased sludge organic matter content, thereby improving the unit gas production rate of the sludge in the digestion tank in the next step.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment devices or equipment, and specifically relates to a pretreatment process for anaerobic digestion sludge in a digester of a municipal sewage plant. Background Art

[0002] At present, the treatment technology of residual sludge from urban sewage treatment plants has become the key development direction of urban environmental pollution prevention and control and green low-carbon resource recycling. Anaerobic digestion of sludge refers to the process in which facultative bacteria and anaerobic bacteria decompose the biodegradable organic matter in the sludge into carbon dioxide, methane and water under anaerobic conditions to stabilize the sludge. It is one of the effective means of sludge reduction, stabilization, harmlessness and resource treatment. Through investigation, it was found that the main factors affecting the gas production rate of anaerobic digestion of digester sludge are low organic matter content in digested sludge, uneven sludge pH, large sludge temperature fluctuations, mud blocking pipelines and other problems. At present, the sludge before digestion is mostly treated by one-time dehydration and alkali treatment. This process does not recycle the heat generated by alkali treatment, resulting in energy waste. Although the sludge contains microorganisms, the number is small. Although simple alkali treatment can destroy the cell wall of microorganisms and dissolve organic matter, the increase in the organic matter content in the sludge is still not ideal due to the small number of microorganisms. In addition, anaerobic microorganisms are not pre-cultured, so the sludge digestion takes a long time and the gas production rate is low. In order to solve the above technical problems, the present invention provides a sludge pretreatment process for anaerobic digestion in a digester of a municipal sewage plant. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the above-mentioned prior art and provide an anaerobic digestion sludge pretreatment process for a digester of an urban sewage plant, which is simple in process, saves resources, reduces the sludge digestion and gas production time in the digester, and improves the unit sludge gas production rate.

[0004] The technical solution adopted to solve the above technical problems is: a pretreatment process of anaerobic digestion sludge in a digester of a municipal sewage plant, comprising the following steps:

[0005] Step 1: Mud distribution: The sedimentation mud from the sewage treatment plant is passed into the mud distribution tank, and the mud in the mud distribution tank is divided into mud one and mud two at a ratio of 1:5;

[0006] Step 2, static concentration: the slurry 1 is concentrated by gravity in a static concentration tank to obtain product 1;

[0007] Step 3, culturing the mud flora: passing the product 1 into the flora culturing device, heating, stirring and circulating the mud in the flora culturing device so that the temperature of the mud in the flora culturing device is maintained at 30° C. to 36° C., thereby obtaining the product 2;

[0008] Step 4: Primary dewatering of the slurry: Feed Slurry 2 into the coagulation device, add a flocculant, and let it stand for 2 - 3 hours to allow the slurry to form lumps and settle, obtaining Product 3;

[0009] Step 5: Secondary dewatering of the slurry: Pass Product 3 through a first grinder and a centrifuge for further dewatering to obtain Product 4;

[0010] Step 6: Aerobic treatment of the slurry: Conduct an aerobic reaction on Product 4 in an aerobic device and supply oxygen to the aerobic device to obtain Product 5;

[0011] Step 7: Alkaline treatment of the slurry: Feed Product 5 into an alkaline solution regulating device, and at the same time introduce the alkaline solution prepared in the alkaline solution preparation device to conduct alkaline treatment on Product 5. Use a stirrer to mix the alkaline solution and Product 5 evenly to obtain Product 6. At the same time, introduce the hot water prepared in the alkaline solution preparation device into the bacterial community cultivation device to provide heat for it;

[0012] Step 8: Slurry mixing: Feed Product 2, Product 6, and the digested sludge from the digestion tank into a mixing tank and mix them evenly with a stirrer. Adjust the feeding amount of Product 2 to make the pH value of the mixed slurry 6 - 7. Grind the mixed slurry through a second grinder to obtain Product 7;

[0013] Step 9: Slurry heating: Feed Product 7 into a slurry hot water exchanger and keep the slurry temperature at 36°C - 37°C to obtain Product 8.

[0014] The alkaline solution preparation device of the present invention is as follows: An alkaline preparation stirrer is arranged inside the lime reaction tank. The second water tank is connected to the inlet of the lime reaction tank through a second clean water pump installed on the pipeline. The outlet of the lime reaction tank is connected to the alkaline solution regulating device through an alkaline solution pump installed on the pipeline. A cold water heating tank is concentrically arranged outside the lime reaction tank. A second temperature detector is arranged at the bottom of the cold water heating tank. The water in the cold water tank enters the upper part of the interlayer formed by the cold water heating tank and the lime reaction tank through a cold water pump. The lower part of the interlayer formed by the cold water heating tank and the lime reaction tank is connected to the inlet of the hot water tank through a first water outlet valve installed on the pipeline. The outlet of the hot water tank is connected to the inlet of the bacterial community cultivation device through a hot water pump installed on the pipeline. The inlet of the cold water tank is connected to the outlet of the bacterial community cultivation device.

[0015] The bacterial community cultivation device of the present invention is as follows: The cultivation pool has a sealed structure, and the sealed gas uses the biogas generated by the digestion tank. A heating coil is arranged at the bottom of the cultivation pool. The inlet of the heating coil is connected to the hot water pump, and the outlet is connected to the cold water tank through a first temperature detector and a first water outlet valve installed on the pipeline. A slurry circulation pump is arranged outside the cultivation pool, and a cultivation pool stirrer is arranged at the upper part of the cultivation pool. The outlet of the cultivation pool is connected to the inlet of the mixing tank through a first slurry pump installed on the pipeline.

[0016] When the temperature difference between the upper and lower parts inside the cultivation tank of the present invention is greater than 5°C, start the cultivation tank stirrer and the mud circulation pump; when the temperature difference between the upper and lower parts inside the cultivation tank is less than 1°C, turn off the cultivation tank stirrer and the mud circulation pump, so that the mud temperature inside the cultivation tank is always maintained at 30°C - 36°C.

[0017] The aerobic device of the present invention is as follows: an air duct is provided at the top of the aerobic tank, the air duct is connected to a ventilator, the ventilator feeds oxygen into the air duct of the aerobic tank, and branch pipes extending into the aerobic tank are vertically arranged on the air duct at intervals of 50 cm, and air outlet holes are evenly processed on the branch pipes.

[0018] The lower part of the aerobic tank of the present invention is a V-shaped chamber and the upper part is a rectangular chamber, and the top of the aerobic tank is open.

[0019] The coagulation device of the present invention is as follows: the flocculant is sent into the flocculant preparation tank through a screw conveyor, several groups of flocculant stirrers are arranged in the flocculant preparation tank, the first water tank is connected to the flocculant preparation tank through a first water pump installed on the pipeline, the outlet of the flocculant preparation tank is connected to the coagulation tank through a flocculant supply pump installed on the pipeline, the second mud is introduced into the coagulation tank for precipitation and caking, and the outlet of the coagulation tank is connected to the inlet of the first grinder through a second mud pump installed on the pipeline.

[0020] A sludge scraper is provided at the lower part of the static thickening tank of the present invention.

[0021] The pH value of the alkali solution prepared in the alkali solution preparation device in step seven of the present invention is 12.

[0022] The present invention has the following advantages compared with the prior art:

[0023] (1) The present invention divides the mud produced by the sewage treatment plant into two parts. One part cultivates anaerobic bacteria in the sludge through the bacterial community cultivation device. The cultivation of anaerobic bacteria can reduce the sludge digestion gas production time in the digestion tank. The other part undergoes two dehydrations, and the mud dehydrated by the centrifuge undergoes an aerobic reaction to allow the rapid growth of aerobic microorganisms, enabling the next alkali treatment to dissolve more microbial cells and increasing the sludge organic matter content.

[0024] (2) When preparing the alkali solution in the present invention, both alkali solution and hot water are produced. The heat released when preparing the alkali solution by adding water to lime is used to provide heat for culturing the bacterial community, and no additional heat is required for culturing the bacterial community. The prepared alkali solution is introduced into the alkali solution regulating device for alkali treatment of the mud. This process realizes the recycling of heat and water, improves the energy utilization efficiency, and saves resources.

[0025] (3) The mixing tank of the present invention can evenly stir the cooked mud, the anaerobically cultivated mud, and the mud after alkali treatment, and grind the sludge into fine particles without clogging the tubular hydrothermal exchanger and the pipeline.

[0026] (4) The digester slurry prepared by the present invention, compared with conventional slurry, increases the aerobic treatment of sludge, improves the number of aerobic microorganisms in the slurry, enables more organic matter to be dissolved during the alkali treatment of sludge, increases the organic matter content in the sludge, adds an anaerobic flora cultivation step, increases the number of anaerobic microorganisms in the sludge, shortens the gas production time during sludge digestion. The two treated slurries and the cooked slurry are mixed in a mixing tank to make the slurry pH uniform. The pretreated digested slurry is rich in anaerobic flora, organic matter and has a uniform pH, which can reduce the digestion time of the digester slurry in the next step and improve the unit gas production rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of an embodiment of the present invention.

[0028] Figure 2 is Figure 1 the schematic structural diagram of the flora cultivation device 3 in

[0029] Figure 3 is Figure 1 the schematic structural diagram of the coagulation device 4 in

[0030] Figure 4 is Figure 1 the schematic structural diagram of the alkali solution preparation device 9 in

[0031] In the figure: 1, slurry distribution tank; 2, static thickening tank; 3, flora cultivation device; 4, coagulation device; 5, first grinder; 6, centrifuge; 7, aerobic device; 8, alkali solution regulating device; 9, alkali solution preparation device; 10, mixing tank; 11, second grinder; 12, slurry hot water exchanger; 3-1, culture tank body; 3-2, first slurry pump; 3-3, first temperature detector; 3-4, first water outlet valve; 3-5, slurry circulation pump; 3-6, culture tank stirrer; 3-7, heating coil; 4-1, screw conveyor; 4-2, flocculant preparation tank; 4-3, flocculant stirrer; 4-4, first water pump; 4-5, first water tank; 4-6, flocculant supply pump; 4-7, coagulation tank body; 4-8, second slurry pump; 7-1, ventilator; 7-2, air duct; 7-3, branch pipe; 7-4, aerobic tank; 9-1, cold water heating tank; 9-2, lime reaction tank; 9-3, alkali preparation stirrer; 9-4, second water pump; 9-5, second water tank; 9-6, alkali solution pump; 9-7, second temperature detector; 9-8, second water outlet valve; 9-9, hot water tank; 9-10, hot water pump; 9-11, cold water tank; 9-12, cold water pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described in detail below with reference to the drawings and embodiments, but the present invention is not limited to these embodiments.

[0033] Example 1

[0034] In Figures 1 to 4 , an anaerobic digestion sludge pretreatment process for a digestion tank in an urban sewage treatment plant according to the present invention includes the following steps:

[0035] Step 1, Mud distribution: The sedimentation mud from the sewage treatment plant is introduced into the mud distribution tank 1. The mud in the mud distribution tank 1 is divided into Mud 1 and Mud 2 in a ratio of 1:5. Mud 1 is pumped into the static thickening tank 2, and Mud 2 is pumped into the coagulation device 4;

[0036] Step 2, Static thickening: Mud 1 is thickened by its own weight in the static thickening tank 2 to obtain Product 1. Product 1 is scraped towards the bottom of the cone of the static thickening tank by a sludge scraper and conveyed to the flora culturing device 3 through a pipeline;

[0037] Step 3, Mud flora culturing: After Product 1 is introduced into the flora culturing device 3, by heating, stirring, and external mud circulation of the mud in the flora culturing device 3, Product 2 is obtained. At this time, the biogas generated by the digestion tank needs to be led to the culture tank 3-1 to ensure an anaerobic environment; specifically, the flora culturing device 3 is composed of a culture tank body 3-1, a first mud pump 3-2, a first temperature detector 3-3, a first water outlet valve 3-4, a mud circulation pump 3-5, and a culture tank stirrer 3-6. The culture tank 3-1 is a sealed structure, and the sealing gas is the biogas generated by the digestion tank. A number of groups of temperature measuring devices are evenly arranged along the pool wall inside the culture tank 3-1 for measuring the mud temperature in the culture tank 3-1. A heating coil 3-7 is installed at the bottom of the culture tank 3-1. The inlet of the heating coil 3-7 is connected to the hot water pump 9-10, and the outlet is connected to the cold water tank 9-11 through the first temperature detector 3-3 and the first water outlet valve 3-4 installed on the pipeline. The hot water generated by the alkali solution preparation device 9 enters the heating coil 3-7 to heat the mud in the culture tank 3-1. After heat exchange, the cold water discharged from the heating coil 3-7 is circulated into the alkali solution preparation device 9 to continue heating, realizing the recycling of heat and water. A mud circulation pump 3-5 is arranged outside the culture tank 3-1, and a culture tank stirrer 3-6 is arranged above the culture tank 3-1. The mud circulation pump 3-5 is used to convey the mud at the bottom of the culture tank 3-1 to the top of the culture tank 3-1. The culture tank stirrer 3-6 makes the mud temperature in the tank uniform through stirring. The outlet of the culture tank 3-1 is connected to the inlet of the mixing tank 10 through the first mud pump 3-2 installed on the pipeline to convey the cultured flora mud to the mixing tank 10. When the temperature difference between the upper and lower parts in the culture tank 3-1 is greater than 5°C, the culture tank stirrer 3-6 and the mud circulation pump 3-5 are started. When the temperature difference between the upper and lower parts in the culture tank 3-1 is less than 1°C, the culture tank stirrer 3-6 and the mud circulation pump 3-5 are turned off to keep the mud temperature in the culture tank 3-1 at 30°C - 36°C all the time.

[0038] Step 4: Primary dehydration of the slurry: Feed the second slurry into the coagulation device 4, add a flocculant, and let it stand for 2 - 3 hours to make the slurry agglomerate and precipitate, obtaining the third product. Specifically, the coagulation device 4 is composed of a screw conveyor 4-1, a flocculant preparation tank 4-2, a flocculant stirrer 4-3, a first water pump 4-4, a first water tank 4-5, a flocculant supply pump 4-6, a coagulation tank body 4-7, and a second slurry pump 4-8 connected. The flocculant is fed into the flocculant preparation tank 4-2 through the screw conveyor 4-1. There are several groups of flocculant stirrers 4-3 arranged in the flocculant preparation tank 4-2. The first water tank 4-5 is connected to the flocculant preparation tank 4-2 through the first water pump 4-4 installed on the pipeline. The outlet of the flocculant preparation tank 4-2 is connected to the coagulation tank 4-7 through the flocculant supply pump 4-6 installed on the pipeline. The second slurry is fed into the coagulation tank 4-7 and precipitates and agglomerates under the action of the flocculant to complete the primary dehydration. The outlet of the coagulation tank 4-7 is connected to the inlet of the first grinder 5 through the second slurry pump 4-8 installed on the pipeline.

[0039] Step 5: Secondary dehydration of the slurry: Pass the third product through the first grinder 5 and the centrifuge 6 in sequence for further dehydration, obtaining the fourth product.

[0040] Step 6: Aerobic treatment of the slurry: Carry out an aerobic reaction on the fourth product in the aerobic device 7, supply oxygen to the aerobic device 7 to increase the growth rate of aerobic organisms and increase the number of aerobic microorganisms, obtaining the fifth product. Specifically, the aerobic device 7 is composed of a ventilator 7-1, an air duct 7-2, a branch pipe 7-3, and an aerobic tank 7-4 connected. The lower part of the aerobic tank 7-4 is a V-shaped chamber and the upper part is a rectangular chamber, and the top of the aerobic tank 7-4 is open. An air duct 7-2 is arranged at the top of the aerobic tank 7-4, and the air duct 7-2 is connected to the ventilator 7-1. The ventilator 7-1 feeds oxygen into the aerobic tank 7-2. The branch pipes 7-3 extending into the aerobic tank 7-4 are vertically arranged at intervals of 50 cm on the air duct 7-2, and air outlet holes are uniformly processed on the branch pipes 7-3 to supply oxygen into the aerobic tank 7-4 through the air outlet holes.

[0041] Step 7. Alkaline treatment of the slurry: Feed Product 5 into the alkaline solution adjusting device 8, and simultaneously feed the alkaline solution with a pH of 12 prepared in the alkaline solution preparation device 9 to perform alkaline treatment on Product 5. Use a stirrer to evenly stir the alkaline solution and Product 5 to obtain Product 6. Specifically, the alkaline solution preparation device 9 is composed of a cold water heating tank 9-1, a lime reaction tank 9-2, an alkaline preparation stirrer 9-3, a second water pump 9-4, a second water tank 9-5, an alkaline solution pump 9-6, a second temperature detector 9-7, a second water outlet valve 9-8, a hot water tank 9-9, a hot water pump 9-10, a cold water tank 9-11, and a cold water pump 9-12. The lime reaction tank 9-2 is made of aluminum plastic steel with good heat dissipation effect. An alkaline preparation stirrer 9-3 is arranged inside the lime reaction tank 9-2. The second water tank 9-5 is connected to the inlet of the lime reaction tank 9-2 through the second water pump 9-4 installed on the pipeline. The outlet of the lime reaction tank 9-2 is connected to the alkaline solution adjusting device 8 through the alkaline solution pump 9-6 installed on the pipeline. A cold water heating tank 9-1 is concentrically arranged outside the lime reaction tank 9-2. Heat insulation materials are wound around the cold water heating tank 9-1 to prevent heat loss. A second temperature detector 9-7 is arranged at the bottom of the cold water heating tank 9-1. The water in the cold water tank 9-11 enters the upper part of the interlayer formed by the cold water heating tank 9-1 and the lime reaction tank 9-2 through the cold water pump 9-12. The lower part of the interlayer formed by the cold water heating tank 9-1 and the lime reaction tank 9-2 is connected to the inlet of the hot water tank 9-9 through the first water outlet valve 9-8 installed on the pipeline. The outlet of the hot water tank 9-9 is connected to the inlet of the flora cultivation device 3 through the hot water pump 9-10 installed on the pipeline. The inlet of the cold water tank 9-11 is connected to the outlet of the flora cultivation device 3. Add quicklime and water into the lime reaction tank 9-2, recover the large amount of heat released by the addition of water to quicklime, obtain the alkaline solution and hot water. The alkaline solution flows into the alkaline solution adjusting device 8, and the hot water flows into the heating coil 3-7 to provide heat for the cultivation pool 3-1. After the hot water exchanges heat and cools down, it continues to flow to the cold water tank 9-11 for heating and is recycled.

[0042] Step 8. Slurry mixing: Feed Product 2, Product 6, and the digested sludge from the digestion tank into the mixing tank 10 and mix them evenly through a stirrer. Adjust the feeding amount of Product 2 to make the pH value of the mixed slurry 6-7. Grind the mixed slurry through the second grinder 11 to obtain Product 7.

[0043] Step 9. Slurry heating: Feed Product 7 into the slurry hot water exchanger 12 and keep the slurry temperature at 36°C - 37°C to obtain Product 8.

Claims

1. A pretreatment process for anaerobic digestion sludge in a digestion tank of an urban sewage treatment plant, characterized in that It includes the following steps: Step 1, Mud distribution: Feed the sediment mud from the sewage treatment plant into the mud distribution tank (1). The mud in the mud distribution tank (1) is divided into Mud 1 and Mud 2 at a ratio of 1:5; Step 2, Static concentration: Concentrate Mud 1 in the static concentration tank (2) by its own weight to obtain Product 1; Step 3, Mud flora cultivation: Feed Product 1 into the flora cultivation device (3). By heating, stirring, and external mud circulation of the mud in the flora cultivation device (3), keep the temperature of the mud in the flora cultivation device (3) at 30°C - 36°C to obtain Product 2; The described flora cultivation device (3) is: The cultivation tank (3-1) is of a sealed structure, and the sealed gas uses the biogas generated by the digester. A heating coil (3-7) is arranged at the bottom of the cultivation tank (3-1). The inlet of the heating coil (3-7) is connected to the hot water pump (9-10), and the outlet is connected to the cold water tank (9-11) through the first temperature detector (3-3) and the first water outlet valve (3-4) installed on the pipeline. A mud circulation pump (3-5) is arranged outside the cultivation tank (3-1), a cultivation tank stirrer (3-6) is arranged at the upper part of the cultivation tank (3-1), and the outlet of the cultivation tank (3-1) is connected to the inlet of the mixing tank (10) through the first mud pump (3-2) installed on the pipeline; Step 4, Primary mud dehydration: Feed Mud 2 into the coagulation device (4), add a flocculant, and let it stand for 2 - 3 hours to make the mud caking and sedimentation to obtain Product 3; Step 5, Secondary mud dehydration: Further dehydrate Product 3 through the first grinder (5) and the centrifuge (6) in sequence to obtain Product 4; Step 6, Aerobic treatment of mud: Conduct an aerobic reaction on Product 4 in the aerobic device (7), supply oxygen to the aerobic device (7) to obtain Product 5; The described aerobic device (7) is: An air duct (7-2) is arranged at the top of the aerobic tank (7-4). The air duct (7-2) is connected to the ventilator (7-1). The ventilator (7-1) feeds oxygen into the air duct (7-2) of the aerobic tank. The air duct (7-2) is vertically provided with branch pipes (7-3) extending into the aerobic tank (7-4) at intervals of 50 cm. The branch pipes (7-3) are evenly processed with air holes. The lower part of the aerobic tank (7-4) is a V-shaped chamber, the upper part is a rectangular chamber, and the top of the aerobic tank (7-4) is open; Step 7, Alkali treatment of mud: Feed Product 5 into the alkali liquid adjustment device (8), and at the same time feed the alkali liquid prepared in the alkali liquid preparation device (9). Conduct alkali treatment on Product 5, and stir the alkali liquid and Product 5 evenly by the stirrer to obtain Product 6. At the same time, feed the hot water prepared in the alkali liquid preparation device (9) into the flora cultivation device (3) to provide heat source for it. The pH of the alkali liquid prepared in the alkali liquid preparation device (9) is 12; The described lye preparation device (9) is as follows: An alkali preparation stirrer (9-3) is arranged inside the lime reaction tank (9-2). The second water tank (9-5) is connected to the inlet of the lime reaction tank (9-2) through a second clean water pump (9-4) installed on the pipeline. The outlet of the lime reaction tank (9-2) is connected to the lye regulating device (8) through a lye pump (9-6) installed on the pipeline. A cold water heating tank (9-1) is concentrically arranged outside the lime reaction tank (9-2). A second temperature detector (9-7) is arranged at the bottom of the cold water heating tank (9-1). The water in the cold water tank (9-11) enters the upper part of the interlayer formed by the cold water heating tank (9-1) and the lime reaction tank (9-2) through a cold water pump (9-12). The lower part of the interlayer formed by the cold water heating tank (9-1) and the lime reaction tank (9-2) is connected to the inlet of the hot water tank (9-9) through a first water outlet valve (9-8) installed on the pipeline. The outlet of the hot water tank (9-9) is connected to the inlet of the flora cultivation device (3) through a hot water pump (9-10) installed on the pipeline. The inlet of the cold water tank (9-11) is connected to the outlet of the flora cultivation device (3). Step Eight, Mud Mixing: Feed Product Two, Product Six, and the digested sludge from the digestion tank into the mixing tank (10) and mix them evenly through a stirrer. Adjust the feeding amount of Product Two to make the pH value of the mixed mud be 6 - 7. Grind the mixed mud through the second grinder (11) to obtain Product Seven. Step Nine, Mud Heating: Feed Product Seven into the mud hot water exchanger (12) and keep the mud temperature at 36°C - 37°C to obtain Product Eight.

2. The anaerobic digestion sludge pretreatment process for the digester of an urban sewage treatment plant according to claim 1, characterized in that: When the temperature difference between the upper and lower parts inside the cultivation tank (3-1) is greater than 5°C, start the cultivation tank stirrer (3-6) and the mud circulation pump (3-5). When the temperature difference between the upper and lower parts inside the cultivation tank (3-1) is less than 1°C, turn off the cultivation tank stirrer (3-6) and the mud circulation pump (3-5) to keep the mud temperature inside the cultivation tank (3-1) at 30°C - 36°C all the time.

3. A pretreatment process for anaerobic digestion sludge in a digestion tank of an urban sewage treatment plant according to claim 1, characterized in that The described coagulation device (4) is as follows: The flocculant is fed into the flocculant preparation tank (4-2) through a screw conveyor (4-1). Several groups of flocculant stirrers (4-3) are arranged inside the flocculant preparation tank (4-2). The first water tank (4-5) is connected to the flocculant preparation tank (4-2) through a first clean water pump (4-4) installed on the pipeline. The outlet of the flocculant preparation tank (4-2) is connected to the coagulation tank (4-7) through a flocculant supply pump (4-6) installed on the pipeline. Mud Two is fed into the coagulation tank (4-7) for precipitation and caking. The outlet of the coagulation tank (4-7) is connected to the inlet of the first grinder (5) through a second mud pump (4-8) installed on the pipeline.

4. A pretreatment process for anaerobic digestion sludge in a municipal sewage treatment plant according to claim 1, characterized in that: A sludge scraper is arranged at the lower part of the static thickener (2).

Images