Method and system for converting carbon source in sewage and storing carbon in sludge

Abstract

The invention discloses a sewage internal carbon source conversion and sludge internal carbon storage method and system, and the method comprises the following steps: sewage is introduced into a sewage internal carbon source conversion reaction zone, under anaerobic conditions, hydrolytic acidification bacteria are used for carrying out hydrolytic acidification reaction on organic particles in sewage, insoluble organic matters are decomposed into soluble organic matters, and the soluble organic matters are separated from the sewage. Converting into volatile fatty acid, and reacting for 4-5 hours; the method comprises the following steps: introducing sewage subjected to carbon source conversion into a carbon source storage reaction area in sludge, absorbing and adsorbing dissolved organic matters in the sewage by utilizing activated sludge subjected to endogenous respiration reaction, converting the dissolved organic matters into poly-beta-hydroxybutyric acid (PHB) and polyhydroxyvalerate (PHV), and storing the dissolved organic matters in the sludge for subsequent denitrification nitrogen removal, the reaction time is 3-4 hours. According to the invention, carbon source conversion in sewage and carbon storage in sludge can be better carried out, and the cost of sewage treatment chemicals is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a method and system for converting carbon sources in sewage and storing carbon in sludge. Background Art

[0002] At present, in the process of urban sewage treatment, the activated sludge method is still the mainstream treatment process. The ammonia nitrogen in the sewage needs to be removed through the autotrophic nitrification and heterotrophic denitrification of microorganisms. However, the carbon source is often the key factor affecting denitrification and phosphorus removal. On the one hand, factors such as the combined rainwater and sewage system lead to low influent concentrations in sewage treatment plants; on the other hand, the increasingly stringent requirements for the effluent quality of sewage treatment plants have further intensified the contradiction between insufficient influent carbon sources and the demand for carbon sources for denitrification and phosphorus removal. According to operating experience, when the carbon-nitrogen ratio is lower than 5, the biological denitrification and phosphorus removal efficiency of sewage treatment plants will not be too high. In order to solve the impact of insufficient carbon sources, it is usually necessary to consider adding external carbon sources. However, adding external carbon sources will increase the operating cost of sewage treatment plants and increase the sludge production of sewage treatment plants. In addition, colloids and organic particulate matter account for a high proportion of suspended matter in domestic sewage. Under normal circumstances, most of them are directly removed in the form of sludge and cannot be fully utilized. Therefore, the sludge production is large and the sludge treatment cost is high. Therefore, a method and system for carbon source conversion in sewage and carbon storage in sludge are proposed. Summary of the invention

[0003] The present invention solves the above technical problems through the following technical solutions, and the present invention includes the following processes: Principle of carbon source conversion in sewage: Under anaerobic conditions, microorganisms decompose insoluble organic matter into soluble organic matter, and decompose macromolecular organic matter into small molecular organic matter; under the action of acidifying bacteria, soluble organic matter and small molecular organic matter produced in the hydrolysis stage are further converted into volatile fatty acids (VFAs) and alcohols, etc.; acetogenic bacteria further convert volatile fatty acids (VFAs) and alcohols produced in the acidification stage into acetic acid, propionic acid, etc. These organic acids are high-quality carbon sources because they are easy to be used by microorganisms. These carbon sources can be used by denitrifying bacteria. In the denitrification process, denitrifying bacteria use these organic acids as electron donors to gradually reduce nitrate nitrogen to nitrogen gas, thereby achieving the removal of nitrogen in sewage. The present invention utilizes the insoluble organic matter in the original sewage for hydrolysis and acidification, and finally converts it into the carbon source required for denitrification. The advanced concept of treating pollution with pollution has been realized. Therefore, the denitrification efficiency is greatly improved without the need for an external carbon source, and a low-energy and low-chemical consumption denitrification method has been achieved, solving the biggest pain point in the current operation and maintenance of sewage treatment plants.

[0004] Principle of carbon source storage in sludge: There is a carbon source in sewage, but it needs to be stored before it can be used. When the environmental conditions are suitable (such as sufficient carbon source), microorganisms will store excess carbon sources in the form of poly-β-hydroxybutyric acid (PHB) and polyhydroxyvaleric acid (PHV) in the cells. When there are converted carbon sources in sewage, such as small molecular organic matter such as acetic acid and propionic acid, microorganisms will convert these carbon sources into PHB and PHV through a series of enzymatic reactions. This process is similar to the construction of an "energy storage warehouse". The present invention uses sludge after denitrification to synthesize internal carbon sources from organic acids converted in sewage under the action of microorganisms such as polyphosphate bacteria (PAOs) and polysaccharide bacteria (GAOs) that have the ability to store internal carbon sources, and store them in microorganisms. When the storage of carbon sources in sludge reaches the limit, a certain degree of mud-water separation is carried out, and the separated lower layer of sludge with rich internal carbon sources is transported to the denitrification reaction zone by power, thereby completing the utilization of internal carbon sources.

[0005] A system for converting carbon sources in sewage and storing carbon in sludge can be composed of a labyrinth-type horizontal baffled multi-stage reaction tank or an upflow-type internal carbon source conversion and storage reaction tank. Regardless of the method, the reaction sequence is: conversion first and then storage. Therefore, the front section is the carbon source conversion reaction zone in sewage, and the back section is the carbon source storage reaction zone in sludge. By controlling the flow rate, the sewage is kept in a suspended state in the reaction tank. The reaction time for carbon source conversion in sewage is 4 to 5 hours, and the reaction time for carbon source storage in sludge is 3 to 4 hours.

[0006] The conversion and storage of internal carbon sources need to be observed in real time, and the parameters should be adjusted to the optimal state according to the reaction conditions. Therefore, the upstream sewage internal carbon source conversion reaction zone is equipped with an online ORP meter, pH meter, and mud level meter; the downstream sludge internal carbon source storage reaction zone is equipped with an ORP meter and sludge concentration meter.

[0007] Compared with the prior art, the present invention has the following advantages: the method and system for converting carbon sources in sewage and storing carbon in sludge utilizes hydrolysis and acidification technology to convert colloids and organic particulate matter in sewage suspension to produce acid, thereby forming an efficient and high-quality denitrification carbon source - volatile fatty acids such as acetic acid and propionic acid, thereby improving the carbon-nitrogen ratio and carbon source quality of sewage, achieving efficient extreme biological denitrification treatment without the need for an external carbon source, and effectively reducing the cost of sewage treatment agents.

[0008] The activated sludge after the endogenous respiratory reaction is used to quickly absorb and adsorb the soluble organic matter in the sewage, and store it in the sludge in the form of internal carbon source, which reduces the concentration of free organic matter in the sewage and the energy consumption of oxidizing organic matter in the sewage, thereby realizing the efficient utilization of the internal carbon source in the sewage, while reducing the generation of residual sludge, saving energy consumption and the use of chemicals, and reducing the cost of sewage treatment.

[0009] It adopts a horizontal multi-stage baffle structure or an upflow structure, has no mechanical power equipment, controls the flow rate, and uses hydraulic action to achieve mixing reaction. It has a simple structure, is easy to construct, is maintenance-free, and is low-cost.

[0010] By setting up online pH meters, ORP meters, sludge concentration meters and mud level meters in the reaction zone, the reaction conditions of each reaction zone can be monitored in real time, and timely adjustments can be made to achieve stable and efficient reactions, making the system more worthy of popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is the principle diagram of horizontal baffle reaction of the present invention; Figure 2 It is the schematic diagram of the upflow reaction of the present invention.

[0012] Reference numerals: Figure 1 Middle: 1. Sewage inlet pipe, 2. Sewage distribution tank, 3. Sludge collecting pipe, 4. Residual sludge pipe, 5. Sludge inlet pipe, 6. Sludge distribution tank, 7. Outlet pipe, 8. Sludge collecting tank, 9. Sludge return pipe; 1-1, the first grid sewage carbon source conversion downward flow reaction zone, 1-2, the first grid sewage carbon source conversion upward flow reaction zone, 1-3, the second grid sewage carbon source conversion downward flow reaction zone, 1-4, the second grid sewage carbon source conversion upward flow reaction zone, 2-1, the first grid sludge carbon source storage downward flow reaction zone, 2-2, the second grid sludge carbon source storage upward flow reaction zone, 2-3, the third grid sludge carbon source storage downward flow reaction zone, 2-4, sludge carbon source storage upward flow reaction separation zone; A, reaction device pool wall and bottom plate, B, baffle plate, C vertical baffle plate; PH—online acid-base monitor; ORP—online oxidation-reduction potential monitor; DS—online mud level meter; MLSS—Online sludge concentration monitor; Figure 2 In: A. Reactor body, 1. Water distribution trough, 2. Water inlet baffle, 3. Mud distributor, 4. Reflection baffle, 5. Integrated clarifier, 1-1. Water inlet pipe, 1-2. Mud inlet pipe, 1-3. Drain pipe, 1-4. Sludge pipe, 1-5. Mud discharge pipe, DS - mud level meter. DETAILED DESCRIPTION

[0013] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0014] like Figure 1 to Figure 2As shown, this embodiment provides a technical solution: a method for converting carbon sources in sewage and storing carbon in sludge, comprising the following steps: The sewage is introduced into the carbon source conversion reaction zone in the sewage. Under anaerobic conditions, the organic particles in the sewage are hydrolyzed and acidified by hydrolytic acidifying bacteria to decompose the insoluble organic matter into soluble organic matter and convert it into volatile fatty acids. The reaction time is 4 to 5 hours. The sewage after carbon source conversion is introduced into the carbon source storage reaction zone in the sludge. The activated sludge after endogenous respiration reaction is used to absorb and adsorb the dissolved organic matter in the sewage, converting it into poly-β-hydroxybutyric acid (PHB) and polyhydroxyvaleric acid (PHV) and storing it in the sludge for subsequent denitrification and denitrification. The reaction time is 3 to 4 hours.

[0015] A system for carbon source conversion in sewage and carbon storage in sludge, a horizontal baffle implementation method, including: a water inlet pipe, a water distribution trough, a vertical baffle baffle, and a single group of upward and downward flow reaction zones formed by the baffle, and a mud discharge pipe arranged in the front-stage sewage carbon source conversion reaction zone; a mud inlet pipe, a mud distribution trough, a vertical baffle baffle, and an upward and downward flow reaction zone, a terminal mud-water separation zone, a mud discharge pipe, and a water outlet trough arranged in the rear-stage sludge carbon source storage reaction zone; and the number of upward and downward flow reaction zones is at least greater than two groups. The embodiment of the present application discloses a system for carbon source conversion in sewage and carbon storage in sludge, including a pool wall, a pool bottom, a vertical baffle baffle, and the baffle is cast with reinforced concrete or assembled with steel metal anti-corrosion plates, wherein the angle between the vertical plate of the baffle baffle and the inclined plate is 120 to 130 degrees, and the height between the lower edge of the inclined plate and the pool bottom is greater than 20 cm; the water distribution trough, the mud distribution trough, and the water outlet trough are made of steel for anti-corrosion; the mud collecting pipe is made of plastic or steel for anti-corrosion; The water distribution trough, mud distribution trough and water outlet trough are rectangular U-shaped structures, with an open top and closed left, right, front and back and bottom. The bottom has round holes with a hole diameter of 20-50mm, a hole spacing of 20-60cm, a trough width of 20-40cm and a trough height of 30-40cm. The trough body is horizontally suspended in the reaction area with a immersion depth of 10-20cm, and the short sides of the trough body are fixed to the pool wall.

[0016] As an implementation method, the mud collecting pipe at the bottom of the reaction zone has cross holes at an angle of 4 to 5 degrees facing downward, with a hole diameter of 20 to 40 cm and a hole spacing of 50 to 80 cm. The mud collecting pipe is installed at a clearance of 20 to 30 cm from the bottom of the pool. When the mud collecting pipe is more than 5 meters long, the outlet is located in the middle of the pipe. When the mud collecting pipe is less than or equal to 5 meters long, the outlet can be located at either end of the pipe.

[0017] As an implementation method, the sludge gas lift reflux device is respectively arranged in the anaerobic tank and the anoxic tank, wherein the anaerobic tank is arranged at the end, and the anoxic tank is arranged on both sides of the short side of the integrated clarification separator, and the air inlet pipe of the sludge gas lift reflux device is connected to the air supply pipe.

[0018] In the implementation method of the upward flow, the sewage passes through the water distribution troughs on both sides, first enters the downward vertical water distribution area, and then enters the sewage carbon source reaction conversion area at the bottom of the device through the baffle horizontal area. A reflective baffle is set at the bottom of the conversion area, so that the sewage entering from both sides rushes to the baffle and reflects to form a ring-shaped stirring effect. This reflection area is formed by a sludge layer formed by a large number of hydrolytic acidifying bacteria. Due to the increase in the water flow section in this area, the sewage flow rate decreases, which is conducive to the separation of high-density suspended solids, while ensuring that the mud and water are fully mixed. The interception effect of the sludge layer is used to intercept the colloids and particulate organic matter in the sewage. Through the action of hydrolytic acidifying bacteria, they are liquefied and decomposed into small molecular volatile fats, increasing the concentration of soluble organic matter in the sewage, reducing suspended solids in the sewage and reducing the amount of residual sludge generated.

[0019] After the reaction, the sewage continues to rise and enter the middle part of the reaction device, through the narrow flow area formed by the mud distributor and the integrated clarifier, and mixes with the sludge after the endogenous respiratory reaction discharged by the mud distributor. As the flow rate increases, the flow area becomes smaller, forming a higher flow rate, ensuring that the sludge after the endogenous respiratory reaction does not fall into the carbon source conversion zone in the lower sewage, and at the same time increasing the contact reaction intensity between sewage and sludge. The activated sludge after the endogenous respiratory reaction is used to adsorb, absorb, enrich and store the soluble volatile fatty acids in the sewage in the bacteria. Then it enters the integrated clarifier, and the gravity mud and water separation is carried out by using the difference in mud and water quality. Most of the sludge settles in the bottom sludge collection bucket and is then discharged from the sludge pipe into the subsequent anoxic denitrification device to denitrify the carbon source in the sludge, consume the carbon source in the sludge to regenerate the sludge, and the separated sewage enters the subsequent aerobic nitrification device through the drainage pipe to degrade ammonia nitrogen by nitrification reaction, thereby realizing the transfer and utilization of the carbon source in the sludge.

[0020] The two implementation schemes are generally used as an implementation method. An online pH meter and ORP meter are set in the middle of the carbon source conversion reaction zone in the front stage of sewage to mainly monitor the reaction state effect. A DS meter is set in the rear part to mainly monitor the sludge height in the pool to facilitate sludge discharge control. An MLSS meter and ORP meter are set at the rear end of the carbon source storage reaction zone in the rear stage of sludge to mainly monitor the effluent sludge concentration in order to control and adjust the sludge concentration and monitor the reaction state.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0022] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0023] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for converting carbon sources in sewage and storing carbon in sludge, characterized in that: The following steps are involved: The sewage is introduced into the carbon source conversion reaction zone in the sewage. Under anaerobic conditions, the organic particles in the sewage are hydrolyzed and acidified by hydrolytic acidifying bacteria to decompose the insoluble organic matter into soluble organic matter and convert it into volatile fatty acids. The reaction time is 4 to 5 hours. The sewage after carbon source conversion is introduced into the carbon source storage reaction zone in the sludge. The activated sludge after endogenous respiration reaction is used to absorb and adsorb the dissolved organic matter in the sewage, converting it into poly-β-hydroxybutyric acid (PHB) and polyhydroxyvaleric acid (PHV) and storing it in the sludge for subsequent denitrification and denitrification. The reaction time is 3 to 4 hours.

2. The method for converting carbon sources in sewage and storing carbon in sludge according to claim 1, characterized in that: In the carbon source conversion reaction zone in the sewage, the pH value is controlled to be 6.5-7.5 and the ORP value is 50-150mV; In the carbon source storage reaction zone in the sludge, the ORP value is controlled to be -50 to -200 mV and the sludge concentration value is 1000 to 2000 mg / L.

3. The method for converting carbon sources in sewage and storing carbon in sludge according to claim 1, characterized in that: In the carbon source conversion reaction zone in the sewage, the flow rate is controlled to keep the sewage in a suspended state, so as to promote full contact between organic particles and hydrolytic acidifying bacteria; In the carbon source storage reaction zone in the sludge, the activated sludge is fully mixed with the dissolved organic matter in the sewage by controlling the flow rate and sludge concentration, thereby improving the absorption and storage efficiency of the carbon source.

4. A system for converting carbon sources in sewage and storing carbon in sludge, based on the storage method according to any one of claims 1 to 3, characterized in that: The system comprises: A carbon source conversion reaction zone in sewage, used for carrying out a conversion reaction of the carbon source in sewage; The carbon source storage reaction zone in the sludge is used for carrying out the storage reaction of the carbon source in the sludge; The carbon source conversion reaction zone in the sewage and the carbon source storage reaction zone in the sludge are connected in sequence, and the sewage is kept in a suspended state in the reaction tank through a flow rate control device.

5. A system for converting carbon sources in sewage and storing carbon in sludge according to claim 4, characterized in that: The carbon source conversion reaction zone in the sewage is provided with an online pH meter, ORP meter and mud level meter for real-time monitoring of the reaction state and sludge height; The carbon source storage reaction zone in the sludge is provided with an online ORP meter and a sludge concentration meter for real-time monitoring of the reaction state and sludge concentration.

6. A system for converting carbon sources in sewage and storing carbon in sludge according to claim 5, characterized in that: The system includes a horizontal baffle system and an upflow system: Horizontal baffle system: including sewage inlet pipe, sewage distribution tank, sludge collecting pipe, residual sludge pipe, sludge inlet pipe, sludge distribution tank, outlet pipe, water collecting tank, sludge return pipe, and multiple upward and downward flow reaction zones formed by baffle baffles; Upflow system: includes reactor body, water distribution trough, water inlet baffle, mud distributor, reflective baffle, integrated clarifier, as well as water inlet pipe, mud inlet pipe, drainage pipe, sludge pipe and mud discharge pipe.

7. The system for converting carbon sources in sewage and storing carbon in sludge according to claim 4, characterized in that: In the horizontal fold system, the included angle between the vertical plate of the baffle and the inclined plate is 120 to 130 degrees, and the height between the lower edge of the inclined plate and the pool bottom is greater than 20 cm; The water distribution trough, mud distribution trough and water outlet trough are rectangular U-shaped structures, with an open top and closed left, right, front and back and bottom. The bottom has round holes with a hole diameter of 20-50mm, a hole spacing of 20-60cm, a trough width of 20-40cm and a trough height of 30-40cm. The mud collecting pipe has cross holes with an angle of 4 to 5 degrees and faces downward, with a hole diameter of 20 to 40 cm, a hole spacing of 50 to 80 cm, and an installation height of 20 to 30 cm above the pool bottom; In the upflow system, sewage enters the downward vertical water distribution area through the water distribution troughs on both sides, and then enters the sewage carbon source reaction conversion area at the bottom of the device through the baffled horizontal area. A reflective baffle is set at the bottom of the conversion area to reflect and form a ring-shaped stirring effect. After the reaction, the sewage continues to rise and enters the middle part of the reaction device, passes through the narrow flow zone formed by the mud distributor and the integrated clarifier, and is mixed with the sludge after the endogenous respiratory reaction discharged from the mud distributor, and then enters the integrated clarifier for mud-water separation.

8. The system for converting carbon sources in sewage and storing carbon in sludge according to claim 4, characterized in that: The system also includes a sludge gas lift reflux device, which is respectively arranged in the anaerobic tank and the anoxic tank, wherein the anaerobic tank is arranged at the end, and the anoxic tank is arranged on both sides of the short side of the integrated clarification separator. The air inlet pipe of the sludge gas lift reflux device is connected to the air supply pipe for recycling the sludge.

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