A device and method for treating excess sludge

Abstract

The present invention discloses a device and method for treating excess sludge, comprising an excess sludge nitrogen-phosphorus separation unit, a nitrification unit, an anaerobic ammonium oxidation unit, and an advanced treatment unit; the excess sludge undergoes anaerobically phosphorus release in the excess sludge nitrogen-phosphorus separation unit, and the phosphorus in the supernatant is reused for farmland as phosphate fertilizer; the dephosphorized excess sludge undergoes sludge fermentation in the excess sludge nitrogen-phosphorus separation unit; the sludge fermentation product enters the nitrification unit and the anaerobic ammonium oxidation unit for decarbonization and nitrogen removal; and after further purification in the advanced treatment unit, the tail water is returned to the natural water system. The present invention has the distinct characteristics of being ecologically friendly, economically efficient, and can achieve sludge reduction, stabilization, harmlessness, and resource utilization. Nitrogen-phosphorus separation and agricultural use of phosphorus prior to sludge fermentation not only help to simultaneously address the current increasing phosphorus demand and excess sludge treatment volume, but also reduce the phosphorus load of subsequent treatment units, facilitating the long-term stable operation of the device, and having practical significance and engineering value.

Description

Technical Field

[0001] The invention belongs to the field of sludge biological treatment, relates to the treatment of excess sludge, and in particular to a treatment device and method for excess sludge. Background Art

[0002] In recent years, with the rapid construction of sewage treatment plants, the annual production of excess sludge has increased dramatically. Excess sludge treatment technology has become a key factor restricting the effectiveness of sewage treatment. Excess sludge is high in organic matter and rich in nutrients such as nitrogen (N) and phosphorus (P). Phosphorus is a critical resource, alongside energy and water, and is widely used in modern industrial and agricultural production, playing a vital role in human survival and development.

[0003] Phosphate fertilizer is one of the factors that restrict the normal growth of crops and is an essential consumable in agricultural production. Currently, the main source of phosphorus is the mining of underground phosphate rock, of which phosphate rock is used in agricultural production as high as 82%. As a non-renewable resource, the demand for phosphorus has far exceeded the supply. It is estimated that by 2050, the consumption of phosphate will reach 1.0×10 9 t, global phosphorus shortage will become one of the most daunting challenges of the 21st century.

[0004] Clearly, agricultural use of sewage sludge is an effective way to dispose of sludge and recover nitrogen and phosphorus. However, direct agricultural use of unstabilized and harmless sludge presents hidden risks, primarily related to the impact of sludge application on plants and the migration of heavy metals within and from soil to plants. Studies have shown that after 10 years of continuous sludge application on experimental land, soil levels of mercury, cadmium, tin, zinc, and copper were elevated, severely contaminating rice, wheat, corn, and vegetables grown there. Currently, commonly used methods for treating and disposing of excess sludge include sludge concentration and dewatering, sanitary landfill, and sludge incineration. Investment in sludge treatment facilities accounts for 30% to 40% of the total investment in a sewage treatment plant. Existing sludge treatment technologies still suffer from numerous challenges, including poor volume reduction, complex operations, numerous steps, and low resource recovery rates. These technologies fail to meet the requirements for stabilization, harmlessness, and resource utilization. Therefore, the development of an environmentally friendly and cost-effective excess sludge treatment and disposal technology is an urgent need. Summary of the Invention

[0005] In the face of the long-term increasing demand for phosphorus and the amount of excess sludge to be treated, the present invention provides a device and method for treating excess sludge. The device and method of the present invention have the distinct characteristics of being eco-friendly, environmentally friendly, economical and efficient, and can achieve sludge reduction, stabilization, harmlessness and resource utilization, which are of great practical significance and engineering value.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention first provides a device for treating excess sludge, which includes a excess sludge nitrogen-phosphorus separation unit, a nitrification unit, an anaerobic ammonium oxidation unit, and a deep treatment unit connected in sequence; wherein, the excess sludge nitrogen-phosphorus separation unit is provided with a first agitator and a first outlet pipe, the bottom of the nitrification unit is provided with an aeration device, the anaerobic ammonium oxidation unit is provided with a second agitator and a second outlet pipe, and the deep treatment unit is provided with a third outlet pipe; the excess sludge nitrogen-phosphorus separation unit is also connected to the anaerobic ammonium oxidation unit, a first electric valve is installed between the excess sludge nitrogen-phosphorus separation unit and the nitrification unit, and a second electric valve is installed between the nitrification unit and the anaerobic ammonium oxidation unit.

[0008] As a preferred solution of the present invention, the excess sludge nitrogen and phosphorus separation unit is further provided with a first water quality meter for detecting temperature, pH, COD, ORP and total phosphorus.

[0009] As a preferred solution of the present invention, the nitrification unit is provided with a second water quality meter for detecting temperature, DO, pH and ammonia nitrogen.

[0010] As a preferred embodiment of the present invention, the anaerobic ammonium oxidation unit is provided with a third water quality meter for detecting temperature, pH, COD, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.

[0011] As a preferred solution of the present invention, the deep treatment unit is provided with a fourth water quality meter for detecting COD, total nitrogen and total phosphorus.

[0012] As a preferred solution of the present invention, the first water outlet pipe is connected to the external farmland, the second water outlet pipe is connected to the deep processing unit, and the third water outlet pipe is connected to the external river.

[0013] As a preferred embodiment of the present invention, the excess sludge is taken from the centrifugally dewatered sludge in the secondary sedimentation tank of a municipal sewage treatment plant that undergoes nitrogen and phosphorus removal through a biological treatment process.

[0014] The present invention also provides a method for treating excess sludge using the above-mentioned treatment device, the method comprising the following steps:

[0015] a) Anaerobic phosphorus release: The excess sludge is subjected to anaerobically released phosphorus in the excess sludge nitrogen-phosphorus separation unit. The temperature is controlled at 10-30°C, the pH is controlled at 7.00-8.00, the COD / TP is controlled at 10-15, the COD / TP is regulated by adding humic acid, and the ORP is controlled at -100 to -200 mV. When the phosphorus release rate first reaches an inflection point, acid / base adjustment is performed according to the pH of the local farmland soil. If the local farmland is acidic, acid adjustment is performed, and pH control is performed. The pH is controlled at 3.50-4.00; if the local farmland is alkaline soil, alkali adjustment is performed to control the pH at 10.00-10.50; when the phosphorus release rate reaches an inflection point for the second time, correction adjustment is made based on the acidity and alkalinity of the local farmland soil to adjust the pH to a pH close to that of the local farmland soil; when the phosphorus release rate reaches an inflection point for the third time, the anaerobic phosphorus release process ends; after settling for 20-30 minutes, the supernatant is transported to the farmland through the first outlet pipe and can be used as a phosphate fertilizer after the phosphorus concentration is adjusted;

[0016] The above-mentioned anaerobic phosphorus release process experiences three inflection points: (1) The phosphorus in the residual sludge includes organic phosphorus and inorganic phosphorus, among which inorganic phosphorus is more suitable for plant absorption and utilization. At the first inflection point, the sludge biological anaerobic process can effectively convert the organic phosphorus in the sludge into soluble inorganic phosphorus such as phosphate. (2) After the residual sludge is anaerobic treated, there is a significant release of phosphorus, but some phosphorus in the sludge is still not completely released, and a large amount of phosphorus is stored in the EPS component. Therefore, in order to achieve the best phosphorus release effect, it is necessary to further enhance the anaerobic phosphorus release effect through acid / alkali adjustment. Among them, the increase in phosphorus under acid pre-conditioning at the second inflection point is mainly attributed to the dissolution and release of inorganic phosphorus in the sludge component, while the increase in phosphorus in the alkaline pre-conditioning solution at the second inflection point is attributed to the release of inorganic phosphorus, the conversion of organic phosphorus into inorganic phosphorus and the disintegration of sludge; acid / alkali adjustment also promotes the loosening of sludge structure, which helps to shorten the subsequent sludge fermentation time. (3) The correction adjustment after acid / alkaline adjustment not only helps maintain a healthy farmland soil environment, but also facilitates the chemical release of phosphorus from the excess sludge. At the third inflection point, the phosphorus concentration of the solution in the excess sludge nitrogen-phosphorus separation unit reaches its maximum value and its pH value is suitable for farmland application.

[0017] b) Sludge fermentation: The dephosphorized excess sludge is fermented in the excess sludge nitrogen-phosphorus separation unit, with the temperature controlled at 25-30°C, the pH controlled at 10.00-11.00, and the sludge retention time controlled at 5-8 days. After the sludge fermentation is completed, the sludge fermentation product is respectively delivered to the nitrification unit and the anaerobic ammonium oxidation unit through the first electric valve and the infusion pump at a ratio of 1:1-1.32:1;

[0018] Sludge fermentation can achieve sludge reduction and stabilization, especially the alkaline anaerobic fermentation of excess sludge. By controlling the sludge age to maintain the sludge fermentation in the hydrolysis and acidification stage, a large amount of short-chain fatty acids (SCFAs) that are the dominant carbon source and are beneficial to the biological utilization of anaerobic ammonia-oxidizing bacteria can be accumulated. At the same time, by separating nitrogen and phosphorus and using phosphorus for agricultural purposes before sludge fermentation, it not only helps to simultaneously solve the current increasing phosphorus demand and excess sludge treatment volume, but also reduces the phosphorus load of subsequent treatment units, which is beneficial to the long-term stable operation of the device.

[0019] c) Aerobic nitrification: The nitrification unit uses an aeration device to achieve mud-water mixing, with DO controlled at 2.0-3.0 mg / L, pH controlled at 7.50-8.00, and temperature controlled at 25-30°C. The aerobic nitrification process ends when the ammonia nitrogen concentration reaches 0 mg / L, and the tail water is sent to the anaerobic ammonium oxidation unit through the second electric valve;

[0020] Nitrifying bacteria include two groups of bacteria: ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). The former can convert ammonia nitrogen (NH4 + -N) is oxidized to nitrite nitrogen (NO2 - -N), which can further convert nitrite nitrogen (NO2 - -N) is oxidized to nitrate nitrogen (NO3 - -N). AOB converts NH4 + -N oxidizes NO2 - The process of -N is called partial nitrification (PN) reaction, and AOB and NOB jointly convert NH4 + -N is oxidized to NO3 - The process of -N is called nitrification. Since AOB and NOB usually appear together in nitrifying sludge, nitrification is much easier to achieve and control than PN reaction.

[0021] d) Anaerobic denitrification: The anaerobic ammonium oxidation unit uses a second agitator to mix mud and water, with the temperature controlled at 30-37°C, the pH at 7.27-7.29, and the carbon-nitrogen ratio at 0.43-1.67. The anaerobic ammonium oxidation process ends when the sum of the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen reaches 2.0 mg / L. The tail water is sent to the deep treatment unit through the second outlet pipe.

[0022] Anaerobic ammonium oxidation (Anammox) bacteria produce NH4 + -N and NO3 -The biological reaction of simultaneous nitrate removal is a short-range nitrate reduction to ammonium (Partial Dissimilatory Nitrate Reduction to Ammonium, PDNRA) coupled with anaerobic ammonium oxidation (PDNRA-Anammox) reaction. The process consists of two steps: anaerobic ammonium oxidizing bacteria first use organic carbon sources as reducing agents to reduce NO3 in the raw water through PDNRA reaction. - -N is converted into the intermediate product NO2 - -N, and then NH4 in the raw water is converted into + -N and generated NO2 - -N is converted into nitrogen gas (N2). Therefore, anaerobic ammonium oxidizing bacteria can be coupled with nitrifying bacteria to achieve nitrogen removal through a more efficient, convenient and stable Nitrification-PDNRA-Anammox process, thereby avoiding the complex work of washing NOB and enriching AOB required by the PN-Anammox process.

[0023] e) Advanced treatment: The advanced treatment unit is filled with modified activated carbon made from SDS and DTAB. The hydraulic retention time (HRT) is controlled at 2-4 hours, the filter material particle size is controlled at 20 mesh × 50 mesh, and the effluent is discharged to the surrounding river through the third outlet pipe for natural circulation again.

[0024] As a preferred embodiment of the present invention, in step e), the preparation method of the SDS and DTAB composite modified activated carbon is as follows: the SDS and DTAB composite solution is prepared according to 20 mL of SDS and DTAB composite solution / g of activated carbon, the initial SDS concentration is 0.05-0.10 mol / L, the initial DTAB concentration is 0.01-0.02 mol / L, the pH is controlled at 4.50-5.50, the modification temperature is controlled at 20-30°C, and the modification time is controlled at 4-5 h.

[0025] Compared with unmodified activated carbon, the surface of activated carbon modified by SDS and DTAB becomes rougher and more uneven, its BET specific surface area, external surface area and total pore volume are significantly increased, and the nitrogen and phosphorus adsorption effect is significantly enhanced; at the same time, its acidic oxygen-containing functional group content is also richer, and the heavy metal adsorption effect is significantly enhanced.

[0026] Compared with the existing technology, the present invention has the following beneficial effects: the device and method of the present invention have distinct ecological and environmental protection and economic and effective characteristics, can achieve sludge reduction, stabilization, harmlessness and resource utilization, and by performing nitrogen and phosphorus separation and agricultural phosphorus use before sludge fermentation, it not only helps to simultaneously solve the current increasing phosphorus demand and residual sludge treatment volume, but also can reduce the phosphorus load of subsequent treatment units, which is beneficial to the long-term stable operation of the device and has practical significance and engineering value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the present invention.

[0028] In the figure, 1. Residual sludge nitrogen-phosphorus separation unit; 1-1. First agitator; 1-2. First water quality meter; 1-3. First outlet pipe; 2. Nitrification unit; 2-1. Second water quality meter; 2-2. Aeration device; 3. Anaerobic ammonia oxidation unit; 3-1. Second agitator; 3-2. Third water quality meter; 3-3. Second outlet pipe; 4. Deep treatment unit; 4-1. Fourth water quality meter; 4-2. Third outlet pipe; 5. First electric valve; 6. Second electric valve; 7. Infusion pump; 8. Farmland; 9. River. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] See also Figure 1 The present invention first provides a device for treating excess sludge, including an excess sludge nitrogen and phosphorus separation unit 1, a nitrification unit 2, an anaerobic ammonium oxidation unit 3 and a deep treatment unit 4.

[0031] The residual sludge nitrogen-phosphorus separation unit 1 is equipped with a first agitator 1-1, a first water quality meter 1-2 and a first outlet pipe 1-3. The residual sludge is taken from the centrifugal dewatered sludge in the secondary sedimentation tank of the urban sewage treatment plant that undergoes denitrification and dephosphorization through a biological treatment process. The parameters of the first water quality meter 1-2 include temperature, pH, COD, ORP and total phosphorus.

[0032] The first water outlet pipe 1 - 3 is connected to the farmland 8 .

[0033] The nitrification unit 2 is inoculated with nitrification sludge, and is equipped with a second water quality meter 2-1 and an aeration device 2-2. The parameters of the second water quality meter 2-1 include temperature, DO, pH and ammonia nitrogen.

[0034] Anaerobic ammonium oxidation unit 3 is inoculated with anaerobic ammonium oxidation biofilm sludge or granular sludge, and is equipped with a second agitator 3-1, a third water quality meter 3-2 and a second outlet pipe 3-3. The parameters of the third water quality meter 3-2 include temperature, pH, COD, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.

[0035] The second water outlet pipe 3 - 3 is connected to the deep processing unit 4 .

[0036] Advanced treatment unit 4 is filled with activated carbon modified with a mixture of SDS and DTAB. A fourth water quality meter 4-1 and a third outlet pipe 4-2 are installed. The parameters of the fourth water quality meter 4-1 include COD, total nitrogen, and total phosphorus. The SDS-DTAB-modified activated carbon is prepared by preparing a solution of SDS and DTAB at a ratio of 20 mL of the solution per gram of activated carbon, with an initial SDS concentration of 0.05-0.10 mol / L and an initial DTAB concentration of 0.01-0.02 mol / L. The pH is controlled between 4.50 and 5.50, the modification temperature is controlled between 20-30°C, and the modification time is controlled between 4 and 5 hours. Compared with unmodified activated carbon, the surface of activated carbon modified by SDS and DTAB becomes rougher and more uneven, its BET specific surface area, external surface area and total pore volume are significantly increased, and the nitrogen and phosphorus adsorption effect is significantly enhanced; at the same time, its acidic oxygen-containing functional group content is also richer, and the heavy metal adsorption effect is significantly enhanced.

[0037] The third water outlet pipe 4 - 2 is connected to the river 9 .

[0038] A first electric valve 5 is installed between the excess sludge nitrogen and phosphorus separation unit 1 and the nitrification unit 2 , a second electric valve 6 is installed between the nitrification unit 2 and the anaerobic ammonium oxidation unit 3 , and an infusion pump 7 is installed between the excess sludge nitrogen and phosphorus separation unit 1 and the anaerobic ammonium oxidation unit 3 .

[0039] Example

[0040] This embodiment discloses a method for treating excess sludge using the above-mentioned treatment device, comprising the following steps:

[0041] (a) Anaerobic phosphorus release:

[0042] Phosphorus in excess sludge consists of both organic and inorganic forms, with inorganic phosphorus being more readily absorbed and utilized by plants. The anaerobic sludge bioprocess effectively converts organic phosphorus into soluble inorganic forms such as phosphate. The excess sludge undergoes anaerobically released phosphorus in the excess sludge nitrogen-phosphorus separation unit, with the temperature controlled at 10-30°C, pH at 7.00-8.00, COD / TP ratio at 10-15, and ORP at -100--200 mV. A COD / TP ratio of 10-15 results in a relatively low organic matter content, further consuming organic matter in the sludge during phosphorus release and reducing the organic matter load in subsequent treatment units. The COD / TP ratio is controlled by adding humic acid. Humic acid, a quinone compound, not only assists microbial oxidation and degradation of organic compounds by providing final electrons, but also reduces the reduced quinone groups, acting as redox reaction mediators for various pollutants and providing electrons for bacterial growth and reproduction. Therefore, combining excess sludge with humic acid can form a new humic acid / microbial phosphorus removal system, thereby achieving humic acid respiration in excess sludge. Furthermore, humic acid is the most active and effective component of soil organic matter. It has beneficial effects on phosphate fertilizer efficiency, such as inhibiting the fixation of water-soluble phosphorus in the soil, increasing phosphorus mobility within the soil, and promoting phosphorus uptake by crop roots, without the risk of soil pollution.

[0043] When the phosphorus release rate first reaches an inflection point, significant phosphorus release occurs after anaerobic treatment of the excess sludge. However, some phosphorus remains incompletely released, and a significant amount is stored in the EPS component. Therefore, to achieve optimal phosphorus release, further acid / base conditioning is required to enhance anaerobic phosphorus release. Acid / base conditioning is performed based on the pH of the local farmland soil. If the local farmland is acidic, acid conditioning is performed to control the pH between 3.50 and 4.00; if the local farmland is alkaline, alkaline conditioning is performed to control the pH between 10.00 and 10.50. Acid / base conditioning effectively enhances anaerobic phosphorus release from excess sludge. The increase in phosphorus during acid preconditioning is primarily attributed to the dissolution and release of inorganic phosphorus from sludge components, while the increase in phosphorus in the alkaline preconditioning solution is attributed to the release of inorganic phosphorus, the conversion of organic phosphorus to inorganic phosphorus, and the breakdown of the sludge. Acid / base conditioning also promotes the loosening of the sludge structure, helping to shorten subsequent sludge fermentation time.

[0044] When the phosphorus release rate reaches its second inflection point, the pH is adjusted based on the acidity and alkalinity of the local farmland soil to a pH close to that of the local farmland soil. This adjustment after acid / alkalinity adjustment not only helps maintain a healthy farmland soil environment but also facilitates the chemical release of phosphorus from the excess sludge.

[0045] When the phosphorus release rate reaches an inflection point for the third time, the anaerobic phosphorus release process ends. After settling for 20-30 minutes, the supernatant is transported to farmland through the first outlet pipe and can be used as phosphorus fertilizer after adjusting the phosphorus concentration.

[0046] (b) Sludge fermentation:

[0047] The dephosphorized excess sludge is fermented in the excess sludge nitrogen-phosphorus separation unit, with the temperature controlled at 25-30°C, the pH at 10.00-11.00, and the sludge retention time (SRT) at 5-8 days. After fermentation, the fermented sludge is delivered to the nitrification unit and the anaerobic ammonium oxidation unit, respectively, via a first electric valve and an infusion pump at a ratio of 1:1-1.32:1. As a preferred option, the excess sludge nitrogen-phosphorus separation unit can also be equipped with a excess sludge storage tank and a sludge fermentation product storage tank to ensure continuous operation.

[0048] Sludge fermentation can achieve sludge reduction and stabilization, especially the alkaline anaerobic fermentation of excess sludge. By controlling the sludge age to maintain the sludge fermentation in the hydrolysis and acidification stage, a large amount of short-chain fatty acids, which are the dominant carbon source and are beneficial to the biological utilization of anaerobic ammonia-oxidizing bacteria, can be accumulated. At the same time, by separating nitrogen and phosphorus and using phosphorus for agricultural purposes before sludge fermentation, it not only helps to simultaneously solve the current increasing phosphorus demand and excess sludge treatment volume, but also reduces the phosphorus load of subsequent treatment units, which is beneficial to the long-term stable operation of the device.

[0049] (c) Aerobic nitrification:

[0050] The nitrification unit uses aeration to mix mud and water, controlling the DO at 2.0-3.0 mg / L, the pH at 7.50-8.00, and the temperature at 25-30°C. The aerobic nitrification process ends when the ammonia nitrogen concentration reaches 0 mg / L. The tailwater is then sent to the anaerobic ammonium oxidation unit via a second electric valve.

[0051] Nitrifying bacteria include AOB and NOB. The former can convert NH4 + -N is oxidized to NO2 - -N, which can further convert NO2 - -N is oxidized to NO3 - -N. AOB converts NH4 + -N oxidizes NO2 - The process of -N is called PN reaction, and AOB and NOB jointly convert NH4 + -N is oxidized to NO3 - The process of -N is called Nitrification reaction. Since AOB and NOB usually appear together in nitrifying sludge, Nitrification reaction is much easier to achieve and control than PN reaction.

[0052] (d) Anaerobic denitrification:

[0053] The anaerobic ammonium oxidation (ANAMMOX) unit uses a second agitator to mix the sludge and water, controlling the temperature at 30-37°C, the pH at 7.27-7.29, and the carbon-nitrogen ratio at 0.43-1.67. The ANAMMOX process ends when the combined concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen reach 2.0 mg / L. The tailwater is then sent to the advanced treatment unit through a second outlet pipe.

[0054] Anammox bacteria to produce NH4 + -N and NO3 - The biological reaction for simultaneous removal of -N is the PDNRA-Anammox reaction, which includes two steps: Anammox bacteria first use organic carbon sources as reducing agents to reduce NO3 in the raw water through the PDNRA reaction. - -N is converted into the intermediate product NO2 - -N, and then NH4 in the raw water is converted into + -N and generated NO2 - -N is converted into N2. Therefore, Anammox bacteria can be coupled with nitrifying bacteria to achieve nitrogen removal through a more efficient, stable and convenient Nitrification-PDNRA-Anammox process, thereby avoiding the complex work of washing NOB and enriching AOB required by the PN-Anammox process.

[0055] (e) Deep processing

[0056] The hydraulic retention time HRT in the deep treatment unit is controlled at 2-4h, the filter material particle size is controlled at 20 mesh × 50 mesh, and the effluent is discharged to the surrounding river through the third outlet pipe for natural circulation again.

[0057] After the treatment method of the present invention, the phosphorus recovery data of the excess sludge nitrogen-phosphorus separation unit and the denitrification data of the nitrification-anaerobic ammonium oxidation unit are as follows:

[0058] Phosphorus recovery efficiency: The total phosphorus content of the residual sludge is about 53.75 mg P / g VSS. After the anaerobic phosphorus release at three inflection points in the present invention, the total phosphorus content of the sludge drops to about 17.30 mg P / g VSS, and the proportion of bioavailable phosphorus in the anaerobic phosphorus release liquid phase of the residual sludge is as high as more than 95%, and the phosphorus recovery rate of the residual sludge can reach 65%.

[0059] Denitrification benefit: Nitrate nitrogen is provided to the anaerobic ammonium oxidation unit through the nitrification unit, and the concentrations of ammonia nitrogen and nitrate nitrogen in the influent of the anaerobic ammonium oxidation unit are controlled at 69.62±1.45 and 88.88±0.61 mg / L, respectively. After the PDNRA-Anammox reaction of anaerobic ammonium oxidizing bacteria, the total nitrogen concentration in the effluent is lower than 2.0 mg / L, which can meet the Class V standard for agricultural water use areas in the surface water environmental quality standard, greatly increasing the service life of the subsequent deep treatment units.

[0060] It can be seen that the present invention performs nitrogen and phosphorus separation and phosphorus recovery before sludge fermentation, which not only helps to simultaneously solve the current increasing phosphorus demand and excess sludge treatment volume, but also reduces the phosphorus load of subsequent treatment units and enhances the denitrification efficiency of the nitrification-anaerobic ammonium oxidation unit, which is beneficial to the long-term stable operation of the device, and brings huge economic benefits while achieving huge environmental benefits.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for treating excess sludge, characterized in that: The processing method comprises the following steps: a) Anaerobic phosphorus release: The excess sludge is subjected to anaerobically released phosphorus in the excess sludge nitrogen-phosphorus separation unit. The temperature is controlled at 10-30°C, the pH is controlled at 7.00-8.00, the COD / TP is controlled at 10-15, the COD / TP is regulated by adding humic acid, and the ORP is controlled at -100 to -200 mV. When the phosphorus release rate first reaches an inflection point, acid / base adjustment is performed according to the pH of the local farmland soil. If the local farmland is acidic, acid adjustment is performed, and pH control is performed. The pH is controlled at 3.50-4.00; if the local farmland is alkaline soil, alkali adjustment is performed to control the pH at 10.00-10.50; when the phosphorus release rate reaches an inflection point for the second time, correction adjustment is made based on the acidity and alkalinity of the local farmland soil to adjust the pH to a pH close to that of the local farmland soil; when the phosphorus release rate reaches an inflection point for the third time, the anaerobic phosphorus release process ends; after settling for 20-30 minutes, the supernatant is transported to the farmland through the first outlet pipe and can be used as a phosphate fertilizer after the phosphorus concentration is adjusted; b) Sludge fermentation: The dephosphorized excess sludge is fermented in the excess sludge nitrogen-phosphorus separation unit, with the temperature controlled at 25-30°C, the pH controlled at 10.00-11.00, and the sludge retention time controlled at 5-8 days. After the sludge fermentation is completed, the sludge fermentation product is respectively delivered to the nitrification unit and the anaerobic ammonium oxidation unit through the first electric valve and the infusion pump at a ratio of 1:1-1.32:1; c) Aerobic nitrification: The nitrification unit uses an aeration device to achieve mud-water mixing, with DO controlled at 2.0-3.0 mg / L, pH controlled at 7.50-8.00, and temperature controlled at 25-30°C. The aerobic nitrification process ends when the ammonia nitrogen concentration reaches 0 mg / L, and the tail water is sent to the anaerobic ammonium oxidation unit through the second electric valve; d) Anaerobic denitrification: The anaerobic ammonium oxidation unit uses a second agitator to mix mud and water, with the temperature controlled at 30-37°C, the pH at 7.27-7.29, and the carbon-nitrogen ratio at 0.43-1.

67. The anaerobic ammonium oxidation process ends when the sum of the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen reaches 2.0 mg / L. The tail water is sent to the deep treatment unit through the second outlet pipe. e) Advanced treatment: The advanced treatment unit is filled with modified activated carbon made from SDS and DTAB. The hydraulic retention time (HRT) is controlled at 2-4 hours, the filter material particle size is controlled at 20 mesh × 50 mesh, and the effluent is discharged to the surrounding river through the third outlet pipe for natural circulation again.

2. The method for treating excess sludge according to claim 1, wherein: In step e), the preparation method of the SDS and DTAB composite modified activated carbon is as follows: SDS and DTAB composite solution is prepared according to 20 mL of SDS and DTAB composite solution / g of activated carbon, the initial SDS concentration is 0.05-0.10 mol / L, the initial DTAB concentration is 0.01-0.02 mol / L, the pH is controlled at 4.50-5.50, the modification temperature is controlled at 20-30°C, and the modification time is controlled at 4-5h.

3. The method for treating excess sludge according to claim 1 or 2, characterized in that: The treatment device adopted in the treatment method includes a residual sludge nitrogen and phosphorus separation unit, a nitrification unit, an anaerobic ammonium oxidation unit and a deep treatment unit connected in sequence; wherein, the residual sludge nitrogen and phosphorus separation unit is provided with a first agitator and a first outlet pipe, the bottom of the nitrification unit is provided with an aeration device, the anaerobic ammonium oxidation unit is provided with a second agitator and a second outlet pipe, and the deep treatment unit is provided with a third outlet pipe; the residual sludge nitrogen and phosphorus separation unit is also connected to the anaerobic ammonium oxidation unit, a first electric valve is installed between the residual sludge nitrogen and phosphorus separation unit and the nitrification unit, and a second electric valve is installed between the nitrification unit and the anaerobic ammonium oxidation unit.

4. The method for treating excess sludge according to claim 3, characterized in that: The excess sludge nitrogen and phosphorus separation unit is also provided with a first water quality meter for detecting temperature, pH, COD, ORP and total phosphorus.

5. The method for treating excess sludge according to claim 3, characterized in that: The nitrification unit is provided with a second water quality meter for detecting temperature, DO, pH and ammonia nitrogen.

6. The method for treating excess sludge according to claim 3, characterized in that: The anaerobic ammonium oxidation unit is provided with a third water quality meter for detecting temperature, pH, COD, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.

7. The method for treating excess sludge according to claim 3, characterized in that: The deep treatment unit is provided with a fourth water quality meter for detecting COD, total nitrogen and total phosphorus.

8. The method for treating excess sludge according to claim 3, characterized in that: The first water outlet pipe is connected to the external farmland, the second water outlet pipe is connected to the deep processing unit, and the third water outlet pipe is connected to the external river.

9. The method for treating excess sludge according to claim 3, characterized in that: The residual sludge is taken from the centrifugal dewatered sludge in the secondary sedimentation tank of the municipal sewage treatment plant where nitrogen and phosphorus are removed through biological treatment process.

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