A sewage treatment method based on PN / A coupled biochar SPD process

Abstract

The present invention discloses a sewage treatment method based on a PN / A coupled biochar SPD process. After the sewage enters the front-end SPD fixed bed through the front-end inlet / outlet channel, the organic matter in the sewage is removed by the adsorption effect of the biochar bricks inside the sewage; then, after entering the PN / A reactor through the front-end upflow / downflow trough, the sewage is denitrified by the nitrite sludge and fully autotrophic denitrification granular sludge inoculated therein; then, after entering the rear-end SPD fixed bed through the rear-end upflow / downflow trough, the denitrifying bacteria use the organic matter adsorbed by the biochar bricks inside as a carbon source to remove residual nitrates in the sewage. Finally, the effluent is discharged through the rear-end inlet / outlet channel. The present invention determines whether the biochar has reached adsorption saturation by real-time detection of the DO concentration and nitrate nitrogen concentration in the PN / A reactor, and dynamically adjusts the inlet and outlet directions to achieve the purpose of repeatedly utilizing the organic matter adsorbed by the biochar, effectively solving the problems of high carbon source cost for deep denitrification and increased amount of residual sludge.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage denitrification treatment, and specifically relates to a sewage treatment method based on a PN / A (partial nitrification-anaerobic ammonium oxidation) coupled biochar SPD (solid phase denitrification) process. Background Art

[0002] With the rapid development of today's social economy and the continuous improvement of people's living standards, the problem of water pollution has received more and more attention.

[0003] Partial nitrification-anaerobic ammonium oxidation (PN / A) is a wastewater denitrification process that first oxidizes ammonia nitrogen to nitrite nitrogen, then uses anaerobic ammonium-oxidizing bacteria to convert nitrite nitrogen and ammonia nitrogen into nitrogen gas. Because it requires no aeration or external carbon source, it can save 60% of energy consumption and 100% of carbon source. However, the PN / A process also has problems such as sensitivity to high concentrations of organic matter, substandard nitrate nitrogen, and residual nitrate nitrogen. Coupled heterotrophic denitrification is often used for deep denitrification. This also creates new challenges such as increased carbon source input costs and increased excess sludge volume.

[0004] Currently, scholars at home and abroad are eager to find the most cost-effective and efficient denitrification process to meet the increasingly stringent water quality standards for sewage treatment plants. Therefore, it is urgent to develop new denitrification processes and study the mechanisms of various denitrification processes. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides a sewage treatment method based on the PN / A (partial nitrification-anaerobic ammonium oxidation) coupled biochar SPD (solid phase denitrification) process to solve the problems of high cost of deep denitrification carbon sources and increased amount of residual sludge, ensure the stability and biological activity of granular sludge, and improve the effluent quality.

[0006] In order to solve the above technical problems and achieve the above technical effects, the present invention is implemented through the following technical solutions:

[0007] A sewage treatment method based on PN / A coupled biochar SPD, the main steps of which include:

[0008] The sewage enters the front-end SPD fixed bed from the front-end inlet / outlet channel. The front-end SPD fixed bed removes organic matter from the sewage by the adsorption effect of the biochar bricks inside it.

[0009] The wastewater after removing organic matter enters the front-end upflow / downflow trough through the front-end SPD fixed bed. The wastewater enters the PN / A reactor after upflow and downflow in the front-end upflow / downflow trough.

[0010] The PN / A reactor uses the nitrite sludge and fully autotrophic denitrification granular sludge inoculated inside it to denitrify the sewage, and the DO concentration and nitrate nitrogen concentration in the PN / A reactor are detected in real time by a DO detector and a nitrate nitrogen detector;

[0011] The denitrified wastewater enters the rear-end upflow / downflow trough from the PN / A reactor, and the effluent enters the rear-end SPD fixed bed after upflow and downflow in the rear-end upflow / downflow trough;

[0012] Denitrifying bacteria use the organic matter adsorbed by the biochar bricks inside the rear-end SPD fixed bed as a carbon source to remove the residual nitrate in the sewage. The effluent after deep denitrification is finally discharged from the rear-end inlet / outlet channel.

[0013] Furthermore, before sewage treatment, nitrite sludge and fully autotrophic denitrification granular sludge are inoculated in a certain proportion in the PN / A reactor to maintain the sludge concentration in the PN / A reactor within a certain range; and a plurality of biochar bricks are stacked in the filler area inside the front-end SPD fixed bed and the rear-end SPD fixed bed respectively.

[0014] Furthermore, the particle sizes of the nitrite sludge and the fully autotrophic denitrification granular sludge are both 0.5-3 mm, and the inoculation volume ratio of the nitrite sludge to the fully autotrophic denitrification granular sludge is 1:1, so that the sludge concentration MLSS of the PN / A reactor is maintained at 3000-9000 mg / L.

[0015] Furthermore, the biochar brick is a cubic biochar brick with honeycomb-shaped holes inside, the ratio of its length, width and height is 1:1:1, the pore radius is 50mm, and the specific surface area is 80-120m 2 / g, porosity is 50%-70%, flow rate in the pore is 0.8-1.2m / s, and organic matter removal rate is 75-90%.

[0016] Furthermore, when the front-end SPD fixed bed or the rear-end SPD fixed bed removes organic matter from sewage, the HRT is 1-4h and the COD load is 0.25-2kg·m -3 ·d -1 , COD removal rate is 75-90%.

[0017] Furthermore, when the PN / A reactor is used to denitrify wastewater, the HRT is 0.5-3h and the NLR is 0.5-4 kg·m -3 ·d -1 The ammonia nitrogen removal rate is 80%-95%.

[0018] Furthermore, when the PN / A reactor is denitrifying the sewage, aeration is ensured by the air compressor and the aeration head to ensure that the sewage and granular sludge in the PN / A reactor are completely mixed, and the DO concentration in the PN / A reactor is monitored in real time by a DO detector to maintain a DO concentration of 2 mg / L.

[0019] Furthermore, when the rear-end SPD fixed bed or the front-end SPD fixed bed removes nitrate from sewage, the HRT is 0.5-3h.

[0020] Furthermore, during the denitrification process of the sewage in the PN / A reactor, the DO detector and the nitrate nitrogen detector will feed back the monitored DO concentration and nitrate nitrogen concentration data to the controller in real time. The controller determines the organic matter adsorption state of the biochar bricks in the front-end SPD fixed bed based on the sent back DO concentration and nitrate nitrogen concentration data.

[0021] Furthermore, when the controller detects that the biochar bricks in the front-end SPD fixed bed are saturated with adsorption, the controller changes the inlet and outlet direction of the sewage, and the sewage enters the rear-end SPD fixed bed through the rear-end inlet / outlet channel; at this time, the rear-end SPD fixed bed is responsible for utilizing the adsorption effect of the cubic biochar bricks inside it to remove organic matter in the sewage, while the front-end SPD fixed bed is responsible for utilizing the organic matter adsorbed by the cubic biochar bricks inside it as a carbon source for denitrifying bacteria to remove residual nitrates in the sewage, thereby achieving resource utilization of organic matter in the sewage while completing deep denitrification.

[0022] The beneficial effects of the present invention are:

[0023] 1. A single short-range nitrification-anaerobic ammonium oxidation (PN / A) process can theoretically remove up to 89% of ammonia nitrogen, but 10%-20% of the nitrogen is converted into nitrate nitrogen and cannot be removed. A single solid phase denitrification (SPD) has a good removal effect on low-concentration nitrate, but a poor removal effect on high-concentration nitrate. Therefore, the sewage treatment method of the present invention couples the two to perform deep denitrification treatment on sewage, reduce the concentration of nitrate nitrogen in the effluent, and improve the effluent water quality.

[0024] 2. The wastewater treatment method of the present invention uses biochar, made from sludge, as a filler in the SPD. Compared to traditional dissolved organic carbon sources, biochar offers low cost and a wide range of sources. Its excellent adsorption properties absorb organic matter from wastewater and store it as a usable carbon source. This not only maintains the stability of the PN / A granular sludge but also recycles the organic matter into a resource, resulting in high economic benefits. Furthermore, it provides a growth medium for microorganisms, creating a more stable living environment for anaerobic ammonium oxidizing bacteria and denitrifying bacteria, thus offering broad development and application prospects.

[0025] 3. The entire system used in the sewage treatment method of the present invention has a symmetrical structure, with water both entering and exiting at both ends. Real-time detection is performed through a DO detector and a nitrate nitrogen monitor. When the biochar adsorption is saturated, the water inlet direction is automatically changed, effectively utilizing the organic matter adsorbed by the biochar as a carbon source, with a high degree of resource utilization.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the invention and to implement it according to the contents of the description, the following preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 1 is a process flow chart of the sewage treatment method of the present invention;

[0029] Figure 2 A front perspective view of an embodiment of a sewage treatment system for implementing the sewage treatment method of the present invention;

[0030] Figure 3 Schematic diagram of the biochar brick used in the invented sewage treatment method. Implementation Method

[0031] The following will be described in detail with reference to the accompanying drawings to better understand the purpose, features and advantages of the invention. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the invention, but are only intended to illustrate the essential spirit of the technical solution of the invention.

[0032] In the following description, for the purpose of illustrating the various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other cases, well-known devices, structures, and techniques associated with this application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0033] Unless the context requires otherwise, throughout the specification and claims, the word "comprise" and variations such as "include" and "have" should be construed in an open, inclusive sense, that is, should be interpreted to mean "including, but not limited to."

[0034] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0035] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0036] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] The present invention provides a sewage treatment method based on PN / A coupled biochar SPD, which needs to be implemented by relying on a sewage treatment system of the following embodiment.

[0038] See also Figure 2-3 As shown, a system for implementing a sewage treatment method based on a PN / A coupled biochar SPD process, the system includes a PN / A reactor 1, and a front-end SPD fixed bed 2a and a rear-end SPD fixed bed 2b located on the left and right sides of the PN / A reactor 1, respectively; the front-end SPD fixed bed 2a is connected to the PN / A reactor 1 via a front-end upflow / downflow trough 3a, and the rear-end SPD fixed bed 2b is connected to the PN / A reactor 1 via a rear-end upflow / downflow trough 3b; the internal structure of the front-end SPD fixed bed 2a is bilaterally symmetrical to the internal structure of the rear-end SPD fixed bed 2b, and the filling area 201 inside the front-end SPD fixed bed 2a and the rear-end SPD fixed bed 2b is composed of multiple biochar bricks; wherein the length, width and height ratio of the front-end SPD fixed bed 2a and the rear-end SPD fixed bed 2b are preferably 1:1:3, and the length, width and height ratio of the PN / A reactor 1 are preferably 1:1:3.

[0039] See also Figure 2As shown, the internal structures of the front-end SPD fixed bed 2a and the rear-end SPD fixed bed 2b are composed of an upper cavity, a middle cavity and a lower cavity, the upper cavity and the middle cavity are separated by an upper filter plate 202, and the middle cavity and the lower cavity are separated by a lower filter plate; a V-shaped groove 203 is provided in the upper cavity, and an inlet / outlet water channel 204 is provided on the outside of the upper cavity, and the inlet / outlet water channel 204 is connected to the V-shaped groove 203; a plurality of biochar bricks are provided in the middle cavity as the filling area; the lower cavity and the middle cavity are separated by a lower filter plate 205, and a bottom water channel 206 is provided in the lower cavity, and the bottom water channel 206 is connected to the front-end upflow / downflow trough 3a or the rear-end upflow / downflow trough 3b; wherein, the ratio of the length, width and height of the filling area is preferably 1:1:2.

[0040] See also Figure 2 As shown, the interior of the PN / A reactor 1 has a symmetrical structure, consisting of a sedimentation zone 101, a main reaction zone 102, and a recirculation zone 103. The recirculation zone 103 is located on the left and right sides of the main reaction zone 102 and is used to introduce or lead sewage into or out of the main reaction zone 102. The main reaction zone 102 is inoculated with nitrite sludge and fully autotrophic denitrification granular sludge for fully mixing with the sewage for denitrification. The sedimentation zone 101 is located at the bottom of the main reaction zone 102 and is used to receive the granular sludge settled after the reaction.

[0041] The PN / A reactor 1 is further equipped with an air compressor 4, an aeration head 5, a DO monitor 6, and a nitrate nitrogen monitor 7; the probes of the nitrate nitrogen monitor 7 and the DO monitor 6 are both inserted into the interior of the PN / A reactor 1, the aeration head is arranged inside the PN / A reactor 1, and the air compressor 4 provides an air source for the aeration head 5;

[0042] The nitrate nitrogen monitor 7, the DO monitor 6 and the air compressor 4 are all connected to the controller 8 by signal. The controller 8 is used to control the inlet and outlet directions of the sewage and the aeration time of the aeration head 5 according to the detection data of the nitrate nitrogen monitor 7 and the DO monitor 6.

[0043] See also Figure 2As shown, the structure of the front-end upflow / downflow trough 3a is bilaterally symmetrical with the structure of the rear-end upflow / downflow trough 3b, and both are composed of side-by-side outer troughs 301 and inner troughs 302. The outer trough 301 and the inner trough 302 are connected through an overflow port 303 at the top, and the outer trough 301 is connected to the front-end SPD fixed bed 2a or the rear-end SPD fixed bed 2b through the outer water hole 304 at the bottom, and the inner trough 302 is connected to the PN / A reactor 1 through the inner water hole 305 in the middle and lower part; one of the outer trough 301 and the inner trough 302 serves as an upflow area, and the other serves as a downflow area; wherein the length-to-width ratio of the outer water hole 304 and the inner water hole 305 is preferably 1:1.5.

[0044] See also Figure 3 As shown, the shape of the biochar brick is a cubic biochar brick with honeycomb holes inside, the ratio of its length, width and height is preferably 1:1:1, the pore radius is 50mm, the specific surface area is 80-120m2 / g, the porosity is 50%-70%, the pore flow rate is preferably 0.8-1.2m / s, and the organic matter removal rate is 75-90%; the preparation steps of the biochar brick are as follows:

[0045] Step 1) The municipal sludge is first conditioned and reshaped, and then dehydrated to form dehydrated cakes. The dehydrated cakes are then crushed into municipal sludge pellets by a crusher. The municipal sludge pellets are then fed into a drying furnace and dried at 120°C for 60 minutes. The municipal sludge pellets are then pyrolyzed in a muffle furnace at a pyrolysis temperature of 600°C, a nitrogen flow rate of 0.5L / min, and a heating rate of 10°C / min. The pyrolysis is carried out in an inert N2 atmosphere for 2-3 hours to produce sludge charcoal. Finally, the sludge charcoal is naturally cooled to room temperature.

[0046] The added agent is one or more of an inorganic coagulant, an organic coagulant, and an additive;

[0047] The moisture content of the dehydrated water cake after high-speed dehydration is ≤60%, and the particle size of the municipal sludge particles after the dehydrated water cake is crushed by a crusher is ≤50mm;

[0048] The drying furnace is an internal heating type drying furnace with a temperature range of 120°C and a residence time of 60 minutes;

[0049] Step 2) The cooled sludge carbon is washed with deionized water until the washing liquid is neutral, and then solid-liquid separation is performed. The resulting solid phase is dried to obtain the impurity-removed sludge carbon, which is then ground using a mechanical grinder and then sieved through a 0.6 mm mesh;

[0050] The purpose of adding deionized water is to remove excess inorganic salt impurity ions in the sludge carbon, and then the sludge carbon is preferably cleaned by combining ultrasound, heating and stirring. The ultrasound time is preferably 30-90 minutes, and stirring is performed; the heating temperature is preferably 40-80°C, and stirring is performed at the same time;

[0051] Step 3) The zeolite is washed with deionized water until the washing liquid is neutral, and then solid-liquid separation is performed. The resulting solid phase is dried to obtain the impurity-free zeolite, which is then ground using a mechanical grinder and then sieved through a 0.6 mm mesh;

[0052] Among them, when cleaning the zeolite, the purpose of adding deionized water is to remove impurities including carbonates and organic matter in the zeolite;

[0053] Step 4) grinding the nanosilica, the impurity-removed zeolite, and the impurity-removed sludge in a ball mill at 800 rpm for 20 minutes, adding the ground mixture to the suspension, and stirring on a magnetic stirrer for 3 hours, separating the sludge impregnated with nanosilica and zeolite, and drying at 80° C. to obtain the sludge raw material;

[0054] The particle size of nano-silicon dioxide is 5-50 nm, and the mass ratio of nano-silicon dioxide to impurity-removing sludge is 1:5;

[0055] The impurity-removing zeolite accounts for 2-4% of the total mass of the nano-silica modified sludge carbon material;

[0056] The suspension is prepared by adding one or both of montmorillonite or kaolin powders to deionized water and then ultrasonically treating the water with an ultrasonic generator. The mass of the montmorillonite and / or kaolin powders is 20% of the total mass of the nano-silica modified sludge carbon material.

[0057] If the mass of the ball-milled mixture of nano-silica, impurity-removed zeolite and impurity-removed sludge is 10 g, the suspension can be prepared by adding 2 g of montmorillonite or kaolin powder to 500 mL of deionized water and then ultrasonicating the mixture for 30 minutes using an ultrasonic generator;

[0058] Step 5) placing the clay-treated sludge carbon raw material in a quartz tube in a tube furnace, pyrolyzing it in an inert gas N2 atmosphere at a pyrolysis temperature of 600-800°C, and slowly pyrolyzing it for 1 hour to obtain a nano-silica-modified sludge carbon material; then grinding the obtained nano-silica-modified sludge carbon material in an electric-controlled mortar and pestle for 30 minutes, and then grinding it in a turbo grinder at 50 Hz and 1000 rpm for 3 hours to obtain a micron-sized nano-silica-modified sludge carbon material;

[0059] Wherein, the particle size of the micron-sized nano-silica modified sludge carbon material is preferably 1-5 μm;

[0060] Step 6) The prepared micron-sized nano-silica modified sludge charcoal material is made into a cubic biochar brick with honeycomb pores inside by 3D printing technology; the length, width and height ratio of the cubic biochar brick is preferably 1:1:1, the pore radius of the honeycomb pores inside the cubic biochar brick is 50mm, and the specific surface area is 80-120m 2 / g, the porosity is 50%-70%, the flow rate in the pore is preferably 0.8-1.2m / s, and the organic matter removal rate is 75-90%.

[0061] See also Figure 1-2 As shown, under the support of the physical structure of the above-mentioned sewage treatment system, the sewage treatment method based on PN / A coupled biochar SPD of the present invention includes the following steps:

[0062] System startup phase:

[0063] 1. Inoculate nitrite sludge and fully autotrophic denitrification granular sludge in a certain proportion in the PN / A reactor 1 to maintain the sludge concentration in the PN / A reactor 1 within a certain range;

[0064] The particle sizes of the nitrite sludge and the fully autotrophic denitrification granular sludge are both 0.5-3 mm, the inoculation volume ratio of the nitrite sludge to the fully autotrophic denitrification granular sludge is 1:1, and the sludge concentration MLSS of the PN / A reactor 1 is 3000-9000 mg / L;

[0065] Among them, in the granular sludge in the PN / A reactor 1, AOB, AMX and symbiotic heterotrophic bacteria are the core bacteria driving the autotrophic denitrification reaction, among which Planctomycetes to which AMX belongs account for 20%-40% of the total, followed by Proteobacteria (10%-30%), Bacteroidetes (10%-20%) and Chloroflexi (5%-15%);

[0066] 2. Use the DO detector and nitrate nitrogen detector to detect the DO (dissolved oxygen) concentration and nitrate nitrogen concentration in PN / A reactor 1 in real time;

[0067] 3. Multiple cubic biochar bricks with honeycomb-shaped holes are stacked in the filling area 201 inside the front SPD fixed bed 2a and the rear SPD fixed bed 2b respectively;

[0068] The dominant bacterial phyla in the front SPD fixed bed 2a and the rear SPD fixed bed 2b are Proteobacteria (20%-50%), Bacteroidetes (10%-30%), Firmicutes (5%-20%) and Patescibacteria (2%-10%), etc.

[0069] The length, width and height ratio of the cubic biochar brick is 1:1:1. The pore radius of the honeycomb pores inside the cubic biochar brick is 50 mm, the specific surface area is 80-120 m2 / g, the porosity is 50%-70%, the flow rate in the pores is preferably 0.8-1.2 m / s, and the organic matter removal rate is 75-90%.

[0070] Operation and control stage:

[0071] 1. Sewage enters the front-end SPD fixed bed 2a through the front-end inlet / outlet channel 204. The front-end SPD fixed bed 2a removes organic matter from the sewage through the adsorption effect of the cubic biochar bricks inside it;

[0072] During this process, the HRT (hydraulic retention time) of the front-end SPD fixed bed 2a is 1-4h, and the COD load is 0.25-2kg·m -3 ·d -1 , COD removal rate is 75-90%;

[0073] 2. After the organic matter is removed, the sewage enters the front-end upflow / downflow trough 3a through the front-end SPD fixed bed 2a. After upflow and downflow in the front-end upflow / downflow trough 3a, the sewage enters the PN / A reactor 1;

[0074] 3. The PN / A reactor 1 uses the nitrite sludge and fully autotrophic denitrification granular sludge inoculated inside it to denitrify the sewage, and the DO (dissolved oxygen) concentration and nitrate nitrogen concentration in the PN / A reactor 1 are detected in real time by the DO detector and the nitrate nitrogen detector;

[0075] During this process, the HRT (hydraulic retention time) of the PN / A reactor 1 was 0.5-3 h, and the NLR (nitrogen volumetric load) was 0.5-4 kg·m -3 ·d -1 , the ammonia nitrogen removal rate is 80%-95%; at the same time, during the aeration stage, the air compressor and aeration head are used to ensure that the sewage and granular sludge in the PN / A reactor 1 are completely mixed, and the DO (dissolved oxygen) concentration in the PN / A reactor 1 is monitored in real time by a DO detector and maintained at 2mg / L;

[0076] 4. The denitrified wastewater enters the rear-end upflow / downflow trough 3b from the PN / A reactor 1. The effluent enters the rear-end SPD fixed bed 2b after upflow and downflow in the rear-end upflow / downflow trough 3b.

[0077] 5. Denitrifying bacteria use the organic matter adsorbed by the cubic biochar bricks inside the rear-end SPD fixed bed 2b as a carbon source to remove the residual nitrate in the sewage. The effluent after deep denitrification is finally discharged through the rear-end inlet / outlet channel 204;

[0078] During this process, the HRT (hydraulic retention time) of the rear-end SPD fixed bed 2b is 0.5-3h;

[0079] 6. The controller determines whether the biochar bricks in the front-end SPD fixed bed 2a are saturated with organic matter adsorption based on the DO concentration and nitrate nitrogen concentration data monitored in real time by the DO detector and the nitrate nitrogen detector. When the biochar bricks in the front-end SPD fixed bed 2a are saturated with organic matter adsorption, the controller changes the inlet and outlet directions of the sewage, and the sewage enters the rear-end SPD fixed bed 2b through the rear-end inlet / outlet channel 204.

[0080] At this time, the rear-end SPD fixed bed 2b is responsible for removing organic matter from the sewage by utilizing the adsorption effect of the cubic biochar bricks inside it. The HRT (hydraulic retention time) is 1-4h and the COD load is 0.25-2kg·m -3 ·d -1 , COD removal rate is 75-90%; and the front-end SPD fixed bed 2a is responsible for using the organic matter adsorbed by the cubic biochar bricks inside it as a carbon source for denitrifying bacteria to remove residual nitrate in the sewage. The HRT (hydraulic retention time) is 0.5-3h. While completing deep denitrification, it realizes the resource utilization of organic matter in the sewage.

[0081] The sewage treatment method of the present invention is specifically described below through two embodiments. Example

[0082] Treated water: The average concentration of pollutants in industrial wastewater is COD 160mg / L, NH 4+ -N 200mg / L, pH 7.6-8.0, operating temperature 30-32℃. Experimental setup Figure 1-3 As shown, the place for realizing short-cut nitrification and anaerobic ammonium oxidation is a CSTR reactor with an effective volume of 500L, and the reactor for deep denitrification by denitrification is a fixed bed with an effective volume of 714L.

[0083] System startup: The PN / A reactor is inoculated with nitrite sludge and fully autotrophic denitrifying granular sludge. The granular sludge particle size is preferably 0.5-3mm. The granular sludge is inoculated at a volume ratio of 1:1 to keep the sludge concentration in the PN / A reactor at 3000-9000mg / L. The DO concentration and nitrate nitrogen concentration in the PN / A reactor are monitored in real time by a DO detector and a nitrate nitrogen detector. No sludge is added to the front-end SPD fixed bed or the rear-end SPD fixed bed. Instead, multiple cubic biochar bricks with honeycomb-shaped holes are placed in the filling area inside the front-end SPD fixed bed and the rear-end SPD fixed bed respectively. The selected biochar bricks are 30cm long, 30cm wide and 30cm high, with a pore radius of 50mm, a porosity of 70%, approximately 713 surface pores, and an organic matter removal rate of 75-90%.

[0084] Forward operation control: sewage flows from the front inlet / outlet channel into the V-shaped groove of the front SPD fixed bed. The V-shaped groove evenly distributes water to the filler area through the upper filter plate. The HRT is 2.9h and the COD load is 1.3 kg·m -3 ·d -1 The filler area uses the adsorption effect of biochar bricks to remove organic matter from the sewage. The water flow rate in the biochar bricks is 1m / s, and then flows into the bottom channel of the front SPD fixed bed through the lower filter plate; the sewage with organic matter removed then flows into the outer trough of the front upflow / downflow trough through the outer water hole. After rising in the outer trough, the water flows into the inner trough of the front upflow / downflow trough through the overflow port at the top. After descending in the inner trough, the water flows into the PN / A reactor through the inner water hole; in the PN / A reactor, the sewage first flows through the recirculation zone into the main reaction zone. The main reaction zone uses the nitrite sludge and fully autotrophic denitrification granular sludge inoculated inside it to denitrify the sewage. The hydraulic retention time is 2h, and the NLR is 2.4kg·m -3 ·d -1In the aeration stage, the air compressor and aeration head are used to ensure that the sewage and granular sludge in the reactor are completely mixed, and the DO concentration is maintained at 2 mg / L. The DO (dissolved oxygen) concentration and nitrate nitrogen concentration in the PN / A reactor are detected in real time by the DO detector and the nitrate nitrogen detector. The granular sludge after the reaction falls into the sedimentation area, and the sewage after denitrification flows into the inner tank of the rear-end upflow / downflow tank through the inner water hole on the other side. After the water flows up in the inner tank, it flows into the outer tank of the rear-end upflow / downflow tank through the overflow port at the top. After the flow is reduced in the outer trough, it flows into the bottom channel of the rear-end SPD fixed bed through the outer water hole; the setting of the rear-end SPD fixed bed is the same as that of the front-end SPD fixed bed, with an HRT of 2.9h. The sewage flows from the bottom channel into the filler area through the lower filter plate. The denitrifying bacteria use the organic matter adsorbed by the biochar bricks in the filler area as a carbon source to remove the residual nitrate in the sewage. The effluent after deep denitrification passes through the upper filter plate from the filler area into the V-shaped trough and is finally discharged from the rear-end inlet / outlet channel. The final effluent TN is less than 15mg / L, NO 3- <3 mg / L;

[0085] Reverse operation control: The controller will determine whether the biochar bricks in the front-end SPD fixed bed are in a saturated state of organic matter adsorption based on the DO concentration and nitrate nitrogen concentration data monitored in real time by the DO detector and the nitrate nitrogen detector. When the controller believes that the biochar bricks in the front-end SPD fixed bed are saturated with adsorption, it will change the inlet and outlet direction of the sewage, and the sewage will enter the rear-end SPD fixed bed from the rear-end inlet / outlet channel. At this time, the rear-end SPD fixed bed is responsible for removing organic matter from the sewage by utilizing the adsorption effect of the cubic biochar bricks inside it, while the front-end SPD fixed bed is responsible for utilizing the organic matter adsorbed by the cubic biochar bricks inside it as a carbon source for denitrifying bacteria to remove residual nitrate in the sewage. The entire treatment process is consistent with the treatment process of forward operation control. Example

[0086] Treated water: The average concentration of pollutants in industrial wastewater is COD 160mg / L, NH 4+ -N 60mg / L, pH 7.6-8.0, operating temperature 30-32℃. Figure 1-3 As shown, the place for realizing short-cut nitrification and anaerobic ammonium oxidation is a CSTR reactor with an effective volume of 500L, and the reactor for deep denitrification by denitrification is a fixed bed with an effective volume of 850L.

[0087] (1) System startup: The PN / A reactor is inoculated with nitrite sludge and fully autotrophic denitrification granular sludge. The particle size of the granular sludge is preferably 0.5-3 mm. The granular sludge is inoculated at a volume ratio of 1:1, so that the sludge concentration MLSS of the PN / A reactor is 3000-9000 mg / L. The DO concentration and nitrate nitrogen concentration in the PN / A reactor are detected in real time by the DO detector and the nitrate nitrogen detector. No inoculated sludge is added to the front-end SPD fixed bed and the rear-end SPD fixed bed. Instead, multiple cubic biochar bricks with honeycomb holes are stacked in the filling area inside the front-end SPD fixed bed and the rear-end SPD fixed bed respectively. The selected biochar bricks are 30 cm × 30 cm × 30 cm in length, width and height, with a pore radius of 50 mm, a porosity of 70%, a number of surface pores of about 713, and an organic matter removal rate of 75-90%.

[0088] (2) Forward operation control: Sewage flows from the front inlet / outlet channel into the V-shaped groove of the front SPD fixed bed. The V-shaped groove evenly distributes water to the filler area through the upper filter plate. The HRT is 1.7h and the COD load is 1.3 kg·m -3 ·d -1 The filler area uses the adsorption effect of biochar bricks to remove organic matter from the sewage. The water flow rate in the biochar bricks is 1m / s, and then flows into the bottom channel of the front SPD fixed bed through the lower filter plate; the sewage with organic matter removed then flows into the outer trough of the front upflow / downflow trough through the outer water hole. After rising in the outer trough, the water flows into the inner trough of the front upflow / downflow trough through the overflow port at the top. After descending in the inner trough, the water flows into the PN / A reactor through the inner water hole; in the PN / A reactor, the sewage first flows through the recirculation zone into the main reaction zone. The main reaction zone uses the nitrite sludge and fully autotrophic denitrification granular sludge inoculated inside it to denitrify the sewage. The hydraulic retention time is 1h, and the NLR is 1.44kg·m -3 ·d -1In the aeration stage, the air compressor and aeration head are used to ensure that the sewage and granular sludge in the reactor are completely mixed, and the DO concentration is maintained at 2 mg / L. The DO (dissolved oxygen) concentration and nitrate nitrogen concentration in the PN / A reactor are detected in real time by the DO detector and the nitrate nitrogen detector. The granular sludge after the reaction falls into the sedimentation area, and the sewage after denitrification flows into the inner tank of the rear-end upflow / downflow tank through the inner water hole on the other side. After the water flows up in the inner tank, it flows into the outer tank of the rear-end upflow / downflow tank through the overflow port at the top. After the flow is reduced in the outer trough, it flows into the bottom channel of the rear-end SPD fixed bed through the outer water hole; the setting of the rear-end SPD fixed bed is the same as that of the front-end SPD fixed bed, with an HRT of 1.7h. The sewage flows from the bottom channel into the filler area through the lower filter plate. The denitrifying bacteria use the organic matter adsorbed by the biochar bricks in the filler area as a carbon source to remove the residual nitrate in the sewage. The effluent after deep denitrification passes through the upper filter plate from the filler area into the V-shaped trough and is finally discharged from the rear-end inlet / outlet channel. The final effluent TN is less than 15mg / L, NO 3- <3mg / L;

[0089] (3) Reverse operation control: The controller will judge whether the biochar bricks in the front-end SPD fixed bed are in a saturated state of organic matter adsorption based on the DO concentration and nitrate nitrogen concentration data monitored in real time by the DO detector and the nitrate nitrogen detector. When the controller believes that the biochar bricks in the front-end SPD fixed bed are saturated with adsorption, it will change the inlet and outlet direction of the sewage, and the sewage will enter the rear-end SPD fixed bed from the rear-end inlet / outlet channel. At this time, the rear-end SPD fixed bed is responsible for removing organic matter from the sewage by utilizing the adsorption effect of the cubic biochar bricks inside it, while the front-end SPD fixed bed is responsible for utilizing the organic matter adsorbed by the cubic biochar bricks inside it as a carbon source for denitrifying bacteria to remove residual nitrate in the sewage. The entire treatment process is consistent with the treatment process of forward operation control.

[0090] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations. The phrase "includes an element defined by..." does not exclude the presence of other identical elements in the process, method, article, or device that includes the element.

[0091] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0092] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A sewage treatment method based on PN / A coupled biochar SPD, characterized in that: include: The sewage enters the front-end SPD fixed bed (2a) from the front-end inlet / outlet channel (204), and the front-end SPD fixed bed (2a) removes organic matter in the sewage by utilizing the adsorption effect of the biochar bricks inside the bed; The wastewater after organic matter removal enters the front-end upflow / downflow trough (3a) from the front-end SPD fixed bed (2a). The wastewater enters the PN / A reactor (1) after upflow and downflow in the front-end upflow / downflow trough (3a). The PN / A reactor (1) denitrifies the sewage by using the nitrite sludge and fully autotrophic denitrification granular sludge inoculated therein, and the DO concentration and nitrate nitrogen concentration in the PN / A reactor (1) are detected in real time by a DO detector and a nitrate nitrogen detector; The denitrified wastewater enters the rear-end upflow / downflow trough (3b) from the PN / A reactor (1), and the effluent enters the rear-end SPD fixed bed (2b) after upflow and downflow in the rear-end upflow / downflow trough (3b); Denitrifying bacteria use the organic matter adsorbed by the biochar bricks inside the back-end SPD fixed bed (2b) as a carbon source to remove the residual nitrate in the sewage. The effluent after deep denitrification is finally discharged from the back-end inlet / outlet channel (204); The biochar brick is a cubic biochar brick with honeycomb-shaped holes inside. The preparation steps of the biochar brick are as follows: first, the municipal sludge is conditioned and reshaped, and then the dehydrated cake is formed into a dehydrated cake. The dehydrated cake is then crushed into municipal sludge particles by a crusher. The municipal sludge particles are then sent to a drying furnace and dried at 120°C for 60 minutes. Thereafter, the municipal sludge particles are pyrolyzed by a muffle furnace at a pyrolysis temperature of 600°C, a nitrogen flow rate of 0.5L / min, a heating rate of 10°C / min, and a drying temperature of 600°C. Pyrolysis is carried out under an inert N2 atmosphere for 2-3 hours to produce sludge carbon, which is then placed naturally to cool to room temperature; the cooled sludge carbon is washed with deionized water, and solid-liquid separation is performed after washing until the washing liquid is neutral. The obtained solid phase is dried to obtain impurity-removed sludge carbon, which is then ground with a mechanical grinder and then sieved through a 0.6mm sieve; the zeolite is washed with deionized water, and solid-liquid separation is performed after washing until the washing liquid is neutral. The obtained solid phase is dried to obtain impurity-removed zeolite, which is then used The impurity-removed zeolite was ground by a mechanical grinder and then sieved through a 0.6 mm mesh. Nanosilica, impurity-removed zeolite and impurity-removed sewage sludge were ground in a ball mill at a speed of 800 rpm for 20 min. The ground mixture was added to the suspension and stirred on a magnetic stirrer for 3 h. The sewage sludge impregnated with nanosilica and zeolite was separated and dried at 80°C to obtain the sewage sludge raw material. The clay-treated sewage sludge raw material was placed in a quartz tube in a tubular furnace and dried under an inert gas atmosphere of N2. 2 atmosphere, pyrolysis was carried out at a pyrolysis temperature of 600-800°C, and the nano-silica modified sludge carbon material was slowly pyrolyzed for 1 hour to obtain the nano-silica modified sludge carbon material; the obtained nano-silica modified sludge carbon material was then ground in an electric-controlled mortar and pestle for 30 minutes, and then ground in a turbo grinder at 50 Hz and 1000 revolutions per minute for 3 hours to obtain micron-sized nano-silica modified sludge carbon material; the obtained micron-sized nano-silica modified sludge carbon material was made into cubic biochar bricks with honeycomb holes inside using 3D printing technology; The structure of the front-end upflow / downflow trough (3a) is bilaterally symmetrical to that of the rear-end upflow / downflow trough (3b), and both consist of side-by-side outer troughs (301) and inner troughs (302). The outer troughs (301) and the inner troughs (302) are connected via an overflow port (303) at the top. The outer troughs (301) are connected to the front-end SPD fixed bed (2a) or the rear-end SPD fixed bed (2b) via an outer water hole (304) at the bottom. The inner troughs (302) are connected to the PN / A reactor (1) via an inner water hole (305) at the middle and lower part. One of the outer troughs (301) and the inner trough (302) serves as an upflow zone, and the other serves as a downflow zone. During the denitrification process of the sewage in the PN / A reactor (1), the DO detector and the nitrate nitrogen detector will feed back the monitored DO concentration and nitrate nitrogen concentration data to the controller in real time, and the controller will judge the organic matter adsorption state of the biochar bricks in the front-end SPD fixed bed (2a) based on the sent back DO concentration and nitrate nitrogen concentration data; When the controller detects that the biochar bricks in the front-end SPD fixed bed (2a) are saturated with adsorption, the controller changes the inlet and outlet directions of the sewage, and the sewage enters the rear-end SPD fixed bed (2b) from the rear-end inlet / outlet channel (204); at this time, the rear-end SPD fixed bed (2b) is responsible for removing organic matter in the sewage by utilizing the adsorption effect of the cubic biochar bricks inside it, while the front-end SPD fixed bed (2a) is responsible for utilizing the organic matter adsorbed by the cubic biochar bricks inside it as a carbon source for denitrifying bacteria to remove residual nitrate in the sewage, thereby achieving resource utilization of organic matter in the sewage while completing deep denitrification.

2. The sewage treatment method based on PN / A coupled biochar SPD according to claim 1, characterized in that: Before sewage treatment, nitrite sludge and fully autotrophic denitrifying granular sludge are inoculated in a certain proportion in the PN / A reactor (1) so that the sludge concentration in the PN / A reactor (1) is maintained within a certain range; and a plurality of biochar bricks are respectively stacked in the packing area (201) inside the front-end SPD fixed bed (2a) and the rear-end SPD fixed bed (2b).

3. The sewage treatment method based on PN / A coupled biochar SPD according to claim 2, characterized in that: The particle sizes of the nitrite sludge and the fully autotrophic denitrification granular sludge are both 0.5-3 mm, and the inoculation volume ratio of the nitrite sludge to the fully autotrophic denitrification granular sludge is 1:1, so that the sludge concentration MLSS of the PN / A reactor (1) is maintained at 3000-9000 mg / L.

4. The sewage treatment method based on PN / A coupled biochar SPD according to claim 1 or 2, characterized in that: The ratio of length, width and height of the biochar brick is 1:1:1, the pore radius is 50 mm, and the specific surface area is 80-120 m 2 / g, porosity is 50%-70%, flow rate in the pore is 0.8-1.2m / s, and organic matter removal rate is 75-90%.

5. The sewage treatment method based on PN / A coupled biochar SPD according to claim 1, characterized in that: When the front-end SPD fixed bed (2a) or the rear-end SPD fixed bed (2b) removes organic matter from sewage, the HRT is 1-4h and the COD load is 0.25-2kg·m -3 ·d -1 , COD removal rate is 75-90%.

6. The sewage treatment method based on PN / A coupled biochar SPD according to claim 1, characterized in that: When the PN / A reactor (1) is used to denitrify wastewater, the HRT is 0.5-3h and the NLR is 0.5-4 kg·m -3 ·d -1 The ammonia nitrogen removal rate is 80%-95%.

7. The sewage treatment method based on PN / A coupled biochar SPD according to claim 6, characterized in that: When the PN / A reactor (1) is denitrifying the sewage, aeration is performed by the air compressor and the aeration head to ensure that the sewage and the granular sludge in the PN / A reactor (1) are completely mixed, and the DO concentration in the PN / A reactor (1) is monitored in real time by a DO detector to maintain the DO concentration at 2 mg / L.

8. The sewage treatment method based on PN / A coupled biochar SPD according to claim 1, characterized in that: When the rear-end SPD fixed bed (2b) or the front-end SPD fixed bed (2a) removes nitrate from sewage, the HRT is 0.5-3h.

Images