A sludge treatment process for simultaneous recovery of carbon source and phosphorus

Abstract

The present application provides a sludge treatment process for synchronously recycling carbon source and phosphorus. The sludge treatment process of the present application comprises: adding sludge to be treated into a pretreatment tank to adjust the sludge to be treated to be acidic or alkaline, pretreating the sludge to be treated to obtain pretreated sludge, and then performing anaerobic fermentation. The sludge treatment process of the present application can simultaneously realize effective recycling and utilization of the carbon source and phosphorus in the sludge. The recycled anaerobic fermentation liquid can be used for carbon source required for denitrification and phosphorus removal in a biological tank. The use of the anaerobic fermentation liquid as carbon source can obviously improve the abundance of short-cut denitrifying bacteria and denitrifying bacteria in the biological tank, obviously reduce the abundance of filamentous bacteria, and increase the types of microorganisms. The biological carbon prepared from the sludge after fermentation can be used as landscape phosphorus fertilizer, and good economic benefits can be achieved. The sludge treatment process of the present application realizes zero solid waste discharge, and completely reduces the residual sludge, thereby solving the problems of high disposal cost and insufficient disposal capacity of residual sludge in a sewage plant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sludge resource utilization, and particularly relates to a sludge treatment process for simultaneously recovering carbon source and phosphorus. BACKGROUND

[0002] With the rapid development of urbanization and the continuous increase of sewage treatment capacity, the amount of sludge produced in sewage treatment plants is also increasing day by day. The treatment and disposal of these sludge has become an increasingly urgent problem. At the same time, sludge treatment and disposal mainly involves landfill or incineration of dewatered sludge, but the traditional landfill and incineration methods not only occupy a large amount of land resources and waste potential resources of sludge, but also may cause potential risks to the environment. Therefore, it is urgent to achieve on-site treatment of municipal sludge in sewage plants to reduce the transportation and disposal cost of sludge and reduce the environmental risk.

[0003] However, when choosing a sludge treatment method, multiple factors must be carefully considered. As a product of the sewage treatment process, the excess sludge is rich in organic matter and pollutant substances, and has the dual attributes of "pollution" and "resource". The excess sludge is mainly composed of organic matter, extracellular polymeric substances, refractory organic matter and inorganic substances, and the organic substances such as proteins, polysaccharides and lipids contained therein can be considered for resource recovery. Anaerobic fermentation of excess sludge can recover valuable products in the sludge, such as short-chain fatty acids (SCFAs), which mainly include organic acids such as acetic acid, propionic acid, isobutyric acid, n-butyric acid, isovaleric acid and n-valeric acid. Compared with methane fermentation, anaerobic fermentation of excess sludge has a shorter cycle, and SCFAs are safer to store and transport, and can be used as a carbon source for denitrification and phosphorus removal in a biological tank, to some extent, solving the problem of insufficient carbon source in the influent of sewage plants in China. At present, a considerable number of sewage treatment plants have the problem of high cost of external carbon source. In view of the high price of external carbon source, this will increase the operating cost of the sewage plant, so when choosing a treatment method, the technology that can efficiently utilize the self-carbon source in the sludge should be given priority. At the same time, the sludge is also rich in phosphorus resources, and phosphorus is an important agricultural nutrient element and is essential for the growth and development of plants. However, if the phosphorus in the sludge is not properly treated, not only will this valuable resource be wasted, but also environmental pollution may occur.

[0004] Therefore, an ideal sludge treatment method should be able to simultaneously achieve efficient recovery and utilization of the self-carbon source and phosphorus in the sludge, thereby creating economic value and reducing the risk of environmental pollution. However, the current sludge treatment methods do not achieve efficient recovery and utilization of the carbon source and phosphorus. SUMMARY

[0005] Therefore, the present application provides a sludge treatment process for simultaneously recovering carbon source and phosphorus to solve the defects in the prior art.

[0006] In a first aspect, the present application provides a sludge treatment process for synchronously recovering carbon source and phosphorus, comprising the following steps:

[0007] The sludge to be treated is added into a pretreatment tank, the sludge to be treated is adjusted to be acidic or alkaline, the sludge to be treated is pretreated, and pretreated sludge is obtained;

[0008] The pretreated sludge is further added into an anaerobic fermentation tank for anaerobic fermentation.

[0009] Preferably, the fermentation liquor after anaerobic fermentation can enter a phosphorus adsorption column for recovery of phosphorus resources;

[0010] The fermentation liquor after anaerobic fermentation can be used as a carbon source for denitrification and phosphorus removal treatment of sewage plant sewage;

[0011] The sludge to be treated is added into a pretreatment tank, iron-based material is added into the pretreatment tank, the sludge to be treated is adjusted to be acidic or alkaline, the sludge to be treated is pretreated, and pretreated sludge is obtained;

[0012] The bottom sludge after anaerobic fermentation is separated by a magnetic drum to obtain iron-based material, and the separated iron-based material is added into the pretreatment tank for the next round of anaerobic fermentation;

[0013] A part of the bottom sludge after magnetic drum separation and / or a part of sludge produced after denitrification and phosphorus removal treatment of sewage plant sewage are dewatered in a sludge dewatering device and then pyrolyzed in a sludge pyrolysis device to obtain biochar.

[0014] Preferably, the iron-based material is Fe-Fe2O3 core-shell material;

[0015] The acidic pH is 5-6, and the alkaline pH is 8-12;

[0016] The sludge to be treated is pretreated, and the pretreatment time is 12-24 h.

[0017] Preferably, the temperature of the anaerobic fermentation is 15-35℃;

[0018] And / or, the MLSS in the sludge to be treated is 10.1-14.4 g / L, and the MLVSS is 4.9-7.4 g / L;

[0019] And / or, the addition amount of the iron-based material is: 0.1-0.5 g Fe-Fe2O3 core-shell material per g VSS;

[0020] And / or, the anaerobic fermentation time is 1-14 d;

[0021] and / or, the pretreated sludge is added into the anaerobic fermentation tank at the same time with inoculated sludge, the MLSS of the inoculated sludge is 33.6-34.4 g / L, and the MLVSS is 22.2-22.6 g / L.

[0022] Preferably, the fermentation liquor after anaerobic fermentation can be used as a carbon source for denitrification and phosphorus removal treatment of sewage in a sewage plant, which specifically includes:

[0023] The fermentation liquor after anaerobic fermentation is added to sewage to be treated in a sewage plant for denitrification and phosphorus removal treatment; wherein, after adding the fermentation liquor, the COD / TN ratio in the sewage is 7.3-7.5.

[0024] Preferably, a part of the bottom sludge after magnetic drum separation and / or a part of the sludge produced after denitrification and phosphorus removal treatment of sewage in a sewage plant are subjected to sludge dewatering in a sludge dewatering device before being dewatered, and Fenton reagent is used as a conditioner for conditioning the sludge, wherein the conditioning specifically includes:

[0025] FeSO4 is added to a part of the bottom sludge after magnetic drum separation and / or a part of the sludge produced after denitrification and phosphorus removal treatment of sewage in a sewage plant, stirred at 130-170 r / min for 5-10 min, then H2O2 is added and stirred at 80-120 r / min for 5-10 min, and the conditioning is completed;

[0026] wherein, the Fe in FeSO4 is 50-60% (w / w). 2+ The addition amount is: 80-150 mg Fe per g VSS 2+ ; the addition amount of H2O2 is 60-100 mg H2O2 per g VSS.

[0027] Preferably, the sludge dewatering in the sludge dewatering device specifically includes: the sludge conditioned by Fenton reagent is transported to a plate-and-frame filter press using an air compressor for sludge dewatering; wherein, the sludge inlet pressure of the air compressor is 0.5-1 MPa, and after completion of sludge inlet, dewatering is performed at a pressure of 0.5-1 MPa for 5-10 min;

[0028] Then the sludge dewatered in the plate-and-frame filter press is transported to a diaphragm filter press using an air compressor for dewatering; wherein, the sludge inlet pressure of the air compressor is 1-1.2 MPa, and after completion of sludge inlet, dewatering is performed at a pressure of 1-1.2 MPa for 5-10 min;

[0029] The sludge dewatered in the diaphragm filter press is dried, then sieved through a 0.5-1 mm sieve, and the undersize is used for subsequent pyrolysis.

[0030] Preferably, the pyrolysis specifically includes:

[0031] The undersize is placed in a tube furnace, and heated to 300-900 DEG C at 8-12 DEG C / min under inert atmosphere, and kept for 1-3 h to obtain the biochar.

[0032] Preferably, the sludge to be treated is added into a sludge storage tank, and then pumped into a pretreatment tank;

[0033] Another part of the bottom layer sludge after magnetic drum separation and / or the sewage plant sewage is subjected to denitrification and phosphorus removal treatment to produce another part of sludge, which is added into the sludge storage tank for pretreatment and anaerobic fermentation again.

[0034] The phosphorus adsorption material used in the phosphorus adsorption column comprises at least one of the biochar and a lanthanide compound.

[0035] In a second aspect, the application further provides a use of the biochar prepared by the sludge treatment process as a phosphorus fertilizer.

[0036] Compared with the prior art, the application has the following beneficial effects:

[0037] The sludge treatment process can realize effective recovery and utilization of the carbon source and phosphorus in the sludge, the recovered anaerobic fermentation liquid can be used as the carbon source required for denitrification and phosphorus removal in the biological tank, the fermentation liquid after anaerobic fermentation can obviously improve the abundance of short-range denitrifying bacteria and denitrifying bacteria in the biological tank, obviously reduce the abundance of filamentous bacteria, and increase the types of microorganisms, the biochar prepared from the sludge after fermentation can be used as a landscape phosphorus fertilizer, and good economic benefits can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0039] Figure 1 The process flow chart of the application;

[0040] Figure 2 The SCFAs yield chart of the anaerobic fermentation tank under different temperatures in Example 1;

[0041] Figure 3 The SCFAs yield chart of the anaerobic fermentation tank under different types of sludge sources in Example 2;

[0042] Figure 4Figure for the change of nitrate nitrogen in different kinds of carbon sources in Example 3;

[0043] Figure 5 Figure for the change of COD removal rate in AAO biological tank in Example 4;

[0044] Figure 6 Figure for the change of TN removal rate in AAO biological tank in Example 4;

[0045] Figure 7 Figure for the change of TP removal rate in AAO biological tank in Example 4;

[0046] Figure 8 Figure for the genus level distribution of microbial population in the anaerobic section in different stages in Example 4;

[0047] Figure 9 Figure for the genus level distribution of microbial population in the anoxic section in different stages in Example 4;

[0048] Figure 10 Figure for the genus level distribution of microbial population in the aerobic section in different stages in Example 4;

[0049] Figure 11 Figure for the distribution of phosphorus forms in sludge and biochar in Example 5;

[0050] Figure 12 Figure for the adsorption isotherm fitting of Fe-300 biochar in Example 6;

[0051] Figure 13 Figure for the comparison of seed germination rates of different biochars in Example 7;

[0052] Figure 14 Figure for the comparison of growth effects and shoot lengths of different biochars in Example 7. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0054] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0055] This application provides a sludge treatment process for simultaneous recovery of carbon sources and phosphorus, including the following steps:

[0056] S1. Add the sludge to be treated into the pretreatment tank, adjust the sludge to be treated to be acidic or alkaline, and pretreat the sludge to obtain pretreated sludge.

[0057] S2. Then add the pretreated sludge into the anaerobic fermentation tank for anaerobic fermentation.

[0058] In some embodiments, the fermentation broth after anaerobic fermentation can be fed into a phosphorus adsorption column for phosphorus resource recovery.

[0059] In some embodiments, the fermentation broth after anaerobic fermentation can be used as a carbon source to treat wastewater from sewage treatment plants for nitrogen and phosphorus removal.

[0060] In some embodiments, the sludge to be treated is added to a pretreatment tank, iron-based materials are added to the pretreatment tank, and the sludge to be treated is adjusted to be acidic or alkaline to pretreat the sludge and obtain pretreated sludge.

[0061] In some embodiments, the bottom sludge after anaerobic fermentation is separated by magnetic drum recycling to obtain iron-based material, and the separated iron-based material is added to a pretreatment tank for the next round of anaerobic fermentation.

[0062] A portion of the bottom sludge after magnetic drum separation and / or a portion of the sludge produced after denitrification and phosphorus removal from wastewater treatment plants are dewatered in a sludge dewatering unit and then pyrolyzed in a sludge pyrolysis unit to obtain biochar.

[0063] In some embodiments, the sludge to be treated in this invention can be various types of municipal sludge, such as primary sludge and residual sludge generated by different treatment processes.

[0064] In some embodiments, the iron-based material is a Fe-Fe2O3core-shell material.

[0065] In some embodiments, the acidic pH is 5-6 and the basic pH is 8-12; specifically, the sludge is adjusted to be acidic by using hydrochloric acid or sulfuric acid, and the sludge is adjusted to be basic by using sodium hydroxide or ammonia water.

[0066] In some embodiments, the sludge to be treated is pretreated, the pretreatment time is 12-24 h, and the pretreatment temperature is 15-35°C.

[0067] In some embodiments, the temperature of the anaerobic fermentation is 15-35°C, or no heating device is provided and no temperature control is performed.

[0068] In some embodiments, the anaerobic fermentation tank adopts a semi-continuous flow process, and the processes of stirring, standing, water discharge, and sludge feeding are performed in a cycle, the ratio of stirring time to standing time can be set to 11 h: 1 h or 23 h: 1 h, and the hydraulic retention time can be set to 4-6 days.

[0069] In some embodiments, the MLSS in the sludge to be treated is 10.1-14.1 g / L, and the MLVSS is 4.9-7.4 g / L.

[0070] Specifically, the MLVSS is the concentration of volatile suspended solids in the sludge, the MLSS is the concentration of total suspended solids, and the MLVSS / MLSS represents the content of volatile substances in the sludge, which is related to the activity of the sludge.

[0071] In some embodiments, the amount of the iron-based material added is: 0.1-0.5 g of the Fe-Fe2O3core-shell material per g of VSS (indicating the mass of volatile suspended solids in the sludge). That is, the amount of the Fe-Fe2O3core-shell material added is determined according to the mass of the VSS volatile suspended solids in the sludge, and the amount of the Fe-Fe2O3core-shell material added is 0.1-0.5 g per g of the mass of the VSS volatile suspended solids in the sludge.

[0072] In some embodiments, the anaerobic fermentation time is 1-14 d.

[0073] Preferably, the MLVSS in the sludge to be treated is 6.9±0.5 g / L, and the MLSS is 13.1±0.7 g / L; the MLVSS in the sludge to be treated is 6.9±0.5 g / L, and the MLSS is 13.1±0.7 g / L; the MLVSS in the sludge to be treated is 6.1±0.7 g / L, and the MLSS is 12.5±0.4 g / L; the MLVSS in the sludge to be treated is 5.6±0.7 g / L, and the MLSS is 10.5±0.4 g / L; and the MLVSS in the sludge to be treated is 7.1±0.3 g / L, and the MLSS is 13.5±0.6 g / L.

[0074] In some embodiments, the pretreated sludge is added to the anaerobic fermentation tank at the same time as the inoculated sludge; the inoculated sludge is an anaerobic fermentation acid-producing sludge that has been long-term operated under the conditions of pH = 5.5 ± 0.2, ORP = -300 ± 20 mv, and 35 ± 0.5°C.

[0075] In some embodiments, the MLSS of the inoculated sludge is 33.6-34.4 g / L, and the MLVSS is 22.2-22.6 g / L. Preferably, the MLSS of the inoculated sludge is 34.0 ± 0.4 g / L, the MLVSS is 22.4 ± 0.2 g / L, and the MLVSS / MLSS is 0.66.

[0076] In some embodiments, 0.8-1.2 L of the inoculated sludge and 3.5-4.5 L of the pretreated sludge are added to the anaerobic fermentation tank, and anaerobic fermentation is performed at 15-35°C for 1-14 d, using a semi-continuous flow mode, i.e., stirring for 20-23 h per day, and the rest of the time being static settling. After static settling, 1-1.5 L of the sludge after fermentation in the anaerobic fermentation tank is discharged, and then 1-1.5 L of the pretreated sludge is added again. The anaerobic fermentation is performed in this way for 1-14 d.

[0077] In some embodiments, the fermentation liquor after anaerobic fermentation can be used as a carbon source for denitrification and phosphorus removal treatment of wastewater in a wastewater treatment plant, and the treatment specifically includes:

[0078] The fermentation liquor after anaerobic fermentation is added to wastewater to be treated in a wastewater treatment plant for denitrification and phosphorus removal treatment. After the addition of the fermentation liquor, the COD / TN ratio in the wastewater is 7.3-7.5.

[0079] Preferably, in some embodiments, the initial TN content in the wastewater to be treated is 33.4-38.6 mg / L, and the initial COD content is 235.6-272.8 mg / L. After the addition of the fermentation liquor, the COD / TN ratio is 7.3-7.5.

[0080] In some embodiments, a part of the bottom sludge after magnetic drum separation and / or a part of the sludge produced after denitrification and phosphorus removal treatment of wastewater in a wastewater treatment plant are subjected to sludge dewatering in a sludge dewatering device. Before the dewatering, Fenton reagent is used as a conditioner to condition the sludge, and the conditioning specifically includes:

[0081] FeSO4 is added to a part of the bottom sludge after magnetic drum separation and / or a part of the sludge produced after denitrification and phosphorus removal treatment of wastewater in a wastewater treatment plant, and stirring is performed at 130-170 r / min for 5-10 min. Then, H2O2 is added, and stirring is performed at 80-120 r / min for 5-10 min, thereby completing the conditioning.

[0082] In the FeSO4, the Fe content is 0.1-0.3 g / L.2+ The amount of addition is: 80-150 mg Fe per g VSS (the mass of volatile solids suspended in sludge) 2+ The amount of addition is: 60-100 mg H2O2 per g VSS (the mass of volatile solids suspended in sludge) (specifically, an H2O2 aqueous solution with a mass concentration of 10-40%).

[0083] In some embodiments, the sludge dewatering device performs dewatering specifically comprising: using an air compressor to deliver the sludge conditioned by the Fenton reagent to a plate-and-frame filter press for sludge dewatering; wherein the sludge inlet pressure of the air compressor is 0.5-1 MPa, and after completing sludge inlet, dewatering is performed at a pressure of 0.5-1 MPa for 5-10 min;

[0084] Then, using an air compressor to deliver the sludge dewatered by the plate-and-frame filter press to a diaphragm filter press for dewatering; wherein the sludge inlet pressure of the air compressor is 1-1.2 MPa, and after completing sludge inlet, dewatering is performed at a pressure of 1-1.2 MPa for 5-10 min;

[0085] After the sludge dewatered by the diaphragm filter press is dried, it is sieved through a 0.5-1 mm sieve, and the undersize is used for subsequent pyrolysis.

[0086] In some embodiments, the pyrolysis specifically comprises:

[0087] The undersize is placed in a tube furnace, heated to 300-900℃ at a rate of 8-12℃ / min under an inert atmosphere, and held for 1-3 h to obtain biochar.

[0088] Specifically, the inert atmosphere includes at least one of nitrogen, helium, neon, and argon, and preferably, nitrogen is used; the undersize is placed in a tube furnace, and high-purity argon is introduced for 10-20 min at a flow rate of 50-150 mL / min to ensure that the tube furnace is filled with argon.

[0089] In some embodiments, the sludge to be treated is added to a sludge storage tank, and then the sludge to be treated is pumped into a pretreatment tank;

[0090] Another part of the sludge and / or sewage plant sewage separated by the magnetic drum is subjected to denitrification and phosphorus removal treatment to produce another part of the sludge, which is then added to the sludge storage tank for pretreatment and anaerobic fermentation again;

[0091] The phosphorus adsorption material used in the phosphorus adsorption column includes at least one of biochar and lanthanide compounds; preferably, the biochar prepared by the present application is used.

[0092] In some embodiments, the preparation method of the Fe-Fe2O3 core-shell material comprises the following steps:

[0093] adding the ferric salt into water to obtain a ferric solution;

[0094] adding the reducing agent into water to obtain a reducing agent solution;

[0095] adding the reducing agent solution into the ferric solution, reacting, filtering and drying to obtain the Fe-Fe2O3 core-shell material;

[0096] The ferric salt includes at least one of FeCl3, ferric sulfate and ferric nitrate;

[0097] The reducing agent includes at least one of NaBH4, Al(BH4)3, KBH4 and hydrazine hydrate;

[0098] The reducing agent solution is added into the ferric solution at a flow rate of 0.1-0.3 mL / s;

[0099] In the step of adding the ferric salt into water, the mass ratio of the ferric salt to water is (1-5):(800-1200);

[0100] In the step of adding the reducing agent into water, the mass ratio of the reducing agent to water is (3-9):(300-500);

[0101] In some embodiments, the separated iron-based material is added into the pretreatment tank together with the newly prepared Fe-Fe2O3 core-shell material, wherein the mass ratio of the newly prepared Fe-Fe2O3 core-shell material to the separated Fe-Fe2O3 core-shell material is 1:(1-4). The recovered iron-based material can be used together with the newly prepared iron-based material, and the mass ratio of the new and old iron-based materials is 1:(1-4) according to the actual recovery rate.

[0102] Further, referring to Figure 1 The sludge treatment process of the present application for simultaneously recovering carbon source and phosphorus adopts the process of Figure 1The device shown is carried out; the device comprises: sludge storage tank 1, pretreatment tank 2, anaerobic fermentation tank 3, first sedimentation tank 4, phosphorus adsorption column 5, acid storage tank 6, biological treatment facility 7, second sedimentation tank 8, magnetic drum 9, sludge dewatering device 10, sludge pyrolysis device 11, first sludge pump 12, second sludge pump 13, third sludge pump 14, first peristaltic pump 15, dosing pump 16, fourth sludge pump 17, fifth sludge pump 18; the sludge storage tank 1 is connected with the pretreatment tank 2 through the first sludge pump 12, and the pretreatment tank 2 is provided with a stirring device and a pH online monitoring device; the pretreatment tank 2 is connected with the anaerobic fermentation tank 3 through the second sludge pump 13, and the anaerobic fermentation tank 3 is provided with a stirring device, a pH / ORP online monitoring device, a top water outlet and a bottom sludge outlet; the anaerobic fermentation tank 3 is connected with the first sedimentation tank 4 through the top water outlet via a gravity flow pipeline, the first sedimentation tank 4 is provided with a water outlet weir and a bottom sludge outlet, and the bottom sludge outlets of the anaerobic fermentation tank 3 and the first sedimentation tank 4 are connected with the magnetic drum 9 through the third sludge pump 14; the water outlet weir of the first sedimentation tank 4 is connected with the phosphorus adsorption column 5 through the first peristaltic pump 15; the phosphorus adsorption column 5 is connected with the acid storage tank 6 through a pressure pipeline; the acid storage tank 6 is connected with the biological treatment facility 7 through the dosing pump 16; the biological treatment facility 7 is connected with the second sedimentation tank 8 through a gravity flow pipeline; and the bottom sludge outlet of the second sedimentation tank 8 is connected with the sludge storage tank 1 through the fourth sludge pump 17;

[0103] Wherein, the sludge to be treated a is placed in the sludge storage tank 1 for standby, under the action of the first sludge pump 12, the sludge to be treated a in the sludge storage tank 1 is pumped into the pretreatment tank 2, at the same time, the iron-based material b is added into the pretreatment tank 2, and the pH is adjusted to the set range, under the action of the second sludge pump 12, the sludge to be treated and the iron-based material b in the pretreatment tank 2 are pumped into the anaerobic fermentation tank 3 for anaerobic fermentation; after the anaerobic fermentation, the fermentation liquor is separated into the sedimentation tank 4 for further clarification, then is pumped into the phosphorus adsorption column 5 through the first peristaltic pump 15 for the recovery of the phosphorus resource c, then the supernatant in the sedimentation tank 4 (i.e. the fermentation liquor after the recovery of the phosphorus resource) is pumped into the acid liquid storage tank 6 for storage standby, and is pumped into the biological treatment facility 7 through the dosing pump 15, and can be used as the carbon source d of the biological tank; the fermentation liquor d after the recovery of the phosphorus resource is used as the carbon source in the biological treatment facility 7 for the denitrification and phosphorus removal of the influent e of the sewage plant, after the clarification of the second sedimentation tank 8, the effluent f can reach the standard, and the residual sludge is added into the sludge storage tank 1 through the fourth sludge pump 17 for standby; further, after the fermentation of the sludge to be treated and the iron-based material b in the anaerobic fermentation tank 3, the fermentation liquor is stored into the first sedimentation tank 4 for solid-liquid separation, the sludge obtained by the bottom precipitation, and the bottom sludge after the fermentation of the anaerobic fermentation tank 3 are pumped into the magnetic drum 9 through the third sludge pump 14, the separated iron-based material is recovered through the magnetic drum 9, the separated iron-based material b is added into the pretreatment tank 2, i.e. the separated iron-based material b is reused for the next round of anaerobic fermentation, so that the cost is reduced; the sludge separated by the magnetic drum 9 and the excess residual sludge are put into the sludge dewatering device 10 and the sludge pyrolysis device 11 through the fifth sludge pump 18, and after the preparation of the biochar g, the biochar g can be used as landscape phosphorus fertilizer; the effluent of the anaerobic fermentation tank can be used as the carbon source of the biological tank after the sedimentation, and the sludge after the fermentation can use the magnetic drum to recover the iron-based material b for reuse.

[0104] The biological treatment facility 7 can adopt various treatment processes, such as AAO process, MBR process, CASS process, oxidation ditch process, etc.; the sludge pyrolysis device 11 can adopt a horizontal tubular furnace.

[0105] Based on the same inventive concept, the application further provides a use of the biochar prepared in the above-mentioned sludge treatment process as phosphorus fertilizer.

[0106] The sludge treatment process can realize the effective recovery and utilization of the carbon source and phosphorus in the sludge, the recovered anaerobic fermentation liquor can be used as the carbon source required for the denitrification and phosphorus removal of the biological tank, the prepared biochar can be used as landscape phosphorus fertilizer, and good economic benefits can be achieved; the sludge treatment process realizes zero solid waste discharge, and the residual sludge is completely reduced, so that the problems of high disposal cost and insufficient disposal capacity of the residual sludge of the sewage plant are solved.

[0107] The sludge treatment process for simultaneously recovering carbon source and phosphorus according to the present application is further illustrated below with specific examples. This part further illustrates the content of the present application in combination with specific examples, but should not be understood as a limitation of the present application. If not specifically stated, the technical means adopted in the examples are conventional means familiar to those skilled in the art. Unless specifically stated, the reagents, methods and equipment adopted by the present application are conventional reagents, methods and equipment in the art.

[0108] The preparation method of the Fe-Fe2O3 core-shell material used in the following examples includes the following steps:

[0109] S1, 3g of FeCl3·6H2O was added to 1000mL of deionized water to obtain a ferric iron solution;

[0110] S2, 6g of NaBH4 was added to 400mL of deionized water to obtain a NaBH4 solution;

[0111] S3, the NaBH4 solution was added to the ferric iron solution at a flow rate of 0.2mL / s (using a peristaltic pump), after the NaBH4 solution was completely added, the black precipitate was collected, then washed with deionized water, and finally dried under a nitrogen stream or vacuum environment to obtain the Fe-Fe2O3 core-shell material.

[0112] Example 1

[0113] The present application provides a sludge treatment process for simultaneously recovering carbon source and phosphorus, which includes the following steps:

[0114] S1, the residual sludge of the AAO biological tank of a sewage plant in Dongguan City was used, the MLVSS of the sludge was 6.9g / L, the MLSS was 13.1g / L, and the MLVSS / MLSS was 0.527, and the sludge was used as the sludge to be treated;

[0115] The sludge to be treated was added to the pretreatment tank, Fe-Fe2O3 core-shell material was added to the pretreatment tank, the pH of the sludge to be treated was adjusted to 6, and the pretreatment was carried out at 15℃ for 24h to obtain pretreated sludge; wherein the dosage of Fe-Fe2O3 core-shell material was 0.1g / gVSS;

[0116] S2, the inoculum sludge was an anaerobic fermentation acid-producing sludge which was long-term operated under the conditions of pH=5.5±0.2, ORP=-300±20mv, and 35±0.5℃; the MLSS of the inoculum sludge was 34.0g / L, the MLVSS was 22.4g / L, and the MLVSS / MLSS was 0.66;

[0117] 1L of inoculum sludge and 4L of pretreated sludge were added to an anaerobic digester. Anaerobic fermentation was carried out at 15°C using a semi-continuous flow method, i.e., stirring for 23 hours and settling for 1 hour daily. After settling, 1.25L of fermented sludge was discharged from the anaerobic digester, and then another 1.25L of pretreated sludge was added. Following this method, anaerobic fermentation for 1–14 days was recorded as the 15°C anaerobic fermentation group.

[0118] Following the above method, the pretreatment temperature was set to 25℃ and the anaerobic fermentation temperature was set to 25℃ respectively. All other process parameters were the same as in Example 1 above, resulting in a 25℃ anaerobic fermentation group.

[0119] Following the above method, the pretreatment temperature was set to 35℃ and the anaerobic fermentation temperature was set to 35℃ respectively. All other process parameters were the same as in Example 1 above, resulting in a 35℃ anaerobic fermentation group.

[0120] The Fe-Fe2O3 core-shell material with 0 g / g VSS was added according to the above method (i.e., no Fe-Fe2O3 core-shell material was added), and the other process parameters were the same as in Example 1 above, to obtain a blank control group.

[0121] After anaerobic fermentation according to the different schemes described above, the yield of short-chain fatty acids (SCFAs) in the fermentation broth was tested after 1–14 days of anaerobic fermentation. Figure 2 As shown.

[0122] Figure 2 In the table, 15℃, 25℃, and 35℃ represent the 15℃ anaerobic fermentation group, the 25℃ anaerobic fermentation group, and the 35℃ anaerobic fermentation group, respectively; Blank represents the blank control group.

[0123] Depend on Figure 2 The results showed that the peak SCFAs concentration in the blank control group was 2763 mg COD / L, with a mean of 2563 mg COD / L during the stationary phase; the peak SCFAs concentration in the 15℃ anaerobic fermentation group was 3796 mg COD / L, with a mean of 3514 mg COD / L during the stationary phase; the peak SCFAs concentration in the 25℃ anaerobic fermentation group was 4803 mg COD / L, with a mean of 4232 mg COD / L during the stationary phase; and the peak SCFAs concentration in the 35℃ anaerobic fermentation group was 5944 mg COD / L, with a mean of 5702 mg COD / L during the stationary phase. The high SCFAs yield indicates good carbon source recovery.

[0124] Example 2

[0125] This application provides a sludge anaerobic fermentation method, which sets up four anaerobic fermentation devices, and uses the residual sludge from the AAO process, MBR process, CASS process and oxidation ditch process of Dongguan Municipal Wastewater Treatment Plant as the sludge to be treated for fermentation. The properties of the sludge are shown in Table 1.

[0126] Anaerobic fermentation was carried out according to the method in Example 1, specifically including the following steps:

[0127] S1, the sludge to be treated was added to the pretreatment tank, Fe-Fe2O3 core-shell material was added to the pretreatment tank, the pH of the sludge to be treated was adjusted to 6, and the pretreatment was carried out at 35°C for 24h to obtain pretreated sludge; wherein the Fe-Fe2O3 core-shell material was added at a dosage of 0.1g / g VSS;

[0128] S2, the inoculated sludge was an anaerobic fermentation acid-producing sludge which was long-term operated under the conditions of pH = 5.5 ± 0.2, ORP = -300 ± 20mv, 35 ± 0.5°C; the MLSS of the inoculated sludge was 34.0 ± 0.4g / L, the MLVSS was 22.4 ± 0.2g / L, and the MLVSS / MLSS was 0.66;

[0129] 1L of the inoculated sludge and 4L of the pretreated sludge were added to the anaerobic fermentation tank, and anaerobic fermentation was carried out at 15°C in a semi-continuous flow mode, i.e. stirring for 23 hours per day, static settling for 1 hour, and then discharging 1.25L of the fermented sludge in the anaerobic fermentation tank, and then adding 1.25L of the pretreated sludge again; according to this method, the anaerobic fermentation was carried out for 1-9d.

[0130] According to the method in Example 2, the short-chain fatty acid (SCFAs) yield in the fermented liquid after the sludge from different sewage plants was anaerobically fermented for 1-9d was tested as shown in Table 2. Figure 3

[0131] Wherein the average SCFAs yield in the SCFAs of the sewage plant 1 group was 5384mgCOD / L, the average SCFAs yield in the sewage plant 2 group was 4515mgCOD / L, the average SCFAs yield in the sewage plant 3 group was 4509mgCOD / L, and the average SCFAs yield in the sewage plant 4 group was 5636mgCOD / L, indicating that the simultaneous recovery of carbon source and phosphorus municipal sludge waste-free treatment process in the present application is suitable for residual sludge of different process flows of different sewage plants.

[0132] Table 1- Properties of sludge from different sources (Note: the unit of sludge concentration is g / L)

[0133] Sewage plant Process Sampling point MLSS MLVSS VSS / SS Sewage plant 1 AAO Return sludge 13.1 6.9 0.526 Sewage plant 2 MBR Sludge storage tank sludge 12.5 6.1 0.488 Sewage plant 3 CASS Excess sludge 10.5 5.6 0.533 Sewage plant 4 Oxidation ditch Return sludge 13.5 7.1 0.526

[0134] Example 3

[0135] The present embodiment provides a method for applying anaerobic fermentation liquid as a carbon source for anoxic denitrification; specifically, according to the method of the blank group without adding Fe@Fe2O3 to strengthen sludge anaerobic fermentation group in Example 1, the fermentation liquid was obtained after anaerobic fermentation for 14d, and the fermentation liquid was used as a carbon source;

[0136] ​The sludge in the anoxic tank of a sewage plant in Wuhan was used as the denitrification seed sludge, with an MLVSS of 2200 mg / L and an MLSS of 3800 mg / L. The composite carbon source commonly used in Dongguan sewage plants (containing small molecule acids, sugars, and short-chain alcohols, and adding trace elements required for denitrification, with a COD content of 400,000 mg / L) and the fermentation broth described above (with a COD content of 1000 mg / L) were used as the denitrification carbon source, and the COD concentration in the reactor was controlled at 120 mg / L. Sodium nitrate was used to control the nitrate nitrogen concentration in the reactor to 30 mg / L (the COD / TN ratio after addition was controlled at 4, and the added COD was all biodegradable, and the TN in the reactor was mainly in the form of nitrate nitrogen). Four reactors (containing the denitrification seed sludge described above) were used, with no carbon source added, with the composite carbon source added, with the fermentation supernatant (i.e. fermentation broth) and the composite carbon source added at a ratio of 1:1, and with the fermentation supernatant (i.e. fermentation broth) added to control the COD concentration in the reactor. The nitrate nitrogen change trend is shown in Figure 4 As can be seen from the nitrate nitrogen change trend shown in

[0137] Example 4

[0138] The present embodiment provides a method for using anaerobic fermentation broth as a carbon source for an AAO biological tank. Specifically, according to the method of the 25°C anaerobic fermentation group in Example 1, after 14 days of anaerobic fermentation, fermentation broth is obtained, and the fermentation broth is used as a carbon source.

[0139] The effluent of the No. 1 fine screen of Dongguan Sewage Plant in Example 2 was used as the influent of the AAO device, and the sludge in the AAO biological tank of Sewage Plant 1 (i.e. the sludge in the anaerobic tank, anoxic tank, and aerobic tank) was collected as the seed sludge. The composite carbon source commonly used in Dongguan sewage plants (containing small molecule acids, sugars, and short-chain alcohols, and adding trace elements required for denitrification, with a COD content of 400,000 mg / L) and the fermentation broth described above were used as the external carbon source, and the influent flow rate was set at 50 L / d, Figures 5-6 As shown in the influent flow rate in the first stage of the test (i.e. the influent flow rate of the AAO device), the initial TN content in the sewage was 33.4-38.6 mg / L, and the initial COD content was 235.6-272.8 mg / L. After adding the carbon source, the COD / TN ratio was controlled at 7.4, and this technical index was derived from the average value of the COD / TN ratio after adding the carbon source in a sewage plant in Dongguan from December 2022 to December 2023). In the first stage of the test (i.e. Figures 5-7Stage Ⅰ), the composite carbon source from Dongguan municipal wastewater treatment plant was used as the carbon source, until the effluent quality was stable to enter the next stage, and the total operation time was 10 days; the second stage (i.e. Figures 5-7 Stage Ⅱ), the composite carbon source and the above-mentioned fermentation broth were added in a ratio of 1:1 (based on COD), and the total operation time was 8 days, in which the effect of denitrification and phosphorus removal in the biological tank was reduced due to the influence of cold wave (average temperature 5℃); the third stage (i.e. Figures 5-7 Stage Ⅲ), only the above-mentioned fermentation broth was used as the carbon source, and the total operation time was 7 days. The change trend of COD, TN and TP removal rates is shown in Figures 5-7 Table 1, and the significance analysis is shown in Table 2 (A is stage Ⅰ, B is stage Ⅱ, and C is stage Ⅲ).

[0140] Table 2- Significance test of COD removal rate in effluent of AAO biological tank in different stages

[0141]

[0142]

[0143] Note: * represents 10% significance level, ** represents 5% significance level, and ns represents no significant difference

[0144] Through the significance test of COD, TN and TP removal rates in the effluent of AAO biological tank in different stages, it can be analyzed that when the anaerobic fermentation broth is used as the carbon source, the COD and TN removal rates of AAO biological tank have no significant difference compared with stage Ⅰ, only the TP removal rate has significant difference, and the analysis Figure 7 shows that in stages Ⅱ and Ⅲ, the TP removal rate is slightly higher than that in stage Ⅰ, so it can be known that the anaerobic fermentation supernatant as the carbon source can promote the removal of TP to a certain extent. In general, it can be considered that the anaerobic fermentation broth can be used as the carbon source of AAO biological tank, and it will not have a negative impact on the operation effect.

[0145] The change of the genus level distribution of microbial population in each region (anaerobic section, anoxic section and aerobic section) in different stages was analyzed, and the results are shown in Figures 8-10 . Figure 8 Figure 1 is the genus level distribution diagram of microbial population in the anaerobic section in different stages; Figure 9 Figure 2 is the genus level distribution diagram of microbial population in the anoxic section in different stages; Figure 10 Figure 3 is the genus level distribution diagram of microbial population in the aerobic section in different stages; Figures 8-10 ana_1 is stage Ⅰ (i.e. adding composite carbon source), ana_1 is stage Ⅱ (adding composite carbon source and the above-mentioned fermentation broth in a ratio of 1:1 (based on COD)), and ana_1 is stage Ⅲ (adding the above-mentioned fermentation broth in a ratio of 1:1 (based on COD)).

[0146] AsFigure 9 As shown, common denitrifying bacteria such as Saccharimonadales, Ferruginibacter, OLB14, and Ottowia were detected in the sludge of the anoxic zone. In stages II and III, the abundance of Saccharimonadales decreased slightly compared to stage I (from 10.1% to 8.2% and 8.5%), while the abundance of Ferruginibacter increased from 7.5% to 7.8% and 8.5%, OLB14 increased from 2.8% to 3.1% and 3.1%, and Ottowia increased from 1.2% to 2.1% and 2.0%. This indicates that adding fermentation supernatant can increase the number of denitrifying bacteria in the anoxic tank, thereby enhancing the denitrification effect. The total abundance of the four denitrifying bacteria in stages I, II, and III was 21.6%, 21.2%, and 22.1%, respectively, indicating that the addition of fermentation broth after anaerobic fermentation had little effect on the total abundance. It can be considered that the addition of fermentation broth after anaerobic fermentation will not affect the AAO denitrification capacity.

[0147] like Figures 8-10 As shown, filamentous bacteria *Kouleothrix* were detected in all three areas of the AAO biological reactor, with average abundances of 4.9%, 4.0%, and 3.9% in the three stages, respectively. This indicates that the addition of fermentation broth after anaerobic fermentation can inhibit the growth of filamentous bacteria to a certain extent, reduce sludge bulking, and is beneficial to the normal operation of the AAO biological reactor. Simultaneously, COD-degrading bacteria such as SC-I-84, SBR1031, and C10-SB1A were also detected. The abundances of SC-I-84 were 6.3%, 5.2%, and 6.3%, respectively, and those of SBR1031 were 2.6%, 3.3%, and 2.0%, respectively. This indicates that the addition of fermentation broth after anaerobic fermentation has a relatively small impact on the total abundance of COD-degrading bacteria and will not significantly affect the COD removal rate of the AAO biological reactor.

[0148] Example 5

[0149] This embodiment provides a sludge pyrolysis method, using sludge produced after denitrification and phosphorus removal treatment of wastewater from a wastewater treatment plant; the sludge pyrolysis method includes the following steps:

[0150] S1. Add FeSO4 to the sludge and stir at 150 r / min for 5 min, then add H2O2 and stir at 100 r / min for 5 min to complete the conditioning.

[0151] Among them, FeSO4 contains Fe 2+ The dosage is: 110 mg Fe per gram of VSS (representing the mass of volatile suspended solids in the sludge). 2+; H2O2 is added in an amount of 88 mg per g of VSS (mass of volatile suspended solids in sludge) (specifically H2O2 solution with a mass concentration of 30%);

[0152] S2, the sludge after Fenton reagent conditioning is delivered to a plate and frame filter press by an air compressor for sludge dewatering; wherein the sludge inlet pressure of the air compressor is 0.8 MPa, and after completing sludge inlet, dewatering is performed at 0.8 MPa for 5 min;

[0153] The sludge after dewatering in the plate and frame filter press is delivered to a diaphragm filter press by an air compressor for dewatering; wherein the sludge inlet pressure of the air compressor is 1.1 MPa, and after completing sludge inlet, dewatering is performed at 1.1 MPa for 10 min;

[0154] The sludge after dewatering in the diaphragm filter press is placed in a 105℃ oven for drying for 24 h, is crushed, and is passed through a 0.8 mm sieve, and the undersize is taken for subsequent pyrolysis;

[0155] S3, the undersize is placed in a tube furnace, high-purity argon is introduced at a flow rate of 100 mL / min to ensure that the tube furnace is filled with argon, and then the temperature is raised to 300-900℃ (specifically, the temperature is raised to 300℃, 500℃, 700℃, 800℃, and 900℃, respectively) at a rate of 10℃ / min, and is held for 2 h to obtain biochar;

[0156] The biochar obtained by raising the temperature to 300℃, 500℃, 700℃, 800℃, and 900℃ is labeled as Fe-300, Fe-500, Fe-700, Fe-800, and Fe-900, respectively. The phosphorus form distribution of the sludge and the biochar is as shown in Figure 11 (b).

[0157] Comparative Example 1

[0158] This comparative example provides a sludge pyrolysis method, except that no reagent is added, and the sludge is directly dewatered by a plate frame, and the remaining steps are the same as those of Example 5; specifically, the sludge used is sludge produced after sewage treatment plant sewage is subjected to denitrification and phosphorus removal treatment; the sludge pyrolysis method comprises the following steps:

[0159] S1, the sludge is delivered to a plate and frame filter press by an air compressor for sludge dewatering; wherein the sludge inlet pressure of the air compressor is 0.8 MPa, and after completing sludge inlet, dewatering is performed at 0.8 MPa for 5 min;

[0160] The sludge after dewatering in the plate and frame filter press is delivered to a diaphragm filter press by an air compressor for dewatering; wherein the sludge inlet pressure of the air compressor is 1.1 MPa, and after completing sludge inlet, dewatering is performed at 1.1 MPa for 10 min;

[0161] The dewatered sludge from the diaphragm filter press was placed in a 105°C oven and dried for 24h, crushed and passed through a 0.8mm sieve, and the undersize was used for subsequent pyrolysis.

[0162] S2, the undersize was placed in a tube furnace, high-purity argon was introduced at a flow rate of 100mL / min to ensure that the tube furnace was filled with argon, and then heated to 300-900°C (specifically, to 300°C, 500°C, 700°C, 800°C and 900°C) at a rate of 10°C / min, and held for 2h to obtain biochar;

[0163] The biochar obtained by heating to 300°C, 500°C, 700°C, 800°C and 900°C was respectively marked as RS-300, RS-500, RS-700, RS-800 and RS-900. The phosphorus form distribution of the sludge and biochar is shown in Figure 11 (a).

[0164] Specifically, Figure 11 The 300°C, 500°C, 700°C, 800°C and 900°C in (a) refer to the biochar obtained by calcining at 300°C, 500°C, 700°C, 800°C and 900°C in Comparative Example 1. Figure 11 The 300°C, 500°C, 700°C, 800°C and 900°C in (b) refer to the biochar obtained by calcining at 300°C, 500°C, 700°C, 800°C and 900°C in Example 5.

[0165] Figure 11 H2O-P is water-soluble phosphorus (referred to as soluble phosphorus), NaHCO3-P is sodium bicarbonate-form phosphorus (referred to as exchangeable phosphorus), NaOH-P is sodium hydroxide-form phosphorus (referred to as iron and aluminum combined state phosphorus), HCl-P is hydrochloric acid-form phosphorus (referred to as calcium and magnesium combined state phosphorus), and Residue-P is residual-form phosphorus, Raw represents the initial sludge in Example 5 (i.e. the sludge used in step S1 in Example 5), and Ferric represents the sludge after dewatering by the diaphragm filter press in Example 5 step S2.

[0166] From Figure 11As can be seen, before pyrolysis, the main phosphorus form of the iron-rich sludge was NaOH-P, which was related to the high iron content in the iron-rich sludge, and thus more iron-aluminum combined state phosphorus was formed. With the pyrolysis temperature increasing from 300°C to 800°C, NaOH-P decreased and HCl-P increased, but NaOH-P was always higher than HCl-P. NaOH-P in the iron-rich sludge biochar had a certain advantage, and for plant growth, NaOH-P could be the preferred form of effective phosphorus. Compared with the pyrolysis of the original sludge, the total phosphorus content of the iron-rich sludge under the pyrolysis condition of 300-800°C increased significantly, and was converted into a more stable form of phosphorus, which reduced the mobility of phosphorus and increased the time of the bioavailability of phosphorus, creating a more persistent nutrient pool for plant growth.

[0167] Example 6

[0168] The embodiment of the present application provides a sludge biochar adsorbing phosphorus method, and the biochar used is Fe-300 biochar prepared in the embodiment 5. 0.3 g of Fe-300 biochar is weighed and added into 20 mL of KH2PO4 solution with a concentration of 23, 46, 68, 91, 115, 135, and 161 mg P / L respectively to obtain a mixed solution; the mixed solution is oscillated at 25°C and 150 r / min for 24 h, and the total phosphorus content in the solution is determined after solid-liquid separation. The adsorption isotherm is as shown in the following figure. Figure 12 In the figure, mg P / L KH2PO4 solution represents the mass (unit: mg) of P element contained in each L of KH2PO4 solution.

[0169] In order to analyze the adsorption amount of Fe-300 biochar under different initial concentrations of KH2PO4 solution, the Langmuir model and the Freundlich model of adsorption isotherm are used for fitting analysis, and the results are shown in Table 3.

[0170] Table 3-Fitting results of adsorption isotherm equation

[0171]

[0172] The correlation coefficient (R 2 = 0.986) of the Langmuir model is higher than that (R 2 = 0.936) of the Freundlich model. The adsorption parameter K F of the Freundlich model is 1.369 mg / g, which is much lower than the actual adsorption amount 2.628 mg / g; in comparison, the maximum adsorption amount q m of the Langmuir model is 2.643 mg / g, which is closer to the actual adsorption amount.

[0173] Example 7

[0174] This application provides a method for using sludge biochar as a landscape phosphate fertilizer. Fifty grass seeds (Pennisetum alopecuroides L.) are evenly scattered on a layer of filter paper moistened with deionized water and containing 0.1g of biochar (specifically, the Fe-300 biochar prepared in Example 5). The entire filter paper is then placed in a germination box for indoor cultivation. Meanwhile, a blank control group was used without the addition of biochar; and control groups were used with 0.1g of RS-300 biochar, Fe-300+AD biochar, and Fe-300+KH2PO4 biochar prepared in Comparative Example 1. Fe-300+AD biochar was prepared by adding 0.3g of Fe-300 biochar from Example 5 to 20mL of anaerobic fermentation supernatant (AD, whose basic characteristics are shown in Table 4 below), and shaking at 25℃ and 150r / min for 24h to allow it to adsorb the anaerobic fermentation supernatant, thus obtaining biochar. 0.1g of the adsorbed biochar was then used for subsequent experiments. Fe-300+KH2PO4 biochar was prepared by adding 0.3g of Fe-300 biochar from Example 5 to 20mL of KH2PO4 solution, and shaking at 25℃ and 150r / min for 24h to allow it to adsorb the KH2PO4 solution (containing 46mg of KH2PO4). Biochar was obtained by (P / L), and 0.1g of the adsorbed biochar was used for subsequent experiments.

[0175] In the above text, AD refers to the anaerobic fermentation supernatant. The basic characteristics of the anaerobic fermentation supernatant are shown in Table 4 below.

[0176] Table 4 - Basic Characteristics of Anaerobic Fermentation Supernatant

[0177]

[0178] The cultivation conditions were standardized as follows: temperature 25℃, humidity 70% RH, and CO2 concentration 800 ppm. After 3 days of cultivation, the seed germination rate was calculated. Figure 13 As shown, after 10 days of cultivation, the length of the tender shoots of 10 randomly selected plants was measured, and the results are as follows. Figure 14 As shown.

[0179] Figure 14 In the middle (a), from left to right, the plants are respectively the blank control, biochar with Fe-300+KH2PO4, biochar with Fe-300+AD, biochar with RS-300, and plants cultured with Fe-300 biochar.

[0180] from Figure 13As can be seen from Table 2, the addition of biochar increased the germination rate of seeds, and the germination rate of seeds increased more obviously in the groups of biochar added with adsorbed phosphorus (Fe-300+KH2PO4 and Fe-300+AD). The germination rate of seeds increased from 66% in the blank group to 92% and 96%, which indicated that biochar promoted the germination rate of seeds. Figure 14 As can be seen from Table 3, the actual effect of plant growth, in the groups of biochar added with adsorbed phosphorus, the plants grew more luxuriantly, the average height of plants was higher, and the leaf area was larger. Biochar not only improved the germination rate of seeds, but also promoted the growth of tender branches. It was indicated that sludge biochar could be used as high-quality landscape phosphorus fertilizer.

[0181] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sludge treatment process for simultaneous recovery of carbon source and phosphorus, characterized in that, The method comprises the following steps: adding the sludge to be treated into a pretreatment tank, adding an iron-based material into the pretreatment tank, adjusting the pH of the sludge to be treated to 6, and pretreating the sludge at 25℃ for 24 hours to obtain pretreated sludge; wherein the dosage of the iron-based material is 0.1 g / g VSS; the MLVSS of the sludge to be treated is 6.9 g / L, and the MLSS is 13.1 g / L; adding 1L of inoculated sludge and 4L of pretreated sludge into an anaerobic fermentation tank, and performing anaerobic fermentation at 25℃ in a semi-continuous flow mode, that is, stirring for 23 hours every day, static settling for 1 hour, discharging 1.25L of sludge after fermentation in the anaerobic fermentation tank, and then adding 1.25L of pretreated sludge again; according to this method, anaerobic fermentation is performed for 14 days; the MLSS of the inoculated sludge is 34.0 g / L, the MLVSS is 22.4 g / L, and the MLVSS / MLSS is 0.66; the iron-based material is a Fe-Fe2O3 core-shell material; the fermentation liquor after anaerobic fermentation is subjected to phosphorus resource recovery in a phosphorus adsorption column; the fermentation liquor after anaerobic fermentation is used as a carbon source for denitrification and phosphorus removal treatment of sewage in a sewage treatment plant, and the treatment specifically comprises: adding the fermentation liquor after anaerobic fermentation into sewage to be treated in the sewage treatment plant for denitrification and phosphorus removal treatment; wherein the COD / TN ratio in the sewage is 7.4 after adding the fermentation liquor; the initial TN content in the sewage is 33.4-38.6 mg / L, and the initial COD content is 235.6-272.8 mg / L; the bottom sludge after anaerobic fermentation is subjected to magnetic drum recovery and separation to obtain the iron-based material, and the separated iron-based material is added into the pretreatment tank for the next round of anaerobic fermentation; adding FeSO4 into a part of the bottom sludge after magnetic drum separation, stirring at 130-170 r / min for 5-10 min, then adding H2O2, and stirring at 80-120 r / min for 5-10 min, so as to complete sludge conditioning; wherein Fe in FeS04is Fe2+ 2+ The amount of addition is: 80~150mg Fe / g VSS 2+ The amount of addition of H2O2 is 60~100mg H2O2 / g VSS the conditioned sludge is subjected to dewatering in a sludge dewatering device, and the dewatering specifically comprises: the Fenton reagent conditioned sludge is conveyed to a plate and frame filter press by an air compressor for sludge dewatering; wherein the sludge inlet pressure of the air compressor is 0.5-1 MPa, and the sludge is dewatered at a pressure of 0.5-1 MPa for 5-10 min after sludge inlet is completed; then the sludge dewatered by the plate and frame filter press is conveyed to a diaphragm filter press by the air compressor for dewatering; wherein the sludge inlet pressure of the air compressor is 1-1.2 MPa, and the sludge is dewatered at a pressure of 1-1.2 MPa for 5-10 min after sludge inlet is completed; the sludge dewatered by the diaphragm filter press is dried, sieved through a 0.5-1 mm sieve, and the undersize is taken for subsequent pyrolysis; the pyrolysis specifically comprises: placing the undersize into a tubular furnace, heating to 300℃ at 8-12℃ / min in an inert atmosphere, and keeping the temperature for 1-3 hours to obtain biochar; the biochar is used as a phosphorus fertilizer after adsorbing the fermentation liquor after anaerobic fermentation.

2. The sludge treatment process according to claim 1, characterized in that adding the sludge to be treated into a sludge storage tank, and then pumping the sludge to be treated into a pretreatment tank; wherein the other part of the bottom sludge after magnetic drum separation is put into the sludge storage tank for pretreatment and anaerobic fermentation again. The phosphorus adsorption material used in the phosphorus adsorption column includes at least one of the biochar and a lanthanide series compound.

Images