CN115043563A - Device and method for strengthening anaerobic fermentation of excess sludge and strengthening nitrogen and phosphorus removal of sewage by fermentation liquor backflow - Google Patents
Device and method for strengthening anaerobic fermentation of excess sludge and strengthening nitrogen and phosphorus removal of sewage by fermentation liquor backflow Download PDFInfo
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Abstract
The invention discloses a method and a device for strengthening anaerobic fermentation of excess sludge and strengthening nitrogen and phosphorus removal of sewage by fermentation liquor backflow, wherein the method comprises the following steps: a pretreatment stage: adding an alkali solution and a complexing agent into the residual sludge obtained in the sewage treatment stage, and pre-stirring and mixing; an anaerobic fermentation stage; a nitrogen/phosphorus separation and recovery stage; and (5) a fermentation liquor recycling stage. The device comprises a pretreatment system, an anaerobic fermentation system, a nitrogen/phosphorus separation and recovery system and a fermentation liquid reflux system. The advantages include: the acid production effect of the anaerobic sludge is improved, and the main component of the produced VFA is acetic acid which is easy to be utilized by water treatment microorganisms, so that the release of nitrogen and phosphorus in sludge cells is enhanced; the recycling of the carbon source, the phosphorus source and the nitrogen source is considered, and the carbon source can be used for enhancing the nitrogen and phosphorus removal effect of the sewage after the carbon source is refluxed; the device has simple structure, convenient operation and non-harsh reaction conditions, and the adopted reaction raw materials are easy to obtain.
Description
Technical Field
The invention relates to the technical field of excess sludge treatment, in particular to anaerobic fermentation and nitrogen and phosphorus removal treatment technology.
Background
By the end of 2020, the total amount of domestic sewage and industrial sewage in cities and towns in China is about 826 hundred million tons, and the relative generated total amount of sludge is about 8382 million tons (sludge with 80% of water content). In a severe context, the excess sludge digestion pathway is not smooth and many sewage plants operate at high sludge concentrations (8-10g/L), resulting in sludge bulking. Meanwhile, sludge accumulation has multiple hazards to soil, air, underground water and the like in the ecological environment, and treatment of residual sludge is urgent. Under the background of emphasizing carbon neutralization and carbon peak, the sludge recycling technology has become an effective measure for reducing carbon emission. In addition, aiming at the problem that the ratio of the concentration of rbCOD and VFA to the concentration of N, P in the inlet water of the sewage plant is low (the ratio of C to N is low), the technology of fully excavating and preferentially utilizing the carbon source in the sewage plant is a domestic research hotspot in recent ten years.
Disclosure of Invention
The invention aims to provide a device and a method for strengthening anaerobic fermentation of excess sludge and strengthening nitrogen and phosphorus removal of sewage by fermentation liquor backflow.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for strengthening anaerobic fermentation of excess sludge and nitrogen and phosphorus removal of sewage by fermentation liquor backflow, which comprises the following steps:
(1) a pretreatment stage: adding an alkali solution and a complexing agent into the residual sludge obtained in the sewage treatment stage, and pre-stirring and mixing;
(2) an anaerobic fermentation stage;
(3) a nitrogen/phosphorus separation and recovery stage;
(4) and (5) a fermentation liquor recycling stage.
Further, the alkaline solution used in the pretreatment stage is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 2mol/L, and the pH of the residual sludge is adjusted to 10;
the complexing agent is sodium citrate, is green and nontoxic, and the ratio of the complexing agent to the sludge TSS is 0.05 g: 1g of TSS-0.2 g of complexing agent: 1g TSS.
Further, the complexing agent is industrial-grade sodium citrate (Na3C6H5O7 & 2H 2O).
Further, in the pretreatment stage, firstly, adding an alkali solution, stirring to adjust the pH value, then adding a complexing agent, stirring at the speed of 100r/min for 150min at the temperature of 25-35 ℃, and destroying sludge Extracellular Polymeric Substances (EPS).
Further, in the anaerobic fermentation stage, firstly adding an alkali solution into the sludge obtained in the step (1) to adjust the pH value, and then carrying out anaerobic stirring, fermentation and digestion;
and (2) adding the sodium hydroxide solution into the sludge obtained in the step (1) to adjust the pH value to 10, and then carrying out anaerobic stirring, fermentation and digestion for 5 days at the temperature of 35 ℃ and the stirring speed of 100 r/min.
Further, after the sludge treated in the anaerobic fermentation stage is subjected to centrifugal treatment, the supernatant enters the nitrogen/phosphorus separation and recovery stage for treatment; the centrifugation operation is centrifugation for 10min under the condition of 4000r/min, and phosphorus in a phospholipid bilayer of broken cells can also enter a supernatant in the centrifugation process.
Further, the nitrogen/phosphorus separation recovery stage is treated as follows:
when nitrogen and phosphorus are recovered simultaneously, a struvite method is adopted to generate struvite; when only phosphorus is recovered, crystal seeds containing calcium elements are added to generate hydroxyapatite crystals.
Further, the struvite process comprises: adding an alkali solution to adjust the pH of the system to 9-9.5, wherein the molar ratio n (Mg): adding magnesium chloride solution with the speed of 150-;
when only phosphorus is recovered, according to Ca 2+ ：PO 4 3- The molar ratio is 3.33, and the calcium-containing seed crystal is selected from calcium-containing bovine bone powder.
Further, the process of the fermentation liquor recycling stage comprises the following steps: performing solid-liquid separation on the sludge treated in the nitrogen/phosphorus separation and recovery stage, and performing filter pressing on the precipitate and drying to obtain a sludge nitrogen/phosphorus recovery product; the supernatant liquid flows back to the sewage treatment stage, so that the synchronous nitrogen and phosphorus removal system for activated sludge treatment works to provide a carbon source for the anoxic stage of nitrogen and phosphorus removal in sewage treatment, no additional carbon source is required to be added for sewage treatment, and the treatment load of nitrogen and phosphorus is not increased, so that the effluent quality of the nitrogen and phosphorus removal process for sewage treatment can be superior to the first-level A discharge standard.
The invention also provides a device for strengthening the method for the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the fermentation liquor by the reflux strengthening of the sewage, which comprises a pretreatment system, an anaerobic fermentation system, a nitrogen/phosphorus separation and recovery system and a fermentation liquor reflux system;
the pretreatment system comprises a pretreatment device provided with a first stirring device and a first pH meter, and the pretreatment device is also connected with a first lye tank and a complexing agent tank;
the anaerobic fermentation system comprises an anaerobic fermentation device, the anaerobic fermentation device is connected with the pretreatment device through a first pump, and an anaerobic fermentation cavity, a second stirring device, a second pH meter, an exhaust hose, a liquid seal device, a heating device, a constant temperature controller and a water bath heat insulation layer are arranged on the anaerobic fermentation device;
the nitrogen/phosphorus separation and recovery system comprises a nitrogen/phosphorus recovery reaction device, the nitrogen/phosphorus recovery reaction device is connected with the anaerobic fermentation device through a second pump, a third pH meter, a TP detection device and a TN detection device are arranged on the nitrogen/phosphorus recovery reaction device, and the nitrogen/phosphorus recovery reaction device is also connected with a second medicament tank;
the fermentation liquor reflux system comprises a fermentation liquor standing device, a filter press and a fourth pump; the fermentation liquor standing device is connected with the nitrogen/phosphorus recovery reaction device through a third pump; the inlet of the fourth pump is connected to the fermentation liquor standing device, and the outlet of the fourth pump is connected to the sewage treatment stage; the filter press is provided with two inlet branches, one inlet branch is connected to the nitrogen/phosphorus recovery reaction device, and the other inlet branch is connected to the fermentation liquor standing device.
Further, a centrifugal machine is arranged between the second pump and the nitrogen/phosphorus recovery reaction device.
Further, the second stirring device, the second pH meter, the exhaust hose and the liquid sealing device are connected to the anaerobic fermentation cavity, the water bath heat insulation layer is arranged on the periphery of the anaerobic fermentation cavity, and the heating device and the constant temperature controller are connected to the water bath heat insulation layer; the side wall of the anaerobic fermentation cavity is also connected with a water outlet and a sampling port, and the water outlet and the sampling port penetrate through the water bath heat insulation layer and extend out of the anaerobic fermentation device;
the nitrogen/phosphorus recovery reaction device is connected with the water outlet of the anaerobic fermentation device through a second pump,
and the outlet of the filter press is connected with a drying device.
The advantages of the invention include:
(1) the method is characterized in that the excess sludge anaerobic fermentation is used for producing Volatile Fatty Acid (VFA), the VFA is an efficient sludge disposal mode, alkali in the pretreatment section is favorable for breaking the wall and dissolving the cell of the sludge, sodium citrate/citric acid is favorable for destroying EPS of the sludge, the dissolution amount of intracellular organic matters and nutrient substances of sludge microorganisms is improved, and the biodegradability of a dissolved matter is improved, and the sodium citrate/citric acid and the dissolved matter have a synergistic effect, so that the sludge has a biochemical substrate with higher concentration for anaerobic fermentation, the sludge anaerobic fermentation can be enhanced by utilizing NaOH to couple the sodium citrate/citric acid for pretreatment, and the VFA yield of unit sludge is further improved;
(2) the pH is adjusted only at the beginning of pretreatment and anaerobic fermentation, so that the consumption of NaOH is reduced;
(3) the sludge anaerobic fermentation system is used for low-temperature anaerobic fermentation at 35 ℃ for 5d, and the VFA concentration in the fermentation liquid (digestive juice) can reach 13000 mg. COD. L < -1 >; the ratio of acetic acid in the digestive juice VFA of the sludge anaerobic fermentation system is 70.64% -90.82%, and the acetic acid is a carbon source which is easy to be utilized by sewage organisms;
(4) the main biological nitrogen and phosphorus removal process for refluxing the VFA-containing sludge fermentation liquor to the sewage treatment stage can provide a carbon source for the nitrogen and phosphorus removal microorganisms, solve the problem of low C/N ratio and strengthen the nitrogen and phosphorus removal efficiency of the microorganisms, and is a technology with better application prospect.
(5) The device simple structure, convenient operation, economy is strong, not only can provide the necessary carbon source of biological nitrogen and phosphorus removal in the sewage treatment stage through mud resourceization, stabilization, strengthens biochemical section nitrogen and phosphorus removal effect, reduces the carbon emission among the sewage treatment, simultaneously, can also retrieve the nutritive substance who contains nitrogen, phosphorus from mud.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention:
FIG. 1 is a schematic view of the overall structure of the apparatus of the present invention;
FIG. 2 is a schematic top view of the pretreatment and anaerobic fermentation systems;
FIG. 3 is a schematic top view of the nitrogen/phosphorus separation and recovery system and the fermentation broth reflux system;
FIG. 4 is a schematic sectional view of an anaerobic fermentation apparatus;
FIG. 5 is a statistical chart of VFA production during the anaerobic fermentation stage of the present invention;
FIG. 6 is a statistical chart of SCOD production during the anaerobic fermentation stage of the present invention;
FIG. 7 is a statistical graph of phosphate production during the anaerobic fermentation stage of the present invention;
FIG. 8 is a statistical chart of ammonia nitrogen production during anaerobic fermentation stage.
The device comprises a pretreatment system 1, a first stirring device 11, a first pH meter 12, a pretreatment device 13, a first lye tank 14, a complexing agent tank 15, an anaerobic fermentation system 2, an anaerobic fermentation device 21, an anaerobic fermentation cavity 211, a second stirring device 212, a second pH meter 213, an exhaust hose 214, a liquid seal device connecting position 215, a heating device 216, a thermostatic controller 217, a water bath heat-insulating layer 218, a water outlet 219, a sampling port 220, a first pump 22, a nitrogen/phosphorus separation and recovery system 3, a nitrogen/phosphorus recovery reaction device 31, a third pH meter 311, a TP detection device 312, a TN detection device 313, a second pump 32, a centrifuge 33, a second reagent tank 34, a fermentation liquor backflow system 4, a fermentation liquor device 41, a filter press 42, a fourth pump 43 and a third pump 44.
Detailed Description
The present invention will be described in detail with reference to the drawings and specific embodiments, which are illustrative of the present invention and are not to be construed as limiting the present invention.
Example one
A device for strengthening the method of excess sludge anaerobic fermentation and fermentation liquor backflow strengthening sewage nitrogen and phosphorus removal comprises a pretreatment system 1, an anaerobic fermentation system 2, a nitrogen/phosphorus separation and recovery system 3 and a fermentation liquor backflow system 4;
the pretreatment system 1 comprises a pretreatment device 13 provided with a first stirring device 11 and a first pH meter 12, wherein the pretreatment device 13 is also connected with a first lye tank 14 and a complexing agent tank 15; the pretreatment device 13 is a pretreatment tank, the first lye tank 14 contains 2mol/L sodium hydroxide solution, and the complexing agent tank 15 contains industrial sodium citrate or citric acid.
The anaerobic fermentation system 2 comprises an anaerobic fermentation device 21, the anaerobic fermentation device 21 is connected with the pretreatment device 13 through a first pump 22, and an anaerobic fermentation cavity 211, a second stirring device 212, a second pH meter 213, an exhaust hose 214, a liquid seal device, a heating device 216, a constant temperature controller 217 and a water bath heat insulation layer 218 are arranged on the anaerobic fermentation device 21;
the second stirring device 212, the second pH meter 213, the exhaust hose 214 and the liquid seal device are connected to the anaerobic fermentation cavity 211, the water bath heat insulation layer 218 is arranged on the periphery of the anaerobic fermentation cavity 211, and the heating device 216 and the constant temperature controller 217 are connected to the water bath heat insulation layer 218; the side wall of the anaerobic fermentation cavity 211 is further connected with a water outlet 219 and a sampling port 220, and the water outlet 219 and the sampling port 220 penetrate through the water bath insulating layer 218 and extend out of the anaerobic fermentation device 21. The liquid seal device can be a structure that a U-shaped pipe is sealed in a liquid mode or a communicating pipe is inserted below the liquid level of the liquid device, and the liquid seal device is connected to the liquid seal device connecting position 215.
The nitrogen/phosphorus separation and recovery system 3 comprises a nitrogen/phosphorus recovery reaction device 31, the nitrogen/phosphorus recovery reaction device 31 is connected to a water outlet 220 of the anaerobic fermentation device 21 through a second pump 32, a centrifuge 33 is arranged between the second pump 32 and the nitrogen/phosphorus recovery reaction device 31, the nitrogen/phosphorus recovery reaction device 31 is provided with a third pH meter 311, a TP detection device 312 and a TN detection device 313, and the nitrogen/phosphorus recovery reaction device 31 is further connected with a second medicament tank 34; the second agent tank contains a magnesium chloride solution or a calcium salt precipitant. The calcium salt precipitant is calcium-rich bovine bone powder.
The fermentation liquid reflux system 4 comprises a fermentation liquid standing device 41, a filter press 42 and a fourth pump 43; the fermentation liquid standing device 41 is connected with the nitrogen/phosphorus recovery reaction device 31 through a third pump 44; the inlet of the fourth pump 43 is connected to the fermentation liquid standing device 41, and the outlet of the fourth pump 43 is connected to the sewage treatment stage; the filter press 42 is provided with two inlet branches, one inlet branch is connected to the nitrogen/phosphorus recovery reaction device 31, and the other inlet branch is connected to the fermentation liquor standing device 41.
And the outlet of the filter press is connected with a drying device.
The working process of the device comprises the following steps:
(1) pumping the sludge in a primary sedimentation tank and a secondary sedimentation tank of a sewage treatment stage into a pretreatment tank through a pump to measure Total Suspended Solids (TSS) of the sludge, adding NaOH with the concentration of 2mol/L into the sludge, starting stirring, and adjusting the pH to be 10;
② adding industrial grade sodium citrate (Na) according to the TSS value and the proportion of 0.2g complexing agent/1 g TSS 3 C 6 H 5 O 7 ·2H 2 O), stirring at 100r/min for 150min continuously to destroy sludge Extracellular Polymeric Substances (EPS).
(2) Anaerobic fermentation (anaerobic digestion) is carried out on the pretreated sludge, the pH value of the sludge is firstly adjusted to 10 before the anaerobic fermentation is started, oxygen in an anaerobic fermentation device is removed by adopting nitrogen, and the sludge is fermented and digested for 5 days in a medium temperature water bath at the temperature of 35 ℃, and the stirring speed is 100 r/min.
(3) The nitrogen and phosphorus separation and recovery stage comprises the following steps:
after the anaerobic fermentation reaction is finished, pumping the mixture after the anaerobic fermentation into a centrifuge 33 by a second pump 32, centrifuging the centrifuge 33 for 10min under the condition of 4000r/min, and feeding the supernatant into a sludge nitrogen/phosphorus recovery reaction device.
Firstly, when simultaneously recovering nitrogen/phosphorus, adopting a struvite method, firstly adding a sodium hydroxide solution with the concentration of 1mol/L, adding the sodium hydroxide solution under the monitoring of a third pH meter until the pH value of a reaction system is 9-9.5,under the indication of TP detection device, through containing MgCl 2 ·6H 2 Reagent tank 2 for O is charged with a quantity of magnesium chloride solution to a molar ratio n (Mg): n (P) ═ 2, and the reaction was carried out sufficiently by allowing the system to react for 30min under the conditions of a stirring rate of 150 and 180 rmp.
② when only phosphorus is recovered, according to Ca 2+ :PO 4 3- Adding bovine bone meal rich in calcium as seed crystal at a molar ratio of 3.33, recovering phosphorus in the sludge digestion solution, and generating Hydroxyapatite (HAP) crystals.
(4) A digestive juice recycling stage, comprising the following steps:
firstly, after the reaction is finished, the fermentation liquor enters a fermentation liquor standing device and stands for 2 to 3 hours;
secondly, the supernatant is refluxed through a fourth pump 43, and the supernatant containing a large amount of VFA is reused in a sewage treatment section, so as to strengthen the nitrogen and phosphorus removal of the sewage;
thirdly, the sediment at the lower layer is subjected to filter pressing through a filter press 42, the filter-pressed solid enters a drying device, and sludge nitrogen/phosphorus recovery is obtained after drying, the main component of the sludge nitrogen/phosphorus recovery is struvite when a struvite method is adopted, and the main component of the recovery is hydroxyapatite when calcium salt precipitator is adopted.
Example two
This example is a small scale experiment using a sample of excess sludge from a Guangzhou municipal sewage plant. The sewage plant adopts anaerobic-anoxic-aerobic A 2 Treating sewage by the/O process, storing the residual sludge sample in a refrigerator at 4 ℃, concentrating for 24 hours under static and heavy force, and pouring out supernatant for later use. The initial characteristics of the excess sludge sample were pH 6.87; the Total COD (TCOD) is 27010 +/-2310 mg/L; soluble COD (SCOD) is 18 +/-2 mg/L; the total suspended solid content (TSS) is 40605 plus or minus 250 mg/L; the Volatile Suspended Solid (VSS) is 12500 +/-100 mg/L; ammonia Nitrogen (NH) 4 + -N) is 4.15 mg/L; soluble total phosphorus (TP, in PO) 4 - Note) was 20.3 mg/L.
3 parallel experiments are set, and each parallel experiment treats the residual sludge sample according to the following steps:
(1) taking 6 brown bottles with the capacity of 1000mL, and respectively adding 900mL of residual sludge;
(2) setting 1 brown bottle, adding NaOH at the initial stage of reaction to adjust pH to 10, and using as blank group, numbering 1 group;
setting 1 brown bottle and adding sodium citrate as cationic complexing agent in the amount of 0.2 g/1 g TSS as reference group, and numbering 2 groups;
setting 4 brown bottles, adding NaOH at the initial stage of the reaction to adjust the pH value to 10, respectively making 4 experimental groups, respectively adding sodium citrate as a cation complexing agent, wherein the sodium citrate is respectively 0.05g of sodium citrate/1 g of TSS, 0.10g of sodium citrate/1 g of TSS, 0.15g of sodium citrate/1 g of TSS and 0.2g of sodium citrate/1 g of TSS, and respectively and rapidly mixing after adding, wherein the number of the groups is 3-6;
(3) the water sample of the content of the brown bottle was pretreated by continuous mixing under a water bath shaker using a rotary shaking mode. The experiment is carried out at the room temperature of 35 ℃, the rotating speed is 100r/min, and the stirring is continuously carried out for 150 min;
(4) anaerobic fermentation experiments were performed in the 1000mL brown bottles described above, and the pH of the pretreated sludge of groups 1, 3-6 was readjusted to 10. Cleaning oxygen in the bottle with nitrogen, sealing to form an anaerobic environment, fermenting and digesting the brown bottle in a water bath vibrator at 35 ℃ and 100r/min for 6d, and sampling every 24h for detection;
(5) centrifuging the sample taken each time in the step (4) for 10min at 4000r/min, and then using the supernatant (fermentation liquor) for VFA, pH, SCOD, soluble protein, soluble polysaccharide, ammonia nitrogen and phosphate radical index determination;
detecting VFA in the fermentation liquid by gas chromatography, and performing domestic gas chromatograph (GC7980, FID, FPD); detecting the pH value by using a pH meter; SCOD is detected by a Hash rapid digestion spectrophotometry method; protein is detected by adopting a Coomassie brilliant blue G-250 staining method; detecting the polysaccharide by adopting a phenol-sulfuric acid method; detecting ammonia nitrogen by adopting a Nashin reagent photometry; the phosphate radical adopts a molybdenum-antimony anti-spectrophotometry method; TSS and VSS are detected by a burning weight reduction method.
The results show that group 6 sludge, pretreated with NaOH to an initial pH of 10 and coupled with sodium citrate at a dose of 0.2g sodium citrate/1 g TSS, has the best cell disruption effect, its SCOD, soluble proteins and sodium citrateThe peak concentrations of soluble polysaccharides were 2059.5mg/L, 114.86mg/L and 190.97 mg/L, respectively, indicating that a large amount of intracellular carbon source was released. In the fermentation process, VFA mainly contains acetic acid, and the highest concentration is 13712.35 mg. cod. L -1 Group 6 showed a 119.8% increase in VFA production over group 1 and 474.7% increase over group 2.
PO4 in group 6 fermentation broths 3- -P and NH 4 + The content of-N is higher and is respectively 71.82 mg/L and 320.75mg/L, MgCl is added 2 ·6H 2 O, the adding amount is 1.51mmol/L, the reaction is carried out for 30min under the condition that the stirring speed is 150-180rmp, struvite sediment is generated, the sediment at the lower layer is subjected to filter pressing through a filter press, the filtrate is reserved, the filtered solid enters a drying device, and the solid matter with the main component of struvite is obtained after drying.
The effective volume of the AAO sewage treatment reaction tank is 96L, and the AAO sewage treatment reaction tank is anaerobic: hypoxia: the volume ratio of aerobic sections is 1:3:5, the inflow rate is 256L/d, the hydraulic retention time is 9 hours, the sludge age is 15 days, the inflow water quality of the AAO sewage treatment section is CODcr 167mg/L, TN 27.73mg/L and TP 3.69mg/L, and according to the proportion of adding 121.5mL of the filtrate into every 1L of sewage to be treated, the filtrate containing a large amount of VFA is reused in the AAO sewage treatment reaction tank, so that the COD of the sewage can reach 372 mg/L.
The effluent of the AAO sewage treatment reaction tank enters a sedimentation tank for solid-liquid separation, the effective volume of the sedimentation tank is 43L, the sedimentation time is 4 hours, and the effluent quality is as follows: CODcr is 15.9mg/L, TN is 10.14mg/L, TP is 0.34mg/L, and the effluent quality is superior to the national first-class A sewage discharge standard.
The advantages of the invention include: the effect of anaerobic sludge acid production is improved by low-cost pretreatment of sodium citrate coupled with sodium hydroxide, and the main component of the produced VFA is acetic acid which is easy to be utilized by water treatment microorganisms, and in addition, the release of nitrogen and phosphorus in sludge cells is enhanced. The invention gives consideration to the recovery of carbon source, phosphorus source and nitrogen source, and does not consume the carbon source in the digestive fluid as much as possible in the process of recovering nitrogen and phosphorus, and the carbon source can be used for strengthening the effect of nitrogen and phosphorus removal of sewage after refluxing; the device has simple structure, convenient operation and non-harsh reaction conditions, and the adopted reaction raw materials are easy to obtain. The method has the advantages of low recovery cost, realization of resource utilization of the sludge, increase of carbon source recycling of the whole water treatment process, promotion of sludge resource utilization in sewage plants and reduction of carbon emission.
The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained herein by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; meanwhile, for a person skilled in the art, according to the embodiments of the present invention, there may be variations in the specific implementation manners and application ranges, and in summary, the content of the present description should not be construed as a limitation to the present invention.
Claims (10)
1. A method for strengthening anaerobic fermentation of excess sludge and strengthening nitrogen and phosphorus removal of sewage by fermentation liquor backflow is characterized by comprising the following steps:
the process comprises the following steps:
(1) a pretreatment stage: adding an alkali solution and a complexing agent into the residual sludge obtained in the sewage treatment stage, and pre-stirring and mixing;
(2) an anaerobic fermentation stage;
(3) a nitrogen/phosphorus separation and recovery stage;
(4) and (5) a fermentation liquor recycling stage.
2. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 1, wherein:
the alkaline solution used in the pretreatment stage is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 2mol/L, and the pH of the residual sludge is adjusted to 10;
the complexing agent is sodium citrate, and the ratio of the complexing agent to the sludge TSS is 0.05 g: 1g of TSS-0.2 g of complexing agent: 1g TSS;
and in the pretreatment stage, firstly adding an alkali solution, stirring to adjust the pH, and then adding a complexing agent, stirring at the speed of 100r/min for 150min at the temperature of 25-35 ℃.
3. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 1, wherein:
in the anaerobic fermentation stage, firstly adding an alkali solution into the sludge obtained in the step (1) to adjust the pH value, and then carrying out anaerobic stirring, fermentation and digestion;
and (2) adding the sodium hydroxide solution into the sludge obtained in the step (1) to adjust the pH value to 10, and then carrying out anaerobic stirring, fermentation and digestion for 5 days at the temperature of 35 ℃ and the stirring speed of 100 r/min.
4. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 1, wherein:
after the sludge treated in the anaerobic fermentation stage is subjected to centrifugal treatment, the supernatant enters the nitrogen/phosphorus separation and recovery stage for treatment; the centrifugation operation is centrifugation for 10min under the condition of 4000 r/min.
5. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 1, wherein:
the nitrogen/phosphorus separation and recovery stage is treated as follows:
when nitrogen and phosphorus are recovered simultaneously, a struvite method is adopted to generate struvite; when only phosphorus is recovered, crystal seeds containing calcium elements are added to generate hydroxyapatite crystals.
6. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 4, wherein:
the struvite method comprises the following steps: adding an alkali solution to adjust the pH of the system to 9-9.5, wherein the molar ratio n (Mg): n (P) is 2, adding magnesium chloride solution, stirring and reacting for 30min at the speed of 150-180 rmp;
when only phosphorus is recovered, according to Ca 2+ ：PO 4 3- A seed crystal containing calcium element at a molar ratio of 3.33, containingThe calcium crystal seed is selected from calcium-containing Os bovis Seu Bubali powder.
7. The method for enhancing the anaerobic fermentation of the excess sludge and the nitrogen and phosphorus removal of the sewage by the reflux of the fermentation broth as claimed in claim 1, wherein:
the process of the fermentation liquor recycling stage comprises the following steps: and (3) performing solid-liquid separation on the sludge treated in the nitrogen/phosphorus separation and recovery stage, performing filter pressing on the precipitate, drying to obtain a sludge nitrogen/phosphorus recovery product, and refluxing the supernatant to the sewage treatment stage.
8. The device for the method for strengthening the anaerobic fermentation of the excess sludge and the reflux enhancement of the sewage nitrogen and phosphorus removal of the fermentation liquor in the claim 1 is characterized in that:
comprises a pretreatment system, an anaerobic fermentation system, a nitrogen/phosphorus separation and recovery system and a fermentation liquor reflux system;
the pretreatment system comprises a pretreatment device provided with a first stirring device and a first pH meter, and the pretreatment device is also connected with a first lye tank and a complexing agent tank;
the anaerobic fermentation system comprises an anaerobic fermentation device, the anaerobic fermentation device is connected with the pretreatment device through a first pump, and an anaerobic fermentation cavity, a second stirring device, a second pH meter, an exhaust hose, a liquid seal device, a heating device, a constant temperature controller and a water bath heat insulation layer are arranged on the anaerobic fermentation device;
the nitrogen/phosphorus separation and recovery system comprises a nitrogen/phosphorus recovery reaction device, the nitrogen/phosphorus recovery reaction device is connected to the anaerobic fermentation device through a second pump, a third pH meter, a TP detection device and a TN detection device are arranged on the nitrogen/phosphorus recovery reaction device, and the nitrogen/phosphorus recovery reaction device is also connected with a second medicament tank;
the fermentation liquor reflux system comprises a fermentation liquor standing device, a filter press and a fourth pump; the fermentation liquor standing device is connected with the nitrogen/phosphorus recovery reaction device through a third pump; the inlet of the fourth pump is connected to the fermentation liquor standing device, and the outlet of the fourth pump is connected to the sewage treatment stage; and the filter press is provided with two inlet branches, one inlet branch is connected to the nitrogen/phosphorus recovery reaction device, and the other inlet branch is connected to the fermentation liquor standing device.
9. The apparatus for enhancing the anaerobic fermentation of excess sludge and the enhanced nitrogen and phosphorus removal method of sewage by fermentation broth reflux as claimed in claim 8, wherein:
and a centrifugal machine is arranged between the second pump and the nitrogen/phosphorus recovery reaction device.
10. The apparatus for enhancing the anaerobic fermentation of excess sludge and the enhanced nitrogen and phosphorus removal method of sewage by fermentation broth reflux as claimed in claim 8, wherein:
the second stirring device, the second pH meter, the exhaust hose and the liquid seal device are connected to the anaerobic fermentation cavity, the water bath heat insulation layer is arranged on the periphery of the anaerobic fermentation cavity, and the heating device and the constant temperature controller are connected to the water bath heat insulation layer; the side wall of the anaerobic fermentation cavity is also connected with a water outlet and a sampling port, and the water outlet and the sampling port penetrate through the water bath heat insulation layer and extend out of the anaerobic fermentation device;
the nitrogen/phosphorus recovery reaction device is connected with the water outlet of the anaerobic fermentation device through a second pump,
and the outlet of the filter press is connected with a drying device.
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