CN113461284A - Municipal sludge treatment method for nitrate-enhanced pyrohydrolysis - Google Patents
Municipal sludge treatment method for nitrate-enhanced pyrohydrolysis Download PDFInfo
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- 239000010802 sludge Substances 0.000 title claims abstract description 130
- 229910002651 NO3 Inorganic materials 0.000 title claims abstract description 52
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 49
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 43
- 239000000706 filtrate Substances 0.000 claims abstract description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000009283 thermal hydrolysis Methods 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 238000000855 fermentation Methods 0.000 claims abstract description 16
- 238000009264 composting Methods 0.000 claims abstract description 15
- 239000003814 drug Substances 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 239000003895 organic fertilizer Substances 0.000 claims abstract description 4
- 239000010865 sewage Substances 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 11
- 230000018044 dehydration Effects 0.000 claims description 6
- 238000006297 dehydration reaction Methods 0.000 claims description 6
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 claims description 5
- 239000002351 wastewater Substances 0.000 claims description 5
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 claims description 4
- JVMRPSJZNHXORP-UHFFFAOYSA-N ON=O.ON=O.ON=O.N Chemical compound ON=O.ON=O.ON=O.N JVMRPSJZNHXORP-UHFFFAOYSA-N 0.000 claims description 3
- 238000001179 sorption measurement Methods 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000009388 chemical precipitation Methods 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000005342 ion exchange Methods 0.000 claims description 2
- 239000013043 chemical agent Substances 0.000 claims 1
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 230000035484 reaction time Effects 0.000 claims 1
- 239000003337 fertilizer Substances 0.000 abstract description 5
- 238000000354 decomposition reaction Methods 0.000 abstract description 4
- 244000005700 microbiome Species 0.000 abstract description 2
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 230000015556 catabolic process Effects 0.000 abstract 1
- 238000006731 degradation reaction Methods 0.000 abstract 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 20
- 229910052757 nitrogen Inorganic materials 0.000 description 11
- 230000029087 digestion Effects 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 235000015097 nutrients Nutrition 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 230000006641 stabilisation Effects 0.000 description 3
- 238000011105 stabilization Methods 0.000 description 3
- 239000003344 environmental pollutant Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Inorganic materials [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000004021 humic acid Substances 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- GQPLMRYTRLFLPF-UHFFFAOYSA-N nitrous oxide Inorganic materials [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 1
- -1 organic matters Substances 0.000 description 1
- 244000052769 pathogen Species 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Inorganic materials [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Substances [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000009279 wet oxidation reaction Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/004—Sludge detoxification
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
- C02F11/04—Anaerobic treatment; Production of methane by such processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5281—Installations for water purification using chemical agents
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F2001/007—Processes including a sedimentation step
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
- C02F2001/425—Treatment of water, waste water, or sewage by ion-exchange using cation exchangers
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F2101/30—Organic compounds
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Abstract
The invention relates to a municipal sludge treatment method of nitrate-enhanced thermal hydrolysis, which comprises the steps of mechanically dehydrating municipal sludge, adding a nitrate medicament into the dehydrated sludge, performing thermal hydrolysis treatment on the obtained mud-water mixture to generate a mud-water mixture, further mechanically dehydrating the mud-water mixture to obtain dehydrated sludge and filtrate, removing heavy metals from the filtrate, mixing the filtrate with the dehydrated sludge to obtain a mixture, performing anaerobic fermentation or aerobic composting treatment on the mixture, and finally obtaining a heavy metal-removed municipal sludge organic fertilizer. According to the invention, by adding nitrate medicaments into the sludge pyrohydrolysis process, the decomposition of microorganisms and degradation-resistant organic matters in the sludge are promoted, the anaerobic fermentation efficiency is improved, heavy metals in the sludge can be removed in a synergistic manner, and the content of heavy metals in the treated sludge is remarkably reduced, so that the sludge after subsequent anaerobic fermentation or composting can be used as a fertilizer for land utilization, and the heavy metal pollution risk of the sludge land utilization is eliminated.
Description
Technical Field
The invention belongs to the technical field of sludge treatment and comprehensive resource utilization, and particularly relates to a municipal sludge treatment method for nitrate-enhanced pyrohydrolysis.
Background
At present, the biological treatment process is widely applied to municipal sewage treatment, and a large amount of biological sludge is generated in the process that pollutants such as organic matters, nitrogen, phosphorus and the like in the sewage are absorbed and utilized by organisms. Every 1 million tons of sewage are treated, 5 to 10 tons of sludge with water content of about 80 percent are produced every day. According to the report, the annual output of sludge in cities and towns in China reaches 3750 ten thousand tons as of 2017, along with the continuous improvement of a system for collecting and treating sewage in cities and towns in China, the treatment amount of municipal sewage is increased year by year, and the production amount of sludge is also increased synchronously. The sludge is enriched with about 5 percent of organic matters, 30 to 45 percent of nitrogen and 85 to 95 percent of phosphorus in the sewage, and if the sludge can be recycled by adopting proper technology, the sludge becomes an important soil nutrient source. However, the sludge is enriched with more than 80% of toxic and harmful substances such as heavy metals, organic pollutants and the like in the sewage, and the toxic and harmful substances may be accumulated in the soil and absorbed by plants in the land utilization process, thereby causing environmental and health risks.
At present, the sludge treatment and disposal modes comprise landfill, incineration, composting, anaerobic digestion and the like. During stabilization treatment processes of composting, anaerobic digestion and the like, the water content of the sludge is greatly reduced, a large number of pathogens are inactivated to form a large number of humic acid substances, plant nutrient elements such as N, P with high content are reserved, and the sludge has good land utilization potential. The amount of sludge treated by land utilization in the united states and the european union accounts for about 50% of the total sludge production, and is the main sludge treatment technology. However, the heavy metal content of sludge in China has large regional variation and is generally higher than that of the United states and European Union. The high content of heavy metals in the sludge becomes one of the key problems for limiting the land utilization of the sludge.
Chinese patent application No. CN202010747292.0 discloses a treatment method for efficiently and stably treating municipal sludge, which comprises the steps of treating dewatered sludge in a pyrohydrolysis tank and then carrying out aerobic composting on the treated sludge. Chinese patent application No. CN202010450567.4 discloses an energy recovery and fertilizer preparation process based on sludge pyrohydrolysis split-phase digestion, which carries out secondary pyrohydrolysis treatment on dewatered sludge, and the water content of mud cakes obtained by mechanically dewatering the sludge can be reduced to below 60 percent after the secondary pyrohydrolysis treatment. Chinese patent application No. CN201910102645.9 discloses a system and a process for treating excess sludge by combining a thermal hydrolysis-catalytic wet oxidation technology. The pyrohydrolysis step in the method disclosed in the above document is mainly used as pretreatment of anaerobic digestion and composting of municipal sludge for improving the efficiency of subsequent biochemical treatment, however, the removal rate of heavy metals in the sludge treated by the above method is not ideal.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a municipal sludge treatment method for nitrate-enhanced pyrohydrolysis. The method can remove heavy metal pollutants in the sludge, meet the land utilization standard, and simultaneously fully utilize organic matters, nitrogen, phosphorus and other nutrient elements in the sludge to realize resource utilization of the sludge. According to the municipal sludge treatment method, the nitrate medicament is added in the sludge pyrohydrolysis process, so that the decomposition of microorganisms and the decomposition of refractory organic matters in the sludge are promoted, the anaerobic fermentation efficiency is improved, meanwhile, the heavy metals in the sludge can be removed in a synergistic manner, the content of the heavy metals in the treated sludge is obviously reduced, and the sludge after subsequent anaerobic fermentation or composting can be used as a fertilizer for land utilization.
The technical scheme adopted by the invention is as follows:
a municipal sludge treatment method for nitrate-enhanced pyrohydrolysis comprises the following steps:
(1) mechanical dehydration: mechanically dehydrating municipal sludge generated in the municipal sewage treatment process to obtain dehydrated sludge;
(2) adding nitrate medicaments: adding a nitrate medicament into the dewatered sludge obtained in the step (1), and fully stirring for mixing reaction to obtain a mud-water mixture;
(3) thermal hydrolysis treatment: carrying out thermal hydrolysis treatment on the mud-water mixture obtained in the step (2);
(4) mechanical dehydration: mechanically dehydrating the mud-water mixture subjected to the thermal hydrolysis treatment in the step (3) to respectively obtain dehydrated sludge and filtrate;
(5) removing heavy metals from the filtrate: removing heavy metals in the filtrate obtained in the step (4);
(6) anaerobic fermentation/composting:
and (4) mixing the filtrate from which the heavy metals are removed in the step (5) with the dewatered sludge from the step (4) to obtain a mixture, and performing anaerobic fermentation or aerobic composting treatment to obtain the municipal sludge organic fertilizer from which the heavy metals are removed.
In the step (1), the water content of the dewatered sludge is 75-85%.
In the step (2), the nitrate medicament is soluble nitrate solution, nitrite solution or waste water containing nitrate and nitrite.
In the step (2), the concentration of nitrate nitrogen or nitrite nitrogen in the nitrate chemical is more than 5 mg/L.
In the step (2), the volume ratio of the nitrate medicament to the dewatered sludge is 1-10: 1.
In the step (2), the time for stirring, mixing and reacting the nitrate medicament and the dewatered sludge is less than 30 min.
In the step (3), the temperature of the thermal hydrolysis treatment is 100-170 ℃, and the time of the thermal hydrolysis treatment is 30-60 min.
In the step (4), the water content of the dewatered sludge is 85% -90%.
In the step (5), the heavy metal removal method is any one of chemical precipitation and ion exchange adsorption.
In the step (6), when anaerobic fermentation is carried out, completely mixing the dewatered sludge in the step (4) with the filtrate from which heavy metals are removed in the step (5) for one time;
when aerobic composting is carried out, mixing the dewatered sludge in the step (4) with the filtrate from which heavy metals are removed in the step (5) for multiple times; the volume ratio of the dewatered sludge to the filtrate is not less than 10:1 during each mixing.
The invention has the beneficial effects that:
according to the municipal sludge treatment method for nitrate-enhanced thermal hydrolysis, municipal sludge is mechanically dehydrated, then nitrate chemicals are added into the dehydrated sludge, and the obtained mud-water mixture is subjected to thermal hydrolysis, so that the predecomposition effect of a thermal hydrolysis process on the sludge can be remarkably improved, heavy metals in the sludge can be effectively leached, and the heavy metal pollution risk of sludge land utilization is eliminated. Specifically, by adding nitrate chemicals, on one hand, the decomposition efficiency of the conventional thermal hydrolysis treatment on the nondegradable organic matters such as flocs, cell walls and the like in the sludge is improved, the anaerobic fermentation rate and the methane gas production rate of the sludge after the thermal hydrolysis treatment are both obviously increased, the anaerobic fermentation treatment efficiency and the energy recovery rate are improved, and the investment and the operation cost of anaerobic fermentation are reduced. On the other hand, the addition of nitrate medicaments can improve the dissolution and release of heavy metals in the sludge in the thermal hydrolysis treatment process, thereby creating favorable conditions for the removal of the heavy metals in the sludge. In addition, heavy metals in the sludge after the thermal hydrolysis treatment are converted into a residue state with lower environmental risk, and the process can have a remarkable effect on the stabilization of the heavy metals in the sludge. The sludge from which the heavy metals are removed is used as a raw material to prepare related fertilizer products, the risk of secondary pollution of the heavy metals is obviously reduced in the using process, and the fertilizer has wider market application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a process flow diagram of the municipal sludge treatment method of nitrate enhanced pyrohydrolysis according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Example 1
The embodiment provides a municipal sludge treatment method for nitrate-enhanced pyrohydrolysis, which specifically comprises the following steps as shown in fig. 1:
(1) mechanical dehydration:
mechanically dehydrating excess sludge generated in the municipal sewage treatment process to obtain dehydrated sludge with the water content of 75-85%;
(2) adding nitrate medicaments:
adding a certain amount of NaNO into the dewatered sludge obtained in the step (1)3Solution, NaNO3Nitrate Nitrogen (NO) in solution3 --N) concentration of 40mg/L, NaNO3The volume ratio of the solution to the dewatered sludge is 3:1, and the solution and the dewatered sludge are fully stirred, mixed and reacted for 15min to obtain a mud-water mixture;
(3) thermal hydrolysis:
carrying out thermal hydrolysis treatment on the mud-water mixture obtained in the step (2) at 170 ℃ for 30 min;
(4) mechanical dehydration:
mechanically dehydrating the mud-water mixture subjected to the thermal hydrolysis treatment in the step (3) to obtain dehydrated sludge and filtrate with the water content of 85-90%;
(5) removing heavy metals from the filtrate:
enabling the filtrate obtained in the step (4) to pass through a D113 type weak acid ion exchange resin adsorption column, and adsorbing and removing dissolved heavy metals in the filtrate;
(6) anaerobic fermentation/composting:
and (3) completely mixing the dewatered sludge produced in the step (4) with the filtrate obtained after the heavy metal removal in the step (5), carrying out anaerobic fermentation treatment on the mixture, and dewatering the fermented residual solid to obtain the municipal sludge organic fertilizer without the heavy metal.
Example 2
This example provides a method for treating municipal sludge by nitrate-enhanced pyrohydrolysis, which differs from example 1 only in that: in the step (2), the nitrate chemical is KNO3The solution was otherwise the same as in example 1.
Example 3
The present example provides a municipal sludge treatment method of nitrate-enhanced pyrohydrolysis, and the difference between the present example and example 1 is only that: in the step (2), the nitrate chemical is KNO2Solution, KNO2Nitrite Nitrogen (NO) in solution2 --N) concentration of 40mg/L, KNO2The volume ratio of the solution to the dewatered sludge was 3:1, and the rest was the same as in example 1.
Example 4
The present example provides a municipal sludge treatment method of nitrate enhanced pyrohydrolysis, and the difference between the present example and example 3 is only that: in the step (2), the nitrate medicament is NaNO2The solution was otherwise identical to that of example 3.
Example 5
The present example provides a municipal sludge treatment method of nitrate-enhanced pyrohydrolysis, and the difference between the present example and example 1 is only that: in the step (2), the nitrate-based chemical is Nitrate (NO)3 -) And Nitrite (NO)2 -) Wastewater of (4), nitrate Nitrogen (NO) in wastewater3 --N) and nitrous Nitrogen (NO)2 -The sum of the concentrations of-N) was 40mg/L, the volume ratio of wastewater to dewatered sludge was 3:1, and the rest was exactly the same as in example 1.
Example 6
The present example provides a municipal sludge treatment method of nitrate-enhanced pyrohydrolysis, and the difference between the present example and example 1 is only that: in the step (6), the dewatered sludge generated in the step (4) and the filtrate after heavy metal removal in the step (5) are mixed again and then are subjected to aerobic composting treatment, the filtrate is added into the dewatered sludge for multiple times, and the adding amount of each time is as follows: the volume ratio of sludge to filtrate was 10:1, and the rest was exactly the same as in example 1.
Experimental example 1
The method of the embodiment 1 of the invention is adopted to treat the sludge generated by a municipal sewage treatment plant in a certain city, and the content of each heavy metal before and after the sludge treatment is specifically shown in the table 1.
TABLE 1 heavy metal content in sludge before and after treatment
As shown in Table 1, after the sludge is treated by the method of the embodiment 1 of the invention, the removal rate of Zn in the sludge reaches 89%, thereby showing that the method of the invention can obviously reduce the heavy metal content in the sludge. In addition, heavy metals in the sludge after the thermal hydrolysis treatment are converted into a residue state with lower environmental risk, and the process can have a remarkable effect on the stabilization of the heavy metals in the sludge.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. The municipal sludge treatment method for nitrate-enhanced pyrohydrolysis is characterized by comprising the following steps of:
(1) mechanical dehydration: mechanically dehydrating municipal sludge generated in the municipal sewage treatment process to obtain dehydrated sludge;
(2) adding nitrate medicaments: adding a nitrate medicament into the dewatered sludge obtained in the step (1), and fully stirring for mixing reaction to obtain a mud-water mixture;
(3) thermal hydrolysis treatment: carrying out thermal hydrolysis treatment on the mud-water mixture obtained in the step (2);
(4) mechanical dehydration: mechanically dehydrating the mud-water mixture subjected to the thermal hydrolysis treatment in the step (3) to respectively obtain dehydrated sludge and filtrate;
(5) removing heavy metals from the filtrate: removing heavy metals in the filtrate obtained in the step (4);
(6) anaerobic fermentation/composting:
and (4) mixing the filtrate from which the heavy metals are removed in the step (5) with the dewatered sludge from the step (4) to obtain a mixture, and performing anaerobic fermentation or aerobic composting treatment to obtain the municipal sludge organic fertilizer from which the heavy metals are removed.
2. The method for municipal sludge treatment with nitrate-enhanced pyrohydrolysis according to claim 1, wherein in step (1), the dewatered sludge has a water content of 75-85%.
3. The method for municipal sludge treatment with nitrate-enhanced pyrohydrolysis according to claim 1, wherein in step (2), the nitrate-based agent is a soluble nitrate solution, a nitrite solution or wastewater containing nitrate and nitrite.
4. The method for municipal sludge treatment with nitrate-enhanced pyrohydrolysis according to claim 1, wherein in step (2), the nitrate-based chemical has a concentration of nitrate nitrogen or nitrite nitrogen >5 mg/L.
5. The method for treating municipal sludge for nitrate-enhanced pyrohydrolysis according to claim 1, wherein in the step (2), the volume ratio of the nitrate-based chemical to the dewatered sludge is 1-10: 1.
6. The method for municipal sludge treatment with nitrate-enhanced pyrohydrolysis according to claim 1, wherein in step (2), the nitrate-based chemical agent and the dewatered sludge are stirred and mixed for a reaction time of less than 30 min.
7. The method for treating municipal sludge for nitrate-enhanced pyrohydrolysis according to claim 1, wherein in the step (3), the temperature of the pyrohydrolysis treatment is 100 ℃ to 170 ℃ and the time of the pyrohydrolysis treatment is 30min to 60 min.
8. The method for municipal sludge treatment with nitrate-enhanced pyrohydrolysis according to claim 1, wherein in step (4), the dewatered sludge has a water content of 85% to 90%.
9. The municipal sludge treatment method for nitrate-enhanced pyrohydrolysis according to claim 1, wherein in the step (5), the heavy metal removal is performed by any one of chemical precipitation and ion exchange adsorption.
10. The municipal sludge treatment method for nitrate-enhanced pyrohydrolysis according to claim 1, wherein in the step (6), the dewatered sludge of the step (4) is mixed with the filtrate from which heavy metals are removed of the step (5) all at once when anaerobic fermentation is performed;
when aerobic composting is carried out, mixing the dewatered sludge in the step (4) with the filtrate from which heavy metals are removed in the step (5) for multiple times; the volume ratio of the dewatered sludge to the filtrate is not less than 10:1 during each mixing.
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