CN113526806B

CN113526806B - Sludge treatment method

Info

Publication number: CN113526806B
Application number: CN202010294975.5A
Authority: CN
Inventors: 肖冬杰; 李方志; 何沙
Original assignee: Hunan Junxin Environmental Co ltd
Current assignee: Hunan Junxin Environmental Co ltd
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2022-03-11
Anticipated expiration: 2040-04-15
Also published as: CN113526806A

Abstract

The invention discloses a sludge treatment method, which comprises the following steps: according to different organic matter contents, the sludge is divided into high organic matter sludge with the organic matter mass content of more than 43 percent and low organic matter sludge with the organic matter mass content of less than or equal to 43 percent; and treating the high and low organic sludge by adopting different treatment modes according to different mass ratios of the high and low organic sludge to finish the treatment of the sludge. The sludge treatment method has the advantages of simple process, convenient operation, low cost, no secondary pollution and the like, can effectively solve the problem of low carbon-nitrogen ratio wastewater generated by anaerobic treatment, can effectively take the whole heat energy of the system into consideration, ensures that the process is suitable for sludge of different organic matters on the basis of not increasing the existing anaerobic process chain, particularly can realize resource utilization and reduction when the proportion of the low organic matter sludge is low, and has high use value and good application prospect.

Description

Sludge treatment method

Technical Field

The invention relates to a sludge treatment method.

Background

With the increase of domestic sewage systems, the amount of excess sludge generated by municipal sewage treatment is increasing day by day, so how to effectively treat the excess sludge becomes an important problem in the field of environmental protection. At present, the main methods for treating the part of sludge are as follows: the processes of thermal hydrolysis and anaerobic treatment, synergetic household garbage incineration, aerobic composting and the like are gradually the preferred processes due to low treatment cost and methane generation, but the popularization and the operation of the anaerobic process are always disturbed by the anaerobic process or the generated low carbon nitrogen ratio wastewater in the process. In view of the existing problems, the measures taken include: adding external high-carbon-nitrogen-ratio wastewater (leachate of a domestic garbage incineration power plant), adding a carbon source (methanol or glucose), adopting an anaerobic ammonia oxidation process and the like, wherein the periphery of most anaerobic projects is not provided with a domestic garbage incineration plant; the cost is increased sharply by adding a carbon source; no mature matching factories exist in China in the anaerobic ammonia oxidation process. The problems that large-area popularization of anaerobic treatment cannot be achieved, high water treatment technical cost cannot be paid, treatment efficiency is low and the like are caused by the reasons, and the problems are not favorable for project popularization and long-period stable operation of the thermal hydrolysis and anaerobic treatment process. In addition, the low-carbon-nitrogen-ratio wastewater generated by the pyrohydrolysis and anaerobic system cannot be effectively treated in the existing process under the condition of no additional carbon source or using a special water treatment process. In addition, in the prior art, the sludge is not considered to be subjected to high-low organic matter sludge layering and synergistic treatment according to the difference of organic matter content, and the heat energy requirement of the high-low organic matter sludge in an anaerobic system cannot be balanced, so that the effective treatment of the sludge cannot be realized at low cost and high efficiency.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a sludge treatment method which is simple in process, convenient to operate, low in cost and free of secondary pollution.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for treating sludge comprises the following steps:

s1, according to different organic matter contents, dividing the sludge into high organic matter sludge with the organic matter mass content more than 43% and low organic matter sludge with the organic matter mass content less than or equal to 43%;

s2, when the mass ratio of the high organic matter sludge to the low organic matter sludge is less than 3: 1, treating the high organic matter sludge and the low organic matter sludge in the step S1 in a mode; when the mass ratio of the high organic sludge to the low organic sludge is more than or equal to 3: 1, treating the high organic sludge and the low organic sludge in the step S1 in a two-pair mode;

the method comprises the following steps:

(1) preheating low organic matter sludge, carrying out anaerobic digestion treatment on the preheated low organic matter sludge, and carrying out solid-liquid separation to obtain a first mud cake and low carbon-nitrogen ratio wastewater; carrying out thermal hydrolysis treatment on the high organic matter sludge, cooling, and carrying out solid-liquid separation to obtain a second mud cake and high carbon-nitrogen ratio wastewater;

(2) mixing the low-carbon-nitrogen-ratio wastewater obtained in the step (1) with the high-carbon-nitrogen-ratio wastewater to ensure that the carbon-nitrogen ratio of the mixed wastewater is not lower than 3.5: 1, and performing subsequent water treatment to finish the treatment of sludge;

the second mode includes the following steps:

(a) carrying out thermal hydrolysis treatment on the high organic matter sludge, and respectively cooling the obtained thermal hydrolysis products to 60-70 ℃ and 45-57 ℃, wherein the obtained thermal hydrolysis products respectively correspond to the mud-water mixture A and the mud-water mixture B; carrying out anaerobic digestion treatment on the mud-water mixture A, and carrying out solid-liquid separation to obtain a first mud cake and first low-carbon-nitrogen-ratio wastewater; carrying out solid-liquid separation on the mud-water mixture B to obtain a second mud cake and first high-carbon-nitrogen-ratio wastewater; carrying out thermal hydrolysis treatment on the low organic matter sludge, cooling, and carrying out solid-liquid separation to obtain a third mud cake and second high carbon-nitrogen ratio wastewater; mixing the second high-carbon-nitrogen-ratio wastewater with the second mud cake for anaerobic digestion treatment, and performing solid-liquid separation to obtain a fourth mud cake and second low-carbon-nitrogen-ratio wastewater;

(b) mixing the first low carbon-nitrogen ratio wastewater, the second low carbon-nitrogen ratio wastewater and the first high carbon-nitrogen ratio wastewater in the step (a), wherein the carbon-nitrogen ratio of the mixed wastewater is not lower than 3.5: 1, and performing subsequent water treatment to complete the treatment of sludge.

In the step (1), the preheating of the low organic matter sludge is to heat the low organic matter sludge to 60-99 ℃; the heat source adopted in the preheating process of the low organic matter sludge is thermal hydrolysis flash steam generated in thermal hydrolysis treatment or boiler steam obtained by heating methane generated in anaerobic digestion treatment; adding water in the preheating process of the low organic matter sludge to control the solid content of the low organic matter sludge to be 6-7%; the water added in the regulation and control process of the solid content of the low organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the anaerobic digestion treatment conditions in the treatment process of the low organic matter sludge are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled to be 4-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the low organic matter sludge; the solid content of the first mud cake is 30-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; in the wastewater with the low carbon-nitrogen ratio, the COD content is 800 mg/L-3000 mg/L, and the ammonia nitrogen content is 800 mg/L-2500 mg/L.

In the step (1), the thermal hydrolysis treatment of the high organic matter sludge is to preheat the high organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then to continuously heat the high organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating methane generated in the anaerobic digestion treatment; adding water in the preheating process of the high organic matter sludge to control the solid content of the high organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the high organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, improve the temperature of the reverse osmosis treatment produced water to 50-80 ℃, and then continuously reduce the temperature to 45 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the high organic matter sludge; the solid content of the second mud cake is 30-50%; the COD content in the wastewater with high carbon-nitrogen ratio is 12000 mg/L-40000 mg/L, and the ammonia nitrogen content is 500 mg/L-3000 mg/L.

In the above sludge treatment method, further improvement is that in the step (1), the first mud cake further comprises the following treatment: drying the first mud cake until the solid content is more than or equal to 42%; the dried sludge is used as covering soil of a landfill or soil for gardens; the temperature of the drying treatment is 65-150 ℃; the drying treatment mode is at least one of hollow blade drying, belt drying, thin layer drying and electrolytic drying; in the drying treatment process, when biogas is required for drying, at least part or all of biogas generated in the anaerobic digestion process is used; the second mud cake is used for adjusting the solid content of the system in the anaerobic digestion treatment process;

in the step (2), the carbon-nitrogen ratio of the mixed wastewater is 4: 1; the subsequent water treatment comprises the following steps of sequentially treating the mixed wastewater: two-stage AO treatment, ultrafiltration membrane treatment, nanofiltration treatment and/or reverse osmosis treatment.

In the step (a), the thermal hydrolysis treatment of the high organic matter sludge is to preheat the high organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then to continuously heat the high organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating methane generated in the anaerobic digestion treatment; adding water in the preheating process of the high organic matter sludge to control the solid content of the high organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the high organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, improve the temperature of the reverse osmosis treatment produced water to 50-80 ℃, and then continuously reduce the temperature to 60-70 ℃ and 45-57 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode.

In the above sludge treatment method, further improvement is provided, in the step (a), the anaerobic digestion conditions in the treatment process of the sludge-water mixture a are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled at 6-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the mud-water mixture A; the solid content of the first mud cake is 35-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; the COD content in the first wastewater with low carbon-nitrogen ratio is 800-3000 mg/L, and the ammonia nitrogen content is 800-2500 mg/L.

In the step (a), a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the sludge-water mixture B; the solid content of the second mud cake is 35-50%; the COD content in the first high carbon-nitrogen ratio wastewater is 12000 mg/L-40000 mg/L, and the ammonia nitrogen content is 500 mg/L-3000 mg/L.

In the step (a), the thermal hydrolysis treatment of the low organic matter sludge is to preheat the low organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then to continuously heat the low organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating methane generated in the anaerobic digestion treatment; adding water in the preheating process of the low organic matter sludge to control the solid content of the low organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the low organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, increase the temperature of the reverse osmosis treatment produced water to 55-80 ℃, and then continuously reduce the temperature to 30-6 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the low organic matter sludge; the solid content of the third mud cake is 35-50%; the COD content in the second high carbon-nitrogen ratio wastewater is 8000mg/L to 40000mg/L, and the ammonia nitrogen content is 500mg/L to 3000 mg/L.

In the above sludge treatment method, further improvement is provided, in the step (a), the anaerobic digestion conditions in the treatment process of the second high carbon-nitrogen ratio wastewater and the second sludge cake are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled at 6-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the second high-carbon-nitrogen-ratio wastewater and the second mud cake; the solid content of the fourth mud cake is 35-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; the COD content in the second low carbon-nitrogen ratio wastewater is 800mg/L to 3000mg/L, and the ammonia nitrogen content is 800mg/L to 2500 mg/L.

In the above sludge treatment method, further improvement is that in the step (a), the first mud cake, the third mud cake and the fourth mud cake further comprise the following treatment: mixing the first mud cake, the third mud cake and the fourth mud cake, and drying until the solid content is more than or equal to 42%; the dried sludge is used as covering soil of a landfill or soil for gardens; the temperature of the drying treatment is 65-150 ℃; the drying treatment mode is at least one of hollow blade drying, belt drying, thin layer drying and electrolytic drying; in the drying treatment process, when biogas is required for drying, at least part or all of biogas generated in the anaerobic digestion process is used;

in the step (b), the carbon-nitrogen ratio of the mixed wastewater is 4: 1; the subsequent water treatment comprises the following steps of sequentially treating the mixed wastewater: two-stage AO treatment, ultrafiltration membrane treatment, nanofiltration treatment and/or reverse osmosis treatment.

Compared with the prior art, the invention has the advantages that:

the invention provides a sludge treatment method, which comprises the steps of classifying high-low organic sludge in municipal sludge, treating the organic sludge with different contents according to different process routes (partially or completely carrying out pyrohydrolysis and digestion), improving the utilization rate of a pyrohydrolysis heat source and the efficiency of a digestion process, further directly surpassing anaerobic digestion of high-carbon-nitrogen-ratio wastewater (partially or completely) generated by pyrohydrolysis for supplementing a carbon source for rear-end water treatment, improving the carbon-nitrogen ratio of the wastewater, meeting the water inlet requirement of a common water treatment process, ensuring stable operation of an integral process chain of a sludge anaerobic digestion process under the condition of not using external carbon source addition or special water treatment, and reducing the operation cost and the difficulty of water treatment control; meanwhile, internal heat energy generated in the technological process is utilized in a stepped mode, for example, a low-grade heat source is recycled in the thermal hydrolysis stage, and the heat utilization efficiency of the system is improved. The sludge treatment method has the advantages of simple process, convenient operation, low cost, no secondary pollution and the like, can effectively solve the problem of low carbon-nitrogen ratio wastewater generated by anaerobic treatment, can effectively take the whole heat energy of the system into consideration, ensures that the process is suitable for sludge of different organic matters on the basis of not increasing the existing anaerobic process chain, particularly can realize resource utilization and reduction when the proportion of the low organic matter sludge is low, and has high use value and good application prospect.

Detailed Description

The invention is further described below with reference to specific preferred embodiments, without thereby limiting the scope of protection of the invention.

Example 1

A method for treating excess sludge obtained from municipal sewage treatment plants comprises the following steps:

and (I) respectively storing the low organic matter sludge and the high organic matter sludge on the boundary of the high organic matter sludge and the low organic matter sludge with the organic matter mass content of 43 percent. In the embodiment, the sludge treatment amount is 500t/d, wherein the amount of the low organic sludge with the organic matter mass content of 32-43% is 240t, and the amount of the high organic sludge with the organic matter mass content higher than 43% is 260 t.

Secondly, the low organic matter sludge in the first step is subjected to a primary heating procedure to increase the temperature of the sludge to 70 ℃, wherein the heating mode is direct heating; the heat source is thermal hydrolysis flash steam and boiler steam (in this embodiment, the boiler steam is used for direct heating in the initial stage until the thermal hydrolysis flash steam comes out). During the heating, a certain amount of Reverse Osmosis (RO) produced water (heated) was added so that the solid content of the sludge-water mixture at the outlet of the process section was 6.5%.

And (III) pumping the heated mud-water mixture in the step two into an intermediate mud storage tank, and then pumping into an anaerobic digestion system for anaerobic digestion treatment. Setting the running temperature of the anaerobic digestion system to be 55 +/-0.5 ℃, the retention time to be 21 days and controlling the solid content to be 10 percent.

(IV) the sludge subjected to anaerobic digestion enters a rear-end sludge storage tank in an overflow mode, PAM (the addition amount of the PAM is 3 per mill of the absolute dry matter amount of the sludge) is added, filter pressing is carried out by using a plate-and-frame filter press, solid-liquid separation is carried out, and a first sludge cake and low-carbon-nitrogen-ratio wastewater are obtained, wherein the solid content of the sludge (the first sludge cake) is maintained at 40 +/-1%, and the low-carbon-nitrogen-ratio wastewater is 750m³The COD content is 2400mg/L, and the ammonia nitrogen content is 2000 mg/L.

And (V) the sludge (first sludge cake) obtained after the solid-liquid separation in the step four enters a plate frame sludge bin and then enters a belt type drier for drying. Setting the drying temperature to be 120 ℃, and drying until the solid content of the sludge is 60%. The drying heat source is methane generated by anaerobic digestion.

And (sixthly), taking the sludge (with the solid content of 60%) dried in the step five as covering soil of a landfill.

And (seventhly), enabling the sewage (the wastewater with the low carbon-nitrogen ratio) obtained after the solid-liquid separation in the step four to enter a high-temperature pool, and enabling the sewage to enter a low-temperature pool after passing through a heat exchanger for later use.

And (eighthly), after the high organic matter sludge in the step one is subjected to a primary heating procedure, raising the temperature to 85 ℃, and synchronously adding water generated by RO treatment until the solid content is 16%. The heat source of the primary heating process is thermal hydrolysis flash steam (in this embodiment, steam from a boiler is used for direct heating in the initial stage until thermal hydrolysis flash steam comes out).

And (ninthly), pumping the high organic matter muddy water mixture subjected to the primary heating procedure in the step eight into a pyrohydrolysis system for pyrohydrolysis treatment, wherein the pyrohydrolysis temperature is set to be 165 ℃ and the pyrohydrolysis time is set to be 30 minutes. The heat source used in the thermal hydrolysis treatment is boiler steam obtained by heating biogas generated in the anaerobic digestion treatment.

And (ten) cooling the mud-water mixture subjected to thermal hydrolysis and pressure relief in the step nine, wherein the solid content is controlled to be 12.5%. And (3) firstly exchanging heat between the decompressed mud-water mixture and RO produced water, increasing the temperature of RO to 75 ℃, and then entering a forced heat exchange area to reduce the temperature of the mud-water mixture after thermal hydrolysis to 45 ℃. (forced heat transfer zone is in tubular heat exchanger + air cooled form, hot water from tubular heat exchange outlet is partially added as hot water to the second step, so lost circulating water is supplemented by fresh water.)

Eleventh, performing solid-liquid separation on the mud-water mixture cooled to 45 ℃ in the tenth step by adopting a plate-and-frame filter press, controlling the solid content of sludge (second sludge cake) to be 40%, and simultaneously obtaining wastewater with high carbon-nitrogen ratio, wherein the volume of the wastewater with high carbon-nitrogen ratio is 286m³The COD content is 24000mg/L and the ammonia nitrogen content is 2000 mg/L. And (3) putting the sludge (second mud cake) with the solid content of 40% obtained after solid-liquid separation in the step into the intermediate sludge storage tank in the step three in a continuous flow mode, and being used for improving the solid content of the sludge in the tank and ensuring the solid content of anaerobic digestion.

And (twelfth) mixing the high-carbon-nitrogen-ratio wastewater obtained in the eleventh step with the low-carbon-nitrogen-ratio wastewater obtained in the fourth step according to the volume ratio of 1:2.7, so that the carbon-nitrogen ratio in the obtained mixed solution is 4: 1.

And (thirteen) the wastewater mixed in the step twelve enters two-stage AO + external ultrafiltration membrane + nanofiltration + reverse osmosis treatment to complete the treatment of sludge. Wherein the concentration of the two-stage AO sludge is controlled to be 15g/L, the internal reflux ratio is 10: 1, the external reflux ratio is 20: 1, and the oxygen concentration of the O tank is 2.5-4 mg/L.

Example 2

A method for treating sludge comprises the following steps:

and (I) respectively storing the low organic matter sludge and the high organic matter sludge on the boundary of the high organic matter sludge and the low organic matter sludge with the organic matter mass content of 43 percent. In the embodiment, the sludge treatment amount is 400t/d, wherein the amount of the low organic sludge with the organic matter mass content of 30-35% is 100t, and the amount of the high organic sludge with the organic matter mass content higher than 43% is 300 t.

And (II) the sludge with high organic matters is subjected to a primary heating process to increase the temperature of the sludge to 90 ℃, wherein the heating mode is direct heating, and the heat source is thermal hydrolysis flash steam (in the embodiment, steam of a boiler is used for direct heating in the initial stage until the thermal hydrolysis flash steam comes out). During the heating process, certain amounts of RO produced water (heated) and fresh hot water (heated) are added, so that the solid content of the mud-water mixture at the outlet of the process section is 16%.

And (III) pumping the heated mud-water mixture in the step two into a pyrohydrolysis system for pyrohydrolysis treatment, wherein the pyrohydrolysis temperature is set to be 135 ℃, and the time is set to be 30 minutes.

And (IV) after the thermal hydrolysis and pressure relief in the step III, controlling the solid content to be 12.5 percent. And (3) preferentially exchanging heat between the decompressed mud-water mixture and RO produced water, and raising the temperature of the RO produced water to 75 ℃. And then entering a forced circulation heat exchange area, and dividing the mud-water mixture into two paths, wherein the temperature of one path is reduced to 60 ℃, and the temperature of the other path is reduced to 55 ℃. The amount of the original sludge reduced to 55 ℃ is 160 tons (in the present invention, the mass ratio of the original high organic matter sludge reduced to 55 ℃ and 60 ℃ is adjusted according to the carbon-nitrogen ratio required for the subsequent biochemical treatment, in this embodiment, the mass ratio of the original high organic matter sludge reduced to 55 ℃ and 60 ℃ is 160: 140). (forced heat transfer zone is in tubular heat exchanger + air cooled form, hot water from tubular heat exchange outlet is partially added as fresh hot water to the second step, so lost circulating water is supplemented by fresh water.)

And fifthly, pumping the mud-water mixture (the mud-water mixture A) with the temperature of 60 ℃ in the fourth step into an anaerobic digestion system for anaerobic digestion treatment after passing through a mud storage tank. Setting the running temperature of the anaerobic digestion system to be 55 +/-0.5 ℃, the retention time to be 20 days and controlling the solid content to be 10 percent.

And (VI) the sludge subjected to anaerobic digestion in the step five enters a rear-end sludge storage tank in an overflow mode, PAM (PAM addition amount is 3 per mill of absolute dry matter mass of the sludge) is added, a plate-and-frame filter press is used for filter pressing and solid-liquid separation, the solid content of the sludge (first mud cake) in plate-and-frame discharging is maintained at 40%, the separated sewage (first low-carbon-nitrogen-ratio wastewater) enters a rear-end biochemical system, and the part of sewage (first low-carbon-nitrogen-ratio wastewater) contains 2200mg/L of COD and 1900mg/L of ammonia nitrogen.

And (seventhly), enabling the sewage (the wastewater with the first low carbon-nitrogen ratio) obtained after solid-liquid separation in the step six to enter a high-temperature pool, and then enter a low-temperature pool after passing through a heat exchanger, and then enter a water treatment system for later use.

And (eighthly), sludge (the first sludge cake with the solid content of 40%) obtained after solid-liquid separation in the step six enters the plate frame sludge bin for later use.

And (ninth), carrying out plate-and-frame filter pressing on the mud-water mixture (mud-water mixture B) with the temperature of 55 ℃ obtained in the fourth step to obtain high carbon-nitrogen ratio wastewater (first high carbon-nitrogen ratio wastewater) and sludge (second sludge cake) with the solid content of 40 percent. In the wastewater with high carbon-nitrogen ratio, the COD content is 23000mg/L, and the ammonia nitrogen content is 1700 mg/L.

And (ten) the sludge (second sludge cake) with the solid content of 40% obtained in the ninth step is retained for standby.

And eleventh, after the low organic matter sludge in the first step is subjected to a primary heating procedure, the temperature is raised to 90 ℃, a heat source of the primary heating procedure is thermal hydrolysis flash steam, and RO water production (after heating) is synchronously added until the solid content of the low organic matter sludge is 16%.

And (twelfth) pumping the low organic matter muddy water mixture subjected to the primary heating procedure in the eleventh step into a pyrohydrolysis system for pyrohydrolysis treatment, wherein the pyrohydrolysis temperature is set to be 160 ℃, and the pyrohydrolysis time is set to be 30 minutes. The heat source used in the thermal hydrolysis treatment is boiler steam obtained by heating biogas generated in the anaerobic digestion treatment.

And (thirteen) cooling the mud-water mixture subjected to the thermal hydrolysis and pressure relief in the step twelve, wherein the solid content is controlled to be 12.5%. And (3) preferentially exchanging heat between the decompressed mud-water mixture and RO produced water, increasing the temperature of RO to 75 ℃, and then entering a forced heat exchange area to reduce the temperature of the mud-water mixture after thermal hydrolysis to 55 ℃.

And (fourteen) performing solid-liquid separation on the sludge-water mixture subjected to temperature reduction in the step thirteen by using a plate-and-frame filter press, controlling the solid content of sludge (third sludge cake) to be 50%, and feeding the separated sludge (third sludge cake) into a plate-and-frame sludge bin for later use. In the step, the COD content in the high carbon-nitrogen ratio wastewater (second high carbon-nitrogen ratio wastewater) after solid-liquid separation is 12000mg/L, and the ammonia nitrogen content is 1200 mg/L.

And (fifteen) mixing the wastewater with the high carbon-nitrogen ratio (second wastewater with the high carbon-nitrogen ratio) obtained after the solid-liquid separation in the step fourteen with the sludge (second sludge cake) in the step fourteen, adding 56 tons of heated RO produced water, raising the temperature to 56 ℃ by utilizing a direct steam heating mode, and putting the mixture into a digestion tank for anaerobic digestion treatment. Setting the running temperature of the anaerobic digestion system to be 55 +/-0.5 ℃, the retention time to be 20 days and controlling the solid content to be 10 percent. The purpose of adding the wastewater with high carbon-nitrogen ratio (the wastewater with the second high carbon-nitrogen ratio) in the step is to dilute the sludge with high solid content in the front so that the solid content meets the requirement of digestion; meanwhile, the COD of the wastewater with high carbon-nitrogen ratio (the wastewater with the second high carbon-nitrogen ratio) is reduced through anaerobic fermentation.

Sixthly, the sludge subjected to anaerobic digestion in the step fifteen enters a rear-end sludge storage tank in an overflow mode, PAM (PAM addition amount is 3 per mill of absolute dry matter amount of the sludge) is added, a plate-and-frame filter press is used for filter pressing and solid-liquid separation, the solid content of the sludge (fourth mud cake) in plate-and-frame discharging is maintained at 40%, the separated sewage (second low-carbon-nitrogen-ratio wastewater) enters a rear-end biochemical system, the content of the COD in the part of the sewage (second low-carbon-nitrogen-ratio wastewater) is 2200mg/L, and the content of the ammonia nitrogen is 2000 mg/L.

Seventhly, enabling the sewage obtained after solid-liquid separation in the sixteenth step to enter a high-temperature pool, then entering a low-temperature pool after passing through a heat exchanger, and then entering a water treatment system for later use.

Eighteen, the sludge (the fourth sludge cake with the solid content of 40%) obtained after the solid-liquid separation in the sixteenth step enters a plate frame sludge bin, is mixed with the sludge (the first sludge cake) in the eighth step and the sludge (the third sludge cake) in the fourteenth step, and then enters a belt type drier for drying until the solid content is 60%. The drying temperature was set at 120 ℃. The dried heat source is methane generated by anaerobic digestion. The dried sludge is treated as covering soil for landfill or soil for garden.

And (nineteenth) taking the high-carbon-nitrogen-ratio wastewater (first high-carbon-nitrogen-ratio wastewater) obtained in the ninth step as a supplementary carbon source, allowing the high-carbon-nitrogen-ratio wastewater to enter a rear-end water treatment system, mixing the high-carbon-nitrogen-ratio wastewater (first low-carbon-nitrogen-ratio wastewater) obtained in the sixth step with the low-carbon-nitrogen-ratio wastewater (second low-carbon-nitrogen-ratio wastewater) obtained in the sixteenth step to enable the carbon-nitrogen ratio in the mixed wastewater to be 4: 1, and allowing the mixed wastewater to enter two stages of AO + external ultrafiltration membrane + nanofiltration + reverse osmosis treatment to complete sludge treatment. Wherein the concentration of the two-stage AO sludge is controlled to be 16g/L, the internal reflux ratio is 10: 1, the external reflux ratio is 20: 1, and the oxygen concentration of the O tank is 2.5-4 mg/L.

In the embodiment 1 and the embodiment 2 of the invention, the municipal sludge is classified into high and low organic sludge, the organic sludge with different contents is treated (partially or completely pyrolyzed and digested) according to different process routes, the utilization rate of a pyrolysis heat source and the efficiency of a digestion process are improved, and then the high carbon-nitrogen ratio wastewater (partially or completely) generated by the pyrohydrolysis directly exceeds anaerobic digestion and is used for supplementing a carbon source for rear-end water treatment, so that the carbon-nitrogen ratio of the wastewater is improved, the water inlet requirement of a common water treatment process is met, the stable operation of the whole process chain of the anaerobic sludge digestion process can be ensured under the condition of not using external carbon source addition or special water treatment, and the operation cost and the water treatment control difficulty are reduced; meanwhile, internal heat energy generated in the technological process is utilized in a stepped mode, for example, a low-grade heat source is recycled in the thermal hydrolysis stage, and the heat utilization efficiency of the system is improved. The sludge treatment method has the advantages of simple process, convenient operation, low cost, no secondary pollution and the like, can effectively solve the problem of low carbon-nitrogen ratio wastewater generated by anaerobic treatment, can effectively take the whole heat energy of the system into consideration, ensures that the process is suitable for sludge of different organic matters on the basis of not increasing the existing anaerobic process chain, particularly can realize resource utilization and reduction when the proportion of the low organic matter sludge is low, and has high use value and good application prospect.

The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.

Claims

1. The sludge treatment method is characterized by comprising the following steps:

the method comprises the following steps:

the second mode includes the following steps:

2. The method for treating sludge according to claim 1, wherein in the step (1), the preheating of the low organic matter sludge is to heat the low organic matter sludge to 60-99 ℃; the heat source adopted in the preheating process of the low organic matter sludge is thermal hydrolysis flash steam generated in thermal hydrolysis treatment or boiler steam obtained by heating methane generated in anaerobic digestion treatment; adding water in the preheating process of the low organic matter sludge to control the solid content of the low organic matter sludge to be 6-7%; the water added in the regulation and control process of the solid content of the low organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the anaerobic digestion treatment conditions in the treatment process of the low organic matter sludge are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled to be 4-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the low organic matter sludge; the solid content of the first mud cake is 30-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; in the wastewater with the low carbon-nitrogen ratio, the COD content is 800 mg/L-3000 mg/L, and the ammonia nitrogen content is 800 mg/L-2500 mg/L.

3. The sludge treatment method according to claim 2, wherein in the step (1), the thermal hydrolysis treatment of the high organic matter sludge comprises preheating the high organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then continuously heating the high organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating biogas generated in the anaerobic digestion treatment; adding water in the preheating process of the high organic matter sludge to control the solid content of the high organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the high organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, improve the temperature of the reverse osmosis treatment produced water to 50-80 ℃, and then continuously reduce the temperature to 45 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the high organic matter sludge; the solid content of the second mud cake is 30-50%; the COD content in the wastewater with high carbon-nitrogen ratio is 12000 mg/L-40000 mg/L, and the ammonia nitrogen content is 500 mg/L-3000 mg/L.

4. The method for treating sludge according to any one of claims 1 to 3, wherein in the step (1), the first sludge cake further comprises the following treatment: drying the first mud cake until the solid content is more than or equal to 42%; the dried sludge is used as covering soil of a landfill or soil for gardens; the temperature of the drying treatment is 65-150 ℃; the drying treatment mode is at least one of hollow blade drying, belt drying, thin layer drying and electrolytic drying; in the drying treatment process, when biogas is required for drying, at least part or all of biogas generated in the anaerobic digestion process is used; the second mud cake is used for adjusting the solid content of the system in the anaerobic digestion treatment process;

5. The method for treating sludge according to claim 1, wherein in the step (a), the thermal hydrolysis treatment of the high organic matter sludge comprises preheating the high organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then continuously heating the high organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating biogas generated in the anaerobic digestion treatment; adding water in the preheating process of the high organic matter sludge to control the solid content of the high organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the high organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, improve the temperature of the reverse osmosis treatment produced water to 50-80 ℃, and then continuously reduce the temperature to 60-70 ℃ and 45-57 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode.

6. The method for treating sludge according to claim 5, wherein in the step (a), the conditions of anaerobic digestion treatment in the treatment process of the sludge-water mixture A are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled at 6-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the mud-water mixture A; the solid content of the first mud cake is 35-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; the COD content in the first wastewater with low carbon-nitrogen ratio is 800-3000 mg/L, and the ammonia nitrogen content is 800-2500 mg/L.

7. The method for treating sludge according to claim 5, wherein in the step (a), a plate-and-frame filter press is used for solid-liquid separation in the treatment process of the sludge-water mixture B; the solid content of the second mud cake is 35-50%; the COD content in the first high carbon-nitrogen ratio wastewater is 12000 mg/L-40000 mg/L, and the ammonia nitrogen content is 500 mg/L-3000 mg/L.

8. The method for treating sludge according to claim 5, wherein in the step (a), the thermal hydrolysis treatment of the low organic matter sludge comprises the steps of preheating the low organic matter sludge to 55-99 ℃ by using thermal hydrolysis flash steam, and then continuously heating the low organic matter sludge to 100-185 ℃ by using boiler steam obtained by heating the methane generated in the anaerobic digestion treatment; adding water in the preheating process of the low organic matter sludge to control the solid content of the low organic matter sludge to be 12-18%; the water added in the regulation and control process of the solid content of the low organic matter sludge is hot water at a tubular heat exchange outlet and/or reverse osmosis treatment water after heat exchange with a thermal hydrolysis treatment product; the time of the thermal hydrolysis treatment is 20min to 60 min; the temperature reduction is to exchange heat between the mud-water mixture obtained after the thermal hydrolysis treatment and the reverse osmosis treatment produced water, increase the temperature of the reverse osmosis treatment produced water to 55-80 ℃, and then continuously reduce the temperature to 30-6 ℃ by utilizing a tubular heat exchanger and/or an air cooling mode; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the low organic matter sludge; the solid content of the third mud cake is 35-50%; the COD content in the second high carbon-nitrogen ratio wastewater is 8000mg/L to 40000mg/L, and the ammonia nitrogen content is 500mg/L to 3000 mg/L.

9. The method for treating sludge according to claim 5, wherein in the step (a), the conditions of anaerobic digestion treatment in the treatment process of the second high carbon-nitrogen ratio wastewater and the second sludge cake are as follows: the operation temperature is 33-60 ℃, the retention time is 15-30 days, and the solid content is controlled at 6-10%; a plate-and-frame filter press is adopted for solid-liquid separation in the treatment process of the second high-carbon-nitrogen-ratio wastewater and the second mud cake; the solid content of the fourth mud cake is 35-50%; the solid-liquid separation process also comprises the step of adding a flocculating agent into the sludge, wherein the adding amount of the flocculating agent is 1-5 per mill of the absolute dry mass of the sludge; the flocculant is PAM; the COD content in the second low carbon-nitrogen ratio wastewater is 800mg/L to 3000mg/L, and the ammonia nitrogen content is 800mg/L to 2500 mg/L.

10. The method for treating sludge according to any one of claims 5 to 9, wherein in the step (a), the first mud cake, the third mud cake and the fourth mud cake further comprise the following treatment: mixing the first mud cake, the third mud cake and the fourth mud cake, and drying until the solid content is more than or equal to 42%; the dried sludge is used as covering soil of a landfill or soil for gardens; the temperature of the drying treatment is 65-150 ℃; the drying treatment mode is at least one of hollow blade drying, belt drying, thin layer drying and electrolytic drying; in the drying treatment process, when biogas is required for drying, at least part or all of biogas generated in the anaerobic digestion process is used;