CN107032576B

CN107032576B - Operation method for treating excess sludge by adopting horizontal anaerobic reactor

Info

Publication number: CN107032576B
Application number: CN201710390565.9A
Authority: CN
Inventors: 赵明星; 许凤剑; 阮文权; 施万胜; 宋联; 朱葛
Original assignee: Wuxi Guolian Environmental Science & Technology Co Ltd; Jiangnan University
Current assignee: Wuxi Guolian Environmental Science & Technology Co Ltd; Jiangnan University
Priority date: 2017-05-27
Filing date: 2017-05-27
Publication date: 2020-03-06
Anticipated expiration: 2037-05-27
Also published as: CN107032576A

Abstract

The invention discloses an operation method for treating excess sludge by adopting a horizontal anaerobic reactor, belonging to the technical field of organic solid waste treatment and disposal. The invention adopts an anaerobic horizontal reactor to carry out anaerobic digestion on the excess sludge with the solid content of 20 percent, the sludge methane yield reaches 294mL/gVS, the protein and polysaccharide degradation rates are 39.5 percent and 37.4 percent respectively, and the maximum value of the sludge dehydrogenase activity is 312TF mu g/(mL.h). Through the stable operation of the high-solid-state horizontal anaerobic digestion reactor, the daily sludge feeding load is up to 10gTS/L.d, which is 2-3 times higher than that of the traditional wet anaerobic digestion.

Description

Operation method for treating excess sludge by adopting horizontal anaerobic reactor

Technical Field

The invention relates to an operation method for treating excess sludge by adopting a horizontal anaerobic reactor, belonging to the technical field of organic solid waste treatment and disposal.

Background

The excess sludge is activated sludge discharged from the system from a secondary sedimentation tank, a sedimentation zone and the like. The main components of the excess sludge are organic matters such as protein, polysaccharide and the like, and contain pathogenic microorganisms harmful to human health. With the continuous improvement of the urbanization level in China, due to the phenomenon of 'heavy water and light mud' in municipal engineering, the attention and investment on the treatment of the sludge cannot follow the development trend of sewage treatment. During the period from 2011 to 2015, wet sludge with 80% water content is produced averagely at 4800 ten thousand tons each year. This value is expected to reach 6000 million tons in 2020, and the increasing sludge production causes serious environmental pollution.

Compared with other technologies, the anaerobic digestion technology has advantages in sludge treatment and disposal, and anaerobic digestion can not only realize sludge reduction, but also kill pathogenic microorganisms in sludge, stabilize sludge property and improve the sanitary quality of sludge. The traditional anaerobic digestion substrate of sludge is sludge in a concentration tank, the water content of the sludge reaches 95%, a large amount of biogas slurry exists in a digestion system, and a large amount of heat energy needs to be provided by a heating system due to the existence of the biogas slurry. The high solid state digestion of the sludge can improve the solid content of a digestion substrate and reduce the water content in a digestion system. The high solid anaerobic digestion overcomes the defects of the traditional anaerobic treatment, improves the treatment capacity of unit organic matters, improves the digestion efficiency and greatly reduces the production of biogas slurry. When the high solid state fermentation is carried out on the excess sludge, if a traditional vertical digestion device is adopted, certain defects exist, and due to the fact that the viscosity and the density of the excess sludge are large, the sludge is easy to accumulate at the bottom during anaerobic treatment, local acidification is caused, mass and heat transfer are hindered, the fermentation speed is slow, and the like.

Disclosure of Invention

In order to solve the problems, the invention provides a method for treating excess sludge, which utilizes a horizontal reactor with a plug flow type stirring device to anaerobically digest the excess sludge with the solid content of 18-20%.

The first purpose of the invention is to provide a method for treating excess sludge, which comprises the step of feeding aerobic excess sludge into a horizontal reactor containing anaerobic sludge every day for treatment in a continuous feeding mode, wherein the sludge retention time is 32-38 d.

In one embodiment of the invention, the feeding is performed in a manner of feeding 1-1.2 t/d in every 40-50 t of anaerobic sludge and discharging 0.8-0.9 t/d by volume.

In one embodiment of the present invention, the horizontal anaerobic reactor is disclosed in the patent application publication No. 106477842 a.

In one embodiment of the present invention, the solid content of the excess sludge is 18 to 20%.

In one embodiment of the invention, the pH of the excess sludge is 7.2-8.0, TS 18-20%, VS/TS 55-60%, ammonia nitrogen 20-26 mg/kg, total carbon 135-160 g/kg, total nitrogen 25-30 g/kg, and carbon-nitrogen ratio 5.0-5.5.

In one embodiment of the invention, the pH value of the excess sludge is 7.6, TS 20%, VS/TS 55-60%, ammonia nitrogen 23.15mg/kg, total carbon 148.63g/kg, total nitrogen 27.84g/kg, and carbon-nitrogen ratio 5.3.

In one embodiment of the invention, the process is carried out by anaerobic digestion in a horizontal anaerobic reactor.

In an embodiment of the present invention, the method specifically includes: (1) feeding residual sludge into the horizontal anaerobic reactor for 40t at one time, and carrying out anaerobic digestion for 60-75 d; (2) feeding 1-1.2t of aerobic sludge every day by adopting a continuous feeding method, and continuously feeding for 118 d; stirring every day at the stirring speed of 5 r/min.

The invention also provides the application of the method in the field of environment.

Has the advantages that: the invention adopts a horizontal reactor provided with a solar heat insulation system to carry out anaerobic digestion treatment on excess sludge with the solid content of 18-20%. Feeding 1-1.2 tons per day, discharging 800-900kg, the sludge biogas production rate reaches 294mL/gVS, the protein and polysaccharide degradation rates are 39.5% and 37.4% respectively, compared with the discontinuous feeding, the degradation rate is improved by 3.4-7.3%, the ammonia nitrogen content is continuously accumulated in the digestion process, the maximum value reaches 795mg/kg, and the maximum value of the sludge dehydrogenase activity is 312TF [ mu ] g/(mL-h). Through the stable operation of the high-solid-state horizontal anaerobic digestion reactor, the gas production efficiency is remarkably improved, the daily sludge feeding load is up to 10gTS/L.d, and is 2-3 times higher than that of the traditional wet anaerobic digestion.

Drawings

FIG. 1 is a schematic view of a reactor apparatus; r1, R2, R3 and R4 respectively represent four sampling ports.

FIG. 2 is the change in pH during digestion;

FIG. 3 shows the gas production and temperature change during digestion;

FIG. 4 is the change in VFA during digestion;

FIG. 5 shows the ammonia nitrogen change in anaerobic digestion;

FIG. 6 is a graph of the change in VS during anaerobic digestion;

FIG. 7 is a graph showing the change in protein in anaerobic digestion;

FIG. 8 is a graph of the change in polysaccharide during anaerobic digestion.

Detailed Description

The residual sludge is the sludge discharged from a belt filter press of a sewage treatment plant, and the sludge property is shown in table 1.

TABLE 1 aerobic excess sludge Properties

Example 1

Aerobic excess sludge was fed daily to a horizontal sludge reactor containing anaerobic sludge for treatment by continuous feeding (fig. 1). Feeding 1-1.2t per day and discharging 0.8-0.9t per day. The daily sludge feeding load is up to 10gTS/L.d, which is 2-3 times higher than that of the traditional wet anaerobic digestion.

The pH is one of the most important indexes for evaluating the stability of an anaerobic fermentation system, and the pH can influence the activity of methanogenic microorganisms, so that the methane yield is influenced. The most suitable pH range for anaerobic fermentation of methanogenic microorganisms is 6.5-8.2, beyond which methanogenic microorganisms are inhibited.

Stirring the sludge in the reactor at a stirring speed of 5r/min, and monitoring the operation process of the reactor. The change of the pH of the sludge at the four sampling ports in the continuous operation of the reactor is shown in FIG. 2, and it can be seen from the graph that the pH of the sludge at the R1 sampling port is reduced from 7.96 to 7.26 in the first 30 days, and the pH is gradually increased to 7.68 in the last 118 days. The change trend of the sludge of the R2, R3 and R4 groups of sampling ports is basically consistent with that of the sludge of the R1 group, but the change amplitude is small, and the change trend is finally stabilized between 7.6 and 8.1. On day 118 the pH reached 7.66 for group R1, 7.86 for group R2, 7.95 for group R3, and 8.09 for group R4.

FIG. 3 shows the variation of the gas production and temperature of the reactor, and it can be seen from the graph that the temperature in the reactor fluctuates from 32.8 ℃ to 43.5 ℃ and the methane production is 12.5m³To 24m³The range is changed, and the gas production of the reactor is controlled to be 15.5m 10 days before operation³Increased to 22m³And stabilized at 22 for the first 30 daysm³The temperature of the reactor is reduced from 38 ℃ to 32 ℃ due to the influence of plum rain season in 30 to 65 days of operation, and the gas production rate fluctuates along with the temperature. The plum rain season from the 60 th to the 70 th days of the operation of the reactor is ended, the temperature of the reactor is increased back to 37 ℃, and the methane yield is also rapidly increased back to 22m within 10 days³It can be seen that the temperature fluctuation of the reactor is 8-10 ℃ without causing irreversible influence on the operation of the reactor, and the methanogens in the reactor can be quickly restored to the original activity when the temperature rises again. When the reactor is operated from 70 days to 118 days, the temperature reaches 38 ℃ and continuously rises, the highest temperature reaches 43.5 ℃ on the 105 th day, and the methane production amount is maintained at 21-23m³During this period, the gas production is maintained in a steady state. The final biogas production rate of the sludge reaches 294 mL/gVS.

In the anaerobic fermentation process, organic matters are gradually converted into Volatile Fatty Acid (VFA) by microorganisms, and the VFA can be used as a substrate of methanogens and generates methane through self-metabolism. As shown in FIG. 4, the VFA of the reactor was reduced from 12700mg/kg to 2000mg/kg, and it was seen that the VFA utilization was significantly improved.

FIG. 5 shows the variation of ammonia nitrogen concentration during the operation of the reactor, wherein the highest ammonia nitrogen concentration of the R2 group sludge is increased to 710mg/kg, the highest ammonia nitrogen concentration of the R3 group sludge is increased to 740mg/kg, the highest ammonia nitrogen concentration of the R4 group sludge is increased to 770mg/kg, and the highest ammonia nitrogen concentration of the R1 group sludge is slightly decreased.

The change condition of VS in the operation process is shown in FIG. 6, sludge VS at 4 sampling ports in the early stage of the reaction is 6.2% -6.5%, sludge VS/TS at four sampling ports is about 34.8%, sludge VS of 4 groups all has a rising trend 30 days before the operation, sludge VS of R1 group increases to the maximum from 6.7% to 10.7%, sludge VS of R2 group increases to the second from 6.4% to 9.3%, sludge VS of R3 group increases to the third from 6.2% to 7.9%, sludge VS of R4 group increases to the minimum from 6.4% to 7.1%. After the digestion time reaches 30 days, VS values of 4 groups of sludge are kept relatively stable, the sludge property in the reactor cannot be greatly changed due to daily quantitative sludge feeding, the retention time of the sludge in the operation of the reactor is about 35 days, and the VS degradation rate reaches 49.7%.

FIG. 7 shows the variation trend of the protein concentration in the sludge, the undegraded organic matter in the reactor is increased due to the newly entered sludge, the protein content is increased accordingly, the protein concentration is reduced from 420mg/kg to 260-280 mg/kg through the treatment of the reactor, and the protein degradation rate is 39.5%.

FIG. 8 shows the change of polysaccharide content in sludge during digestion, after 20 to 30 days of feeding, the amount of polysaccharide remains relatively stable, the sludge polysaccharide content of R1 group is stabilized at about 310mg/kg, the sludge polysaccharide content of R2 group is stabilized at about 280mg/kg, the sludge polysaccharide content of R3 group is stabilized at about 255mg/kg, the sludge polysaccharide content of R4 group is hardly changed, and the polysaccharide content is maintained at about 195 mg/kg. In the whole digestion process, the polysaccharide content is reduced from 300-320 mg/kg to 180-200 mg/kg, and the degradation rate is 37.4%.

Comparative example 1

The excess sludge is directly fermented without adopting a continuous feeding mode, and the result shows that after the digestion reaction is operated for 3 months, the methane production rate of the sludge reaches 274mL/gVS, the methane content is 58%, the VS conversion rate reaches 46%, the protein and polysaccharide degradation rates are respectively 36.7% and 30.1%, the maximum value of the VFA content in the digestion process is 2395mg/kg, the ammonia nitrogen concentration in the digestion process is slowly increased all the time, and the maximum value is about 124.3 mg/kg.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The method for treating the aerobic excess sludge is characterized in that the aerobic excess sludge is fed into an anaerobic sludge reactor for treatment in a continuous feeding mode, and the method specifically comprises the following steps: (1) feeding aerobic excess sludge into the horizontal anaerobic reactor for 40t at one time, and carrying out anaerobic digestion for 60-75 d; (2) feeding 1-1.2t of aerobic excess sludge per day by adopting a continuous feeding method, discharging at 0.8-0.9 t/d, continuously feeding for 110-120 d, stirring per day at a stirring speed of 5r/min, wherein the pH of the aerobic excess sludge is 7.2-7.6, the TS is 18-20%, the VS/TS is 55-60%, the carbon-nitrogen ratio is 5.0-5.5, the ammonia nitrogen is 20-26 mg/kg, the total carbon is 135-160 g/kg, and the total nitrogen is 25-30 g/kg.

2. The method according to claim 1, wherein the retention time of the aerobic excess sludge in the reactor is 32-38 d.

3. Use of the method according to claim 1 or 2 in the field of the environment.