CN108191144A - A kind of processing method of municipal solid waste incinerator percolate - Google Patents

Abstract

The present invention proposes a kind of processing method of municipal solid waste incinerator percolate, and the present invention is for processing high concentration COD cr, high concentration NH₃N and garbage burning factory percolate high in salt are with obvious effects, can significantly improve effluent quality；Use upflow anaerobic sludge blanket reactor can be with 80% 90%COD in the removal sewage of high-efficiency low energy consumption, system entirety producing water ratio can be improved using ultrafiltration+network pipe type reverse osmosis process, especially network pipe type reverse osmosis process is reverse osmosis compared to common rolling, salt resistance ability is stronger, operating pressure higher, concentration liquid measure is reduced to the receptive level of incineration plant by producing water ratio higher；The excess sludge generated in system is dehydrated by centrifugal dehydrator moisture percentage in sewage sludge being down to 80% hereinafter, then, without being transported using sludge vehicle, avoiding the excessive pollution environment of foul smell in sludge transportational process to trash repository using high pressure screw pump and pipeline.

Description

A treatment method for leachate of domestic waste incineration plant

technical field

The invention relates to a treatment method for leachate, in particular to a treatment method for the leachate of a domestic garbage incineration plant.

Background technique

Landfill leachate is the product of primary waste storage, and incineration plant leachate mainly comes from the liquid produced by the waste itself holding water and waste decomposition. Since waste in China is not collected and treated in a classified manner, and is greatly affected by regions and seasons, the leachate water quality components of waste incineration plants are complex, and the water quality and water volume fluctuate greatly. High concentration of pollutants. According to the current statistics of incineration plant leachate water quality data, the concentration of COD is 30000-60000mg/L, the concentration of BOD is 20000-40000mg/L, and the concentration of ammonia nitrogen is 1500-2500mg/L. In addition, there are a large number of other metals , Inorganic pollutants. More importantly, the current incineration plant as an overall environmental protection system does not allow any sewage to be discharged outside, and all sewage must be absorbed internally to achieve zero discharge of system pollutants.

At present, the industry generally adopts the process of "pretreatment + biochemical treatment + membrane advanced treatment" to treat the leachate of waste incineration plants. Among them, the advanced membrane treatment generally adopts the treatment process of "nanofiltration (NF) + reverse osmosis (RO)" to ensure that the effluent COD and total nitrogen can meet the standards.

Since the leachate of the incineration plant uses the nanofiltration membrane unit mainly to reduce COD, the design of the reverse osmosis membrane unit is to reduce COD and reduce monovalent ions such as ammonia nitrogen and total nitrogen. This process must be operated in series to ensure the quality of the effluent water. Nanofiltration yield The water rate is 85%, the water production rate of reverse osmosis is 70%, and the final overall water production rate of the system is 0.85×0.7=0.595 (59.5%). This operation will inevitably lead to the concentrated liquid produced by the system as high as 40%. The amount of sewage that the system can receive and consume internally is only 15% to 20% of the leachate treatment scale, or even less.

Contents of the invention

In view of this, the present invention proposes a treatment method for the leachate of domestic waste incineration plants with high water production rate and less concentrated liquid.

The technical scheme of the present invention is achieved in that the present invention provides a treatment method for leachate of domestic waste incineration plant, which comprises the following steps,

S1, the landfill leachate is collected from the waste pond and introduced into the solid-liquid separator to remove the solid impurities therein;

S2, importing the landfill leachate obtained in step S1 into a regulating tank for caching;

S3, the effluent of step S2 passes through the upflow anaerobic sludge bed reactor from bottom to top to degrade high-concentration wastewater;

S4, performing MBR enhanced biological denitrification treatment on the effluent of step S3;

S5, performing network-managed reverse osmosis treatment on the effluent in step S4.

On the basis of the above technical solutions, preferably, the COD concentration of the influent in the step S2 is 30,000-60,000 mg/L, the designed influent residence time of the regulating tank is 10 days, and the capacity of the pond is 2000m ³ . The regulating pond includes two parallel-connected Water storage tank, each storage tank has a capacity of 1000m ³ , and two mixers are installed in each storage tank, one of which is set higher than the other.

On the basis of the above technical scheme, preferably, in the step S3, the rising flow rate of the water flow in the upflow anaerobic sludge bed reactor is 0.5-0.8m/h, the anaerobic temperature is 33°C-37°C, and the pH is 6.5- 7.5.

On the basis of the above technical solutions, preferably, the step S4 includes the following steps,

S4-1, the influent is denitrified in the anoxic section in the denitrification tank;

S4-2, for the denitrification effluent enters the nitrification tank, degrades organic pollutants, and oxidizes NH ₃ -N to nitrite or nitrate by nitrifying bacteria, and the obtained nitrite or nitrate is introduced into step S4-1 carry out denitrification reaction;

S4-3, the effluent in step S4-2 is introduced into the sedimentation tank to settle part of the sludge, and the effluent flows into the buffer tank;

S4-4, the effluent from the buffer tank in step S4-3 is introduced into the ultrafiltration membrane system for processing.

Further preferably, an external ultrafiltration membrane is used in the step S4-4, the sludge concentration in the steps S4-1 to S4-3 is 15-30g/L, and the turbidity value of the effluent from the ultrafiltration membrane system is lower than 5NTU, SDI If the value is lower than 5, the dope of the ultrafiltration membrane system is returned to the denitrification tank in step S4-1 and the nitrification tank in step S4-2.

Further preferably, the pH of the nitrification tank in the step S4-2 is 7-8, and the temperature of the nitrification tank is lower than 35°C.

On the basis of the above technical solutions, preferably, in step S5, add acid to the effluent of step S4 to adjust the pH value to 6.0-6.5, add scale inhibitor, and then use a high-pressure pump to pressurize the water flow to 30-40bar, after pressurization The water flow through the network tube reverse osmosis membrane. Further preferably, the concentrated water passing through the network tube type reverse osmosis membrane is mixed with the pressurized water flow and then passes through the network tube type reverse osmosis membrane again.

On the basis of the above technical solution, preferably, step S6 is also included, and the sludge generated in steps S3 and S4 is pumped to the sludge tank, and PAM with a concentration of 1‰～3‰ is added, and then sent to the centrifugal dehydration The liquid phase after dehydration is pumped to the denitrification tank, and the solid phase with a solid content higher than 20% after dehydration is transported to the garbage bin by high-pressure screw pumps and pipelines.

On the basis of the above technical solutions, preferably, step S7 is also included, and the odor generated in steps S1-S5 is collected through glass fiber reinforced plastic pipes, and then introduced into a biofilter for deodorization.

Compared with the prior art, the treatment method of domestic waste incineration plant leachate has the following beneficial effects:

(1) The present invention has an obvious effect on treating high-concentration CODcr, high-concentration NH ₃ -N and high-salt waste incineration plant leachate, and can greatly improve the quality of effluent water;

(2) Upflow anaerobic sludge bed reactor can remove 80%-90% COD in sewage with high efficiency and low energy consumption, and the use of ultrafiltration + network-managed reverse osmosis process can improve the overall water production rate of the system, especially network-managed reverse osmosis Compared with ordinary roll-type reverse osmosis, the process has stronger salt tolerance, higher operating pressure, and higher water production rate, which reduces the amount of concentrated liquid to the level that the incineration plant can accept, and the water production rate can reach 85% of the treatment scale. , The concentrated solution scale is only 15%;

(3) The excess sludge generated in the system is dehydrated by a centrifugal dehydrator to reduce the moisture content of the sludge to below 80%, and then transported to the garbage bin by high-pressure screw pumps and pipelines instead of using sludge trucks to avoid sludge During transportation, the odor spills out and pollutes the environment.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the flow chart of the treatment method of leachate of domestic waste incineration plant of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

As shown in Figure 1, the processing method of domestic waste incineration plant leachate of the present invention, with processing 200 tons/day refuse incineration plant leachate as example, comprises the following steps:

S1, enhanced pretreatment of landfill leachate. The landfill leachate is collected from the landfill pool and then introduced into the solid-liquid separator to remove solid impurities. The large-sized solid particles, sediment, hair, and fiber substances are intercepted by the solid-liquid separator, so as to avoid entering the subsequent membrane system and causing blockage of the membrane. The separator has the advantages of good interception effect, compact structure and high degree of automation. Specifically, the solid-liquid separator can be equipped with a reverse high-pressure water spray cleaning system and an automatic slag scraping system to collect the retained filter residue into the slag collection tank, and then discharge the filter residue by the slag discharge system. The solid-liquid separator can replace the traditional solid-liquid separation devices such as the drum grille, and has the advantages of good filter residue effect, high degree of automation, and convenient cleaning and maintenance.

S2, adjust pool processing. The landfill leachate obtained in step S1 is introduced into a regulating tank for buffering. The adjustment tank is mainly to adjust the incoming water volume. The buffer of the adjustment tank can ensure that the influent water entering the next-stage upflow anaerobic sludge bed reactor has a smaller range of changes. The COD concentration of the influent water in the adjustment tank is 30000-60000mg/ L, to avoid shock loads on the upflow anaerobic sludge bed reactor. When the amount of water is too much during the flood season, and the treatment capacity of the leachate treatment system is limited, a large-capacity regulating tank is required for water storage, so as to avoid delaying the waste incineration capacity of the waste incineration system due to untimely leachate treatment. The design water residence time of the regulating tank is 10 days, and the leachate output can be stored for up to 10 days. The tank capacity is 2000m ³ . Specifically, the regulating tank includes two water storage tanks connected in parallel, so that when one of them is overhauled, the leachate treatment system of the other regulating tank can also operate. The capacity of each storage tank is 1000m ³ , and two mixers are installed in each storage tank, one of which is set higher than the other to adapt to different water levels in the adjustment tank and ensure that the adjustment tank is low and does not settle. Specifically, the height of one mixer is 540mm from the bottom of the water storage tank, and the height of the other mixer is the middle height of the water storage tank and is arranged along the pool wall.

S3, anaerobic UASB treatment. The effluent from step S2 passes through the upflow anaerobic sludge bed reactor from bottom to top to degrade high-concentration wastewater. Specifically, the effluent from the regulating tank is lifted to the upflow anaerobic sludge bed reactor through the screw pump, and the design of the screw pump is for the convenience of maintenance and safety. There is a high concentration and high activity sludge layer at the bottom of the upflow anaerobic sludge bed reactor, where most of the organic matter is converted into CH ₄ and CO ₂ . Due to the agitation of gaseous products and the adhesion of air bubbles to the sludge, a sludge suspension layer is formed above the sludge layer. The upper part of the upflow anaerobic sludge bed reactor is equipped with a three-phase separator to complete the separation of gas, liquid and solid. The separated gas is exported from the upper part, and the separated sludge automatically slides down to the suspended sludge layer. The effluent flows out from the clarification zone. Since a large amount of anaerobic sludge is retained in the upflow anaerobic sludge bed reactor, the sludge concentration is as high as 60g/L, which makes the reactor have a large load capacity. According to the detected sludge concentration, the upflow anaerobic sludge bed reactor is regularly discharged. The diameter of the connected sludge discharge pipe is DN150, and multiple points are set to discharge the sludge evenly. way to discharge sludge. An anaerobic circulating pump is installed in the upflow anaerobic sludge bed reactor to ensure the height of the sludge bed in the upflow anaerobic sludge bed reactor, and the rising velocity of the water flow is 0.5-0.8m/h. In addition, a steam-water mixer is installed on the outlet pipe of the anaerobic circulation, and the steam is sent to the equipment to heat the anaerobic system. The anaerobic temperature is maintained at 33°C to 37°C for medium-temperature anaerobic use. The saturated steam pressure used is 0.4Mpa and the temperature is 143.64 ℃; An on-line pH instrument is installed on the circulation pipeline. Generally, the anaerobic reaction is an acid production process. In order to ensure the anaerobic efficiency, it is necessary to control the pH in the upflow anaerobic sludge bed reactor at 6.5-7.5, so the design has alkali dosing device, the flow rate of the alkali dosing pump used is 100L/H, and the operating data shows that the removal rate of the unit for COD reaches 85%.

S4, MBR enhanced biological denitrification treatment. The effluent of step S3 is subjected to MBR enhanced biological denitrification treatment. Specifically, MBR enhanced biological denitrification treatment includes biochemical treatment of denitrification and nitrification, and ultrafiltration membrane treatment. Specifically, the following steps are included,

S4-1, the incoming water undergoes denitrification reaction in the anoxic section in the denitrification tank. Specifically, two submersible mixers are designed for each denitrification tank, and the mixers are arranged at different heights to ensure uniform stirring in the denitrification tank.

S4-2, for the denitrification effluent enters the nitrification tank, degrades organic pollutants, and oxidizes NH ₃ -N to nitrite or nitrate by nitrifying bacteria, and the obtained nitrite or nitrate is introduced into step S4-1 Carry out denitrification reaction, reduce to nitrogen, and remove part of COD at the same time. Specifically, the pH of the nitrification pool is 7-8, and the temperature of the nitrification pool is lower than 35°C. Specifically, the nitrite or nitrate in the nitrification tank is returned to the denitrification tank through the nitrate return pump, and the return ratio is 8-10 times.

S4-3, the effluent in step S4-2 is introduced into the sedimentation tank to settle part of the sludge, and the effluent flows into the buffer tank. The sedimentation tank can settle part of the sludge. On the one hand, the settled sludge is returned to the denitrification tank through the sludge return pump and pipeline to maintain the concentration of biochemical sludge; on the other hand, the sludge entering the ultrafiltration membrane system is reduced, and the ultrafiltration Reduce the frequency of membrane fouling and increase the water production rate of the ultrafiltration membrane system.

S4-4, the effluent from the buffer tank in step S4-3 is introduced into the ultrafiltration membrane system for processing. The function of the ultrafiltration membrane is to separate mud and water, and an external ultrafiltration membrane is used. The interception effect of the ultrafiltration membrane can make the sludge concentration in steps S4-1~S4-3 15-30g/L, and prolong the sludge age, so that nitrifying autotrophic bacteria, which have a long generation time It grows effectively in the pool, and at the same time, the microbial flora formed through continuous domestication also has a good degradation function for the refractory biodegradable organic matter in the leachate. At the same time, the turbidity value of the ultrafiltration membrane outlet water is lower than 5NTU, and the SDI value is lower than 5, which can meet the water inlet requirements of the subsequent membrane advanced treatment system. Specifically, a return pipe is provided in the ultrafiltration membrane system to return the concentrated liquid to the denitrification tank and nitrification tank to avoid sludge loss.

Specifically, when the COD concentration entering the S4-1 denitrification tank is lower than 10,000 mg/L, the effluent from the adjustment tank in step S2 surpasses step S3 and directly enters the denitrification tank to ensure the carbon source required for the denitrification reaction.

S5, network management reverse osmosis treatment. Perform network-managed reverse osmosis treatment on the effluent in step S4. Add acid to the ultrafiltered water in step S4 to adjust the pH value to 6.0-6.5. Add scale inhibitors to prevent scaling of inorganic salts such as silicates and sulfates. The amount of scale inhibitors added is based on the scale ion content in the wastewater, and the general value is 3-5ppm. Then use a high-pressure pump to pressurize the water flow to 30-40bar. The head of the high-pressure pump is H=800m. The purpose is to provide a higher pressure for the operation of the network-managed reverse osmosis membrane to increase the water production of the network-managed reverse osmosis system. At the same time, to overcome membrane fouling And improve the water production rate of network-managed reverse osmosis. The pressurized water flows through the network tube reverse osmosis membrane. Specifically, the network-managed reverse osmosis adopts the concentrated internal circulation mode, and the circulating pump is set to mix the concentrated water of the network-managed reverse osmosis membrane with the pressurized water flow and then pass through the network-managed reverse osmosis membrane again, so as to ensure the surface filtration of the network-managed reverse osmosis membrane. flow rate. The operating pressure of the network tube reverse osmosis membrane system is 30-40bar, the water production rate is high, up to 85%, and the effluent water quality is stable.

S6, sludge treatment. The remaining sludge generated in steps S2, S3 and S4 is pumped to the sludge tank. Due to the high concentration of sludge, especially the high concentration and high viscosity of anaerobic sludge, the sludge needs to be discharged by means of power. The solid content of the sludge produced in steps S2, S3 and S4 is 2%-4%, and PAM with a concentration of 1‰-3‰ is added, and then sent to the centrifugal dehydrator. The liquid phase after dehydration is pumped to the denitrification tank, and the solid phase with a solid content higher than 20% after dehydration is transported to the garbage bin by high-pressure screw pumps and pipelines instead of using sludge trucks to avoid sludge During transportation, the odor spills out and pollutes the environment.

S7, odor collection and treatment. The odor generated in steps S1-S5 is collected through a glass fiber reinforced plastic pipe, and then introduced into a biofilter for deodorization. The deodorization method of the biological filter is that the odor passes through the filter layer that is moist, porous and full of active microorganisms, and the adsorption, absorption and degradation of the odorous substances by the microbial cells are used, and the cells of the microorganisms are small in size, large in surface area, strong in adsorption, and metabolized. Various types of characteristics, decompose odorous substances into CO ₂ , H ₂ O, H ₂ SO ₄ , HNO ₃ and other simple inorganic substances after adsorption. Biological filter deodorization is a safe and reliable treatment method, with a deodorization efficiency greater than 90%, and can achieve a good environment for leachate treatment stations without odor.

Specifically, it also includes biogas treatment and recycling steps: the biogas yield of the upflow anaerobic sludge bed reactor is as high as 0.4kg/kg.COD, and the gas production is large. For the biogas produced by the upflow anaerobic sludge bed reactor, after desulfurization and dehydration treatment, it is pressurized by a biogas fan and transported to the waste incinerator through pipelines for combustion. Make full use of the biogas energy. During the maintenance of the incinerator, the biogas is desulfurized and dehydrated and then connected to the emergency flare for combustion through pipelines.

Take the leachate treatment of 200 tons/day waste incineration plant as an example. Adopt the treatment method of domestic waste incineration plant leachate of the present invention, collect the water quality in each step and detect, obtain the result as shown in the table below:

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. a treatment method for domestic waste incineration plant leachate, characterized in that: it comprises the following steps, S1, the landfill leachate is collected from the waste pond and introduced into the solid-liquid separator to remove the solid impurities therein; S2, importing the landfill leachate obtained in step S1 into a regulating tank for caching; S3, the effluent of step S2 passes through the upflow anaerobic sludge bed reactor from bottom to top to degrade high-concentration wastewater; S4, performing MBR enhanced biological denitrification treatment on the effluent of step S3; S5, performing network-managed reverse osmosis treatment on the effluent in step S4. 2. The method for treating leachate of domestic waste incineration plant as claimed in claim 1, characterized in that: in said step S2, the influent COD concentration is 30,000-60,000 mg/L, and the designed influent residence time of the regulating tank is 10 days, and the pond The capacity is 2000m ³ , and the adjustment tank includes two parallel connected storage tanks, each storage tank has a capacity of 1000m ³ , and two mixers are installed in each storage tank, one of which is set higher than the other. 3. The method for treating leachate of domestic waste incineration plant as claimed in claim 1, characterized in that: in the step S3, the rising velocity of the water flow in the upflow anaerobic sludge bed reactor is 0.5～0.8m/h, anaerobic The temperature is 33°C-37°C, and the pH is 6.5-7.5. 4. The processing method of domestic waste incineration plant leachate as claimed in claim 1, characterized in that: said step S4 comprises the following steps, S4-1, the influent is denitrified in the anoxic section in the denitrification tank; S4-2, for the denitrification effluent enters the nitrification tank, degrades organic pollutants, and oxidizes NH ₃ -N to nitrite or nitrate by nitrifying bacteria, and the obtained nitrite or nitrate is introduced into step S4-1 carry out denitrification reaction; S4-3, the effluent in step S4-2 is introduced into the sedimentation tank to settle part of the sludge, and the effluent flows into the buffer tank; S4-4, the effluent from the buffer tank in step S4-3 is introduced into the ultrafiltration membrane system for processing. 5. The method for processing leachate of domestic waste incineration plant as claimed in claim 4, characterized in that: an external ultrafiltration membrane is adopted in the step S4-4, and the sludge concentration in the steps S4-1～S4-3 is 15-30g/L, the turbidity value of the effluent from the ultrafiltration membrane system is lower than 5NTU, and the SDI value is lower than 5, and the concentrated liquid of the ultrafiltration membrane system is returned to the denitrification tank in step S4-1 and the nitrification tank in S4-2. 6. The method for treating the leachate of domestic waste incineration plant according to claim 4, characterized in that: the pH of the nitrification tank in the step S4-2 is 7-8, and the temperature of the nitrification tank is lower than 35°C. 7. The method for treating leachate of domestic waste incineration plant as claimed in claim 1, characterized in that: in step S5, add acid to the effluent of step S4 to adjust the pH value to 6.0-6.5, add antiscalant, and then use high-pressure pump The water flow is pressurized to 30-40bar, and the pressurized water flow passes through the network tube reverse osmosis membrane. 8. The method for treating leachate of domestic waste incineration plant as claimed in claim 7, characterized in that: the concentrated water passing through the network-managed reverse osmosis membrane is mixed with the pressurized water flow and then passed through the network-managed reverse osmosis membrane again. 9. The processing method of domestic waste incineration plant leachate as claimed in claim 1, characterized in that: it also includes step S6, the sludge generated in steps S3 and S4 is discharged to the sludge pond by pump, and the added concentration is 1 ‰～3‰ PAM, and then sent to the centrifugal dehydrator, the liquid phase after dehydration is pumped to the denitrification tank, and the solid phase with a solid content higher than 20% after dehydration is transported to the garbage bin by high-pressure screw pump and pipeline . 10. The method for processing leachate from domestic waste incineration plants as claimed in claim 1, further comprising step S7, collecting the odor generated in steps S1 to S5 through glass fiber reinforced plastic pipes, and then introducing it into a biofilter for deodorization .