CN111470731B - Method and system for treating leachate of refuse landfill - Google Patents
Method and system for treating leachate of refuse landfill Download PDFInfo
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Abstract
The invention discloses a method and a system for treating percolate in a refuse landfill.A coagulant is added into raw percolate water for coagulating sedimentation to obtain mixed liquor; carrying out filter pressing on the precipitate in the mixed solution to obtain filter-pressed effluent; performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water; and refluxing the filter-pressing effluent and the microfiltration concentrated water into raw leachate water for circulation treatment, and finally obtaining the water which reaches the standard through two-stage DTRO treatment and resin adsorption treatment. Ensuring long-term stable operation of the landfill leachate treatment system and ensuring that the produced water reaches the standard and is discharged through various combined processes; partial organic matters and large suspended particles can be removed through coagulating sedimentation, organic pollution of a subsequent microfiltration membrane is relieved, colloid can be effectively intercepted through microfiltration treatment to remove hydrogen sulfide, the problems that a two-stage DTRO colloid pollutes a membrane, even a runner is blocked, and sulfur pollution is caused can be solved.
Description
Technical Field
The invention belongs to the field of landfill leachate treatment, and particularly relates to a method and a system for treating leachate in a landfill.
Background
With the development of national economy and the improvement of the living standard of people, the production amount of domestic garbage also increases day by day, the average daily garbage yield of each person in China is 0.8-1.1kg at the present time, and the garbage increases year by year at a rate of 10%, and the garbage yield is estimated to reach 4.09 hundred million tons in 2030 and 5.28 hundred million tons in 2050. Landfill is a main mode for treating garbage in China, landfill leachate is high-concentration organic wastewater generated in a landfill site, and if the landfill leachate is not properly treated, the landfill leachate can cause serious pollution to surrounding surface water and underground water, and the living environment of human beings is seriously threatened.
The water quality of the initial leachate of the refuse landfill is characterized by pH being acidic and BOD 5 High content of ammonia nitrogen, low content of ammonia nitrogen and good biodegradability. With the lapse of time, the quality of leachate from old landfills shows serious imbalance of C/N and deterioration of biodegradability of water quality. The landfill leachate treatment mostly adopts a biological method and a membrane advanced treatment process, and the method has good treatment effect on the initial leachate of the landfill, but has very high treatment difficulty on the aged leachate. In recent years, a pure membrane method disc tube type reverse osmosis technology is applied to treatment of percolate, the method has high automation degree, and the effluent is stable and reaches the standard, but problems such as easy pollution of colloid in raw percolate water to a membrane, even blockage of a flow channel, easy sulfur pollution of sulfide in the raw water to the membrane and the like exist.
In the existing leachate treatment technology, the process of 'anaerobic + multi-stage A/O (anoxic/aerobic) + MBR (membrane bioreactor) + NF (nanofiltration) + RO (reverse osmosis)' is most commonly applied. The process adopts biochemical treatment and membrane advanced treatment, aims at the biochemical treatment of percolate of old landfill, has serious imbalance of C/N ratio and poor biodegradability of water quality, needs to add a large amount of carbon source to raw water, causes high operation cost and poor stability, has extremely high requirement on operators, seriously limits the stable operation of the whole system, and has large floor area of a biochemical treatment and membrane advanced treatment system, long construction period and low automatic control. The pure membrane method mainly adopts a disc tube type reverse osmosis technology, the method adopts a process of 'sand filtration + core filtration + two-stage DTRO + resin adsorption', the method mainly adopts a pure physical interception method to remove pollutants, the system integration level is high, the automation degree is high, the effluent can reach the standard stably, but the problem that the colloid in raw leachate pollutes membranes and even blocks flow channels easily occurs, so that equipment faults or even operation cannot be caused, and secondly, the leachate is in an anaerobic state for a long time, the content of reducing sulfide in the water is high, and the sulfur pollution is easily caused to the membranes.
In view of the above, there is a need to develop a new process for treating the old landfill leachate which is difficult to be biologically treated.
Disclosure of Invention
The application aims to provide a method and a system for treating leachate in a refuse landfill to solve the problems that colloids in raw leachate easily pollute membranes or even block flow channels, sulfides in raw leachate easily pollute the membranes and the like.
In a first aspect, an embodiment of the present application provides a method for treating leachate in a landfill, including the following steps:
s1: adding a coagulant into raw leachate water for coagulating sedimentation to obtain a mixed solution;
s2: carrying out filter pressing on the precipitate in the mixed solution to obtain filter-pressed effluent;
s3: performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water; and
s4: and refluxing the filter-pressing effluent and the microfiltration concentrated water into the raw leachate for circulating treatment.
The process can solve the problems of large occupied area, long construction period, low self-control performance, colloid pollution of a membrane even blocking a flow channel, sulfur pollution and the like of a biochemical and membrane advanced treatment process.
In some embodiments, step S1 specifically includes:
s11: adding a coagulant into raw water of the percolate to stir and react;
s12: and carrying out precipitation separation on the mixed solution obtained after the reaction.
The coagulant and the raw water of the percolate can be subjected to coagulating sedimentation by adding drugs and stirring, and large-particle suspended matters and a part of macromolecular organic matters in the raw water of the percolate are removed through coagulating sedimentation.
In some embodiments, the pH of the raw leachate water is adjusted to 9 to 9.5 after the coagulant is added in step S1. The coagulant is added to improve the pH value to adjust the leachate to be alkaline, the organic pollutants are adjusted to have the same electrical property with the microfiltration membrane, the net charge quantity of the organic pollutants and the microfiltration membrane is increased, the acting force between the membrane and the pollutants can be weakened, and the organic pollution of a subsequent microfiltration membrane layer is relieved.
In some embodiments, the coagulant comprises calcium hydroxide. The calcium hydroxide can not only carry out coagulation and precipitation reaction with partial substances in raw water of the percolate, but also adjust the pH value of the percolate so as to slow down the organic pollution of a membrane layer of the subsequent microfiltration treatment.
In some embodiments, microfiltration is performed in step S3 using submerged MBR membrane modules. The microfiltration treatment adopts an immersed MBR membrane component, so that colloid in the percolate can be effectively intercepted, hydrogen sulfide is removed, and qualified inlet water is provided for DTRO.
In some embodiments, the membrane module used in the microfiltration treatment in step S3 is a hollow fiber membrane, the hollow fiber membrane is made of PVDF, and the pore size is 0.03 to 0.1 μm. The PVDF hollow fiber membrane has a stain resistant effect, and can fully ensure good colloid retention and effective mud-water separation.
In some embodiments, the microfiltration treatment employs microporous aeration. Bubbles released by aeration are mixed with liquid part to form vortex on the surface of the membrane, the rising air scrubs and cleans the outer surface of the middle fiber outer membrane to delay membrane pollution, meanwhile, oxygen in the aeration can oxidize hydrogen sulfide in water to slow down sulfur pollution of the membrane layer during DTRO treatment, and elemental sulfur generated by reaction flows back to the front end along with the microfiltration concentrated water to be removed by coagulating sedimentation.
In some embodiments, further comprising: the microfiltration product water is subjected to two-stage DTRO treatment, the two-stage DTRO treatment comprises one-stage DTRO treatment and two-stage DTRO treatment, the one-stage product water obtained by the one-stage DTRO treatment is subjected to the two-stage DTRO treatment, the two-stage product water obtained by the two-stage DTRO treatment is subjected to resin adsorption treatment to obtain final product water, and the two-stage concentrated water obtained by the two-stage DTRO treatment is refluxed to carry out the one-stage DTRO treatment. The two-stage DTRO treatment has high rejection rate of pollutants, the removal rate of COD and ammonia nitrogen is more than 99%, the produced water basically reaches the standard, only the ammonia nitrogen index is slightly high, the treated water enters the rear-end resin adsorption treatment, and the resin adsorption treatment is mainly used for further reducing the ammonia nitrogen in the two-stage DTRO produced water.
In a second aspect, an embodiment of the present application further provides a landfill leachate treatment system, including a coagulating sedimentation unit, a filter pressing unit, and a microfiltration unit, where the leachate raw water is fed into the coagulating sedimentation unit to be added with a coagulant for coagulating sedimentation, a supernatant outlet end of the coagulating sedimentation unit is connected to a water inlet end of the microfiltration unit, a precipitate outlet end of the coagulating sedimentation unit is connected to an inlet end of the filter pressing unit, and a water outlet end of the filter pressing unit and a concentrated water outlet end of the microfiltration unit are connected to a water inlet end of the coagulating sedimentation unit.
In some embodiments, the coagulating sedimentation unit specifically includes a dosing device, a stirring device and a sedimentation device, the dosing device is used for adding a coagulant into raw leachate, the stirring device is used for stirring and reacting the raw leachate with the coagulant, and the sedimentation device is used for carrying out sedimentation separation on mixed liquor obtained after reaction. The dosing device and the stirring device can enable the coagulant and the raw water of the percolate to carry out coagulating sedimentation, and large particle suspended matters and a part of macromolecular organic matters in the raw water of the percolate are removed through coagulating sedimentation.
In some embodiments, the coagulating agent is added into the coagulating sedimentation unit, and then the pH value of raw leachate is adjusted to 9-9.5. The coagulant is added to improve the pH value to adjust the leachate to be alkaline, the organic pollutants are adjusted to have the same electrical property with the microfiltration membrane, the net charge quantity of the organic pollutants and the microfiltration membrane is increased, the acting force between the membrane and the pollutants can be weakened, and the organic pollution of a subsequent microfiltration membrane layer is relieved.
In some embodiments, the coagulant comprises calcium hydroxide. The calcium hydroxide can not only carry out coagulation and precipitation reaction with partial substances in raw water of the percolate, but also adjust the pH value of the percolate so as to slow down the organic pollution of a membrane layer of the subsequent microfiltration treatment.
In some embodiments, the microfiltration unit employs submerged MBR membrane modules for microfiltration. The microfiltration treatment adopts an immersed MBR membrane component, so that colloid in the percolate can be effectively intercepted, hydrogen sulfide is removed, and qualified inlet water is provided for DTRO.
In some embodiments, the microfiltration unit uses a hollow fiber membrane, the hollow fiber membrane is made of PVDF, and the pore size is 0.03-0.1 μm. The PVDF hollow fiber membrane has a stain-resistant effect, and can fully ensure good colloid retention and effective mud-water separation.
In some embodiments, the bottom of the microfiltration unit is sparged with micropores. Bubbles released by aeration are mixed with liquid part to form vortex on the surface of the membrane, the rising air scrubs and cleans the outer surface of the fiber outer membrane, the membrane pollution is delayed, meanwhile, oxygen in the aeration can oxidize hydrogen sulfide in water to slow down the sulfur pollution of a DTRO unit, and elemental sulfur generated by reaction flows back to the front end along with microfiltration concentrated water and is removed through coagulating sedimentation.
In some embodiments, the system further comprises a two-stage DTRO unit and a resin adsorption unit, the two-stage DTRO unit comprises a first-stage DTRO device and a second-stage DTRO device, the water outlet end of the produced water of the microfiltration unit is connected with the water inlet end of the first-stage DTRO device, the water outlet end of the produced water of the first-stage DTRO device is connected with the water inlet end of the second-stage DTRO device, the water outlet end of the produced water of the second-stage DTRO device is connected with the water inlet end of the resin adsorption unit, and the concentrated water outlet end of the second-stage DTRO device is connected with the water inlet end of the first-stage DTRO device. The two-stage DTRO unit treatment has high rejection rate of pollutants, the removal rate of COD and ammonia nitrogen is more than 99%, the produced water basically approaches to the standard, only the ammonia nitrogen index is slightly high, the treated water enters a rear-end resin adsorption unit for treatment, and the resin adsorption treatment is mainly used for further reducing the ammonia nitrogen in the two-stage DT produced water.
The application discloses a method and a system for treating leachate of a refuse landfill, wherein coagulant is added into raw leachate for coagulating sedimentation to obtain mixed liquor; carrying out filter pressing on the precipitate in the mixed solution to obtain filter-pressed effluent; performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water; and refluxing the filter-pressing effluent and the microfiltration concentrated water into raw leachate water for circulation treatment, and finally obtaining the water which reaches the standard through two-stage DTRO treatment and resin adsorption treatment. Ensuring the long-term stable operation of the landfill leachate treatment system and ensuring the standard discharge of the produced water of the landfill leachate through various combined processes; partial organic matters and large suspended particles can be removed through coagulating sedimentation, organic pollution of a subsequent microfiltration membrane is slowed down, colloid can be effectively intercepted through microfiltration treatment, hydrogen sulfide is removed, the problems that a membrane is polluted by two-stage DTRO colloid, even a flow channel is blocked, and sulfur pollution is caused can be solved, a key effect is played on stable operation of the two-stage DTRO, and the method and the system are suitable for processing stock garbage percolate and biochemical poor aged percolate.
Drawings
The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
FIG. 1 is a flow chart of a landfill leachate treatment process according to an embodiment of the present invention;
FIG. 2 is a flow chart of a landfill leachate treatment process according to an embodiment of the present invention;
fig. 3 is a flow diagram of a landfill leachate treatment system of an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention will be described in detail with reference to the accompanying drawing 1, and an embodiment of the invention provides a method for treating leachate in a landfill, which comprises the following steps:
s1: adding a coagulant into raw leachate water for coagulating sedimentation to obtain a mixed solution;
s2: carrying out filter pressing on the precipitate in the mixed solution to obtain filter-pressed effluent;
s3: performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water; and
s4: and refluxing the filter-pressing effluent and the microfiltration concentrated water into the raw leachate for circulating treatment.
The invention adopts a combined process of 'modification pretreatment + microfiltration (immersed MBR) + two-stage DTRO + resin adsorption', solves the problems of large occupied area, long construction period and low self-control performance of 'biochemical treatment + membrane advanced treatment' process, and simultaneously solves the problems of colloid pollution of membranes, even flow channel blockage and sulfur pollution in 'sand filtration + core filtration + two-stage DTRO + resin adsorption' process.
In a specific embodiment, the step S1 is a modification pretreatment process, which mainly removes large suspended particles by adding a coagulant into raw leachate water for coagulation, and can increase pH to change the leachate to alkaline to mitigate organic pollution of a membrane layer subjected to back-end microfiltration treatment. As shown in fig. 2, step S1 specifically includes:
s11: adding a coagulant into raw water of the percolate to stir and react;
s12: and carrying out precipitation separation on the mixed solution obtained after the reaction.
The coagulant and raw leachate water can be subjected to coagulating sedimentation by adding chemicals and stirring, and a part of macromolecular organic matters and large suspended particles in the raw leachate water can be removed through coagulating sedimentation. And carrying out precipitation separation on the mixed liquor obtained after the coagulation precipitation, and carrying out filter pressing on the sludge obtained by the precipitation separation.
In a specific embodiment, after the coagulant is added in the step S1, the pH value of raw leachate is adjusted to 9-9.5. In a preferred embodiment, the coagulant is sodium hydroxide, which may be sourced from quicklime or slaked lime. Adding sodium hydroxide into raw percolate water to adjust the pH value to about 9-9.5 for coagulating sedimentation, removing a part of macromolecular organic matters and large suspended particles in the raw percolate water through coagulating sedimentation, adjusting organic pollutants to have the same electrical property with a microfiltration membrane by adjusting the percolate to be alkaline, increasing the net charge amount of the organic pollutants and the microfiltration membrane, weakening the acting force between the membrane-pollutant and the pollutant-pollutant, and slowing down the organic pollution of a subsequent microfiltration membrane layer.
The microfiltration treatment is used as the core part of the pretreatment part, can effectively intercept colloid in the percolate, remove hydrogen sulfide and provide qualified inlet water for DTRO. In a preferred embodiment, microfiltration is performed in step S3 using submerged MBR membrane modules. The microfiltration treatment adopts an immersed MBR membrane component, the membrane component adopts a hollow fiber membrane, the material of the hollow fiber membrane is PVDF, and the aperture is 0.03-0.1 μm. The PVDF hollow fiber membrane has the effect of pollution resistance, has a filtering pore diameter of 0.03-0.1 mu m, and can fully ensure good colloid interception and effective mud-water separation.
In a specific embodiment, the microfiltration process employs microporous aeration. The bubble of aeration release forms the vortex through mixing on the membrane surface with liquid part, and the surface of fibre adventitia in the rising air scrubbing and cleanness delays the membrane pollution, and oxygen in the aeration can be with the hydrogen sulfide oxidation in the aquatic simultaneously, slows down the sulphur pollution of rete when DTRO handles, and the reaction of taking place is: o is 2 +H 2 S→H 2 And O + S ↓, wherein the elemental sulfur generated by the reaction flows back to the front end along with the microfiltration concentrated water and is removed by coagulating sedimentation. The micro-filtration produced water is discharged in a self-priming pump negative pressure suction mode, the operation pressure is lower than 60kpa, and the micro-filtration produced water is subjected to subsequent further treatment.
In a specific embodiment, the processing method of the embodiment of the present invention further includes: the microfiltration product water is subjected to two-stage DTRO treatment, the two-stage DTRO treatment comprises one-stage DTRO treatment and two-stage DTRO treatment, the one-stage product water obtained by the one-stage DTRO treatment is subjected to the two-stage DTRO treatment, the two-stage product water obtained by the two-stage DTRO treatment is subjected to resin adsorption treatment to obtain final product water, and the two-stage concentrated water obtained by the two-stage DTRO treatment is refluxed to carry out the one-stage DTRO treatment. The membrane component adopted by the two-stage DTRO treatment is of a disc-type structure, and has more excellent anti-pollution capacity compared with a common roll-type membrane, the operating pressure of the first-stage DTRO is 50-75bar, the highest withstand pressure is 90bar, the first-stage concentrated water is discharged outside and returned to a tank or evaporated, the first-stage produced water enters the second-stage DTRO, the operating pressure of the second-stage DTRO is 20-30bar, the second-stage concentrated water flows back to the first-stage DTRO, and the second-stage produced water is subjected to resin adsorption treatment. The two-stage DTRO treatment has high pollutant retention rate, COD and ammonia nitrogen removal rate is more than 99 percent, the produced water basically reaches the standard, only ammonia nitrogen index is slightly high, and the treated water enters the rear-end resin adsorption treatment.
In a preferred embodiment, the adsorption contact time of the resin adsorption treatment is 30-60min, the resin adsorption is used as the guarantee that the produced water reaches the standard, the ammonia nitrogen in the two-stage DTRO produced water is mainly further reduced, and the effluent of the landfill leachate can reach the standard of Table 3 in the domestic garbage landfill control Standard GB16889-2008, namely the ammonia nitrogen is less than or equal to 8mg/L, and the total nitrogen is less than or equal to 20mg/L.
Example 1
The original membrane method process of raw water of landfill leachate treated in a certain landfill in Henan is 'raw water of leachate + basket filter + sand filtration + core filtration + two-stage DTRO + resin adsorption', and because the content of suspended matters in the raw water of the leachate is high, the sand filtration is frequently backwashed, and a DTRO membrane flow channel is frequently blocked. Then, adopting a process of 'modification pretreatment + microfiltration (immersed MBR) + two-stage DTRO + resin adsorption', adding 1% hydrated lime into raw leachate, stirring and reacting to obtain a leachate, and then allowing the leachate to have a pH value of 9.2 and enter a sedimentation tank for sedimentation; supernatant enters an immersed MBR unit, micro-filtration produced water is pumped by a self-priming pump, the operating pressure is 20-50kpa, the bottom is subjected to micro-pore aeration, and the aeration intensity is 100Nm 3 /h·m 2 The reflux ratio of the microfiltration concentrated water is 50 percent, and the microfiltration produced water enters two stages againAnd DTRO, wherein the operation pressure of the first-stage DTRO is 50-75bar, the operation pressure of the second-stage DTRO is 20-30bar, and the water produced by the two-stage DTRO is subjected to resin adsorption to remove ammonia nitrogen and then is discharged after reaching the standard. The water quality condition at each stage is as follows:
example 2
The original membrane method process of raw water of landfill leachate treated in certain landfill in Shanxi is 'raw water of leachate + basket filter + sand filtration + core filtration + two-stage DTRO + resin adsorption', because the raw water suspended solid of the leachate is higher, the sand washing is frequent, and the sulfide concentration in the raw water of the leachate is higher, and the DTRO membrane column has sulfur pollution. Then, adopting a process of 'modification pretreatment + microfiltration (immersed MBR) + two-stage DTRO + resin adsorption', adding 0.6% hydrated lime into raw leachate, stirring and reacting to obtain a leachate, and then allowing the leachate to have a pH value of 9.5 and enter a sedimentation tank for sedimentation; supernatant enters an immersed MBR unit, produced water is pumped by a self-priming pump, the operating pressure is 20-50kpa, the bottom is subjected to micropore aeration, and the aeration intensity is 100Nm 3 /h·m 2 The reflux ratio of the microfiltration concentrated water is 50 percent; and (3) the microfiltration produced water enters two stages of DTRO, the operation pressure of the first stage DTRO is 50-75bar, the operation pressure of the second stage DTRO is 20-30bar, and the two stages of DTRO produced water is subjected to resin adsorption to remove ammonia nitrogen and then is discharged after reaching the standard. The water quality condition at each stage is as follows:
corresponding to the method for treating leachate in a landfill site provided by the present invention, an embodiment of the present invention further provides a system for treating leachate in a landfill site, as shown in fig. 3, the system includes a coagulating sedimentation unit 1, a pressure filtration unit 2 and a microfiltration unit 3, raw leachate water is fed into the coagulating sedimentation unit 1, a coagulant is added into the raw leachate water for coagulating sedimentation, a supernatant water outlet end of the coagulating sedimentation unit 1 is connected with a water inlet end of the microfiltration unit 3, a precipitate outlet end of the coagulating sedimentation unit 1 is connected with an inlet end of the pressure filtration unit 2, and a water outlet end of the pressure filtration unit 2 and a concentrated water outlet end of the microfiltration unit 3 are connected with a water inlet end of the coagulating sedimentation unit 1.
In a specific embodiment, the coagulation sedimentation unit 1 specifically includes a dosing device, a stirring device and a sedimentation device, the dosing device is used for adding a coagulant into the raw leachate, the stirring device is used for stirring and reacting the raw leachate with the coagulant, and the sedimentation device is used for carrying out sedimentation separation on a mixed solution obtained after the reaction. The dosing device and the stirring device can enable the coagulant and the raw water of the percolate to carry out coagulating sedimentation, and large particle suspended matters and a part of macromolecular organic matters in the raw water of the percolate are removed through coagulating sedimentation. In a preferred embodiment, the settling device comprises a settling tank.
In a specific embodiment, a coagulant is added into the coagulating sedimentation unit 1, and then the pH value of raw leachate is adjusted to 9-9.5. In a preferred embodiment, the coagulant comprises calcium hydroxide. Calcium hydroxide may be obtained from quicklime or slaked lime. The pH value of the original percolate water is adjusted to about 9-9.5 by calcium hydroxide for coagulating sedimentation, a part of macromolecular organic matters and large suspended particles in the percolate original water are removed by coagulating sedimentation, and the percolate is adjusted to be alkaline, so that organic pollutants are adjusted to have the same electrical property as the micro-filtration membrane, the net charge quantity of the organic pollutants and the micro-filtration membrane is increased, the acting force between the membrane-pollutant and the pollutant-pollutant can be weakened, and the organic pollution of the micro-filtration unit 3 at the rear end is reduced.
In a specific embodiment, the microfiltration unit 3 can effectively retain the colloid in the percolate, remove hydrogen sulfide and provide qualified inlet water for DTRO. The microfiltration unit 3 can adopt an immersed MBR membrane component for microfiltration treatment. In a preferred embodiment, the membrane module used in the microfiltration unit 3 is a hollow fiber membrane, the material of the hollow fiber membrane is PVDF, and the filtration pore size is 0.03-0.1 μm. The PVDF hollow fiber membrane has a stain resistant effect, and can fully ensure good colloid retention and effective mud-water separation.
In a specific embodiment, the bottom of the microfiltration unit 3 is aerated with micropores. The bubbles released by aeration are mixed with the liquid part to form vortex on the surface of the membrane, the rising air scrubs and cleans the outer surface of the middle fiber outer membrane to delay membrane pollution, and meanwhile, the oxygen in aeration can oxidize hydrogen sulfide in water to slow down sulfur pollution of the DTRO unit to generate reaction O 2 +H 2 S→H 2 And O + S ↓, wherein the elemental sulfur generated by the reaction flows back to the front end along with the microfiltration concentrated water and is removed by coagulating sedimentation. The micro-filtration produced water is discharged in a self-sucking pump negative pressure suction mode, and the operation pressure is lower than 60kpa.
In a specific embodiment, the device further comprises a two-stage DTRO unit 4 and a resin adsorption unit 5, the two-stage DTRO unit 4 comprises a first-stage DTRO device and a second-stage DTRO device, the water outlet end of the produced water of the microfiltration unit 3 is connected with the water inlet end of the first-stage DTRO device, the water outlet end of the produced water of the first-stage DTRO device is connected with the water inlet end of the second-stage DTRO device, the water outlet end of the produced water of the second-stage DTRO device is connected with the water inlet end of the resin adsorption unit 5, and the concentrated water outlet end of the second-stage DTRO device is connected with the water inlet end of the first-stage DTRO device. The membrane component of the two-stage DTRO unit 4 is a disc-type structure, and has more excellent anti-pollution capability compared with a common roll-type membrane, the operation operating pressure of the first-stage DTRO is 50-75bar, the highest tolerance pressure is 90bar, the first-stage concentrated water is discharged and recharged or evaporated, the first-stage produced water enters the second-stage DTRO, the operation operating pressure of the second-stage DTRO is 20-30bar, the second-stage concentrated water flows back to the water inlet end of the first-stage DTRO, the second-stage produced water enters the resin adsorption unit, the rejection rate of the two-stage DTRO unit 4 to pollutants is high, the removal rate of COD and ammonia nitrogen is more than 99%, the produced water basically reaches the standard, only the ammonia nitrogen index is slightly high, and the produced water enters the rear-end resin adsorption unit 5 for treatment.
The embodiment of the invention discloses a method and a system for treating percolate of a refuse landfill, wherein coagulant is added into raw percolate water for coagulating sedimentation to obtain mixed liquor; carrying out filter pressing on the precipitate in the mixed solution to obtain filter-pressed effluent; performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water; and refluxing the filter-pressing effluent and the microfiltration concentrated water into raw leachate water for circulation treatment, and finally obtaining the water which reaches the standard through two-stage DTRO treatment and resin adsorption treatment. The long-term stable operation of the landfill leachate treatment system is ensured through various combined processes, and the standard discharge of the produced water of the landfill leachate is ensured. Partial organic matters and large suspended particles can be removed through coagulating sedimentation, organic pollution of a follow-up microfiltration membrane is slowed down, colloid can be effectively intercepted through microfiltration treatment, hydrogen sulfide is removed, the problems that a membrane is polluted by two-stage DTRO colloid, even a flow channel is blocked, and sulfur pollution is caused can be solved, a key effect is played on stable operation of the two-stage DTRO, and the method and the device are suitable for processing stock garbage percolate and biochemical poor aged percolate.
While the principles of the invention have been described in detail in connection with the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing embodiments are merely illustrative of exemplary implementations of the invention and are not limiting of the scope of the invention. The details of the embodiments are not to be interpreted as limiting the scope of the invention, and any obvious changes, such as equivalent alterations, simple substitutions and the like, based on the technical solution of the invention, can be interpreted without departing from the spirit and scope of the invention.
Claims (8)
1. A method for treating leachate in a refuse landfill is characterized by comprising the following steps:
s1: adding a coagulant into raw leachate to carry out coagulating sedimentation to obtain a mixed solution, wherein the raw leachate is stock landfill leachate or biochemical poor-aged leachate;
s2: performing filter pressing on the precipitate in the mixed solution to obtain filter-pressing effluent, wherein the filter-pressing effluent is subjected to plate-and-frame filter pressing in the filter-pressing process, the filter-pressing effluent flows back to the raw leachate for further modification treatment, and the supernatant in the mixed solution is subjected to microfiltration treatment;
s3: performing microfiltration treatment on the supernatant in the mixed solution to obtain microfiltration concentrated water and microfiltration produced water;
in the step S3, an immersed MBR membrane module is adopted for microfiltration treatment so as to intercept colloid in the percolate and remove hydrogen sulfide;
the membrane component adopted in the microfiltration treatment in the step S3 is a hollow fiber membrane, the hollow fiber membrane is made of PVDF, and the aperture is 0.03-0.1 mu m, so that good colloid interception and effective mud-water separation are fully ensured;
the microfiltration treatment adopts micropore aeration, and the bubble of aeration release forms the vortex through mixing on the membrane surface with liquid part, and the surface of hollow fiber membrane is scrubbed and cleaned to the air that rises, delays membrane pollution, and oxygen in the aeration is with aquatic hydrogen sulfide oxidation simultaneously, and the sulphur of rete pollutes when slowing down the DTRO and handling, and the reaction of taking place is:
O 2 +2H 2 S→2H 2 O+2S↓
the elemental sulfur generated by the reaction flows back to the front end along with the microfiltration concentrated water and is removed through coagulating sedimentation, the microfiltration produced water is discharged in a self-priming pump negative pressure suction mode, and the operating pressure is lower than 60kpa; and
performing two-stage DTRO treatment on the microfiltration produced water to improve the rejection rate of pollutants, wherein the two-stage DTRO treatment comprises first-stage DTRO treatment and second-stage DTRO treatment, the first-stage produced water obtained by the first-stage DTRO treatment is subjected to the second-stage DTRO treatment, the second-stage produced water obtained by the second-stage DTRO treatment is subjected to resin adsorption treatment to obtain final produced water, and the second-stage concentrated water obtained by the second-stage DTRO treatment is refluxed to be subjected to the first-stage DTRO treatment;
s4: and refluxing the filter-pressing effluent and the microfiltration concentrated water into the leachate raw water for circulation treatment.
2. The landfill leachate treatment method of claim 1, wherein the step S1 specifically comprises:
s11: adding a coagulant into the leachate raw water, stirring and reacting;
s12: and carrying out precipitation separation on the mixed solution obtained after the reaction.
3. The method for treating leachate in a landfill site of claim 1, wherein the pH of the raw leachate is adjusted to 9 to 9.5 after the coagulant is added in step S1.
4. The method of claim 1, wherein the coagulant comprises calcium hydroxide.
5. A landfill leachate treatment system is characterized by comprising a coagulating sedimentation unit, a filter pressing unit and a microfiltration unit, wherein leachate raw water is fed into the coagulating sedimentation unit and added with a coagulant for coagulating sedimentation, wherein the leachate raw water is stock landfill leachate or biochemical poor aged leachate, the supernatant liquid water outlet end of the coagulating sedimentation unit is connected with the water inlet end of the microfiltration unit, the precipitate outlet end of the coagulating sedimentation unit is connected with the inlet end of the filter pressing unit, and the water outlet end of the filter pressing unit and the concentrated water outlet end of the microfiltration unit are connected with the water inlet end of the coagulating sedimentation unit; the microfiltration unit is internally provided with an immersed MBR (membrane bioreactor) membrane component for microfiltration treatment, the bottom of the microfiltration unit is subjected to micropore aeration, the membrane component adopted by the microfiltration unit is a hollow fiber membrane, the hollow fiber membrane is made of PVDF (polyvinylidene fluoride), and the aperture is 0.03-0.1 mu m;
still include two-stage DTRO unit and resin adsorption unit, the two-stage DTRO unit includes one-level DTRO device and second grade DTRO device, the product water of micro-filtration unit go out the water end with the end connection of intaking of one-level DTRO device, the product water of one-level DTRO device go out the water end with the end connection of intaking of second grade DTRO device, the product water of second grade DTRO device go out the water end with the end connection of intaking of resin adsorption unit, the dense water of second grade DTRO device go out the water end with the end connection of intaking of one-level DTRO device.
6. The landfill leachate treatment system of claim 5, wherein the coagulating sedimentation unit specifically comprises a dosing device, a stirring device and a sedimentation device, the dosing device is used for adding a coagulant into the raw leachate, the stirring device is used for stirring and reacting the raw leachate with the coagulant, and the sedimentation device is used for carrying out sedimentation separation on the mixed liquor obtained after the reaction.
7. The landfill leachate treatment system of claim 5, wherein the coagulating agent is added to the coagulating sedimentation unit and then the pH value of the raw leachate is adjusted to 9-9.5.
8. The landfill leachate treatment system of claim 5, wherein the coagulant comprises calcium hydroxide.
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