CN113105073A - Leachate treatment method and system - Google Patents

Leachate treatment method and system Download PDF

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Publication number
CN113105073A
CN113105073A CN202110380477.7A CN202110380477A CN113105073A CN 113105073 A CN113105073 A CN 113105073A CN 202110380477 A CN202110380477 A CN 202110380477A CN 113105073 A CN113105073 A CN 113105073A
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percolate
leachate
coagulation
treatment
sludge
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黄高声
朱意彬
李璐
蒋荣闽
张世裕
陈志林
李斯琪
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Hanlan Huian Solid Waste Treatment Co ltd
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Hanlan Huian Solid Waste Treatment Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06—Contaminated groundwater or leachate
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/1236—Particular type of activated sludge installations
    • C02F3/1268—Membrane bioreactor systems

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  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
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  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The invention provides a leachate treatment method and a system, wherein the method comprises the following steps: dehydrating the sludge, and then filtering to obtain a leachate clear solution; calculating the number of particle collisions in the coagulation process to obtain factors influencing the coagulation rate and effect, and carrying out pretreatment to provide good conditions for coagulation treatment; adding a coagulant into the pretreated clear liquid, then stirring and precipitating, and finally filtering to obtain the pretreated percolate; then putting into a membrane system for treatment, and discharging after reaching the standard; according to the invention, by calculating the collision times of the colloidal particles, factors influencing the coagulation effect and speed are obtained and controlled, so that the coagulation effect and speed are increased; the invention reduces the content of each harmful substance in the concentrated solution, increases the treatability and reduces the post-treatment cost by carrying out coagulation pretreatment on the percolate stock solution; the effluent quality of the sewage treatment method provided by the invention can stably meet the requirements.

Description

Leachate treatment method and system
Technical Field
The invention relates to the field of garbage treatment, in particular to a leachate treatment method and system.
Background
The garbage leachate is the garbage which is extruded when being buried and is subjected to biodegradation and chemical degradation along with the garbage, and the infiltration of groundwater and rainwater, etc., and a liquid containing high concentration of organic matter, inorganic matter and suspended matter, which is generated along with the aggravation of water resource shortage and increasingly serious environmental pollution, in order to meet the continuously improved drinking water standard of people, the membrane technology is continuously developed, the membrane technology is regarded as a technology with strong practicability in sewage treatment and recycling, but has a part of defects that the membrane technology is inevitable, the osmotic pressure generated when inflow water pollutants with high concentration exist is high, and the raw leachate contains a large amount of suspended matters, if the suspended matters are not removed, the impurity removal treatment in the next step not only needs more raw materials, but also influences the effect of further treatment.
The principle of the membrane separation technology is that wastewater passes through a filter membrane, and macromolecular particles are intercepted, so that water passes through the process, and the membrane separation technology mainly comprises the following steps: nanofiltration (NF), Reverse Osmosis (RO), Ultrafiltration (UF) and the like, and the membrane treatment process has the advantages of good treatment effect, capability of continuous treatment, stronger impact resistance on the quality and quantity of inlet water, stable running state and the like; but also has the disadvantages of high treatment cost and easy blockage and pollution of the filter membrane.
Disclosure of Invention
The invention aims to provide a percolate treatment method and a percolate treatment system, which are used for solving the problems of high membrane treatment cost and easy blockage and pollution of a filter membrane in the prior art.
In order to achieve the above purpose, the invention provides the following technical scheme:
a leachate treatment process, said process comprising the steps of:
dehydrating the sludge to extract leachate, and then filtering the leachate to obtain leachate clear liquid;
pretreating the leachate clear solution;
adding a coagulant into the pretreated clear percolate, stirring, precipitating, and filtering to obtain a primarily treated percolate;
and putting the percolate subjected to coagulation treatment into a membrane system for treatment, and discharging after reaching the standard.
In the above aspect, it is preferable that the dewatering of the sludge includes the steps of: the method comprises the steps of conveying sludge in a sludge storage pool to a dehydrator, separating the sludge from percolate, conveying a dewatered mud cake to a landfill for landfill, conveying the separated percolate to a basket filter by using a terrain gravity faucet, filtering and intercepting suspended particles larger than 3mm, intercepting and filtering the percolate by using a sand filter to remove fine suspended matters, and enabling the turbidity of effluent to be smaller than 5 NTU.
In any of the above embodiments, preferably, the pre-treating of the percolate clear solution comprises the steps of: the particle collision frequency in the coagulation process is calculated to obtain factors influencing the coagulation rate and effect, and the specific calculation is as follows:
in the anisotropic agglomeration process, the rate of change of the colloid concentration is calculated by the formula:
Figure BDA0003012735330000021
in the formula: k is a radical ofpFor the rate constant, the calculation formula is as follows: k is a radical ofp＝8αp*Dbπ a; in the formula: dbIs the particle size, a is the fraction of collisions occurring, alphapIs the Brownian motion diffusion coefficient;
obtained by the stokes formula:
Figure BDA0003012735330000022
in the formula: mu is the viscosity coefficient of water, k is the Boltzmann constant, and T is the absolute temperature;
thereby obtaining
Figure BDA0003012735330000023
Thereby obtaining the number of particle collisions resulting from brownian motion:
Figure BDA0003012735330000024
in the process of homodromous agglomeration, the number of times of mutual collision of colloidal particles under the stirring action in unit time is
Figure BDA0003012735330000025
In the formula: n is1，n2Two particle concentrations, i.e. the number of particles per unit volume; r is1，r2Two particle diameters in m; du/dt is the velocity gradient G, in S-1。
In any of the above embodiments, preferably, the pre-treating the percolate clear solution further comprises the steps of: firstly, regulating the pH value of the clear percolate solution to 6, then regulating the temperature of the clear percolate solution, regulating the temperature of the clear percolate solution to 30 ℃, and finally adding a coagulant aid PAM (1%) into the clear percolate solution, wherein the adding amount of the coagulant aid PAM (1%) is 1.5 ml/L.
In any of the above schemes, preferably, the step of adding coagulant into the pretreated clear percolate solution comprises the following steps: adding a coagulant FPS according to the volume of the landfill leachate to be treated, wherein the dosage of the coagulant FPS is 6g/L, and stirring the mixture in a way that: firstly stirring rapidly for 2min at a stirring speed of 300r/min, then stirring slowly for 10min at a stirring speed of 50r/min, and finally precipitating for 30 min.
In any of the above schemes, preferably, the membrane system comprises an external MBR membrane bioreactor, the external MBR membrane bioreactor consists of a bioreactor and a membrane module, and the membrane is installed inside the water outlet end of the bioreactor.
In any of the above schemes, preferably, the membrane system further includes an NF system and an RO system, and the leachate treated by the external MBR membrane bioreactor enters the NF system to be treated, and is treated by the NF system and finally treated by the RO system.
In any of the above aspects, it is preferred that a leachate treatment system, the system comprising:
the sludge dewatering and filtering module is used for dewatering sludge, extracting percolate and filtering the percolate to obtain percolate clear liquid;
the adjusting module comprises an adjusting tank and is used for preprocessing the percolate clear liquid;
the coagulation treatment module comprises a coagulation tank, a stirring device, a sedimentation tank and a filtering device, and is used for adding a coagulant into the pretreated percolate clear liquid, stirring, precipitating, and filtering to obtain pretreated percolate;
and the membrane treatment module comprises an external MBR, an NF system and an RO system, and is used for carrying out membrane system treatment on the percolate after coagulation treatment so as to realize discharge after reaching the standard.
In any of the above schemes, preferably, the sludge dewatering module comprises a sludge storage tank, a dewatering machine, a basket filter and a sand filter, the sludge storage tank is communicated with the input end of the dewatering machine through a pipeline and a water pump, the water outlet end of the dewatering machine is communicated with the water inlet end of the basket filter through a terrain gravity faucet, and the water outlet pipe of the basket filter is communicated with the water inlet pipe of the sand filter.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, factors influencing coagulation effect and speed are obtained by calculating the collision times of the colloidal particles, and the coagulation effect and speed are increased by controlling the influencing factors; the invention further treats the leachate of the refuse landfill by adding an NF system and an RO system behind a Membrane Bioreactor (MBR), so that the effluent quality meets the discharge standard; the invention improves the biodegradability of the stock solution and reduces the load of the filter membrane and the yield of the concentrated solution in the later period by carrying out coagulation pretreatment on the stock solution of the percolate; the invention reduces the content of each harmful substance in the concentrated solution, increases the treatability and reduces the post-treatment cost by carrying out coagulation pretreatment on the percolate stock solution; the effluent quality of the landfill leachate treated by the sewage treatment method provided by the invention can stably meet the requirements of the pollution control standard of domestic garbage landfill, and the sewage treatment combined process has wide popularization prospect.
Drawings
In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
Fig. 1 is a flow chart of a leachate treatment method provided in this embodiment;
fig. 2 is a schematic view of a leachate treatment system according to this embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
For better understanding of the above technical solutions, the technical solutions of the present invention will be described in detail below with reference to the drawings and the detailed description of the present invention.
A method of treating leachate, the method comprising the following steps.
Step one, sludge is dehydrated, leachate is extracted, and then the leachate is filtered to obtain leachate clear liquid.
Specifically, the sludge in the sludge storage pool is transported to a dehydrator, the sludge and the percolate are separated, a mud cake after dehydration is sent to a landfill site for landfill, the percolate after separation is sent to a basket filter by using a terrain gravity faucet, suspended particles larger than 3mm are filtered and intercepted, and fine suspended matters are removed by intercepting and filtering through a sand filter, so that the effluent turbidity is less than 5 NTU.
The garbage leachate is the garbage which is extruded when being buried and is subjected to biodegradation and chemical degradation along with the garbage, and the infiltration of groundwater and rainwater, etc., and a liquid containing high concentration of organic matter, inorganic matter and suspended matter, which is generated along with the aggravation of water resource shortage and increasingly serious environmental pollution, in order to meet the continuously improved drinking water standard of people, the membrane technology is continuously developed, the membrane technology is regarded as a technology with strong practicability in sewage treatment and recycling, but has a part of defects that the membrane technology is inevitable, the osmotic pressure generated when inflow water pollutants with high concentration exist is high, and the raw leachate contains a large amount of suspended matters, if the suspended matters are not removed, the impurity removal treatment in the next step not only needs more raw materials, but also influences the effect of further treatment.
And step two, pretreating the leachate clear solution to provide good conditions for coagulation treatment.
Specifically, at first, calculate the granule number of times of collision among the coagulation process to obtain the factor that influences coagulation rate and effect, then adjust the factor that influences coagulation rate and effect, the accommodation process includes: firstly, regulating the pH value of the clear percolate solution to 6, then regulating the temperature of the clear percolate solution, regulating the temperature of the clear percolate solution to 30 ℃, and finally adding a coagulant aid PAM (1%) into the clear percolate solution, wherein the adding amount of the coagulant aid PAM (1%) is 1.5 ml/L.
Coagulation mainly comprises two processes of flocculation and coagulation, wherein flocculation refers to a process that colloid in water is destabilized under the action of a flocculating agent and colloidal particles collide with each other to form a floc by Brownian motion, and is also called anisotropic coagulation, and in the coagulation process, mechanical stirring is required to accelerate the colloidal particles to collide with each other, which is called isotropic coagulation; in the course of anisotropic agglomeration, the total mass of the colloid is constant, and its concentration n (number of particles per unit volume) decreases with time, at the following rate:
Figure BDA0003012735330000061
in the formula: k is a radical ofpFor the rate constant, the calculation formula is as follows: k is a radical ofp＝8αp*Dbπa；
In the formula: dbIs the particle size, a is the fraction of collisions occurring, alphapIs the brownian motion diffusion coefficient.
Obtained by the stokes formula:
Figure BDA0003012735330000062
in the formula: mu is the viscosity coefficient of water, k is the Boltzmann constant, and T is the absolute temperature;
thereby obtaining
Figure BDA0003012735330000063
Thereby obtaining the number of particle collisions resulting from brownian motion:
Figure BDA0003012735330000064
it can be seen that the number of particle collisions is proportional to the square of the particle concentration and the water temperature, independent of particle size.
In the process of equidirectional agglomeration, the number of times that colloidal particles collide with each other under the stirring action in unit time is as follows:
Figure BDA0003012735330000065
in the formula: n is1，n2Two particle concentrations, i.e. the number of particles per unit volume; r is1，r2Two particle diameters in m; du/dt is the velocity gradient G, in S-1(ii) a Therefore, the particle collision frequency is related to the diameter and concentration of particles in water, and in addition, the influence of the water flow shearing force on flocs is realized, and the larger the particle size is, the higher the probability of floc breakage is.
Coagulation is a process that stable colloid and tiny suspended matters in water are destabilized under the action of a coagulant, and destabilized particles are coagulated into flocs after mutual collision, and researches show that coagulation is comprehensively summarized into four aspects: compressing double electric layers, adsorbing electric neutralization, adsorbing bridging and rolling sweeping, when a coagulant PFS is used for treating landfill leachate stock solution, if the pH value is lower, hydrolysis reaction of hydrated iron complex ions is difficult to occur, so that the coagulation effect is poor, at the moment, the pH value is properly increased, a large amount of coordination hydrolysis reaction of the complex ions in water occurs, iron hydroxide precipitates are generated, and other insoluble particles in water are rolled and swept in the process of precipitation, so that COD (chemical oxygen demand) and other substances in water are removed, but when the pH value is too high, on one hand, the precipitate in water can be partially dissolved, the rolling sweeping capacity is reduced, on the other hand, a complex which is the same as the charged particles in water can be formed, so that the particles after destabilization in water are subjected to a restabilization phenomenon, and are difficult to remove.
The coagulant is greatly influenced by temperature when the landfill leachate stock solution is treated, on one hand, the reactions of the coagulant during the treatment of the landfill leachate are mostly endothermic reactions, so that when the temperature is lower, the hydrolysis of the coagulant is limited, the year of the produced water is larger, the brownian motion of colloidal particles is weaker, and the effective collision of the colloidal particles is reduced, so that the coagulation effect is poor, and on the other hand, the proper action of colloidal particles is weakened, so that the adhesive strength between the coagulant and the colloidal particles is lower, so that the flocs in the water grow slowly and loosely, and the coagulation efficiency is reduced and the coagulation effect is poor; when the water temperature is too high, on one hand, the floccule formed by the coagulant is loose and difficult to precipitate due to the excessively high hydrolysis speed of the coagulant, so that the coagulation effect is poor, and on the other hand, the coagulant is in a high molecular structure, so that the coagulant is aged or decomposed at high temperature, insoluble substances are formed, precipitates with high water content and large volume are easy to generate, and the treatment cost is increased.
The coagulant aid is added into water to improve floc structures and increase coagulation effect through an action mechanism of adsorption bridging, the coagulant aid PAM is a high molecular substance with a chain structure, a large number of active groups exist on the molecules of the coagulant aid PAM, when the leachate is subjected to coagulation treatment, a proper amount of PAM is added, the coagulant produces adsorption bridging effect, fine and loose floc particles are enabled to become thick and dense, particulate matters in the water are removed, when the addition is excessive, on one hand, the particles can be surrounded by partial high molecular chains, the particles are stable due to no adsorption positions, the destabilization phenomenon of the destabilized particles in the water is enabled to occur, the particles are difficult to remove, on the other hand, the excessive coagulant aid can increase the viscosity of the water body, and the subsequent treatment process is unfavorable.
And step three, adding a coagulant into the pretreated percolate clear liquid, then stirring and precipitating, and finally filtering to obtain the pretreated percolate.
Specifically, a coagulant FPS is added according to the volume of the landfill leachate to be treated, the dosage of the coagulant FPS is 6g/L, and the stirring mode is as follows: stirring rapidly for 2min at 300r/min, stirring slowly for 10min at 50r/min, and precipitating for 30 min.
The coagulant PFS is a cationic coagulant, the surface has a large number of positively charged active groups and complex ions, when the coagulant FPS is used for coagulating landfill leachate stock solution, when the adding amount of the PFS is less than 6g/L, the coagulation sedimentation is facilitated to be fully carried out, the surface active groups and negatively charged particles are mutually adsorbed, formed flocs are fine and dense, the boundaries between the flocs and the water surface are clear, along with the increase of the adding amount, when the adding amount of the PFS is more than 6g/L, the surfaces of the particles have insufficient space for adsorption with the coagulant, and the collision probability of solid particles is increased, so that part of colloid is electrified again to generate a re-stabilization phenomenon.
The stirring mode is an important condition for successful flocculation, and in order to create proper hydrodynamic conditions and optimal stirring time, the stirring is divided into two stages according to the early-stage pre-experimental result, wherein the first stage is called rapid stirring or rapid stirring, and the main purpose of the first stage is to ensure that a coagulant is distributed in water more quickly and completely and is contacted with organic matters in the water, and meanwhile, the stirring can ensure that floccules are compact; the second stage is called slow stirring or flocculation stirring, and the slow stirring influences the collision times of flocculation particles and the adsorption and bridging effect, so that the growth of flocs is promoted. Above all, the slow stirring can reduce the water flow speed, and avoid the crushing of the growing flocs due to the flow velocity to influence the coagulation effect.
When the garbage leachate is treated by using a coagulant FPS, when the settling time reaches a certain value, the removal rate is slowly increased along with the increase of the time, because after the stirring is stopped, the floccules generate a velocity gradient due to the action of hydraulic rotation inertia, colloid particles are further collided and aggregated under different settling speeds to form floccule groups, the settling speed is continuously increased, so that the settling occurs, the concentration of the colloid particles in the leachate is very low in the later stage of the settling, the number of times of collision among the particles is reduced, the settling speed can be slowly reduced until the particles settle at a constant speed, the stage is a free settling stage, the settling time is longer and longer along with the decrease of the concentration of the particles in the leachate, in the actual engineering, the settling time is too short, the content of the particles in the effluent is higher, the subsequent treatment load is increased, the settling time is longer, although the quality of the effluent is better, but the occupied area of the sedimentation tank needs to be increased, and the investment cost is increased.
And step four, putting the percolate subjected to coagulation treatment into a membrane system for treatment so as to achieve discharge after reaching the standard.
Specifically, the membrane system is an MBR (membrane bioreactor) which comprises a bioreactor and a membrane module, the membrane is arranged inside the water outlet end of the bioreactor, a substrate is in contact with a large amount of microorganisms inside the bioreactor, organic pollutants are degraded by oxidative decomposition of the microorganisms in the growth and reproduction processes, solid-liquid separation of sludge mixed liquor and wastewater is realized through the sludge mixed liquor membrane module, and in order to maintain the number of the microorganisms within a certain range, the concentrated sludge is returned to the bioreactor.
As a further step, MRB treatment cannot enable water quality to be stably discharged up to the standard, fine treatment is needed after water outlet of an MBR system, according to the existing treatment technology, the outlet water can be deeply treated through an NF or RO system, and as the smaller the membrane aperture in the reverse osmosis process is, the stronger the interception capacity is, heavy metals, salts and other pollutants in the water can be effectively removed through the treatment of the NF system and the treatment of the RO system, and the up to the standard discharge can be realized.
A leachate treatment system, the system comprising:
the sludge dewatering and filtering module is used for dewatering sludge, extracting percolate and filtering the percolate to obtain percolate clear liquid;
the adjusting module comprises an adjusting tank and is used for pretreating the percolate clear solution and providing good conditions for coagulation treatment;
the coagulation treatment module comprises a coagulation tank, a stirring device, a sedimentation tank and a filtering device, and is used for adding a coagulant into the pretreated percolate clear liquid, then carrying out sedimentation after stirring, and finally obtaining the pretreated percolate after filtering;
and the membrane treatment module comprises an external MBR, an NF system and an RO system, and is used for carrying out membrane system treatment on the percolate after coagulation treatment so as to realize discharge after reaching the standard.
As a further step, the sludge dewatering module comprises a sludge storage pool, a dewatering machine, a basket filter and a sand filter, the sludge storage pool is communicated with the input end of the dewatering machine through a pipeline and a water suction pump, the water outlet end of the dewatering machine is communicated with the water inlet end of the basket filter through a terrain gravity faucet, and the water outlet pipe of the basket filter is communicated with the water inlet pipe of the sand filter.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, factors influencing coagulation effect and speed are obtained by calculating the collision times of the colloidal particles, and the coagulation effect and speed are increased by controlling the influencing factors; the invention further treats the leachate of the refuse landfill by adding an NF system and an RO system behind a Membrane Bioreactor (MBR), so that the effluent quality meets the discharge standard; the invention improves the biodegradability of the stock solution and reduces the load of the filter membrane and the yield of the concentrated solution in the later period by carrying out coagulation pretreatment on the stock solution of the percolate; the invention reduces the content of each harmful substance in the concentrated solution, increases the treatability and reduces the post-treatment cost by carrying out coagulation pretreatment on the percolate stock solution; the effluent quality of the landfill leachate treated by the sewage treatment method provided by the invention can stably meet the requirements of the pollution control standard of domestic garbage landfill, and the sewage treatment combined process has wide popularization prospect.
Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that various changes, modifications and substitutions can be made without departing from the spirit and scope of the invention as defined by the appended claims. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A leachate treatment method, characterized in that said method comprises the following steps:
dehydrating the sludge, extracting percolate, and filtering the percolate to obtain percolate clear solution;
pretreating the leachate clear solution;
adding a coagulant into the pretreated clear percolate, stirring, precipitating, and filtering to obtain a primarily treated percolate;
and putting the percolate subjected to coagulation treatment into a membrane system for treatment, and discharging after reaching the standard.
2. The leachate treatment method according to claim 1, wherein the dewatering of the sludge comprises the steps of: and (2) transporting the sludge in the sludge storage tank to a dehydrator, separating the sludge from the percolate, delivering the dewatered sludge cake to a landfill for landfill, delivering the separated percolate to a basket filter by using a terrain gravity faucet, filtering and intercepting suspended particles larger than 3mm, and intercepting and filtering by using a sand filter to remove fine suspended matters.
3. The leachate treatment method according to claim 2, wherein the pretreatment of the leachate supernatant comprises the steps of: the particle collision frequency in the coagulation process is calculated to obtain factors influencing the coagulation rate and effect, and the concrete calculation is as follows:
in the anisotropic agglomeration process, the rate of change of the colloid concentration is calculated by the formula:
Figure FDA0003012735320000011
in the formula: k is a radical ofpIs a rate constant, rate constant kpThe calculation formula is as follows: k is a radical ofp＝8αp*Dbπ a; in the formula: dbIs the particle size, a is the fraction of collisions occurring, alphapIs the Brownian motion diffusion coefficient;
obtained by the stokes formula:
Figure FDA0003012735320000012
in the formula: mu is the viscosity coefficient of water, k is the Boltzmann constant, and T is the absolute temperature;
thereby obtaining
Figure FDA0003012735320000013
Thereby obtaining the number of particle collisions resulting from brownian motion:
Figure FDA0003012735320000014
in the process of homodromous agglomeration, the number of times of mutual collision of the colloidal particles under the stirring action in unit time is
Figure FDA0003012735320000015
In the formula: n is1，n2Two particle concentrations, i.e. the number of particles per unit volume; r is1，r2Two particle diameters in m; du/dt is the velocity gradient G, in S-1。
4. The leachate treatment method of claim 3, wherein the pre-treating of the leachate supernatant further comprises the steps of: adjusting the pH value of the clear percolate solution to 6, adjusting the temperature of the clear percolate solution to 30 ℃, adding a coagulant aid PAM into the clear percolate solution, wherein the concentration of the coagulant aid is 1%, and the adding amount of the coagulant aid PAM is 1.5 ml/L.
5. The leachate treatment method according to claim 4, wherein the step of adding coagulant to the pretreated leachate supernatant comprises the steps of: adding a coagulant FPS according to the volume of the landfill leachate to be treated, wherein the dosage of the coagulant FPS is 6g/L, and stirring the mixture in a way that: firstly stirring rapidly for 2min at a stirring speed of 300r/min, then stirring slowly for 10min at a stirring speed of 50r/min, and finally precipitating for 30 min.
6. The leachate treatment method of claim 5, wherein the membrane system comprises an external MBR membrane bioreactor, and the external MBR membrane bioreactor comprises a bioreactor and a membrane module, and the membrane is installed inside the outlet end of the bioreactor.
7. The leachate treatment method of claim 6, wherein the membrane system further comprises an NF system and an RO system, and the leachate treated by the external MBR membrane bioreactor enters the NF system for treatment and is treated by the RO system after being treated by the NF system.
8. The leachate treatment system of claim 1, wherein said leachate treatment system comprises:
the sludge dewatering and filtering module is used for dewatering sludge, extracting percolate and filtering the percolate to obtain percolate clear liquid;
the adjusting module comprises an adjusting tank and is used for preprocessing the percolate clear liquid;
the coagulation treatment module comprises a coagulation tank, a stirring device, a sedimentation tank and a filtering device, and is used for adding a coagulant into the pretreated percolate clear liquid, stirring, precipitating, and filtering to obtain pretreated percolate;
and the membrane treatment module comprises an external MBR, an NF system and an RO system, and is used for performing membrane system treatment on the percolate after coagulation treatment and discharging the percolate after reaching the standard.
9. The leachate treatment system of claim 8, wherein the sludge dewatering module comprises a sludge storage tank, a dewatering machine, a basket filter and a sand filter, the sludge storage tank is communicated with the input end of the dewatering machine through a pipeline and a water pump, the water outlet end of the dewatering machine is communicated with the water inlet end of the basket filter through a terrain gravity faucet, and the water outlet pipe of the basket filter is communicated with the water inlet pipe of the sand filter.
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