CN111704301A - Landfill leachate treatment process based on PMVR-ZLD - Google Patents

Landfill leachate treatment process based on PMVR-ZLD Download PDF

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CN111704301A
CN111704301A CN202010611190.6A CN202010611190A CN111704301A CN 111704301 A CN111704301 A CN 111704301A CN 202010611190 A CN202010611190 A CN 202010611190A CN 111704301 A CN111704301 A CN 111704301A
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stock solution
separation
pump
solution
evaporation
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苏宏伟
孙全婷
戚志忠
雷彪
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Qingyuan Environmental Construction Guangzhou Co ltd
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Qingyuan Environmental Construction Guangzhou Co ltd
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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00Multistage treatment of water, waste water or sewage
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00Treatment of sludge; Devices therefor
    • C02F11/12Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/02Treatment of water, waste water, or sewage by heating
    • C02F1/04Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/043Details
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/02Treatment of water, waste water, or sewage by heating
    • C02F1/04Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/048Purification of waste water by evaporation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/02Treatment of water, waste water, or sewage by heating
    • C02F1/04Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/06Flash evaporation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/44Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56Macromolecular compounds
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/66Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F2001/007Processes including a sedimentation step
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06Contaminated groundwater or leachate

Abstract

The invention belongs to the technical field of garbage wastewater treatment, and particularly relates to a PMVR-ZLD-based garbage leachate treatment process, which comprises the following steps: collecting stock solution, pretreating, preheating, evaporating and separating, performing advanced treatment, solidifying and the like. The invention adopts a coagulating sedimentation system in the pretreatment, thereby effectively solving the problem of unstable operation of the device caused by blockage; by adopting the MVR forced circulation evaporation separation system, the leachate is subjected to wastewater evaporation, so that the problems of heat transfer coefficient reduction, energy consumption increase, evaporator blockage and shutdown are avoided; the evaporation effluent is treated by adopting the advanced treatment system, so that the cost is greatly reduced; through adopting landfill leachate zero release processing system, carry out evaporation separation to the leachate, the crystallization of production solidifies into the brick, and landfill treatment again does not influence into water quality, all adopts the concentrated recharge form more has the advantage than the waste water treatment to the leachate at present.

Description

Landfill leachate treatment process based on PMVR-ZLD
Technical Field
The invention belongs to the technical field of garbage wastewater treatment, and particularly relates to a PMVR-ZLD-based garbage leachate treatment process.
Background
The landfill leachate is sewage generated in the landfill reservoir area during the landfill process, and also comprises car washing wastewater, road washing wastewater and the like; factors influencing the production amount of the leachate are various, wherein the main source of the landfill leachate is rainfall infiltration, in addition, moisture contained in the garbage and waste liquid generated by anaerobic decomposition are also provided, and meanwhile, the landfill age, the garbage compaction degree, the garbage property, the pore water content of a garbage pile, atmospheric evaporation, whether underground water is infiltrated or not and the like can influence the water amount of the leachate to a certain extent.
The water quality of the landfill leachate is quite complex, and the landfill leachate generally contains high-concentration COD, heavy metal salts, SS and ammonia nitrogen and has the characteristics of high hardness and the like; the CODcr and BOD5 in the landfill leachate have the highest concentration of tens of thousands mg/L, and compared with municipal sewage, the concentration is very high. The high-concentration landfill leachate is mainly generated in an acid fermentation stage, the pH value reaches or is slightly lower than 7, the COD of low-molecular fatty acid accounts for more than 80% of the total amount of the COD, and the ratio of the BOD5 to the COD is 0.5-0.6.
The quality of landfill leachate varies greatly, and the main components of the landfill leachate include the following four types:
common elements and ions such as Cd, Mg, Fe, Na, NH3-N, carbonate, chloride ions and the like;
② trace metals such as Mn, Cr, Ni, Pb, etc.;
metering organic matters, common TOC and COD, and independently metering phenol and the like;
and fourthly, microorganisms.
The nature of the percolate is related to various factors such as the type and the nature of landfill waste, the landfill mode and the like, the chemical composition changes greatly, the concentration and the nature of the percolate have a highly dynamic change relationship with time and mainly depend on the service life of a landfill and the stage of the landfill when sampling;
in the early stage of landfill, the concentration of the organic acid in the percolate is higher, the content of the volatile organic acid is less than 1 percent, and the proportion of the volatile organic acid is increased along with the time;
in the acid phase of the landfill, the pH value is lower, and the contents of BOD5, TOC, COD, nutrients and heavy metals are higher;
in the methanogenesis stage of the landfill, the pH value is between 6.5 and 7.5, the contents of BOD5, TOC, COD and nutrients are obviously reduced, and the content of heavy metals is also obviously reduced.
The composition analysis of the leachate of domestic established refuse disposal sites has the following composition changes:
the pH value is 6-7 at the initial stage of landfill, is weakly acidic, and can be increased to 7-8 to be weakly alkaline as time goes on.
The BOD in the leachate is gradually increased along with the increase of time and microbial activity, the highest peak value is reached after the leachate is generally buried for 6 months to 2.5 years, the BOD mainly takes the solubility at the moment, and then the index begins to decline until the landfill is stabilized for 6 to 15 years;
COD is slightly lower than BOD in the initial stage of landfill, and the COD dropping rate is lower than the BOD dropping rate and is slightly higher than BOD instead along with the lapse of time.
The ammonia nitrogen concentration of the percolate increases along with the increase of the landfill years and can reach more than 2000mg/L, and the imbalance of the C/N ratio in the percolate can reduce the biological treatment effect; for biochemical treatment, the ratio of the appropriate nutrient elements in the sewage is BOD5: N: P is 100:5:1, while the ratio of BOD5/TP in general landfill leachate is relatively large and is greatly different from phosphorus element required by microorganism growth, so that phosphorus element is often lacked in biochemical treatment of leachate and needs to be supplemented;
if a large amount of metal wastes are mixed in the garbage, the garbage leachate contains more than ten metal ions, exceeds the general discharge standard and needs to be treated; therefore, metal wastes are strictly forbidden when garbage enters a field, so that the content of metals in the leachate is extremely low, and only dilution treatment or no treatment is carried out.
In order to overcome the water quality characteristics of the landfill leachate, the water quality is discharged according with the pollutant control standard of the domestic garbage landfill (GB16889-2008), therefore, the treatment process of the landfill leachate is needed to treat the leachate, but the existing landfill leachate treatment process has many problems, the evaporation, concentration and crystallization of the wastewater can not be carried out to produce salt, so that the solidification, brick formation and landfill treatment can not be carried out, further influencing the quality of inlet water, and in addition, the method has the problems of high energy consumption, low efficiency, high cost, unsafe operation and low on-line rate, therefore, the invention provides a PMVR-ZLD-based landfill leachate treatment process, which has the advantages of capability of evaporating, concentrating and crystallizing wastewater to produce salt, effective scaling, reduction of system operation energy consumption, reduction of operation cost, safe and reliable operation, high online rate, good operability and operation flexibility.
Disclosure of Invention
Technical problem to be solved
In order to overcome many problems of the landfill leachate treatment process, such as incapability of evaporating, concentrating, crystallizing and salting the wastewater, incapability of solidifying into bricks and performing landfill treatment, further influencing the quality of inlet water, and the problems of high energy consumption, low efficiency, high cost, unsafe operation and low online rate, the invention provides the landfill leachate treatment process based on PMVR-ZLD, which has the advantages of capability of evaporating, concentrating, crystallizing and salting the wastewater, effective scaling, reduction of system operation energy consumption, reduction of operation cost, safe and reliable operation, high online rate and good operability and operation flexibility.
(II) technical scheme
The invention is realized by the following technical scheme: the invention provides a landfill leachate treatment process based on PMVR-ZLD, which comprises the following steps:
a) collecting stock solution: the landfill leachate is used as stock solution and enters a stock solution pool for collection;
b) pretreatment: the feed liquid pump extracts the stock solution in the stock solution tank and conveys the stock solution into the integrated coagulating sedimentation system for treatment, at the moment, the integrated dosing system can put the coagulant PAC and the PAM into the integrated coagulating sedimentation system, the integrated coagulating sedimentation system can stir the coagulant PAC, the PAM and the stock solution to enable coagulation and chemical reaction to occur, the coagulant PAC, the PAM and the stock solution are mutually adsorbed and combined to form larger particles and precipitate, meanwhile, the stock solution after coagulation and chemical reaction directly enters a subsequent inclined tube sedimentation tank for precipitation to form slurry, the slurry is conveyed into a sludge concentration tank for further concentration through a sludge discharge pump, finally, the slurry is subjected to sludge-water separation through a plate frame dehydrator to form stock solution supernatant and dry sludge, the dry sludge is directly transported and buried outside, the stock solution supernatant enters a middle temporary storage tank, sulfuric acid is added into the middle temporary storage tank through the integrated dosing system, and the PH is adjusted to 5, changing NH3-N of the stock solution supernatant into NH4 +; finishing the pretreatment of the stock solution;
c) preheating: after the pretreatment of the stock solution is finished, the stock solution is extracted from the middle temporary storage tank by an MVR (mechanical vapor recompression) delivery pump and delivered into a heat exchanger, at the moment, the distilled water in the distilled water tank enters the heat exchanger through the extraction of a distilled water pump to exchange heat with the stock solution, the stock solution is preheated, and the temperature is raised to be close to the boiling point temperature;
d) evaporation and separation: an MVR forced circulation evaporation separation system is adopted, after preheating, stock solution with the temperature slightly lower than the boiling point is in an unsaturated state, the stock solution in the unsaturated state tangentially enters an upper laminar flow bed of a crystallizer and is mixed with supersaturated circulation solution containing a large number of fine crystals, the mixture is distributed into each heat exchange tube through a forced circulation pump, the flow rate is controlled to be 1.5 m/s-3.5 m/s, when the circulation solution flows from the tubes at a high speed, the circulation solution is heated and heated by heat generated by condensation of steam outside the heat exchange tubes, the pressure in the tubes is controlled to be higher than the saturated steam pressure at the temperature, concentrated brine does not boil in the tubes and is not evaporated in the tubes, the heated circulation solution flows out of a heater into a low-pressure separation chamber, and because the separation pressure is suddenly reduced, the high-temperature concentrated brine is flashed in the separation chamber, the brine is concentrated and crystallized and separated out, and directly rushes to the bottom of the crystallizer along a precipitation, uniformly turning to rise through a specially designed distributor, fully contacting supersaturated solution with suspended crystal nuclei in the rising process to enable the crystal nuclei to grow, eliminating supersaturation, treating the crystals through a crystallizer, wherein the particle diameters from bottom to top are well-graded, larger granular crystals are pumped out by a concentrated solution pump to a subsequent centrifugal separation system for treatment, and supernatant of the crystallizer is pumped out by a forced circulation pump to a heater for continuous circulation and evaporation; the concentrated solution pump pumps the crystal slurry of larger crystal particles of the crystallizer to be conveyed in a pipeline, after the crystal slurry is concentrated and crystallized to a design value through the evaporator, strong brine containing crystals pumped out by the concentrated solution pump enters a solid-liquid separator to be subjected to solid-liquid separation, and part of mother solution flows back to a separation chamber to be mixed with indoor solution and is continuously evaporated; part of mother liquor is sent to a curing system for treatment;
e) deep treatment: the distilled water treated by the MVR evaporation system is removed with more than 99% of salt, a small amount of ammonia nitrogen is remained, the distilled water needs to enter an RO system for treatment, before entering the RO system, the distilled water is firstly adjusted to have pH value which is acidic, the ammonia nitrogen exists in the water in the form of ammonium salt, the effluent quality of the RO system is improved, and finally the produced water is discharged in a qualified mode.
f) And (3) curing: the concentrated solution after the over-circulation evaporation separation is evaporated to a certain degree along with the increase of the concentration, when the high COD of the enriched impurities affects the normal evaporation separation, the crystallized substances and a small amount of high-concentration mother liquor pass through a sludge solidification stabilizing system, the mother liquor is solidified by adopting cement and a chelating agent, and the solidified mother liquor is sent to a landfill area for landfill.
Further, the integrated dosing system in the step b): the device is used for pretreatment dosing and is provided with a storage tank, a stirrer and a dosing pump for sulfuric acid, PAC and PAM;
the integrated coagulating sedimentation system in the step b): used for pretreatment reaction precipitation, is provided with 2 reaction tanks, 1 inclined tube precipitation tank and corresponding stirrers.
Further, the MVR delivery pump in the step c) is a VFD control feed liquid delivery pump, and the frequency is 0-50 Hz;
after the preheating of the raw liquid in the step c) is finished, preheating is also carried out through an exhaust condenser.
Further, said crystallizer in step d) takes the form of a salt leg crystallizer designed as a fluidized bed crystallizer with size classification.
Furthermore, the forced circulation pump in the step d) is controlled by adopting a VFD (vacuum frequency converter), the system is initially started to run, the TDS (total dissolved solids) of the system solution is low, the specific gravity is low, the frequency is automatically adjusted within the range of 0-50 Hz according to the automatic detection of the specific gravity and the outlet pressure, and the circulation flow demand is met;
the secondary steam generated in the separation chamber in the step d) passes through a high-efficiency demisting system with quite sufficient liquid-vapor separation area and separation height, the high-efficiency demisting system is provided with two layers, one layer adopts a folded plate type demister, the second layer adopts a wire mesh type demister, a PLC (programmable logic controller) is arranged for automatically controlling regular product water cleaning demisting net arrangement, the secondary steam is pumped out by a compressor for temperature rise and pressure rise after passing through the high-efficiency demisting system, and the steam after temperature rise is used as an evaporation heat source of a heater; distilled water condensed by the heater is stored in a distilled water tank, is conveyed by a distilled water pump to exchange heat with the stock solution, and is discharged out of the system; the system is provided with a BPE online monitoring instrument for automatically detecting BPE changes; the distilled water removing system adopts VFD to control the frequency of the distilled water pump to be automatically adjusted within the range of 0-50 Hz.
Further, the conveying pipeline of the crystal slurry in the step d) is designed by adopting a circulating pipeline, the pipeline is designed by adopting a multi-flange mode, and an automatic flushing system is arranged in the circulating pipeline.
Furthermore, the MVR forced circulation evaporation separation system in the step d and the emptying port of the crystal slurry are both provided with a reflux backflushing design.
Further, the curing system in the step d) is provided with a mixing stirrer and a dosing machine.
(III) advantageous effects
Compared with the prior art, the invention has the following beneficial effects:
the invention can evaporate, concentrate and crystallize the wastewater to produce salt, effectively aims at scaling, reduces the energy consumption of system operation, reduces the operation cost, has safe and reliable operation and high online rate, and has the effects of good operability and operation flexibility.
1. In order to recover heat to the maximum extent, the water inlet plate of the evaporation system adopts a high-efficiency plate heat exchanger, the plate heat exchanger has the advantages of high heat exchange efficiency, small occupied area and narrow flow channel, is easy to block and is suitable for water quality without SS and colloid, and aiming at the problem, the invention adopts a coagulating sedimentation pretreatment system to remove SS and colloid in waste water and keep the stability of the plate heat exchanger so as to avoid unstable operation of the device caused by blocking.
2. The garbage leachate contains a large amount of hardness ions such as Ca, Mg and Si and a large amount of difficultly volatile COD (chemical oxygen demand), inorganic scale and organic scale are formed in an evaporation system, a conventional evaporation system generally adopts a horizontal pipe spraying falling film system to treat the leachate for concentration, the leachate is uniformly sprayed on the surface of a heat exchange pipe for heat exchange and then is evaporated, the inorganic scale and the organic scale are easily attached to the surface of the heat exchange pipe for scaling, so that the problems of heat transfer coefficient reduction, energy consumption increase and the like are caused, the whole evaporator is seriously blocked and stopped, and aiming at the problems, the invention adopts an MVR forced circulation evaporation separation system to evaporate the wastewater of the leachate.
The system adopts a forced circulation evaporation separation system as follows: the evaporation process with the strongest scale resistance and adaptability can ensure the long-time on-line operation of the system, and the circulation in the process equipment mainly depends on forced flow generated by external power. The circulation speed can reach 1.5-3.5 m/s, the heat transfer efficiency and the production capacity are higher, and the continuous operation can be carried out for more than 3 months.
3. In order to ensure the quality of the effluent, the subsequent system adopts a membrane advanced treatment system to treat the evaporated effluent, the salt content of the evaporated effluent is low, and the recovery rate can reach more than 96 percent. Compared with the conventional method of adopting sulfuric acid to wash steam, the method has low manufacturing cost, does not need a high-temperature resistant dilute sulfuric acid washing tower (generally needs to use zirconium materials), and needs to consider the subsequent treatment of the ammonium sulfate solution of the produced water.
4. At present, the waste water treatment of the percolate adopts a concentration recharge mode, so that the percolate in a landfill is worse and is difficult to treat due to vicious circulation.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic flow chart of the present invention.
FIG. 2 is a process flow diagram of the MVR evaporation separation system of the present invention.
FIG. 3 is a schematic diagram of a forced circulation evaporative separation system of the present invention.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. 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.
A landfill leachate treatment process based on PMVR-ZLD comprises the following steps:
a) collecting stock solution: the landfill leachate is used as stock solution and enters a stock solution pool for collection;
b) pretreatment: the feed liquid pump extracts the stock solution in the stock solution tank and conveys the stock solution into the integrated coagulating sedimentation system for treatment, at the moment, the integrated dosing system can put the coagulant PAC and the PAM into the integrated coagulating sedimentation system, the integrated coagulating sedimentation system can stir the coagulant PAC, the PAM and the stock solution to enable coagulation and chemical reaction to occur, the coagulant PAC, the PAM and the stock solution are mutually adsorbed and combined to form larger particles and precipitate, meanwhile, the stock solution after coagulation and chemical reaction directly enters a subsequent inclined tube sedimentation tank for precipitation to form slurry, the slurry is conveyed into a sludge concentration tank for further concentration through a sludge discharge pump, finally, the slurry is subjected to sludge-water separation through a plate frame dehydrator to form stock solution supernatant and dry sludge, the dry sludge is directly transported and buried outside, the stock solution supernatant enters a middle temporary storage tank, sulfuric acid is added into the middle temporary storage tank through the integrated dosing system, and the PH is adjusted to 5, changing NH3-N of the stock solution supernatant into NH4 +; finishing the pretreatment of the stock solution;
c) preheating: after the pretreatment of the stock solution is finished, the stock solution is extracted from the middle temporary storage tank by an MVR (mechanical vapor recompression) delivery pump and delivered into a heat exchanger, at the moment, the distilled water in the distilled water tank enters the heat exchanger through the extraction of a distilled water pump to exchange heat with the stock solution, the stock solution is preheated, and the temperature is raised to be close to the boiling point temperature;
d) evaporation and separation: an MVR forced circulation evaporation separation system is adopted, after preheating, stock solution with the temperature slightly lower than the boiling point is in an unsaturated state, the stock solution in the unsaturated state tangentially enters an upper laminar flow bed of a crystallizer and is mixed with supersaturated circulation solution containing a large number of fine crystals, the mixture is distributed into each heat exchange tube through a forced circulation pump, the flow rate is controlled to be 1.5 m/s-3.5 m/s, when the circulation solution flows from the tubes at a high speed, the circulation solution is heated and heated by heat generated by condensation of steam outside the heat exchange tubes, the pressure in the tubes is controlled to be higher than the saturated steam pressure at the temperature, concentrated brine does not boil in the tubes and is not evaporated in the tubes, the heated circulation solution flows out of a heater into a low-pressure separation chamber, and because the separation pressure is suddenly reduced, the high-temperature concentrated brine is flashed in the separation chamber, the brine is concentrated and crystallized and separated out, and directly rushes to the bottom of the crystallizer along a precipitation, uniformly turning to rise through a specially designed distributor, fully contacting supersaturated solution with suspended crystal nuclei in the rising process to enable the crystal nuclei to grow, eliminating supersaturation, treating the crystals through a crystallizer, wherein the particle diameters from bottom to top are well-graded, larger granular crystals are pumped out by a concentrated solution pump to a subsequent centrifugal separation system for treatment, and supernatant of the crystallizer is pumped out by a forced circulation pump to a heater for continuous circulation and evaporation; the concentrated solution pump pumps the crystal slurry of larger crystal particles of the crystallizer to be conveyed in a pipeline, after the crystal slurry is concentrated and crystallized to a design value through the evaporator, strong brine containing crystals pumped out by the concentrated solution pump enters a solid-liquid separator to be subjected to solid-liquid separation, and part of mother solution flows back to a separation chamber to be mixed with indoor solution and is continuously evaporated; part of mother liquor is sent to a curing system for treatment;
e) deep treatment: the distilled water treated by the MVR evaporation system is removed with more than 99% of salt, a small amount of ammonia nitrogen is remained, the distilled water needs to enter an RO system for treatment, before entering the RO system, the distilled water is firstly adjusted to have an acidic pH value, the ammonia nitrogen exists in the water in the form of ammonium salt, the effluent quality of the RO system is improved, and finally the produced water is discharged in a qualified way;
f) and (3) curing: the concentrated solution after the over-circulation evaporation separation is evaporated to a certain degree along with the increase of the concentration, when the normal evaporation separation is influenced by the high COD of the enriched impurities, the crystallized substances and a small amount of high-concentration mother liquor pass through a sludge solidification and stabilization system, the mother liquor is solidified by adopting cement and a chelating agent, and the solidified mother liquor is sent to a landfill area for landfill;
the integrated dosing system in the step b): the device is used for pretreatment dosing and is provided with a storage tank, a stirrer and a dosing pump for sulfuric acid, PAC and PAM;
the integrated coagulating sedimentation system in the step b): used for pretreatment reaction precipitation, 2 reaction tanks, 1 inclined tube precipitation tank and corresponding stirrers are arranged;
the MVR delivery pump in the step c) is a VFD control feed liquid delivery pump, and the frequency is 0-50 Hz;
after the preheating of the raw liquid in the step c) is finished, preheating the raw liquid by an exhaust condenser; the exhaust condenser recovers the energy of the steam exhausted out of the system along with the non-condensable gas, so as to achieve the aim of reducing steam loss and minimizing heat loss;
the crystallizer in the step d) is in a salt leg crystallizer mode, and the salt leg crystallizer is designed into a fluidized bed crystallizer with granularity grading;
the forced circulation pump in the step d) is controlled by VFD, the system is started to operate initially, the TDS of the system solution is low, the specific gravity is small, the frequency is automatically regulated within the range of 0-50 Hz according to the automatic detection of the specific gravity and the outlet pressure, and the circulation flow demand is met;
the secondary steam generated in the separation chamber in the step d) passes through a high-efficiency demisting system with quite sufficient liquid-vapor separation area and separation height, the high-efficiency demisting system is provided with two layers, one layer adopts a folded plate type demister, the second layer adopts a wire mesh type demister, a PLC (programmable logic controller) is arranged for automatically controlling regular product water cleaning demisting net arrangement, the secondary steam is pumped out by a compressor for temperature rise and pressure rise after passing through the high-efficiency demisting system, and the steam after temperature rise is used as an evaporation heat source of a heater; distilled water condensed by the heater is stored in a distilled water tank, is conveyed by a distilled water pump to exchange heat with the stock solution, and is discharged out of the system; the system is provided with a BPE online monitoring instrument for automatically detecting BPE changes; the distilled water discharge system adopts VFD to control the frequency of a distilled water pump to be automatically adjusted within the range of 0-50 Hz; the VFD (variable frequency control) is adopted, so that the energy consumption is saved, and the VFD is different from the VFD which is controlled by a regulating valve in that the full-frequency full-load operation of a pump is not needed, the abrasion loss of the pump is reduced, and the replacement cost of spare parts is reduced;
the conveying pipeline of the crystal slurry in the step d) is designed by adopting a circulating pipeline, the pipeline is designed by adopting a multi-flange design, and an automatic flushing system is arranged in the circulating pipeline; the circulating pipeline is designed, the pipeline flow channel is large, the flow rate is high, the number of elbows is small, particles are prevented from settling on the pipeline, the circulating pipeline is provided with an automatic flushing system, the pipeline can be flushed by dilution when the machine is stopped, and the blockage caused by settling and caking is prevented;
meanwhile, the pipeline adopts a multi-flange design, and is easy to disassemble and clean;
in the step d), the MVR forced circulation evaporation separation system and the emptying port of the crystal slurry are both provided with a reflux backflushing design;
the curing system in the step d) is provided with a mixing stirrer and a dosing machine.
1. In order to recover heat to the maximum extent, the water inlet plate of the evaporation system adopts a high-efficiency plate heat exchanger, the plate heat exchanger has the advantages of high heat exchange efficiency, small occupied area and narrow flow channel, is easy to block and is suitable for water quality without SS and colloid, and aiming at the problem, the invention adopts a coagulating sedimentation pretreatment system to remove SS and colloid in waste water and keep the stability of the plate heat exchanger so as to avoid unstable operation of the device caused by blocking.
2. The garbage leachate contains a large amount of hardness ions such as Ca, Mg and Si and a large amount of difficultly volatile COD (chemical oxygen demand), inorganic scale and organic scale are formed in an evaporation system, a conventional evaporation system generally adopts a horizontal pipe spraying falling film system to treat the leachate for concentration, the leachate is uniformly sprayed on the surface of a heat exchange pipe for heat exchange and then is evaporated, the inorganic scale and the organic scale are easily attached to the surface of the heat exchange pipe for scaling, so that the problems of heat transfer coefficient reduction, energy consumption increase and the like are caused, the whole evaporator is seriously blocked and stopped, and aiming at the problems, the invention adopts an MVR forced circulation evaporation separation system to evaporate the wastewater of the leachate.
The system adopts a forced circulation evaporation separation system as follows: the evaporation process with the strongest scale resistance and adaptability can ensure the long-time on-line operation of the system, and the circulation in the process equipment mainly depends on forced flow generated by external power. The circulation speed can reach 1.5-3.5 m/s, the heat transfer efficiency and the production capacity are higher, and the continuous operation can be carried out for more than 3 months.
3. In order to ensure the quality of the effluent, the subsequent system adopts a membrane advanced treatment system to treat the evaporated effluent, the salt content of the evaporated effluent is low, and the recovery rate can reach more than 96 percent. Compared with the conventional method of adopting sulfuric acid to wash steam, the method has low manufacturing cost, does not need a high-temperature resistant dilute sulfuric acid washing tower (generally needs to use zirconium materials), and needs to consider the subsequent treatment of the ammonium sulfate solution of the produced water.
4. At present, the waste water treatment of the percolate adopts a concentration recharge mode, so that the percolate in a landfill is worse and is difficult to treat due to vicious circulation.
Untreated and treated leachate analysis reports:
taking out the landfill leachate to analyze main components, and the following table shows the components:
serial number Index (I) Unit of Data of Remarks for note
1 Appearance of the product / Black solution
2 PH / 8.24
3 TDS mg/L 52750
4 COD mg/L 10895
5 Ammonia nitrogen mg/L 5367.3
6 SS mg/L 1000
The landfill leachate is subjected to the treatment of the invention, and the main components are analyzed, and the following table shows the component report:
serial number Index (I) Unit of Data of Remarks for note
1 Appearance of the product / Slightly turbid solution
2 PH / 6.03
3 TDS mg/L 563
4 COD mg/L 85
5 Ammonia nitrogen mg/L 13.89
Compared with the two tables, the water quality is greatly improved, and the discharge can be carried out according with the pollutant control standard of the household garbage landfill (GB 16889-2008).
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may include only a single embodiment, and such description is for clarity only, and those skilled in the art will be able to make the description as a whole, and the embodiments may be appropriately combined to form other embodiments as will be apparent to those skilled in the art.

Claims (8)

1. A landfill leachate treatment process based on PMVR-ZLD is characterized in that: comprises the following steps:
a) collecting stock solution: the landfill leachate is used as stock solution and enters a stock solution pool for collection;
b) pretreatment: the feed liquid pump extracts the stock solution in the stock solution tank and conveys the stock solution into the integrated coagulating sedimentation system for treatment, at the moment, the integrated dosing system can put the coagulant PAC and the PAM into the integrated coagulating sedimentation system, the integrated coagulating sedimentation system can stir the coagulant PAC, the PAM and the stock solution to enable coagulation and chemical reaction to occur, the coagulant PAC, the PAM and the stock solution are mutually adsorbed and combined to form larger particles and precipitate, meanwhile, the stock solution after coagulation and chemical reaction directly enters a subsequent inclined tube sedimentation tank for precipitation to form slurry, the slurry is conveyed into a sludge concentration tank for further concentration through a sludge discharge pump, finally, the slurry is subjected to sludge-water separation through a plate frame dehydrator to form stock solution supernatant and dry sludge, the dry sludge is directly transported and buried outside, the stock solution supernatant enters a middle temporary storage tank, sulfuric acid is added into the middle temporary storage tank through the integrated dosing system, and the PH is adjusted to 5, changing NH3-N of the stock solution supernatant into NH4 +; finishing the pretreatment of the stock solution;
c) preheating: after the pretreatment of the stock solution is finished, the stock solution is extracted from the middle temporary storage tank by an MVR (mechanical vapor recompression) delivery pump and delivered into a heat exchanger, at the moment, the distilled water in the distilled water tank enters the heat exchanger through the extraction of a distilled water pump to exchange heat with the stock solution, the stock solution is preheated, and the temperature is raised to be close to the boiling point temperature;
d) evaporation and separation: an MVR forced circulation evaporation separation system is adopted, after preheating, stock solution with the temperature slightly lower than the boiling point is in an unsaturated state, the stock solution in the unsaturated state tangentially enters an upper laminar flow bed of a crystallizer and is mixed with supersaturated circulation solution containing a large number of fine crystals, the mixture is distributed into each heat exchange tube through a forced circulation pump, the flow rate is controlled to be 1.5 m/s-3.5 m/s, when the circulation solution flows from the tubes at a high speed, the circulation solution is heated and heated by heat generated by condensation of steam outside the heat exchange tubes, the pressure in the tubes is controlled to be higher than the saturated steam pressure at the temperature, concentrated brine does not boil in the tubes and is not evaporated in the tubes, the heated circulation solution flows out of a heater into a low-pressure separation chamber, and because the separation pressure is suddenly reduced, the high-temperature concentrated brine is flashed in the separation chamber, the brine is concentrated and crystallized and separated out, and directly rushes to the bottom of the crystallizer along a precipitation, uniformly turning to rise through a specially designed distributor, fully contacting supersaturated solution with suspended crystal nuclei in the rising process to enable the crystal nuclei to grow, eliminating supersaturation, treating the crystals through a crystallizer, wherein the particle diameters from bottom to top are well-graded, larger granular crystals are pumped out by a concentrated solution pump to a subsequent centrifugal separation system for treatment, and supernatant of the crystallizer is pumped out by a forced circulation pump to a heater for continuous circulation and evaporation; the concentrated solution separating pump pumps the crystal slurry of larger crystal particles of the crystallizer to convey in a pipeline, after the crystal slurry is concentrated and crystallized to a design value through an evaporator, strong brine containing crystals pumped out by the concentrated solution pump enters a solid-liquid separator to carry out solid-liquid separation, part of mother solution flows back to a separation chamber to be mixed with indoor solution, and evaporation is continuously carried out; part of mother liquor is sent to a curing system for treatment;
e) deep treatment: the distilled water treated by the MVR evaporation system is removed with more than 99% of salt, a small amount of ammonia nitrogen is remained, the distilled water needs to enter an RO system for treatment, before entering the RO system, the distilled water is firstly adjusted to have pH value which is acidic, the ammonia nitrogen exists in the water in the form of ammonium salt, the effluent quality of the RO system is improved, and finally the produced water is discharged in a qualified mode.
f) And (3) curing: the concentrated solution after the over-circulation evaporation separation is evaporated to a certain degree along with the increase of the concentration, when the high COD of the enriched impurities affects the normal evaporation separation, the crystallized substances and a small amount of high-concentration mother liquor pass through a sludge solidification stabilizing system, the mother liquor is solidified by adopting cement and a chelating agent, and the solidified mother liquor is sent to a landfill area for landfill.
2. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein:
the integrated dosing system in the step b): the device is used for pretreatment dosing and is provided with a storage tank, a stirrer and a dosing pump for sulfuric acid, PAC and PAM;
the integrated coagulating sedimentation system in the step b): used for pretreatment reaction precipitation, is provided with 2 reaction tanks, 1 inclined tube precipitation tank and corresponding stirrers.
3. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein;
the MVR delivery pump in the step c) is a VFD control feed liquid delivery pump, and the frequency is 0-50 Hz;
after the preheating of the raw liquid in the step c) is finished, preheating is also carried out through an exhaust condenser.
4. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein: the crystallizer in the step d) is in the form of a salt leg crystallizer, and the salt leg crystallizer is designed to be a fluidized bed crystallizer with granularity grading.
5. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein:
the forced circulation pump in the step d) is controlled by VFD, the system is started to operate initially, the TDS of the system solution is low, the specific gravity is small, the frequency is automatically regulated within the range of 0-50 Hz according to the automatic detection of the specific gravity and the outlet pressure, and the circulation flow demand is met;
the secondary steam generated in the separation chamber in the step d) passes through a high-efficiency demisting system with quite sufficient liquid-vapor separation area and separation height, the high-efficiency demisting system is provided with two layers, one layer adopts a folded plate type demister, the second layer adopts a wire mesh type demister, a PLC (programmable logic controller) is arranged for automatically controlling regular product water cleaning demisting net arrangement, the secondary steam is pumped out by a compressor for temperature rise and pressure rise after passing through the high-efficiency demisting system, and the steam after temperature rise is used as an evaporation heat source of a heater; distilled water condensed by the heater is stored in a distilled water tank, is conveyed by a distilled water pump to exchange heat with the stock solution, and is discharged out of the system; the system is provided with a BPE online monitoring instrument for automatically detecting BPE changes; the distilled water removing system adopts VFD to control the frequency of the distilled water pump to be automatically adjusted within the range of 0-50 Hz.
6. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein: and d) the conveying pipeline of the crystal slurry in the step d) is designed by adopting a circulating pipeline, the pipeline is designed by adopting a plurality of flanges, and an automatic flushing system is arranged in the circulating pipeline.
7. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein: and d), setting reflux backflushing design for the MVR forced circulation evaporation separation system and the emptying port of the crystal slurry in the step d).
8. The PMVR-ZLD based landfill leachate treatment process according to claim 1, wherein: the curing system in the step d) is provided with a mixing stirrer and a dosing machine.
CN202010611190.6A 2020-06-30 2020-06-30 Landfill leachate treatment process based on PMVR-ZLD Pending CN111704301A (en)

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CN112794580A (en) * 2021-01-12 2021-05-14 无锡朗盼环境科技有限公司 Landfill leachate treatment and discharge process
CN113354008A (en) * 2021-06-01 2021-09-07 光大环保(中国)有限公司 Landfill leachate evaporation mother liquor treatment process
CN113716784A (en) * 2021-09-14 2021-11-30 湖南天为环保科技有限公司 Pretreatment composition for high-concentration landfill leachate membrane concentrated solution and application thereof
CN114634271A (en) * 2022-02-09 2022-06-17 中创水务科技环保(广东)有限公司 Waste water zero-discharge treatment process for garbage transfer station
CN114699779A (en) * 2022-04-26 2022-07-05 镇江新区固废处置股份有限公司 Low-temperature evaporation and concentration device for waste water heat pump and waste water treatment process
CN114835338A (en) * 2022-04-24 2022-08-02 东莞市新东欣环保投资有限公司 Method for treating percolate concentrated solution of refuse landfill
CN117088449A (en) * 2023-10-19 2023-11-21 福州科煌生态环保科技有限公司 Direct contact type evaporator for garbage leachate membrane concentrate treatment

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CN110759571A (en) * 2019-10-31 2020-02-07 广东闻扬环境科技有限公司 Fly ash leachate treatment system and treatment method
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CN110759568A (en) * 2019-10-24 2020-02-07 广东闻扬环境科技有限公司 Recovery system and recovery method for potassium perchlorate and sodium chloride crystal salt in wastewater
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Cited By (9)

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Publication number Priority date Publication date Assignee Title
CN112794580A (en) * 2021-01-12 2021-05-14 无锡朗盼环境科技有限公司 Landfill leachate treatment and discharge process
CN113354008A (en) * 2021-06-01 2021-09-07 光大环保(中国)有限公司 Landfill leachate evaporation mother liquor treatment process
CN113716784A (en) * 2021-09-14 2021-11-30 湖南天为环保科技有限公司 Pretreatment composition for high-concentration landfill leachate membrane concentrated solution and application thereof
CN113716784B (en) * 2021-09-14 2023-12-29 湖南天为环保科技有限公司 Pretreatment composition for high-concentration landfill leachate membrane concentrate and application thereof
CN114634271A (en) * 2022-02-09 2022-06-17 中创水务科技环保(广东)有限公司 Waste water zero-discharge treatment process for garbage transfer station
CN114835338A (en) * 2022-04-24 2022-08-02 东莞市新东欣环保投资有限公司 Method for treating percolate concentrated solution of refuse landfill
CN114699779A (en) * 2022-04-26 2022-07-05 镇江新区固废处置股份有限公司 Low-temperature evaporation and concentration device for waste water heat pump and waste water treatment process
CN117088449A (en) * 2023-10-19 2023-11-21 福州科煌生态环保科技有限公司 Direct contact type evaporator for garbage leachate membrane concentrate treatment
CN117088449B (en) * 2023-10-19 2024-01-12 福州科煌生态环保科技有限公司 Direct contact type evaporator for garbage leachate membrane concentrate treatment

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Application publication date: 20200925