Disclosure of Invention
The invention aims at overcoming the defects of the prior art and provides a method and a system for reducing landfill leachate concentrated solution. The system and the method not only enable the landfill leachate concentrated solution to be further reduced under lower operating pressure and reduce subsequent treatment cost, but also improve the quality of produced water, ensure that the effluent is discharged after reaching standards stably, and also have the advantages of low energy consumption, high pollution resistance and the like, and solve the problems of membrane pollution and high energy consumption.
In order to achieve the above object, according to one aspect of the present invention, there is provided a landfill leachate concentrate reduction system including a nanofiltration unit, a filtration unit, an acid adjustment unit, a forward osmosis unit and a high salt concentration unit connected in sequence;
the nanofiltration unit is connected with the filtration unit through a first concentrated solution water tank and a first feed pump;
the acid adjusting unit comprises an acid adjusting water tank, an acid mixing pump, a dosing device, a pH controller and a second feeding pump; the dosing device comprises a metering pump, a Y-shaped filter and a dosing box which are connected in sequence; the water inlet and outlet pipes of the mixed acid pump are connected with the acid regulating water tank, and the water outlet pipe of the mixed acid pump is also connected with the metering pump; the metering pump and the pH controller are used for adjusting the pH value of the solution in the acid adjusting water tank;
the forward osmosis unit comprises a forward osmosis water inlet tank, a third feed pump, a multi-section forward osmosis component, a second concentrated solution water tank, a drawing liquid water inlet pump, a drawing liquid concentrated water tank and a drawing liquid dilute water tank;
the multistage forward osmosis components are sequentially connected and are used for realizing the stage-by-stage concentration of the feed liquid and the stage-by-stage dilution of the drawing liquid; each section of forward osmosis component of the multi-section forward osmosis component comprises a feed liquid circulating pump, a forward osmosis membrane component and a drawing liquid circulating pump; the liquid circulating pump is connected with the liquid side of the forward osmosis membrane component, and the liquid drawing circulating pump is connected with the liquid drawing side of the forward osmosis membrane component;
the second feed pump, the forward osmosis feed water tank, the third feed pump and the feed water inlet pipe of the feed water circulating pump of the first section of forward osmosis assembly are sequentially connected; the second concentrated solution water tank is connected with a feed liquid concentration pipe of a feed liquid circulating pump of the last section of forward osmosis assembly;
the drawing liquid concentrated water tank, the drawing liquid water inlet pump and the drawing liquid concentrated water pipe of the drawing liquid circulating pump of the last section of forward osmosis component are connected in sequence; the drawing liquid thin water tank is connected with a drawing liquid thin water pipe of a drawing liquid circulating pump of the first section of forward osmosis assembly;
the high-salt concentration unit comprises a fourth feed pump, a first-stage nanofiltration device, a first-stage water production tank, a fifth feed pump, a second-stage nanofiltration device, a second-stage water production tank, a sixth feed pump and a reverse osmosis device which are connected in sequence, and optionally comprises a drawing liquid solute supplementing device; the nanofiltration unit is connected with the secondary water production tank through a nanofiltration water production pipe; the drawing liquid thin water tank is respectively connected with the fourth feed pump and the secondary nanofiltration device, and the drawing liquid solute supplementing device is arranged on one side of the drawing liquid thin water tank opposite to the fourth feed pump; the first-stage nanofiltration device is also connected with the draw solution concentrated water tank; the reverse osmosis device is also connected with the primary water production tank.
The invention also provides a method for reducing the landfill leachate concentrated solution, which adopts the landfill leachate concentrated solution reducing system and comprises the following steps:
s1: delivering pretreated landfill leachate into the nanofiltration unit, delivering the obtained landfill leachate concentrated solution into the first concentrated solution water tank after nanofiltration separation, and delivering the obtained nanofiltration product water into the second-stage product water tank;
s2: sequentially sending the landfill leachate concentrated solution in the first concentrated solution water tank into the filtering unit and the acid adjusting unit, and sequentially removing suspended matters and adjusting the pH value of the liquid;
s3: sending the liquid subjected to pH adjustment treatment into a forward osmosis water inlet tank of the forward osmosis unit, further sending the liquid into the first section forward osmosis assembly, correspondingly sending the drawing liquid from the drawing liquid concentrated water tank to the last section forward osmosis assembly of the forward osmosis unit, sending the forward osmosis concentrated liquid obtained by the last section forward osmosis assembly into the second concentrated liquid water tank after multistage forward osmosis treatment, carrying out evaporation or incineration treatment, and sending the drawing liquid diluent obtained by the first section forward osmosis assembly into the drawing liquid diluted water tank;
s4: sending the drawing liquid diluent from the drawing liquid thin water tank to a first-stage nanofiltration device of the high-salt concentration unit, carrying out first-stage concentration treatment, then, refluxing the obtained first-stage concentrated liquid to the drawing liquid thick water tank, sending the obtained first-stage produced water to the first-stage produced water tank, then, sending the obtained first-stage produced water to the second-stage nanofiltration device, carrying out second-stage concentration treatment, refluxing the obtained second-stage concentrated liquid to the drawing liquid thin water tank, sending the obtained second-stage produced water to the second-stage produced water tank, sending the obtained second-stage produced water and the nanofiltration produced water to the reverse osmosis device, carrying out third-stage concentration treatment, refluxing the obtained third-stage concentrated liquid to the first-stage produced water tank, and discharging the obtained third-stage produced water;
if the TDS of the solution in the dilute draw solution tank does not reach the TDS percentage requirement range of the water inlet of the first-stage nanofiltration device, the solution TDS in the dilute draw solution tank is supplemented by the draw solution solute supplementing device, so that the first-stage concentration treatment is carried out.
The technical scheme of the invention has the following beneficial effects:
(1) The invention has low requirement on the water quality of the inlet water, wide water quality application range and small influence of water quality fluctuation on the system operation;
(2) The invention can resist dirt blocking, has light membrane pollution, low chemical cleaning frequency and long service life of the membrane;
(3) The system has low operating pressure, low energy consumption and low operating cost;
(4) The invention has high recovery rate and concentration decrement and has the advantages;
(5) The invention has simple process, high automation degree and low requirement on the level of operators;
(6) The produced water is stable and reaches the standard.
(7) The system and method of the present invention solve two key technical problems: firstly, the membrane pollution problem is that on the forward osmosis side, the complex water quality is faced, and the chemical pressure (osmotic pressure difference) is utilized to carry out concentration and decrement, so that the mechanical pressure is reduced, and the membrane pollution is slowed down; on the draw solution recovery side, the membrane pollution level is still light even under high mechanical pressure because of the single component (sodium chloride) facing; secondly, the problem of high energy consumption: according to the osmotic pressure calculation formula pi= cRT, if a reverse osmosis membrane is adopted, the concentration of sodium chloride at the concentrated water side can reach 10% at the condition of 120bar of water inlet pressure; in the invention, the operating pressure is reduced on the drawing liquid side by reducing the osmotic pressure difference between the concentrated water side and the water producing side, and in theory, 14% concentration of sodium chloride can be realized under the pressure of 70bar, so that the energy consumption is reduced. In addition, the nanofiltration produced water enters a high-salt concentration unit, so that on one hand, part of salt is recovered, and on the other hand, the quality of the produced water is improved, and the produced water is stable and reaches the standard.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention are described below, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The invention provides a landfill leachate concentrated solution reducing system which comprises a nanofiltration unit, a filtration unit, an acid regulation unit, a forward osmosis unit and a high-salt concentration unit which are connected in sequence;
the nanofiltration unit is connected with the filtration unit through a first concentrated solution water tank and a first feed pump;
the acid adjusting unit comprises an acid adjusting water tank, an acid mixing pump, a dosing device, a pH controller and a second feeding pump; the dosing device comprises a metering pump, a Y-shaped filter and a dosing box which are connected in sequence; the water inlet and outlet pipes of the mixed acid pump are connected with the acid regulating water tank, and the water outlet pipe of the mixed acid pump is also connected with the metering pump; the metering pump and the pH controller are used for adjusting the pH value of the solution in the acid adjusting water tank;
the forward osmosis unit comprises a forward osmosis water inlet tank, a third feed pump, a multi-section forward osmosis component, a second concentrated solution water tank, a drawing liquid water inlet pump, a drawing liquid concentrated water tank and a drawing liquid dilute water tank;
the multistage forward osmosis components are sequentially connected and are used for realizing the stage-by-stage concentration of the feed liquid and the stage-by-stage dilution of the drawing liquid; each section of forward osmosis component of the multi-section forward osmosis component comprises a feed liquid circulating pump, a forward osmosis membrane component and a drawing liquid circulating pump; the liquid circulating pump is connected with the liquid side of the forward osmosis membrane component, and the liquid drawing circulating pump is connected with the liquid drawing side of the forward osmosis membrane component;
the second feed pump, the forward osmosis feed water tank, the third feed pump and the feed water inlet pipe of the feed water circulating pump of the first section of forward osmosis assembly are sequentially connected; the second concentrated solution water tank is connected with a feed liquid concentration pipe of a feed liquid circulating pump of the last section of forward osmosis assembly;
the drawing liquid concentrated water tank, the drawing liquid water inlet pump and the drawing liquid concentrated water pipe of the drawing liquid circulating pump of the last section of forward osmosis component are connected in sequence; the drawing liquid thin water tank is connected with a drawing liquid thin water pipe of a drawing liquid circulating pump of the first section of forward osmosis assembly;
the high-salt concentration unit comprises a fourth feed pump, a first-stage nanofiltration device, a first-stage water production tank, a fifth feed pump, a second-stage nanofiltration device, a second-stage water production tank, a sixth feed pump and a reverse osmosis device which are connected in sequence, and optionally comprises a drawing liquid solute supplementing device; the nanofiltration unit is connected with the secondary water production tank through a nanofiltration water production pipe; the drawing liquid thin water tank is respectively connected with the fourth feed pump and the secondary nanofiltration device, and the drawing liquid solute supplementing device is arranged on one side of the drawing liquid thin water tank opposite to the fourth feed pump; the first-stage nanofiltration device is also connected with the draw solution concentrated water tank; the reverse osmosis device is also connected with the primary water production tank.
In the invention, in order to avoid the too large difference of the salt concentration of the feed liquid side and the salt concentration of the drawing liquid side (if the difference is too large, the phenomenon of internal concentration polarization is easy to occur, and the decrease of the produced water flux and the membrane fouling are caused), the multistage forward osmosis component is adopted, so that the stage-by-stage concentration of the feed liquid and the stage-by-stage dilution of the drawing liquid are realized.
According to the present invention, preferably, the forward osmosis membrane module comprises a forward osmosis membrane element, a membrane shell and a water inlet and outlet valve; the forward osmosis membrane element comprises a forward osmosis membrane and a diversion net bonded with the forward osmosis membrane; the area of the forward osmosis membrane is determined by the membrane flux and the amount of feed liquid treated by the forward osmosis membrane.
According to the present invention, preferably, the filtration unit is a bag filter, a disc self-cleaning filter or a tube micro-filter.
According to the present invention, preferably, the tubular microfiltration device comprises a two or three reaction tanks, a tubular membrane concentration tank, a circulating pump, a tubular membrane module, a chemical cleaning system and a water production tank.
According to the invention, preferably, the feed liquid inlet pipe and the feed liquid concentration pipe of the feed liquid circulating pump are both connected to the feed liquid side of the forward osmosis membrane assembly, and the draw liquid concentrated water pipe and the draw liquid dilute water pipe of the draw liquid circulating pump are both connected to the draw liquid side of the forward osmosis membrane assembly.
According to the invention, preferably, the lower part of the primary nanofiltration device is connected with the draw solution concentrate tank through a primary nanofiltration concentrate pipe; the drawing liquid dilute water tank is connected with the secondary nanofiltration device through a secondary nanofiltration concentrated liquid pipe; the reverse osmosis device is connected with the primary water production tank through a tertiary nanofiltration concentrated solution pipe.
The invention also provides a method for reducing the landfill leachate concentrated solution, which adopts the landfill leachate concentrated solution reducing system and comprises the following steps:
s1: delivering pretreated landfill leachate into the nanofiltration unit, delivering the obtained landfill leachate concentrated solution into the first concentrated solution water tank after nanofiltration separation, and delivering the obtained nanofiltration product water into the second-stage product water tank;
s2: sequentially sending the landfill leachate concentrated solution in the first concentrated solution water tank into the filtering unit and the acid adjusting unit, and sequentially removing suspended matters and adjusting the pH value of the liquid;
s3: sending the liquid subjected to pH adjustment treatment into a forward osmosis water inlet tank of the forward osmosis unit, further sending the liquid into the first section forward osmosis assembly, correspondingly sending the drawing liquid from the drawing liquid concentrated water tank to the last section forward osmosis assembly of the forward osmosis unit, sending the forward osmosis concentrated liquid obtained by the last section forward osmosis assembly into the second concentrated liquid water tank after multistage forward osmosis treatment, carrying out evaporation or incineration treatment, and sending the drawing liquid diluent obtained by the first section forward osmosis assembly into the drawing liquid diluted water tank;
s4: sending the drawing liquid diluent from the drawing liquid thin water tank to a first-stage nanofiltration device of the high-salt concentration unit, carrying out first-stage concentration treatment, then, refluxing the obtained first-stage concentrated liquid to the drawing liquid thick water tank, sending the obtained first-stage produced water to the first-stage produced water tank, then, sending the obtained first-stage produced water to the second-stage nanofiltration device, carrying out second-stage concentration treatment, refluxing the obtained second-stage concentrated liquid to the drawing liquid thin water tank, sending the obtained second-stage produced water to the second-stage produced water tank, sending the obtained second-stage produced water and the nanofiltration produced water to the reverse osmosis device, carrying out third-stage concentration treatment, refluxing the obtained third-stage concentrated liquid to the first-stage produced water tank, and discharging the obtained third-stage produced water;
if the TDS of the solution in the dilute draw solution tank does not reach the TDS percentage requirement range of the water inlet of the first-stage nanofiltration device, the solution TDS in the dilute draw solution tank is supplemented by the draw solution solute supplementing device, so that the first-stage concentration treatment is carried out.
In the invention, the pretreatment in the step S1 is a treatment process of an adjusting tank, pretreatment and biochemical treatment.
According to the present invention, preferably, the filtration accuracy of the filtration unit is 50 μm; the concentration of suspended matters of the landfill leachate concentrated solution in the first concentrated solution tank after the suspended matters are removed is less than 1000mg/L.
In the invention, when the differential pressure of the filter unit is more than 35KPa, the filter bag is replaced or automatically cleaned.
According to the present invention, preferably, the step of the pH adjustment treatment includes injecting the chemical from the chemical tank into a water outlet pipe of the mixed acid pump by the metering pump, and mixing the chemical and the liquid subjected to the removal treatment of the suspended matter in the acid-adjusting water tank by the mixed acid pump; the agent for the pH adjustment treatment is a non-oxidizing acid, preferably hydrochloric acid; the pH of the liquid subjected to the pH adjustment treatment is 5-7.
According to the present invention, preferably, in the multistage forward osmosis treatment:
the conductivity difference between the solution at the feed liquid side and the solution at the drawing liquid side in each section of forward osmosis component is 30-40ms/cm;
the circulation flow rate of the solution at the feed liquid side in each section of forward osmosis component is 30-40m3 And/h, the circulation flow rate of the solution at the liquid drawing side is 10-15m3 /h；
The TDS of the liquid subjected to the pH adjustment treatment is 20000mg/L-30000mg/L; the TDS of the forward osmosis concentrated solution is 70000mg/L-80000mg/L;
the solution in the drawing liquid and the drawing liquid solute supplementing device is sodium chloride solution; the TDS of the drawing liquid is 110000mg/L-120000mg/L; the TDS of the drawing liquid diluent is 65000-70000mg/L; the solute concentration in the drawing liquid solute supplementing device is 6.8% -7.2%;
after the multistage forward osmosis treatment, the volume reduction of the liquid subjected to the pH adjustment treatment is 50-70%.
In the invention, the high-salt concentration unit recovers the monovalent salt concentration in the nanofiltration produced water on one hand and concentrates the draw solution diluent produced by the forward osmosis unit on the other hand. As a preferable scheme, the nanofiltration produced water enters the high-salt concentration unit, the action mechanism of the high-salt concentration unit is similar to that of nanofiltration, and concentrated brine with the osmotic pressure exceeding 14% of sodium chloride concentration can be produced, the concentrated brine can be used as the drawing liquid of the forward osmosis unit, and the produced water of the high-salt concentration unit is discharged after reaching the standard; the landfill leachate concentrated solution enters the forward osmosis unit after passing through the filtering unit and the acid regulating unit, and the forward osmosis unit further concentrates and reduces the landfill leachate concentrated solution (low osmotic pressure) by utilizing the drawing solution (high osmotic pressure) generated by the high-salt concentration unit, wherein the driving force is osmotic pressure difference. And the reduced landfill leachate concentrated solution enters a subsequent operation unit.
According to the present invention, preferably,
the TDS percentage of the inlet water of the first-stage nanofiltration device is 6.5% -7.0%;
the concentration factor of the primary concentration treatment is 1.65-1.75, the working pressure is 65bar-70bar, the TDS of the primary concentrated solution is 110000mg/L-120000mg/L, and the TDS of the primary water production is 28000-35000mg/L;
the concentration factor of the secondary concentration treatment is 1.8-2, the working pressure is 37bar-45bar, the TDS of the secondary concentrated solution is 50000mg/L-60000mg/L, and the TDS of the secondary water is 2800-3500mg/L;
the TDS of the tertiary concentrated solution is 5000-6000mg/L, and the TDS of the tertiary water is less than 100mg/L.
The present invention is specifically illustrated by the following examples.
The forward osmosis membrane is purchased from FTS company in the united states.
Example 1
The embodiment provides a landfill leachate concentrated solution reducing system, which is shown in fig. 1, and comprises a nanofiltration unit 1, a filtration unit 6, an acid regulating unit 7, a forward osmosis unit and a high-salt concentration unit which are connected in sequence;
the nanofiltration unit 1 is connected with the filtration unit 6 through a first concentrate water tank 4 and a first feed pump 5; the filtering unit 6 is a bag type filtering device;
the acid regulating unit 7 comprises an acid regulating water tank, an acid mixing pump 8, a dosing device, a pH controller and a second feeding pump 9; the dosing device comprises a metering pump, a Y-shaped filter and a dosing box which are connected in sequence; the water inlet and outlet pipes of the mixed acid pump 8 are connected with the acid regulating water tank, and the water outlet pipe of the mixed acid pump 8 is also connected with the metering pump; the metering pump and the pH controller are used for adjusting the pH value of the solution in the acid adjusting water tank; the acid regulating water tank, the dosing device, the metering pump, the Y-shaped filter and the dosing tank are not shown.
The forward osmosis unit comprises a forward osmosis water inlet tank 10, a third feed pump 11, a multi-section forward osmosis assembly 12, a second concentrated solution water tank 13, a drawing liquid water inlet pump 14, a drawing liquid concentrated water tank 15 and a drawing liquid diluted water tank 16;
the multistage forward osmosis components 12 are sequentially connected, and are used for realizing the stage-by-stage concentration of the feed liquid and the stage-by-stage dilution of the drawing liquid, and in this embodiment, the multistage forward osmosis components 12 are three-stage forward osmosis components; each section of forward osmosis assembly 12 comprises a feed liquid circulating pump 17, a forward osmosis membrane assembly 18 and a drawing liquid circulating pump 19; the feed liquid circulating pump 17 is connected with the feed liquid side of the forward osmosis membrane module 18, and the drawing liquid circulating pump 19 is connected with the drawing liquid side of the forward osmosis membrane module 18; the forward osmosis membrane module 18 includes a forward osmosis membrane element, a membrane shell, and a water inlet and outlet valve; the forward osmosis membrane element comprises a forward osmosis membrane and a diversion net bonded with the forward osmosis membrane; the area of the forward osmosis membrane is determined by the membrane flux and the amount of feed liquid treated by the forward osmosis membrane. The feed liquid inlet pipe 22 and the feed liquid concentration pipe 23 of the feed liquid circulating pump 17 are both connected to the feed liquid side of the forward osmosis membrane module 18, and the draw liquid concentrated water pipe 24 and the draw liquid dilute water pipe 25 of the draw liquid circulating pump 19 are both connected to the draw liquid side of the forward osmosis membrane module 18. The forward osmosis membrane element, membrane shell, water inlet and outlet valves, forward osmosis membrane and the water guide mesh bonded to the forward osmosis membrane are not shown.
The second feed pump 9, the forward osmosis feed water tank 10, the third feed pump 11 and the feed water inlet pipe 22 of the feed water circulating pump 17 of the first section forward osmosis assembly 20 are sequentially connected; the second concentrated solution water tank 13 is connected with a feed liquid concentration pipe 23 of a feed liquid circulating pump 17 of the last section of forward osmosis assembly 21;
the drawing liquid concentrated water tank 15, the drawing liquid water inlet pump 14 and the drawing liquid concentrated water pipe 24 of the drawing liquid circulating pump 19 of the last section of forward osmosis assembly 21 are sequentially connected; the drawing liquid dilute water tank 16 is connected with a drawing liquid dilute water pipe 25 of a drawing liquid circulating pump 19 of the first section of forward osmosis assembly 20;
the high-salt concentration unit comprises a fourth feed pump 26, a first-stage nanofiltration device 27, a first-stage water production tank 28, a fifth feed pump 29, a second-stage nanofiltration device 30, a second-stage water production tank 31, a sixth feed pump 32 and a reverse osmosis device 33 which are sequentially connected, and comprises a drawing liquid solute supplementing device (namely a sodium chloride supplementing unit in fig. 2 and 3) 34; the nanofiltration unit 1 is connected with the secondary water production tank 31 through a nanofiltration water production pipe 3; the draw solution thin water tank 16 is respectively connected with the fourth feed pump 26 and the secondary nanofiltration device 30, and the draw solution solute supplementing device 34 is arranged at one side of the draw solution thin water tank 16 opposite to the fourth feed pump 26; the primary nanofiltration device 27 is also connected to the draw solution concentrate tank 15 through a primary nanofiltration concentrate pipe 35; the reverse osmosis unit 33 is also connected to the primary water production tank 28 by a tertiary nanofiltration concentrate line 37. The draw solution lean tank 16 is connected to the secondary nanofiltration device 30 via a secondary nanofiltration concentrate line 36.
Example 2
The embodiment provides a method for reducing the landfill leachate concentrated solution, which is shown in fig. 1 and 2, wherein the method adopts the landfill leachate concentrated solution reducing system in the embodiment 1, and measured water quality data of the landfill leachate are shown in table 1.
TABLE 1 actual measured Water quality data for landfill leachate
The method comprises the following steps:
s1: delivering pretreated landfill leachate into the nanofiltration unit 1, delivering the obtained landfill leachate concentrate 2 into the first concentrate water tank 4 after nanofiltration separation, and delivering the obtained nanofiltration product water into the secondary product water tank 31;
s2: sequentially feeding the landfill leachate concentrated solution 2 in the first concentrated solution tank 4 into the filtering unit 6 and the acid adjusting unit 7, and sequentially removing suspended matters and adjusting the pH of the liquid;
s3: the liquid subjected to pH adjustment treatment is sent to a forward osmosis water inlet tank 10 of the forward osmosis unit, then is sent to a first section of forward osmosis assembly 20, the drawing liquid is correspondingly sent to a last section of forward osmosis assembly 21 of the forward osmosis unit from a drawing liquid concentrated water tank 15, after multi-section forward osmosis treatment, the forward osmosis concentrated liquid obtained by the last section of forward osmosis assembly 21 is sent to a second concentrated liquid water tank 13 for evaporation or incineration treatment, and the drawing liquid diluent obtained by the first section of forward osmosis assembly 20 is sent to a drawing liquid diluted water tank 16;
s4: the drawing liquid diluent is sent from the drawing liquid dilute water tank 16 to a first-stage nanofiltration device 27 of the high-salt concentration unit, after first-stage concentration treatment, the obtained first-stage concentrated liquid is returned to the drawing liquid concentrated water tank 24, the obtained first-stage produced water is sent to the first-stage produced water tank 28, then the drawing liquid dilute water tank 16 is sent to the second-stage nanofiltration device 30, after second-stage concentration treatment, the obtained second-stage concentrated liquid is returned to the drawing liquid dilute water tank 25, the obtained second-stage produced water is sent to the second-stage produced water tank 31, and is sent to the reverse osmosis device 33 together with the nanofiltration produced water, after third-stage concentration treatment, the obtained third-stage concentrated liquid is returned to the first-stage produced water tank 28, and the obtained third-stage produced water is discharged;
if the TDS of the solution in the dilute draw solution tank does not meet the requirement of the primary nanofiltration device 27 for the TDS of the water, the solution TDS in the dilute draw solution tank 16 is replenished by the solute replenishment device 34, so as to perform the primary concentration treatment.
The filtering precision of the filtering unit 6 is 50 mu m;
the concentration of suspended matters of the landfill leachate concentrated solution 2 in the first concentrated solution tank 4 after the suspended matters are removed is less than 1000mg/L;
the step of the pH adjustment treatment comprises injecting hydrochloric acid from the dosing tank into a water outlet pipe of the mixed acid pump 8 by using the metering pump, and mixing the liquid subjected to the removal treatment of the suspended matters in the acid adjustment water tank with the hydrochloric acid by the mixed acid pump 8; the pH of the liquid subjected to the pH adjustment treatment is 6;
in the multistage forward osmosis treatment:
the conductivity difference between the solution at the feed liquid side and the solution at the drawing liquid side in each section of forward osmosis component is 30-40ms/cm;
the circulation flow rate of the solution at the feed liquid side in each section of forward osmosis component is 30-40m3/h, and the circulation flow rate of the solution at the drawing liquid side is 10-15m3/h;
the TDS of the liquid subjected to the pH adjustment treatment is 20000mg/L-30000mg/L; the TDS of the forward osmosis concentrated solution is 70000mg/L-80000mg/L;
the solution in the draw solution and the draw solution solute replenishment device 34 are both sodium chloride solutions; the TDS of the drawing liquid is 110000mg/L-120000mg/L; the TDS of the drawing liquid diluent is 65000-70000mg/L; the solute concentration in the drawing liquid solute supplementing device is 7%;
after the multistage forward osmosis treatment, the volume reduction of the liquid subjected to the pH adjustment treatment is 50-70%.
The TDS percentage requirement range of the inlet water of the first-stage nanofiltration device 27 is 7%;
the concentration factor of the primary concentration treatment is 1.7, the working pressure is 65bar-70bar, the TDS of the primary concentrated solution is 110000mg/L-120000mg/L, and the TDS of the primary water is 28000-35000mg/L;
the concentration factor of the secondary concentration treatment is 1.75, the working pressure is 37bar-45bar, the TDS of the secondary concentrated solution is 50000mg/L-60000mg/L, and the TDS of the secondary water is 2800-3500mg/L;
the TDS of the tertiary concentrated solution is 5000-6000mg/L, and the TDS of the tertiary water is less than 100mg/L.
Example 3
The present embodiment provides a method for reducing the landfill leachate concentrated solution, as shown in fig. 1 and 3, which adopts the landfill leachate concentrated solution reducing system described in embodiment 1, and is different only in that a tubular micro filtration device (TMF) is selected as the filtration unit 6.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.