WO2019200590A1 - Composition and method for pretreating landfill leachate on mechanical vapor recompression evaporation process - Google Patents

Composition and method for pretreating landfill leachate on mechanical vapor recompression evaporation process Download PDF

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Publication number
WO2019200590A1
WO2019200590A1 PCT/CN2018/083782 CN2018083782W WO2019200590A1 WO 2019200590 A1 WO2019200590 A1 WO 2019200590A1 CN 2018083782 W CN2018083782 W CN 2018083782W WO 2019200590 A1 WO2019200590 A1 WO 2019200590A1
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Prior art keywords
composition
weight
landfill leachate
composition according
dry
Prior art date
Application number
PCT/CN2018/083782
Other languages
French (fr)
Inventor
Yan Xu
Fengyang LI
Original Assignee
Kemira Oyj
Kemira (Asia) Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kemira Oyj, Kemira (Asia) Co., Ltd. filed Critical Kemira Oyj
Priority to CN201880093775.4A priority Critical patent/CN112218831B/en
Priority to PCT/CN2018/083782 priority patent/WO2019200590A1/en
Publication of WO2019200590A1 publication Critical patent/WO2019200590A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/02—Softening water by precipitation of the hardness
    • C02F5/04—Softening water by precipitation of the hardness using phosphates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
    • C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
    • C02F5/105—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances combined with inorganic substances
    • 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

Definitions

  • the present invention relates to a composition and a method for pretreating landfill leachate on mechanical vapor recompression evaporation process according to the preambles of the independent claims presented below.
  • Landfill leachate is the high-density organic wastewater produced in landfill process. Because the leachate produced in landfill sites is very harmful to the environment, it has been paid attention to the treatment of leachate.
  • the MVR (mechanical vapor recompression) evaporation process is the most energy-efficient technique that removes organic matter among all existing evaporation processes and thus landfill leachate is evaporated by using MVR technology.
  • Landfill leachate also comprises inorganic metal ions, such as calcium and magnesium ions, which should be removed before entering evaporation system because they may be precipitated in the reactor after heating and evaporation.
  • inorganic metal ions such as calcium and magnesium ions
  • the precipitating of mineral deposits in the heat exchanger and/or MVR evaporation process can lead to the loss of heat transfer in the system, and consequently to significant economic losses.
  • Shutting down of the evaporation system to clean may be required for guaranteeing normal operation. Therefore, the pretreatment of landfill leachate for removing Mg and Ca ions prior to conveying the landfill leachate to the evaporation process is cost saving and desirable.
  • Pretreatment on MVR evaporation process for landfill leachate is Ca and Mg softening treatment, which actually removes Ca and Mg to prevent scaling in the evaporation process.
  • Conventional chemical pretreatment is performed by using caustic soda, Ca (OH) 2 -Na 2 CO 3 or NaOH-Na 2 CO 3 softening.
  • Ca (OH) 2 -Na 2 CO 3 or NaOH-Na 2 CO 3 softening There are some limitations relating to these conventional precipitation methods, such as high cost and low efficiency, e.g. disposal of large amount of sludge generated by the lime softening.
  • use of the conventional methods requires neutralization of pH (pH > 12) after the softening by using sulfuric acid, which causes significant operational risks, and also requires one additional process step.
  • the object of the invention is to provide a novel composition for use in pretreatment of leachate from landfill on MVR evaporation process.
  • the object of the invention is especially to provide a composition and a method for use in chemical precipitation pretreatment of landfill leachate, wherein at least part of calcium and magnesium ions can be removed from leachate prior to conveying landfill leachate to MVR evaporation process.
  • a typical composition according to the invention for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process comprises
  • a composition according to an embodiment of the invention is in a form of a dry powder.
  • the composition further comprises an aqueous medium, wherein the composition is in a form of an aqueous solution.
  • the composition according to the present invention is added to the landfill leachate prior to conveying the landfill leachate to the evaporation system.
  • the composition of the present invention is developed to use in pretreatment of leachate from landfill, wherein a concentration of Ca and Mg ions present in said leachate may be efficiently decreased prior to MVR evaporation process and so eliminating precipitation of Mg and Ca ions in the heat exchanger and/or MVR evaporation process.
  • the composition according to the present invention not only takes the effect on the removal of inorganic metal ions, such as calcium and magnesium, but also works well on ammonia and total suspended solids.
  • the composition according to the present invention reduces an amount of Ca and Mg ions and N-NH 4 content in landfill leachate, and further an amount of the sludge to be produced is decreased.
  • composition according to the present invention for pretreating landfill leachate does not require using sulfuric acid or the like to re-adjust pH after the softening treatment.
  • the present invention substitutes the alkali and acid treatment steps of the commonly known softening methods. Therefore, the method according to the present invention is more safety and simplifies the pretreatment process on MVR evaporation process.
  • the composition according to the present invention removes the hardness, i.e. Ca and Mg, effectively, even 90 %of hardness can be removed and the concentration of both calcium and magnesium can be controlled below 20 ppm. Besides that, also at least a part of ammonia can be eliminated.
  • the pretreated leachate effluent is suitable for the MVR evaporation process wherein the scaling may be inhibited and also the pretreatment costs may be decreased.
  • the composition and the method according to the present invention decrease the amount of the dosage to 30-35 %and produce smaller amount of sludge.
  • the composition and the method according to the present invention provide same efficiency as the conventionally softening methods by using remarkably smaller dosage amounts.
  • the present invention provides the pretreatment of MVR evaporation process on the landfill leachate and brings forward the solvent method on the scaling problems of heat exchange and MVR evaporation processes.
  • the composition according to the invention comprises the cationic polymer for providing the composition to capability to flocculate suspended solids.
  • the composition according to the present invention comprises cationic polymer in an amount of 0.2–2 weight-%, calculated from the total weight of the constituents in the composition, as dry. If the composition comprises more than 2 weight-%cationic polymer, the viscosity of the aqueous solution may be too high for application.
  • the cationic polymer comprises 0.1–12 mol-%of cationic monomers.
  • a cationic polymer is a copolymer of acrylamide and cationic monomers, wherein cationic monomers are selected from the group consisting of 2- (dimethylamino) ethyl acrylate (ADAM) , [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , 2-dimethylaminoethyl methacrylate (MADAM) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , [3- (acryloylamino) propyl] trimethylammonium chloride (APTAC) , [3-(methacryloylamino) propyl] trimethylammonium chloride (MAPTAC) , and diallyldimethylammonium chloride (DADMAC) .
  • ADAM 2- (dimethylamino) ethyl acrylate
  • the cationic monomers are selected from [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , and diallyldimethylammonium chloride (DADMAC) . More preferably the cationic monomer is [2-(acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) .
  • the composition of the invention further comprises 5–80 weight-%, and preferably 30–80 weight-%or 40 –60 weight-%of sodium and/or potassium phosphate, calculated from the total weight of the constituents in the composition, as dry.
  • the composition comprises disodium phosphate (Na 2 HPO 4 ) , sodium dihydrogen phosphate (NaH 2 PO 4 ) and/or dipotassium phosphate (K 2 HPO 4 ) .
  • the composition according to the present invention in a powder form comprises preferably sodium dihydrogen phosphate and composition in a form of aqueous solution comprises preferably dipotassium phosphate.
  • Sodium and/or potassium phosphates are especially used for Mg removal.
  • composition of the invention further comprises 5–40 weight-%, and preferably 10–40 weight-%or 20–30 weight-%of sodium and/or potassium carbonate, calculated from the total weight of the constituents in the composition, as dry.
  • the composition comprises sodium carbonate.
  • Carbonates in the composition remove efficiently calcium from the leachate and phosphate removes magnesium and ammonium.
  • the amounts of sodium and/or potassium phosphate and sodium and/or potassium carbonate in the composition are selected from the basis of the initial calcium and magnesium amounts of landfill leachate to be treated.
  • the composition of the invention further comprises 5–40 weight-%, and preferably 20–40 weight-%of saccharide, calculated from the total weight of the constituents in the composition as dry, for stabilizing the composition.
  • the saccharide may be selected from monosaccharide, polysaccharide, hemicellulose and any combination of them.
  • the composition comprises glucose for stabilizing the composition.
  • the composition for pretreating landfill leachate, in a dry powder form comprises
  • an aqueous solution of the composition for pretreating landfill leachate comprises
  • weight-%of the constituents is calculated from the total weight of the constituents in the composition, as dry.
  • the amounts of the constituents in the composition may be adjusted by the water quality of landfill leachate to be treated.
  • the composition is added to a flow of an aqueous landfill leachate.
  • the composition according to the invention may be used in desired dose, depending on the nature of the landfill leachate to be treated.
  • the composition may be added in an amount of 3–4 g (dry) /L, and preferably 3.3–3.5 g (dry) /L.
  • composition according to the present invention is added to landfill leachate prior to conveying the landfill leachate to the MVR evaporation system.
  • the composition is applied as an aqueous solution to landfill leachate.
  • the composition according to the invention in a dry powder form is dissolved into an aqueous solution, such as water, prior to addition into the landfill leachate.
  • the composition is in dissolved form in the aqueous solutions.
  • Example 2 the effects of the pretreatment composition according to the present invention were studied.
  • the reference samples were treated by commonly used softening chemicals.
  • the remaining Mg, Ca and N-NH 4 were analyzed from the landfill leachate samples after the addition of the pretreatment composition.
  • Ca and Mg were analyzed with ICP instrument, and N-NH 4 was analyzed with HACH method.
  • pH of the landfill leachate sample was adjusted to 9.100 mL landfill leachate was poured into the glass screw cap centrifuge tube.
  • the pretreatment chemical was added, and the tube was slowly shaken 20 times for pretreating the samples. After the samples were stood 30 minutes, the remaining Ca and Mg were analyzed. Also, pH and the volume of sludge were measured after pretreatment.
  • Table 1 is presented the results measured from landfill leachate sample prior to pretreatment and after the pretreatment with the composition according to the present invention.
  • Table 2 presents comparison between the composition according to the present invention and the reference compositions.
  • the references comprise caustic soda softening and Ca (OH) 2 -Na 2 CO 3 softening.
  • the composition according to the present invention decreases the amount of the dosage to 35 %and still the same and even better efficiency as the conventional methods has reached.
  • the novel composition according to the present invention not only takes the effect on the removal of inorganic metal ion, such as calcium and magnesium, but also works well on ammonia. Further, the amount of the sludge to be produced is decreased.
  • the pH of landfill leachate after pretreatment with the composition according to the present invention does not need the re-adjustment of pH.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Processing Of Solid Wastes (AREA)
  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)

Abstract

A composition for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process by which Mg, Ca and ammonia are efficiently removed is provided. The composition comprises 0.2–2 weight-% of cationic polymer, 5–80 weight-% of sodium and/or potassium phosphate, 5–40 weight-% of saccharide, and 5–40 weight-% of sodium and/or potassium carbonate, calculated from the total weight of the constituents in the composition, as dry. A method for pretreating landfill leachate on MVR evaporation process is provided. The composition is added to the landfill leachate prior to conveying the landfill leachate to the evaporation system.

Description

COMPOSITION AND METHOD FOR PRETREATING LANDFILL LEACHATE ON MECHANICAL VAPOR RECOMPRESSION EVAPORATION PROCESS TECHNICAL FIELD
The present invention relates to a composition and a method for pretreating landfill leachate on mechanical vapor recompression evaporation process according to the preambles of the independent claims presented below.
BACKGROUND ART
Landfill leachate is the high-density organic wastewater produced in landfill process. Because the leachate produced in landfill sites is very harmful to the environment, it has been paid attention to the treatment of leachate. The MVR (mechanical vapor recompression) evaporation process is the most energy-efficient technique that removes organic matter among all existing evaporation processes and thus landfill leachate is evaporated by using MVR technology.
Landfill leachate also comprises inorganic metal ions, such as calcium and magnesium ions, which should be removed before entering evaporation system because they may be precipitated in the reactor after heating and evaporation. The precipitating of mineral deposits in the heat exchanger and/or MVR evaporation process can lead to the loss of heat transfer in the system, and consequently to significant economic losses. Shutting down of the evaporation system to clean may be required for guaranteeing normal operation. Therefore, the pretreatment of landfill leachate for removing Mg and Ca ions prior to conveying the landfill leachate to the evaporation process is cost saving and desirable. Pretreatment on MVR evaporation process for landfill leachate is Ca and Mg softening treatment, which actually removes Ca and Mg to prevent scaling in the evaporation process. Conventional chemical pretreatment is performed by using caustic soda, Ca (OH)  2-Na 2CO 3 or NaOH-Na 2CO 3 softening. There are some limitations relating to these conventional precipitation methods, such as high cost and low efficiency, e.g. disposal of large amount of sludge generated by the lime softening. Further, use of the conventional methods requires neutralization of  pH (pH > 12) after the softening by using sulfuric acid, which causes significant operational risks, and also requires one additional process step.
SUMMARY OF INVENTION
There is a constant need for cost effective compositions and method for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process, which inhibit precipitating of Mg and Ca ions in the heat exchanger and/or MVR evaporation process and decrease the formation of sludge.
It is an object of the present invention to reduce or even eliminate the above-mentioned problems appearing in prior art.
The object of the invention is to provide a novel composition for use in pretreatment of leachate from landfill on MVR evaporation process.
The object of the invention is especially to provide a composition and a method for use in chemical precipitation pretreatment of landfill leachate, wherein at least part of calcium and magnesium ions can be removed from leachate prior to conveying landfill leachate to MVR evaporation process.
In order to achieve among others the objects presented above, the invention is characterized by what is presented in the characterizing parts of the enclosed independent claims.
Some preferred embodiments of the invention will be described in the other claims.
The embodiments and advantages mentioned in this text relate, where applicable, both to the composition, the method as well as to the uses according to the invention, even though it is not always specifically mentioned.
A typical composition according to the invention for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process comprises
-0.2–2 weight-%of cationic polymer,
-5–80 weight-%of sodium and/or potassium phosphate,
-5–40 weight-%of saccharide, and
-5–40 weight-%of sodium and/or potassium carbonate,
calculated from the total weight of the constituents in the composition, as dry.
A composition according to an embodiment of the invention is in a form of a dry powder. According to another embodiment of the invention, the composition further comprises an aqueous medium, wherein the composition is in a form of an aqueous solution.
In a typical method according to the invention for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process, the composition according to the present invention is added to the landfill leachate prior to conveying the landfill leachate to the evaporation system.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the present invention is developed to use in pretreatment of leachate from landfill, wherein a concentration of Ca and Mg ions present in said leachate may be efficiently decreased prior to MVR evaporation process and so eliminating precipitation of Mg and Ca ions in the heat exchanger and/or MVR evaporation process. The composition according to the present invention not only takes the effect on the removal of inorganic metal ions, such as calcium and magnesium, but also works well on ammonia and total suspended solids. The composition according to the present invention reduces an amount of Ca and Mg ions and N-NH 4 content in landfill leachate, and further an amount of the sludge to be produced is decreased.
The use of the composition according to the present invention for pretreating landfill leachate does not require using sulfuric acid or the like to re-adjust pH after the softening treatment. The present invention substitutes the alkali and acid treatment steps of the commonly known softening methods. Therefore, the method according to the present invention is more safety and simplifies the pretreatment process on MVR evaporation process.
It has been observed that the composition according to the present invention removes the hardness, i.e. Ca and Mg, effectively, even 90 %of hardness can be removed and the concentration of both calcium and magnesium can be controlled below 20 ppm. Besides that, also at least a part of ammonia can be eliminated. The pretreated leachate effluent is suitable for the MVR evaporation process wherein the scaling may be inhibited and also the pretreatment costs may be decreased. Compared with the conventional hardness removal methods, the composition and the method according to the present invention decrease the amount of the dosage to 30-35 %and produce smaller amount of sludge. The composition and the method according to the present invention provide same efficiency as the conventionally softening methods by using remarkably smaller dosage amounts.
The present invention provides the pretreatment of MVR evaporation process on the landfill leachate and brings forward the solvent method on the scaling problems of heat exchange and MVR evaporation processes.
The composition according to the invention comprises the cationic polymer for providing the composition to capability to flocculate suspended solids. The composition according to the present invention comprises cationic polymer in an amount of 0.2–2 weight-%, calculated from the total weight of the constituents in the composition, as dry. If the composition comprises more than 2 weight-%cationic polymer, the viscosity of the aqueous solution may be too high for application. According to an embodiment of the invention, the cationic polymer comprises 0.1–12 mol-%of cationic monomers. In one preferred embodiment a cationic polymer is a copolymer of acrylamide and cationic monomers, wherein cationic monomers are selected from the group consisting of 2- (dimethylamino) ethyl acrylate (ADAM) , [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , 2-dimethylaminoethyl methacrylate (MADAM) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , [3- (acryloylamino) propyl] trimethylammonium chloride (APTAC) , [3-(methacryloylamino) propyl] trimethylammonium chloride (MAPTAC) , and diallyldimethylammonium chloride (DADMAC) . In a preferred embodiment the cationic monomers are selected from [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , and diallyldimethylammonium  chloride (DADMAC) . More preferably the cationic monomer is [2-(acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) .
The composition of the invention further comprises 5–80 weight-%, and preferably 30–80 weight-%or 40 –60 weight-%of sodium and/or potassium phosphate, calculated from the total weight of the constituents in the composition, as dry. In one preferred embodiment, the composition comprises disodium phosphate (Na 2HPO 4) , sodium dihydrogen phosphate (NaH 2PO 4) and/or dipotassium phosphate (K 2HPO 4) . The composition according to the present invention in a powder form comprises preferably sodium dihydrogen phosphate and composition in a form of aqueous solution comprises preferably dipotassium phosphate. Sodium and/or potassium phosphates are especially used for Mg removal.
The composition of the invention further comprises 5–40 weight-%, and preferably 10–40 weight-%or 20–30 weight-%of sodium and/or potassium carbonate, calculated from the total weight of the constituents in the composition, as dry. Preferably the composition comprises sodium carbonate. Carbonates in the composition remove efficiently calcium from the leachate and phosphate removes magnesium and ammonium.
The amounts of sodium and/or potassium phosphate and sodium and/or potassium carbonate in the composition are selected from the basis of the initial calcium and magnesium amounts of landfill leachate to be treated.
The composition of the invention further comprises 5–40 weight-%, and preferably 20–40 weight-%of saccharide, calculated from the total weight of the constituents in the composition as dry, for stabilizing the composition. The saccharide may be selected from monosaccharide, polysaccharide, hemicellulose and any combination of them. In one preferred embodiment, the composition comprises glucose for stabilizing the composition.
According to one preferred embodiment, the composition for pretreating landfill leachate, in a dry powder form, comprises
-0.2–2 weight-%of cationic polyacrylamide,
-30–80 weight-%of disodium phosphate (Na 2HPO 4) , sodium dihydrogen phosphate (NaH 2PO 4) and/or dipotassium phosphate (K 2HPO 4) ,
-20–40 weight-%of glucose, and
-10–40 weight-%of sodium carbonate (Na 2CO 3) , calculated from the total weight of the constituents in the composition, as dry.
According to another preferred embodiment, an aqueous solution of the composition for pretreating landfill leachate comprises
-0.2–2 weight-%of cationic polyacrylamide,
-5–80 weight-%of disodium phosphate (Na 2HPO 4) , sodium dihydrogen phosphate (NaH 2PO 4) and/or dipotassium phosphate (K 2HPO 4) ,
-5–40 weight-%of glucose, and
-5–40 weight-%of sodium carbonate (Na 2CO 3) , and
-10–90 weight-%of water,
wherein the weight-%of the constituents is calculated from the total weight of the constituents in the composition, as dry.
The amounts of the constituents in the composition may be adjusted by the water quality of landfill leachate to be treated.
According to a preferred embodiment of the invention, the composition is added to a flow of an aqueous landfill leachate. The composition according to the invention may be used in desired dose, depending on the nature of the landfill leachate to be treated. According to an embodiment of the invention the composition may be added in an amount of 3–4 g (dry) /L, and preferably 3.3–3.5 g (dry) /L.
The composition according to the present invention is added to landfill leachate prior to conveying the landfill leachate to the MVR evaporation system.
According to a preferred embodiment of the present invention, the composition is applied as an aqueous solution to landfill leachate. Typically, the composition according to the invention in a dry powder form is dissolved into an aqueous solution, such as water, prior to addition into the landfill leachate. The composition is in dissolved form in the aqueous solutions.
A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate but are not to be construed  as the limit of the present invention.
Example
In the following Example, the effects of the pretreatment composition according to the present invention were studied. The reference samples were treated by commonly used softening chemicals. The remaining Mg, Ca and N-NH 4 were analyzed from the landfill leachate samples after the addition of the pretreatment composition.
Ca and Mg were analyzed with ICP instrument, and N-NH 4 was analyzed with HACH method.
First, pH of the landfill leachate sample was adjusted to 9.100 mL landfill leachate was poured into the glass screw cap centrifuge tube. The pretreatment chemical was added, and the tube was slowly shaken 20 times for pretreating the samples. After the samples were stood 30 minutes, the remaining Ca and Mg were analyzed. Also, pH and the volume of sludge were measured after pretreatment.
In Table 1 is presented the results measured from landfill leachate sample prior to pretreatment and after the pretreatment with the composition according to the present invention. Table 2 presents comparison between the composition according to the present invention and the reference compositions. The references comprise caustic soda softening and Ca (OH)  2-Na 2CO 3 softening.
Table 1.
Figure PCTCN2018083782-appb-000001
Table 2.
Figure PCTCN2018083782-appb-000002
The composition according to the present invention decreases the amount of the dosage to 35 %and still the same and even better efficiency as the conventional methods has reached. The novel composition according to the present invention not only takes the effect on the removal of inorganic metal ion, such as calcium and magnesium, but also works well on ammonia. Further, the amount of the sludge to be produced is decreased. The pH of landfill leachate after pretreatment with the composition according to the present invention does not need the re-adjustment of pH.

Claims (13)

  1. A composition for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process, characterized in that the composition comprises
    - 0.2–2 weight-%of cationic polymer,
    - 5–80 weight-%of sodium and/or potassium phosphate,
    - 5–40 weight-%of saccharide, and
    - 5–40 weight-%of sodium and/or potassium carbonate,
    calculated from the total weight of the constituents in the composition, as dry.
  2. The composition according to claim 1, characterized in that the cationic polymer is a copolymer of acrylamide and cationic monomers.
  3. The composition according to claim 1 or 2, characterized in that the cationic polymer comprises 0.1–12 mol-%of cationic monomers.
  4. The composition according to any of the preceding claims, characterized in that the composition comprises 30–80 weight-%of sodium and/or potassium phosphate, calculated from the total weight of the constituents in the composition, as dry.
  5. The composition according to any of the preceding claims, characterized in that the composition comprises disodium phosphate (Na 2HPO 4) , sodium dihydrogen phosphate (NaH 2PO 4) and/or dipotassium phosphate (K 2HPO 4) .
  6. The composition according to any of the preceding claims, characterized in that the composition comprises 20–40 weight-%of saccharide, calculated from the total weight of the constituents in the composition, as dry.
  7. The composition according to any of the preceding claims, characterized in that the composition comprises monosaccharide, polysaccharide, hemicellulose or any combination of them.
  8. The composition according to claim 7, characterized in that the composition comprises glucose.
  9. The composition according to any of the preceding claims, characterized in that the composition comprises 10–40 weight-%of sodium and/or potassium carbonate, preferably sodium carbonate, calculated from the total weight of the constituents in the composition, as dry.
  10. The composition according to any of the preceding claims, characterized in that the composition is in a dry particle form.
  11. The composition according to any of the preceding claims 1 to 9, characterized in that the composition further comprises an aqueous medium, wherein the composition is in a form of an aqueous solution.
  12. A method for pretreating landfill leachate on mechanical vapor recompression (MVR) evaporation process, in which method the composition according to any of the preceding claims 1 to 11 is added to the landfill leachate prior to conveying the landfill leachate to the evaporation system.
  13. The method according to claim 12, characterized in that the composition is added in an amount of 3–4 g (dry) /L, and preferably 3.3–3.5 g (dry) /L.
PCT/CN2018/083782 2018-04-19 2018-04-19 Composition and method for pretreating landfill leachate on mechanical vapor recompression evaporation process WO2019200590A1 (en)

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