CN109354292B - Reduction treatment process for landfill leachate membrane filtration concentrated solution - Google Patents
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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- C02F3/00—Biological treatment of water, waste water, or sewage
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- C02F3/12—Activated sludge processes
- C02F3/1236—Particular type of activated sludge installations
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Abstract
The invention discloses a reduction treatment process of landfill leachate membrane filtration concentrated solution, which comprises the following steps: blending and mixing the NF concentrated solution and the RO concentrated solution to obtain blended solution; adding ferric chloride and polyacrylamide into the blended solution, stirring, and performing flocculation precipitation to obtain supernatant and sludge; adjusting the pH value of the supernatant to 6.1-6.6, and then carrying out two-stage CSM membrane reduction treatment to obtain a clear liquid and an intercepted concentrated liquid; evaporating the obtained clear liquid to obtain concentrated mother liquid and condensed water obtained by condensation; and (4) recharging the obtained sludge, the trapped concentrated solution and the concentrated mother solution into a landfill or returning the sludge, the trapped concentrated solution and the concentrated mother solution to an incinerator for incineration treatment. The treatment process has high concentration multiple, the effluent quality can reach the standard of Table 2 of GB 16889-2008, the operation cost is low, the process realization difficulty is low, the pollution is low, and the reduction of the landfill leachate membrane filtration concentrated solution can be effectively realized.
Description
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a reduction treatment process of landfill leachate membrane filtration concentrated solution.
Background
At present, the daily production of domestic garbage in Changsha city is about 8000 tons, wherein about 2000 tons is used for sanitary landfill and 6000 tons of incineration treatment. The method comprises the steps that fresh garbage is extruded before sanitary landfill or incineration, the amount of leachate generated per day is about 3200 tons (the water content is about 40%), and after leachate is treated by a treatment process of 'water inlet + water quality balance + external MBR + UF + NF/RO system + standard discharge', 480-800 tons of membrane filtration concentrated solution are generated per day (the generation ratio of the membrane filtration concentrated solution is calculated according to 15-25%).
The leachate adopts a treatment process of 'water inlet + water quality balance + external MBR + UF + NF/RO system + standard discharge', wherein the ultrafiltration membrane (UF) is a physical screening process which takes pressure as a driving force and utilizes different pore diameters of the ultrafiltration membrane to separate liquid, and the process is a membrane separation technology which takes pressure as a driving force. The separation aperture is between Nanofiltration (NF) and Microfiltration (MF), generally ranges from 0.001 to 0.05 mu m, the range of molecular weight cut-off is 1000 to 100000 daltons, and the operation pressure is generally 3 to 10 bar. The separation mechanism of the membrane mainly depends on physical screening, and after a certain pressure is applied to feed liquid, three modes of interception of high molecular substances and colloidal substances due to the primary adsorption of the membrane surface and micropores in the pores and mechanical screening of the membrane surface are stopped by the ultrafiltration membrane, and water and low molecular substances pass through the membrane. When the system is stable, the Chemical Oxygen Demand (COD) content of the clear liquid passing through the ultrafiltration membrane is 400-800 mg/L, the conductivity (k) is 11-14 ms/cm, and the ammonia nitrogen concentration is 2-10 mg/L.
The ultrafiltration clear liquid needs to be further filtered and separated by an NF/RO membrane, wherein the principle of a Nanofiltration (NF) separation technology is similar to mechanical screening, but the nanofiltration membrane body has electric charge, so the separation mechanism is only similar to mechanical screening, and simultaneously, the dissolution and diffusion effects are also included, so the nanofiltration membrane still has higher desalination performance and intercepts low molecular weight organic matters under very low pressure. The nanofiltration process has poor interception on monovalent ions and organic matters with the molecular weight of less than 200, and has higher removal rate on divalent or multivalent ions and organic matters with the molecular weight of between 200 and 500. The separation aperture of the nanofiltration membrane is 1-10 nm, and the operation pressure is 5-25 bar. Reverse Osmosis (RO) has a separation particle size of less than 1nm and a separation particle level of up to an ionic level. The separation mechanism is a selective adsorption-capillary flow mechanism: because of the hydrophilic nature of the membrane surface, water molecules are preferentially adsorbed and salt molecules are rejected, so that two pure water layers of water molecules (1 nm) are formed in the membrane epidermal layer, and the molecules of the pure water layers continuously flow through the reverse osmosis membrane through capillary tubes by applying pressure. The same principle is that when the system is stable, the yield of the nanofiltration clear liquid is controlled to be 85%, and the yield of the reverse osmosis clear liquid is controlled to be 75%, the Chemical Oxygen Demand (COD) content of the clear liquid penetrating through the nanofiltration membrane is 60-100 mg/L, the conductivity (k) is 11-14 ms/cm, the ammonia nitrogen concentration is 2-10 mg/L, the Chemical Oxygen Demand (COD) content of the clear liquid penetrating through the reverse osmosis membrane is 5-10 mg/L, the conductivity (k) is 400-700 us/cm, and the ammonia nitrogen concentration is 0-2 mg/L.
According to the NF/RO separation principle, the UF clear solution generates about 15% of membrane filtration concentrated solution after the NF membrane separation, and generates about 25% of membrane filtration concentrated solution after the RO membrane separation, and the two parts of membrane filtration concentrated solution have the characteristics that: the method has the characteristics of high organic matter concentration, high salinity, poor biodegradability and the like, and has complex components and great treatment difficulty, and the specific detection indexes of the components are shown in the following table:
the membrane filtration concentrate of the landfill leachate is a residual solution intercepted by an NF/RO membrane after the landfill leachate is subjected to biodegradation, water can smoothly pass through the membrane due to the selective permeability of the permeable membrane, and other compounds are intercepted by the membrane more or less or even completely, so that the inflow water is divided into two parts after passing through the membrane, namely the treated penetrating fluid and the membrane filtration concentrate respectively, wherein the membrane filtration concentrate has the characteristics that: the organic matter has the characteristics of high concentration, high chroma, poor biodegradability, relatively high salt content and the like, has high treatment difficulty and high cost, and the main components of the organic matter are humus substances which are brownish black and contain a large amount of metal ions. The membrane filtration concentrate produced by the nanofiltration and reverse osmosis processes has TDS concentration of 20000-35000 mg/L, conductivity of 25000-45000 us/cm, COD concentration of 2500-4000 mg/L and ammonia nitrogen concentration of 5-20 mg/L.
The existing membrane filtration concentrated solution has a plurality of treatment processes, wherein the representative treatment processes with more engineering applications comprise a recharging method, a membrane concentration method, a coagulating sedimentation-advanced oxidation method, an evaporation-drying method, an electrochemical oxidation method and the like. The recharging method can cause the gradual accumulation of organic matters and salt in the landfill site, and the high-concentration high-salt leachate returns to a biochemical system, so that the pressure of a membrane tube rises, and the system is extremely unstable in operation. The membrane concentration method has a middle Asia-nanofiltration membrane method, the yield of clear liquid is only 55-60%, the concentration multiple is 1-1.2 times, the clear liquid outlet water cannot reach the standard of GB 16889 + 2008 table 2, and the problems of high operation pressure, high energy consumption, low water yield, serious membrane pollution and the like exist. The membrane filtration concentrated solution is treated by adopting a conventional evaporation method, and evaporation residues are hazardous wastes, so that the evaporation equipment has short service life and high treatment cost. The membrane filtration concentrated solution is treated by adopting a coagulation precipitation-advanced oxidation method, the removal effect of humic acid substances is good, but residual organic nitrogen substances in the concentrated solution can be oxidized into nitrate nitrogen, and the total nitrogen of effluent is difficult to reach the standard. The electrochemical oxidation method is adopted to treat the membrane filtration concentrated solution, and the method can not remove hardness ions in the membrane filtration concentrated solution, and can cause scaling and blockage of an electrolytic polar plate, a pipeline and a reactor after long-term operation.
201721625490.X discloses an integrated decrement device for concentrated solution of landfill leachate, but the quality of the effluent water treated by the device cannot meet the national standard of discharge; 201410231477.0 discloses a method for treating leachate nanofiltration concentrated solution by ozone oxidation, but the quality of the effluent obtained by the method can not meet the national standard of discharge and the operation cost is high.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a reduction treatment process of the membrane filtration concentrated solution of the landfill leachate, which has the advantages of high concentration multiple, low operation cost, low process realization difficulty and low pollution, can achieve the standard of table 2 in GB 16889-2008, and can effectively treat the membrane filtration concentrated solution of the landfill leachate, particularly effectively treat NF concentrated solution and RO concentrated solution generated in the process of treating the landfill leachate at the early stage and the medium and long term, finally realize the reduction of the membrane filtration concentrated solution of the landfill leachate, and provide a guidance direction for realizing the zero emission target of pollutants in the membrane filtration concentrated solution in the leachate industry.
In order to solve the technical problems, the invention adopts the following technical scheme:
a process for reducing the membrane filtration concentrated solution of landfill leachate comprises the following steps:
s1, blending and mixing the NF concentrated solution and the RO concentrated solution to obtain a blended solution;
s2, adding ferric chloride and polyacrylamide into the blended liquid, stirring, and performing flocculation precipitation to obtain supernatant and sludge;
s3, adjusting the pH value of the supernatant to 6.1-6.6, and then carrying out two-stage CSM membrane reduction treatment to obtain a clear liquid and an entrapped concentrated liquid;
s4, evaporating the clear liquid obtained in the step S3 to obtain concentrated mother liquid and condensed water obtained by condensation, and discharging the condensed water after the temperature of the condensed water is reduced;
and S5, returning the sludge obtained in the step S2, the trapped concentrated solution obtained in the step S3 and the concentrated mother solution obtained in the step S4 to a landfill or an incinerator for incineration treatment.
In the above reduction treatment process of the landfill leachate membrane filtration concentrated solution, preferably, in step S3, the total amount of the clear liquid is 95 to 97% of the mass of the supernatant liquid;
the COD concentration of the clear liquid is 1000-2000 mg/L, and the ammonia nitrogen concentration is 0-2 mg/L.
In the above process for reducing the landfill leachate membrane filtration concentrated solution, preferably, in step S3, in the two-stage CSM membrane reduction treatment, the operating pressure of the first-stage membrane treatment is less than 4.5MPa, and the concentrated solution obtained by the first-stage membrane treatment is subjected to a second-stage membrane treatment, where the operating pressure of the second-stage membrane treatment is less than 6 MPa;
the membrane elements of the first-stage membrane treatment and the second-stage membrane treatment are both RE8040SN membrane elements;
the yield of the first-stage clear liquid treated by the first-stage membrane is 80-85%, and the yield of the second-stage clear liquid treated by the second-stage membrane is 75-80%.
In the above process for reducing the membrane filtration concentrated solution of landfill leachate, preferably, in step S3, the amount of the trapped concentrated solution is 3 to 5% of the mass of the supernatant;
the COD concentration of the intercepted concentrated solution is 4000-10000 mg/L, and the ammonia nitrogen concentration is 20-60 mg/L.
Preferably, in the reduction treatment process of the landfill leachate membrane filtration concentrated solution, in the step S1, the blended solution has a COD concentration of 2500 to 4000mg/L and an ammonia nitrogen concentration of 5 to 20 mg/L.
In the above process for reducing the membrane filtration concentrated solution of landfill leachate, preferably, in step S4, the amount of the condensed water is 90 to 95% of the mass of the clear liquid; the COD concentration of the condensed water is 20-80 mg/L, and the ammonia nitrogen concentration is 0-5 mg/L.
In the above reduction treatment process of the landfill leachate membrane filtration concentrated solution, preferably, in step S4, the amount of the concentrated mother liquor is 5 to 10% of the mass of the clear liquid; the COD concentration of the concentrated mother liquor is 20000-50000 mg/L, and the TDS concentration is 400000-600000 mg/L.
In the above process for reducing the membrane filtration concentrated solution of landfill leachate, it is preferable that the step S4 further includes a step of uniformly mixing the clear liquid with an antifoaming agent and performing a preheating treatment before evaporating the clear liquid.
Preferably, in the step S2, the adding amount of the ferric chloride is 0.15 to 0.35% of the total amount of the prepared liquid, and the adding amount of the polyacrylamide is 0.002 to 0.008% of the total amount of the prepared liquid by mass percentage.
In the above process for reducing the membrane filtration concentrated solution of landfill leachate, preferably, in step S4, the evaporation temperature is 105 to 110 ℃.
Compared with the prior art, the invention has the advantages that:
1. according to the characteristics of NF leachate and RO leachate, a great deal of research is carried out to obtain the advanced treatment process suitable for the liquid membrane filtration concentrated solution of the landfill leachate, the NF leachate and the RO leachate are mixed, flocculation precipitation is firstly carried out on the membrane filtration concentrated solution obtained by mixing to remove a part of COD, membrane reduction treatment is carried out on the supernatant obtained by the flocculation precipitation to intercept humic acid substances, evaporation and condensation are carried out on the membrane reduction clear solution obtained by the membrane reduction treatment, the condensate obtained by the condensation reaches the standard of GB 16889 2008 table 2, the condensate can be directly discharged, most of COD, TDS and metal ions are remained in the evaporation concentrated solution, and a small amount of floc generated by the flocculation precipitation, humic acid substances generated by the membrane reduction and the evaporation concentrated solution are sprayed back to an incinerator or a recharging landfill site. The invention organically combines a plurality of processes, namely, processes of flocculation precipitation, membrane reduction, evaporation condensation and the like which are buckled by ring and ring, the total clear liquid rate obtained after treatment is more than 85 percent, the treatment cost is low, a small amount of sludge, humic acid substances and evaporation concentrated liquid obtained are subjected to incineration treatment, and the generated slag is used for ash waste landfill or recharging landfill sites, thereby realizing the aim of efficiently treating the pollutants in the landfill leachate.
2. In the whole process, due to organic matching of the whole process, the steps are reasonably designed, the concentration multiple can reach 10-20 times, the treatment efficiency is high, the damage to equipment is small, the pollution is extremely low, the operation cost is low, and the process difficulty is low.
Drawings
Fig. 1 is a flow chart of the advanced treatment process of membrane filtration concentrate of landfill leachate according to the present invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and specific examples.
The invention relates to a process for deeply treating membrane filtration concentrated solution of landfill leachate, which has a process flow diagram shown in figure 1 and comprises the following steps:
(1) wastewater blending
Conveying the NF concentrated solution and the RO concentrated solution to a pretreatment regulating reservoir by using a lift pump, uniformly mixing the NF concentrated solution and the RO concentrated solution, regulating the water quantity and the water quality of the membrane filtration concentrated solution by allocating the proportion of the NF concentrated solution and the RO concentrated solution, wherein the COD concentration of the membrane filtration concentrated solution of the garbage leachate obtained after regulation is 2500-4000 mg/L, the ammonia nitrogen concentration is 5-20 mg/L, if the COD and the ammonia nitrogen concentration in the water are too high, the effluent is difficult to ensure to reach the standard, and if the COD and the ammonia nitrogen concentration in the water are too low, the waste of process equipment exists.
(2) Flocculation precipitation
Conveying the membrane filtration concentrated solution of the landfill leachate after wastewater blending to a stirring tank, adding ferric trichloride and polyacrylamide into the stirring tank, fully mixing the ferric trichloride and the polyacrylamide in the stirring tank with the membrane filtration concentrated solution through a stirrer, carrying out coagulation reaction, adding a flocculation mixed solution after reaction to a sedimentation tank for sedimentation, enabling supernatant of the sedimentation tank to flow into a clear solution collecting tank, and periodically discharging sludge in the sedimentation tank to be transferred to a landfill. Preferably, the addition amount of the ferric trichloride is 0.15-0.35% of the total mass of the landfill leachate membrane filtration concentrated solution, and the addition amount of the polyacrylamide is 0.002-0.008% of the total mass of the landfill leachate membrane filtration concentrated solution.
The COD concentration of the supernatant after flocculation precipitation is 1500-2500 mg/L, and the ammonia nitrogen concentration is 5-20 mg/L. After flocculation precipitation, the COD content can be removed by a small amount, which is beneficial to the subsequent membrane reduction treatment.
After flocculation precipitation, the method can degrade partial organic matters, reduce the content of the organic matters in the wastewater, and remove suspended matters in the wastewater, so that the sewage quality of the membrane is better, and the subsequent pollution and blockage to the membrane are prevented.
(3) pH adjustment
And (3) conveying the supernatant after precipitation to a pH adjusting tank, adjusting the pH to 6.1-6.6 by adding acid, and conveying to a membrane reduction device.
(4) Film reduction
The CSM membrane reduction treatment is adopted in the step, and the membrane reduction device comprises a water inlet storage tank, a membrane element, a water inlet pump, a booster pump, a circulating pump and a cleaning system. A membrane system of the device adopts two-section operation, an RE8040SN membrane element is adopted, and the first section and the second section are mutually connected in series, namely, a first section of mother liquid enters the second section of membrane element, a first section of clear liquid and a second section of clear liquid are combined and enter an evaporative crystallization device, and a second section of concentrated liquid is sprayed back to an incinerator or a landfill. The method comprises the following specific steps: the supernatant of the pH adjusting tank is conveyed to a CSM membrane reduction device through a lift pump, and the inflow is controlled to be 10-30 m3After being pressurized by a booster pump, the first-stage membrane element is conveyed by a first-stage circulating pump, the yield of the first-stage clear liquid is controlled to be 80-85%, and the operating pressure is less than 4.5 MPa; conveying the first-stage concentrated solution produced water to a second-stage membrane element through a second-stage circulating pump, controlling the yield of second-stage clear liquid to be 75-80%, and operatingThe pressure is less than 6 MPa; wherein, the second section of concentrated solution produced water is collected by a special concentrated solution box, and the first section of clear water and the second section of clear water are merged and enter an evaporation unit; meanwhile, the device is provided with a cleaning system, and a membrane system is cleaned regularly, so that the operation stability is ensured. The water flow direction in the cleaning process is consistent with that in the operation process, the inlet water in the cleaning process is recycled water, and the chemical cleaning frequency is used for periodically carrying out chemical cleaning according to the membrane pollution condition. In the step, the total yield of the clear liquid is 95-97% in total, the total content of the mother liquid is 3-5% in total, and the main component is humic acid substances.
Humic acid substances can be removed through reduction treatment with low cost, the COD concentration of the obtained clear liquid is 1000-2000 mg/L, the ammonia nitrogen concentration is 0-2 mg/L, the COD concentration of the mother liquid is 4000-10000 mg/L, and the ammonia nitrogen concentration is 20-60 mg/L, the liquid yield of the clear liquid obtained through the reduction treatment is high, and the clear liquid is suitable for subsequent evaporation treatment.
After organic matters such as humic acid and the like are removed in the step, not only can the subsequent evaporation process be prevented from bubbling easily, and the stable water outlet is ensured, but also salt is separated out easily in the subsequent evaporation process, water vapor is discharged easily, the treatment power consumption is lower, and the cost is lower; and the salt content of the residual substance after evaporation is relatively increased, the viscous substance is relatively reduced, the caking is not easy, and the cleaning is simple.
(5) Evaporation of
The evaporation device comprises a water inlet unit, a circulating unit, a recovery unit, a steam supplementing unit and an external concentrated solution discharging unit. The step of evaporating comprises: the method comprises the steps of uniformly mixing a reducing clear liquid and an antifoaming agent, wherein the addition amount of the antifoaming agent is 0.01-0.05% of the mass of the reducing clear liquid, lifting the mixed liquid to a secondary heat exchanger through a lifting pump for preheating, then feeding the mixed liquid into a main heat exchanger through a water inlet pump through a circulating pump, finally conveying the mixed liquid to an evaporating tank for evaporation, controlling the temperature in the evaporating process to be 105-110 ℃, compressing steam generated by evaporation in a mechanical steam compressor, heating and boosting the steam by the steam compressor, then feeding the steam to a cleaning end of the main heat exchanger, transmitting the high-temperature and high-pressure steam to circulating concentrated water through plates of the heat exchanger in the main heat exchanger, condensing the steam after heat exchange into water, preheating the inlet water by a condensate in the secondary heat exchanger, and cooling the produced condensate water.
After evaporation and crystallization by the device, the effluent of condensed water can reach the standard of table 2 of GB 16889-2008, wherein the COD concentration of main indexes is 20-80 mg/L, the ammonia nitrogen concentration is 0-5 mg/L, the yield of the condensed water can reach 90-95% by mass percent, the COD concentration of the obtained evaporation concentration mother liquor is 20000-50000 mg/L, the TDS concentration is 400000-600000 mg/L, the mother liquor accounts for about 5-10% (concentration multiple is 10-20 times), the amount of the mother liquor is small, and the condensation water can be directly used for back spray of an incinerator or solidification backfill of a landfill.
The advantage that the multiple of concentration is high: 1. the treatment cost is low; 2. the reduction degree is high, and the residual pollution is greatly reduced; 3. the equipment obtains the maximum benefit. 4. The clear water yield is increased.
(6) Discharging
And (4) cooling the evaporated condensate water, and discharging after the detection reaches the standard.
In the invention, the yield of the total clear liquid is up to more than 85%, the treatment cost is low, the zero emission standard of pollutants is finally realized, the condensed water generated in the treatment process reaches the emission standard, a small amount of sludge is generated by flocculation precipitation, the extracted humic acid part and the amount of mother liquor generated by evaporation are relatively small, the condensed water can be sprayed back to the incinerator, and the generated slag is used for landfill of ash waste.
Example 1
The invention relates to a process for deeply treating membrane filtration concentrated solution of landfill leachate, which has a process flow diagram shown in figure 1 and comprises the following steps:
(1) the landfill leachate generated in a landfill site for 10 years is subjected to water inlet, water quality balance and external MBR +
Treating by a UF + NF/RO system + standard discharge treatment process, wherein nanofiltration and reverse osmosis membrane filtration concentrated solution are generated in the treatment process, and the generation amount is 240 t/d. And (3) conveying the generated NF concentrated solution and RO concentrated solution to a pretreatment regulating reservoir by using a lifting pump, and then mixing and blending to obtain blended solution with a COD value of 2553mg/L, an ammonia nitrogen concentration of 8mg/L and a TDS of 27500 mg/L.
(2) Adding ferric chloride and polyacrylamide into the prepared liquid obtained in the step (1), wherein the addition amount of the ferric chloride is 0.18 wt% of the total amount of the prepared liquid, the addition amount of the polyacrylamide is 0.003 wt% of the total amount of the prepared liquid, uniformly stirring by using a stirrer, carrying out coagulation reaction for 2 hours, precipitating and removing flocs generated after flocculation, and obtaining supernatant with a COD value of 1972mg/L and an ammonia nitrogen concentration of 7.5 mg/L.
(3) And (3) adjusting the pH of the supernatant obtained in the step (2) to 6.4 by using 33wt% of concentrated hydrochloric acid, feeding the supernatant into a membrane reduction device, controlling the yield of the first-stage clear liquid to be 82% and the yield of the second-stage clear liquid to be 78%, extracting the interception concentrated solution of the humic acid part to be 3.96%, controlling the ratio of the clear liquid to be 96.04%, controlling the COD value of the clear liquid to be 1520mg/L, controlling the ammonia nitrogen concentration to be 1.8mg/L and controlling the TDS concentration to be 21800 mg/L.
(4) Uniformly mixing the clear liquid obtained in the step (3) with an antifoaming agent, wherein the addition amount of the antifoaming agent is 0.04 wt% of the clear liquid, lifting the clear liquid to an evaporation tank, controlling the temperature at 108 ℃, controlling the yield of condensed water at 93%, and controlling the main control indexes of the condensed water effluent: the COD value is 68mg/L, the ammonia nitrogen is 2.1mg/L, the pH =7.71 and the K =363 us/cm.
Through detection, various indexes of the final condensed water effluent reach the standard of table 2 of GB 16889-2008, the total clear liquid yield in the whole process is 89.32%, a small amount of sludge is generated by flocculation and precipitation in the treatment process, 3.96% of trapped concentrated solution of humic acid part is extracted, and 6.72% of mother solution generated by evaporation is directly returned to the landfill.
Example 2
The invention relates to a process for deeply treating membrane filtration concentrated solution of landfill leachate, which has a process flow diagram shown in figure 1 and comprises the following steps:
(1) the landfill leachate generated in a 15-year landfill site is subjected to water inlet, water quality balance and external MBR +
Treating by a UF + NF/RO system + standard discharge treatment process, wherein nanofiltration and reverse osmosis membrane filtration concentrated solution are generated in the treatment process, and the generation amount is 640 t/d. And conveying the generated NF concentrated solution and RO concentrated solution to a pretreatment regulating reservoir by using a lifting pump, and then mixing and blending to obtain blended solution with a COD value of 3250mg/L, ammonia nitrogen of 7mg/L and TDS of 32700 mg/L.
(2) Adding ferric chloride and polyacrylamide into the prepared liquid obtained in the step (1), wherein the addition amount of the ferric chloride is 0.26wt% of the total amount of the prepared liquid, the addition amount of the polyacrylamide is 0.004wt% of the total amount of the prepared liquid, uniformly stirring by a stirrer, carrying out coagulation reaction for 2 hours, precipitating and removing flocs generated after flocculation, and obtaining supernatant with a COD value of 2764mg/L and an ammonia nitrogen concentration of 6.6 mg/L.
(3) And (3) adjusting the pH of the supernatant obtained in the step (2) to 6.5 by using 34wt% of concentrated hydrochloric acid, feeding the supernatant into a membrane reduction device, controlling the yield of the first-stage clear liquid to be 81% and the yield of the second-stage clear liquid to be 77%, extracting the interception concentrated solution of the humic acid part to be 4.37%, the clear liquid to be 95.63%, wherein the COD value of the clear liquid is 1938mg/L, the ammonia nitrogen concentration is 1.6mg/L, and the TDS concentration is 27600 mg/L.
(4) Uniformly mixing the clear liquid obtained in the step (3) with an antifoaming agent, wherein the addition amount of the antifoaming agent is 0.05 wt% of the clear liquid, lifting the clear liquid to an evaporation tank, controlling the temperature at 109 ℃, controlling the yield of condensed water at 92%, and controlling the main control indexes of the condensed water effluent: the COD value is 77mg/L, the ammonia nitrogen concentration is 2.8mg/L, the pH is =7.59, and the K is =337 us/cm.
Through detection, various indexes of the final condensed water effluent reach the standard of table 2 of GB 16889-2008, the total clear liquid yield in the whole process is 87.98%, a small amount of sludge is generated by flocculation precipitation in the treatment process, 4.37% of trapped concentrated solution of humic acid is extracted, and 7.65% of mother solution generated by evaporation is directly sprayed back to the incinerator.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present invention, or modify equivalent embodiments to equivalent variations, without departing from the scope of the invention, using the teachings disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.
Claims (8)
1. A process for reducing the membrane filtration concentrated solution of landfill leachate is characterized by comprising the following steps:
s1, blending and mixing the NF concentrated solution and the RO concentrated solution to obtain a blended solution, wherein the COD concentration in the blended solution is 2500-4000 mg/L, and the ammonia nitrogen concentration is 5-20 mg/L;
s2, adding ferric chloride and polyacrylamide into the blended liquid, stirring, and performing flocculation precipitation to obtain supernatant and sludge;
s3, adjusting the pH value of the supernatant to 6.1-6.6, and then carrying out two-stage CSM membrane reduction treatment to obtain a clear liquid and an entrapped concentrated liquid; in the two-section CSM membrane reduction treatment, the operating pressure of the first-section membrane treatment is less than 4.5MPa, and the concentrated solution obtained by the first-section membrane treatment is subjected to second-section membrane treatment, wherein the operating pressure of the second-section membrane treatment is less than 6 MPa; the yield of the first-stage clear liquid subjected to the first-stage membrane treatment is 80-85%, and the yield of the second-stage clear liquid subjected to the second-stage membrane treatment is 75-80%;
s4, evaporating the clear liquid obtained in the step S3 to obtain concentrated mother liquid and condensed water obtained through condensation;
before the clear liquid is evaporated, the method also comprises the steps of uniformly mixing the clear liquid with a defoaming agent and carrying out preheating treatment;
and S5, returning the sludge obtained in the step S2, the trapped concentrated solution obtained in the step S3 and the concentrated mother solution obtained in the step S4 to a landfill or an incinerator for incineration treatment.
2. The process for reducing the amount of a concentrated liquid of membrane filtration of landfill leachate according to claim 1, wherein in step S3, the total amount of the supernatant is 95 to 97% by mass;
the COD concentration of the clear liquid is 1000-2000 mg/L, and the ammonia nitrogen concentration is 0-2 mg/L.
3. The process for reducing the amount of a concentrated liquid of a membrane filtration of landfill leachate according to claim 1, wherein in step S3, the membrane elements of the first membrane treatment and the second membrane treatment are both RE8040SN membrane elements.
4. The process for reducing the amount of a landfill leachate membrane filtration concentrate of claim 1, wherein in step S3, the amount of the retained concentrate is 3 to 5% by mass of the supernatant;
the COD concentration of the intercepted concentrated solution is 4000-10000 mg/L, and the ammonia nitrogen concentration is 20-60 mg/L.
5. The process for the quantitative reduction of a membrane filtration concentrate according to any one of claims 1 to 4, wherein in step S4, the amount of condensed water is 90 to 95% by mass of the clear liquid; the COD concentration of the condensed water is 20-80 mg/L, and the ammonia nitrogen concentration is 0-5 mg/L.
6. The process for reduction of the liquid membrane filtration concentrate of landfill leachate according to any one of claims 1 to 4, wherein in step S4, the amount of the concentrated mother liquor is 5 to 10% of the mass of the clear liquid; the COD concentration of the concentrated mother liquor is 20000-50000 mg/L, and the TDS concentration is 400000-600000 mg/L.
7. The process for reduction of liquid membrane filtration concentrate according to any one of claims 1 to 4, wherein in step S2, the amount of ferric chloride added is 0.15 to 0.35% by mass of the total amount of the solution after blending, and the amount of polyacrylamide added is 0.002 to 0.008% by mass of the total amount of the solution after blending.
8. The process for the reduction of a membrane filtration concentrate according to any one of claims 1 to 4, wherein the evaporation temperature in step S4 is 105 to 110 ℃.
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