CN113200634A - Biogas slurry coprecipitation-electrodialysis purification process - Google Patents

Biogas slurry coprecipitation-electrodialysis purification process Download PDF

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CN113200634A
CN113200634A CN202110590557.5A CN202110590557A CN113200634A CN 113200634 A CN113200634 A CN 113200634A CN 202110590557 A CN202110590557 A CN 202110590557A CN 113200634 A CN113200634 A CN 113200634A
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biogas slurry
coprecipitation
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莫雅慧
陈美珠
魏曦玟
邓海波
邵含笑
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Central South University of Forestry and Technology
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
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    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/16—Nitrogen compounds, e.g. ammonia
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
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    • C02F2101/38—Organic compounds containing nitrogen

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Abstract

The invention discloses a biogas slurry coprecipitation-electrodialysis purification process, which belongs to the technical field of agricultural environment treatment and comprises the following steps: s1, biogas slurry coprecipitation: with CaO-AlCl3The method is characterized in that the method is a coprecipitator, and the biogas slurry is subjected to coprecipitation in a coprecipitation device to obtain true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen; s2, electrolysis-electrodialysis: introducing the true solution A containing true soluble state micromolecule organic matter and high-content ammonia nitrogen obtained in the step S1 into electrolysis-electroosmosisAnd the analyzer refers to the limit voltage, and increases the direct-current voltage to convert the ammonia water into ammonium ions, and then separates the ammonium ions from the true solution A through an electrodialysis process to concentrate the ammonium ions to obtain the fresh water reaching the standard. The invention solves the problem of environmental pollution caused by the current biogas slurry in a farm, and can remove COD, water-soluble phosphorus, heavy metals, ammonia nitrogen and antibiotics in the biogas slurry.

Description

Biogas slurry coprecipitation-electrodialysis purification process
Technical Field
The invention relates to the technical field of agricultural environment treatment, in particular to a biogas slurry coprecipitation-electrodialysis purification process.
Background
The large-scale farm is a meat supply source for the whole society. Organic wastewater and part of organic solid waste generated by the large-scale cultivation farm are usually gathered into a methane tank and generate methane as renewable energy through anaerobic fermentation, and the generated methane slag and methane liquid are also regarded as crop fertilizer which can return to the farm land. However, in the paddy field with much rainfall and low farm land topography in the plains of the hills in the south of China, biogas slurry discharged from a large-scale farm enters the paddy field to form eutrophication pollution, which causes serious damage to cultivated land and water body environment quality. Therefore, purification of biogas slurry is a major environmental issue that remains to be solved at present.
Aiming at the treatment of biogas slurry in pig farms in south China, in recent years, aeration biological oxidation method for removing biochemically organic matter and flocculation method for reducing COD are widely implemented in south China-The combined process of removing ammonia nitrogen by a stripping method reduces the content of pollutants such as COD (chemical oxygen demand), ammonia nitrogen and the like in the biogas slurry (similar to the invention patent 201110147233.0), but the process has high energy consumption and unsatisfactory treatment effect, and meanwhile, the content of antibiotics in the biogas slurry cannot be reduced, thus objectively causing the lack of the implementation intention of a farm.
Another currently popularized way to reduce biogas slurry pollutants is to dilute ammonia nitrogen concentration of biogas slurry by using wetlands such as rice fields and oxidation ponds, and then absorb ammonia nitrogen by using organisms such as bacteria and algae, thereby achieving the purpose of reducing ammonia (for example, patent nos. 201210018944.2, 202010122002.3, 202110173831.9 and 201710041473. X). In the method, colloidal and granular organic matters which are difficult to degrade by biogas slurry are precipitated in the paddy wetland, so that the COD content is reduced, and meanwhile, the bacteria and algae can be harvested to serve as animal feed. The mode has good effect of reducing ammonia nitrogen in the biogas slurry, but has insurmountable limitation. Firstly, a large amount of antibiotics in the biogas slurry cannot be removed, and the environment is still threatened by pollution; secondly, the implementation of the method requires large-area wetland such as paddy field, and most of common farms do not have the condition; thirdly, biogas slurry remains in the paddy field for a long time, and it leaks downward to cause groundwater pollution.
Aiming at recycling nitrogen and phosphorus in biogas slurry, struvite method (as in patent invention 201410062868.4) and biogas slurry high-temperature evaporation ammonia nitrogen absorption method (as in patent invention 201610603815.8) are widely researched and applied at home and abroad. The former is to fix phosphorus and ammonia nitrogen in the biogas slurry by a struvite crystallization method, and the latter is to boil the biogas slurry to evaporate ammonia and then absorb the ammonia with acid solution. The two methods mainly aim at the recovery of nitrogen and phosphorus in the biogas slurry, but neglect the treatment of antibiotics in the biogas slurry in the technical process, and have the disadvantages of complex process, high cost and difficult popularization in China.
In the aspect of application research, domestic scholars research the feasibility of realizing biogas slurry volume reduction by a negative pressure concentration method (such as the invention patent 201510407545.9) and a nanofiltration concentration method. Researches find that although the two methods reduce the volume of the biogas slurry to a certain extent, the ammonia nitrogen concentration efficiency of the former method is low, the operation of the latter method needs to keep a lower pH value, and the two methods have high energy consumption and low feasibility.
In addition, the research reports that organic matters, nitrogen and phosphorus and antibiotics of the biogas slurry are degraded by an ultrasonic wave + SBR method, an electrochemical method, a microwave method and AOPs (advanced oxidation methods) are also provided in China, the mechanisms of the methods are that the removal rate of pollutants in the biogas slurry is improved by enhancing the oxidation efficiency of the pollutants in the biogas slurry, and the test effect is good. However, the application of ultrasonic waves and microwaves needs to consume a large amount of electric energy, the implementation process of the electrochemical technology also has the problems of easy blockage of a reactor, uneven water distribution and the like, most of researches are in a primary test stage, a process route is not mature, the treatment cost is high, and few reports on application practice are provided.
In conclusion, an economical and effective biogas slurry purification method and an economical and effective biogas slurry purification idea are not found by the predecessors at present. In view of the above, the invention provides a process capable of thoroughly removing COD, water-soluble phosphorus, heavy metals, ammonia nitrogen and antibiotics from biogas slurry.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a biogas slurry coprecipitation-electrodialysis purification process, which solves the problem of environmental pollution caused by the current biogas slurry in a farm and can remove COD, water-soluble phosphorus, heavy metals, ammonia nitrogen and antibiotics in the biogas slurry.
In order to achieve the purpose, the invention provides the following technical scheme:
a biogas slurry coprecipitation-electrodialysis purification process comprises the following steps:
s1 coprecipitation of biogas slurry
With CaO-AlCl3The method is characterized in that the method is a coprecipitator, and the biogas slurry is subjected to coprecipitation in a coprecipitation device to obtain true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen;
s2, electrolysis-electrodialysis
And (4) introducing the true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen obtained in the step (S1) into an electrolysis-electrodialysis device, referring to a limit voltage, and increasing a direct-current voltage to convert ammonia water into ammonium ions, and then separating the ammonium ions from the true solution A through an electrodialysis process and concentrating to obtain the fresh water reaching the standard.
More preferably: in the coprecipitate, AlCl3The volume ratio of the CaO to the CaO is 1: 2.5.
More preferably: the volume ratio of the biogas slurry to the coprecipitator is 1: (0.2-1).
More preferably: the volume ratio of the biogas slurry to the coprecipitator is 1: 1.
more preferably: in the step S1, the biogas slurry co-precipitation time is 60 min.
More preferably: the pH value of the biogas slurry is 5-9.
More preferably: the pH value of the biogas slurry is 9.
More preferably: in step S2, the membrane-to-membrane voltage was 20V, and the hydraulic retention time of the solution a was 15 min.
More preferably: in step S2, the water inlet flow rate of the electrolysis-electrodialysis device is 10-30L/h, and/or the pH of the solution A is 8.5.
More preferably: in step S2, a small molecular organic substance having an organic carbon concentration of 4% of the original organic carbon in solution a is added to solution a.
In conclusion, the invention has the following beneficial effects: the main purpose of the coprecipitation process is to remove granular and colloidal organic matters (COD) and water-soluble phosphorus in the biogas slurry, so that the obtained true solution A does not contain macromolecular organic matters, and the electrodialysis membrane of the true solution A cannot be blocked when electrodialysis is carried out in the later process. For the electrolysis-electrodialysis process, combining electrolysis with electrodialysis is a key technology for the process. Only in the presence of electrolysis process, the ammonia water can be converted into ammonium ion, so that the ammonium ion can be separated from true solution A by electrodialysis process and concentrated. The process has good water purification effect, good commercial utilization value and is worthy of great popularization.
The process can thoroughly separate suspended or dissolved organic matters (COD main source), ammonia nitrogen, phosphorus, antibiotics and heavy metals in the biogas slurry, so that the biogas slurry is purified. The purified water produced by the biogas slurry treated by the process of the invention reaches the standard and is discharged, and the produced by-products can be recycled, thus realizing the aim of thoroughly eliminating the pollution of the biogas slurry to the environment and recycling useful components in the biogas slurry.
Drawings
FIG. 1 is used to illustrate the effect of co-precipitant formulation on organic matter removal;
FIG. 2 is used to show the effect of co-precipitant addition on organic matter removal;
FIG. 3 is used to show the effect of reaction time on organic matter removal;
FIG. 4 is used for representing the effect of biogas slurry pH on organic matter removal;
FIG. 5 is used for reflecting the relationship between voltage and ammonia nitrogen and organic matter removal rate;
FIG. 6 is used for reflecting the relationship between the flow rate and the ammonia nitrogen and organic matter removal rate;
figure 7 is used to reflect the relationship of pH to ammonia nitrogen and organic matter removal rate.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
A biogas slurry coprecipitation-electrodialysis purification process comprises the following steps:
s1, biogas slurry coprecipitation to remove organic matters (shown as COD) and other substances in biogas slurry
With CaO-AlCl3And (3) coprecipitating the biogas slurry in a coprecipitation device to obtain true solution A containing true soluble micromolecular organic matters and high-amount ammonia nitrogen.
Preferably, CaO-AlCl is used3The coprecipitator is used for removing macromolecular refractory organic matters characterized by high COD, water-soluble phosphorus and heavy metal Cu2+、Zn2+Etc. to obtain precipitate containing organic matter, phosphorus, copper, zinc, etc. and NH3·H2O, micromolecular organic matter and a small amount of supernatant of anions and cations, namely a grade-clear treatment solution A (true solution A containing true soluble micromolecular organic matter and high-content ammonia nitrogen).
The coprecipitator has positive charges in water, after the coprecipitator and the biogas slurry are uniformly stirred, organic matters (shown as COD) with negative charges in the biogas slurry are combined with the coprecipitator to be rapidly precipitated, and simultaneously, water-soluble phosphorus and Ca dissociated from the coprecipitator2+Combining to form calcium phosphate precipitate to separate from biogas slurry, wherein copper and zinc ions in the biogas slurry are also separated from OH dissociated from the coprecipitate-Bond formation of Cu (OH)2、Zn(OH)2Precipitating and separating from the aqueous solution. The precipitate is deposited at the bottom of the coprecipitation device and separated from the supernatant, which now contains only a high amount of NH3·H2O, small molecular organic matter (such as antibiotics, etc.), and small amount of cation (such as Cl)-)。
The precipitate can be used as a soil conditioner of the potted nutrient soil after being dried, and the supernatant, namely the true solution A liquid containing true soluble state micromolecule organic matter and high amount of ammonia nitrogen enters the next procedure for continuous purification.
S2, electrolysis-electrodialysis is carried out to remove ammonia nitrogen and antibiotics in true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen;
introducing the true solution A containing true soluble small molecular organic matters and high-content ammonia nitrogen obtained in the step S1 into an electrolysis-electrodialysis device, referring to a limit voltage, increasing a direct current voltage to convert ammonia water into ammonium ions, separating the ammonium ions from the true solution A through an electrodialysis process, and concentrating to obtain the standard fresh water
Preferably, the true solution A containing true soluble small molecular organic matters (including antibiotics) and high-content ammonia nitrogen is introduced into an electrolysis-electrodialysis device, the limit voltage is referred, the direct current voltage is properly increased, and the electrolytic oxidation of the small molecular organic matters is strengthened to generate CO2，CO2With NH in solution A3·H2O to form NH4HCO3，NH4HCO3Ionization to form NH4 +And HCO3-The two are flowed out through a dense water gap by an electrodialysis membrane, and finally the removal of NH in the solution A is achieved3N and the purpose of the antibiotic. In addition, a small amount of Cl-in the true solution A is converted into ClO after electrolytic oxidation-，ClO-Oxidation of NH3·H2Conversion of O to NOx or N2. Fresh water flows out from a fresh water port of the electrolysis-electrodialysis device, and the fresh water reaches the standard and is discharged into the environment.
In the technical scheme, the main purpose of the coprecipitation process is to remove granular and colloidal organic matters (COD) and water-soluble phosphorus in the biogas slurry, so that the obtained true solution A does not contain macromolecular organic matters, and the electrodialysis membrane of the true solution A cannot be blocked when electrodialysis is carried out in the subsequent process. For the electrolysis-electrodialysis process, combining electrolysis with electrodialysis is a key technology for the process. Only in the presence of electrolysis process, the ammonia water can be converted into ammonium ion, so that the ammonium ion can be separated from true solution A by electrodialysis process and concentrated. Coprecipitator CaO-AlCl3The formula and dosage, the optimal pH value and other parameters are the key of the purification process.
Example 1: according to the step S1 in the biogas slurry coprecipitation-electrodialysis purification process, the coprecipitator AlCl is added in the embodiment3And optimizing the parameters of the mixture ratio of CaO and the mixture ratio of CaO.
The total dosage of the fixed mixed coprecipitator is 50mL, the pH value of the biogas slurry is 8.64, and the reaction is carried out for 1h at 25 ℃. As can be seen from FIG. 1, in AlCl3CaO in different volume ratios of 1:2.5The minimum content of organic matters in the treatment liquid is 41.16 mg.L < -1 >, and the removal rate reaches a higher value of 93 percent. When the coprecipitation agent is continuously added, the removal rate of organic matters is not obviously increased.
Example 2: according to the step S1 in the biogas slurry coprecipitation-electrodialysis purification process, parameters of the amount of the coprecipitation agent are optimized.
Fixed coprecipitator AlCl3The CaO proportion is 1:2.5, the pH of the biogas slurry is 8.64, and the total amount of the biogas slurry is 50 mL. As can be seen from FIG. 2, the organic matter removal rate of the biogas slurry is improved as the adding amount of the precipitator is increased, and the organic matter removal efficiency is increased from 43% to 93% when the adding amount of the precipitator is increased from 10mL to 50 mL. After the addition amount was more than 50mL, the removal rate hardly changed. The reason is that the organic matter content in the biogas slurry with a fixed volume is constant, and the reaction is close to equilibrium already when 50mL of coprecipitator is added, so that the addition is increased again, and the removal rate is almost not changed.
Example 3: according to the step S1 in the biogas slurry coprecipitation-electrodialysis purification process, parameters of coprecipitation action time are optimized.
Fixed coprecipitator AlCl3CaO proportion is 1:2.5, the adding amount is 50mL/50mL (coprecipitator/biogas slurry), the pH of the biogas slurry is 8.64, the reaction is carried out for different times (10, 30, 60, 90 and 120min) at 25 ℃, and the removal effect of the organic matters in the biogas slurry is researched. As can be seen from FIG. 3, the removal efficiency reaches 93% in 60min, and then the removal efficiency of organic matters in the biogas slurry tends to be stable.
Example 4: according to the step S1 in the biogas slurry coprecipitation-electrodialysis purification process, parameters of the pH of the biogas slurry are optimized.
Fixed coprecipitator AlCl3The CaO proportion is 1:2.5, the adding amount is 50mL/50mL (coprecipitator/biogas slurry), the reaction time is 1h, the room temperature is 25 ℃, and the organic matter removal effect of the biogas slurry is researched under different pH values (5, 6, 7, 8, 9 and 10). As can be seen from fig. 4, when the pH of the biogas slurry is in the range of 5 to 9, the removal of organic matter in the biogas slurry increases with increasing pH, and reaches a maximum of 94% at pH 9.
From examples 1 to 4, it can be seen that AlCl3Co-precipitation of-CaOIn the starch, AlCl3The optimal volume ratio of the solution (1g/L) to the CaO solution (10g/L) is 1: 2.5; relative to the volume of the biogas slurry, the optimal dosage of the coprecipitator is equal to the volume of the biogas slurry; the ideal action time is 1 h; the most suitable pH of the biogas slurry is 9.
Example 5: the organic matter content of the biogas slurry is 883mg/L, and the ammonia nitrogen content is 2051 mg/L. The contents of the main components of the supernatant (true solution a) obtained after the coprecipitation treatment under the above optimum parameters are shown in table 1.
TABLE 1 Main Components and contents of real solution A
Figure RE-GDA0003137799100000081
As can be seen from Table 1, after the coprecipitation treatment, organic matters are basically removed, the residual concentration of the true solution A is 53mg/L, and the removal rate is 94%; the ammonia nitrogen is hardly removed, the residual concentration is 1908mg/L, and the ammonia nitrogen removal rate is 7%.
Example 6: according to the step S2 in the biogas slurry coprecipitation-electrodialysis purification process, the influence of voltage on the removal rate of ammonia nitrogen and soluble organic matters in the solution A is explored in the embodiment.
The original mass concentration of the true solution A is 1908mg/L, the water inflow rate is 30L/h, the pH value is 6.5, the hydraulic retention time of the true solution A is 15min, the true solution A is added into an electrolysis-electrodialysis raw liquid tank for treatment, and the influence of different voltages on the removal rate of ammonia nitrogen and soluble organic matters in the true solution A is determined. As shown in fig. 5, the removal rates of ammonia nitrogen and dissolved organic matters in the solution a by electrodialysis were 88% and 100%, respectively, when the voltage was 20V. The result is similar to the result of ammonia nitrogen simulation wastewater treated by electrodialysis, and shows that the ammonia nitrogen treated by electrodialysis is not influenced by organic matters in the true solution A and is only related to the concentration of the ammonia nitrogen.
Example 7: according to the step S2 in the biogas slurry coprecipitation-electrodialysis purification process, the influence of the flow rate on the removal rate of ammonia nitrogen and soluble organic matters in the solution A is researched
The water inflow can change the pollutant load in the true solution A to a certain extent, thereby influencing the electrodialysis treatment effect. The original mass concentration of liquid ammonia nitrogen of the true solution A is 1908mg/L, the membrane pair voltage is 20V, pH is 6.5, and the hydraulic retention time of the true solution A is 15 min. And verifying the influence of different water inflow rates on the removal rate of ammonia nitrogen and dissolved organic matters in the true solution A. As shown in FIG. 6, as the inflow rate increases, the contents of residual ammonia nitrogen and soluble organic matters in the wastewater both decrease, and the removal rates of the ammonia nitrogen and the soluble organic matters increase. When the feed water flow is increased from 10L/h to 30L/h, the ammonia nitrogen removal rate is remarkably increased from 50% to 88%, and after the feed water flow is increased, the increase of the removal rate tends to be gentle.
The influence of the water inflow rate on the removal rate of the true dissolved organic matter is slightly different from that of ammonia nitrogen, and when the water inflow rate is 20L/h, the removal rate of the organic matter is close to 100 percent, and high reaction activity is shown.
Example 8: according to the step S2 in the biogas slurry coprecipitation-electrodialysis purification process, the influence of pH on the removal rate of ammonia nitrogen and soluble organic matters in the solution A is explored in the embodiment.
The nitrogen concentration of the liquid ammonia of the true solution A is 1908mg/L, the organic matter concentration is 53mg/L, the reaction voltage (membrane pair voltage) is 20V, the inflow rate is 30L/h, and the hydraulic retention time is 15 min. As can be seen from FIG. 7, the ammonia nitrogen removal rate changes with the increase of pH, and the ammonia nitrogen removal rate shows an S-shaped trend of decreasing, increasing and decreasing.
When the pH value is increased from 5.5 to 6.5, the removal rate of ammonia nitrogen is reduced from 92 percent to 88 percent, and at the moment, the ammonia nitrogen in the solution is mainly NH4 +The form exists. NH when pH increased from 6.5 to 8.53The ammonia nitrogen removal rate starts to increase slowly with increasing N content, reaches a maximum of 95% at pH 8.5, and then starts to decrease again as the pH increases.
Example 9: according to the step S2 in the biogas slurry co-precipitation-electrodialysis purification process, in this embodiment, to verify that the water-soluble small-molecule organic substance promotes ammonia nitrogen in the solution a, sucrose solutions with different concentrations are added to the solution a under the conditions that the nitrogen concentration of the solution a is 1908mg/L, the organic substance concentration is 53mg/L, the reaction voltage is 20V, the water inlet flow rate is 30L/h, the hydraulic retention time is 15min, and the pH value is 8.5, so that the added organic carbons are 1%, 2%, 3%, 4%, 5%, and 6% of the original organic carbon in the solution a, respectively. As shown in Table 2, when the sucrose solution was added to increase the concentration of organic carbon in the solution A by 4%, the ammonia nitrogen removal rate was 100%.
TABLE 2 Effect of increasing organic carbon concentration on ammonia nitrogen removal from true solution A
Figure RE-GDA0003137799100000101
Mechanism for removing ammonia nitrogen and true soluble organic matters in true solution A simultaneously by electrodialysis method
The solution A fed to the electrodialysis unit is the supernatant from which the precipitate is removed, and the main component is NH3·H2O and true soluble small molecule organic matter. Wherein real soluble micromolecular organic matter is combined with OH in alkaline primary treatment liquid-Or loss of H+And is negatively charged, so that they are driven by DC electric field to concentrate on anode, and near the anode they lose charge and are oxidized to form CO2. The reaction formula is as follows:
Figure RE-GDA0003137799100000102
NH in the vicinity of the anode at this time3·H2O with newly formed CO2Combine to form NH4HCO3. This reaction is an energy release process with reduced entropy, and is irreversible, and its reaction equation is as follows:
NH3·H2O+CO2→NH4HCO3+ Heat quantity
The pH value of the solution is exactly 8.5 when the ammonium bicarbonate is dissolved, and the dissolution balance is as follows:
Figure RE-GDA0003137799100000103
NH generated by dissolution in the weak alkaline environment4+And HCO3-The concentrated water of the positive ions and the concentrated water of the negative ions are respectively gathered by penetrating through the positive membrane and the negative membrane of the electrodialysis device under the driving of voltage, and the purified water without ammonia nitrogen flows out from the fresh water outlet, thereby achieving the purpose of primary treatment water purification.
CaO and AlCl3The market prices are 380 yuan/ton and 4000 yuan/ton respectively, and the cost for treating the biogas slurry coprecipitator per ton is 3.8 yuan. According to the formula of energy consumption, the following formula is obtained: operating voltage of 20V, treating 2L of water, wherein the current is 0.1A, the ammonia nitrogen removal rate reaches 100%, the ammonium ions in the wastewater reduce the current along with the increase of the hydraulic retention time of the wastewater in electrodialysis, the required current is reduced to the minimum when 15min is reached, and the power consumption is 10 at the moment-3kw.h, the electricity consumption per ton of water is 0.5 degree electricity, which is converted into 0.3 yuan; the added small molecular organic matters can be separated from other organic wastewater, and the cost is negligible. Therefore, the cost of treating biogas slurry per ton of water is not more than 4.2 yuan. Secondly, the concentrated ammonium water and the precipitate obtained from the purification process can be converted into commercial products through resource recycling, and the commercial value is obtained, so that the treatment cost can be offset. Therefore, the process has a good water purification effect, has a good commercial utilization value, and is worthy of great popularization.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that several improvements and modifications without departing from the principle of the present invention will occur to those skilled in the art, and such improvements and modifications should also be construed as within the scope of the present invention.

Claims (10)

1. A biogas slurry coprecipitation-electrodialysis purification process is characterized in that: the method comprises the following steps:
s1 coprecipitation of biogas slurry
With CaO-AlCl3The method is characterized in that the method is a coprecipitator, and the biogas slurry is subjected to coprecipitation in a coprecipitation device to obtain true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen;
s2, electrolysis-electrodialysis
And (4) introducing the true solution A containing true soluble small molecular organic matters and high-amount ammonia nitrogen obtained in the step (S1) into an electrolysis-electrodialysis device, referring to a limit voltage, and increasing a direct-current voltage to convert ammonia water into ammonium ions, and then separating the ammonium ions from the true solution A through an electrodialysis process and concentrating to obtain the fresh water reaching the standard.
2. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: in the coprecipitate, AlCl3The volume ratio of the CaO to the CaO is 1: 2.5.
3. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: the volume ratio of the biogas slurry to the coprecipitator is 1: (0.2-1).
4. The biogas slurry coprecipitation-electrodialysis purification process according to claim 3, characterized in that: the volume ratio of the biogas slurry to the coprecipitator is 1: 1.
5. the biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: in the step S1, the biogas slurry co-precipitation time is 60 min.
6. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: the pH value of the biogas slurry is 5-9.
7. The biogas slurry coprecipitation-electrodialysis purification process according to claim 6, characterized in that: the pH value of the biogas slurry is 9.
8. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: in step S2, the membrane-to-membrane voltage was 20V, and the hydraulic retention time of the solution a was 15 min.
9. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: in step S2, the water inlet flow rate of the electrolysis-electrodialysis device is 10-30L/h, and/or the pH of the solution A is 8.5.
10. The biogas slurry coprecipitation-electrodialysis purification process according to claim 1, characterized in that: in step S2, a small molecular organic substance having an organic carbon concentration of 4% of the original organic carbon in solution a is added to solution a.
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