CN113292214A - Heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties - Google Patents
Heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000011282 treatment Methods 0.000 title claims abstract description 37
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 30
- 230000008569 process Effects 0.000 title claims abstract description 30
- 239000010802 sludge Substances 0.000 claims abstract description 97
- 238000002386 leaching Methods 0.000 claims abstract description 60
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 58
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 29
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 18
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 16
- 229910052717 sulfur Inorganic materials 0.000 claims description 12
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- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical group N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 4
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
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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
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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Abstract
The invention discloses a heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties. The process parameters are set according to the specific physicochemical properties (total organic carbon, total nitrogen and acid consumption capacity) of the bottom sludge, so as to carry out classification treatment on the bottom sludge, and the subsequent process route can be divided into: 1) adding leaching functional bacteria and then performing bioleaching treatment; 2) carrying out bioleaching treatment by using indigenous bacteria of the bottom mud; 3) pre-acidifying or adding nutrient, and performing bioleaching treatment. The invention effectively solves the problem that the bottom mud is difficult to leach and acidify in the traditional bioleaching treatment, simplifies the other treatment process steps of the easily leached bottom mud, and further promotes the engineering application of the bottom mud bioleaching technology.
Description
Technical Field
The invention belongs to the field of heavy metal pollution treatment, and particularly relates to a heavy metal bioleaching method for bottom mud.
Technical Field
The bioleaching technology is a technology which utilizes the action of sulfur oxidizing bacteria to oxidize and reduce low-valent sulfur to form final products such as sulfuric acid and other intermediate products, leaches insoluble heavy metals in a solid phase into a liquid phase through direct action or indirect action of oxidation, reduction, proton attack, adsorption, complexation and other ways, and finally realizes the separation of heavy metal polluted solid and liquid. The technology originates from the microorganism hydrometallurgy in the middle of the 20 th century, and is gradually applied to the fields of electronic waste treatment, waste incineration fly ash, industrial polluted sludge and the like along with the development of science and technology. Meanwhile, in the process of scale water environment treatment in China in last twenty years and last two decades, a large amount of sediment polluted by heavy metals is generated by dredging, and the treatment and disposal of the sediment are urgent. Compared with the traditional physical and chemical methods, the bottom sludge heavy metal bioleaching technology has the advantages of milder reaction, lower operation cost and better subsequent dehydration performance of the bottom sludge, and is considered to be one of the promising treatment technologies for the heavy metal polluted bottom sludge.
However, most of the current process researches related to bioleaching treatment of heavy metal in bottom sludge are in laboratory pilot-scale test and pilot-scale test stages, and the stable operation of actual engineering is not realized. One important reason is that the physical and chemical properties of the bottom mud in different drainage basins are very different, which can affect the acidification effect of the bioleaching process, and thus the standardization difficulty of the leaching process parameters is increased. The lack of engineering experience, the heterogeneity of the bottom sludge and other problems cause the difficulty in popularization and application of the bottom sludge heavy metal bioleaching technology. Therefore, based on the research on the correlation between the physicochemical property of the bottom sludge and the leaching efficiency, a set of heavy metal bioleaching process suitable for various types of bottom sludge is formed, which is favorable for the popularization and the application of the technology.
Disclosure of Invention
The invention aims to provide a heavy metal removal bioleaching process for carrying out classification treatment based on the properties of bottom mud, which can carry out classification treatment on the bottom mud from different sources and realize leaching acidification.
The invention specifically adopts the technical scheme that:
a heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties comprises the following steps:
s1, aiming at the sediment to be treated polluted by the heavy metals, determining the physicochemical properties of the sediment and classifying the sediment according to the physicochemical properties:
classifying the sediment into a first type if the acid consumption capacity is more than or equal to 0.3 mol/kg;
classifying as a second type of bottom mud if the acid consumption is less than 0.3mol/kg, the total organic carbon content is less than 18g/kg and the total nitrogen content is less than 2 g/kg;
classifying the sludge as a third type if the acid consumption is less than 0.3mol/kg, the total organic carbon content is not less than 18g/kg and the total nitrogen content is not less than 2 g/kg;
the acid consumption capacity is calculated by taking the pH value of the bottom mud as an acidification end point;
s2, adjusting the bottom mud to be treated into a mud-water mixture with the water content of 95% -98%, and pretreating the mud-water mixture according to the classification of the bottom mud to be treated:
if the sludge to be treated is the first type of sludge, adding a leaching functional microbial inoculum from an external source after dropwise adding a dilute sulfuric acid solution into the sludge-water mixture until the pH value is 4;
if the bottom sludge to be treated is the second type of bottom sludge, a carbon source and a nitrogen source nutrient are required to be supplemented into the sludge-water mixture to ensure that the total organic carbon content is higher than 18g/kg and the total nitrogen content is higher than 2g/kg, or an exogenous leaching functional microbial inoculum is added into the sludge-water mixture;
if the bottom sludge to be treated is the third type of bottom sludge, the sludge-water mixture does not need to be pretreated;
s3, adding 3-10 g/L of sulfur matrix into the mud-water mixture treated in the S2;
s4, continuously carrying out oxygenation operation on the mud-water mixture treated in the step S3, so as to change the Eh of the mud-water mixture to form an environmental condition favorable for leaching, stopping oxygenation operation until the pH value of the mud-water mixture is less than 2.5, and regarding as reaching the leaching end point;
and S5, standing the mud-water mixture after reaching the leaching end point, discharging supernatant after mud-water separation, and dehydrating the mud at the lower layer to finish the bioleaching treatment.
Preferably, the method for detecting the acid consumption capability of the bottom mud comprises the following steps: gradually acidifying the sludge with the original pH A by using dilute sulfuric acid until the pH of the sludge is 4, and adding H consumed by the sludge in unit dry weight in the acidification process+The molar amount was calculated as acid buffer capacity B as acid consumption B/(a-4).
Preferably, the leaching functional microbial inoculum is one or more of leaching functional pure bacteria, bottom sludge source leaching mixed bacteria and sludge source leaching mixed bacteria.
Preferably, the carbon source is glucose.
Preferably, the nitrogen source is ammonium sulfate.
Preferably, the sulfur-based substance is sublimed sulfur powder or an agricultural sulfur matrix.
Preferably, the oxygenation is performed by aeration, shaking or stirring.
Compared with the prior art, the invention has the advantages and effects that:
the invention defines key process parameters for limiting the bioleaching feasibility, divides the bottom sludge into a difficult leaching type, a difficult leaching type and an easy leaching type according to three physical and chemical properties of total organic carbon, total nitrogen and acid consumption capacity of the bottom sludge, and provides theoretical guidance for bioleaching treatment of heavy metal in the bottom sludge. Different process routes are adopted for different types of bottom sludge, leaching acidification of all types of bottom sludge is finally realized, meanwhile, the process steps of bioleaching of part types of bottom sludge are simplified to a certain extent, the operation period is shortened, and the operation cost is reduced.
Drawings
FIG. 1 is a process scheme of the present invention;
FIG. 2 shows the final pH of the inoculated and unaerated groups;
FIG. 3 is a graph showing the effect of pre-acidification on the final pH of a difficult-to-leach substrate slurry under conditions of microbial contamination;
FIG. 4 is a graph of the effect of nutrient addition treatment on the final pH of the less leachable sludge without adding bacteria.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description.
The invention provides a heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties, wherein the process route is shown in figure 1, and the specific description is as follows:
1) and (3) detecting the total organic carbon and total nitrogen contents of the sediment to be treated polluted by the heavy metal, and detecting the acid consumption capacity (pH is 4).
The total organic carbon and the total nitrogen content are measured according to the corresponding national standard method, and the acid consumption capacity (pH 4) refers to the Acid Consumption Capacity (ACC) calculated by taking the pH 4 of the sediment as an acidification endpoint, and it should be noted that the measurement of the three indexes is performed by taking the dried sludge as an object, that is, the obtained indexes are all dry weight indexes. In the present invention, the acid-consuming capacity (pH 4) is measured as follows:
gradually acidifying the sludge with the original pH A by using dilute sulfuric acid until the pH of the sludge is 4, and adding H consumed by the sludge in unit dry weight in the acidification process+The molar amount was calculated as acid buffer capacity B as acid consumption B/(a-4).
The physicochemical properties thereof were determined and classified according to their physicochemical properties:
if the acid consumption capacity is more than or equal to 0.3mol/kg, classifying the sludge into a first type of bottom sludge, namely the bottom sludge difficult to leach;
if the acid consumption is less than 0.3mol/kg, the total organic carbon content is less than 18g/kg and the total nitrogen content is less than 2g/kg, the sludge is classified as the second type of bottom sludge, namely the difficult leaching type of bottom sludge;
if the acid consumption is less than 0.3mol/kg, the total organic carbon content is not less than 18g/kg and the total nitrogen content is not less than 2g/kg, the sludge is classified as a third type of sludge, namely easily leachable type sludge;
2) adjusting the bottom sludge to be treated into a mud-water mixture with the water content of 95% -98%, and pretreating the mud-water mixture according to the classification of the bottom sludge to be treated:
if the sludge to be treated is the first type of sludge, adding a leaching functional microbial inoculum from an external source after dropwise adding a dilute sulfuric acid solution into the sludge-water mixture until the pH value is 4;
if the bottom sludge to be treated is the second type of bottom sludge, a carbon source and a nitrogen source nutrient are required to be supplemented into the sludge-water mixture to ensure that the total organic carbon content is higher than 18g/kg and the total nitrogen content is higher than 2g/kg, or an exogenous leaching functional microbial inoculum is added into the sludge-water mixture;
if the bottom sludge to be treated is the third type bottom sludge, the sludge-water mixture does not need to be pretreated.
It should be noted that, in the invention, the form of the exogenous leaching functional microbial inoculum to be added is not limited, as long as the leaching of the heavy metal organisms in the bottom sludge can be promoted. The leaching functional bacteria agent can be one or more of leaching functional pure bacteria, bottom sludge source leaching mixed bacteria and sludge source leaching mixed bacteria. The leaching-functional pure bacteria are pure bacteria with bioleaching function, such as Acidithiobacillus caldus. The pure bacteria used for bioleaching mainly comprise Acidithiobacillus (Acidithiobacillus), the bacteria are rod-shaped and have no spores, the bacteria are inorganic autotrophic gram negative bacteria and can grow under aerobic conditions, the pure bacteria used for bioleaching comprise Acidithiobacillus ferrooxidans, thiobacillus thiooxidans, Acidithiobacillus caldus and the like, and all the pure bacteria can adopt commercial products. The mixed bacteria for leaching the substrate sludge source and the mixed bacteria for leaching the sludge source are both mixed bacteria which have complex components and have the bioleaching function, and the two mixed bacteria are obtained by domesticating indigenous bacteria in the substrate sludge/sludge through continuous bioleaching reaction.
In the present invention, the carbon source to be added may be glucose, and the nitrogen source to be added may be ammonium sulfate. Of course, any material that can provide a source of nutrients for both the carbon and nitrogen sources for the bioleaching process can be substituted.
3) Adding 3-10 g/L of sulfur matrix into the mud-water mixture treated in the step 2). The sulfur-based substance may be sublimed sulfur powder or agricultural sulfur matrix. Of course, any other reduced sulfur compound that can be oxidized and utilized by sulfur oxidizing bacteria during bioleaching may be substituted.
4) Continuously carrying out oxygenation operation on the mud-water mixture treated in the step 3), so as to change the Eh of the mud-water mixture to form an environmental condition favorable for leaching, and stopping oxygenation operation until the pH value of the mud-water mixture is less than 2.5, wherein the end point of leaching is considered to be reached. The oxygenation operation adopted by the invention can be aeration, oscillation or stirring, and the like, and any other operation capable of oxygenating the muddy water mixture can be used as an alternative.
5) And (3) standing the mud-water mixture after the leaching end point is reached, discharging supernatant after mud-water separation, and dehydrating the lower layer mud to finish the bioleaching treatment.
The invention will be further described with reference to the drawings and examples, but the scope of the invention is not limited thereto.
Example 1
Samples of bottom mud from 28 lakes in the northern part of Jiaxing city were collected and tested for total organic carbon content, total nitrogen content and acid consumption (pH 4). Wherein, the total organic carbon content and the total nitrogen content are measured by a national standard method, and the acid consumption (pH is 4) is measured by the following method: acid Buffering Capacity (ABC) of the bottom sludge is measured by a dilute sulfuric acid titration method. Weighing 5g of fresh sediment sample in dry weight, adding 150ml of ultrapure water, and then dropwise adding 1mol/L H2SO4And (3) placing the solution in a constant-temperature shaking incubator, shaking for 2 hours, detecting the pH value of the mud-water mixed solution, and recording the volume of acid added at the moment. Dropwise addition of H2SO4The solution was allowed to stand until the pH was lowered to 4, and the H consumed was calculated+The molar mass ratio to the dry weight of the sediment sample is the acid buffer capacity at pH 4, and is referred to as the acid buffer capacity (pH 4). Acid Consumption Capacity (ACC) is the average H consumed per pH+The molar amount, i.e., the amount of change in the acid buffer capacity from pH, was calculated as the acid consumption capacity at pH 4 (pH 4).
The results of measuring the physical and chemical properties of the 28 sediment samples are shown in Table 1.
Physicochemical Properties of bottom mud of 128 samples in Table
Firstly, the 28 sediment samples are subjected to the traditional bioleaching treatment, namely bioleaching is carried out after exogenous leaching functional bacteria are added. The specific operation method comprises the following steps: in a 250ml conical flask, 5g of bottom sludge in dry weight is weighed, 150ml of ultrapure water is added, 3g/L of sublimed sulfur powder is added, 3ml of leaching functional bacteria liquid obtained by enrichment culture is added, and 3 parallel bottom sludge samples are obtained. Meanwhile, bioleaching without adding exogenous bacteria is carried out, and the operation is the same as that of the traditional bioleaching except that leaching functional bacteria are not added. The Erlenmeyer flasks of all treatment groups were incubated in a constant temperature shaking incubator at 28 ℃ and 180 r/min. The pH was measured daily and periodically, and the system was kept constant by supplementing distilled water.
After 10 days bioleaching treatment, the final pH profile of all sediment samples is shown in figure 2: if the final pH is less than 2.5, which is defined as successful bioleaching acidification, it can be found that leaching can be realized only after bacteria are added to a part of sediment samples; leaching can be realized even if bacteria are not added to part of the bottom mud samples; the residual sediment sample can not realize leaching even if bacteria are added.
The biological leaching results of 28 bottom sludge samples and the physicochemical properties of the bottom sludge samples are integrated and classified, so that the acid consumption capacity (pH 4) average value of the bottom sludge samples which cannot be leached and acidified by adding bacteria is more than or equal to 0.3mol/kg, and the bottom sludge is defined as the bottom sludge which is difficult to leach; the acid consumption capacity (pH is 4) of a sediment sample which can be leached and acidified after bacteria are added is less than 0.3mol/kg, meanwhile, the total organic carbon content is lower than 18g/kg, the total nitrogen content is lower than 2g/kg, and the sediment is defined as difficult-to-leach sediment; and the acid consumption capacity (pH 4) of a leached and acidified substrate sludge sample can be less than 0.3mol/kg without adding bacteria, and meanwhile, the total organic carbon content is not less than 18g/kg and the total nitrogen content is not less than 2g/kg, and the substrate sludge is defined as the easy leaching type substrate sludge. The above results show that the sludge may be difficult to be acidified due to too high acid consumption (pH 4), and the feasibility of leaching acidification by indigenous bacteria of the sludge may be affected when the contents of total organic carbon and total nitrogen are high, and the leaching acidification by the sludge with low total organic carbon and total nitrogen contents may be achieved by adding the exogenous leaching functional bacteria.
In order to verify the reasoning, pre-acidification treatment is carried out on the difficult-to-leach bottom mud, namely before bioleaching treatment is carried out, dilute sulfuric acid solution is dropwise added into the mud-water mixture until the pH value is 4, and leaching functional bacteria are added; and for the sediment which is difficult to leach, before bioleaching treatment, a carbon source (glucose) and a nitrogen source (ammonium sulfate) nutrient are supplemented into the mud-water mixture, so that the total organic carbon content is higher than 18g/kg and the total nitrogen content is higher than 2 g/kg.
Table 228 sample points bottom mud physicochemical properties and leaching result classification
The bioleaching acidification results of the pretreated bottom mud difficult to leach and the bottom mud difficult to leach are shown in fig. 3 and 4. As can be seen from fig. 3, compared to the treatment group in which the leaching functional bacteria are directly added without any pretreatment, the leaching acidification can be finally achieved by adding the leaching functional bacteria to the non-leaching type sediment after the pre-acidification. As can be seen from fig. 4, compared to the treatment group without any pretreatment, the difficult-to-leach type sediment can be leached and acidified by indigenous bacteria of the sediment after the carbon source and the nitrogen source nutrients are added, and although the pH of all sediment samples cannot be reduced below 2.5, the acidification performance has been greatly improved. Certainly, the difficult leaching type bottom mud can also be added with leaching functional bacteria by direct external source, so that the bioleaching effect is improved.
According to the embodiment, before bioleaching treatment of the heavy metal in the bottom sludge, different pretreatment means can be adopted according to different physicochemical properties of the bottom sludge, and finally the purpose of removing the heavy metal in the bottom sludge is achieved.
The method effectively solves the problem that part of the bottom sludge is difficult to carry out effective leaching acidification in the traditional bioleaching treatment, provides more definite process indexes and parameters for the classification of the types of the bottom sludge, shortens the bioleaching treatment time to a certain extent, simplifies the treatment steps and the operation cost of part of the bottom sludge, and further promotes the engineering application of the bottom sludge bioleaching technology.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Those skilled in the art can make appropriate adjustments to the ranges of process parameters in the actual production run without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (7)
1. A heavy metal removal bioleaching process for carrying out classification treatment based on bottom mud properties is characterized by comprising the following steps:
s1, aiming at the sediment to be treated polluted by the heavy metals, determining the physicochemical properties of the sediment and classifying the sediment according to the physicochemical properties:
classifying the sediment into a first type if the acid consumption capacity is more than or equal to 0.3 mol/kg;
classifying as a second type of bottom mud if the acid consumption is less than 0.3mol/kg, the total organic carbon content is less than 18g/kg and the total nitrogen content is less than 2 g/kg;
classifying the sludge as a third type if the acid consumption is less than 0.3mol/kg, the total organic carbon content is not less than 18g/kg and the total nitrogen content is not less than 2 g/kg;
the acid consumption capacity is calculated by taking the pH value of the bottom mud as an acidification end point;
s2, adjusting the bottom mud to be treated into a mud-water mixture with the water content of 95% -98%, and pretreating the mud-water mixture according to the classification of the bottom mud to be treated:
if the sludge to be treated is the first type of sludge, adding a leaching functional microbial inoculum from an external source after dropwise adding a dilute sulfuric acid solution into the sludge-water mixture until the pH value is 4;
if the bottom sludge to be treated is the second type of bottom sludge, a carbon source and a nitrogen source nutrient are required to be supplemented into the sludge-water mixture to ensure that the total organic carbon content is higher than 18g/kg and the total nitrogen content is higher than 2g/kg, or an exogenous leaching functional microbial inoculum is added into the sludge-water mixture;
if the bottom sludge to be treated is the third type of bottom sludge, the sludge-water mixture does not need to be pretreated;
s3, adding 3-10 g/L of sulfur matrix into the mud-water mixture treated in the S2;
s4, continuously carrying out oxygenation operation on the mud-water mixture treated in the step S3, so as to change the Eh of the mud-water mixture to form an environmental condition favorable for leaching, stopping oxygenation operation until the pH value of the mud-water mixture is less than 2.5, and regarding as reaching the leaching end point;
and S5, standing the mud-water mixture after reaching the leaching end point, discharging supernatant after mud-water separation, and dehydrating the mud at the lower layer to finish the bioleaching treatment.
2. The bioleaching process for removing heavy metals based on bottom mud property classification treatment according to claim 1 is characterized in that: the method for detecting the acid consumption capacity of the bottom sludge comprises the following steps: gradually acidifying the sludge with the original pH A by using dilute sulfuric acid until the pH of the sludge is 4, and adding H consumed by the sludge in unit dry weight in the acidification process+The molar amount was calculated as acid buffer capacity B as acid consumption B/(a-4).
3. The bioleaching process for heavy metal removal according to claim 1, which is based on the classification of the bottom sludge properties, characterized in that: the leaching functional microbial inoculum is one or more of leaching functional pure bacteria, bottom sludge source leaching mixed bacteria and sludge source leaching mixed bacteria.
4. The bioleaching process for heavy metal removal based on bottom sludge property classification as claimed in claim 1, characterized in that: the carbon source is glucose.
5. The bioleaching process for heavy metal removal based on bottom sludge property classification as claimed in claim 1, characterized in that: the nitrogen source is ammonium sulfate.
6. The bioleaching process for heavy metal removal based on bottom sludge property classification as claimed in claim 1, characterized in that: the sulfur matrix is sublimed sulfur powder or agricultural sulfur matrix.
7. The bioleaching process for heavy metal removal based on bottom sludge property classification as claimed in claim 1, characterized in that: the oxygenation operation is aeration, oscillation or stirring.
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Citations (3)
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| JP2002355695A (en) * | 2001-05-31 | 2002-12-10 | Sumitomo Heavy Ind Ltd | Water treatment method and apparatus |
| CN105731750A (en) * | 2016-03-16 | 2016-07-06 | 福州大学 | Method for removing heavy metal in sludge by means of bioleaching by aid of mixed substrates |
| CN109970299A (en) * | 2019-03-28 | 2019-07-05 | 浙江大学 | The batch-type biology of heavy metal is from leaching technique in a kind of removal bed mud |
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| JP2002355695A (en) * | 2001-05-31 | 2002-12-10 | Sumitomo Heavy Ind Ltd | Water treatment method and apparatus |
| CN105731750A (en) * | 2016-03-16 | 2016-07-06 | 福州大学 | Method for removing heavy metal in sludge by means of bioleaching by aid of mixed substrates |
| CN109970299A (en) * | 2019-03-28 | 2019-07-05 | 浙江大学 | The batch-type biology of heavy metal is from leaching technique in a kind of removal bed mud |
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