CN112777888B

CN112777888B - Treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation

Info

Publication number: CN112777888B
Application number: CN202011550718.XA
Authority: CN
Inventors: 方迪; 周立祥
Original assignee: Nanjing Agricultural University
Current assignee: Nanjing Agricultural University
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2022-04-19
Anticipated expiration: 2040-12-24
Also published as: CN112777888A

Abstract

The invention belongs to the technical field of sludge harmlessness and recycling, and discloses a treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation. The method comprises the following steps: 1) adding granular sulfur simple substance S into sludge⁰Treating, namely treating the particles S in the sludge when the pH value of the sludge is 2.0-3.0⁰Taking out; 2) removing heavy metals from the sludge solid phase by sludge dehydration, and simultaneously generating acid wastewater containing heavy metal ions; 3) adding the residual sulfur simple substance S in a particle state into the acidic wastewater⁰And an electron donor, treating for a period of time to generate metal sulfide, raising the pH value of the wastewater, recovering the metal sulfide through natural sedimentation, and discharging the supernatant after reaching the standard. The 2 exactly opposite biotransformation processes of sulfur oxidation and sulfur reduction are coupled and linked, so that the aim of removing and recovering heavy metals from sludge is fulfilled, and closed cycle and near zero emission of the heavy metals in the whole treatment link are realized.

Description

Treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation

Technical Field

The invention belongs to the technical field of sludge harmlessness and recycling, and particularly relates to a treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation.

Background

The sludge discharged from the sewage treatment plant accumulates 50-80% of heavy metals in the sewage, and the content of the heavy metals such as Zn, Cu, Pb, Cr, Ni and the like in the sludge of the sewage treatment plant in cities and towns and industrial parks which are mixed with a large amount of industrial wastewater (such as mechanical production, semiconductor processing and metal surface treatment) can reach several hundred to several thousand mg/kg. In recent years, environmental hazards and social effects caused by the irregular disposal of sludge containing heavy metals have been frequently reported. The method for removing or recovering the heavy (noble) metals with high concentration in the sludge has great significance for solving the difficult problem of sludge outlet and expanding the resource utilization way of the sludge.

Sulfur (S) is an element of variable valence state, having different forms of oxidation state (S)₀、SO₄ ^2-、S^2-Etc.). Research reports that acidophilic sulfur oxidizing bacteria can reduce sulfur (S)⁰) The catalytic oxidation and acid production of the method can dissolve out 60-90% of heavy metal in the solid phase of the sludge, enter the liquid phase, and then remove the heavy metal in the sludge through sludge dehydration. Compared with the traditional chemical method (chemical leaching and the like), the biological sulfur oxidation method has the obvious advantages of environmental friendliness, low cost, easiness in engineering operation and the like.

However, from the existing theory and engineering research, the biological sulfur oxidation for removing the heavy metals in the sludge has certain limitations in the practical application at present. This is mainly due to: 1) powdered sulfur powder (S) is commonly used in the existing biological sulfur oxidation treatment of sludge⁰) As an energy source substance for microorganisms. Due to S⁰Is very hydrophobic and typically 50-60% of S remains at the end of the treatment⁰Not utilized by the microorganisms and finally left in the sludge. These residual sulphur powders are fine-grained and dispersed, cannot be recovered and can be continuously oxidized once exposed to air, causing the hazard of "secondary acidification" of the sludge. 2) The sludge after biological sulfur oxidation treatment can generate a large amount of wastewater rich in soluble heavy metal ions during dehydration. In most cases, the pH value of the wastewater is 2.0-3.0, and Cu²⁺，Zn²⁺，Pb³⁺And Ni²⁺The content of the same can reach dozens to hundreds of mg/L. If the bulky acid water containing heavy metals cannot be properly treated, secondary pollution is easily caused, and even the effect of removing the heavy metals in the solid phase of the front-end sludge is completely counteracted. Both of these problems severely limit the pace at which this technology is pushed to engineering applications on a large scale. Currently, for such low pH and heavy metal rich wastewater, lime neutralization (raising pH, precipitating heavy metals as hydroxides) or sulfate bioreduction (precipitating heavy metals as sulfides) is mainly used. However, many studies show that the lime neutralization method has a large lime consumption, and the metal sediments generated finally have large quantity, low purity and low recovery value; and sulfates are alsoThe original rule generally needs to add a large amount of nutrients (electron donors), so that the cost of wastewater treatment is extremely high, and the phenomena that the Chemical Oxygen Demand (COD) and toxic sulfides in the wastewater seriously exceed standards are easy to occur.

Through retrieval, for the removal of heavy metals in wastewater sludge, the prior art discloses related applications, for example, the application with chinese patent application No. 2018100638434 and publication date 2018.06.22 discloses a method for removing heavy metals in municipal sludge, comprising: A) carrying out ultrasonic pretreatment on the municipal sludge to obtain pretreated municipal sludge; B) inoculating the inoculated bacteria into the pretreated municipal sludge to obtain the inoculated municipal sludge; C) and carrying out bioleaching on the inoculated municipal sludge to obtain the municipal sludge without heavy metals. The method of the application can effectively remove heavy metals in the sludge, but does not consider the treatment of the strong acid wastewater which is formed after the treatment and is rich in a large amount of heavy metals.

For another example, the application with the publication date 2017.07.28 of the Chinese patent application No. 2017101500840 discloses a waste-free utilization method of sludge containing heavy metals, which comprises the following steps: step S1, bioleaching: adding acidophilic microorganisms into the sludge containing heavy metals for bioleaching treatment, and performing solid-liquid separation to prepare leaching residues and a leaching solution; step S2, copper extraction: extracting the leachate prepared in the step S1 by using a hydroximic extractant solution selective for copper to prepare a copper-containing extraction liquid and a raffinate A which can be used for separately recovering copper; step S3, extraction of chromium: adding sulfite into the raffinate A, adjusting the pH value of the solution to be less than or equal to 2.0, heating and adding phosphate to prepare chromium phosphate precipitate capable of independently recovering chromium; step S4, extraction of iron: and (4) treating the residual solution B after the chromium deposition in the step S3 with an oxidant, adjusting the pH value of the solution to 1.0-1.5, and adding sodium sulfate at the temperature of 80-95 ℃ to prepare the jarosite capable of independently recovering iron. The method of the application carries out heavy metal extraction by using an extraction reagent which is selective to metals, so that the cost is high, the operation is complicated, and secondary pollution is easily caused.

Based on the defects of the prior art, a new treatment method for removing and recovering heavy metals in wastewater sludge needs to be invented.

Disclosure of Invention

1. Objects of the invention

One of the purposes of the invention is to provide a treatment method for removing and recovering heavy metals from wastewater and sludge, which is simple in operation and free of secondary pollution, and is used for coupling and connecting 2 just opposite biotransformation processes of sulfur oxidation and sulfur reduction to respectively generate acid by biological sulfur oxidation under aerobic conditions, promote the dissolution of insoluble heavy metals in a solid phase of sludge, reduce the biological sulfur under anaerobic conditions to generate sulfides, and induce the precipitation of soluble heavy metals in a liquid phase, so that the purpose of removing and recovering the heavy metals from the sludge is achieved, and the closed cycle and near zero emission of the heavy metals in the whole treatment link are realized.

The invention also aims to provide a treatment method for removing and recycling heavy metals in wastewater and sludge, which has low energy consumption cost and high economic practicability.

2. Technical scheme

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation, which comprises the following steps:

1) adding granular sulfur into the sludge, treating for a period of time, and taking out the granular sulfur from the sludge when the pH value of the sludge reaches 2.0-3.0;

2) removing heavy metals from the sludge solid phase by sludge dehydration, and simultaneously generating acid wastewater containing heavy metal ions;

3) adding granular sulfur and an electron donor into the acidic wastewater, treating for a period of time to generate metal sulfide, raising the pH value of the wastewater, recovering the metal sulfide through natural sedimentation, and discharging the supernatant after reaching the standard.

The invention adds granular S into the sludge⁰(sulfur spheres or sulfur)Tablet), induces endogenous acidophilic sulfur oxidizing bacteria in sludge to convert S⁰Oxidizing and producing acid, dissolving heavy metal in the sludge from a solid phase and transferring the heavy metal into a liquid phase when the pH of the sludge is acidified to 2.0-3.0, and then, carrying out sulfur removal on residual particles in the sludge⁰Taking out; removing heavy metals from the sludge solid phase by sludge dehydration, and simultaneously generating acid wastewater containing heavy metal ions; adding residual granular sulfur S into acidic wastewater⁰And electron donor of endogenous sulfur reducing bacteria to initiate S reduction of endogenous sulfur reducing bacteria in waste water⁰Reduction to H₂S, inducing heavy metal ions in water to generate extremely insoluble sulfide precipitate; and finally, recovering heavy metal ions in the acidic wastewater through natural sedimentation.

As a preferred embodiment, the solid content of the sludge added in the step 1) is 1-10%, and S in a particle state in the step 1)⁰The concentration is 1-12 g/L.

As a preferred embodiment, the treatment conditions in step 1) are: treating for 5-15 days at 20-35 deg.C under stirring and aeration.

In a preferred embodiment, in step 3), the electron donor of the endogenous elemental sulfur-reducing bacteria includes any one or a combination of glucose, sodium lactate, ethanol, acetic acid, glycerol and pyruvic acid.

As a preferred embodiment, the particles S in the sludge are treated in the step 1)⁰And (3) after taking out, refluxing 10-50% of sludge in volume into the reactor for the next batch of treatment, and performing the step (2) on the remaining 50-90% of sludge.

As a preferred embodiment, the S in the form of particles in the step 3)⁰The adding concentration of the sulfur source is 0.25-5.0g/L, and the adding concentration of the electron donor of the endogenous sulfur simple substance reducing bacteria is 0.25-5.0 g/L.

As a preferred embodiment, the treatment conditions in step 3) are: treating at 20-40 deg.C under stirring and anaerobic condition for 3-7 days.

As a preferred embodiment, the metal sulfide obtained in the step 3) is used for recovering noble metal, S in the form of particles⁰Including sulfur spheres or sulfur tablets.

As a preferred embodiment, the time for natural settling in step 3) is 8 h.

As a preferred embodiment, the sludge dewatering conditions in step 2) are: high pressure filter pressing at 15-20Mpa for 30min or plate-frame filter pressing at 1.6Mpa for 30 min.

As a preferred embodiment, the invention provides a treatment method for removing and recovering heavy metals in sludge based on biological sulfur circulation, which comprises the following steps:

(1) and (3) biological sulfur oxidation for removing heavy metals in sludge: adding wastewater sludge with a solid content of 1-10% and 1-12g/L sulfur balls or sulfur sheets into a reactor, treating for 5-15 days under the conditions of stirring and aeration at 20-35 ℃, taking out and cleaning the residual sulfur balls or sulfur sheets for later use when the pH value of the sludge is reduced to 2.0-3.0, then refluxing (retaining) the sludge with a volume ratio of 10-50% in the reactor for the next batch of treatment, and carrying out the step (2) on the residual 50-90% of the sludge.

(2) Sludge dewatering: and (3) dehydrating by using a high-pressure squeezer or a plate-and-frame filter press to obtain dehydrated mud cakes with the water content of less than 60 percent and the acidic wastewater containing heavy metal ions. Neutralizing the dewatered mud cake with a small amount of lime to be used as building materials or incinerated; and (3) carrying out the step (3) on the acid wastewater containing the heavy metals.

(3) Recovering heavy metals in the acidic wastewater by reducing the elemental sulfur: and (2) adding a certain amount of wastewater and 0.25-5.0g/L of the sulfur balls or sulfur pieces left in the step (1) into the reactor, simultaneously adding 0.25-5.0g/L of an electron donor of endogenous elemental sulfur reducing bacteria, treating for 3-7 days under stirring and anaerobic conditions at 20-40 ℃, naturally settling effluent of the reactor, returning supernatant to a sewage plant, and recovering precious metals from sediments (metal sulfides).

3. Advantageous effects

(1) Compared with the prior art, the sulfur oxidizing bacteria and the sulfur reducing bacteria adopted by the invention are both derived from the sludge, and no additional addition is needed. Meanwhile, the invention provides the granular sulfur (sulfur balls or sulfur pieces) which is easy to recycle and is used for biological sulfur oxidation, and the residual sulfur can be recycled for biological sulfur reduction, thereby not only eliminating the hidden danger of residual secondary acidification of a large amount of powder sulfur in the traditional method, but also saving the treatment cost. In addition, the dosage of the medicament and the nutrient in the whole treatment process is less, the energy consumption cost is low, and the economic practicability is strong.

(2) The treatment method provided by the invention can convert heavy metals in the sludge into sulfides with higher purity and recoverability, realizes closed cycle and near zero emission of the heavy metals in the treatment process, and can obtain products with additional values while eliminating heavy metal pollutants.

(3) The treatment method provided by the invention can reduce the heavy metal content in the sludge to be below the pollutant control standard (GB4284-84) in agricultural sludge or the landscaping utilization standard (GB/T23486-2009), and the heavy metal content of the effluent meets the national comprehensive sewage discharge standard (GB 8978-1996).

Drawings

FIG. 1 is a schematic view of the process flow of biological sulfur cycle removal and recovery of heavy metals in wastewater sludge provided by the present invention.

Detailed Description

The following examples are intended to further illustrate the invention, but are not intended to limit the invention.

It should be noted that the terms "upper", "lower", "left", "right" and "middle" used in the present specification are for the sake of clarity, and are not intended to limit the scope of the present invention, and changes or adjustments of the relative relationship thereof may be made without substantial technical changes.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

As used herein, the term "about" is used to provide the flexibility and inaccuracy associated with a given term, measure or value. The degree of flexibility for a particular variable can be readily determined by one skilled in the art.

As used herein, at least one of the terms "is intended to be synonymous with one or more of. For example, "at least one of A, B and C" explicitly includes a only, B only, C only, and combinations thereof, respectively.

Concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the explicitly recited limit values of 1 to about 4.5, but also include individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges reciting only one numerical value, such as "less than about 4.5," which should be construed to include all of the aforementioned values and ranges. Moreover, such an interpretation should apply regardless of the breadth of the range or feature being described.

Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims.

Example 1

In the embodiment, the biological sulfur circulation is used for removing and recycling heavy metals from wastewater and sludge containing various heavy metal elements.

The sample is collected from a sludge concentration tank of a sewage treatment plant in a certain industrial park of Jiangsu, the solid content of the sludge is 3.2 percent, and the basic properties are shown in Table 1. Compared with the control standard of agricultural pollutants of sludge (GB4284-84), the content of heavy metals such as Zn, Cu, Cd, Ni and the like in the sludge exceeds 2-6.5 times.

TABLE 1 basic sludge Properties

The present embodiment is directed to the above sludge treatment, and the flow chart is shown in fig. 1, and includes the following steps:

biological elemental sulfur oxidation stage (sulfur spheres): adding sludge with a solid content of 3.2% and 8.0g/L sulfur balls into a biological sulfur oxidation reactor, carrying out blast aeration for 10 days at 25 ℃, reducing the pH of the sludge to 2.0, taking out the residual sulfur balls in the reactor, and washing with tap water for later use; subsequently, 20% (v/v) of the sludge in the reactor was retained, and the remaining sludge was press-dewatered by a high-pressure filter press.

And (3) a dehydration stage: squeezing under 15-20MPa for 30min to obtain heavy metal-containing acidic wastewater (Zn)²⁺、Cu²⁺、Ni²⁺And Cd²⁺Respectively 95, 42, 3.6 and 0.78mg/L) and dewatered cake (moisture content about 55%, Zn, Cu, Cd and Ni contents reduced to 272, 198, 3.7, 83mg/kg, respectively). And adding lime into the mud cakes to adjust the pH value to 6.5, placing the mud cakes in the air for 60 days at room temperature, and measuring the pH value of the mud cakes to be still 6.5, which indicates that the harm of 'secondary acidification' does not occur.

Biological elemental sulfur reduction stage (recovered residual sulfur spheres): adding the acidic wastewater, 0.25g/L sulfur balls and 0.25g/L glycerol into a biological sulfur reduction reactor, sealing and treating at 30 ℃ for 5 days, naturally settling the treated effluent in a sedimentation tank for 8 hours, and detecting the generated supernatant to obtain Zn²⁺、Cu²⁺、Ni²⁺And Cd²⁺The content of the metal sediments meets the national comprehensive sewage discharge standard (GB8978-1996), and the generated metal sediments are mainly ZnS, CuS, NiS and CdS through detection.

TABLE 2 Change in Properties before and after treatment of test sludge

Comparative example A

This comparative example is a control in which no particulate sulfur (powdered sulfur) was used in the biological sulfur oxidation stage, and no biological sulfur reduction treatment (lime neutralization) was used.

The sample was the same as example 1, and the comparative example was processed as follows:

biological sulphur oxidation stage (powdered sulphur): adding a certain volume of sludge and 8.0g/L of powdered sulfur into a biological sulfur oxidation reactor, carrying out blast aeration for 10 days at 25 ℃, and reducing the pH value of the sludge to 1.8; subsequently, 20% (v/v) of the sludge in the reactor was retained, and the remaining sludge was subjected to high-pressure filter-pressing dehydration.

And (3) a dehydration stage: squeezing under 15-20MPa for 30min to obtain heavy metal-containing acidic wastewater (Zn)²⁺、Cu²⁺、Ni²⁺And Cd²⁺97, 42, 3.5 and 0.8mg/L, respectively) and dewatered cake (moisture content about 55%, Zn, Cu, Cd and Ni contents reduced to 270, 198, 3.7, 83mg/kg, respectively). And adding lime into the mud cakes to adjust the pH value to 6.5, placing the mud cakes in the air for 60 days at room temperature, and then reducing the pH value of the mud cakes to 3.3, which indicates that residual powdered sulfur in the sludge is continuously oxidized and secondary acidification occurs.

Lime neutralization: adding the acidic wastewater and 4g/L lime into a neutralization pond, stirring for 5h, adding 50mg/L flocculant Polyacrylamide (PAM), stirring for 3h, centrifuging at 5000r/min for 10min, filtering, detecting the generated supernatant, and detecting Zn²⁺、Cu²⁺、Ni²⁺And Cd²⁺The content reaches the national sewage comprehensive discharge standard (GB8978-1996), but a large amount of metal sediments are generated at the same time, and the main component is CaSO by detection₄、Zn(OH)₂、Cu(OH)₂、Ni(OH)₂And Cd (OH)₂。

Comparative example B

The present comparative example is a control in which no particulate sulfur (powdered sulfur) was used in the biological sulfur oxidation stage, and no biological sulfur reduction treatment (biological reduction with sulfate) was performed.

A sulfate reduction stage: adding the acidic wastewater and 3.2g/L glycerol into a sulfate reduction reactor, sealing at 30 deg.C for 5 days, naturally settling the treated effluent in a sedimentation tank for 8 hr, and detecting Zn in the supernatant²⁺、Cu²⁺、Ni²⁺And Cd²⁺The content reaches the national sewage comprehensive discharge standard (GB8978-1996), but the Chemical Oxygen Demand (COD) in the effluent is nearly 2200mg/L, and sulfide (S)^2-) The content is about 200mg/L, which are all seriously out of limits.

Table 3 comparison of the effects of sludge heavy metal removal and recovery in example 1, comparative example a and comparative example B

Example 2

In the embodiment, the biological sulfur circulation removes and recovers only single high-concentration heavy metal Cu in the wastewater sludge of the copper electroplating.

The sample is electroplating sludge of a wastewater treatment plant in an electroplating industrial park of Shandong, the solid content of the sludge is about 30 percent, the pH value is 6.8, the sludge mainly contains copper, and the total copper content is 10280 mg/kg.

The treatment method for removing and recycling heavy metals in sludge based on biological sulfur circulation comprises the following steps:

biological elemental sulfur oxidation stage (sulfur tablet): adding electroplating sludge with the solid content of 3% and 12.0g/L sulfur sheets diluted by tap water into a biological sulfur oxidation reactor, uniformly stirring and aerating at 20 ℃ for 5 days, reducing the pH of the sludge to 3, taking out the residual sulfur sheets in the reactor, and cleaning the residual sulfur sheets by tap water for later use.

And (3) a dehydration stage: in a reactor10% (v/v) of the sludge remained, and the rest sludge was dewatered by a plate-and-frame filter press. Obtaining Cu-rich²⁺Acid wastewater (Cu)²⁺The content is 282mg/L) and dehydrated mud cakes (the water content is about 60 percent, the Cu content is 822mg/kg, and the sludge meets the landscaping utilization standard (GB/T23486-2009)). The pH of the mud cake is adjusted to 6.5 by adding lime, and the mud cake is still measured to be 6.5 after being placed in the air and stored for 60 days at room temperature, which indicates that the harm of 'secondary acidification' does not occur.

Biological elemental sulfur reduction stage (sulfur tablet): adding the Cu-containing material into a biological sulfur reduction reactor²⁺Sealing the wastewater and 5.0g/L sulfur flakes and 5g/L sodium lactate at 20 deg.C for 7 days, naturally settling the treated effluent for 8h, detecting the supernatant, and collecting Cu²⁺The content of the Cu-containing sediments accords with the national comprehensive sewage discharge standard (GB8978-1996), and the generated Cu-containing sediments are mainly CuS through detection and can be used for subsequent Cu extraction and recovery.

Example 3

The sample was the same electrolytic copper plating sludge as in example 2. The treatment method for removing and recycling heavy metals in sludge based on biological sulfur circulation comprises the following steps:

biological elemental sulfur oxidation stage (sulfur spheres + sulfur tablets): adding electroplating sludge with the solid content of 10 percent, 5g/L sulfur balls and 5g/L sulfur sheets diluted by tap water into a biological sulfur oxidation reactor, uniformly stirring and aerating at 35 ℃ for 15 days, reducing the pH of the sludge to 2.2, taking out the residual sulfur balls and sulfur sheets in the reactor, and washing the reactor by tap water for later use.

And (3) a dehydration stage: 50% (v/v) of the sludge in the reactor was retained, and the rest sludge was dewatered by a plate and frame filter press. Obtaining Cu-rich²⁺Acid wastewater (Cu)²⁺The content is 920mg/L) and dehydrated mud cakes (the water content is about 60 percent, and the Cu content meets the utilization standard of sludge landscaping (GB/T23486-2009)). The pH of the mud cake is adjusted to 6.5 by adding lime, and the mud cake is still measured to be 6.5 after being placed in the air and stored for 60 days at room temperature, which indicates that the harm of 'secondary acidification' does not occur.

Biological elemental sulfur reduction stage (using two steps of treatment): first, half volume of Cu-containing solution is added into a biological sulfur reduction reactor²⁺Waste water, 0.5g/L sulfur ball and 1.0g/L acetic acid, sealing and processing for 3 days at 40 ℃, at the moment, pumping the other half of Cu-containing material to be processed into the reactor²⁺Stirring and mixing the wastewater for 2h, naturally settling for 8h, detecting the generated supernatant, and detecting Cu²⁺The content of the sediment meets the national sewage comprehensive discharge standard (GB8978-1996), and the generated sediment containing Cu is mainly CuS and Cu through detection₂And the S mixture can be used for the subsequent extraction and recovery of Cu.

Claims

1. A treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur circulation is characterized by comprising the following steps: the method comprises the following steps:

1) adding granular sulfur simple substance S into sludge⁰Treating for a period of time, and when the pH value of the sludge reaches 2.0-3.0, adding the granular sulfur simple substance S in the sludge⁰Taking out;

2) removing heavy metals from a sludge solid phase through sludge dehydration to obtain acid wastewater containing heavy metal ions;

3) adding the residual sulfur simple substance S in a particle state into the acidic wastewater⁰And the electron donor is an electron donor of endogenous elemental sulfur reducing bacteria, the electron donor is treated for a period of time to generate metal sulfide, the pH value of the wastewater is increased, the metal sulfide is recovered through natural sedimentation, and the supernatant reaches the standard and is discharged.

2. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 1, wherein: the elemental sulfur S in the particle state in the step 1)⁰The concentration is 1-12 g/L.

3. The treatment method for removing and recovering heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 1 or 2, characterized in that: the treatment conditions of the step 1) are as follows: treating for 5-15 days at 20-35 ℃ under the conditions of stirring and aeration.

4. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 2, characterized in that: in the step 3), the electron donor of the endogenous elemental sulfur reducing bacteria comprises any one or a combination of glucose, sodium lactate, ethanol, acetic acid, glycerol and pyruvic acid.

5. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 2, characterized in that: in the step 1), the sulfur in the granular state in the sludge is added to the S⁰And (3) after taking out, refluxing 10-50% of the sludge by volume into the reactor for the next batch of treatment, and performing the step (2) on the rest 50-90% of the sludge by volume.

6. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 5, characterized in that: the elemental sulfur S in the particle state in the step 3)⁰The adding concentration of the sulfur source is 0.25-5.0g/L, and the adding concentration of the electron donor of the endogenous sulfur simple substance reducing bacteria is 0.25-5.0 g/L.

7. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 6, characterized in that: the treatment conditions of the step 3) are as follows: treating for 3-7 days under stirring and anaerobic conditions at 20-40 ℃.

8. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 7, wherein: the metal sulfide obtained in the step 3) is used for recovering noble metal, and the sulfur elementary substance S in the particle state⁰Including sulfur spheres or sulfur tablets.

9. The treatment method for removing and recycling heavy metals in wastewater sludge based on biological sulfur cycle as claimed in claim 8, wherein: the sludge dewatering conditions in the step 2) are as follows: pressing for 30min under 15-20MPa or performing plate-and-frame press filtration for 30min under 1.6 MPa.