A method for simultaneously removing lead and adsorbable organohalogenated compounds from wastewater

Abstract

This invention discloses a method for simultaneously removing lead and adsorbable organohalides from wastewater, comprising: (1) adding Shewanella bacteria to wastewater containing adsorbable organohalides under anaerobic conditions, adding a sulfur source, and reacting at 25-30°C for 12-36 hours; (2) adding lead-containing heavy metal wastewater to the reaction solution of step (1) under stirring conditions, and reacting for 12-24 hours; (3) allowing the mixture to stand for 12-24 hours after the reaction, and then effluent. This invention enables in-situ resource utilization of lead-containing heavy metals, achieving the goal of simultaneously removing lead and adsorbable organohalides from wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater. Background Technology

[0002] With economic development and social progress, lead is increasingly used in many fields, resulting in a corresponding increase in the amount of lead-containing wastewater generated. This wastewater typically originates from industries such as electroplating, mining, smelting, leather making, petroleum, coatings, pesticides, printing and dyeing, photography, and battery manufacturing, with the smelting industry emitting the most significant environmental impact.

[0003] Lead is a non-essential element for plants and animals, but it is highly toxic because it reacts with nitrogen and sulfur atoms on the side chains of amino acids. Lead combines with proteins and some enzymes in the human body, harming human health, accumulating in human organs, and eventually causing lead poisoning. Low concentrations of lead will not harm adults in the short term, but they can harm children. Early lead poisoning in children can cause slow development, difficulty walking, insomnia, and other symptoms. Long-term lead poisoning can eventually affect children's intellectual development and cause serious diseases such as hearing impairment. Lead can quickly enter various organs in the body through the bloodstream, causing serious harm. Lead has a long half-life in the human body and is difficult to eliminate naturally. Long-term presence of lead in the body can cause adverse reactions such as abdominal pain, palpitations, and headaches. When blood lead exists in the bones in the form of salts, it can also cause poor bone development in children and even cause mobility problems. At the same time, lead may also damage the nervous system in children, leading to intellectual disability. In addition, lead can cause anemia and seriously affect the human immune system and normal cellular metabolism. Lead can cause permanent intellectual impairment in children, with serious consequences. Children are far more likely to suffer from lead poisoning than adults. Reports of lead poisoning incidents are commonplace. Acute lead poisoning can severely affect the functioning of the nervous system, and in severe cases, it can even be fatal, as seen in cases of lead poisoning in children.

[0004] Compared to conventional methods such as chemical precipitation, electrolysis, ion exchange, and membrane separation, biological methods for removing lead are more economical, but they require overcoming the tolerance of living microorganisms to lead. Furthermore, lead in wastewater is both waste and a resource; therefore, developing technologies for the resource utilization of lead-contaminated wastewater is urgently needed.

[0005] Adsorbable organohalides (AOXes) are widely used in industry as raw materials and solvents. AOXes include chlorides, bromides, and iodides, but not fluorides. These substances are highly toxic, persistent, and bioaccumulative; their release into the environment can affect human health and endanger ecological security. Of the 129 priority pollutants identified by the U.S. Environmental Protection Agency, halogenated organic compounds account for approximately 60%. AOXes, characterized by their low biodegradability, have become an international water quality indicator. Conventional activated sludge processes have limited effectiveness in removing AOXes.

[0006] To date, there are few reported methods for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater. Summary of the Invention

[0007] This invention provides a method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater.

[0008] The technical solution of the present invention is as follows:

[0009] A method for simultaneously removing lead and adsorbable organohalogenated compounds from wastewater includes:

[0010] (1) Under anaerobic conditions, Shewanella bacteria were added to wastewater containing adsorbable organic halogenated compounds, and a sulfur source was added. The mixture was reacted at 25-30℃ for 12-36 hours.

[0011] (2) Under stirring conditions, lead-containing heavy metal wastewater is added to the reaction solution of step (1) and reacted for 12-24 hours;

[0012] (3) After the reaction is complete, let it stand for 12-24 hours and then drain the water.

[0013] The Shewanella species mentioned is *Shewanella oneidensis* MR-1, ATCC number 700550. This invention utilizes live Shewanella bacteria to synthesize nano-lead sulfide from wastewater. The synthesized nano-lead sulfide can adsorb adsorbable organic halogenated compounds (AOX) in the wastewater, achieving the resource utilization of lead-containing wastewater while simultaneously removing lead and AOX from the wastewater.

[0014] During the treatment of lead-containing wastewater, Shewanella bacteria slowly release H₂S using sulfur sources. - Alternatively, H2S and lead ions can be combined with microorganisms or extracellular polymers to synthesize lead sulfide nanomaterials. During the nucleation process, the lead sulfide nanomaterials adsorb AOX pollutants in the wastewater, thus enabling in-situ resource utilization of lead-containing heavy metals and achieving the goal of simultaneously removing lead and AOX from the wastewater. After adsorption, the pollutants are removed by sedimentation.

[0015] Lead is a highly toxic heavy metal, and Shewanella bacteria have difficulty surviving when directly added to lead-containing wastewater. This invention first reacts Shewanella bacteria with a sulfur source for a period of time to slowly generate HS. - Or H2S, then lead-containing heavy metal wastewater is introduced, and the introduced lead-containing heavy metal wastewater reacts with H2S. - Alternatively, it can react with H2S to form lead sulfide precipitate, which greatly reduces the toxicity of lead sulfide to microorganisms.

[0016] Preferably, before step (1), the bacteria are cultured at 25-30°C for 12-18 hours.

[0017] Furthermore, the culture medium for Shewanella includes: 5 g / L yeast extract, 10 g / L peptone, and 10 g / L sodium chloride.

[0018] Preferably, in step (1), the concentration of Shewanella in the wastewater is 3 × 10⁻⁶. 6 -7×10 6 CFU / ml.

[0019] Preferably, in step (1), the pH value of the wastewater containing adsorbable organic halogenated compounds is adjusted to 6-8.

[0020] More preferably, in wastewater containing adsorbable organic halogenated compounds, the concentration of adsorbable organic halogenated compounds is 1-80 mg / L, and the COD is 10-1000 mg / L.

[0021] Further preferred, in wastewater containing adsorbable organic halogenated compounds, the concentration of adsorbable organic halogenated compounds is 1-50 mg / L, and the COD is 10-500 mg / L.

[0022] Preferably, in step (2), the pH value of the lead-containing heavy metal wastewater is adjusted to 6-8.

[0023] Further preferred, the lead ion concentration in the lead-containing heavy metal wastewater is 1-1000 mg / L.

[0024] Preferably, in step (2), the volume ratio of the lead-containing heavy metal wastewater to the wastewater containing adsorbable organic halogenated compounds is 2-1:1.

[0025] Furthermore, in terms of molar amount, the amount of sulfur source added is 2-4 times that of lead ions.

[0026] The sulfur source can be at least one of thiosulfate, sulfite, and sulfur.

[0027] Preferably, the waste gas generated during the reaction is absorbed by alkaline solution.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] This invention first reacts Shewanella bacteria with a sulfur source for a period of time to slowly generate HS. - Or H2S, then lead-containing heavy metal wastewater is introduced, HS - Alternatively, H2S and lead ions can be reacted with microorganisms or extracellular polymers to synthesize lead sulfide nanomaterials. During the nucleation process, the lead sulfide nanomaterials adsorb AOX pollutants from wastewater, and the adsorbed pollutants are removed by sedimentation. This invention enables in-situ resource utilization of lead-containing heavy metals, achieving the simultaneous removal of lead and AOX from wastewater. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to the present invention.

[0031] Figure 2 XRD pattern of purified sediment from lead-containing wastewater.

[0032] Figure 3 Transmission electron microscope image of purified sediment from lead-containing wastewater. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0034] like Figure 1 As shown, this invention utilizes live Shewanella bacteria to synthesize nano-lead sulfide from lead in wastewater. The synthesized nano-lead sulfide can adsorb and remove adsorbable organic halogenated compounds (AOX) in wastewater, thereby achieving the resource utilization of lead-containing wastewater while simultaneously removing lead and AOX from the wastewater.

[0035] The specific steps are as follows:

[0036] (1) Shewanella oneidensis MR-1 (abbreviated as MR-1, ATCC number: 700550) was cultured in a culture medium at 25-30℃ for 12-18h;

[0037] (2) Add the cultured Shewanella bacteria to an anaerobic reactor containing AOX organic wastewater with pH adjusted to 6-8, add a sulfur source (thiosulfate, sulfite or sulfur), the amount of sulfur source added is 2-4 times that of lead heavy metal (in molar amount), and react at 25-30℃ for 24-36h.

[0038] (3) Under slow stirring at 60-80 rpm, lead-containing heavy metal wastewater with pH adjusted to 6-8 is introduced into the anaerobic reactor in (2). The volume ratio of lead-containing wastewater to AOX wastewater is 2-1:1, and the reaction continues for 12-24 hours.

[0039] (4) After the reaction, stop stirring and let it stand for 12-24 hours, then effluent. The waste gas is treated with alkaline solution.

[0040] The culture medium for Shewanella consisted of 5 g / L yeast extract, 10 g / L peptone, and 10 g / L sodium chloride.

[0041] Example 1

[0042] The wastewater from a certain company's workshop mainly contains lead ions, with a concentration of 812 mg / L. The wastewater also contains AOX, with a COD concentration of 480 mg / L and an AOX concentration of 42.6 mg / L.

[0043] The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater is as follows:

[0044] (1) Oda Nesshua was cultured at 30°C in a culture medium (5 g / L yeast extract, 10 g / L peptone, 10 g / L sodium chloride) for 12 h.

[0045] (2) The cultured *Shewanella audanae* was added to an anaerobic reactor containing AOX organic wastewater with a pH adjusted to 7, so that the concentration of *Shewanella audanae* was 5 × 10⁻⁶. 6 Approximately CFU / ml, add 8mM thiosulfate, and react at 30°C for 24 hours.

[0046] (3) While stirring slowly at 80 rpm, lead-containing heavy metal wastewater with pH adjusted to 7 was introduced into (2). The volume ratio of lead-containing heavy metal wastewater to AOX wastewater was 1:1, and the reaction continued for 24 h.

[0047] (4) Stop stirring after the reaction and let it stand for 24 hours.

[0048] After settling, the lead concentration in the effluent was 0.8 mg / L, and the AOX concentration was 6.02 mg / L. The waste gas was absorbed by alkaline solution. The lead concentration in the effluent met the requirements of the "Integrated Wastewater Discharge Standard" (GB 8978-1996), and the AOX concentration in the effluent met the Class III discharge standard (AOX < 8 mg / L) of the "Integrated Wastewater Discharge Standard" (GB 8978-1996).

[0049] After treating lead-containing wastewater, precipitates are formed in the water body, and these precipitates are collected. For example... Figure 2 As shown, the precipitate was purified and characterized as PbS by X-ray laser diffraction (XRD).

[0050] like Figure 3 As shown, transmission electron microscopy revealed that the PbS nanomaterials synthesized after treating lead-containing wastewater were rod-shaped after purification of the precipitate.

[0051] Comparative Example 1

[0052] The wastewater from a certain company's workshop mainly contains lead ions, with a concentration of 812 mg / L. The wastewater also contains AOX, with a COD concentration of 350 mg / L and an AOX concentration of 42.6 mg / L.

[0053] (1) Oda Nesshua was cultured at 30°C in a culture medium (5 g / L yeast extract, 10 g / L peptone, 10 g / L sodium chloride) for 12 h.

[0054] (2) The cultured *Shewanella audanae* was added to an anaerobic reactor containing AOX organic wastewater with a pH adjusted to 7, so that the concentration of *Shewanella audanae* was 5 × 10⁻⁶. 6 Add approximately CFU / ml of 8mM thiosulfate and, while stirring slowly at 80 rpm, uniformly introduce lead-containing heavy metal wastewater with pH adjusted to 7. The volume ratio of lead-containing heavy metal wastewater to AOX wastewater is 1:1, and the reaction is carried out for 48 hours.

[0055] (3) Stop stirring after the reaction and let it stand for 24 hours.

[0056] The effluent lead concentration was 402 mg / L, and the AOX concentration was 20.1 mg / L, which is essentially the concentration obtained by diluting lead-containing wastewater and AOX wastewater in a 1:1 volume ratio. No PbS was synthesized during the reaction. Because lead is toxic to microorganisms, direct mixing with lead would make it difficult for Shewanella bacteria to survive or function.

[0057] Comparative Example 2

[0058] The wastewater from a certain company's workshop mainly contains lead ions, with a concentration of 812 mg / L. The wastewater also contains AOX, with a COD concentration of 350 mg / L and an AOX concentration of 42.6 mg / L.

[0059] (1) Oda Nesshua was cultured at 30°C in a culture medium (5 g / L yeast extract, 10 g / L peptone, 10 g / L sodium chloride) for 12 h.

[0060] (2) The cultured *Shewanella audanae* was added to an anaerobic reactor containing AOX organic wastewater with a pH adjusted to 7, so that the concentration of *Shewanella audanae* was 5 × 10⁻⁶. 6 Add approximately CFU / ml of 8mM thiosulfate and stir slowly at 80 rpm for 48 hours.

[0061] (3) Stop stirring after the reaction and let it stand for 24 hours.

[0062] The waste gas was absorbed by alkaline solution. The AOX concentration in the effluent was 39.5 mg / L, indicating that microorganisms alone have very limited ability to remove AOX.

[0063] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater, characterized in that, include: (1) Adjust the pH of the wastewater containing adsorbable organic halogenated compounds to 6-8; the concentration of adsorbable organic halogenated compounds in the wastewater containing adsorbable organic halogenated compounds is 1-80 mg / L and the COD is 10-1000 mg / L. Under anaerobic conditions, Shewanella bacteria were added to wastewater containing adsorbable organic halogenated compounds to achieve a concentration of 3 × 10⁻⁶ bacteria in the wastewater. 6 -7×10 6 CFU / ml; then add a sulfur source and react at 25-30℃ for 12-36 hours; (2) Adjust the pH of the lead-containing heavy metal wastewater to 6-8; the lead ion concentration in the lead-containing heavy metal wastewater is 1-1000 mg / L; Under stirring conditions, lead-containing heavy metal wastewater is added to the reaction solution in step (1) and reacted for 12-24 hours; the volume ratio of the added lead-containing heavy metal wastewater to the wastewater containing adsorbable organic halogenated compounds is 2-1:

1. (3) After the reaction is complete, let it stand for 12-24 hours and then drain the water.

2. The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to claim 1, characterized in that, Before step (1), the following steps are also included: culturing Shewanella at 25-30°C for 12-18 hours; the culture medium for culturing Shewanella includes: 5 g / L yeast extract, 10 g / L peptone, and 10 g / L sodium chloride.

3. The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to claim 1, characterized in that, In wastewater containing adsorbable organic halogenated compounds, the concentration of adsorbable organic halogenated compounds is 1-50 mg / L, and the COD is 10-500 mg / L.

4. The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to claim 1, characterized in that, In terms of molar amount, the amount of sulfur source added is 2-4 times that of lead ions.

5. The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to claim 4, characterized in that, The sulfur source is at least one of thiosulfate, sulfite, and sulfur.

6. The method for simultaneously removing lead and adsorbable organic halogenated compounds from wastewater according to claim 1, characterized in that, The waste gas generated during the reaction is absorbed by alkaline solution.

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