Method and system for debromination of micro-current regulated nano zero-valent iron enhanced anaerobic biofilm

Abstract

The application discloses a method and system for debromination of micro-current regulated nano zero-valent iron reinforced anaerobic biofilm, and belongs to the technical field of bromine-containing organic wastewater treatment. The method sets up conductive filler and electrode assembly in the anaerobic biofilm reactor, so that the anaerobic biofilm is attached to the surface of the conductive filler; nano zero-valent iron is added to the reaction system, and a micro-current is applied between the anode and the cathode, so that the nano zero-valent iron participates in the reduction debromination of bromine-containing organic matter as an electron donor, and the reduction environment and the electron supply process are regulated by the micro-current regulation system. Under the preferred operating conditions, when treating 4-bromophenol-containing wastewater, the debromination rate can reach 0.293 mM / h, which is about 2.53 times higher than that of the single anaerobic biofilm reactor. The application can improve the anaerobic debromination efficiency of bromine-containing organic wastewater under the condition of lower additional carbon source, and is suitable for bromophenol and other bromine-containing refractory organic wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of treatment technology for refractory bromine-containing phenolic wastewater, specifically relating to a method and system for microcurrent-controlled nano-zero-valent iron-enhanced anaerobic biofilm debromination, applicable to anaerobic reduction debromination treatment of bromine-containing phenolic wastewater and other bromine-containing refractory organic wastewater. Background Technology

[0002] Bromine-containing organic pollutants are present in some industrial wastewater from chemical, pharmaceutical, flame retardant, and pesticide industries. Among them, bromophenols exhibit certain biotoxicity and are difficult to degrade, resulting in limited removal efficiency during conventional biological treatment processes. Anaerobic reduction debromination is an important pathway for the transformation of bromine-containing organic compounds, but this process typically relies on sufficient electron donors and anaerobic microorganisms with dehalogenation capabilities. When available organic carbon sources in the wastewater are insufficient, the anaerobic biological debromination process is easily limited by insufficient electron supply.

[0003] Nano-zero-valent iron possesses reducing properties and can serve as an auxiliary electron donor in anaerobic debromination processes. However, nano-zero-valent iron is prone to rapid oxidation and passivation in water treatment systems, leading to instability in the electron release process. Furthermore, direct contact between nanoparticles and microorganisms may adversely affect microbial activity. Therefore, the electron supply efficiency and long-term operational stability of nano-zero-valent iron when added alone still require improvement.

[0004] Microcurrent-assisted anaerobic biological treatment can regulate the redox environment of the reaction system and promote the formation of electroactive microorganisms and extracellular electron transfer processes. However, when microcurrent is applied alone, the reduction and debromination efficiency of bromine-containing organic compounds is still limited if the system lacks a continuous and effective electron donor.

[0005] Therefore, it is necessary to provide a wastewater treatment method and system that can simultaneously improve electron supply, reduce dependence on external carbon sources, and increase anaerobic debromination efficiency. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the debromination process of anaerobic biofilms, such as insufficient available electron donors in bromine-containing organic wastewater, unstable electron release process when nano-zero valent iron is added alone, potential adverse effects of nano-zero valent iron on the activity of anaerobic microorganisms, and low debromination efficiency of anaerobic biofilms under low carbon source conditions.

[0007] To solve the above-mentioned technical problems and achieve the purpose of this invention, the specific technical solution is as follows: A method for enhancing anaerobic biofilm debromination using microcurrent-controlled nano-zero-valent iron includes the following steps: placing conductive packing material and an electrode assembly inside an anaerobic biofilm reactor, allowing the anaerobic biofilm to adhere to the surface of the conductive packing material; introducing bromine-containing organic wastewater into the anaerobic biofilm reactor; adding nano-zero-valent iron to the anaerobic biofilm reactor; and applying a microcurrent between the anode and cathode of the electrode assembly, enabling the nano-zero-valent iron to act as an electron donor in the reduction and debromination of bromine-containing organic matter, thereby increasing the debromination rate of the anaerobic biofilm reactor.

[0008] Furthermore, the bromine-containing organic wastewater is bromine-containing phenolic wastewater.

[0009] Furthermore, the dosage of the nano-zero valent iron is 0.1~5 g / L; the particle size of the nano-zero valent iron is 10~200 nm.

[0010] Furthermore, the microcurrent is 0.1~5 mA.

[0011] Furthermore, the conductive filler includes one or more of granular activated carbon, graphite particles, biochar particles, carbon felt, and carbon brush.

[0012] Furthermore, the hydraulic retention time of the anaerobic biofilm reactor is 4 to 48 hours.

[0013] Furthermore, an external carbon source is added to the anaerobic biofilm reactor, and the external carbon source includes one or more of sodium acetate, acetate, glucose, lactate, methanol and ethanol.

[0014] An anaerobic biofilm debromination system for implementing the above method includes a reactor body, an influent unit, an effluent unit, conductive packing material, an electrode assembly, a DC power supply, and a nano-zero-valent iron dosing unit. The conductive packing material is disposed within the reactor body for attaching the anaerobic biofilm. The electrode assembly includes an anode and a cathode, which are respectively connected to the DC power supply. The nano-zero-valent iron dosing unit is used to add nano-zero-valent iron into the reactor body. The DC power supply is used to apply a microcurrent between the anode and the cathode.

[0015] Furthermore, the anode is one of a titanium-based noble metal oxide electrode, a graphite electrode, a carbon felt electrode, and a stainless steel electrode; the cathode is one of a stainless steel electrode, a graphite electrode, a carbon felt electrode, and a carbon cloth electrode; the anode and cathode are arranged in parallel, and the distance between them is 2~10 cm.

[0016] Furthermore, the conductive filler is granular activated carbon, and the surface of the granular activated carbon is loaded with an anaerobic biofilm.

[0017] An application of the above system in the treatment of bromine-containing, recalcitrant organic wastewater.

[0018] This invention involves setting conductive packing material and electrode assembly in an anaerobic biofilm reactor, allowing the anaerobic biofilm to adhere to the surface of the conductive packing material; continuously or intermittently feeding bromine-containing organic wastewater into the reactor; adding nano-zero-valent iron to the reaction system; and simultaneously applying a microcurrent between the anode and cathode of the electrode assembly, enabling the nano-zero-valent iron to participate as an electron donor in the reduction and debromination of bromine-containing organic compounds, and regulating the reduction environment and electron supply process of the system through the microcurrent. Beneficial effects

[0019] Compared with existing technologies, this invention couples nano-zero-valent iron with microcurrent for the debromination process of anaerobic biofilms. The nano-zero-valent iron provides an electron source for the reduction and debromination of bromine-containing organic matter, while the microcurrent is used to regulate the reduction environment and electron supply process of the reaction system, thereby improving the debromination rate.

[0020] This invention uses conductive fillers to load anaerobic biofilms, which facilitates the formation of stable biofilm structures and provides an attachment and transfer interface for electron transfer between microorganisms and electron donors.

[0021] This invention enables anaerobic debromination of bromine-containing organic compounds under conditions of lower external carbon source, reducing dependence on external organic carbon sources.

[0022] In one specific embodiment, when the influent 4-bromophenol concentration is 200 mg / L, the sodium acetate dosage is 30 mg / L, the hydraulic retention time is 18 h, the nano-zero valent iron dosage is 2 g / L, and the current is 1 mA, the debromination rate of the reactor reaches 0.293 mM / h, which is about 2.53 times higher than that of a standalone anaerobic biofilm reactor. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the anaerobic biofilm debromination system in one embodiment of the present invention; Figure 2 The graph shows the changes in the concentrations of 4-bromophenol and bromide ions when treating simulated wastewater containing 4-bromophenol in different reaction systems. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] See Figure 1 The reactor structure of the present invention includes: a water seal cover 1; an outlet 2; an anode mesh plate 3; a granular activated carbon and microbial layer 4; a cathode mesh plate 5; a gravel layer 6; a porous acrylic plate 7; an inlet 8; and a support leg 9.

[0026] Example 1: Construction of a microcurrent-controlled nano-zero-valent iron enhanced anaerobic biofilm debromination system This embodiment uses a cylindrical anaerobic biofilm reactor made of polyethylene plastic, with an inner diameter of 15 cm and a height of 10 cm. An inlet is located at the bottom of the reactor, and an outlet is located at the top.

[0027] The reactor contains an anode and a cathode. The anode is a 15 cm diameter circular titanium-iridium-ruthenium mesh, fixed approximately 1 cm below the effluent surface. The cathode is a 15 cm diameter stainless steel circular mesh, fixed to the bottom of the reactor. The anode and cathode are arranged parallel to each other, spaced 8 cm apart, and connected to the positive and negative terminals of a DC power supply via wires, respectively.

[0028] Activated sludge and granular activated carbon were mixed and incubated to form an anaerobic biofilm on the surface of the granular activated carbon. The biofilm-coated granular activated carbon was then filled into the reactor, with a bulk volume of 1 L and an effective water throughput volume of 1.1 L.

[0029] Example 2: Continuous flow debromination treatment of wastewater containing 4-bromophenol A continuous flow influent method was used, in which simulated wastewater containing 4-bromophenol was introduced into the reactor from the bottom via a peristaltic pump. The reactor was operated continuously for 55 days to acclimate the anaerobic biofilm and establish a stable operating state.

[0030] After the system stabilizes, adjust the dosage of the external carbon source, the dosage of nano-zero valent iron, and the hydraulic retention time. The specific operating conditions are as follows: influent 4-bromophenol concentration of 200 mg / L, sodium acetate dosage of 30 mg / L, hydraulic retention time of 18 h, nano-zero valent iron dosage of 2 g / L, and a 1 mA current applied through a DC power supply.

[0031] Under the above conditions, the debromination rate of the reactor reached 0.293 mM / h.

[0032] Comparative Example 1: Isolated Anaerobic Biofilm Reactor The reactor structure and influent conditions were the same as in Example 2, but no nano-zero-valent iron was added, and no microcurrent was applied. The debromination rate of this system was 0.083 mM / h.

[0033] Comparative Example 2: Nano-zero valent iron-enhanced anaerobic biofilm reactor Using the same reactor structure and influent conditions as in Example 2, 2 g / L of nano-zero valent iron was added, but no microcurrent was applied. The debromination rate of this system was 0.163 mM / h.

[0034] Comparative Example 3: Microcurrent-enhanced anaerobic biofilm reactor Using the same reactor structure and influent conditions as in Example 2, a 1 mA microcurrent was applied, but without the addition of nano-zero valent iron. This comparative example illustrates the effect of microcurrent alone on the debromination process of anaerobic biofilms and is compared with Example 2 to evaluate the coupling effect of microcurrent and nano-zero valent iron.

[0035] Experimental results See Figure 2 The graph shows the changes in 4-bromophenol concentration and bromide ion concentration when different reaction systems are used to treat simulated wastewater containing 4-bromophenol. In the graph, (a) shows the changes in 4-BP and (b) show the changes in bromide ion concentration. R1 is the control group, which is a simple anaerobic biofilm reactor. R2 is an anaerobic biofilm reactor with nZVI added. R3 is an anaerobic biofilm reactor with microcurrent applied. R4 is an anaerobic biofilm reactor with microcurrent and nZVI enhanced.

[0036] The results showed that in Example 2, the debromination rate of the anaerobic biofilm reactor coupled with microcurrent and nano-zero valent iron was 0.293 mM / h; in Comparative Example 2, the debromination rate of the anaerobic biofilm reactor with nano-zero valent iron added alone was 0.163 mM / h; and in Comparative Example 1, the debromination rate of the anaerobic biofilm reactor alone was 0.083 mM / h.

[0037] The results above show that the debromination rate of the reactor after coupling microcurrent with nano-zero valent iron is higher than that of the anaerobic biofilm system alone and the nano-zero valent iron enhanced system alone, indicating that this coupling method can improve the reduction and debromination efficiency of 4-bromophenol in the anaerobic biofilm system.

Claims

1. A method for enhancing anaerobic biofilm debromination using microcurrent-controlled nano-zero-valent iron, characterized in that, Includes the following steps: Conductive packing material and electrode assembly are installed inside the anaerobic biofilm reactor so that the anaerobic biofilm adheres to the surface of the conductive packing material. Bromine-containing organic wastewater is introduced into the anaerobic biofilm reactor; nano-zero-valent iron is added to the anaerobic biofilm reactor; a microcurrent is applied between the anode and cathode of the electrode assembly, so that the nano-zero-valent iron acts as an electron donor to participate in the reduction and debromination of bromine-containing organic matter, thereby increasing the debromination rate of the anaerobic biofilm reactor.

2. The method according to claim 1, characterized in that, The bromine-containing organic wastewater is bromine-containing phenolic wastewater.

3. The method according to claim 1, characterized in that, The dosage of the nano-zero valent iron is 0.1~5 g / L; the particle size of the nano-zero valent iron is 10~200 nm.

4. The method according to claim 1, characterized in that, The microcurrent is 0.1~5 mA.

5. The method according to claim 1, characterized in that, The conductive filler includes one or more of granular activated carbon, graphite particles, biochar particles, carbon felt, and carbon brush.

6. The method according to claim 1, characterized in that, The hydraulic retention time of the anaerobic biofilm reactor is 4 to 48 hours.

7. The method according to claim 1, characterized in that, An external carbon source is added to the anaerobic biofilm reactor, and the external carbon source includes one or more of sodium acetate, acetate, glucose, lactate, methanol and ethanol.

8. An anaerobic biofilm debromination system for implementing the method according to any one of claims 1 to 7, characterized in that, The reactor includes a reactor body, an inlet unit, an outlet unit, conductive packing material, an electrode assembly, a DC power supply, and a nano-zero-valent iron dosing unit. The conductive packing material is disposed within the reactor body and is used to attach an anaerobic biofilm. The electrode assembly includes an anode and a cathode, which are respectively connected to the DC power supply. The nano-zero-valent iron dosing unit is used to add nano-zero-valent iron into the reactor body. The DC power supply is used to apply a microcurrent between the anode and the cathode.

9. The system according to claim 8, characterized in that, The anode is one of a titanium-based noble metal oxide electrode, a graphite electrode, a carbon felt electrode, and a stainless steel electrode; the cathode is one of a stainless steel electrode, a graphite electrode, a carbon felt electrode, and a carbon cloth electrode; the anode and cathode are arranged in parallel, and the distance between them is 2~10 cm.

10. The system according to claim 8, characterized in that, The conductive filler is granular activated carbon, and the surface of the granular activated carbon is loaded with an anaerobic biofilm.

11. The application of the system according to any one of claims 8 to 10 in the treatment of bromine-containing recalcitrant organic wastewater.

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