NL2029145B1

NL2029145B1 - Aquatic plant-microbial electrochemical remediation system and application thereof and method for treating organic polluted water

Info

Publication number: NL2029145B1
Application number: NL2029145A
Authority: NL
Inventors: Zhou Qixing; Li Ruixiang; Li Tian; Zhang Xiaolin
Original assignee: Univ Nankai
Priority date: 2021-07-14
Filing date: 2021-09-07
Publication date: 2022-04-06
Also published as: CN113480013B; CN113480013A; NL2029145A

Abstract

The present disclosure relates to the technical ﬁeld of sewage treatment, in particular to an aquatic plant—microbial electrochemical remediation system and an application thereof, and a method for treating organic polluted water. The aquatic plant—microbial electrochemical remediation system provided by the present disclosure comprises a composite working electrode (9), a carbon felt counter electrode (4), an aquatic remediation plant (5) and a potentiostat (6); the composite working electrode (9) and the potentiostat (6) are electrically connected through a ﬁrst outer lead (71); the carbon felt counter electrode (4) and the potentiostat (6) are electrically connected through a second outer lead (72); the composite working electrode (9) comprises biochar (2). The aquatic plant—microbial electrochemical remediation system has a good treatment effect on organic polluted water. FIG.1

Description

AQUATIC PLANT-MICROBIAL ELECTROCHEMICAL REMEDIATION SYSTEM AND APPLICATION THEREOF AND METHOD FOR TREATING ORGANIC POLLUTED WATER TECHNICAL FIELD

[01] The present disclosure relates to the technical field of sewage treatment, in particular to an aquatic plant-microbial electrochemical remediation system and an application thereof, and a method for treating organic polluted water.

BACKGROUND ART

[02] The increasing discharge of organic pollutants into water bodies threatens the safety of water resources in the process of globalization. Organic pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phenols, pesticides and antibiotics with the characters of carcinogenicity and biotoxicity are the main pollutant components in agricultural, industrial and domestic wastewater. Especially, the persistent organic compounds (e.g. polycyclic aromatic hydrocarbons, polychlorinated biphenyls, etc.) have stable chemical structures and are reluctant to a series of repair methods. Therefore, it is urgent to explore a practical technology for efficiently removing organic pollutants from wastewater.

[03] At present, the technologies for the treatment of organic polluted wastewater can be divided into physical adsorption, chemical oxidation, and biodegradation technologies based on the principles. The physical adsorption technology utilizes the porous surface of solid adsorbents to adsorb pollutants through the physical or chemical bonds between them and purify the water body. The improvement of adsorbent performance can realize the rapid transfer of pollutants, but the toxic and harmful substances are not degraded. Chemical oxidation technology applies chemical oxidants (e.g. hydrogen peroxide, ozone, potassium permanganate, etc.) to oxidize organic pollutants into low-toxic and harmless substances or into controllable forms. Generally,

the participation of a large number of chemical reagents in the chemical oxidation technology could cause secondary pollution to the water body, and the high cost will hinder its large-scale application. Biodegradation technology generally uses the metabolic reaction of bacteria, fungi, plants or animals to absorb, transfer, and transform organic pollutants, which is considered as a green, economic and safe remediation technology.

[04] The current biodegradation technologies for water purification are mainly divided into microbial remediation and phytoremediation. Microbial remediation includes aerobic degradation technologies (such as aeration, activated sludge reactors, membrane bioreactors), anaerobic degradation technologies (flow anaerobic sludge blankets, anaerobic biofilters), and the combination of aerobic and anaerobic technologies (such as oxidation ditch). The remediation plants generally have strong viability and well-developed root systems, which remove pollutants through root absorption and metabolism. The current artificial wetland technology uses wetland as a biofilter in principle, and combines the self-purification of microorganisms, plants, and animals to remove pollutants in the water. For the treatment of high-concentration industrial wastewater, the relative lack of electron acceptors will lead to a small number and low activity of functional bacteria, and the community structure is unstable, thus failing to achieve the desired removal effect.

SUMMARY

[05] The purpose of the present disclosure is to provide an aquatic plant-microbial electrochemical remediation system and an application thereof, and a method for treating organic polluted water. The aquatic plant-microbial electrochemical remediation system has a good treatment effect on organic polluted water.

[06] In order to achieve the above purpose of the disclosure, the present disclosure provides the following technical schemes:

[07] The present disclosure provides an aquatic plant-microbial electrochemical remediation system, comprising a composite working electrode 9, a carbon felt counter electrode 4, an aquatic remediation plant 5, and a potentiostat 6; the composite working electrode 9 and the potentiostat 6 are electrically connected through a first outer lead 71; and the carbon felt counter electrode 4 and the potentiostat 6 are electrically connected through a second outer lead 72;

[08] The composite working electrode 9 includes biochar 2.

[09] Preferably, the aquatic remediation plant 5 is planted on the carbon felt counter electrode 4, and the root system of the aquatic remediation plant 5 passes through the carbon felt counter electrode 4 into the organic polluted water to be treated.

[10] Preferably, the aquatic remediation plant 5 comprises iris, reed, calamus or arundo.

[11] Preferably, the planting density of the aquatic remediation plant 5 is 2-20 plants / me.

[12] Preferably, the carbon felt counter electrode 4 is fixed and floated on the surface of the organic polluted water to be treated;

[13] The composite working electrode 9 is fixed and suspended in the organic polluted water to be treated by connecting to a nylon rope 3 of the carbon felt counter electrode

4.

[14] Preferably, the depth of the composite working electrode 9 in the organic polluted water to be treated is 20-50 cm.

[15] Preferably, the voltage adjustable range of the potentiostat 6 is 0-10 V, and the range of the recorded current signal is 0-5 mA, and the accuracy is 0.01 mA.

[16] The present disclosure also provides the application of the aquatic plant-microbial electrochemical remediation system described in the above technical scheme in the treatment of organic polluted water.

[17] The present disclosure also provides a method for treating organic polluted water, comprising the following steps:

[18] Placing the aquatic plant-microbial electrochemical remediation system described in the above technical scheme in the organic polluted water to be treated, and applying a voltage through a potentiostat 6 to perform the plant-microbial electrochemical remediation.

[19] The present disclosure provides an aquatic plant-microbial electrochemical remediation system, comprising a composite working electrode 9, a carbon felt counter electrode 4, an aquatic remediation plant 5, and a potentiostat 6; the composite working electrode 9 and the potentiostat 6 are electrically connected through a first outer lead 71; the carbon felt counter electrode 4 and the potentiostat 6 are electrically connected through a second outer lead 72; and the composite working electrode 9 includes biochar

2. The aquatic plant-microbial electrochemical remediation system of the present disclosure can stably produce electricity through the stimulation of external power supply, realize the enrichment of functional flora, and promote the continuous consumption of organic pollutants relying on external electrodes (i.e. composite working electrodes); the introduction of aquatic remediation plants can provide nutrients (carbon source or nitrogen source, etc.) for the rhizosphere functional microorganisms (degrading bacteria, electrogenic bacteria, etc.) using the secreted rhizosphere metabolites, on the one hand, they can absorb small molecule pollutants to promote the removal of pollutants by their root systems. At the same time, the biochar in the composite working electrode and the stainless steel mesh for fixing the biochar can further improve the physical adsorption performance of the composite working electrode, and can strengthen the consumption of pollutants. That is, the present disclosure integrates the effects of plant-microbial degradation, electrochemical stimulation and physical adsorption, further strengthens the treatment of organic polluted water, and has excellent remediation performance.

[20] In addition, the remediation system does not require additional carbon sources during operation, is environmentally friendly, has controllable costs, and has ecological landscape functions.

[21] The present disclosure also provides a method for treating organic polluted water, comprising the following steps: placing the aquatic plant-microbial electrochemical remediation system described in the above technical scheme in the organic polluted water to be treated, and applying a voltage through a potentiostat 6 to perform the plant-microbial electrochemical remediation. The method achieves a stable and efficient remediation performance. The constructed repair system has the advantages of simple operation, low cost and little environmental disturbance. Moreover, it has the potential of large-scale treatment of high-concentration industrial wastewater.

BRIEF DESCRIPTION OF THE DRAWINGS

[22] FIG 1 is a schematic diagram of the aquatic plant-microbial electrochemical 5 remediation system of the present disclosure; among them, l-stainless steel mesh, 2-biochar, 3-nylon rope, 4-carbon felt counter electrode, S-aquatic remediation plant, 6-potentiostat, 71-the first outer lead, 72-the second outer lead, 8-current signal collection and processing system, 9-composite working electrode;

[23] FIG 2 shows the average current change curve of the remediation system constructed in Example 1 and Comparative Example 2 during 30 days of remediation;

[24] FIG. 3 shows the change curves of absorbance at 329 nm of the remediation system constructed in Example 1 and Comparative Example 2 on the 0th, 10th, 20th and 30th day;

[25] FIG. 4 shows the change curves of TOC content of the remediation system constructed in Example 1 and Comparative Example 2 on the Oth, 10th, 20th and 30th days.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[26] The present disclosure provides an aquatic plant-microbial electrochemical remediation system, comprising a composite working electrode 9, a carbon felt counter electrode 4, an aquatic remediation plant 5, and a potentiostat 6; the composite working electrode 9 and the potentiostat 6 are electrically connected through a first outer lead 71; the carbon felt counter electrode 4 and the potentiostat 6 are electrically connected through a second outer lead 72;

[27] The composite working electrode 9 includes biochar 2.

[28] As a specific embodiment of the present disclosure, the composite working electrode 9 further includes a stainless steel mesh 1 for fixing the biochar 2.

[29] In the present disclosure, the particle size of the biochar 2 is preferably 0.5-5 mm, and more preferably 2 mm; the specific surface area of the biochar 2 is preferably 500-1500 m?/ g, and more preferably 1200 m?/ g. In the present disclosure, the type of biochar 2 is preferably coconut shell biochar, corn stalk biochar, rice husk biochar or bamboo charcoal, and more preferably coconut shell biochar. The present disclosure does not have any special restrictions on the source of the biochar 2, a source well known to those skilled in the art can be used.

[30] In the present disclosure, the mesh diameter of the stainless steel mesh 1 is preferably 1-10 mm, and more preferably 2 mm; the pore diameter of the stainless steel mesh is preferably 0.1-5 mm, and more preferably 1 mm.

[31] As a specific embodiment of the present disclosure, the particle size of the biochar 2 is larger than the pore size of the stainless steel mesh 1.

[32] As a specific embodiment of the present disclosure, the method of fixing biochar 2 by the stainless steel mesh 1 is wrapping.

[33] In the present disclosure, the aquatic remediation plant 5 preferably includes iris, reed, calamus or arundo, more preferably includes iris, and specifically blue iris.

[34] In the present disclosure, the aquatic remediation plant 5 has a relatively developed root system and a relatively high pollutant tolerance.

[35] As a specific embodiment of the present disclosure, the aquatic remediation plant 5 is planted on the carbon felt counter electrode 4, and the root system of the aquatic remediation plant 5 passes through the carbon felt counter electrode 4 into the organic polluted water to be treated.

[36] In the present disclosure, the planting density of the aquatic remediation plants 5 is preferably 2-20 plants / m?, more preferably 5-15 plants / m?, and most preferably 9 plants / m?.

[37] As a specific embodiment of the present disclosure, the composite working electrode 9 is suspended in the organic polluted water to be treated through a nylon rope 3, In the present disclosure, the diameter of the nylon rope 3 is preferably 0.5-20 mm, and more preferably 10 mm. In the present disclosure, the depth of the composite working electrode 9 in the organic polluted water to be treated is preferably 20-50 cm, more preferably 25-35 cm, and most preferably 30 cm. In the present disclosure, setting the composite working electrode 9 within the above depth range can ensure that the nutrients secreted by the plant roots can be utilized by the microorganisms attached to the composite working electrode 9.

[38] As a specific embodiment of the present disclosure, the carbon felt counter electrode 4 is fixed and floated on the surface of the organic polluted water to be treated. In the present disclosure, the thickness of the carbon felt counter electrode 4 is preferably 10-50 mm, and more preferably 30 mm.

[39] As a specific embodiment of the present disclosure, the voltage adjustable range of the potentiostat 6 is 0-10 V, the range of the recorded current signal is 0-5 mA, and the accuracy is 0.01 mA.

[40] As a specific embodiment of the present disclosure, the aquatic plant-microbial electrochemical remediation system further includes a current signal collection and processing system 8; the potentiostat 6 and the current signal collection and processing system 8 are electrically connected.

[41] The present disclosure uses the current signals recorded by the current signal collection and processing system 8 to reflect the removal process of pollutants, and its configuration also has the potential for actual site remediation.

[42] In the present disclosure, the preparation process of the aquatic plant-microbial electrochemical remediation system preferably includes the following steps:

[43] Wrapping the biochar 2 by the stainless steel mesh 1 and sealing to obtain a composite working electrode 9;

[44] Connecting one end of the nylon rope 3 to the carbon felt counter electrode 4, and connecting the other end to the composite working electrode 9 to make the carbon felt fixed and floated on the surface of the water, and the composite working electrode 9 is fixed and suspended in the organic polluted water to be treated;

[45] Fixing the carbon felt counter electrode 4 and making it floated on the surface of the organic polluted water to be treated;

[46] Planting the aquatic remediation plant 5 on the carbon felt counter electrode 4 to make its root system into the water;

[47] Connecting the composite working electrode 9 and the carbon felt counter electrode 4 to the anode and the cathode of the potentiostat 6 respectively by the first outer lead 71 and the second outer lead 72 to obtain the aquatic plant-microbial electrochemical remediation system.

[48] In the present disclosure, after the composite working electrode 9 and the carbon felt counter electrode 4 are respectively connected to the anode and the cathode of the potentiostat 6, it also preferably includes the electrical connection of the potentiostat to the current signal collection and processing system &.

[49] In the present disclosure, the sealing is preferably sealing tightly with an iron wire.

[50] The present disclosure also provides the application of the aquatic plant-microbial electrochemical remediation system described in the above technical scheme in the treatment of organic polluted water.

[S1] The present disclosure also provides a method for treating organic polluted water, comprising the following steps:

[52] Placing the aquatic plant-microbial electrochemical remediation system described in the above technical scheme in the organic polluted water to be treated, and applying a voltage through a potentiostat 6 to perform the plant-microbial electrochemical remediation.

[53] In the present disclosure, the voltage applied by the potentiostat 6 is preferably

0.5-1.5 V, and more preferably 0.7 V.

[54] In the present disclosure, the remediation is preferably carried out under the conditions of the room temperature of 25°C, the humidity of 50 % RH, the light time of 12 h per day and a ventilated atmosphere.

[SS] In the present disclosure, the total concentration of pollutants in the organic polluted water to be treated is preferably 500-2000 mg / L.

[56] In the present disclosure, during the process of aquatic plant-microbial electrochemical remediation, the current signal collection and processing system 8 is used to monitor the degradation of the polluted substrate in the organic polluted water to be treated. The electrode system can act as a biosensor, and the current signals generated can detect the degradation process of pollutants.

[S57] The present disclosure addresses the problem of low remediation efficiency caused by relatively lack of electron receptors in the current plant-microbial treatment of high-concentration industrial wastewater, and introduces the microbial electrochemical technology and proposes the construction of a new type of aquatic plant-microbial electrochemical remediation system with zero-carbon source addition and the method of treating organic polluted water, the present disclosure has the following advantages: the remediation efficiency is high and the operation is stable, the present disclosure integrates plant-microbial degradation, electrochemical stimulation, and physical adsorption to strengthen the treatment of organic polluted water, and achieves a good treatment effect; by applying external power stimulation and stabilizing the enrichment of electrogenic bacteria to ensure the stability of operating conditions. While consuming and removing organic pollutants, it can also simultaneously remove pollutants such as nitrogen and phosphorus that pollute the water, which can avoid the eutrophication of the water. It is green and environmentally friendly, and has landscape ecological functions. The methods and materials used in the present disclosure have little environmental disturbance and basically no secondary harm; the introduced aquatic remediation plants have certain ornamental and ecological functions; the cost is controllable and it can be applied on a large scale. The present disclosure does not require an external carbon source, and uses plant rhizosphere exudates to ensure the activity of functional bacteria; the applied weak external voltage has low energy consumption and can be operated for a long time; the electrode material used is low in cost; the system construction method is simple and easy to implement, with potential for large-scale treatment of industrial wastewater; it has the function of biosensor. The present disclosure utilizes the composite working electrode 9 to degrade and consume organic pollutants and simultaneously generate current signals, and through the data acquisition and processing system, the degradation of pollutants can be monitored in real time.

[58] The aquatic plant-microbial electrochemical remediation system provided by the present disclosure, the application thereof, and the method for treating organic polluted water provided by the present disclosure will be described in detail in conjunction with examples in the following, but they should not be understood as limiting the protection scope of the present disclosure.

[59] Example 1

[60] The main body of the remediation system is: a cuboid acrylic box with a length of 100 cm, a width of 100 cm, and a height of 60 cm, and the thickness of the acrylic box is I cm;

[61] According to the structure shown in FIG. 1:

[62] 500 L of petroleum hydrocarbon polluted wastewater (taken from the drilling well of Shandong Shengli Oilfield) was poured into the box with a liquid level of 50 cm;

[63] 500 g of coconut shell biochar (a particle size of 2 mm) was wrapped by a stainless steel mesh with a length of 30 cm and a width of 30 cm (the mesh diameter of 2 mm, and the pore size of 1 mm), and sealed tightly with iron wire to obtain a composite working electrode;

[64] A carbon felt with a length of 15 cm, a width of 15 cm and a thickness of 30 mm was fixed and floated on the surface of the water; one end of a nylon rope 3 with a diameter of 10 mm was connected to the carbon felt counter electrode 4, and the other end was connected to the composite working electrode and suspended at a depth of 30 cm from the surface of the water;

[65] The seedlings of blue iris with well-growing and well-developed roots were planted on the surface of the carbon felt counter electrode 3 to make the roots into the water. The composite working electrode and the carbon felt counter electrode 4 were respectively connected to the anode and the cathode of the potentiostat 6 by the first outer lead 71 and the second outer lead 72, and the potentiostat was electrically connected to the current signal collection and processing system 8 to obtain the aquatic plant-microbial electrochemical remediation system, wherein 9 groups of the aquatic plant-microbial electrochemical remediation system were placed evenly in each cuboid box, denoted as PMEC.

[66] Comparative Example 1

[67] The petroleum hydrocarbon contaminated wastewater from the same source as in Example 1 was used as the control group OS.

[68] Comparative Example 2

[69] With reference to Example 1, the only difference was that water that was not contaminated by petroleum hydrocarbons was poured into the box, the height of the liquid level was 50 cm, which was denoted as the control group CK.

[70] Test Example

[71] The voltage of the potentiostat 6 was adjusted to 0.7 V under the conditions of a room temperature of 25°C, a humidity of 50 % RH, a light time of 12 h per day and a ventilated atmosphere, the aquatic plant-microbial electrochemical remediation system was turned on for remediation for 30 days, and the degradation of the contaminated substrate was monitored by using the current signal collection and processing system 8;

[72] In the above remediation process, water samples were taken every 10 days for the determination of TOC (all organic matter dissolved in water, mainly including petroleum hydrocarbon components and a small amount of rhizosphere exudates) content and the absorbance at 329nm. The TOC content was determined by a TOC instrument for quantitative determination; the absorbance at 329nm was measured by an ultraviolet spectrophotometer; the current signal was collected by the potentiostat 6, and the signal change was detected by the current signal collection and processing system 8;

[73] FIG. 2 shows the average current change curve of the remediation system constructed in Example 1 (PMEC group) and Comparative Example 2 (CK group) during 30 days of remediation. It can be seen from FIG. 2 that the average current of the CK group shows a slow increase until it stabilizes, the current range is 0.11-0.27 mA; the current of PMEC group is significantly higher than that of CK group as a whole, the current increases rapidly in the early stage (reaching 0.61 + 0.08 mA on the 12th day), and then slowly decreases, after the 26th day, it decreases to a level equivalent to that of the CK group. The water in the CK group does not contain petroleum hydrocarbon pollutants, and the current is mainly produced by the metabolism of rhizosphere exudates; the initial increase in current indicates the enrichment of electrogenic bacteria, and the subsequent stabilization of the current indicates that rhizosphere exudates can be continuously produced to provide nutrients for microorganisms. The high current in the PMEC group is mainly due to the metabolism of petroleum hydrocarbons; with the consumption of pollutants, the current gradually decreases. These results show that the constructed aquatic plant-microbial electrochemical remediation system with zero-carbon source addition can degrade petroleum substances in water and reflect the process through current signals;

[74] FIG 3 shows the change curve of the absorbance at 329 nm of the remediation system constructed in Example 1 and Comparative Example 2 on the 0th, 10th, 20th and 30th day; it can be seen from FIG. 3 that the initial absorbance of the CK group is 0.156 + 0.012, and the initial absorbance of the PMEC group (i.e. OS) is 0.852 + 0.063, indicating that the absorbance at 329 nm can reflect the content of petroleum hydrocarbons in the water. On the 10th day, the absorbance at 329nm of PMEC group is decreased by 38% relative to that of the OS group (0.526 + 0.041), accounting for 65 % of the total decrease, which indicates that the removal of petroleum hydrocarbons in water mainly occurred in the early stage;

[75] FIG. 4 shows the change curve of TOC content of the remediation system constructed in Example 1 and Comparative Example 2 on the Oth, 10th, 20th, and 30th days; it can be seen from FIG. 4 that the initial TOC content in the CK group is 152 + 22 mg / L, and shows a downward trend over time. Due to the presence of petroleum hydrocarbon pollutants, the initial (i.e. OS) TOC content of the PMEC group reaches 1232 + 121 mg / L; and the removal is mainly concentrated in the first 10 days (removal rate reaches 39%), and the total removal rate of 30 days is 74 % (relative to OS). These results indicate that the typical aquatic plant-microbial electrochemical remediation system with zero-carbon source addition constructed by the present disclosure has good remediation performance for high-concentration organic polluted wastewater.

[76] The above are only the preferred embodiments of the present disclosure. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present disclosure, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present disclosure.

Claims

-13- Conclusions:

An electrochemical microbial water purification system with aquatic plants, comprising a composite working electrode (9), a carbon felt counter electrode (4), a water purification plant (5) and a potentiostat (6); wherein the composite working electrode (9) and the potentiostat (6) are electrically connected through a first connection {71}; wherein the carbon felt counter electrode {4} and the potentiostat {6) are electrically connected through a second connection (72); and wherein the composite working electrode {9} comprises biochar {2}.

The electrochemical microbial water purification system with aquatic plants according to claim 1, wherein the water purification plant {5} is planted on the carbon felt counter electrode {4) and the root system of the water purification plant {5} through the carbon felt counter electrode (4) in the organically polluted water to be treated urges.

The electrochemical microbial water purification system with aquatic plants according to claim 2, wherein the water purification plant (5) comprises iris, reed, calamus or ornamental grass.

The electrochemical microbial water purification system with aquatic plants according to one or more of claims to 3, wherein the planting density of the water purification plant (5) is 2 to 20 plants per square meter.

The electrochemical microbial water purification system with aquatic plants according to claim 1, wherein the carbon felt counter electrode {4} is fixed floating on the surface of the organic contaminated water to be treated; and the composite working electrode {9} is fixed in the organically polluted water to be treated and suspended by a nylon rope connection (3) of the carbon felt counter electrode (4).

The electrochemical microbial water purification system with aquatic plants according to claim 5, wherein the composite working electrode (9) lies at a depth of 20 to 50 cm in the organically polluted water to be treated.

The electrochemical microbial water purification system with aquatic plants according to claim 1, wherein the adjustable voltage range of the potentiostat (6) is from 0 to 10 V, and

-14- is the range of the recorded current signal from 0 to 5 mA, with an accuracy of 0.01 mA.

Use of the electrochemical microbial water purification system with aquatic plants according to one or more of claims 1 to 7 in the treatment of organically polluted water.

A method for treating organically polluted water, comprising the following steps: - placing the electrochemical microbial water purification system with aquatic plants according to one or more of claims 1 to 7 in the organically polluted water to be treated, and - installing of a voltage by means of a potentiostat (6) to carry out the microbial electrochemical purification on plants.