Apparatus and method for treating groundwater contaminants using bioelectrochemical process

Abstract

The application provides a device and method for treating groundwater pollutants by a bioelectrochemical method, the device comprises two groups of electrode pairs, and the two groups of electrode pairs are vertically installed on the side wall of the device; each group of electrode pairs comprises a titanium carbide electrode, a cast iron electrode and a plastic electrode. The current density can be effectively reduced by the arrangement of the electrodes, and the reaction efficiency is improved; active oxygen free radicals can be effectively generated on the surface of the plastic electrode, so that the small molecule and mineralization of the organic pollutants are realized; in addition, the addition of microorganisms can effectively improve the degradation efficiency of the pollutants; the fluorite gypsum filler can create an alkaline environment to promote the settlement and flocculation of the pollutants, and the released fluorine ions can stimulate the hydration reaction in the steel slag filler layer to realize the solidification and stabilization of the pollutants; the decontamination device of the application adopts a composite system of electrochemistry and microorganisms, the treatment efficiency of the contaminated groundwater is greatly improved by extraction and soil infiltration, the treatment cost is low, and the application prospect of the application in the field of contaminated groundwater remediation is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of groundwater pollution treatment, in particular to a device and method for treating groundwater pollutants by bio-electrochemical method. BACKGROUND

[0002] Water pollution is caused by harmful chemicals, which reduces or eliminates the use value of water. The acid, base, oxidizing agent, and compounds such as copper, cadmium, mercury, and arsenic in wastewater, organic poisons such as benzene and dichloroethane, and ethylene glycol can kill aquatic organisms and affect drinking water sources and scenic landscapes. When organic matter in wastewater is decomposed by microorganisms, oxygen in water is consumed, affecting the life of aquatic organisms. After the dissolved oxygen in water is depleted, organic matter is anaerobically decomposed to produce hydrogen sulfide, mercaptans, and other unpleasant gases, further deteriorating water quality.

[0003] Water pollution is mainly caused by pollutants generated by human activities, and the sources of pollutants mainly include four parts: mine pollution sources, industrial pollution sources, agricultural pollution sources, and domestic pollution sources.

[0004] There is an urgent need for treatment of high-salinity heavy metal and organic wastewater.

[0005] Electrochemical technology is commonly used to repair contaminated wastewater. However, the repair efficiency needs to be improved. SUMMARY

[0006] Based on the above technical background, the present application provides a device for treating groundwater pollutants by bio-electrochemical method, which includes two groups of electrodes, and each group of electrodes is vertically installed on the side wall of the device. Each group of electrodes includes a titanium carbide electrode, a cast iron electrode, and a plastic electrode. The electrode pair formed by the above electrodes can effectively reduce the current density and improve the reaction efficiency, and can effectively generate active oxygen free radicals to achieve the small molecule and mineralization of organic pollutants. The fluorite gypsum filler used can create an alkaline environment to promote the settlement and flocculation of pollutants, and the released fluoride ions can stimulate the hydration reaction in the steel slag filler layer to achieve the solidification and stabilization of pollutants. In addition, the addition of microorganisms in the iron-rich biochar filler layer can effectively improve the degradation efficiency of pollutants. The device has the advantages of high pollutant removal efficiency, stable treatment effect, small land occupation, and low energy consumption, effectively reduces the treatment cost of groundwater pollutants, and can be widely applied to the repair of contaminated groundwater, thereby completing the present application.

[0007] The first aspect of the present application provides a device for treating groundwater pollutants by bio-electrochemical method, which includes two groups of electrodes, and each group of electrodes is vertically installed on the inner side wall of the device. Each pair of electrodes includes a titanium carbide electrode, a cast iron electrode, and a plastic electrode.

[0008] The second aspect of the present application provides a method for treating groundwater pollutants, preferably using the device of the first aspect of the present application, the method comprising using a centrifugal pump to extract groundwater to be treated from an extraction well into the device for treating groundwater pollutants by bio-electrochemical method. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 Fig. 1 shows a schematic diagram of a device for treating groundwater pollutants by bio-electrochemical method according to a preferred embodiment of the present application.

[0010] REFERENCE SIGNS

[0011] 1 - Titanium carbide electrode;

[0012] 2 - Cast iron electrode;

[0013] 3 - Plastic electrode;

[0014] 4 - Planting layer;

[0015] 5 - Filler layer. DETAILED DESCRIPTION

[0016] The present application will be described in detail below, and the features and advantages of the present application will become more apparent with these descriptions.

[0017] The first aspect of the present application provides a device for treating groundwater pollutants by bio-electrochemical method, the device comprising two groups of electrodes, both of which are vertically installed on the inner side wall of the device, and each pair of electrodes comprises a titanium carbide electrode, a cast iron electrode and a plastic electrode.

[0018] According to the present application, the active substances generated by the electrodes can reduce heavy metals in the wastewater to be treated and oxidize organic pollutants in the wastewater.

[0019] The device is connected to an extraction well, and a centrifugal pump is arranged between the device and the extraction well, as shown in Fig. 1. Figure 1 The centrifugal pump is used to extract groundwater to be treated from the extraction well into the device for treating groundwater pollutants by bio-electrochemical method.

[0020] According to a preferred embodiment of the present application, the first electrode pair comprises a titanium carbide electrode 1, a cast iron electrode 2 and a plastic electrode 3.

[0021] The second group of electrodes comprises a titanium carbide electrode 1, a cast iron electrode 2 and a plastic electrode 3.

[0022] The first group of electrode pairs and the second group of electrodes are installed in the device in order from top to bottom, as shown in Fig. 1. Figure 1

[0023] ​According to a further preferred embodiment of the present application, in the first group of electrodes, the cast iron electrode 2 is installed below the titanium carbide electrode 1, and the plastic electrode 3 is installed below the cast iron electrode 2; in the second group of electrodes, the cast iron electrode 2 is installed below the titanium carbide electrode 1, and the plastic electrode 3 is installed below the cast iron electrode 2.

[0024] According to a further preferred embodiment of the present application, the titanium carbide electrode 1 in the first group of electrodes, the plastic electrode 3, and the cast iron electrode 2 in the second group of electrodes are all installed on the left side wall of the device, and are spaced apart from the right side wall; the rest of the electrodes are all installed on the right side wall of the device, and are spaced apart from the left side wall. In this way, the hydraulic retention time is improved, and the water flow sequentially passes through the three electrodes, and reduction and oxidation of the pollutants are sequentially achieved on the titanium carbide electrode, the cast iron electrode, and the plastic electrode.

[0025] Preferably, the distance between the electrodes on the left side wall of the device and the right side wall is 4-8 cm, preferably 5 cm.

[0026] The distance between the electrodes on the right side wall of the device and the left side wall is 4-8 cm, preferably 5 cm.

[0027] In the device of the present application, the distance between adjacent electrodes is the same, and the distance between adjacent electrodes is 10-15 cm, preferably 10 cm.

[0028] According to the present application, a voltage is applied to the two groups of electrodes, and the voltage applied to each group of electrodes gradually increases from top to bottom. The voltage applied to the first group of electrodes is the smallest, and the voltage applied to the second group of electrodes is the largest.

[0029] It has been found through experiments that the design of sequentially increasing voltage can effectively improve the current density and application efficiency, and ensure the removal effect of pollutants in the sewage to be treated which changes with the increase of depth.

[0030] Preferably, the voltage applied to the first group of electrodes is 0.5-5 V, and the voltage applied to the second group of electrodes is 1-6 V.

[0031] More preferably, the voltage applied to the first group of electrodes is 2 V, and the voltage applied to the second group of electrodes is 3 V.

[0032] In the present application, when the pollutants are mainly heavy metals, halogenated or nitro organic pollutants, the strong reduction effect is generated by the cathode of the titanium carbide electrode, the Fe 2+ is released by the anode of the cast iron electrode, a weak reduction environment is generated, and the strong oxidation effect is generated by the anode of the plastic electrode.

[0033] The pore size of the titanium carbide electrode is 50-500 nm, preferably 200 nm; and the distance between adjacent pores is 50-500 μm, preferably 200 nm.

[0034] In the present application, a planting layer 4 is arranged above the first group of electrodes, and aquatic plants are planted, and pollutants such as heavy metals, organic pollutants, etc. in the wastewater to be treated are absorbed by the aquatic plants in the planting layer 4, so as to strengthen the removal of the pollutants in the wastewater to be treated.

[0035] The distance between the planting layer 4 and the titanium carbide electrode 1 in the first group of electrodes is 10-15 cm, preferably 15 cm.

[0036] In a preferred embodiment of the present application, a filler layer 5 is arranged directly below each electrode, and the length of the filler layer 5 is preferably the same as the length of the electrode.

[0037] The distance between the filler layer 5 and its adjacent electrode is equal, and the distance is 5-7.5 cm, preferably 5 cm.

[0038] The filler layer 5 comprises one or more of manganese sand, iron-rich biochar, steel slag, limestone, fly ash, volcanic stone, fluorogypsum, and gravel, wherein the steel slag, iron-rich biochar, and fluorogypsum are preferred.

[0039] Preferably, the filler layer 5 below the titanium carbide electrode 1, cast iron electrode 2, and plastic electrode 3 is steel slag, iron-rich biochar, and fluorogypsum, respectively.

[0040] The fluorogypsum filler layer is preferably three layers, comprising an upper fluorogypsum filler layer, a middle fluorogypsum filler layer, and a bottom fluorogypsum filler layer arranged from top to bottom.

[0041] More preferably, the particle size of the upper fluorogypsum filler layer is larger than that of the middle fluorogypsum filler layer, and the particle size of the bottom fluorogypsum filler layer is larger than that of the middle fluorogypsum filler layer.

[0042] Further preferably, the particle size of the upper fluorogypsum filler layer is 15-30 mm, the particle size of the middle fluorogypsum filler layer is 8-15 mm, and the particle size of the bottom fluorogypsum filler layer is 15-30 mm. This reduces the water flow pressure and increases the biological load and growth space.

[0043] In a further preferred embodiment of the present application, microorganisms are loaded in the iron-rich biochar filler layer. The addition of microorganisms can effectively improve the degradation of pollutants, and at the same time, the loaded microorganisms have a synergistic effect with the active substances produced by the aquatic plants and electrodes, further improving the treatment effect and efficiency of the contaminated groundwater.

[0044] As the iron-rich biochar, it is a biochar obtained by anaerobic pyrolysis of plants planted in iron-containing soil, wherein the zero-valent iron loading is the highest, and is loaded in the bulk phase, which can be used for a long time. For the iron-rich biochar, the iron-rich biochar disclosed in the prior art can be used without particular limitation.

[0045] The microorganism is selected from one or more of Desulfovibrio desulfuicans, Geobacter sulfurreducen, Shewanella oneidensis MR-1, Geobacter metallireducens, Geobacter sulfurreducens, nitrifying bacteria, denitrifying bacteria and phosphorus bacteria, and is preferably Geobacter sulfurreducen, Geobacter metallireducens and nitrifying bacteria.

[0046] In a further preferred embodiment of the present application, an impermeable layer is laid under the filler layer to delay the residence time of the wastewater to be treated in the device, so that the wastewater to be treated can be ensured to have sufficient electrochemical remediation and bioremediation.

[0047] The second aspect of the present application provides a method for treating groundwater pollutants, preferably using the device of the first aspect of the present application to treat groundwater pollutants, the method comprising using a centrifugal pump to extract the groundwater to be treated from the extraction well into the device for biologically electrochemically treating groundwater pollutants.

[0048] The groundwater to be treated passes through the planting layer 4, the electrode layer and the filler layer 5 in the device in sequence.

[0049] The flow rate of the groundwater to be treated in the device is 5-15 L / min, and the flow rate is preferably 10 L / min.

[0050] The flow-through time of the groundwater to be treated in the device is 3-10 min, and the flow-through time is preferably 5 min.

[0051] The use of the device of the present application for removing groundwater pollutants can effectively improve the removal efficiency and achieve good removal effect in a short time.

[0052] The voltage applied to the first group of electrodes is 0.5-5 V, and the voltage is preferably 2 V.

[0053] The voltage applied to the second group of electrodes is 1-6 V, and the voltage is preferably 3 V.

[0054] The present application uses two groups of electrodes arranged from top to bottom in sequence, and the voltage of the lower electrodes is higher than that of the upper electrodes, which uses a stepwise distribution design to effectively improve the current density and application efficiency and ensure the removal effect of pollutants that change with depth.

[0055] The present application has the following beneficial effects:

[0056] (1) The decontamination device of the present application adopts a composite system of electrochemistry and microorganisms, and greatly improves the treatment efficiency of contaminated groundwater through extraction and soil infiltration;

[0057] (2) The present application can effectively produce a reducing environment by using titanium carbide electrodes and cast iron electrodes to realize the reduction of heavy metals, and the use of iron-rich biochar filler can produce a micro-electrolysis effect to promote the reduction of heavy metals; plastic electrodes can effectively generate active oxygen free radicals to realize the small molecule and mineralization of organic pollutants; in addition, the addition of microorganisms can effectively improve the degradation efficiency of pollutants; the use of fluorite gypsum filler can create an alkaline environment to promote the settlement and flocculation of pollutants; and the released fluoride ions can stimulate the hydration reaction in the steel slag filler layer to realize the solidification and stabilization of pollutants;

[0058] (3) The two groups of electrodes of the device are composed of titanium carbide electrodes, cast iron electrodes and plastic electrodes, and are designed in a multi-level step distribution from top to bottom, and the voltage of the lower electrodes is higher than that of the upper electrodes, effectively improving the current density and application efficiency, and ensuring the removal effect of pollutants changing with depth;

[0059] (4) The treatment device adopted by the present application has the advantages of high pollutant removal efficiency, stable treatment effect, small occupied area, low energy consumption, effectively reduces the cost of purifying groundwater, and can be widely applied to the remediation of contaminated groundwater.

[0060] Embodiment

[0061] The present application will be further described below through specific examples, which are limited to illustrate the present application, and are not used to limit the scope of the present application.

[0062] Example 1

[0063] The device for treating groundwater pollutants by the biological electrochemical method is connected with an extraction well, a centrifugal pump is arranged between the device and the extraction well, the device comprises two groups of three-electrode systems, including a titanium carbide electrode 1, a cast iron electrode 2 and a plastic electrode 3, which are stacked from top to bottom. Each electrode system is vertically installed on the side wall of the device from top to bottom, in the first group of electrode systems, the cast iron electrode 2 is installed below the titanium carbide electrode 1, and the plastic electrode 3 is installed below the cast iron electrode 2. The titanium carbide electrode 1 in the first group of electrode systems, the plastic electrode 3 and the cast iron electrode 2 in the second group of electrode systems are installed on the left side wall of the device, and the distance between the left side wall and the right side wall is 5 cm; the cast iron electrode 2 in the first group of electrode systems, the titanium carbide electrode 1 in the second group of electrode systems and the plastic electrode 3 are all installed on the right side wall of the device, and the distance between the right side wall and the left side wall is 5 cm; a planting layer 4 is arranged at the top, and the distance between the planting layer 4 and the titanium carbide electrode 1 in the first electrode pair is 15 cm. A filler layer 5 is arranged below each electrode, the length of the filler layer 5 is equal to the length of the electrode, and the distance between the filler layer 5 and the adjacent electrode is 5 cm; the filler layers 5 below the titanium carbide electrode 1, the cast iron electrode 2 and the plastic electrode 3 are respectively iron-rich biochar, steel slag and fluorogypsum filler layers, wherein the fluorogypsum comprises an upper fluorogypsum filler layer, a middle fluorogypsum filler layer and a bottom fluorogypsum filler layer arranged from top to bottom, the particle size of the upper fluorogypsum filler layer is 8-15 mm, the particle size of the middle fluorogypsum filler layer is 8-15 mm, and the particle size of the bottom fluorogypsum filler layer is 20-35 mm; Geobacter sulfurreducen is loaded in the iron-rich biochar filler layer, and a impermeable layer is arranged below the bottom fluorogypsum filler layer.

[0064] A voltage is applied to each group of electrodes, the voltage applied to the first group of electrodes is 2 V, and the voltage applied to the second group of electrodes is 3 V.

[0065] The centrifugal pump is used to extract the groundwater to be treated from the extraction well to the device for treating groundwater pollutants by the biological electrochemical method, the flow rate of the groundwater to be treated in the device is 10 L / min, and the flow time of the groundwater to be treated in the device is 5 min.

[0066] After detection, the content of heavy metals is 0.13 mg / L, and the content of organic pollutants is 28 mg / L before treatment, after treatment by the device, the content of heavy metals in the groundwater is 0.02 mg / L, and the content of organic pollutants is 0.56 mg / L, and the main components of the organic pollutants are 1,3-dinitrobenzene, 1,4-dichlorobenzene, benzene, o-(p) nitrochlorobenzene and chlorobenzene.

[0067] The repair system can be used for pollution groundwater treatment, groundwater resource protection, gas station, chemical plant and the like, mine groundwater repair, underground reservoir, underground storage facility, urban groundwater resource repair, contaminated site repair, ecological sensitive area, water conservancy project periphery, groundwater monitoring point and the like.

[0068] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "back" and the like indicate the orientation or positional relationship in the working state of the present application, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0069] The above describes the present application in combination with the preferred embodiments, but these embodiments are only exemplary and serve only to illustrate. On this basis, various substitutions and improvements can be made to the present application, which all fall within the scope of protection of the present application.

Claims

1. An apparatus for the treatment of groundwater contaminants by bioelectrochemical processes, characterized in that, The device comprises two groups of electrodes, both of which are vertically installed on the inner side wall of the device, each group of electrodes comprising a titanium carbide electrode (1), a cast iron electrode (2) and a plastic electrode (3); A filler layer (5) is arranged directly below each electrode, and the filler layer (5) is one or more of steel slag, iron-rich biochar and fluorite gypsum; A planting layer (4) is arranged above the first electrode pair, and aquatic plants are planted in the planting layer (4); In each group of electrodes, the cast iron electrode (2) is installed below the titanium carbide electrode (1), and the plastic electrode (3) is installed below the cast iron electrode (2); The titanium carbide electrode (1) and the plastic electrode (3) in the first group of electrodes and the cast iron electrode (2) in the second group of electrodes are all installed on the left side wall of the device, and there is a certain distance between them and the right side wall, and the rest of the electrodes are all installed on the right side wall of the device, and there is a certain distance between them and the left side wall.

2. The device for treating groundwater pollutants by bio-electrochemical method according to claim 1, wherein, Each group of electrodes comprises a titanium carbide electrode (1), a cast iron electrode (2) and a plastic electrode (3); The two groups of electrodes are installed in the device from top to bottom.

3. The device for treating groundwater pollutants by bio-electrochemical method according to claim 2, wherein, The distance between adjacent electrodes is the same, and the distance between adjacent electrodes is 10-15 cm.

4. The device for treating groundwater pollutants by bio-electrochemical method according to claim 2, wherein, The distance between the planting layer (4) and the titanium carbide electrode (1) in the first electrode pair is 10-15 cm.

5. The device for treating groundwater pollutants by bio-electrochemical method according to claim 2, wherein, The length of the filler layer (5) is the same as the length of the electrode; The distance between the filler layer (5) and its adjacent electrode is equal, and the distance is 5-7.5 cm.

6. A method of treating a groundwater pollutant, characterized by, The device for treating groundwater pollutants by bio-electrochemical method according to any one of claims 1-5, wherein the method comprises using a centrifugal pump to extract the groundwater to be treated from the extraction well into the device for treating groundwater pollutants by bio-electrochemical method.

7. The method according to claim 6, wherein, The flow rate of the groundwater to be treated in the device is 5-15 L / min; The flow-through time of the groundwater to be treated in the device is 3-9 min.

8. The method according to claim 6, wherein, The voltage applied to the two groups of electrodes is 0.5-6 V, and the voltage of the lower electrode pair is higher than that of the upper electrode pair.

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