NL2024123B1 - An electrochemical sewage treatment plant and process - Google Patents

Abstract

The invention belongs to the field of sewage treatment technology, specifically relates to an electrochemical sewage treatment plant which can effectively treat impurities, heavy metals and organic pollutants in sewage, and further discloses an electrochemical sewage treatment process. The sewage treatment plant in this invention consists of pretreatment reaction tank, sedimentation tank, electrolytic tank and regulating tank. In the electrolytic tank, the sewage is electrolyzed by electrifying the anode and cathode plates. The hydroxyl radical generated by electrochemical oxidation completely mineralizes the organic matter in the sewage, while the remaining heavy metal ions gain electrons and settle on the cathode to complete the decomposition and purification process of sewage. The electrochemical sewage treatment plant of the invention gives a higher overall treatment efficiency for sewage, and the treated sewage fully meets the emission standard.

Description

AN ELECTROCHEMICAL SEWAGE TREATMENT PLANT AND PROCESS

FIELD OF INVENTION The invention belongs to the field of sewage treatment technology, specifically relates to an electrochemical sewage treatment plant which can effectively treat impurities, heavy metals and organic pollutants in sewage, and further discloses an electrochemical sewage treatment process.

BACKGROUND OF THE PRESENT INVENTION With the rapid development of global economy, water pollution has gradually become a worldwide issue, especially in developing countries, and the treatment of industrial wastewater in China is a hot issue that needs to be tackled urgently. In the past decades, China's surface water and groundwater have been seriously polluted by industrial production, agricultural activities, municipal sewage and other sources. Especially with the increase of population, man's demand for water is continuously rising. How to treat sewage effectively and recover sewage properly is of great significance to sustainable development of economy and resources. Conventional wastewater treatment methods in existing technologies include mechanical treatment, physical treatment, chemical treatment, and biological treatment. However, with the improvement of people's living standards and continuous development of industrialization, the components of both domestic sewage and industrial sewage are becoming more and more complex, and there are more chances for possible types of organic matter in wastewater. Hence it is more difficult to treat the sewage. The common organic pollutants in sewage mainly include polycyclic aromatic hydrocarbons, nitrogen- containing organic compounds, halogenated hydrocarbons, heavy metal pollutants that cannot be degraded and other miscellaneous organic compounds, which makes the current conventional sewage treatment methods difficult to meet the desired performance and effect. The electrochemical treatment technology is a process that uses chemical reaction via electric energy to remove harmful substances from sewage. Electrochemical technology is widely used in the recycling of metals, the treatment of organic pollutants and suspended particles, the removal of grease from various industrial wastewaters and domestic wastewater, and other kinds of wastewater treatment. Electrochemical technology becomes popular and the focus of current research because of its advantages of no secondary pollution, good treatment effect, low operating cost and easy operation and management.

SUMMARY OF THE INVENTION Therefore, this invention aims to solve the technical issue by providing a simply-structured, easily operated and managed electrochemical sewage treatment plant that can significantly improve the effect of sewage treatment. The second technical issue this invention aims to solve is to provide an electrochemical sewage treatment process. To solve the above technical issues, the electrochemical sewage treatment plant in the invention comprises a successively connected pretreatment reaction tank, a sedimentation tank, an electrolytic tank and a regulating tank.

The electrolytic tank is provided with an independent electrolytic reaction tank, in which at least two groups of electrodes are arranged for electrolytic treatment.

The side wall of the electrolytic reaction tank and the inner wall of the electrolytic tank form a diversion channel for sewage to pass through.

The side wall of the electrolytic reaction tank includes a permeable overflow wall and a non-permeable barrier wall.

The overflow wall is arranged above the barrier wall, forming a continuous side wall structure.

The electrolytically treated sewage flows out of the electrolytic reaction tank through the overflow wall and flows into the regulating tank through the diversion channel.

Specifically, the electrolytic tank is also provided with a separator plate above the electrolytic reaction tank; the separator plate is fixed to the inner wall of the electrolytic tank.

The separator plate is provided with a diversion orifice, through which sewage of the electrolytic tank flows into the electrolytic reaction tank for electrolytic treatment.

Specifically, the inner diameter of the barrier wall is identical to that of the bottom plate of the electrolytic reaction tank, forming a cylinder- structured barrier zone; the inner diameter of the overflow wall gradually increases from the size of the bottom plate to that of the separator plate, forming an overflow zone in the shape of round table.

Specifically, the electrolytic tank is also provided with a driving assembly, which drives the electrolytic reaction tank to rotate.

Specifically, the electrode is covered with insulating adhesive material and has one end stuck securely to the separator plate and the other end extended into the electrolytic reaction tank.

Specifically, the electrode is provided in 4 to 10 groups, which are evenly distributed on and stuck securely to the separator plate.

Specifically, the electrolytic reaction tank is provided with an impurity collection strainer and/or a cleaning brush.

Specifically, the pretreatment reaction tank is provided with a stirring rod, which comprises several groups of arc blades, and there are several diversion needles distributed randomly on the blades.

The invention also discloses the application of the electrochemical sewage treatment plant in the field of sewage treatment.

The invention also discloses the electrochemical sewage treatment process based on the equipment, wherein the following steps are included: (1) The sewage to be treated enters the pretreatment reaction tank, to which pretreatment auxiliary agent is added and which is fully mixed under the action of the stirring rod.

(2) The mixed and reacted wastewater enters the sedimentation tank. The resulting sediment is discharged, and the remaining sewage enters the electrolysis tank.

(3) The sewage entering the electrolytic tank goes into the electrolytic reaction tank through the diversion orifice, and conducts electrochemical treatment under the action of the electrode. The decomposed sewage flows out of the electrolytic reaction tank through the overflow wall and flows into the regulating tank through the diversion channel. (4) The sewage flowing into the regulating tank is discharged after neutralization reaction treatment.

5 The sewage treatment plant in this invention consists of pretreatment reaction tank, sedimentation tank, electrolytic tank and regulating tank. In the electrolytic tank, the sewage is electrolyzed by electrifying the anode and cathode plates. The hydroxyl radical generated by electrochemical oxidation completely mineralizes the organic matter in the sewage, while the remaining heavy metal ions gain electrons and settle on the cathode to complete the decomposition and purification process of sewage. The electrochemical sewage treatment plant of the invention gives a higher overall treatment efficiency for sewage, and the treated sewage fully meets the emission standard.

The electrochemical sewage treatment plant in the invention, wherein the separator plate designed in the electrolytic tank not only can extend the time for sewage to enter the electrolytic reaction tank so as to increase the electrolytic effect, but also can be used to attach multiple groups of electrodes to the separator plate so as to form a fixed electrolytic zone. The side wall of the electrolytic reaction tank is arranged as a structure combining the separation with overflow, and the overflow zone is arranged above the separation zone, so that the sewage to be treated can go through an electrolytic process from bottom to top. Compared with the conventional electrolytic tank structure with the outlet arranged below, the electrochemical plant of the invention can effectively extend the reaction time of sewage in the electrolytic tank, facilitate complete oxidation of organic matter in sewage and removal of heavy metal ions, and effectively improve the effect of electrolytic treatment. The electrochemical sewage treatment plant in the invention, wherein the electrodes are fixed, but the body of the electrolytic reaction tank rotates along with the driving unit. On the one hand, it can increase the flow and contact area of sewage with the help of rotating eddy current. On the other hand, it is also useful for cleaning the tank wall with the cleaning brush to avoid impurities settling on the tank wall. In the electrochemical sewage treatment plant in the invention, an impurity collection strainer is further provided in the central area of the electrolytic reaction tank to further remove suspended impurities and floccules in sewage and improve the treatment effect. With the help of rotating electrolytic reaction tank, a vortex comes into being in the center of electrode. Since the suspended impurities and floccules are light in the sewage, they are rolled up by water and concentrated in the collection strainer so as to be cleared up from the reaction tank at anytime. In the electrochemical sewage treatment plant in the invention, an additional stirring rod is provided in the pretreatment reaction tank. The stirring rod is a combination of 3 to 6 arc blades, on which some cylindrical metal stick structured diversion needles are distributed randomly to change the rotating direction of water so as to obtain full reaction of flocculants and collectors with water. This is also useful for preventing impurities in the reaction tank from concentrating on the roots of the arc metal blades, thus improving the pretreatment effect.

BRIEF DESCRIPTION OF THE DRAWINGS

To easily and clearly understand the content of the invention, further detailed description of the invention is given as the following based on the specific embodiment of the invention and the attached drawings, wherein, Figure 1 is a structure diagram of the sewage treatment plant of the invention; Figure 2 is a structure diagram of the stirring rod of the invention; The callouts indicated in the drawings are: 1- pretreatment reaction tank, 2- sedimentation tank, 3- electrolytic tank, 4- regulating tank, 5- separator plate, 6- sewage receiving zone, 7- electrolytic reaction tank, 8- electrode, 9- diversion orifice, 10- bottom plate, 11- overflow wall, 12- barrier wall, 13- diversion channel, 14- impurity collection strainer, 15- stirring rod, 16- arc blade, 17- diversion needle, 18- reaction tank inlet, 19- reaction tank drain pipe, 20- mud discharger, 21- sedimentation tank drain pipe, 22- electrolytic tank drain pipe, 23- alkali box, 24- regulating tank outlet, 25- dosing opening, 26- cleaning brush, 27- rotary shaft.

DETAILED DESCRIPTION In the structure diagram as shown in Figure 1, the electrochemical sewage treatment plant in the invention comprises a successively connected pretreatment reaction tank (1), a sedimentation tank (2), an electrolytic tank (3) and a regulating tank (4).

According to the structure shown in Figure 1, the pretreatment reaction tank (1) is used to perform corresponding pretreatment of sewage to be treated. Sewage to be treated flows through the reaction tank inlet (18) into the pretreatment reaction tank (1), which is provided with a dosing opening (25) on top of it for adding flocculants and/or heavy metal collectors so as to remove impurities and heavy metals.

The heavy metal collectors can collect copper, zinc, nickel and other heavy metals, and perform pretreatment of sewage. The sewage after pretreatment is discharged into the sedimentation tank (2) through the reaction tank drain pipe (19).

To increase the mixing degree and effect of pretreatment, the pretreatment reaction tank (1) is also provided with a stirring rod (15), which is fixed on the left and right sides of the pretreatment reaction tank (1). According to the structure shown in Figure 2, the stirring rod (15) is an assembly of 3 to 6 arc blades (16), which are shaped with Some diversion needles (17) that are randomly distributed on the surfaces. The diversion needles (17) are preferably designed as cylindrical metal sticks, specifically with a diameter of 1.5-2.5cm and a height of 5-8cm and an appropriate distance of 5-8cm between the sticks.

According to the structure shown in Figure 1, the sedimentation tank (2) is used to settle and discharge the floccules, heavy metal and other sediments generated in the process of pretreatment. The sedimentation tank (2) of the invention is preferably a horizontal flow sedimentation tank, which is provided with mud discharger (20) on the bottom to discharge sediment. The remaining sewage flows into the electrolytic tank (3) through the sedimentation tank drain pipe (21). In the installation shown in Figure 1, the sedimentation tank drain pipe (21) is preferably set up in a position higher than the sewage inlet of the electrolytic tank.

According to the structure shown in Figure 1, the electrolytic tank (3) is provided with an independent electrolytic reaction tank (7), in which at least two groups of electrodes (8) are arranged for electrolytic treatment. The size of the electrolytic reaction tank (7) is smaller than that of the electrolytic tank (3). The side wall of the electrolytic reaction tank (7) and the inner wall of the electrolytic tank (3) form a diversion channel (13) for sewage to pass through. The electrolytic tank (3) also includes a power supply device, whose positive pole is wired for connection with anode of the electrode (8). The negative pole of the power supply device is wired for electric connection with the cathode of the electrode (8). According to the structure shown in Figure 1, the electrolytic tank (3) is also provided with a separator plate (5) positioned above the electrolytic reaction tank (7). A sewage receiving zone (6) is formed above the separator plate (5) and it receives sewage before it flows into the electrolytic tank (3). The size of the separator plate (5) is adaptable to the inner diameter of the electrolytic tank (3) and it is secured against the inner wall of the electrolytic tank (3). The separator plate (5) is provided with diversion orifice (9), through which the sewage in the sewage receiving zone (6) flows into the electrolytic reaction tank (7) for respective electrolytic treatment. The diversion orifice (9) is preferably designed in the central area of the separator plate (5) and its size can be determined according to sewage treatment capacity of the equipment.

According to the structure shown in Figure 1, the electrolytic reaction tank (7) includes a bottom plate (10) and integrated side walls comprising a permeable overflow wall (11) and a non-permeable barrier wall (12). The overflow wall (11) is made of screen material with selected aperture and the barrier wall (12) can be made of common non-permeable materials. According to the structure shown in Figure 1,

the overflow wall (11) is designed above the barrier wall (12) and they are shaped together to form continuous side wall structure so that the electrolytic reaction tank (7) forms an isolated space. The separator plate (5) is close to the top of the electrolytic reaction tank (7) and it can be further close to the overflow wall (11).

As an preferably selected structure, in the electrochemical sewage treatment plant of the invention shown in Figure 1, the inner diameter of the barrier wall (12) is identical to that of the bottom plate (10) of the electrolytic reaction tank (7), i.e. the bottom plate (10) and the barrier wall (12) may enclose to form a cylindrical barrier zone; the inner diameter of the overflow wall (11) gradually increases from the size of the bottom plate (10) to that of the separator plate (5), i.e. the bottom plate (10) and the overflow wall (11) may enclose to form an overflow zone in the shape of an inverse truncated cone. In the electrolytic reaction tank (7), the overflow zone is positioned above the barrier zone. The sewage to be treated flows into the electrolytic reaction tank (7) and goes directly into the barrier zone under gravity and is subject to electrochemical decomposition under the action of electrode (8). As the volume of incoming sewage increases, the sewage after treatment will be squeezed out of the electrolytic reaction tank (7) through the overflow wall (11) and flow into subsequent the regulating tank (4) through the diversion channel (13) and the electrolytic tank drain pipe (22).

In the electrochemical sewage treatment plant shown in Figure 1, the electrode (8) used for corresponding electrochemical treatment can be conventional electrode known in the existing technologies. Such as titanium based electrode with Ti base, anode coated with SnO2-Sb20s and cathode coated with Pt, higher oxygen evolution potential (i.e.

degradation efficiency) can be obtained. The titanium base can also be first coated with a layer of IrO2 in order to make it a SnO2-Sb205/lrO?/Ti electrode with considerably longer service life. In the equipment of the invention, the cathode plate and anode plate of the electrode (8) are both covered with insulating adhesive material, with one end securely bonded to the bottom end of the separator plate (5), while the other end fully extended into the electrolytic reaction tank (7) for electrochemical treatment of sewage. The electrode (8) of the equipment of the invention is preferably provided in 4 to 10 groups, with their ends evenly distributed and securely bonded to the bottom end of the separator plate (5), i.e. the electrodes (8) enclose a hollow rectangular zone.

In the sewage treatment plant of the invention, the electrolytic tank (3) is also provided with a driving assembly, which drives the rotary shaft (27) that brings along the electrolytic reaction tank (7). At the moment, the separator plate (5) and the electrodes (8) attached to the separator plate (5) stay static, while the tank bodies (including the bottom plate (10), the overflow wall (11) and the barrier wall (12)) of the electrolytic reaction tank (7) rotate together at a preferably set speed of 10-13 rpm so as to improve the effect of electrochemical decomposition.

Further in the sewage treatment plant of the invention, the electrolytic reaction tank (7) is also provided with a removable impurity collection strainer (14) which is close to the center so as to collect decomposed waste at any time. The impurity collection strainer (14) can be directly set up on the location of the rotary shaft (27) at a height of 23- 25cm. Due to the light weight of suspended impurities and floccules in sewage, it is easy to form a vortex in the center of electrode (8) during rotation of sewage and they can be brought along with water and concentrated in the impurity collection strainer (14) to complete impurity collection.

Meanwhile, in the equipment of the invention, each group of electrodes (8) can be provided with a cleaning brush (26), with a length equal to the height of electrode (8), on the adhesive material on the side wall close to the electrolytic reaction tank (7), which facilitates rotation of the electrolytic reaction tank (7) so as to clean the side walls of the electrolytic reaction tank (7). In the sewage treatment plant of the invention, specifically, the electrolytic reaction tank (7) can be provided with a diameter of 50-60cm and a height of 30-35cm, with 4 to 10 groups of electrodes (8) evenly distributed and attached to the separator plate (5). The electrode (8) is secured at a distance of 1-1.2cm from the edge of the separator plate (5) and its bottom should be 10-12cm from the bottom of tank.

For each group of electrodes (8), a distance of 8-10cm is required between the cathode and anode plates.

For other electrolytic tanks (3) with different sizes, the above dimensions can be referred to for scaling up or down accordingly.

In the electrochemical sewage treatment plant shown in Figure 1, the regulating tank (4) is connected with the alkali box (23), through which alkali can be added to the regulating tank (4) at any time.

After treatment in the electrolytic tank (3), the sewage flows into the regulating tank (4) through the electrolytic tank drain pipe (22), in which alkali is added to regulate the pH value of the sewage so as to make it meet the emission standard.

The treated water flowing out of the sewage treatment plant through the regulating tank outlet (24) can be collected or used for other purposes.

The electrochemical sewage treatment process of the invention is based on the electrochemical sewage treatment plant shown in Figure 1 above, which includes the following steps: (1) The sewage to be treated enters the pretreatment reaction tank (1), to which a regular amount of auxiliary agents such as flocculant and/or heavy metal collector is added to remove impurities and heavy meals and which is fully mixed and pre-treated under the action of the stirring rod (15). (2) After mixing and pretreatment, the wastewater is discharged through the reaction tank drain pipe (19) and flows into the sedimentation tank (2). The resulted sediment is discharged through the mud discharger (20) and the remaining sewage flows into the electrolytic tank (3) through the sediment tank drain pipe (21). (3) The sewage in the electrolytic tank (3) flows through the diversion orifice (9) into the rectangular electrolytic zone formed by several groups of electrodes (8) in the electrolytic reaction tank (7) and is subject to electrochemical treatment under the action of the electrodes (8). The sewage goes directly into the barrier zone under gravity and is subject to electrochemical decomposition under the action of electrodes (8). As the volume of incoming sewage increases, the sewage after treatment will be squeezed out of the electrolytic reaction tank (7) through the overflow wall (11) and flow into subsequent the regulating tank (4) through the diversion channel (13) and the electrolytic tank drain pipe (22). (4) The sewage flowing into the regulating tank (4) is neutralized by alkali added to it.

The treated sewage flows out of the sewage treatment plant through the regulating tank outlet (24) for collection or other purposes.

Example of effectiveness The above electrochemical sewage treatment plant is used to treat the sewage in the industrial park.

The inlet and outlet water quality indexes are shown in Table 1 below.

Table 1 Inlet and outlet water quality indexes (mg/L) paramet | concentrati n limit er on Outlet Rate of Outlet Rate of Outlet Rate of concentratio | remova | concentratio | remova | concentratio | remova n I n | n | Pm | es | 78 [| | es | ~ | 73 | — | eo | It can be seen that the conventional indexes of effluent water quality treated by the electrochemical sewage treatment plant of the invention all conform to the level A standard of Comprehensive Sewage Discharge Standard (GB 8978-1996), and a better sewage treatment effect is obtained.

It is clear that the above embodiment is only an example given for clear illustration and is not restriction on the mode of implementation.

For the general technical personnel in the field, other different forms of changes or modifications can be made on the basis of the above description.

It is neither necessary nor possible to exhaust all modes of implementation.

Any obvious change or modification derived therefrom is still within the scope of protection of the invention.

Claims (10)

Conclusions 1. An electrochemical sewage treatment apparatus having a pre-treatment tank (1), a sludge tank (2), an electrolytic tank (3) and a matching tank (4) connected in series, characterized in that: The electrolytic tank (3) is provided with an independent electrolytic reaction tank (7); the electrolytic reaction tank (7) is provided with at least two sets of electrodes (8) for electrolytic treatment; between the side wall of the electrolytic reaction tank (7) and the inner wall of the electrolytic tank (3) it forms a flow-conducting channel (13) for the passage of sewage; The side wall of the electrolytic reaction tank (7) includes a water-permeable overflow wall (11) and a water-impermeable partition wall (12), and the overflow wall (11) is placed above the partition wall (12) and forms a continuous side wall structure; the sewage treated by the electrolytic reaction cell (7) is discharged through the overflow wall (11) from the electrolytic reaction cell (7) and flows through the flow conduction channel (13) into the matching tank (4). The electrochemical sewage treatment apparatus according to claim 1, characterized in that the electrolytic tank (3) further comprises a separator plate (5) located above the electrolytic reaction cell (7); the partition plate (5) is fixed to an inner wall of the electrolytic tank (3), and the partition plate (5) is provided with a flow conduction hole (9) and the sewage flowing in the electrolytic tank (3) through the flow conduction hole (9) in the electrolytic reaction tank (7) for electrolytic treatment. The electrochemical sewage treatment apparatus according to claim 2, characterized in that the inner wall of the partition wall (12) has the same inner diameter as the bottom plate (10) of the electrolytic reaction cell (7) to form a separation region of the cylinder structure; the inner diameter of the overflow wall (11) is gradually increased from the size of the bottom plate (10) to the size of the partition plate (5) to form an overflow area of the frustoconical structure. The electrochemical sewage treatment apparatus according to any one of claims 1 to 3, characterized in that the electrolytic tank (3) further comprises a driving assembly and the driving assembly drives the electrolytic reaction tongs (7) to rotate. The electrochemical sewage treatment plant according to any one of claims 1-4, characterized in that the electrodes (8) are covered with an insulating viscous material and one end is connected and fixed to the separator plate (5) while the other end protrudes in the electrolytic reaction tank (7). The electrochemical sewage treatment apparatus according to any one of claims 1-5, characterized in that the electrodes (8) are 4-10 sets, and are evenly distributed and connected and fixed on the separator plate (5). The electrochemical sewage treatment apparatus according to any one of claims 1 to 6, characterized in that the electrolytic reaction tank (7) is further provided with an impurity collecting net (14) and/or a cleaning brush (26). The electrochemical sewage treatment apparatus according to any one of claims 1 to 7, characterized in that the pre-treatment tank (1) is provided with a stirring rod (15) and the stirring rod (15) comprises a plurality of groups of curved arc blades (16) and a plurality of randomly distributed flow guide needles (17) are formed on the surface of the blades (16). Use of an electrochemical sewage treatment plant according to any one of claims 1-8 in the field of sewage treatment. An electrochemical sewage treatment process based on the apparatus according to any one of claims 1-8, characterized in that it comprises the steps of: (1) the sewage to be treated enters the pre-treatment tank (1) and a pre-treatment aid is added and then mixed thoroughly under the influence of the stir bar (15); (2) the mixed and reacted sewage enters the sediment tank (2), the resulting sediment is discharged, and the remaining sewage enters the electrolytic tank (3): (3) the sewage entering the electrolytic tank (3) enters the electrolytic reaction tank (7) enters through the flow conduction hole (9) and is electrochemically treated under the influence of the electrodes (8); the dissolved sewage flows through the overflow wall (11) from the electrolytic reaction tank (7) and then flows through the flow-conducting channel (13) into the matching tank (4); (4) The sewage flowing into the adjustment tank (4) is discharged after the neutralization reaction treatment.