Sewage plant tail water treatment system and treatment method

Abstract

The invention discloses a sewage plant tail water treatment system and method, and relates to the technical field of sewage treatment.The sewage plant tail water treatment system is applied to tail water generated by a sewage plant adopting an ozone advanced oxidation technology, and the treatment system comprises an activated carbon reaction device, a denitrification reaction device, an ecological pond and a horizontal subsurface flow wetland; the activated carbon reaction device is communicated with the tail water pipe and comprises an activated carbon filtering layer, and the activated carbon filtering layer is used for adsorbing chemical oxygen demand and dissolved oxygen in tail water; the denitrification reaction device is communicated with the activated carbon reaction device and comprises a denitrification filter material layer, and the denitrification filter material layer is used for autotrophic denitrification nitrogen removal of tail water; the ecological pond is communicated with the denitrification reaction device and comprises aquatic plants and aquatic animals; the horizontal subsurface flow wetland is communicated with the ecological pond and is used for deeply filtering the tail water. The treatment system can improve the purification effect of the tail water of the sewage plant.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a wastewater treatment system and method for treating wastewater effluent from a wastewater treatment plant. Background Technology

[0002] Ozone advanced oxidation is a widely adaptable wastewater treatment technology that can effectively treat various recalcitrant organic wastewaters (such as wastewater from printing and dyeing, chemical, pesticide, papermaking, and electroplating industries) and significantly reduce wastewater color. The application of this technology helps improve the overall quality of wastewater treatment plant effluent.

[0003] In recent years, with the continuous improvement of national environmental quality requirements and the gradual implementation of water environment quality ranking mechanisms, the discharge standards of sewage treatment plants have become increasingly stringent. Therefore, advanced treatment of effluent has become particularly important. Ecological ponds, as a typical ecological treatment technology, have been widely used in advanced effluent treatment due to their advantages such as low construction and operating costs, simple operation and maintenance, and environmental beautification functions. However, the effluent from sewage treatment plants using ozone advanced oxidation processes is characterized by a low concentration of bioavailable organic matter, making it unsuitable for further COD (chemical oxygen demand) removal via biological methods in advanced treatment. It is also difficult to achieve efficient nitrogen removal through heterotrophic denitrification. Furthermore, the high dissolved oxygen concentration in the effluent also inhibits the denitrification process.

[0004] Therefore, current treatment systems are not effective in purifying wastewater effluent. In the fields of ecology, environment and wetland science, developing enhanced ecological pond treatment technologies suitable for this type of effluent has become an important and urgent need. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a wastewater treatment system and method for treating wastewater effluent, thereby solving the technical problem of insufficient purification effect of wastewater effluent in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a wastewater treatment system for wastewater treatment plants. This system is applied to wastewater generated by wastewater treatment plants employing ozone advanced oxidation technology. The system includes an activated carbon reactor, a denitrification reactor, an ecological pond, and a horizontal subsurface flow wetland. The activated carbon reactor is connected to the wastewater pipe and includes an activated carbon filter layer that adsorbs chemical oxygen demand (COD) and dissolved oxygen in the wastewater. The denitrification reactor is connected to the activated carbon reactor and includes a denitrification filter layer for autotrophic denitrification of the wastewater. The ecological pond is connected to the denitrification reactor and includes aquatic plants and animals. The horizontal subsurface flow wetland is connected to the ecological pond and is used for deep filtration of the wastewater.

[0007] In some embodiments, the bottom of the activated carbon reactor is connected to the tailwater pipe, the top of the activated carbon reactor is connected to the top of the denitrification reactor, and the bottom of the denitrification reactor is connected to the ecological pond.

[0008] In some embodiments, the liquid level in the activated carbon reactor is higher than that in the denitrification reactor, and the height difference between the two is less than 30 cm.

[0009] In some embodiments, the top of the activated carbon reactor is connected to the tailwater pipe, the bottom of the activated carbon reactor is connected to the bottom of the denitrification reactor, and the top of the denitrification reactor is connected to the ecological pond.

[0010] In some embodiments, the activated carbon reactor and the denitrification reactor are respectively provided with water and air distribution plates for support. The water and air distribution plates are annular and uniformly provided with multiple round holes. The diameter of the round holes satisfies 3mm≤a≤5mm.

[0011] In some embodiments, the activated carbon filter layer comprises granular activated carbon, and in other embodiments, the activated carbon filter layer comprises columnar activated carbon.

[0012] In some embodiments, the activated carbon reactor is provided with a first backwash pipe at the bottom and a first backwash pump connected to the first backwash pipe; the denitrification reactor is provided with a second backwash pipe at the bottom and a second backwash pump connected to the second backwash pipe.

[0013] In some embodiments, the aquatic plants include at least three of the following: Vallisneria natans, Myriophyllum spicatum, Hydrilla verticillata, Ceratophyllum demersum, Potamogeton malaianum, Potamogeton microdentula, Potamogeton pectinatus, and Potamogeton crispus.

[0014] In some embodiments, the horizontal subsurface flow wetland includes an inlet zone, a main zone, and an outlet zone in sequence, wherein the particle size of the inlet zone and the outlet zone is larger than that of the main zone.

[0015] Secondly, the present invention also provides a method for treating wastewater effluent from a wastewater treatment plant, applied to the aforementioned wastewater effluent treatment system. The treatment method includes: starting the treatment system; the effluent enters an activated carbon reactor through an effluent pipe, the filtration rate of the activated carbon reactor being 1.275 m / h-3.5 m / h, and the effluent retention time being 35 min-98 min; the effluent leaves the activated carbon reactor and enters a denitrification reactor, the filtration rate of the denitrification reactor being 2.12 m / h-5.94 m / h, and the effluent retention time being 21 min-60 min; the effluent leaves the denitrification reactor and enters an ecological pond, where it remains for 1-2 days; and the effluent leaves the ecological pond and enters a horizontal subsurface flow wetland, where it remains for 0.5-1 day.

[0016] Compared with existing technologies, the wastewater treatment system provided by this invention employs a combined process integrating activated carbon reactors, denitrification reactors, ecological ponds, and horizontal subsurface flow wetlands. This approach overcomes the inhibition of denitrification by excessively high dissolved oxygen concentrations in the effluent, improving nitrogen removal efficiency and conserving carbon sources. Furthermore, it efficiently removes residual non-biodegradable organic matter from the effluent, comprehensively improving effluent quality and meeting stricter discharge standards. This solves the problem of low concentrations of bioavailable organic matter and high dissolved oxygen concentrations in effluent treated by ozone advanced oxidation processes, thus enhancing the purification effect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a wastewater treatment system for wastewater treatment plants provided by an embodiment of the present invention; Figure 2 This is a schematic diagram of the flow of tailwater transfer between the activated carbon reactor and the denitrification reactor provided in this embodiment of the invention. Figure 3 This is another flow diagram illustrating the tailwater transfer between the activated carbon reactor and the denitrification reactor provided in this embodiment of the invention. Figure 4 This is a schematic diagram of the structure of a water and air distribution plate provided in an embodiment of the present invention; Figure 5 This is a schematic flowchart of a wastewater treatment method for wastewater treatment provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 100. Processing system; 110. Activated carbon reaction device; 111. Activated carbon filter layer; 112. Support layer; 113. Water and air distribution plate; 1131. Circular hole; 114. Top of the activated carbon reactor; 115. Bottom of the activated carbon reactor; 120. Denitrification reactor; 121. Denitrification filter bed; 122. Top of denitrification reactor; 123. Bottom of denitrification reactor; 130. Ecological pond; 131. Emergent plants; 132. Submerged plants; 133. Planting soil; 140. Horizontal subsurface flow wetland; 141. Inlet area; 142. Main area; 143. Outlet area; 144. Wetland plants; 150. Tailwater pipe; 160. Water pipes; 170. Backwash pipe; 171. Backwash air pipe; 172. Backwash water pipe; 180. Backwash pump; 181. Air compressor; 182. Backwash water pump. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Ecological ponds, as a typical ecological treatment technology, have been widely used in advanced effluent treatment due to their advantages such as low construction and operating costs, simple operation and maintenance, and environmental beautification functions. However, the effluent from wastewater treatment plants using ozone advanced oxidation processes is characterized by a low concentration of bioavailable organic matter, making it unsuitable for further COD removal using biological methods in advanced treatment, and also difficult to achieve efficient nitrogen removal through heterotrophic denitrification. In addition, the high dissolved oxygen concentration in the effluent also inhibits the denitrification process.

[0021] To address the technical problem of insufficient purification effect of wastewater treatment plant effluent in existing technologies, this invention provides a wastewater treatment system for wastewater treatment plants. By employing a combined process integrating activated carbon reactors, denitrification reactors, ecological ponds, and horizontal subsurface flow wetlands, this system overcomes the inhibition of denitrification by excessively high dissolved oxygen concentrations in the effluent, improving nitrogen removal efficiency and conserving carbon sources. Furthermore, it efficiently removes residual non-biodegradable organic matter from the effluent, comprehensively improving effluent quality and meeting more stringent discharge standards. This solves the problem of low concentrations of bioavailable organic matter and high dissolved oxygen concentrations in effluent treated by ozone advanced oxidation processes, thus enhancing the purification effect.

[0022] It should be noted that the treatment system of the present invention is used for, but not limited to, the treatment of effluent from sewage treatment plants. For ease of explanation, this invention will only use the application of the treatment system to the treatment of effluent from sewage treatment plants as an example. The principle of the treatment system applied to the treatment of other effluents treated by ozone advanced oxidation process is essentially the same as that applied to the treatment of effluent from sewage treatment plants, and will not be described in detail here.

[0023] This application provides a wastewater treatment system 100 for wastewater treatment plants. The wastewater treatment system 100 is applied to the wastewater generated by wastewater treatment plants using ozone advanced oxidation technology, such as... Figure 1 As shown, the treatment system 100 includes an activated carbon reactor 110, a denitrification reactor 120, an ecological pond 130, and a horizontal subsurface flow wetland 140. The activated carbon reactor 110 is connected to the effluent pipe 150 and includes an activated carbon filter layer 111, which adsorbs the chemical oxygen demand and dissolved oxygen in the effluent. The denitrification reactor 120 is connected to the activated carbon reactor 110 and includes a denitrification filter layer 21, which is used for autotrophic denitrification of the effluent. The ecological pond 130 is connected to the denitrification reactor 120 and includes aquatic plants and aquatic animals. The horizontal subsurface flow wetland 140 is connected to the ecological pond 130 and is used for deep filtration of the effluent.

[0024] The activated carbon reactor 110 is a device for adsorbing and degrading COD in the effluent of a wastewater treatment plant using ozone advanced oxidation technology, and for adsorbing dissolved oxygen in the effluent.

[0025] The activated carbon reaction device 110 includes, from top to bottom, an activated carbon filter layer 111, a support layer 112, and a water and air distribution plate 113. The filter media used in the activated carbon filter layer 111 is not limited; relevant embodiments will be given later, and it will not be described here. The support layer 112 is used to support the activated carbon filter layer 111. The filling material of the support layer 112 can be determined according to requirements; for example, the support layer 112 can be filled with pebbles with a particle size of 10-20 mm.

[0026] The effluent enters the activated carbon reactor 110 through the effluent pipe 150 and undergoes adsorption filtration. The filtration rate and residence time of the effluent in the activated carbon reactor 110 can be determined according to actual needs. For example, the filtration rate is between 1.27-3.5 m / h, specifically 1.3 m / h, 1.5 m / h, 2 m / h, 3 m / h, 3.5 m / h, etc. The residence time is between 35-98 min, specifically 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 98 min, etc.

[0027] The denitrification reactor 120 is a device used for autotrophic denitrification and nitrogen removal of effluent.

[0028] The denitrification reactor 120 includes, from top to bottom, a denitrification filter media layer 121, a support layer 112, and a water and air distribution plate 113. The filter media used in the denitrification filter media layer 121 is not limited; for example, it can be a sulfur-based composite packing material with a particle size of 1-6 mm. The support layer 112 in the denitrification reactor 120 can be the same as the support layer 112 in the activated carbon reactor 110.

[0029] The effluent flows through water pipe 160 from activated carbon reactor 110 into denitrification reactor 120. The filtration rate and residence time of denitrification reactor 120 can be determined according to actual needs. For example, the filtration rate is between 2.12-5.94 m / h, specifically 2.2 m / h, 3 m / h, 4 m / h, 5 m / h, 5.94 m / h, etc. The residence time is between 21-60 min, specifically 25 min, 30 min, 40 min, 50 min, 60 min, etc. The volumetric loading rate is 0.14-0.41 kg NO3-N / (m³). 3 ·d).

[0030] Ecological pond 130 is used to further purify the effluent filtered by denitrification reactor 120. The effluent enters ecological pond 130 from denitrification reactor 120 through water pipe 160.

[0031] The ecological pond 130 comprises, from top to bottom, emergent plants 131, submerged plants 132, and planting soil 133. The depth, plant species, and animal species of the ecological pond 130 can be determined according to actual needs. For example, the water depth of the ecological pond 130 is between 1.5 and 2.5 meters, specifically 1.5 meters, 1.8 meters, 12 meters, and 2.5 meters; the tailwater retention time is between 1 and 2 days; and the thickness of the planting soil 133 is 20-40 cm, which can be ordinary planting soil or river / pond mud.

[0032] Submerged plants 132 include, but are not limited to, *Vallisneria natans*, *Myriophyllum spicatum*, *Hydrilla verticillata*, *Ceratophyllum demersum*, *Potamogeton malaianus*, *Potamogeton microdentula*, *Potamogeton pectinatus*, and *Potamogeton crispus*. The planting depth for submerged plants 132 is 0.5-2.0m, with a coverage of greater than 30% and a planting density of 80-120 plants / m². 2 For example, 85 plants / m 2 90 plants / m 2 100 plants / m 2 110 plants / m 2 120 plants / m 2 etc.

[0033] Emergent plants 131 include, but are not limited to, canna lilies, irises, thaliana, umbrella sedge, and variegated reed. Emergent plants 131 should be planted in water depths less than 0.5m. Specific species and planting area can be determined based on landscape requirements, with a planting density of, for example, 20-40 plants / m². 2 For example, 20 plants / m 2 30 plants / m 2 40 plants / m 2 etc.

[0034] Aquatic animals include, but are not limited to, filter-feeding fish and benthic animals. Filter-feeding fish include, but are not limited to, silver carp and bighead carp. For example, the stocking size is 150-200g / fish, the stocking ratio of silver carp to bighead carp is 3:2, and the stocking density is 40-70g / m³. 3 Benthic animals, including but not limited to snails and clams, should be stocked at a density of 180-220 g / m³. 2 The release area covers 10-15% of the surface area of ​​the ecological pond.

[0035] The horizontal subsurface flow wetland 140 is used to further treat the effluent from the ecological pond 130. The effluent enters the horizontal subsurface flow wetland 140 from the ecological pond 130 through the water pipe 160.

[0036] The horizontal subsurface flow wetland 140 includes an inlet zone 141, a main zone 142, an outlet zone 143, and wetland vegetation 144; the tailwater flows sequentially through the inlet zone 141, the main zone 142, and the outlet zone 143. For example, the depth of the horizontal subsurface flow wetland 140 is between 0.6 and 1.6 meters, specifically 0.6 meters, 0.8 meters, 1 meter, 1.2 meters, 1.6 meters, etc. The tailwater retention time is 0.5 to 1 day, and the hydraulic loading is 0.5 to 1.0 meters. 3 / (m 2 ·d).

[0037] The inlet zone 141 is 1.0-1.5m long and can be filled with crushed stone, gravel, or pebbles; the outlet zone 143 is 0.8-1.0m long and can be filled with crushed stone, gravel, or pebbles; the main zone 142 can be filled with gravel, crushed stone, pebbles, zeolite, volcanic rock, ceramsite, limestone, slag, furnace slag, vermiculite, blast furnace slag, shale, or steel slag, etc.

[0038] Wetland plants 144 are located above the inlet area 141, the main area 142, and the outlet area 143. Wetland plants 144 include, but are not limited to, canna lilies, irises, thaliana, umbrella sedge, variegated reeds, etc. The specific species can be determined according to the landscape requirements, and the planting density is, for example, 20-40 plants / m². 2 .

[0039] By employing a combined process integrating activated carbon reactor 110, denitrification reactor 120, ecological pond 130, and horizontal subsurface flow wetland 140, the process overcomes the inhibition of denitrification by excessively high dissolved oxygen concentration in the effluent, improving nitrogen removal efficiency and conserving carbon sources. Furthermore, it efficiently removes residual non-biodegradable organic matter from the effluent, comprehensively improving effluent quality and meeting stricter discharge standards. This addresses the issues of low concentrations of bioavailable organic matter and high dissolved oxygen concentrations in the effluent after ozone advanced oxidation treatment, thus enhancing the purification effect.

[0040] In some embodiments, such as Figure 2 As shown, the bottom 115 of the activated carbon reactor is connected to the tailwater pipe 150, the top 114 of the activated carbon reactor is connected to the top 122 of the denitrification reactor, and the bottom 123 of the denitrification reactor is connected to the ecological pond 130.

[0041] In this embodiment, the activated carbon reactor 110 adopts a bottom-in, top-out configuration, while the denitrification reactor 120 adopts a top-in, bottom-out configuration. The effluent from the top 114 of the activated carbon reactor flows directly into the top 122 of the denitrification reactor, resulting in a simpler process layout and smoother water flow. The activated carbon reactor 110 uses a bottom-in, top-out configuration, with the effluent flowing upwards through the activated carbon filter layer 111. The impact force of the water flow reduces the deposition of suspended solids between activated carbon particles, extends the service life of the activated carbon, and reduces the frequency of backwashing.

[0042] In some embodiments, the liquid level in the activated carbon reactor 110 is higher than the liquid level in the denitrification reactor 120, and the height difference between the two liquid levels is less than 30 cm.

[0043] In this embodiment, the height difference between the two liquid levels is controlled to be less than 30cm. Gravity can be used to achieve flow, reducing energy consumption. At the same time, water splashing and reoxygenation caused by water droplets are avoided, ensuring the anaerobic environment for denitrification and improving the purification effect.

[0044] In some embodiments, such as Figure 3 As shown, the top 114 of the activated carbon reactor is connected to the tailwater pipe 150, the bottom 115 of the activated carbon reactor is connected to the bottom 123 of the denitrification reactor, and the top 122 of the denitrification reactor is connected to the ecological pond 130.

[0045] In this embodiment, the activated carbon reactor 110 adopts a top-in, bottom-out design, while the denitrification reactor 120 adopts a bottom-in, top-out design. The effluent from the bottom 115 of the activated carbon reactor flows directly into the bottom 123 of the denitrification reactor, resulting in a simpler process layout and smoother water flow. The activated carbon reactor 110, with its top-in, bottom-out design, allows the effluent to flow downwards through the activated carbon filter layer 111, where gravity facilitates full contact with the activated carbon particles, preventing short-circuiting and improving the adsorption efficiency for COD and trace pollutants. The denitrification reactor 120, with its bottom-in, top-out design, pushes the water upwards from the bottom, ensuring uniform contact between the effluent and the autotrophic denitrification packing material (such as sulfur autotrophic packing material). The minimal water flow disturbance helps maintain the stability of the biofilm on the packing layer surface, ensuring an anaerobic or low-oxygen environment and reducing the probability of reoxygenation. Furthermore, entering from the bottom 123 of the denitrification reactor avoids sludge accumulation on the top of the denitrification filter layer 121, reducing the risk of clogging.

[0046] In some embodiments, such as Figure 1 and Figure 4 As shown, the activated carbon reaction device 110 and the denitrification reaction device 120 are respectively provided with water and air distribution plates 113 for support. The water and air distribution plates 113 are annular and uniformly provided with multiple round holes 1131. The diameter of the round holes 1131 satisfies 3mm≤a≤5mm.

[0047] In this embodiment, a support layer 112 is supported above the water and air distribution plate 113 in the activated carbon reactor 110, and an activated carbon filter layer 111 is supported above the support layer 112; similarly, a support layer 112 is supported above the water and air distribution plate 113 in the denitrification reactor 120, and a denitrification filter media layer 121 is supported above the support layer 112. The water and air distribution plate 113 can be configured according to the shape of the device. For example, the water and air distribution plate 113 can be a ring structure with multiple evenly distributed circular holes 1131. The diameter 'a' of the circular holes 1131 is between 3mm and 5mm, specifically 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or any value between two adjacent values ​​mentioned above. The multiple circular holes 1131 serve as flow channels for the effluent.

[0048] In some embodiments, the activated carbon filter layer 111 includes granular activated carbon, the particle size of which can be determined according to actual needs, such as 8-30 mesh granular activated carbon; granular activated carbon has a large specific surface area and fast adsorption rate, can efficiently capture refractory organic matter in effluent, and is not easily clogged, with low operation and maintenance costs.

[0049] In some embodiments, the activated carbon filter layer 111 includes columnar activated carbon, the size of which can be determined according to actual needs, for example, columnar activated carbon with a diameter of 1.5-2.0 mm; columnar activated carbon has high strength, long service life, and uniform pore size of the filler layer, resulting in stable water flow distribution.

[0050] In some embodiments, the activated carbon filter layer 111 includes both granular activated carbon and columnar activated carbon.

[0051] In some embodiments, such as Figures 1 to 3 As shown, the activated carbon reaction device 110 is provided with a first backwash pipe at the bottom and a first backwash pump connected to the first backwash pipe; the denitrification reaction device 120 is provided with a second backwash pipe at the bottom and a second backwash pump connected to the second backwash pipe.

[0052] In this embodiment, both the activated carbon reactor 110 and the denitrification reactor 120 are equipped with backwashing devices, which are capable of water washing and air washing. The backwashing device includes a backwash pipe 170 and a backwash pump 180. The backwash pipe 170 includes a backwash air pipe 171 and a backwash water pipe 172; the backwash pump 180 includes an air compressor 181 and a backwash water pump 182. The backwash air pipe 171 is connected to the air compressor 181, and the backwash water pipe 172 is connected to the backwash water pump 182.

[0053] In this embodiment, the activated carbon reactor 110 is backwashed. The first backwash pipe includes a backwash air pipe 171 and a backwash water pipe 172. The first backwash pump includes an air compressor 181 and a backwash water pump 182. One end of the backwash air pipe 171 and the backwash water pipe 172 is located at the bottom 115 of the activated carbon reactor, used for air washing and water washing of the activated carbon reactor 110. For example, the activated carbon reactor 110 can adopt a combined air-water washing method, with an air washing intensity of 54-61.2 m. 3 / (m 2 ·h), rinsing time 3-5min; water flushing intensity 25.2-43.2m 3 / (m 2 ·h), rinsing time 8-12min, rinsing frequency 5-10 times / month.

[0054] In this embodiment, the denitrification reactor 120 is backwashed. The second backwash pipe includes a backwash air pipe 171 and a backwash water pipe 172. The second backwash pump includes an air compressor 181 and a backwash water pump 182. One end of the backwash air pipe 171 and the backwash water pipe 172 is located at the bottom 123 of the denitrification reactor, used for air washing and water washing of the denitrification reactor 120. For example, the denitrification reactor 120 can be flushed using a combined air-water flushing method, with air flushing for 3-6 minutes and an air flushing intensity of 90-120 m³ / min. 3 / (m 2 • h); combined air-water flushing for 10-15 min, air flushing intensity 90-120 m 3 / (m 2 •h), water flushing intensity 15-20m 3 / (m2 •h); Water flush alone for 10-15 minutes, water flushing intensity 15-20m 3 / (m 2 ·h), the rinsing frequency is 2-4 times / month.

[0055] In some embodiments, such as Figure 1 As shown, the submerged plants 132 in the aquatic plants include at least three of the following: *Vallisneria natans*, *Myriophyllum spicatum*, *Hydrilla verticillata*, *Ceratophyllum demersum*, *Potamogeton malaianus*, *Potamogeton microdentula*, *Potamogeton pectinatus*, and *Potamogeton crispus*. By providing a variety of submerged plants 132, the diversity of the ecological pond 130 is enhanced, thereby improving the water purification effect.

[0056] In some embodiments, such as Figure 1 As shown, the horizontal subsurface flow wetland 140 includes an inlet zone 141, a main zone 142, and an outlet zone 143 in sequence. The particle size of the inlet zone 141 and the outlet zone 143 is larger than that of the main zone 142.

[0057] In this embodiment, the inlet zone 141 can be filled with crushed stone, gravel, or pebbles with a particle size of 3.0-6.0 cm; the outlet zone 143 can be filled with crushed stone, gravel, or pebbles with a particle size of 3.0-6.0 cm; and the main zone 142 can be filled with gravel, crushed stone, pebbles, zeolite, volcanic rock, ceramsite, limestone, slag, furnace slag, vermiculite, blast furnace slag, shale, or steel slag, with a particle size of 1.0-3.0 cm. By designing the particle size of the inlet zone 141 and outlet zone 143 to be larger than that of the main zone 142, the larger particle size fillers in the inlet zone 141 and outlet zone 143 can evenly distribute water, trap impurities to prevent clogging of the main zone 142, and also provide support for the main zone 142, ensuring wetland purification efficiency.

[0058] This application embodiment also provides a wastewater treatment method 300, applied to the aforementioned wastewater treatment system 100, such as... Figure 5 As shown, the processing method 300 includes: Step S310: Start the treatment system 100. The effluent enters the activated carbon reactor 110 through the effluent pipe 150. The filtration rate of the activated carbon reactor 110 is 1.275 m / h-3.5 m / h, and the effluent retention time is 35 min-98 min.

[0059] Specifically, when the treatment system 100 is started, the effluent from the wastewater treatment plant, which uses ozone advanced oxidation technology, flows into the activated carbon reactor 110 through the effluent pipe 150. The activated carbon filter layer 111 in the activated carbon reactor 110 adsorbs and degrades the COD in the effluent and adsorbs the dissolved oxygen in the effluent. The filtration rate of the entire activated carbon reactor 110 is, for example, 1.3 m / h, 1.5 m / h, 2 m / h, 3 m / h, 3.5 m / h, etc., and the effluent retention time is, for example, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 98 min, etc.

[0060] In step S320, the effluent leaves the activated carbon reactor 110 and enters the denitrification reactor 120. The filtration rate of the denitrification reactor 120 is 2.12 m / h-5.94 m / h, and the effluent retention time is 21 min-60 min.

[0061] Specifically, the effluent enters the denitrification reactor 120 through water pipe 160, where the denitrification filter layer 121 in the denitrification reactor 120 performs autotrophic denitrification to remove nitrogen from the effluent. The flow rate of the entire denitrification reactor 120 is, for example, 2.2 m³ / h, 3 m³ / h, 4 m³ / h, 5 m³ / h, 5.94 m³ / h, etc., and the effluent retention time is, for example, 25 min, 30 min, 40 min, 50 min, 60 min, etc.

[0062] In step S330, the effluent leaves the denitrification reactor 120 and enters the ecological pond 130. The effluent stays in the ecological pond 130 for 1-2 days. Specifically, the wastewater enters the ecological pond 130 through water pipe 160, where it undergoes further purification. The purification retention time is 1 or 2 days.

[0063] In step S340, the tailwater leaves the ecological pond 130 and enters the horizontal subsurface flow wetland 140. The tailwater stays in the horizontal subsurface flow wetland 140 for 0.5 days to 1 day.

[0064] Specifically, the effluent enters the horizontal subsurface flow wetland 140 through water pipe 160, where it undergoes further advanced treatment. The advanced treatment retention time is 0.5 days or 1 day.

[0065] To better understand this invention, the following is combined with... Figures 1 to 4 The technical solution of the present invention will be described in detail below: In some embodiments, the treatment system 100 includes an activated carbon reactor 110, a denitrification reactor 120, an ecological pond 130, and a horizontal subsurface flow wetland 140, with the activated carbon reactor 110 connected to the tailwater pipe 150.

[0066] In this embodiment, the support layer 112 of the activated carbon reactor 110 is filled with pebbles with a particle size of 20 mm and a filling height of 20 cm. The activated carbon filter layer 111 uses granular activated carbon with a particle size of 8-30 mesh and a filling height of 2.1 m. The filtration rate of the activated carbon reactor 110 is 1.27 m / h, and the residence time is 98 min. The backwashing of the activated carbon reactor 110 adopts a combined air-water flushing method, with an air flushing intensity of 55 m. 3 / (m 2 ·h), rinsing time 5min; water flushing intensity 40m 3 / (m 2 ·h), rinsing time 10min, rinsing frequency 6 times / month.

[0067] In this embodiment, the support layer 112 of the denitrification reactor 120 is filled with pebbles with a particle size of 20 mm and a filling height of 20 cm. The denitrification filter layer 121 uses sulfur-based composite filler with a particle size of 1-6 mm and a filling height of 2.1 m. The denitrification reactor 120 has a filtration rate of 4.25 m / h, a residence time of 30 min, and a volumetric loading rate of 0.29 kg NO3-N / (m³). 3 ·d). The backwashing of the denitrification reactor 120 adopts a combined air-water flushing method, first air flushing and then water flushing, with air flushing alone lasting 3 minutes and an air flushing intensity of 90 m. 3 / (m 2 • h); combined air and water flushing for 10 min, air flushing intensity 90 m 3 / (m 2 ·h), water flushing intensity 15m 3 / (m 2 •h); Water flush alone for 10 minutes, water flushing intensity 15m 3 / (m 2 ·h), the rinsing frequency is 4 times / month.

[0068] In this embodiment, the ecological pond 130 is covered with a 30cm thick layer of ordinary planting soil 133. The submerged plants 132 are Vallisneria natans, Myriophyllum spicatum, Hydrilla verticillata, Potamogeton malaianus, and Potamogeton crispus, with a planting area ratio of 1:1:1:1:2 and a planting density of 100 plants / m². 2 The total coverage is 70%; emergent plant 131 is iris, which is planted in 30% of the water area at a density of 25 plants / m². 2 Filter-feeding fish include silver carp and bighead carp, with a stocking size of 150-200g / fish, a stocking ratio of silver carp to bighead carp of 3:2, and a stocking density of 50g / m³. 3 Benthic animals included *Bellamya affinis* and *Cyprinus triangularis*, with a stocking ratio of 1:1 and a stocking density of 200 g / m³. 2The release area covers 10% of the surface area of ​​the ecological pond. The water depth of the ecological pond is 2.0m, and the retention time is 1.2 days.

[0069] In this embodiment, the inlet zone 141 of the horizontal subsurface flow wetland 140 is 1.0m long and filled with gravel with a particle size of 4.0-6.0cm; the outlet zone 143 is 1.0m long and filled with gravel with a particle size of 4.0-6.0cm; the main zone 142 is filled with volcanic rock with a particle size of 1.0-3.0cm; the wetland plants selected are canna lilies and irises, with a planting density of 25 plants / m². 2 The effective depth of the wetland is 1.6m, the residence time is 0.72d, and the hydraulic loading is 0.9m. 3 / (m 2 ·d).

[0070] In this embodiment, after two months of monitoring the operation of treatment system 100, the COD content in the effluent of the wastewater treatment plant was 25.05-71.36 mg / L, and the TN (total nitrogen) content was 3.69-10.47 mg / L. The COD content of the effluent from activated carbon reactor 110 was 3.35-22.78 mg / L, with a COD removal rate of 61.80%-90.82%; the COD content of the effluent from horizontal subsurface flow wetland 140 was 2.00-10.45 mg / L, with a COD removal rate of 77.23%-94.09%. The TN content of the effluent from denitrification reactor 120 was 0.74-6.19 mg / L, with a TN removal rate of 37.94%-82.79%; the TN content of the effluent from horizontal subsurface flow wetland 140 was 0.68-4.79 mg / L, with a TN removal rate of 50.00%-86.71%.

[0071] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A wastewater treatment system for wastewater treatment plants, applied to wastewater generated by wastewater treatment plants using ozone advanced oxidation technology, characterized in that, include: An activated carbon reactor is connected to a tailwater pipe. The activated carbon reactor includes an activated carbon filter layer, which adsorbs the chemical oxygen demand and dissolved oxygen in the tailwater. A denitrification reactor is connected to the activated carbon reactor. The denitrification reactor includes the denitrification filter layer, which is used for autotrophic denitrification of effluent. An ecological pond is connected to the denitrification reactor, and the ecological pond includes aquatic plants and aquatic animals; A horizontal subsurface flow wetland is connected to the ecological pond, and the horizontal subsurface flow wetland is used for deep filtration of the wastewater.

2. The wastewater treatment system according to claim 1, characterized in that, The bottom of the activated carbon reactor is connected to the tailwater pipe, the top of the activated carbon reactor is connected to the top of the denitrification reactor, and the bottom of the denitrification reactor is connected to the ecological pond.

3. The wastewater treatment system according to claim 2, characterized in that, The liquid level in the activated carbon reactor is higher than the liquid level in the denitrification reactor, and the height difference between the two liquid levels is less than 30 cm.

4. The wastewater treatment system according to claim 1, characterized in that, The top of the activated carbon reactor is connected to the tailwater pipe, the bottom of the activated carbon reactor is connected to the bottom of the denitrification reactor, and the top of the denitrification reactor is connected to the ecological pond.

5. The wastewater treatment system for wastewater treatment plants according to any one of claims 1-4, characterized in that, The activated carbon reactor and the denitrification reactor are respectively equipped with water and gas distribution plates for support. The water and gas distribution plates are annular and have multiple round holes evenly arranged. The diameter of the round holes satisfies 3mm≤a≤5mm.

6. The wastewater treatment system according to claim 5, characterized in that, The activated carbon filter layer includes granular activated carbon and / or columnar activated carbon.

7. The wastewater treatment system according to claim 5, characterized in that, The activated carbon reaction device is provided with a first backwash pipe at the bottom and a first backwash pump connected to the first backwash pipe; The denitrification reactor is equipped with a second backwash pipe located at the bottom and a second backwash pump connected to the second backwash pipe.

8. The wastewater treatment system for wastewater treatment plants according to any one of claims 1-4, characterized in that, The aquatic plants include at least three of the following: Vallisneria natans, Myriophyllum spicatum, Hydrilla verticillata, Ceratophyllum demersum, Potamogeton malaianum, Potamogeton microdentula, Potamogeton pectinatus, and Potamogeton crispus.

9. The wastewater treatment system for wastewater treatment plants according to any one of claims 1-4, characterized in that, The horizontal subsurface flow wetland comprises an inlet zone, a main zone, and an outlet zone, wherein the particle size of the inlet zone and the outlet zone is larger than that of the main zone.

10. A method for treating wastewater effluent from a wastewater treatment plant, applied to the wastewater effluent treatment system described in any one of claims 1-9, characterized in that, The processing method includes: When the treatment system is started, the wastewater enters the activated carbon reactor through the wastewater pipe. The filtration rate of the activated carbon reactor is 1.275 m / h-3.5 m / h, and the wastewater retention time is 35 min-98 min. The effluent leaves the activated carbon reactor and enters the denitrification reactor, which has a filtration rate of 2.12 m / h-5.94 m / h and a effluent retention time of 21 min-60 min. The effluent leaves the denitrification reactor and enters the ecological pond, where it remains for 1-2 days. The tailwater leaves the ecological pond and enters the horizontal subsurface flow wetland, where it remains for 0.5 to 1 day.

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