Multi-stage coupling membrane method urban sewage treatment device

Abstract

The utility model relates to a multi-stage coupling membrane method urban sewage treatment device, and belongs to the technical field of water treatment. The multi-stage coupling membrane method urban sewage treatment device comprises a sedimentation tank used for carrying out sedimentation treatment on municipal wastewater; the air floatation tank is connected to the sedimentation tank and is used for carrying out air floatation treatment on clear liquid in the sedimentation tank; the ozone aeration tank is connected to a water production port of the air floatation tank and is used for carrying out ozone oxidation treatment on produced water; the ceramic membrane is connected to a water production port of the ozone aeration tank and is used for filtering produced water; and the hollow fiber nanofiltration membrane is connected to the permeation side of the ceramic membrane and is used for carrying out nanofiltration treatment on the produced water to obtain purified water.

Description

Technical Field

[0001] This utility model relates to a multi-stage coupled membrane method urban sewage treatment device, belonging to the field of water treatment technology. Background Technology

[0002] With rapid industrialization and urbanization, China's tap water treatment faces unprecedented challenges. Traditional tap water treatment processes are no longer sufficient to meet the ever-increasing demands for water quality safety. Therefore, the development and application of new and efficient water treatment technologies are particularly important. Against this backdrop, dissolved air flotation (DAF) / sedimentation tank technology has regained attention due to its highly efficient solid-liquid separation capabilities. This technology removes suspended solids by injecting microbubbles into the water, causing them to adhere to the bubbles and float rapidly. Compared to traditional sedimentation tanks, DAF technology offers advantages such as faster processing speed, smaller footprint, and simpler operation.

[0003] Traditional air flotation technology does have some limitations in water treatment. These limitations may lead to high treatment loads in subsequent water treatment processes and may cause membrane fouling when using ceramic membranes. These limitations include the following aspects:

[0004] Limited pollutant removal efficiency: Traditional air flotation technology mainly relies on physical methods, injecting air into the water to form bubbles, causing pollutants to adhere to the bubbles and float to the surface for removal. This method is effective for some pollutants, especially hydrophobic suspended solids and destabilized colloidal particles, but its removal efficiency is not high for other types of pollutants, such as dissolved organic matter and certain heavy metal ions.

[0005] High treatment load: Because traditional air flotation technology cannot effectively remove all types of pollutants, subsequent water treatment processes need to withstand a greater treatment load to ensure that the water quality meets discharge standards. This not only increases treatment costs but may also lead to reduced treatment efficiency.

[0006] Membrane fouling: When ceramic membranes are used for subsequent treatment, if the flotation process is insufficient, unremoved contaminants will directly contact the ceramic membrane surface, leading to membrane fouling. Membrane fouling reduces membrane filtration efficiency, increases the frequency of membrane cleaning and replacement, and thus increases operating costs.

[0007] Maintenance and cleaning of ceramic membranes: Although inorganic ceramic membranes have advantages such as high temperature resistance and corrosion resistance, if air flotation is insufficient during treatment, pollutants will accumulate on the membrane surface, leading to a decrease in membrane flux. This requires periodic chemical cleaning or physical scraping to restore membrane performance, but these operations increase maintenance costs and operational complexity.

[0008] The stability and reliability of dissolved air flotation (DAF) equipment are crucial to the entire water treatment process. Frequent malfunctions, such as insufficient pump head or clogged release devices, will directly impact the flotation effect, consequently affecting the effectiveness of subsequent ceramic membrane treatment. Summary of the Invention

[0009] This invention relates to a process combining an air flotation / sedimentation tank with membrane aeration (ozone) and inorganic ceramic membranes and hollow fiber nanofiltration membranes. First, the wastewater undergoes preliminary solid-liquid separation in the air flotation / sedimentation tank, removing suspended solids and some organic matter. Then, the wastewater enters the membrane aeration (ozone) system, where the strong oxidizing properties of ozone further degrade organic matter, improving water quality. The inorganic ceramic membrane, as the next stage of filtration, effectively traps particles and bacteria during filtration due to its small pore size, high temperature resistance, and corrosion resistance, ensuring the cleanliness of the effluent. Finally, the hollow fiber nanofiltration membrane performs advanced treatment, further removing dissolved organic matter and inorganic salts to ensure the effluent meets higher water quality standards. The modular design of this technology combination provides excellent adaptability and flexibility for wastewater treatment projects of varying scales. Whether for industrial wastewater treatment or municipal sewage treatment, this technology offers an efficient and economical solution.

[0010] A multi-stage coupled membrane urban wastewater treatment device, comprising:

[0011] Sedimentation tanks are used for sedimentation treatment of municipal wastewater.

[0012] An air flotation tank, connected to a sedimentation tank, is used to treat the clarified liquid in the sedimentation tank by air flotation.

[0013] The ozone aeration tank is connected to the product water outlet of the dissolved air flotation tank and is used to treat the product water with ozone oxidation.

[0014] A ceramic membrane is connected to the product water outlet of the ozone aeration tank to filter the product water.

[0015] Hollow fiber nanofiltration membranes, connected to the permeate side of ceramic membranes, are used to nanofiltration process permeate water to obtain purified water.

[0016] In the hollow fiber nanofiltration membrane assembly, hollow fiber membrane filaments are used, and the diameter of the membrane filaments ranges from 0.5 to 3 mm.

[0017] The hollow fiber nanofiltration membrane has a 90% rejection rate for 1000 ppm MgSO4 solution and a 90% rejection rate for 200 ppm PEG400 solution.

[0018] The ceramic membrane is an ultrafiltration membrane or a microfiltration membrane.

[0019] The ceramic membrane is made of alumina, zirconium oxide, titanium oxide, silicon carbide, or silicon oxide.

[0020] The ceramic membrane has a pore size of 1-1200 nm.

[0021] The ceramic membrane has a pore size of 4-500 nm.

[0022] The ozone aeration tank is equipped with multiple aeration points at the bottom, which are arranged sequentially along the water flow direction.

[0023] The microporous aerators installed at the aeration points are plate-type, tubular-type, or disc-type, and their materials are titanium alloy, corundum, polytetrafluoroethylene, or ceramic.

[0024] The beneficial effects of this invention are as follows: It employs a multi-stage coupled membrane process integrating flotation / sedimentation tanks with membrane aeration (ozone), inorganic ceramic membranes, and hollow fiber nanofiltration membranes to improve both the quality and treatment efficiency of tap water. The process first removes suspended solids and some organic matter through a flotation / flocculation tank. Then, oxygen is introduced using membrane aeration technology, further degrading harmful substances such as ammonia nitrogen and organic matter through oxidation. Next, the microporous structure of the inorganic ceramic membrane effectively traps remaining suspended particles and large organic molecules, ensuring the clarity of the effluent. Finally, the nanoscale filtration capability of the hollow fiber nanofiltration membrane ensures the purity of the final effluent, meeting or even exceeding tap water standards. This process exhibits good adaptability and can treat raw water from different sources and with varying degrees of pollution. Due to its modular design, the treatment scale can be flexibly adjusted according to actual needs. This multi-stage coupled membrane tap water treatment process is not only technologically innovative but also offers significant advantages in terms of economic and environmental benefits. It provides a new solution for improving tap water treatment efficiency and quality and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a flowchart of the patent;

[0026] Figure 2 This is a diagram of the device in this patent.

[0027] 1. Sedimentation tank; 2. Air flotation tank; 3. Ozone aeration tank; 4. Ceramic membrane; 5. Hollow fiber nanofiltration membrane. Detailed Implementation

[0028] This utility model relates to a process combining an air flotation / sedimentation tank with membrane aeration (ozone) and inorganic ceramic membranes and hollow fiber nanofiltration membranes. Membrane aeration (ozone) technology further enhances water treatment efficiency based on air flotation tanks. Through the strong oxidizing properties of ozone, organic matter, bacteria, and viruses in water can be effectively removed. Simultaneously, the oxygen produced after ozone decomposition increases the dissolved oxygen content in the water, improving the aquatic environment. The application of inorganic ceramic membranes and hollow fiber nanofiltration membranes provides a more refined filtration method for tap water treatment. Inorganic ceramic membranes possess characteristics such as high temperature resistance, corrosion resistance, and resistance to microbial erosion, effectively trapping particles, bacteria, and viruses in water. Hollow fiber nanofiltration membranes excel in removing dissolved organic matter and heavy metal ions from water, further ensuring the safety of drinking water.

[0029] The wastewater to be treated by this invention originates from urban domestic sewage. In a typical embodiment, the influent water quality is as follows:

[0030] Influent water quality BOD5 / mg / L COD / mg / L SS / mg / L NH3-N / mg / L numerical values 100-200 150-300 100-300 15-30

[0031] The multi-stage coupled membrane method for tap water treatment of this utility model mainly includes the following steps:

[0032] Step 1, the air flotation / sedimentation tank, introduces microbubbles to cause suspended particles in the wastewater to float or settle, thus initially separating solids and liquids.

[0033] Step 2: Membrane aeration (ozone) technology utilizes the strong oxidizing properties of ozone to further decompose organic pollutants in the water, improving the biodegradability of the water. Microporous aerators can be plate, tubular, or disc types. The materials of the microporous aerator and its fixing components should be resistant to ozone corrosion; materials for the aerator can include titanium alloy, corundum, polytetrafluoroethylene, and ceramics.

[0034] Step 3: Next, the inorganic ceramic membrane filters effectively removes particles and bacteria from the water, ensuring the cleanliness of the output water.

[0035] In step 4, the hollow fiber nanofiltration membrane, with its unique nanoscale filtration capability, can remove dissolved organic matter, viruses, and some salts from the water, ensuring that the final effluent meets or even exceeds tap water standards.

[0036] In the air flotation process described in step 1, flocculant is first added to generate precipitate, and tiny bubbles are generated by an air compressor.

[0037] In step 2, oxygen is introduced into the wastewater through the micropores of the membrane to oxidize and degrade harmful substances and remove ammonia nitrogen and organic matter.

[0038] The filtration in step 3 uses a ceramic membrane. The pore size of the ceramic membrane is 1-1200 nm, preferably 4-500 nm; the feed temperature during the ceramic membrane filtration process is 5-80℃; the pressure is 0.1-0.5 MPa; the membrane surface flow rate is 2-5 m / s; and the concentration factor is 1-30 times.

[0039] The retentate obtained from the ultrafiltration membrane in step 4 is sent back to step 4 for further filtration.

[0040] The nanofiltration membrane is a hollow fiber nanofiltration membrane made of organic material, with a molecular weight cutoff of 100-1000 Da and a filtration pressure of 0.4-4.0 MPa.

[0041] The multi-stage coupled membrane method for urban wastewater treatment provided by this utility model, such as Figure 2 As shown, it includes:

[0042] Sedimentation tank 1 is used for sedimentation treatment of municipal wastewater;

[0043] Flotation tank 2 is connected to sedimentation tank 1 and is used to perform flotation treatment on the clear liquid in sedimentation tank.

[0044] Ozone aeration tank 3 is connected to the product water outlet of the flotation tank and is used to treat the product water with ozone oxidation.

[0045] Ceramic membrane 4 is connected to the water outlet of ozone aeration tank 3 and is used to filter the water.

[0046] Hollow fiber nanofiltration membrane 5 is connected to the permeate side of ceramic membrane 4 and is used to perform nanofiltration treatment on the product water to obtain purified water.

[0047] In the hollow fiber nanofiltration membrane 5, the membrane fibers are in the form of hollow fibers, and the diameter of the membrane fibers ranges from 0.5 to 3 mm.

[0048] The hollow fiber nanofiltration membrane 5 has a 90% rejection rate for 1000 ppm MgSO4 solution and a 90% rejection rate for 200 ppm PEG400 solution.

[0049] The ceramic membrane 4 is an ultrafiltration membrane or a microfiltration membrane.

[0050] The ceramic film 4 is made of alumina, zirconium oxide, titanium oxide, silicon carbide, or silicon oxide.

[0051] The ceramic membrane has a pore size of 1-1200 nm.

[0052] The ceramic membrane has a pore size of 4-500 nm.

[0053] The ozone aeration tank 3 is equipped with multiple aeration points at its bottom, which are arranged sequentially along the water flow direction.

[0054] The microporous aerators installed at the aeration points are plate-type, tubular-type, or disc-type, and their materials are titanium alloy, corundum, polytetrafluoroethylene, or ceramic.

[0055] Example 1

[0056] The processing method used is detailed below:

[0057] Influent water quality BOD5 / mg / L COD / mg / L SS / mg / L <![CDATA[NH3-N / mg / L]]> numerical values 125-132 167-174 176-192 17-19

[0058] Step 1: The raw water is introduced into the primary sedimentation tank to initially remove larger solid particles, thereby reducing the load on subsequent treatment and improving treatment efficiency;

[0059] Step 2: Bubbles are introduced into the bottom of the solution. The gas-liquid interface of the bubbles is used to remove hydrophobic and amphoteric substances from the liquid. The surface bubbles are then removed by a mechanical skimmer, thus achieving solid-liquid or liquid-liquid separation. The dissolved gas pressure is between 0.4 MPa. When the dissolved gas pressure is below 0.3 MPa, the amount of microbubbles generated is small, the dissolved gas effect is poor, and the air flotation effect is affected. When the dissolved gas pressure is too high, a higher head of the reflux pump is required, which leads to increased energy consumption. The reflux ratio is 20%.

[0060] Step 3: The supernatant from the dissolved oxygen flotation tank is transferred to the membrane aeration tank. The ozone dosage is controlled at 10-12 mg / L. Aeration not only increases the dissolved oxygen concentration but also promotes microbial activity, while simultaneously slowing down membrane fouling. Membrane aeration can degrade and remove recalcitrant organic matter. The membrane aeration system uses a three-point series dosing system. The first dosing point distributes 50-55% of the total gas volume, while the second and third points distribute the ozone proportionally.

[0061] Step 4: The supernatant in the membrane aeration tank enters the ultrafiltration membrane module, where it passes through the ultrafiltration membrane system to remove impurities such as macromolecular organic matter, suspended solids, and microorganisms. The ultrafiltration process uses a pressure range of 0.3 MPa, the ultrafiltration membrane has an average pore size of 0.05 μm, and the membrane material is ZrO2.

[0062] Step 5: The water produced by the ceramic ultrafiltration membrane module is fed into the hollow fiber nanofiltration membrane module. In the hollow fiber nanofiltration membrane module, the water passes through the microporous hollow fiber membrane, further removing dissolved organic matter and some inorganic salts. Nanofiltration membranes have a high molecular weight cutoff, effectively retaining divalent ions and some monovalent ions in the water, while allowing water molecules and some small molecules to pass through. The hollow fiber nanofiltration membrane has a 90% rejection rate for 1000 ppm MgSO4 solution and a 90% rejection rate for 200 ppm PEG400 solution.

[0063] Operating conditions for nanofiltration membrane: 6.9 bar.

[0064] The obtained water quality data for the treated wastewater, or the data on the retention rate of major pollutants.

[0065] effluent water quality BOD5 / mg / L COD / mg / L SS / mg / L NH3-N / mg / L pH ≤8.7 ≤8.3 ≤6.8 ≤10.2 7.2

Claims

1. A multi-stage coupled membrane urban wastewater treatment device, characterized in that, include: Sedimentation tank (1) is used for sedimentation treatment of municipal wastewater; The flotation tank (2) is connected to the sedimentation tank (1) and is used to perform flotation treatment on the clear liquid in the sedimentation tank. Ozone aeration tank (3) is connected to the water outlet of the flotation tank and is used to treat the water by ozone oxidation. A ceramic membrane (4) is connected to the water outlet of the ozone aeration tank (3) for filtering the water. Hollow fiber nanofiltration membrane (5) is connected to the permeate side of ceramic membrane (4) and is used to perform nanofiltration treatment on the product water to obtain purified water.

2. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, In the hollow fiber nanofiltration membrane (5) assembly, hollow fiber membrane filaments are used, and the diameter of the membrane filaments ranges from 0.5 to 3 mm.

3. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The ceramic membrane (4) is an ultrafiltration membrane or a microfiltration membrane.

4. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The ceramic film (4) is made of alumina, zirconium oxide, titanium oxide, silicon carbide or silicon oxide.

5. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The ceramic membrane has a pore size of 1-1200 nm.

6. The multi-stage coupled membrane urban wastewater treatment device according to claim 5, characterized in that, The ceramic membrane has a pore size of 4-500 nm.

7. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The ozone aeration tank (3) is equipped with multiple aeration points at the bottom, which are arranged sequentially along the water flow direction.

8. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The microporous aerators installed at the aeration points can be plate-type, tube-type, or disc-type.

9. The multi-stage coupled membrane urban wastewater treatment device according to claim 1, characterized in that, The materials used for microporous aerators are titanium alloy, corundum, polytetrafluoroethylene, or ceramic.

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