A method and device for treating sewage using algae membrane combined with ultrafiltration membrane

Abstract

The present invention discloses a method and device for treating sewage by using algae membrane combined with ultrafiltration membrane. The method utilizes the photosynthesis and respiration of algae to treat sewage alternately, removing nitrogen and phosphorus in the sewage; then utilizes flocculants to remove suspended algae precipitation in the effluent, and then uses ultrafiltration membranes to further separate suspended matter and water, thereby improving the effluent quality. The device is connected in sequence by a raw water tank, a tubular algae membrane system, an ultrafiltration membrane system, and an effluent water tank according to the direction of water flow; the tubular algae membrane system is connected alternately by a light-transmitting tubular reactor and a light-impermeable tubular reactor, wherein an algae membrane can be arranged in the light-transmitting tubular reactor; the ultrafiltration membrane system is composed of a dosing device, a sedimentation tank, and an ultrafiltration membrane assembly. The device of the present invention is used to treat sewage according to the method of the present invention, so that sewage can be treated continuously, efficiently, and with high quality, and the degree of automation and equipment utilization are high.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a method and a device for treating sewage by utilizing an algae membrane in combination with an ultrafiltration membrane. Background Art

[0002] With the intensification of my country's urbanization process, the discharge and generation of urban sewage are increasing day by day, and the operating load of urban sewage treatment plants is also increasing. In recent years, many domestic sewage treatment plants have been carrying out new construction, expansion and upgrading to increase the sewage treatment capacity and effluent quality, reduce the pollution of sewage to the water environment, especially the eutrophication of water bodies caused by nitrogen and phosphorus pollutants in sewage. In the process of algae using light energy for photosynthesis, it can effectively absorb nutrients such as nitrogen and phosphorus in water and generate its own substances. Based on this feature, algae has a good application prospect in the field of sewage treatment and water environment management. A large number of studies have shown that algae has a significant effect on the removal of nitrogen, phosphorus and other nutrients in domestic sewage, industrial sewage, agricultural sewage and other sewage. Therefore, an algae sewage treatment system that can achieve deep treatment of nitrogen and phosphorus in sewage and nutrient reuse will be an attractive technology.

[0003] Algae membrane is formed by combining algae with carriers. Domestic and foreign research results show that using it for sewage treatment can more effectively remove pollutants, especially nitrogen and phosphorus pollutants, compared with traditional sewage treatment technology. At the same time, it can produce algae biomass products. The use of algae resource technology can obtain higher economic benefits and reduce sewage treatment costs. Christenson et al. (Christenson Logan B, Sims Ronald C, Biotechnology and Bioengineering, 2012, 109 (7): 1674-1684) designed a rotating photobioreactor for wastewater integrated treatment based on blue-green algae biofilm for simultaneous carbon removal, nitrogen removal and phosphorus removal. Under high nutrient load, the removal rates of COD, nitrate and phosphate can reach 65.68%, 79.17% and 91.64% respectively. Gao et al. (Gao, F., Yang, ZH, Li, C. et al, Bioresource Technology, 2015, 179: 8-12) developed a new algae biofilm treatment technology (BMPBR) with solid carriers and immersed membrane components for attached growth of Chlorella and secondary effluent treatment. The experimental results showed that the new algae biofilm treatment technology (BMPBR) has a more stable denitrification effect and a higher algae biomass than the suspended growth membrane photobioreactor (MPBR).

[0004] The application of algae in sewage treatment has been developed for decades, and the treatment forms include high-efficiency algae ponds, biological stabilization ponds, hydraulic algae beds, algae photobioreactors and immobilized algae systems. Because the growth and reproduction of algae are easily affected by external environmental factors such as temperature, pH, and light, the large-scale, industrialized cultivation and engineering application of algae are restricted by algae cultivation technology and bioreactors. According to existing research, the design principles of algae photobioreactors are: full utilization of light energy, good scalability, high mixing degree, and controllable operating conditions. In fact, various types of photobioreactors (PBRs) have been well developed in recent years, mainly divided into open and closed light cultivation systems. The two cultivation systems have their own advantages and disadvantages. The open system has low investment, low cost, and simple technology, but it is easily affected by the external environment. The closed system has good controllability, but the engineering cost is high and it is difficult to scale up the cultivation. In recent years, ultrafiltration membrane technology has also been studied in the field of algae-water separation. The research mainly focuses on the pretreatment process and membrane fouling characteristics. To use ultrafiltration membrane technology for algae-water separation in actual projects, it is necessary to comprehensively consider aspects such as membrane fouling, water production and energy consumption. At present, the research on algae membranes is more inclined to the removal of new pollutants and the optimization of reactor structure. The research on ultrafiltration membrane algae-water separation is mainly focused on membrane fouling characteristics and control. There are few studies on combining the two technologies of algae membrane removal of pollutants and ultrafiltration membrane algae-water separation to form a complete sewage treatment system. The development of an algae membrane-ultrafiltration membrane sewage treatment device that can be put into actual sewage treatment applications is of great significance to the development of algae membrane sewage treatment technology.

[0005] The research group led by Wei Qun, the first inventor of this application, has been engaged in the research of algae / algae membrane denitrification and phosphorus removal. In his master's thesis "Experimental Study on Wastewater Treatment with Mixed Algae and Algae Membranes", Sun Hongyun studied the effects of freshwater algae species, algae membrane carriers, added organic carbon sources and light-dark ratio on the denitrification and phosphorus removal effects of algae membranes. In his master's thesis "Experimental Study on Wastewater Denitrification and Phosphorus Removal with a New Algae Membrane Process System", Chen Yanfei proposed to construct an algae membrane process system consisting of an inlet (raw) water tank, a peristaltic pump, an algae membrane reactor, an inclined plate sedimentation tank, an ultrafiltration membrane device and an outlet water tank, and to use an algae biofilm and ultrafiltration membrane double membrane system to treat domestic sewage and improve the water quality of the effluent. Patent CN201310380921.0 proposed by the applicant discloses a method for deep treatment of wastewater denitrification and phosphorus removal, which mainly includes pretreatment, algae membrane bioreactor treatment, inclined plate sedimentation tank treatment and membrane filtration treatment. The sewage is first pretreated, and then enters the algae membrane bioreactor to efficiently remove nitrogen and phosphorus from the sewage, and then enters the inclined plate sedimentation tank to precipitate the suspended matter to prevent clogging of the subsequent filter membrane. Finally, the sewage is filtered through the membrane assembly, and the filtrate is stored in the permeate water pool for reuse. However, the algae membrane reactor disclosed in the paper "Experimental Study on Sewage Nitrogen and Phosphorus Removal in a New Algae Membrane Process System" and the algae membrane bioreactor disclosed in patent CN201310380921.0 are both composed of reactors equipped with algae membranes in series, and the sewage is treated under room temperature and continuous light conditions of 3000-4500lx. The algae grows under light for a long time, matures and ages quickly, the algae membrane has a short service life, and the secondary pollution caused by algae corruption is serious; the light energy consumption is high and the detached algae need to be treated frequently. In addition, the algae membrane process system disclosed in the paper "Experimental Study on Wastewater Nitrogen and Phosphorus Removal by a New Algae Membrane Process System" has a good decontamination effect in the laboratory test stage, but when it is put into actual sewage treatment, the decontamination effect is reduced. There are many suspended algae in the effluent of the algae membrane reactor, which is easy to clog the ultrafiltration membrane. Therefore, the algae membrane process system is currently only in the laboratory test stage. Therefore, how to improve the algae membrane process system and its sewage treatment process to improve the efficiency and capacity of the algae membrane process system in actual operation and the effluent water quality is still our current research direction. Summary of the invention

[0006] The purpose of the present invention is a method and device for treating sewage using algae membrane combined with ultrafiltration membrane. The device of the present invention is used to treat sewage according to the method of the present invention, which can achieve continuous, efficient and high-quality sewage treatment with a high degree of automation and high equipment utilization.

[0007] The technical solution of the present invention is as follows:

[0008] A method for treating sewage using an algae membrane combined with an ultrafiltration membrane comprises the following steps:

[0009] (1) Cultivating algae membranes.

[0010] (2) The sewage to be treated is first stored in a raw water tank, and the pH value is adjusted by adding acid solution or alkaline solution. At the same time, gravity is used to precipitate the heavy objects in the sewage.

[0011] (3) At room temperature, the sewage in the raw water tank is sent to a reactor equipped with an algae membrane. The sewage is treated for 4-48 hours under a light intensity of 3000-100000 lux, and the nitrogen and phosphorus in the sewage are removed by the photosynthesis of algae cells. Subsequently, the sewage and the detached suspended algae are discharged into a reactor without an algae membrane and treated for 1-48 hours in the dark. The respiration of the suspended algae is used to remove the nitrogen and phosphorus in the sewage and consume the dissolved oxygen in the sewage.

[0012] (4) The sewage and suspended algae in the reactor without algae membrane are discharged into another reactor equipped with algae membrane, and the sewage is treated for 4-48 hours under the condition of light intensity of 3000-100000 lux; then, the sewage and the detached suspended algae are discharged into another reactor without algae membrane and treated for 1-48 hours under dark conditions.

[0013] (5) Alternately connect several reactors equipped with algae membranes and reactors without algae membranes, and repeat step (4) several times until the COD, TP, TN and NH4 in the sewage are + -N meets the water outlet requirements.

[0014] (6) Sewage that meets the effluent requirements is discharged into a sedimentation tank, and flocculants are added to settle the suspended algae in the sewage. The supernatant in the sedimentation tank is then ultrafiltered using an ultrafiltration membrane to further separate the suspended matter and water, thereby achieving continuous, efficient, and high-quality sewage treatment.

[0015] A device for treating sewage using an algae membrane combined with an ultrafiltration membrane, which is connected in sequence by a raw water tank, a tubular algae membrane system, an ultrafiltration membrane system, and an outlet water tank according to the direction of water flow. The tubular algae membrane system is formed by alternately connecting a light-transmitting tubular reactor and an opaque tubular reactor, wherein an algae membrane can be arranged inside the light-transmitting tubular reactor. The ultrafiltration membrane system is composed of a dosing device, a sedimentation tank, and an ultrafiltration membrane assembly. The dosing device is arranged on a pipeline in front of the water inlet of the sedimentation tank, and the water outlet of the sedimentation tank is connected to the water inlet of the ultrafiltration membrane assembly, and liquid is pumped through the ultrafiltration pump in between.

[0016] The light-transmitting tubular reactor and the light-impermeable tubular reactor are both upright tubular reactors, and the tubular reactor is composed of a top circular end cover, a cylindrical part, and a conical part from top to bottom; the water inlet of the tubular reactor is arranged on one side below the cylindrical part, and the water outlet is arranged on the other side above the cylindrical part; a mud discharge port is arranged at the top of the conical part, and a valve is arranged at the mud discharge port, and the algae mud deposited at the bottom of the tubular reactor is cleaned by regularly opening the valve at the mud discharge port; the inclination angle of the cone is 30-60°. Valves are arranged on the water inlet and outlet pipes of the tubular reactor, and a vent pipe is also arranged on its outlet pipe. The lowest point of the vent pipe is higher than the liquid level in the tubular reactor, which can realize the connection between the air inside the tubular reactor and the atmosphere, so that the oxygen produced by the photosynthesis of the algae in the tubular reactor and the carbon dioxide produced by the respiration can be discharged from the tubular reactor. The vent pipe is preferably a curved vent pipe, and the curved pipe design can reduce the impact of external pollution on the operation of the device. The vent pipe is arranged on the water outlet pipe instead of on the tubular reactor, which is more conducive to reducing the impact of external pollution on the operation of the tubular reactor. In order to prevent the tubular reactor from overflowing from the vent pipe due to excessive water in the tubular reactor, the opening of the inlet and outlet valves must be strictly controlled, or a liquid leakage monitoring and alarm device must be installed on the vent pipe. Once water enters the vent pipe, the liquid leakage monitoring and alarm device will be triggered.

[0017] Inside the light-transmitting tubular reactor, the top circular end cap and the side wall of the cone are provided with fixings for the algae film, and the algae film is unfolded in the light-transmitting tubular reactor through the fixings and the algae film is detachable relative to the light-transmitting tubular reactor. The fixings can be structures of any shape, such as hook-shaped, ring-shaped, semi-ring-shaped, etc., as long as the algae film can be fixed and easily disassembled. The diameter of the light-transmitting tubular reactor is small, and a strip-shaped algae film carrier can be selected. The fixings for the algae film can be set at the center of the top circular end cap and the side wall of the cone near the mud discharge port.

[0018] The light-transmitting tubular reactor and the light-impermeable tubular reactor are fixedly placed by a fixing frame; a lighting lamp is arranged on the fixing frame to provide lighting conditions for photosynthesis of algae cells. The lighting lamp can adjust the light intensity.

[0019] The fixing frame has an inclined surface, and the angle between the inclined surface and the horizontal ground is 45-90 degrees. The light-transmitting tubular reactor is fixed above the inclined surface, and the light-opaque tubular reactor is fixed below the inclined surface. The inclined surface is set high and long according to the length, diameter and number of side-by-side tubular reactors, and is divided into several layers by long plates or long tubes in the height direction of the inclined surface. The long plates or long tubes are provided with several annular tube sleeves for fixing the tubular reactors. The lighting lamps are arranged around the upper and lower sides of the fixing frame, and can also be arranged on the long plates or long tubes in the middle of the inclined surface.

[0020] The dosing device is a fully automatic dosing device, which can adjust the dosing time and dosage of the flocculant according to the sewage flow rate and the pollutant concentration. The ultrafiltration membrane assembly is PLC fully automatic controlled, and the operation of the ultrafiltration membrane assembly can be adjusted according to the sewage flow rate. The ultrafiltration membrane assembly is any one of tubular ultrafiltration membrane, plate and frame ultrafiltration membrane, roll ultrafiltration membrane or hollow fiber ultrafiltration membrane, or a combination of two or more.

[0021] The water inlet of the sedimentation tank is arranged on one side above the sedimentation tank, and the water outlet is arranged on the other side above the sedimentation tank, and the water inlet is higher than the water outlet. A baffle is arranged near the water inlet in the sedimentation tank, and the lower end of the baffle is lower than the water outlet, so that the flocculated algae can directly reach the lower part of the sedimentation tank, thereby improving the sedimentation efficiency and avoiding affecting the water quality when the flow rate is large. The bottom of the sedimentation tank is a cone structure with an inclination angle of 30-60°. A mud discharge port is arranged at the top of the cone, and a valve is arranged at the mud discharge port. The algae mud deposited at the bottom of the sedimentation tank is cleaned by regularly opening the valve at the mud discharge port. The sedimentation tank can be circular or square.

[0022] The raw water tank and the outlet water tank can be round or square. A liquid delivery pump is provided between the outlet of the raw water tank and the inlet of the tubular algae membrane system, and liquid is delivered by the liquid delivery pump. The bottom of the raw water tank can also be set into a cone structure with an inclination angle of 30-60°. A mud discharge port is provided at the top of the cone, and a valve is provided at the mud discharge port. The pollutants deposited at the bottom of the raw water tank are cleaned by regularly opening the valve at the mud discharge port.

[0023] When the device is in operation, the sewage in the raw water tank is sent into the transparent tubular reactor of the tubular algae membrane system through the liquid delivery pump, and then comes out from the outlet of the last tubular reactor of the tubular algae membrane system, and enters the ultrafiltration membrane system from the water inlet of the sedimentation tank. Before the water inlet of the sedimentation tank, a dosing device is used to add flocculant into the water inlet pipe and mix it with water to improve the sedimentation efficiency of the algae. Then, the supernatant of the sedimentation tank is sent into the ultrafiltration membrane assembly through the ultrafiltration pump for ultrafiltration. The water coming out from the outlet of the ultrafiltration membrane assembly is stored in the outlet tank. After passing the test, it can be discharged or used in industrial and agricultural production.

[0024] The algae membrane is formed by combining algae with a carrier, and can be directly cultured and formed in a reactor (such as the above-mentioned light-transmitting tubular reactor) equipped with the algae membrane, or can be cultured and formed in other devices in advance and then transferred into the reactor (such as the above-mentioned light-transmitting tubular reactor) equipped with the algae membrane. The culture of the algae membrane includes pre-treatment of the carrier, algae membrane formation, and algae membrane acclimation, and the specific steps are as follows:

[0025] (1) Pretreatment of the carrier: soak the carrier in a 0.05-1.5 mol / L NaHCO3 solution for 23-25 ​​h, rinse it with deionized water 3-5 times, soak the obtained carrier in a 0.05-2.0 mol / L hydrochloric acid solution for 6-14 h, rinse it with deionized water 3-5 times and install it in the culture device after drying.

[0026] (2) Algae biofilm formation: Add BG11 culture medium into the culture device, inoculate algae into the culture medium at an initial concentration of 0.1-5 g / L, mix well and culture statically until algae biofilm formation is basically complete.

[0027] (3) Algae membrane acclimation: The wastewater to be treated is introduced into the culture device at a flow rate set according to the hydraulic retention time, and the culture medium in the culture device is replaced in equal amounts until the culture medium is completely replaced. This completes the acclimation of the algae membrane and can begin to treat the wastewater.

[0028] Cultivating algae film directly in a light-transmitting tubular reactor means installing the carrier in the light-transmitting tubular reactor, and performing film formation and domestication in the light-transmitting tubular reactor. Cultivating algae film directly in a light-transmitting tubular reactor is easier to operate, and the domesticated algae film can immediately treat sewage with high efficiency, but because the cultivation and domestication time is long, the entire sewage treatment device needs to stop operating for 10-15 days. The algae film is cultivated and formed in other devices in advance and then moved into the light-transmitting tubular reactor. It means installing the carrier in other devices, performing film formation and domestication, and moving the domesticated algae film into the light-transmitting tubular reactor; or installing the carrier in other devices, performing film formation, and moving the algae film into the light-transmitting tubular reactor for domestication after the film formation is completed. The algae film is cultivated and formed in other devices in advance and then moved into the light-transmitting tubular reactor, which can save the cultivation and domestication time of the algae film, and the operation of the entire sewage treatment device can be restored in a short time.

[0029] The flocculant is one or more of polyaluminium chloride (PAC), polyaluminium ferric chloride (PAFC), polyaluminium ferric sulfate (PAFS), polyferric sulfate (PFS) and polyacrylamide (PAM).

[0030] The algae species are not limited, and may be one or more of Oedogonium sp, Anabaena flos-aquae, Chlorella pyrenoidosa, Scenedesmus obliquus, Hydrodictyon reticulatum, and Oscillatoria agardhii.

[0031] The scaly algae belongs to the order Scalyalgae of the Chlorophyta, and can be subdivided into the genera of Cladoscelis, Scalyalgae, and Chaetoscelis. The mononuclear cells are cylindrical or obtuse in shape, and contain a large central vacuole and a reticulate chloroplast. They can reproduce sexually by egg-matching or asexually, producing zoospores with multiple flagella. The algae are filamentous and branched or unbranched, and can be suspended on the water surface or attached to the surface of other objects. They are mainly distributed in temperate and subtropical regions, and are one of the dominant algae species in eutrophication of lakes and reservoirs in my country.

[0032] Anabaena algae belongs to the Anabaena species of the family Nostoc, Cyanobacteria, Cyanobacteriales, Cyanobacteriaceae, and is filamentous in shape and emits a unique "fishy smell". The cells are waist-drum-shaped or spherical, with a length of 6-8μm and a width of 4-8μm. The algae filaments are single, and the entire algae filaments are straight, curved, and irregularly curved. They can exist alone or entangled in groups. They have good invasive ability and mostly live in freshwater environments. They are common floating species in lakes and ponds. They like to grow under higher temperature conditions and are prone to algae blooms in summer. They are one of the main algae species in eutrophic water bodies in my country.

[0033] Chlorella belongs to the genus Chlorella of the order Chlorococcales of the phylum Chlorophyta. It contains a distinct pyrenoid and is a single-celled organism. The cells are spherical, with thin cell walls and a diameter of about 3-5μm. It has strong reproductive capacity and high nutritional and economic value. It can be used to make various natural health products and is one of the main algae species in eutrophic water bodies.

[0034] Scenedesmus obliquus belongs to the genus Scenedesmus of the family Scenedesmus of the order Chlorococcophorales, Chlorophyta, and has cells that are spherical, oval, spindle-shaped, crescent-shaped, etc., containing single-plate chloroplasts and nuclei; with a smooth surface or a few small protrusions on the cell wall. The algae reproduces by producing spores, and has the advantages of fast reproduction, strong adaptability, and rich nutrition, and has good application prospects in the fields of sewage treatment, feed, food, and energy products.

[0035] Hydronet algae is a large colony of green algae, belonging to the order of true aggregates of the order of Chlorophyta, Chlorophyceae, Chlorococcales, and large net-like or net-like algae. Its cystic net is composed of cylindrical or broadly oval cells connected at both ends. When young, it has one pyrenoid, one nucleus, and flaky chromatophores; when grown up, it has multiple pyrenoids, multiple nuclei, and reticular chromatophores. The cells are cylindrical, bright yellow-green, up to 200μm wide and 1cm long. The meshes are mostly pentagonal or hexagonal, visible to the naked eye. The cells are long and scutellaria, and each mesh consists of 4-6 cells. It absorbs ammonia nitrogen, nitric nitrogen, and phosphate ions, with a removal rate of about 30%-80%.

[0036] Oscillatoria australis is a common oscillator algae belonging to the cyanobacteria class of the phylum Cyanobacteria. The algae have single or multiple filaments accumulated into bundles or tubes, mostly floating on the surface of water bodies. The cells are square, 4-6μm wide, 2.5-4μm long, 4μm long, with particles on both sides of the cell wall, pseudo-vacuoles in the contents, and the terminal cells are sometimes cap-shaped. It is commonly found in freshwater bodies, such as wells, wet soil surfaces, rock surfaces, rice fields, ditches, ponds, lakes, swamps, streams, rivers, and seashores.

[0037] The carrier is a three-dimensional elastic carrier, a semi-soft carrier or a soft carrier, etc.

[0038] The basic material of the soft carrier is acidified cellulose, which is processed according to the shape of natural aquatic plants. It has the advantages of large specific surface area, high utilization rate, variable and non-clogging gaps, wide application range and low cost.

[0039] The semi-soft carrier is made of polypropylene and polyethylene in the shape of snowflakes and connected by plastic ropes. It has the advantages of high heat dissipation performance, low resistance, good water and air distribution performance, easy film growth, and bubble cutting effect.

[0040] The three-dimensional elastic carrier is made of several high-quality fillers of polyolefins and polyamides that are resistant to corrosion, high temperature and aging, mixed with hydrophilic, adsorbent and heat-resistant additives, and made by special wire drawing and thread wool making process. The threads are interlaced and fixed on the corrosion-resistant and high-strength central rope in a radiating state, with moderate rigidity and flexibility. Its advantage is that the water and air distribution is uniform, and the biofilm can not only be evenly implanted on each thread, but also can fully contact and exchange with water and air, maintaining good activity and gap variability.

[0041] The device for treating sewage using algae membrane in combination with ultrafiltration membrane as described above is used to treat domestic sewage, industrial sewage, and agricultural sewage according to the method for treating sewage using algae membrane in combination with ultrafiltration membrane as described above, so as to achieve nitrogen and phosphorus removal from sewage. In fact, the algae membrane is installed in the light-transmitting tubular reactor as a reactor installed with the algae membrane, and the opaque tubular reactor is used as a reactor without the algae membrane, so as to provide a dark environment for sewage treatment under dark conditions, and the alternation of light and dark treatment is realized by controlling the water flow rate (hydraulic retention time) to control the time for the sewage to flow through each reactor.

[0042] The beneficial effects of the present invention are:

[0043] By adopting the sewage treatment method of the present invention, the sewage is continuously treated by using algae membranes under light conditions and suspended algae under dark conditions alternately. The algae cells on the algae membranes perform photosynthesis under light conditions, synthesize their own nutrients using organic matter in the sewage, and release oxygen. The suspended algae perform respiration under dark conditions, remove some pollutants in the sewage and consume part of the dissolved oxygen, alleviate the supersaturated oxygen inhibition in the next stage, and improve the photosynthesis efficiency of the algae cells in the next stage. By using the photosynthesis and respiration of algae cells to treat sewage alternately, the phenomenon of the photosynthesis of algae cells decreasing step by step when photosynthesis is performed continuously can be avoided. By adjusting the appropriate light-dark ratio, the photosynthesis and respiration of the algae cells promote each other, the decontamination effect is stronger, and the water quality of the effluent is better and more stable.

[0044] In order to realize the method of treating sewage by using algae membrane combined with ultrafiltration membrane in the present invention, the device for treating sewage by using algae membrane combined with ultrafiltration membrane is designed, which uses a tubular algae membrane system composed of light-transmitting tubular reactors and light-impermeable tubular reactors alternately connected and an ultrafiltration membrane system composed of a dosing device, a sedimentation tank, and an ultrafiltration membrane assembly to treat sewage. COD, TP, TN and NH4 in the sewage are removed in the tubular algae membrane system. +-N, and then the algae-water separation is carried out through the ultrafiltration membrane system, and the effluent quality is high. By alternately connecting the light-transmitting tubular reactor equipped with the algae membrane and the light-impermeable tubular reactor, the algae cells on the algae membrane can receive light conditions for 24 hours in the light-transmitting tubular reactor for photosynthesis, and the sewage treatment efficiency is high and the capacity is strong; the dead algae that fall off the algae membrane sink to the cone part of the tubular reactor and are discharged and cleaned up through the mud outlet; the suspended live algae that fall off the algae membrane reach the light-impermeable tubular reactor with the water flow, and breathe in the light-impermeable tubular reactor, removing some pollutants in the sewage and consuming dissolved oxygen, and the dead algae are further settled, separated and removed in the light-impermeable tubular reactor. Alternating the light-transmitting tubular reactor with the light-impermeable tubular reactor not only improves the utilization rate of live algae, but also can separate and remove dead algae in time with a high removal rate of dead algae. Compared with the existing algae membrane system (consisting of multiple identical algae membrane reactors connected in series), the cost of the light-transmitting tubular reactor is higher than that of the opaque tubular reactor. Under the same sewage treatment volume, the tubular algae membrane system of the invention is used for treatment, and the number of light-transmitting tubular reactors required is less, and the cost of the tubular algae membrane system is lower; when the number of light-transmitting tubular reactors is the same, the sewage treatment volume of the entire device is larger, and the sewage treatment volume can be increased by increasing the number of tubular reactors, and the continuity of sewage treatment is better. Moreover, the tubular algae membrane system of the present invention can be installed outdoors, and sunlight is used during the day to provide lighting conditions for the algae cells in the light-transmitting tubular reactor, which greatly saves the energy consumption required for providing lighting, and does not affect the life activities of the suspended algae in the opaque tubular reactor, so it does not affect the continuity of the effluent, and can achieve continuous treatment of sewage. The tubular reactor is a tubular, continuously operated reactor with a large aspect ratio, and belongs to a plug flow reactor. The use of a tubular reactor as an algae bioreactor provides a practical and feasible basis for the continuous treatment of sewage. Moreover, when the tubular algae membrane system of the present invention is used for sewage treatment, the water temperature in the tubular reactor changes more smoothly, which is more conducive to the growth of algae. In the light-transmitting tubular reactor, by utilizing the push-pull effect, the water quality of the algae cells at any point in the reactor and the sewage they contact is almost similar, and the algae cells have good growth adaptability, which can keep the photosynthesis in a relatively good state, avoiding the reduction of photosynthesis caused by the algae cells taking a certain amount of time to adapt to the environmental changes due to the different water quality they contact. A ventilation pipe is provided on the outlet pipe of the tubular reactor, so that the tubular reactor is a semi-open reactor, which is not polluted by dust, insects and miscellaneous bacteria, and can also be connected to the atmosphere to realize the exchange of CO2 and O2.

[0045] The present invention combines the two technologies of algae membrane pollutant removal and ultrafiltration membrane algae-water separation, and performs algae-water separation through a sedimentation tank and an ultrafiltration membrane. First, a flocculant is added to the sedimentation tank through a dosing device to allow most of the algae to settle quickly, and then the remaining algae and suspended matter are further separated through an ultrafiltration membrane, which greatly improves the sewage deep treatment efficiency and algae collection effect, and is not easy to clog the ultrafiltration membrane, and has high feasibility. Compared with the existing algae membrane sewage treatment system and sewage treatment method, the advantage of the present invention is that it can achieve long-term continuous sewage treatment, stable effluent water quality, greater device flexibility, higher feasibility for application in actual industrial, agricultural, and domestic sewage treatment, better economic benefits, and COD, TP, TN and NH4 + The emission concentration of -N can meet the Level A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB 18918-2002). BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the structure of a device for treating sewage using an algae membrane combined with an ultrafiltration membrane;

[0047] Figure 2 and Figure 3 A block diagram of an alternate connection mode of a light-transmitting tubular reactor and a light-impermeable tubular reactor in a tubular algae membrane system;

[0048] Figure 4 It is a structural schematic diagram of a light-transmitting tubular reactor;

[0049] Figure 5 It is a structural schematic diagram of a light-tight tubular reactor;

[0050] Figure 6 It is the structural diagram of the sedimentation tank;

[0051] Figure 7 A schematic diagram of the structure of the fixing frame.

[0052] Markings in the figure: 1. Raw water tank; 2. Liquid delivery pump; 3. Light-transmitting tubular reactor; 4. Light-opaque tubular reactor; 5. Dosing device; 6. Sedimentation tank; 7. Ultrafiltration pump; 8. Ultrafiltration membrane assembly; 9. Outlet water tank; 10. Connector; 11. End cover; 12. Vent pipe; 13. Valve; 14. Water outlet; 15. Algae; 16. Mud discharge port; 17. Fixing part; 18. Water inlet; 19. Carrier; 20. Baffle; 21. Fixing frame; 22A and 22B, annular pipe sleeve; 23. Lighting lamp. DETAILED DESCRIPTION

[0053] In order to introduce the present invention in more detail, the present invention is further described below in conjunction with embodiments. Example

[0054] A device for treating sewage using an algae membrane in combination with an ultrafiltration membrane, which is connected in sequence according to the direction of water flow, by a raw water tank 1, a tubular algae membrane system, an ultrafiltration membrane system, and an outlet water tank 9. The tubular algae membrane system is formed by alternatingly connecting a light-transmitting tubular reactor 3 and an opaque tubular reactor 4, wherein an algae membrane can be arranged inside the light-transmitting tubular reactor 3. The ultrafiltration membrane system is composed of a dosing device 5, a sedimentation tank 6, and an ultrafiltration membrane assembly 8. The dosing device 5 is arranged on a pipeline in front of the water inlet 18 of the sedimentation tank 6. The water outlet 14 of the sedimentation tank 6 is connected to the water inlet of the ultrafiltration membrane assembly 8, and liquid is delivered in between by an ultrafiltration pump 7. A liquid delivery pump 2 is arranged between the water outlet of the raw water tank 1 and the water inlet of the tubular algae membrane system, and liquid is delivered by the liquid delivery pump 2. The liquid delivery pump is preferably a peristaltic pump. The structural schematic diagram of the system device is shown in FIG. Figure 1 As shown, however, Figure 1 Only three light-transmitting tubular reactors and three light-impermeable tubular reactors are listed as being alternately connected. The number of light-transmitting tubular reactors and light-impermeable tubular reactors is selected according to actual needs and can be more than one.

[0055] The light-transmitting tubular reactor 3 and the light-impermeable tubular reactor 4 are both upright tubular reactors, and the tubular reactor is composed of a top circular end cap 11, a cylindrical part, and a conical part from top to bottom; the top circular end cap 11 is sealed and connected to the cylindrical part by a connector 10, and the connector can be a flange, a bolt, a screw, etc. The water inlet 18 of the tubular reactor is arranged on one side below the cylindrical part, and the water outlet 14 is arranged on the other side above the cylindrical part. A mud discharge port 16 is arranged at the top of the conical part, and a valve 13 is arranged at the mud discharge port 16; the inclination angle of the cone is 30-60°. Valves 13 are arranged on the water inlet and outlet pipes of the tubular reactor, and a vent pipe 12 is also arranged on its outlet pipe, the lowest point of the vent pipe 12 is higher than the liquid level in the tubular reactor, and the valve 13 on the outlet pipe is behind the vent pipe 12. The vent pipe is preferably a curved vent pipe, and the curved pipe design can reduce the impact of external pollution on the operation of the device. The structural schematic diagrams of the light-transmitting tubular reactor 3 and the light-impermeable tubular reactor 4 are shown in FIG. Figure 4 , Figure 5 shown.

[0056] The light-transmitting tubular reactor 3 and the light-impermeable tubular reactor 4 are fixedly placed by a fixing frame 21; the fixing frame 21 has an inclined surface, and the angle between the inclined surface and the horizontal ground is 45-90°; the inclined surface is set high and long according to the length, diameter and side-by-side number of the tubular reactors, and is divided into several layers by long plates or long tubes in the height direction of the inclined surface, and several annular tube sleeves 22 are provided on the long plates or long tubes to fix the tubular reactors. The light-transmitting tubular reactor 3 is fixed above the inclined surface by an annular tube sleeve 22A above the inclined surface, and the light-impermeable tubular reactor 4 is fixed below the inclined surface by an annular tube sleeve 22B below the inclined surface. An illuminating lamp 23 is provided above the inclined surface of the fixing frame 21. The illuminating lamp 23 can be arranged around the upper part of the inclined surface of the fixing frame 21, and can also be arranged on the long plate or long tube in the middle of the inclined surface, such as Figure 7 The lighting lamp can adjust the light intensity.

[0057] The algae film is formed by combining algae 15 and a carrier 19, and can be directly cultured and formed in the light-transmitting tubular reactor 3, or it can be cultured and formed in other devices in advance and then moved into the light-transmitting tubular reactor 3. Inside the light-transmitting tubular reactor 3, the top circular end cover 11 and the side wall of the cone are provided with algae film fixings 17, and the algae film is unfolded in the light-transmitting tubular reactor through the fixings 17, and the algae film is made detachable relative to the light-transmitting tubular reactor 3. The fixings 17 can be structures of any shapes, such as hooks, rings, semi-rings, etc., as long as the algae film can be fixed and easily disassembled. The diameter of the light-transmitting tubular reactor 3 is small, and a strip-shaped algae film carrier can be selected. The algae film fixings 17 can be set at the center of the top circular end cover 11 and on the side wall of the cone near the mud discharge port 16. The algae film carrier can be fully unfolded in the light-transmitting tubular reactor along the center of the reactor through these two hooks, such as Figure 4 .

[0058] Cultivating algae film directly in a light-transmitting tubular reactor means installing the carrier in the light-transmitting tubular reactor, and performing film formation and domestication in the light-transmitting tubular reactor. Cultivating algae film directly in a light-transmitting tubular reactor is easier to operate, and the domesticated algae film can immediately treat sewage with high efficiency, but because the cultivation and domestication time is long, the entire sewage treatment device needs to stop running for 10-15 days; therefore, this cultivation method is suitable for the first activation or reactivation of the entire tubular algae film system when all light-transmitting tubular reactors need to be cultivated for algae film, or when the light-transmitting tubular reactor is too long to be suitable for replacing the algae film. Algae film is cultured and formed in other devices in advance and then moved into the light-transmitting tubular reactor, which means installing the carrier in other devices, performing film formation and domestication, and moving the domesticated algae film into the light-transmitting tubular reactor; or installing the carrier in other devices, performing film formation, and after the film formation is completed, moving it into the light-transmitting tubular reactor for domestication. The algae membrane is cultured and formed in other devices in advance and then moved into the light-transmitting tubular reactor. This can save the culture and acclimation time of the algae membrane and restore the operation of the entire sewage treatment device in a short time. This culture method is suitable for when the algae membrane of a light-transmitting tubular reactor needs to be replaced during the operation of the tubular algae membrane system, or when the light-transmitting tubular reactor is short and it is convenient to replace the algae membrane.

[0059] The dosing device 5 is a fully automatic dosing device, which can adjust the dosing time and dosage of the flocculant according to the sewage flow rate and the pollutant concentration. The ultrafiltration membrane assembly 8 is PLC fully automatic controlled, and the operation of the ultrafiltration membrane assembly can be adjusted according to the sewage flow rate. The ultrafiltration membrane assembly is any one of tubular ultrafiltration membrane, plate and frame ultrafiltration membrane, roll ultrafiltration membrane or hollow fiber ultrafiltration membrane, or a combination of two or more thereof.

[0060] The water inlet 18 of the sedimentation tank 6 is arranged on one side above the sedimentation tank 6, and the water outlet 14 is arranged on the other side above the sedimentation tank 6, and the water inlet 18 is higher than the water outlet 14. A baffle 20 is arranged near the water inlet 18 in the sedimentation tank 6, and the lower end of the baffle 20 is lower than the water outlet 14, so that the flocculated algae can directly reach the lower part of the sedimentation tank, improve the sedimentation efficiency, and avoid affecting the water quality when the flow rate is large. The bottom of the sedimentation tank 6 is a cone structure with an inclination angle of 30-60°. A mud outlet 16 is arranged at the top of the cone, and a valve 13 is arranged at the mud outlet 16. The algae mud deposited at the bottom of the sedimentation tank is cleaned by regularly opening the valve at the mud outlet. The sedimentation tank can be circular or square.

[0061] The raw water tank 1 and the outlet water tank 9 can be round or square. The bottom of the raw water tank 1 can also be set to a cone structure, the cone inclination angle is 30-60 degrees, the cone top is provided with a mud discharge port, the mud discharge port is provided with a valve, and the pollutants deposited at the bottom of the raw water tank are cleaned by regularly opening the mud discharge port valve.

[0062] When the device is in operation, the sewage in the raw water tank is sent into the transparent tubular reactor of the tubular algae membrane system through the liquid delivery pump, and then comes out from the outlet of the last tubular reactor of the tubular algae membrane system, and enters the ultrafiltration membrane system from the water inlet of the sedimentation tank. Before the water inlet of the sedimentation tank, a dosing device is used to add flocculant into the water inlet pipe and mix it with water to improve the sedimentation efficiency of the algae. Then, the supernatant of the sedimentation tank is sent into the ultrafiltration membrane assembly through the ultrafiltration pump for ultrafiltration. The water coming out from the outlet of the ultrafiltration membrane assembly is stored in the outlet tank. After passing the test, it can be discharged or used in industrial and agricultural production.

[0063] One connection mode of the light-transmitting tubular reactor and the light-impermeable tubular reactor is as follows: light-transmitting tubular reactor I→light-impermeable tubular reactor I→light-transmitting tubular reactor II→light-impermeable tubular reactor II→light-transmitting tubular reactor III→light-impermeable tubular reactor III→light-transmitting tubular reactor IV→light-impermeable tubular reactor IV→light-transmitting tubular reactor V→… (see Figure 2 When all the light-transmitting tubular reactors and light-impermeable tubular reactors in the tubular algae membrane system can operate normally, the system can be operated in this connection mode.

[0064] In addition, based on the above connection, there are also the following connection methods: light-transmitting tubular reactor I → light-impermeable tubular reactor II, light-transmitting tubular reactor II → light-impermeable tubular reactor III, light-transmitting tubular reactor III → light-impermeable tubular reactor IV, light-impermeable tubular reactor I → light-transmitting tubular reactor III, light-impermeable tubular reactor II → light-transmitting tubular reactor IV, light-impermeable tubular reactor III → light-transmitting tubular reactor V, and so on (see Figure 2 The part connected with → in the figure). That is, in the light-transmitting tubular reactor and the light-impermeable tubular reactor connection chain, the previous light-transmitting tubular reactor is connected in parallel with the two light-impermeable tubular reactors that follow it, and the previous light-impermeable tubular reactor is connected in parallel with the two light-transmitting tubular reactors that follow it. When one or two adjacent tubular reactors in the tubular algae membrane system cannot work, or when the algae membrane of a light-transmitting tubular reactor needs to be replaced, a certain connection method here can be started to skip the tubular reactor that cannot work or the light-transmitting tubular reactor that needs to replace the algae membrane, so that the tubular algae membrane system can continue to operate. Furthermore, when it is necessary to temporarily reduce the number of tubular reactors in the installed tubular algae membrane system, a certain connection method here can also be started to adjust to a better sewage treatment state.

[0065] At the same time, a pipe is provided at the outlet of the raw water tank and connected to the water inlet of the light-transmitting tubular reactor II. The pipe is in a closed state at normal times and is only opened when the algae membrane of the light-transmitting tubular reactor I needs to be replaced or when either the light-transmitting tubular reactor I or the opaque tubular reactor I fails and cannot operate.

[0066] When the last tubular reactor of the tubular algae membrane system is a light-transmitting tubular reactor, the water outlet of the previous light-opaque tubular reactor of the light-transmitting tubular reactor is also connected to the front of the dosing device by a pipe. When the light-transmitting tubular reactor needs to replace the algae membrane or fails to operate, the light-transmitting tubular reactor can be temporarily skipped. By combining the series and parallel modes, the series connection mode is mainly used, and the parallel connection is used as a backup, so as to improve the operation flexibility of the entire tubular algae membrane system and even the entire device.

[0067] Another way to connect the light-transmitting tubular reactor and the light-impermeable tubular reactor is as follows (see Figure 3 ): light-transmitting tubular reactor Ⅰ (1, 2, 3...N) → light-impermeable tubular reactor ⅰ → light-transmitting tubular reactor Ⅱ (1, 2, 3...N) → light-impermeable tubular reactor ⅱ → light-transmitting tubular reactor Ⅲ (1, 2, 3...N) → light-impermeable tubular reactor ⅲ → light-transmitting tubular reactor Ⅳ (1, 2, 3...N) → light-impermeable tubular reactor ⅳ → .... Among them, 2≤N≤6, that is, 2-6 light-transmitting tubular reactors are connected to the front and rear light-impermeable tubular reactors at the same time, and the water inlet of the light-transmitting tubular reactor Ⅰ (1, 2, 3...N) is connected in parallel with the raw water tank through a liquid delivery pump. Through this connection mode, the time the sewage stays in the tubular reactor can be adjusted according to the sewage treatment capacity of each light-transmitting tubular reactor.

[0068] The above-mentioned device for treating sewage using algae membrane combined with ultrafiltration membrane is used to treat domestic sewage, industrial sewage, and agricultural sewage to achieve nitrogen and phosphorus removal from sewage. The specific steps are as follows:

[0069] (1) Cultivating algae membranes in a culture device; the initial culture can be carried out directly in a light-transmitting tubular reactor. When the algae membrane needs to be replaced later, it can be first cultured in other devices and then moved into the light-transmitting tubular reactor.

[0070] (2) After the algae biofilms have been domesticated and installed in the light-transmitting tubular reactor, and the entire device has been installed and connected, the sewage to be treated is stored in a raw water tank. The pH value is adjusted by adding acid solution or alkaline solution. At the same time, gravity is used to precipitate heavy objects in the sewage. The valve at the mud outlet at the bottom of the raw water tank is opened regularly to clean up the precipitated pollutants.

[0071] (3) At room temperature, the sewage in the raw water tank is pumped into the light-transmitting tubular reactor I through a liquid delivery pump, and the lighting conditions are provided by a lighting lamp (when the device is installed outdoors, sunlight can be used to provide lighting conditions during the day). The sewage is treated for 4-48 hours under the condition of a light intensity of 3000-100000 lux; then, the sewage and the detached suspended algae in the light-transmitting tubular reactor I are discharged into the light-opaque tubular reactor I and treated for 1-48 hours under dark conditions.

[0072] (4) The sewage and suspended algae in the light-tight tubular reactor i are then discharged into the light-transmitting tubular reactor ii, and the sewage is treated for 4 to 48 hours at a light intensity of 3000 to 100,000 lux using a lighting lamp (when the device is located outdoors, sunlight can be used to provide lighting during the day). Subsequently, the sewage and the fallen suspended algae in the light-transmitting tubular reactor ii are discharged into the light-tight tubular reactor ii and treated for 1 to 48 hours in the dark.

[0073] (5) The wastewater is treated by a tubular algae membrane system formed by alternating a number of light-transmitting tubular reactors and a number of light-impermeable tubular reactors until the COD, TP, TN and NH4 + -N meets the effluent requirements; or a specific hydraulic retention time (HRT) is set through preliminary tests, and the flow rate is adjusted by the liquid delivery pump and the valve at the water inlet of the light-transmitting tubular reactor I to feed the liquid according to the set hydraulic retention time.

[0074] (6) The effluent that meets the effluent requirements is discharged into the sedimentation tank. Flocculants are added before the water inlet of the sedimentation tank using a dosing device so that some suspended algae can be removed through sedimentation in the sedimentation tank. The supernatant in the sedimentation tank is then pumped into the ultrafiltration membrane assembly through an ultrafiltration pump to further separate the suspended matter in the effluent. The clean water from the ultrafiltration membrane assembly is stored in the effluent tank. The clean water in the effluent tank can be discharged or reused after being tested and found to be qualified.

[0075] The cultivation of the algae film includes pre-treatment of the carrier, algae film formation, and algae film domestication. The specific steps are as follows:

[0076] (1) Pretreatment of the carrier: soak the carrier in a 0.05-1.5 mol / L NaHCO3 solution for 23-25 ​​h, rinse it with deionized water 3-5 times, soak the obtained carrier in a 0.05-2.0 mol / L hydrochloric acid solution for 6-14 h, rinse it with deionized water 3-5 times and install it in the culture device after drying.

[0077] (2) Algae biofilm formation: Add BG11 culture medium into the culture device, inoculate algae into the culture medium at an initial concentration of 0.1-5 g / L, mix well and culture statically for 6-8 days.

[0078] (3) Algae membrane domestication: When the algae membrane is basically formed, the flow rate is set according to the hydraulic retention time to pass the wastewater to be treated in an equal amount to displace the culture medium until the culture medium is completely displaced. This means that the algae membrane is domesticated and can be used for wastewater treatment.

[0079] The BG11 medium is prepared by accurately weighing the medicine according to the BG11 medium formula table and dissolving it in deionized water to prepare a mother solution. When used, the mother solution is measured according to the dosage, and a corresponding volume of deionized water is added. After stirring evenly, the pH is adjusted to 7.1±0.2 with a 1 mol / L NaOH solution or HCl solution.

[0080] Application Examples

[0081] In order to illustrate the practical application effect of the method and device of the present invention, the applicant set up two sewage treatment systems and put them into trial operation, wherein the connection mode of one device (hereinafter referred to as device 1) is: raw water tank → peristaltic pump → light-transmitting tubular reactor I → light-impermeable tubular reactor I → light-transmitting tubular reactor II → light-impermeable tubular reactor II → dosing device → sedimentation tank → ultrafiltration pump → PVDF hollow fiber ultrafiltration membrane assembly → outlet water tank. The connection mode of another device (hereinafter referred to as device 2) is: raw water tank → peristaltic pump → light-transmitting tubular reactor I → light-impermeable tubular reactor I → light-impermeable tubular reactor II → light-impermeable tubular reactor II → light-impermeable tubular reactor III → light-impermeable tubular reactor III → light-impermeable tubular reactor IV → light-impermeable tubular reactor IV → dosing device → sedimentation tank → ultrafiltration pump → PVDF hollow fiber ultrafiltration membrane assembly → outlet water tank. In the device 1 and the device 2, the size of each reactor is the same, that is, after the hydraulic retention time is set, the sewage stays in each tubular reactor for the same time.

[0082] Example 1

[0083] A method for treating sewage using an algae membrane combined with an ultrafiltration membrane comprises the following steps:

[0084] (1) Pretreatment of the carrier: Soak the three-dimensional elastic polyvinyl chloride carrier in a 0.5 mol / L NaHCO3 solution for 24 h, rinse it with deionized water four times, soak the obtained carrier in a 1.0 mol / L hydrochloric acid solution for 6 h, rinse it with deionized water four times and install it in a light-transmitting tubular reactor after drying.

[0085] (2) Algae biofilm formation: Add BG11 culture medium into the light-transmitting tubular reactor, inoculate Scenedesmus obliquus into the culture medium at an initial concentration of 1 g / L, mix well and culture statically for 7 days.

[0086] (3) Algae film domestication: When the algae film is basically formed, introduce the untreated sewage into the light-transmitting tube reactor at a flow rate of 4 days at a hydraulic retention time. Every day, 1 / 4 of the total volume of the culture medium in the light-transmitting tube reactor is replaced with the untreated sewage. This process is repeated for 4 days. In the last day, all the culture medium in the light-transmitting tube reactor is replaced with sewage. This completes the domestication.

[0087] (4) The treated sewage is introduced into the raw water tank, and the pH value is adjusted to 6.6-7.3 by adding acid solution or alkaline solution. The inlet and outlet valves of the peristaltic pump and the tubular reactor are opened, and the liquid is introduced at a flow rate of 4 days of hydraulic retention time. The sewage treatment is started formally, and it is operated continuously for 16 days. The effluent quality is tested every two days. Sunlight is used to provide lighting conditions during the day, and lighting conditions are provided by lighting conditions at night. The lighting intensity of the lighting is 4500 lux. The sludge outlets of the raw water tank, tubular reactor, and sedimentation tank are opened every other day to discharge sludge.

[0088] When the raw water treated above is natural water, its COD, TP, TN and NH4 + -N concentrations were 66.7mg / L, 0.49mg / L, 3.13mg / L, and 2.79mg / L, respectively. After treatment by device 1, COD, TP, TN, and NH4 + The average concentrations of -N were 11.52mg / L, 0.04mg / L, 0.25mg / L, and 0.17mg / L, respectively, and had an impact on COD, TP, TN, and NH4 + The average removal rates of -N were 82.73%, 91.84%, 91.91% and 93.76% respectively. After treatment by device 2, COD, TP, TN, NH4 + The average concentrations of -N were 11.45mg / L, 0.04mg / L, 0.24mg / L, and 0.16mg / L, respectively, and had an impact on COD, TP, TN, and NH4 + The average removal rates of -N were 82.83%, 91.84%, 92.33% and 94.26% respectively. It can be seen that the discharge concentration of natural water bodies treated by device 1 and device 2 according to the above sewage treatment method reached the Class II standard of the "Surface Water Environmental Quality Standard" (GB 3838-2002), but the sewage treatment capacity of device 2 was twice that of device 1.

[0089] Example 2

[0090] A method for treating sewage using an algae membrane combined with an ultrafiltration membrane comprises the following steps:

[0091] (1) Pretreatment of the carrier: Soak the three-dimensional elastic polyvinyl chloride carrier in a 0.5 mol / L NaHCO3 solution for 24 h, rinse it with deionized water four times, soak the obtained carrier in a 1.0 mol / L hydrochloric acid solution for 6 h, rinse it with deionized water four times and install it in a light-transmitting tubular reactor after drying.

[0092] (2) Algae biofilm formation: Add BG11 culture medium into the light-transmitting tubular reactor, inoculate Scenedesmus obliquus into the culture medium at an initial concentration of 1 g / L, mix well and culture statically for 7 days.

[0093] (3) Algae film domestication: When the algae film is basically formed, introduce the untreated sewage into the light-transmitting tube reactor at a flow rate of 6 days at a hydraulic retention time. Every day, 1 / 6 of the total volume of the culture medium in the light-transmitting tube reactor is replaced with the untreated sewage. This process is repeated for 6 days. In the last day, all the culture medium in the light-transmitting tube reactor is replaced with sewage. This completes the domestication.

[0094] (4) The treated sewage is introduced into the raw water tank, and the pH value is adjusted to 6.6-7.3 by adding acid solution or alkaline solution. The inlet and outlet valves of the peristaltic pump and the tubular reactor are opened, and the liquid is introduced at a flow rate of 6 days for the hydraulic retention time. The sewage treatment is started and the operation is continued for 24 days. The effluent quality is tested every two days. Sunlight is used to provide lighting conditions during the day, and lighting conditions are provided at night. The lighting intensity of the lighting is 4500 lux. The sludge outlets of the raw water tank, tubular reactor, and sedimentation tank are opened every other day to discharge sludge.

[0095] When the raw water treated above is simulated domestic sewage, its COD, TP, TN and NH4 + -N concentrations were 578.71mg / L, 12.76mg / L, 34.38mg / L, and 11.13mg / L, respectively. After treatment by device 1, COD, TP, TN, and NH4 + The average concentrations of -N were 47.57mg / L, 0.37mg / L, 3.08mg / L, and 1.33mg / L, respectively, and had an impact on COD, TP, TN, and NH4 + The average removal rates of -N were 91.78%, 97.10%, 91.04% and 88.05% respectively. After treatment by device 2, COD, TP, TN, NH4 + The average concentrations of -N were 43.17mg / L, 0.36mg / L, 2.70mg / L, and 1.02mg / L, respectively, and had an impact on COD, TP, TN, and NH4 +The average removal rates of -N were 92.54%, 97.18%, 92.14% and 90.83% respectively. It can be seen that the discharge concentration of simulated domestic sewage treated by device 1 and device 2 according to the above sewage treatment method can reach the Class A standard of the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB 18918-2002), but the sewage treatment capacity of device 2 is twice that of device 1.

[0096] When the raw water treated above is actual domestic sewage, its COD, TP, TN and NH4 + -N concentrations were 256.10mg / L, 6.39mg / L, 60.21mg / L, and 49.50mg / L, respectively. After treatment by device 1, COD, TP, TN, and NH4 + The average concentrations of -N were 42.87mg / L, 0.17mg / L, 10.40mg / L, and 3.45mg / L, respectively, and had an impact on COD, TP, TN, and NH4 + The average removal rates of -N were 83.26%, 97.27%, 82.73% and 93.03% respectively. After treatment by device 2, COD, TP, TN, NH4 + The average concentrations of -N were 37.34mg / L, 0.18mg / L, 10.20mg / L, and 3.41mg / L, respectively, and had an impact on COD, TP, TN, and NH4 + The average removal rates of -N were 85.42%, 97.18%, 83.05% and 93.11% respectively. It can be seen that the discharge concentration of the actual domestic sewage treated by the above sewage treatment methods using device 1 and device 2 can reach the Class A standard of the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB l89l8-2002), but the sewage treatment capacity of device 2 is twice that of device 1.

[0097] It can also be seen from the sewage treatment effects of the device 1 and the device 2 in the above embodiment 1 or embodiment 2 that, using the device of the present invention, increasing the number of tubular reactors can increase the sewage treatment capacity without reducing the effluent water quality. Therefore, the device of the present invention can be used to increase the sewage treatment capacity by increasing the number of tubular reactors, thereby improving the continuity and efficiency of sewage treatment.

Claims

1. A method for treating sewage using an algae membrane combined with an ultrafiltration membrane, characterized in that: The method comprises the following steps: (1) Cultivating algae membranes; (2) The sewage to be treated is first stored in a raw water tank, and the pH value is adjusted by adding acid solution or alkaline solution, while using gravity to precipitate the heavy objects in the sewage; (3) At room temperature, the sewage in the raw water tank is sent to a reactor equipped with an algae membrane. The sewage is treated for 4-48 hours under a light intensity of 3000-100000 lux, and the nitrogen and phosphorus in the sewage are removed by the photosynthesis of algae cells. Subsequently, the sewage and the detached suspended algae are discharged into a reactor without an algae membrane and treated for 1-48 hours in the dark. The respiration of the suspended algae is used to remove nitrogen and phosphorus in the sewage and consume the dissolved oxygen in the sewage. (4) The sewage and suspended algae in the reactor without algae membrane are discharged into another reactor equipped with algae membrane, and the sewage is treated for 4-48 hours under the condition of light intensity of 3000-100000 lux; then, the sewage and the detached suspended algae are discharged into another reactor without algae membrane and treated for 1-48 hours under dark conditions; (5) Alternately connect several reactors equipped with algae membranes and reactors without algae membranes, and repeat step (4) several times until the COD, TP, TN and NH4 in the sewage are + -N meets the water outlet requirements; (6) The sewage that meets the effluent requirements is discharged into the sedimentation tank, and flocculants are added to settle the suspended algae in the sewage. The supernatant in the sedimentation tank is then ultrafiltered using an ultrafiltration membrane to further separate the suspended matter and water, thus achieving continuous, efficient and high-quality sewage treatment; The algae is one or more of the group consisting of: Scalycophyte, Anabaena flos-aquae, Chlorella pyrenoidosa, Scenedesmus obliquus, Hydrodictyum, and Oscillatoria axolotl. The flocculant is one or more of polyaluminium chloride, polyaluminium ferric chloride, polyaluminium ferric sulfate, polyferric sulfate and polyacrylamide.

2. The method for treating sewage using algae membrane combined with ultrafiltration membrane according to claim 1, characterized in that: The cultivation of the algae film includes pre-treatment of the carrier, algae film formation, and algae film domestication. The specific steps are as follows: (1) Pretreatment of the carrier: soak the carrier in a 0.05-1.5 mol / L NaHCO3 solution for 23-25 ​​h, rinse it with deionized water 3-5 times, soak the obtained carrier in a 0.05-2.0 mol / L hydrochloric acid solution for 6-14 h, rinse it with deionized water 3-5 times and install it in the culture device after drying; (2) Algae biofilm formation: Add BG11 culture medium into the culture device, inoculate algae in the culture medium at an initial concentration of 0.1-5 g / L, mix well and culture statically until algae biofilm formation is basically complete; (3) Algae membrane acclimation: The wastewater to be treated is introduced into the culture device at a flow rate set according to the hydraulic retention time, and the culture medium in the culture device is replaced in equal amounts until the culture medium is completely replaced. This completes the acclimation of the algae membrane and can begin to treat the wastewater.

3. A device for treating sewage using an algae membrane combined with an ultrafiltration membrane, characterized in that: The device is connected in sequence by a raw water tank, a tubular algae membrane system, an ultrafiltration membrane system, and an outlet water tank according to the direction of water flow; the tubular algae membrane system is formed by alternately connecting a light-transmitting tubular reactor and a light-impermeable tubular reactor, wherein an algae membrane can be arranged in the light-transmitting tubular reactor; the ultrafiltration membrane system is composed of a dosing device, a sedimentation tank, and an ultrafiltration membrane assembly, wherein the dosing device is arranged on a pipeline in front of the water inlet of the sedimentation tank, and the water outlet of the sedimentation tank is connected to the water inlet of the ultrafiltration membrane assembly; The light-transmitting tubular reactor and the light-impermeable tubular reactor are fixedly placed by a fixing frame; a lighting lamp is arranged on the fixing frame to provide lighting conditions for photosynthesis of algae cells; the lighting lamp can adjust the light intensity; The light-transmitting tubular reactor and the light-impermeable tubular reactor are both upright tubular reactors, and the tubular reactor is composed of a top circular end cover, a cylindrical part, and a conical part from top to bottom; the water inlet of the tubular reactor is arranged on one side below the cylindrical part, and the water outlet is arranged on the other side above the cylindrical part; valves are arranged on the water inlet and water outlet pipes of the tubular reactor; a mud outlet is arranged at the top of the conical part, and a valve is arranged at the mud outlet, and the inclination angle of the cone is 30-60°; inside the light-transmitting tubular reactor, the top circular end cover and the side wall of the cone are provided with fixings for the algae membrane, and the algae membrane is unfolded in the light-transmitting tubular reactor through the fixings and the algae membrane is detachable relative to the light-transmitting tubular reactor; The water inlet of the sedimentation tank is arranged on one side above the sedimentation tank, and the water outlet is arranged on the other side above the sedimentation tank, and the water inlet is higher than the water outlet; a baffle is arranged near the water inlet in the sedimentation tank, and the lower end of the baffle is lower than the water outlet, so that the flocculated algae can directly reach the lower part of the sedimentation tank; the bottom of the sedimentation tank is a cone structure, and the inclination angle of the cone is 30-60°, and a mud discharge port is arranged at the top of the cone, and a valve is arranged at the mud discharge port.

4. Use the device for treating sewage using algae membrane combined with ultrafiltration membrane as described in claim 3 to treat domestic sewage, industrial sewage, and agricultural sewage according to the method for treating sewage using algae membrane combined with ultrafiltration membrane as described in any one of claims 1-2 to achieve nitrogen and phosphorus removal from sewage.

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