Method and device for removing phosphorus in high-salinity wastewater by utilizing mud flat microalgae

Abstract

The invention provides a method for removing phosphorus from high-salinity wastewater by utilizing mudflat microalgae, which comprises the following steps: collecting silt rich in microalgae from a mudflat, washing with deionized water to obtain a mudflat microalgae culture solution, then carrying out expanding culture, and finally applying the mudflat microalgae culture solution to a phosphorus removal device. The dephosphorization device comprises a filter tank, a water quality adjusting tank, an acid and alkali liquor storage tank and a dephosphorization tank. According to the method, the mud flat microalgae is used for treating the high-salinity wastewater for the first time, the method has the advantages of being environmentally friendly, low in cost and low in technical requirement, the problems that a traditional biological method is low in phosphorus removal efficiency and unstable in system operation are solved, and a new technical thought can be provided for phosphorus removal of the high-salinity wastewater.

Description

Technical Field

[0001] The invention belongs to the field of sewage and wastewater treatment, and in particular relates to a method and a device for removing phosphorus from high-salinity wastewater by utilizing tidal flat microalgae. Background Art

[0002] Phosphorus is an important industrial raw material, widely used in fertilizers, detergents, food additives and metal processing industries. A large amount of phosphorus-containing wastewater is generated during industrial production. Discharge of this wastewater into water bodies will lead to excessive growth of algae and aquatic plants, which in turn will cause environmental problems such as water hypoxia, water quality deterioration, and ecological imbalance, affecting fisheries, tourism and drinking water safety. Therefore, controlling phosphorus emissions and developing efficient phosphorus removal technologies are crucial to ensuring water ecological safety.

[0003] At present, the technologies for removing phosphorus from industrial wastewater mainly include chemical precipitation, adsorption, and biological methods. Among them, the biological method uses the life activities of microorganisms to remove phosphorus from water bodies. It has many advantages such as environmental protection, economy, stability, and strong integration. It is an efficient and sustainable technology for removing phosphorus from wastewater. However, with the development of industry, the composition of phosphorus-containing wastewater has become increasingly complex. Especially in industrial production processes such as marine aquaculture, food processing, pharmaceuticals, and metal processing, wastewater usually contains a large amount of salt. High concentrations of salt will destroy the osmotic pressure balance of microbial cells, reduce the activity of microbial enzymes, and poison microbial cells, resulting in a significant decrease in the phosphorus removal effect of high-salt wastewater, and the system operation is unstable and prone to collapse.

[0004] The acquisition of salt-tolerant microorganisms is the key to the application of biological methods to treat high-salt and phosphorus-containing wastewater. At present, there are three main ways to obtain salt-tolerant microorganisms, including gradient salinity acclimation of activated sludge, screening of salt-tolerant functional bacteria, and direct use of microorganisms in high-salt environments (such as tidal flats and saline-alkali land). Compared with the first two, the direct use of microorganisms in high-salt environments has the advantages of low cost, simple operation, high treatment efficiency, and broad application prospects. In a high-salt environment, bacteria and algae are the main microbial groups. At present, salt-tolerant bacteria are mainly collected for phosphorus removal from high-salt wastewater, while salt-tolerant algae phosphorus removal technology is relatively rare.

[0005] The tidal flat is a wide sediment accumulation body located in the transition zone between land and sea, and is periodically submerged and exposed by seawater. Due to the rich nutrition and sufficient sunlight, the surface of the tidal flat is rich in microalgae, such as diatoms, cyanobacteria and chlorella. These tidal flat microalgae have strong salt tolerance and phosphorus metabolism ability, and have the potential to efficiently treat high-salinity and phosphorus-containing wastewater. Summary of the invention

[0006] Based on the characteristics of tidal flat microalgae with strong salt tolerance and phosphorus metabolism ability, the present invention develops a method for removing phosphorus from high-salinity wastewater using tidal flat microalgae, which can solve the problems of low phosphorus removal efficiency and unstable system operation of the current biological method, and provide a new technical idea for removing phosphorus from high-salinity wastewater. In order to achieve the above purpose and other related purposes, the present invention provides a method and device for removing phosphorus from high-salinity wastewater using tidal flat microalgae.

[0007] A method for removing phosphorus from high-salinity wastewater using tidal flat microalgae comprises the following steps:

[0008] Step 1) contacting high-salt wastewater with an iron-carbon filler to react and obtain pretreated wastewater; the iron-carbon filler contains iron and carbon; the iron content of the iron-carbon filler is 30-60wt%, and the carbon content is 1-5wt%;

[0009] Step 2) culturing beach microalgae in the pretreated wastewater, so that the beach microalgae absorb phosphorus in the pretreated wastewater to obtain phosphorus-removed wastewater; the beach microalgae are collected from beach mud and cultured.

[0010] Optionally, in the step 1), the high-salt wastewater is filtered and then contacted with the iron-carbon filler; during the contact process, the oxygen content of the pretreated wastewater is maintained at 6 to 9 mg / L by aeration;

[0011] Preferably, high-salt wastewater is filtered using a filter with a pore size of less than or equal to 1 mm.

[0012] Optionally, the iron-carbon filler is prepared by mixing and granulating raw materials including cast iron powder, fly ash and montmorillonite, and the particle size is 1 to 5 mm;

[0013] The weight ratio of the cast iron powder to fly ash is 1 to 4:1; the weight ratio of the cast iron powder to montmorillonite is 1 to 4:1.

[0014] Optionally, the method of collecting and culturing microalgae from tidal flat sand in step 2) comprises:

[0015] The muddy beach is collected, water is added, stirred evenly, and then allowed to stand for sedimentation. The supernatant is added to salt water to obtain a culture solution of microalgae on the beach. The culture solution of microalgae on the beach is then cultured to make the chlorophyll a content in the culture solution of microalgae on the beach reach 200-600 μg / L.

[0016] Optionally, the sampling depth of the tidal flat sand is 0 to 2 cm in the vertical direction, and the collected tidal flat sand is stored at 0 to 4° C.;

[0017] The sediment was mixed with deionized water in a ratio of 100 to 300 g of tidal flat sediment to 1 L of water, stirred on a magnetic stirrer at a tangential flow rate of 20 to 50 cm / s for 1 to 3 h, then allowed to settle for 20 to 30 min, and the supernatant was collected.

[0018] Optionally, the tidal flat microalgae culture solution has a salinity of 20-30‰, and oxygen is supplied to the tidal flat microalgae culture solution at a flow rate of 5-10 L / h through an air pump, and the culture is carried out under a light condition of 5000-10000 Lux;

[0019] Preferably, the tidal flat microalgae culture solution further comprises 0.1-0.5 g / L of glucose, 0.01-0.05 g / L of ammonium chloride, and 0.001-0.005 g / L of potassium dihydrogen phosphate.

[0020] Optionally, during the process of culturing tidal flat microalgae in the pretreated wastewater, the pH of the pretreated wastewater is adjusted to 6 to 9; during the culturing process, the oxygen content of the pretreated wastewater is maintained at 6 to 9 mg / L through aeration, and the light source is maintained at 5000 to 10000 Lux; a portion of the dephosphorized wastewater is discharged, and the remaining dephosphorized wastewater is returned to the pretreated wastewater for circulation treatment.

[0021] A device for removing phosphorus from high-salinity wastewater by using beach microalgae, comprising:

[0022] A regulating tank, wherein the regulating tank is provided with an iron-carbon filler; the regulating tank is used to contact high-salt wastewater with the iron-carbon filler to react and obtain pre-treated wastewater; the regulating tank is provided with an regulating tank aeration device;

[0023] A dephosphorization tank is connected to the regulating tank, and is used to cultivate beach microalgae in the pretreated wastewater. The beach microalgae absorbs phosphorus in the pretreated wastewater to obtain dephosphorized wastewater. A dephosphorization tank aeration device is provided in the dephosphorization tank. A light source is provided above the dephosphorization tank.

[0024] Optionally, the device further comprises a filter tank, in which a filter screen is provided, and the filter tank is connected to the regulating tank;

[0025] Optionally, the filling ratio of the carbon filler in the regulating tank is 30-50% of the volume of the liquid in the tank body;

[0026] Optionally, the dephosphorization pool is filled with suspended ball fillers with a diameter of 2 to 4 cm and a filling density of 1000 to 2000 balls / m 3 .

[0027] Optionally, the regulating tank is connected to a pH regulating liquid storage tank, and the pH regulating liquid storage tank is used to pass the pH regulating liquid into the regulating tank;

[0028] Optionally, the outlet of the dephosphorization tank is connected to the inlet of the dephosphorization tank via a reflux pipe, and a reflux pump is provided on the reflux pipe.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention uses tidal flat microalgae to remove phosphorus from high-salinity wastewater, providing a natural wastewater treatment solution that is green, environmentally friendly, low cost, and has low technical requirements;

[0031] 2) It solves the problem that the current biological method for removing phosphorus from high-salinity wastewater is inefficient and prone to system collapse, and provides a new technical approach for removing phosphorus from high-salinity wastewater;

[0032] 3) No toxic or harmful water treatment by-products will be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a schematic diagram of a device for removing phosphorus from high-salinity wastewater using tidal flat microalgae in the present invention;

[0035] Figure 2 The removal rate of total phosphorus in high-salinity and phosphorus-containing wastewater by tidal flat microalgae. DETAILED DESCRIPTION

[0036] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0037] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0039] The terms "include", "including", "have", "contain" and the like used in this article are open-ended terms, which mean including but not limited to. First, collect mud and sand rich in microalgae from the beach, store it in a constant temperature box and bring it back to the laboratory. Then, take a certain amount of mud and sand rich in beach microalgae and place it in a container, add a certain amount of deionized water, and place it on a magnetic stirrer for thorough stirring. After that, let it stand and settle for a period of time, take out the supernatant, and add deionized water to the mud and sand again, and repeat the above process several times. Mix the obtained supernatants together to obtain a beach microalgae culture solution, which is rich in beach microalgae.

[0040] Preferably, when collecting microalgae-rich sediment from the beach, the sampling depth is in the range of 0 to 2 cm in the vertical direction;

[0041] Preferably, the temperature of the thermostat is 0-4°C;

[0042] Preferably, the mixing ratio of the sediment rich in benthic microalgae and deionized water is 100-300 g of sediment rich in benthic microalgae in 1 L of deionized water;

[0043] Preferably, when the magnetic stirrer is stirring, the tangential flow velocity in the container is controlled at 20 to 50 cm / s, and the stirring time is controlled at 1 to 3 h;

[0044] Preferably, the static sedimentation time is 20 to 30 minutes;

[0045] Preferably, the repetition number is 2 to 4 times.

[0046] Based on the above-mentioned tidal flat microalgae culture solution, the second aspect of the present invention provides a method for expanding tidal flat microalgae. First, the tidal flat microalgae culture solution is placed in a transparent container, artificial seawater prepared with sodium chloride is added, and suitable growth conditions are provided, including: supplying oxygen through an air pump, providing light through a fluorescent lamp, controlling the temperature and pH within a suitable range, and adding appropriate nutrients. Under the above conditions, the microalgae biomass is cultured for a period of time to reach a certain range, and the expanded tidal flat microalgae culture solution is obtained.

[0047] Preferably, the transparent container is made of glass, organic glass or polyethylene;

[0048] Preferably, the salinity of the artificial seawater is 20-30‰, and the ratio of the artificial seawater to the culture solution of the beach microalgae is 5-10L of artificial seawater to 1L of the culture solution of the beach microalgae;

[0049] Preferably, the air pump flow rate is controlled at 5 to 10 L / h;

[0050] Preferably, the light intensity provided by the fluorescent lamp is controlled at 5000-10000 Lux;

[0051] Preferably, the temperature is controlled at 20-30°C and the pH is controlled at 6-9;

[0052] Preferably, the nutrient salt components and dosages are: glucose 0.1-0.5 g / L, ammonium chloride 0.01-0.05 g / L, potassium dihydrogen phosphate 0.001-0.005 g / L, and all of the above drugs are analytically pure.

[0053] Preferably, the microalgae biomass is measured by measuring the chlorophyll a content in the culture solution, and the chlorophyll a content is controlled to be 200-600 μg / L.

[0054] After obtaining the above-mentioned culture solution of the microalgae cultivated on the beach, the third aspect of the present invention provides a device for applying the culture solution of the microalgae cultivated on the beach to remove phosphorus from high-salinity wastewater ( Figure 2 ), including four components: a filter tank 1, a water quality regulating tank 5, an acid-base liquid reserve tank 3, and a dephosphorization tank 8. A filter screen 2 is arranged in the filter tank. The water regulating tank is filled with iron-carbon fillers 6, is equipped with an aeration head 7, and is connected to the acid-base liquid reserve tank 3. The acid-base reserve liquid in the acid-base liquid reserve tank enters the water quality regulating tank 5 through a metering pump 2. The dephosphorization tank 8 contains tidal flat microalgae, is filled with suspended ball fillers 10 made of polyethylene material, and is equipped with an aeration head 7. In addition, a fluorescent lamp 9 is installed above the dephosphorization tank to provide illumination for maintaining the photosynthetic activity of the microalgae. The effluent from the dephosphorization tank 8 is refluxed back to the dephosphorization tank 8 through a reflux pump 11.

[0055] Preferably, the filter mesh aperture is less than or equal to 1 mm;

[0056] Preferably, the iron-carbon filler is prepared by mixing cast iron powder, fly ash and montmorillonite in a ratio of 1 to 4:1:1 and by a granulator, and the particle size is 1 to 5 mm;

[0057] Preferably, the filling ratio of the iron-carbon filler in the water pool regulating tank is 30-50% of the liquid volume in the tank body;

[0058] Preferably, the aeration heads in the water pool regulating tank are installed at the bottom, and the installation density is 1 / m 2 , air supply volume is 1~5m 3 / h;

[0059] Preferably, the acid and alkali solution storage tank contains 1-5% dilute hydrochloric acid and 1-5% sodium hydroxide solution;

[0060] Preferably, the amount of microalgae added to the tidal flat in the dephosphorization pool is set according to 1L of culture solution for expanding the tidal flat microalgae for every 10-20L of liquid in the dephosphorization pool;

[0061] Preferably, the diameter of the suspended ball filler in the dephosphorization tank is 2 to 4 cm, and the packing density is 1 m 3 CIC adds 1,000 to 2,000;

[0062] Preferably, the aeration heads in the dephosphorization tank are installed at the bottom with a density of 1 head / m 2 , air supply volume is 0.5~1m 3 / h.

[0063] Preferably, the light intensity provided by the fluorescent lamp above the dephosphorization tank is 5000-10000 Lux.

[0064] The fourth aspect of the present invention provides an operation method of the above-mentioned device, including two stages of trial operation and formal operation. In the operation stage, high-salt phosphorus-containing wastewater is injected into the device, the inlet and outlet of the device are closed, and static culture is carried out for a period of time, so that the beach microalgae adapt to the water quality conditions of the high-salt wastewater, and can fully grow on the suspended ball filler in the dephosphorization tank. After that, the inlet and outlet of the device are opened for formal operation. High-salt phosphorus-containing wastewater first enters the filter tank through the water inlet, and is filtered through the filter to remove large-sized impurities. Then, it flows into the water pool regulating tank, where the pH of the wastewater is adjusted to an appropriate range. In addition, the iron-carbon filler forms "iron-carbon micro-electrolysis" to convert phosphorus-containing substances (organic phosphorus) into orthophosphates, which is convenient for subsequent microalgae to use. The aeration head in the water pool regulating tank supplies oxygen, which can enhance the effect of "iron-carbon micro-electrolysis". After that, the wastewater flows into the dephosphorization tank. The beach microalgae attached to the suspended filler balls in the dephosphorization tank take phosphates in the wastewater as nutrients for life activities, thereby removing phosphorus. Finally, part of the treated wastewater is discharged through the outlet of the dephosphorization tank, and part of the wastewater is returned to the dephosphorization tank for secondary treatment. In addition, the suspended ball filler in the dephosphorization tank needs to be replaced regularly to avoid a decrease in the treatment effect.

[0065] Preferably, the flow rate of wastewater in the device is less than 5 mm / s

[0066] Preferably, the static culture time is 15 to 30 days;

[0067] Preferably, the suitable range of the wastewater pH is 6 to 9;

[0068] Preferably, the ratio of effluent from the dephosphorization tank to reflux water is 1:2-4;

[0069] Preferably, the replacement cycle of the suspended ball filler in the dephosphorization pool is 60 to 90 days. The high-salt phosphorus-containing wastewater used in the following examples is wastewater from a marine aquaculture plant, with a total phosphorus content of 2.67 mg / L and a salinity of 24.32%. The total phosphorus content of the wastewater was measured by ammonium molybdate spectrophotometry (GB11893-89). The sampling Hach HQ30D multi-parameter water quality analyzer was used to measure the salinity of the wastewater.

[0070] Example 1

[0071] A method for removing phosphorus from high-salinity wastewater using tidal flat microalgae, the specific steps are as follows:

[0072] (1) Collection of microalgae from tidal flats. The Dongtan Beach in Chongming, Shanghai was selected as the tidal flat microalgae collection area. First, the microalgae-rich sediment within the range of 0 to 2 cm on the surface of the tidal flat was scraped, stored in an incubator at 4°C, and brought back to the laboratory. Then, the collected sediment was placed in a container, and deionized water was added. The addition ratio was 100 g of sediment in 1 L of deionized water. Subsequently, the container containing the sediment mixture was placed on a magnetic stirrer, and the speed was adjusted so that the tangential flow velocity in the container was 20 cm / s, and the mixture was stirred thoroughly for 1 hour. Afterwards, it was allowed to stand and settle for 20 minutes, the supernatant was taken out, and the same amount of deionized water was added again, and the above process was repeated twice. The obtained supernatants were mixed together to obtain the tidal flat microalgae culture solution.

[0073] (2) Cultivation of microalgae on the tidal flat. Add the above-mentioned microalgae culture solution to a container made of plexiglass, and add artificial seawater prepared with sodium chloride with a salinity of 20‰, with the ratio of 1L microalgae culture solution to 5L artificial seawater. Supply oxygen through an air pump, and the air pump flow rate is controlled at 5L / h; provide light through a fluorescent lamp, and the light intensity is 5000Lux; control the temperature at 20℃; control the pH at 6; the nutrient salt content is: glucose 0.1g / L, ammonium chloride 0.01g / L, potassium dihydrogen phosphate 0.001g / L, and the above drugs are all analytically pure. Stop the cultivation when the chlorophyll a content in the solution reaches 200μg / L.

[0074] (3) Device configuration. The overall structure of the device is shown in Figure 1 , including a filter tank 1, a filter screen 2, an acid and alkali liquid storage tank 3, a metering pump 4, a water quality regulating tank 5, an iron-carbon filler 6, an aeration head 7, a dephosphorization tank 8, a fluorescent lamp 9, a suspended ball filler 10, and a reflux pump 11. Among them, the pore size of the filter screen 2 is 1mm; the acid and alkali liquid storage tank 3 stores 1% of dilute hydrochloric acid and sodium hydroxide solution; the iron-carbon filler 6 is made of cast iron powder, fly ash and montmorillonite, mixed in a ratio of 1:1:1, and prepared by a granulator, with a particle size of 1mm; the filling ratio of the iron-carbon filler in the water quality regulating tank is 30% of the liquid volume in the tank body; the air flow of the aeration head 7 in the water quality regulating tank is controlled at 1m 3 / h; aeration maintains the oxygen content of the pretreated wastewater at 6 mg / L. The amount of microalgae added to the tidal flat in the dephosphorization pool is 1L of culture solution for every 10L of liquid in the pool; the diameter of the suspended ball filler in the dephosphorization pool is 2cm, and the filling density is 1m 3 1000 are added in the middle; the air flow rate of aeration head 7 in the dephosphorization tank is controlled at 0.5m 3 / h.

[0075] (4) Operation of the device. Wastewater from a marine aquaculture plant was injected into the device and statically cultured for 15 days according to the set conditions. After that, the inlet and outlet of the device were opened for formal operation. High-salt phosphorus-containing wastewater first entered the filter tank through the inlet and was filtered through the filter to remove impurities with a diameter greater than 1 mm. Then, it flowed into the water pool regulating tank, where the pH of the wastewater was adjusted to 7. In addition, the iron-carbon filler formed "iron-carbon micro-electrolysis" to convert phosphorus-containing substances (organic phosphorus) into orthophosphate, which is convenient for subsequent microalgae to use. The aeration head in the water pool regulating tank supplies oxygen, which can enhance the effect of "iron-carbon micro-electrolysis". After that, the wastewater flowed into the dephosphorization tank. The tidal flat microalgae attached to the suspended filler balls in the dephosphorization tank absorb the phosphate in the wastewater as nutrients for life activities, thereby removing phosphorus. Finally, part of the treated wastewater was discharged through the outlet of the dephosphorization tank, and part of the wastewater was returned to the dephosphorization tank for secondary treatment. The ratio of effluent and return water in the dephosphorization tank was 1:2.

[0076] Example 2

[0077] A method for removing phosphorus from high-salinity wastewater using tidal flat microalgae, the specific steps are as follows:

[0078] (1) Collection of microalgae from tidal flats. Shanghai Chongming Dongtan was selected as the tidal flat microalgae collection area. First, the microalgae-rich sediment within the range of 0 to 2 cm on the surface of the tidal flat was scraped, stored in an incubator at 0°C, and brought back to the laboratory. Then, the collected sediment was placed in a container and deionized water was added. The addition ratio was 300 g of sediment in 1 L of deionized water. Subsequently, the container containing the sediment mixture was placed on a magnetic stirrer, and the speed was adjusted so that the tangential flow velocity in the container was 50 cm / s, and the mixture was stirred thoroughly for 2 hours. Afterwards, it was allowed to stand and settle for 30 minutes, the supernatant was taken out, and the same amount of deionized water was added again, and the above process was repeated 4 times. The obtained supernatants were mixed together to obtain the tidal flat microalgae culture solution.

[0079] (2) Cultivation of tidal flat microalgae. Add the above tidal flat microalgae culture solution into a container made of plexiglass, and add artificial seawater prepared with sodium chloride with a salinity of 30‰, with the ratio of 1L tidal flat microalgae culture solution to 10L artificial seawater. Supply oxygen through an air pump, and the air pump flow rate is controlled at 10L / h; provide light through a fluorescent lamp, and the light intensity is 10000Lux; control the temperature at 30℃; control the pH at 9; the nutrient salt content is: glucose 0.5g / L, ammonium chloride 0.05g / L, potassium dihydrogen phosphate 0.005g / L, and the above drugs are all analytically pure. Cultivate until the chlorophyll a content in the solution reaches 600μg / L and then stop the cultivation.

[0080] (3) Device configuration. The overall structure of the device is shown in Figure 1 , wherein the pore size of the filter 2 is 0.5mm; the acid and alkali solution storage tank 3 stores 5% dilute hydrochloric acid and sodium hydroxide solution; the iron-carbon filler 6 is made of cast iron powder, fly ash and montmorillonite, mixed in a ratio of 4:1:1, and prepared by a granulator, with a particle size of 5mm; the filling ratio of the iron-carbon filler in the water pool regulating tank is 50% of the liquid volume in the pool body; the air flow rate of the aeration head 7 in the water quality regulating tank is controlled at 5m 3 / h; aeration maintains the oxygen content of the pretreated wastewater at 9 mg / L; the dosage of the beach microalgae in the dephosphorization pool is 1L of the culture solution of the expanded beach microalgae for every 20L of liquid volume in the pool; the diameter of the suspended ball filler in the dephosphorization pool is 4cm, and the filling density is 1m 3 2000 are added in the middle; the air flow rate of aeration head 7 in the dephosphorization tank is controlled at 1m 3 / h; Fluorescent light intensity above the dephosphorization pool

[0081] (4) Operation of the device. Wastewater from a marine aquaculture plant was injected into the device and statically cultured for 30 days according to the set conditions. After that, the inlet and outlet of the device were opened for formal operation. High-salt phosphorus-containing wastewater first entered the filter tank through the inlet and was filtered through the filter to remove impurities with a diameter greater than 0.5 mm. Then, it flowed into the water pool regulating tank, where the pH of the wastewater was adjusted to 9. In addition, the iron-carbon filler formed "iron-carbon micro-electrolysis" to convert phosphorus-containing substances (organic phosphorus) into orthophosphate, which is convenient for subsequent microalgae to use. The aeration head in the water pool regulating tank supplies oxygen, which can enhance the effect of "iron-carbon micro-electrolysis". After that, the wastewater flowed into the dephosphorization tank. The tidal flat microalgae attached to the suspended filler balls in the dephosphorization tank absorb the phosphate in the wastewater as nutrients for life activities, thereby removing phosphorus. Finally, part of the treated wastewater was discharged through the outlet of the dephosphorization tank, and part of the wastewater was returned to the dephosphorization tank for secondary treatment. The ratio of effluent and return water in the dephosphorization tank was 1:4.

[0082] Comparative Example 1

[0083] The conventional AAO process (anaerobic-anoxic-aerobic process) was used to remove phosphorus from the wastewater of the marine aquaculture plant, and the treatment effects were compared with those of Examples 1 and 2. The main process and parameter settings of the AAO process are as follows. (1) Sludge was obtained from a sewage treatment plant and inoculated into the reactor. The initial sludge concentration (in terms of MLSS) was 2000 mg / L, and the volume of the inoculated sludge was 15% of the total volume of the reactor; (2) The hydraulic retention time was 2, 3 and 8 h in the anaerobic, anoxic and aerobic zones, respectively; (3) Dissolved oxygen was <0.2 mg / L, <0.5 mg / L and 3 mg / L in the anaerobic, anoxic and aerobic zones, respectively; (4) The sludge age was 10 days; (5) The internal reflow ratio (anoxic zone to anaerobic zone): 150%, the external reflow ratio (aerobic zone to anoxic zone): 100%; (6) The pH value was 6-9; (7) The temperature was 20-30°C.

[0084] Figure 2 The total phosphorus removal rates of Example 1, Example 2 and Comparative Example 3 for wastewater from aquaculture plants are shown. The system was run for 90 days, during which the changes in total phosphorus in the effluent from different treatment methods were recorded, and the total phosphorus removal rate was calculated by the following formula:

[0085]

[0086] Where: p is the total phosphorus removal rate, %; c t is the total phosphorus content in the effluent after t days of operation; c0 is the initial total phosphorus content in the wastewater of the marine aquaculture plant.

[0087] from Figure 2 It can be seen that in the initial stage of operation, the total phosphorus removal rates of Examples 1 and 2 are lower than those of Comparative Example 1. However, as the operating time increases, the total phosphorus removal rates of Examples 1 and 2 continue to increase, and eventually stabilize at around 96%. The above results show that the present invention has excellent high-salt wastewater phosphorus removal effects. But at the same time, the present invention requires a period of stable operation to achieve a higher phosphorus removal effect. In contrast, the phosphorus removal effect of Comparative Example 1 gradually decreases with the operating time. After stable operation, its total phosphorus removal rate is only 30-40%, which is much lower than the total phosphorus removal rate of the present invention.

[0088] Comparative Example 2

[0089] Filling the water quality regulating tank with iron-carbon filler to convert phosphorus-containing organic matter in high-salt phosphorus-containing wastewater into phosphate is a key step to ensure the subsequent absorption and utilization of phosphorus by microalgae. In order to reflect the importance of this step to the present invention, the iron-carbon filler 6 in the water quality regulating tank 5 is removed in Comparative Example 2, and the other implementation steps are consistent with Example 1. Specifically:

[0090] (1) Collection of microalgae from tidal flats. The Dongtan Beach in Chongming, Shanghai was selected as the tidal flat microalgae collection area. First, the microalgae-rich sediment within the range of 0 to 2 cm on the surface of the tidal flat was scraped, stored in an incubator at 4°C, and brought back to the laboratory. Then, the collected sediment was placed in a container, and deionized water was added. The addition ratio was 100 g of sediment in 1 L of deionized water. Subsequently, the container containing the sediment mixture was placed on a magnetic stirrer, and the speed was adjusted so that the tangential flow velocity in the container was 20 cm / s, and the mixture was stirred thoroughly for 1 hour. Afterwards, it was allowed to stand and settle for 20 minutes, the supernatant was taken out, and the same amount of deionized water was added again, and the above process was repeated twice. The obtained supernatants were mixed together to obtain the tidal flat microalgae culture solution.

[0091] (2) Cultivation of microalgae on the tidal flat. Add the above-mentioned microalgae culture solution to a container made of plexiglass, and add artificial seawater prepared with sodium chloride with a salinity of 20‰, with the ratio of 1L microalgae culture solution to 5L artificial seawater. Supply oxygen through an air pump, and the air pump flow rate is controlled at 5L / h; provide light through a fluorescent lamp, and the light intensity is 5000Lux; control the temperature at 20℃; control the pH at 6; the nutrient salt content is: glucose 0.1g / L, ammonium chloride 0.01g / L, potassium dihydrogen phosphate 0.001g / L, and the above drugs are all analytically pure. Stop the cultivation when the chlorophyll a content in the solution reaches 200μg / L.

[0092] (3) Device configuration. The overall structure of the device is shown in Figure 1 , including a filter tank 1, a filter screen 2, an acid and alkali solution storage tank 3, a metering pump 4, a water quality regulating tank 5, an aeration head 7, a phosphorus removal tank 8, a fluorescent lamp 9, a suspended ball filler 10, and a reflux pump 11. Compared with Example 1, no iron-carbon filler is added, wherein the pore size of the filter screen 2 is 1 mm; 1% dilute hydrochloric acid and sodium hydroxide solution are stored in the acid and alkali solution storage tank 3; the air flow rate of the aeration head 7 in the water quality regulating tank is controlled at 1m 3 / h; the dosage of beach microalgae in the dephosphorization pool is 1L of culture solution for expanding beach microalgae for every 10L of liquid volume in the pool; the diameter of the suspended ball filler in the dephosphorization pool is 2cm, and the filling density is 1m 3 1000 are added in the middle; the air flow rate of aeration head 7 in the dephosphorization tank is controlled at 0.5m 3 / h.

[0093] (4) Operation of the device. Wastewater from a marine aquaculture plant was injected into the device and statically cultured for 15 days according to the set conditions. After that, the inlet and outlet of the device were opened for formal operation. High-salt and phosphorus-containing wastewater first entered the filter tank through the inlet and was filtered through the filter to remove impurities with a diameter greater than 1 mm. Then, it flowed into the water pool regulating tank, where the pH of the wastewater was adjusted to 7. The aeration head in the water pool regulating tank supplied oxygen. After that, the wastewater flowed into the dephosphorization tank. The tidal flat microalgae attached to the suspended filler balls in the dephosphorization tank absorbed the phosphate in the wastewater as nutrients for their life activities, thereby removing phosphorus. Finally, a part of the treated wastewater was discharged through the outlet of the dephosphorization tank, and another part of the wastewater was returned to the dephosphorization tank for secondary treatment. The ratio of effluent and return water in the dephosphorization tank was 1:2.

[0094] from Figure 2 It can be seen that when the iron-carbon filler pretreatment is not performed, the total phosphorus removal rate is only about 50%, which is a significant decrease compared to Example 1 and Example 2.

[0095] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for removing phosphorus from high-salinity wastewater using tidal flat microalgae, characterized in that: The steps include: Step 1) contacting high-salt wastewater with an iron-carbon filler to react and obtain pretreated wastewater; the iron-carbon filler contains iron and carbon; the iron content of the iron-carbon filler is 30-60wt%, and the carbon content is 1-5wt%; Step 2) culturing beach microalgae in the pretreated wastewater, so that the beach microalgae absorb phosphorus in the pretreated wastewater to obtain phosphorus-removed wastewater; the beach microalgae are collected from beach mud and cultured.

2. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 1, characterized in that: In the step 1), the high-salt wastewater is filtered and then contacted with the iron-carbon filler; During the contact process, the oxygen content of the pretreated wastewater is maintained at 6 to 9 mg / L by aeration; Preferably, high-salt wastewater is filtered using a filter with a pore size of less than or equal to 1 mm.

3. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 1, characterized in that: The iron-carbon filler is made by mixing and granulating raw materials including cast iron powder, fly ash and montmorillonite, and the particle size is 1 to 5 mm; The weight ratio of the cast iron powder to fly ash is 1 to 4:1; the weight ratio of the cast iron powder to montmorillonite is 1 to 4:

1.

4. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 1, characterized in that: The method for collecting and culturing microalgae from tidal flat sand in step 2) comprises: The muddy beach is collected, water is added, stirred evenly, and then allowed to stand for sedimentation. The supernatant is added to salt water to obtain a culture solution of microalgae on the beach. The culture solution of microalgae on the beach is then cultured to make the chlorophyll a content in the culture solution of microalgae on the beach reach 200-600 μg / L.

5. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 4, characterized in that: The sampling depth of collecting mudflats is 0 to 2 cm in the vertical direction, and the collected mudflats are stored at 0 to 4°C; The sediment was mixed with deionized water in a ratio of 100 to 300 g of tidal flat sediment to 1 L of water, stirred on a magnetic stirrer at a tangential flow rate of 20 to 50 cm / s for 1 to 3 h, then allowed to settle for 20 to 30 min, and the supernatant was collected.

6. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 4, characterized in that: The salinity of the microalgae culture solution on the tidal flat is 20-30‰, oxygen is supplied to the microalgae culture solution on the tidal flat at a flow rate of 5-10L / h through an air pump, and the culture is carried out under a light condition of 5000-10000Lux; Preferably, the tidal flat microalgae culture solution further comprises 0.1-0.5 g / L of glucose, 0.01-0.05 g / L of ammonium chloride, and 0.001-0.005 g / L of potassium dihydrogen phosphate.

7. The method for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 1, characterized in that: During the process of cultivating tidal flat microalgae in the pretreated wastewater, the pH of the pretreated wastewater is adjusted to 6-9; during the cultivation process, the oxygen content of the pretreated wastewater is maintained at 6-9 mg / L through aeration, and the light source is maintained at 5000-10000 Lux; a part of the dephosphorized wastewater is discharged, and the remaining dephosphorized wastewater is returned to the pretreated wastewater for circulation treatment.

8. A device for removing phosphorus from high-salinity wastewater using tidal flat microalgae, characterized in that: include: A regulating tank, wherein an iron-carbon filler is provided in the regulating tank; the regulating tank is used to contact the high-salt wastewater with the iron-carbon filler to react and obtain pre-treated wastewater; The regulating tank is provided with a regulating tank aeration device; A dephosphorization tank is connected to the regulating tank, and is used to cultivate beach microalgae in the pretreated wastewater. The beach microalgae absorbs phosphorus in the pretreated wastewater to obtain dephosphorized wastewater. A dephosphorization tank aeration device is provided in the dephosphorization tank. A light source is provided above the dephosphorization tank.

9. The device for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 8, characterized in that: The device also includes a filter tank, in which a filter screen is provided, and the filter tank is connected to the regulating tank; Preferably, the filling ratio of the carbon filler in the regulating tank is 30-50% of the volume of the liquid in the tank body; Preferably, the dephosphorization pool is filled with suspended ball fillers with a diameter of 2 to 4 cm and a filling density of 1000 to 2000 balls / m 3 .

10. The device for removing phosphorus from high-salinity wastewater using tidal flat microalgae according to claim 8, characterized in that: The regulating tank is connected to a pH regulating liquid storage tank, and the pH regulating liquid storage tank is used to pass the pH regulating liquid into the regulating tank; Preferably, the outlet of the dephosphorization tank is connected to the inlet of the dephosphorization tank via a reflux pipe, and a reflux pump is provided on the reflux pipe.

Images