CN103789195A - Membrane microalgae photobioreactor for realizing in-situ solid-liquid separation and culture method thereof - Google Patents

Abstract

A membrane microalgae photobioreactor for realizing in-situ solid-liquid separation, including a liquid level balance water tank, a reactor body, a microporous diffuser, a hollow fiber membrane module, a constant flow pump, and the like. The cultivation method of the membrane microalgae photobioreactor, the culture liquid enters the main body of the reactor through the liquid level balance tank, provides the nutrients required for the growth of the microalgae and keeps the liquid level constant, and the cultured algae liquid is installed in the middle of the reactor The hollow fiber membrane module realizes solid-liquid separation in situ. Under the suction and filtration of the constant flow pump, the water is discharged from the constant flow pump through the membrane module, and the microalgae cells are retained in the reactor, and the microalgae cells are regularly separated. reward. The present invention proposes a new type of membrane microalgae photobioreactor capable of in-situ solid-liquid separation, which has a simple structure and is easy to operate. High hydraulic load operation, thus greatly improving the operating efficiency of the photobioreactor.

Description

A membrane microalgae photobioreactor and its cultivation method for realizing in-situ solid-liquid separation

technical field

The invention relates to the technical field of algae cultivation reactors, in particular to a membrane microalgae photobioreactor for realizing in-situ solid-liquid separation.

The present invention also relates to a method for cultivating microalgae using the above-mentioned device.

Background technique

Microalgae has the characteristics of rapid growth and high photosynthetic efficiency. It can effectively use solar energy to convert inorganic nutrients, CO ₂ , H ₂ O and other substances into organic compounds through photosynthesis. Because of its high oil content, easy cultivation, high yield per unit area, and low It is considered to be the only currently known raw material that may replace fossil fuels due to its advantages such as occupying arable land. In addition, microalgae can also fix _CO2 in the air during the growth process and contribute to the mitigation of the greenhouse effect.

In the large-scale cultivation of microalgae, the closed photobioreactor can artificially control the growth conditions of microalgae, thereby obtaining a higher growth rate of algae cells and avoiding the pollution of miscellaneous algae and bacteria. In addition, the photobioreactor has a simple structure and can be scaled up according to production needs, which is suitable for efficient large-scale cultivation of microalgae. At present, the high cost in the production process is the main limiting factor for the development of microalgae production of biodiesel industry, and the cost of microalgae cultivation accounts for more than 70% of the total cost of biodiesel production. The cost of microalgae cultivation mainly comes from the inorganic nutrients such as nitrogen and phosphorus and fresh water resources consumed in the cultivation.

In order to reduce the cost of microalgae cultivation, people try to cultivate microalgae by using urban sewage, secondary treated water, aquaculture wastewater, etc., which contain a certain amount of nitrogen, phosphorus and nutrient salts and have clear and transparent water quality for microalgae cultivation. The production cost of algae biodiesel is also beneficial to the improvement of surface water quality. However, compared with the artificially prepared microalgae culture solution, the concentration of nitrogen and phosphorus in these waste waters is low, the growth rate of the microalgae is slow, the production capacity of the reactor is low, and it is also difficult to obtain a high-concentration microalgae culture solution. Facilitate the subsequent harvest of microalgae cells. In order to maintain a high growth rate of microalgae in the photobioreactor, it is necessary to increase the influent flow of the reactor accordingly to increase the supply of nitrogen and phosphorus. The traditional photobioreactor has no solid-liquid separation function, and the hydraulic pressure in the reactor The residence time and the residence time of microalgae are the same, and increasing the influent flow rate will shorten the residence time of microalgae in the reactor, reduce the concentration of algae liquid in the reactor, and cause the microalgae per unit volume of the reactor to decrease. Reduced production capacity. Therefore, it is difficult for the traditional photobioreactors used for culturing microalgae to meet the needs of cultivating microalgae in water bodies with low nitrogen and phosphorus content.

Contents of the invention

The object of the present invention is to provide a microalgae photobioreactor with the function of in-situ solid-liquid separation, the in-situ separation of water and microalgae can be realized through the submerged membrane module installed in the reactor, and the microalgae is separated in the reactor The residence time and concentration in the reactor can be adjusted manually, so that the reactor can operate at a higher hydraulic load when using the secondary treatment effluent of urban sewage with low nitrogen and phosphorus content as the nutrient solution for microalgae cultivation, thus greatly improving the The operating efficiency of the photobioreactor.

Another object of the present invention is to provide a method for cultivating microalgae using the reactor.

In order to achieve the above object, the submerged membrane microalgae photobioreactor provided by the present invention, its main structure includes: water inlet tank, water pump, liquid level balance water tank, reactor main body, hollow fiber membrane module, constant flow pump, liquid flow meter , Outlet pipe, microporous diffuser, air flow meter, air compressor, sampling and microalgae discharge pipe.

In the method for cultivating microalgae using the reactor provided by the present invention, the nutrient solution is sucked into the liquid level balance water tank by the water pump, the outlet end of the liquid level balance water tank is connected with the lower end of the reactor main body through the water inlet pipe, and the nutrient solution flows automatically from the liquid level balance water tank Continuously enter the main body of the membrane microalgae photobioreactor to provide the microalgae in the reactor with the nutrient solution required for growth and keep the water level at a constant position. The main shell of the reactor is a cylindrical plexiglass container. The bottom of the main body of the reactor is equipped with a microporous diffuser connected to the air compressor. The tiny air bubbles generated can stir the mixed liquid, keep the algae cells in suspension, and provide the carbon source required for their growth. The ventilation rate is controlled at 0.20 ~0.65vvm, the gas is discharged from the gas outlet pipe installed on the top side of the reactor main shell. The algae liquid cultivated in the reactor is separated from the solid and liquid in situ through the submerged hollow fiber membrane module installed in the middle, and the effluent without microalgae is continuously discharged from the reactor through the submerged membrane module and the constant flow pump connected to it. The microalgae cells are separated by the hollow fiber membrane module and kept in the reactor. The high-concentration microalgae cultured in the reactor are regularly discharged from the reactor through the sampling and microalgae discharge pipes, so as to realize the harvest of microalgae cells and the renewal of microalgae in the reactor.

In the above technical solution, the hollow fiber membrane module is cylindrical, and the membrane module is a microfiltration membrane or an ultrafiltration membrane with a pore size of 0.001-0.2 μm. The membrane module has the effect of solid-liquid separation in the reactor. Its role is mainly to realize the separation of the hydraulic residence time and the solid residence time in the reactor. The residence time of algae in the main body of the reactor is controlled at 10-36 days. In the process of operation, according to the water quality characteristics such as the nitrogen and phosphorus content of the influent water, the inflow and outflow flow can be adjusted to change the hydraulic load of the reactor to achieve high operating efficiency.

In the above technical solution, the shell of the main body of the reactor is made of transparent plexiglass material, which can transmit the light of the external light source. The external light source can be fluorescent lamp or LED lamp, etc., which are evenly distributed around the outer cylinder and fixed by brackets to ensure that the reactor is in the Obtain uniform light from all directions, providing light source for the growth of microalgae. The light intensity at the outer wall of the reactor is 2000-6000lux, and the light-to-dark ratio is set to (10-14)L:(14-10)D, which can effectively promote the growth and reproduction of microalgae.

In the above technical scheme, the microalgae culture solution can be replaced by the artificially prepared microalgae culture solution, thereby greatly reducing the amount of microalgae The cost of cultivation, on the other hand, through the cultivation of microalgae in the reactor, a large amount of nitrogen and phosphorus in the sewage is absorbed and removed, and the content of dissolved oxygen in the effluent is increased, which effectively improves the water quality.

In the above technical scheme, the microalgae can use algae species with faster growth and reproduction rates such as Scenedesmus, Spirulina, Chlorella, Seaweed, Nostoc, Chromococcus, etc., to maximize the use of membrane microalgae photobioreactors. operating efficiency. When microalgae are cultivated using the secondary treatment effluent of urban sewage containing a certain amount of pollutants, Scenedesmus and Chlorella are selected as the preferred algae according to the indicators such as pollution resistance, growth rate, oil content, nitrogen and phosphorus removal rate, etc. kind.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The submerged membrane microalgae photobioreactor provided by the present invention can control the hydraulic retention time and the microalgae residence time respectively, and can operate with a higher hydraulic load than the traditional photobioreactor, so it can use nitrogen-containing Secondary treatment effluent of urban sewage with low phosphorus content, aquaculture wastewater, etc. have outstanding advantages in microalgae cultivation, and the hydraulic load can reach 0.5-2.0m ³ /(m ³ ·d) when treating urban sewage secondary treatment effluent , when the concentration of nitrogen and phosphorus in the influent is much lower than that of the traditional microalgae culture solution, the nitrogen and phosphorus nutrient loads provided to the reactor can still reach 7.0-40.5g N/(m ³ ·d) and 0.6-2.3g P/ (m ³ ·d), so as to realize the efficient operation of the reactor.

2. The submerged membrane microalgae photobioreactor provided by the present invention can realize the in-situ separation of microalgae and culture solution in the reactor, and can control the residence time of culture solution and microalgae in the reactor respectively. While increasing the influent flow rate to increase the nutrient load of the reactor, the microalgae in the reactor will not be lost with the effluent, and the concentration of microalgae can be maintained when the secondary treatment effluent of urban sewage with low nitrogen and phosphorus content is used for cultivation. At a high level of 3500-6000mg/L, the unit volume reactor has a higher nitrogen and phosphorus absorption rate and microalgae production rate. The absorption rate of nitrogen reaches 4.3-10.5g N/(m ³ ·d), the absorption rate of phosphorus reaches 0.1-0.3g P/(m ³ ·d), and the production rate of microalgae reaches 50-94g/(m ³ · d).

3. Applying the submerged membrane microalgae photobioreactor provided by the present invention can realize the coupling of deep wastewater purification and microalgae biofuel production, and the concentration of TN in the effluent can be reduced to below 5 mg/L, and the concentration of TP can be reduced to 0.3 mg/L In the following, a high-efficiency, low-consumption water quality deep purification technology is provided for the reuse of wastewater. At the same time, experimental studies have shown that the use of waste water with low nitrogen and phosphorus content in microalgae cultivation can not only greatly save the cultivation cost compared with the artificially prepared culture solution, but also the lower nitrogen and phosphorus nutrient environment effectively promotes the microalgae cells. For the accumulation of oil, the oil content of microalgae can be increased by 4% to 10%.

The present invention will be further described in detail below in conjunction with the accompanying drawings and the corresponding specific embodiments.

Description of drawings

Accompanying drawing is the structural representation of the film microalgae photobioreactor that realizes in-situ solid-liquid separation of the present invention

Among them: 1-reactor main body, 2-microporous diffuser, 3-hollow fiber membrane module, 4-outlet pipe, 5-sampling and microalgae discharge pipe, 6-air flow meter, 7-air compressor, 8- Inlet pool, 9-water pump, 10-liquid level balance tank, 11-constant flow pump, 12-liquid flow meter.

Detailed ways

Example 1:

Referring to the accompanying drawings, a membrane microalgae photobioreactor that realizes in-situ solid-liquid separation, the microalgae culture solution in the water inlet tank 8 enters the liquid level balance water tank 10 through the water pump 9, and the water outlet end of the liquid level balance water tank 10 passes through the water inlet The water pipe communicates with the lower end of the reactor main body 1, so as to input the microalgae culture solution into the reactor and keep the water level at a constant position. The outer cylinder of the reactor main body 1 is made of transparent plexiglass, with an air outlet pipe 4 on the side of the upper end, a sampling and microalgae discharge pipe 5 on the top, and a microporous diffuser 2 at the bottom, and the microporous diffuser 2 passes through an air flow meter 6 is connected with air compressor 7. A hollow fiber membrane module 3 is arranged inside the reactor main body 1, and is connected to a constant flow pump 11 and a liquid flow meter 12 in sequence through an outlet pipe.

Take the effluent of a city sewage treatment plant as microalgae culture solution, the water quality is NH4 ⁺ -N6.1～12.5mg/L, NO ₃ ^- -N4.2～10.8mg/L, NO ₂ ^- -N0.2～1.3mg /L, PO ₄ ^3- -P0.1～0.9mg/L, SS4.6～15.5mg/L, COD25～80mg/L, pH 6.4～7.8. Enter the photobioreactor main body 1 from the water inlet pool 8 through the water pump 9 and the liquid level balance water tank 10, and adjust the air flow meter 6 to control the air flow entering the reactor from the microporous diffuser 2, so that the microalgae in the reactor can be kept at In the suspended growth state, the ventilation rate is controlled at 0.20-0.35vvm, and the liquid in the reactor is continuously discharged through the constant flow pump 11 and the hollow fiber membrane module 3 connected thereto. The hollow fiber membrane module 3 is a microfiltration membrane made of polypropylene , the pore size is 0.05-0.2μm, by adjusting the flow rate of the constant flow pump 11, the hydraulic retention time of the effluent from the urban sewage treatment plant in the reactor is controlled at 1-2d, and the corresponding hydraulic load is 0.5-1.0m ³ /(m ³ · d). When the concentration of nitrogen and phosphorus in the influent is much lower than that of the traditional microalgae culture solution, the nitrogen and phosphorus nutrient loads provided to the reactor can still reach 9.4-18.5gN/(m ³ d) and 0.3-0.9gP/(m ³ ·d), which promotes the high-speed reproduction of microalgae in the reactor. The microalgae cultivated in the reactor are retained in the reactor because they cannot pass through the hollow fiber membrane module 3, so that the concentration of microalgae in the reactor continues to rise, reaching a high concentration in the effluent of urban sewage treatment plants with low nitrogen and phosphorus content. The effect of microalgae, the concentration of microalgae can reach 3500-6000mg/L when chlorella is used for cultivation, and the high-concentration algae liquid obtained from the cultivation is regularly discharged from the reactor through the sampling and microalgae discharge pipe 5 to realize microalgae cells. Harvesting and renewal of microalgae in the reactor.

The film microalgae photobioreactor of the present invention realizes the in-situ solid-liquid separation of the culture medium and the microalgae, even if the effluent of the urban sewage treatment plant with the above-mentioned low nitrogen and phosphorus content is used to cultivate microalgae, the reaction rate of the reactor per unit volume to nitrogen Phosphorus uptake rate and microalgae production rate both reached a high level. The nitrogen absorption rate reaches 5.2-7.5g N/(m ³ ·d), the phosphorus absorption rate reaches 0.1-0.3g P/(m ³ ·d), and the microalgae production rate reaches 51-74g/(m ³ d), the TN concentration in the effluent is less than 5mg/L and the TP concentration in the effluent is less than 0.3mg/L in the stable operation stage, which can be used not only for the cultivation of microalgae, but also for the deep denitrification and phosphorus removal of sewage.

Claims (5)

1. A membrane microalgae photobioreactor that realizes in-situ solid-liquid separation, including a reactor body with an air outlet pipe, sampling and microalgae discharge pipes at the top, and a microporous diffuser at the bottom of the reactor body The air flow meter and the air compressor are connected in parallel, and it is characterized in that a hollow fiber membrane module is installed in the main body of the reactor, and the hollow fiber microfiltration membrane module is connected with a constant flow pump and a liquid flow meter. A liquid level balance water tank, the outlet end of the liquid level balance water tank communicates with the lower end of the reactor main body through a water inlet pipe. 2. The membrane microalgae photobioreactor realizing in-situ solid-liquid separation as claimed in claim 1, is characterized in that, described hollow fiber membrane module is cylindrical, and membrane module is microfiltration membrane or ultrafiltration membrane, and membrane The top height of the component installation is lower than the top height of the liquid level balance tank. 3. A method for cultivating microalgae using the reactor described in claim 1, characterized in that the microalgae culture solution enters the main body of the reactor continuously through the water pump and the liquid level balance water tank, and passes through the micropores installed at the bottom of the reactor. The diffuser provides microbubbles to the reactor, and the high-concentration algae liquid obtained from the cultivation in the reactor is regularly discharged from the sampling and microalgae discharge pipe, and the effluent without microalgae passes through the submerged membrane module and the constant flow pump connected to it. Continuous discharge from the reactor. 4. The method according to claim 3, characterized in that the residence time of the culture solution in the main body of the film microalgae photobioreactor is controlled at 1～3d, and the residence time of the microalgae in the main body of the film microalgae photobioreactor Controlled in 10 ~ 36d. 5. The method according to claim 3, characterized in that the air flow provided by the microporous diffuser in the reactor is controlled at 0.20～0.65vvm.

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