CN109554300B - Method for harvesting oil-producing microalgae in urban sewage culture system by using self-flocculating microalgae - Google Patents
Method for harvesting oil-producing microalgae in urban sewage culture system by using self-flocculating microalgae Download PDFInfo
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Abstract
The invention relates to a method for harvesting oil-producing microalgae in a municipal sewage culture system by using self-flocculating microalgae, which comprises the following steps: a step of adding, namely adding a self-flocculating algae solution with a certain concentration into an oil-producing microalgae solution; and B: a flocculation step, wherein the mixed algae liquid obtained in the step A is subjected to flocculation treatment; and C: and a separation step, wherein algae-laden water separation treatment is carried out. The method for harvesting the oil-producing microalgae by utilizing the self-flocculation characteristic of the self-flocculation microalgae avoids the problems of high energy consumption of a physical or chemical flocculant and pollution to a final product, obviously reduces the production and operation cost in the harvesting process, and is an efficient, economic and environment-friendly microalgae harvesting method. The microalgae utilizes nutrient substances such as carbon, nitrogen, phosphorus and the like in the municipal sewage to carry out growth metabolism and oil accumulation, promotes the degradation of organic pollutants in the water, reduces carbon emission in the municipal sewage treatment process to a certain extent, and realizes the conversion of the sewage from the pollutants to microalgae growth raw materials.
Description
Technical Field
The invention relates to a harvesting method of microalgae, in particular to a method for harvesting oil-producing microalgae in a municipal sewage culture system by utilizing self-flocculating microalgae.
Background
In the face of the dual challenges of energy crisis and environmental water pollution, the biodiesel is produced by utilizing the oil-producing microalgae cultured by the urban sewage, which is beneficial to exploring a new way for treating the urban sewage and relieving the pressure of relative shortage of energy.
The process for producing biodiesel by utilizing oil-producing microalgae cultured by urban sewage mainly comprises the steps of culturing the microalgae, harvesting, extracting grease, transesterification and the like, wherein the cost for harvesting biomass accounts for 20-30% of the total production cost, and microalgae cells have the characteristics of small volume, low density and uniform distribution in a culture system, so that the technical bottleneck still exists in the efficient and economic harvesting of the microalgae. The microalgae harvesting method mainly comprises centrifugation, air flotation, sedimentation, filtration, flocculation and the like. The centrifugal method has high energy consumption; the filtration method has high cost and is easy to cause membrane blockage; the sedimentation method consumes long time; the air floatation method needs pretreatment and is not suitable for large-scale industrial application.
At present, microalgae are efficiently harvested by a flocculation method, wherein flocculation can be divided into chemical, physical and biological flocculation, but the use of a chemical flocculant increases the production cost, and residues of the chemical flocculant bring troubles to downstream treatment; the physical flocculation has high cost and large energy consumption; bioflocculation can avoid contamination of the final product by chemical flocculants, but the technical requirements or costs are high.
For example, CN101748068A discloses a microalgae harvesting method, which mainly comprises five parts, namely a high-density culture photoreactor, a sedimentation tank, a submersible pump, a solar system, and a pulverizer/grinder. The method comprises the steps of A, settling; B. removing supernatant, pumping the upper layer algae liquid with a submersible pump, and recycling; C. drying, irradiating the lower concentrated algae solution with sunlight, and sun drying to obtain algae tablet; D. and preparing the algae tablets into algae powder by a pulverizer or grinding, and the algae powder can be used for subsequent processing. The method is simple to operate, but the algae are not easy to settle, so the harvesting process is time-consuming, and the harvesting speed requirement of large-scale production is difficult to meet.
CN 106995248A discloses a green, safe and rapid microalgae harvesting method, firstly, food-grade natural macromolecular flocculant is used for electrically neutralizing negative charges on surfaces of algae particles to promote the stability of the algae particles to be lost, and algae flocs are further formed under the action of bridge-bridging net-trapping of macromolecular chains. Then, the micro bubbles generated by the electric air floatation are adhered to the algae flocs to form a water-gas-floc three-phase mixed system, and the water-gas-floc three-phase mixed system quickly floats to the water surface to realize quick collection of the algae. The method is short in time consumption, high in energy consumption and high in cost because high-power electric energy output needs to be maintained, and the food-grade natural macromolecular flocculant is high in cost and difficult to meet the requirement of industrial production of the algae biofuel on low cost.
Therefore, finding a cost-effective green harvesting method is one of the most challenging areas in algal biofuel research, and is also a key factor limiting the commercialization of microalgae.
Disclosure of Invention
In view of the technical problems in the prior art, the invention provides a method for harvesting oil-producing microalgae in a municipal sewage culture system by utilizing self-flocculating microalgae, which is used for overcoming the problems of high cost, high energy consumption and difficult industrial application of the existing microalgae harvesting method.
The technical scheme of the invention is as follows: the method for harvesting the oil-producing microalgae in the municipal sewage culture system by using the self-flocculating microalgae comprises the following steps:
step A: a step of adding, in which a self-flocculating algae solution with a certain concentration is added into an oil-producing microalgae solution;
and B: a flocculation step of performing flocculation treatment on the mixed algae liquid obtained in the step A;
and C: and D, a separation step, namely, carrying out algae-laden water separation treatment on the flocculating constituent obtained in the step B.
Because the formed floc has larger volume, the algae-laden water can be separated by utilizing the filter cloth under the action of gravity. The method can harvest the oil-producing microalgae in a green, efficient and economical manner.
The further technical scheme of the invention is as follows: the oil-producing microalgae is one or more of chlorella, scenedesmus obliquus, crescent moon algae and Dunaliella salina obtained by mutation, domestication and screening, and the oil content is more than 20%. The method has wide application range.
The further technical scheme of the invention is as follows: the self-flocculation microalgae is one or more of filamentous algae, Asterina, Fusarium fiber algae and Scenedesmus which are cultured in urban sewage and are easy to settle. The sedimentation rate can reach more than 90 percent within 12 hours.
The further technical scheme of the invention is as follows: by measuring OD680The self-flocculating microalgae and the oil-producing microalgae are cultured in the municipal sewage to the earlier stage of the stationary phaseHarvesting was performed at the highest biomass.
The further technical scheme of the invention is as follows: in the step A, the self-flocculating algae liquid is prepared into uniformly distributed suspension by using a dispersion machine, and the rotating speed of the dispersion machine is 1000-1500 rpm; when the adding amount of the self-flocculating algae is small, the oil-producing microalgae cells capable of adsorbing and flocculating are limited, and when the adding amount of the self-flocculating algae is too large, mutual adsorption among the self-flocculating microalgae is easily formed, so that the adsorption of the oil-producing microalgae is influenced, and the yield of the oil-producing microalgae is reduced. Therefore, the adding amount of the self-flocculating algae has better concentration, and the better concentration range obtained by experiments is 0.06-0.10 g/L.
The further technical scheme of the invention is as follows: and in the step B, the formation of algae flocs is induced by regulating and controlling the pH of the mixed algae solution, adding calcium ions, magnesium ions and other conditions, and the conditions play a decisive role in the harvesting efficiency of the microalgae.
The further technical scheme of the invention is as follows: and in the step B, the initial pH value when the self-flocculation microalgae is used for harvesting the oil-producing microalgae is set to be 8-10.
The further technical scheme of the invention is as follows: and the concentration of calcium and magnesium ions added in the step B is 4-6 mmoL/L.
The further technical scheme of the invention is as follows: and B, uniformly mixing the algae liquid by using a shaking table and accelerating the formation of algae flocs, wherein the rotation speed of the shaking table is 120-140 rpm.
The further technical scheme of the invention is as follows: and C, standing for 30min after the step B is carried out for 6-12 h, and then carrying out the step C.
The further technical scheme of the invention is as follows: the filter cloth has too small aperture, which affects the filtration rate; the loss of algae will be caused by too large aperture. And C, carrying out algae-laden water separation by adopting 60-100 meshes of filter cloth. The algae liquid passes through the filter cloth under the action of gravity, and the microalgae flocs are retained on the filter cloth, so that the algae-water separation is realized. Compared with the method that the filter membrane vacuum filtration is adopted when the oil-producing microalgae are harvested independently, the energy consumption of algae-water separation can be greatly reduced.
The invention has the beneficial effects that:
the scheme constructs a method for harvesting oil-producing microalgae in a municipal sewage culture system by using self-flocculating microalgae, and the self-flocculating microalgae has the advantages of safety, environmental protection, low cost and simple operation; meanwhile, the urban domestic sewage has high content of organic matters, nitrogen, phosphorus and other nutrient substances, is beneficial to mass propagation of microalgae, realizes the conversion of the sewage from pollutants to microalgae growth raw materials, and provides a technology with good industrial prospect for microalgae harvesting.
The method for harvesting the oil-producing microalgae by utilizing the self-flocculation characteristic of the self-flocculation microalgae avoids the problems of high energy consumption of a physical or chemical flocculant and pollution to a final product, obviously reduces the production and operation cost in the harvesting process, and is an efficient, economic and environment-friendly microalgae harvesting method. The microalgae utilizes nutrient substances such as carbon, nitrogen, phosphorus and the like in the municipal sewage to carry out growth metabolism and oil accumulation, promotes the degradation of organic pollutants in the water, reduces carbon emission in the municipal sewage treatment process to a certain extent, and realizes the conversion of the sewage from the pollutants to microalgae growth raw materials.
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FIG. 1 is a flow diagram of the present invention, wherein 1, a microalgae suspension is self-flocculated; 2. producing oil microalgae; 3. mixing the algae solution; 4. shaking table; 5. and (4) flocculating constituent.
Detailed Description
Preferred embodiments of the present invention will be described in further detail below with reference to specific examples and drawings, but the present invention is not limited thereto.
The invention provides a method for harvesting oil-producing microalgae in an urban sewage culture system by utilizing self-flocculating microalgae. The present invention will be described in detail below with reference to the accompanying drawings and examples.
As shown in fig. 1, the specific embodiment of the present invention is: provided is a method for harvesting oleaginous microalgae in a municipal sewage culture system by using self-flocculating microalgae, comprising the following steps: 1. self-flocculating the microalgae suspension; 2. producing oil microalgae; 3. mixing the algae solution; 4. shaking table; 5. and (4) flocculating constituent.
The specific implementation process is as follows: the method comprises the steps of preparing self-flocculating microalgae with a certain concentration into a self-flocculating microalgae suspension 1 which is uniformly dispersed, putting the self-flocculating microalgae suspension into an oil-producing microalgae solution 2 cultured by urban sewage, adding calcium and magnesium ions into a mixed algae solution 3, adjusting the pH value, putting the mixed algae solution on a shaking table 4 for flocculation reaction, and separating a flocculating constituent 5 from the urban sewage by using filter cloth after flocculation is finished. In a specific embodiment, the self-flocculating microalgae is one or more of filamentous algae, astrophyta, fusarium and scenedesmus which are cultured in municipal sewage and are easy to settle. In a specific embodiment, the oil-producing microalgae is one or more of chlorella, scenedesmus obliquus, crescenta closterium and dunaliella salina obtained by mutagenesis, domestication and screening.
The method has wide application range. In the specific embodiment, the self-flocculating algae liquid is made into uniformly distributed suspension by a dispersion machine, the rotation speed of the dispersion machine is 1000-1500rpm, and the adding amount is 0.06-0.10 g/L. In the specific embodiment, the formation of microalgae flocculating constituents is induced by regulating the pH of the mixed algae solution and adding calcium ions, magnesium ions and other conditions; the initial pH of the mixed algae solution is 8-10; the concentration of the added calcium and magnesium ions is 4-6 mmoL/L. In a specific embodiment, the shaking table is used for uniformly mixing the algae liquid and accelerating the formation of algae flocs, and the rotation speed of the shaking table is 120-140 rpm. In the specific embodiment, after the flocculation process is carried out for 6-12 hours, standing is carried out for 30min, and then algae-laden water separation is carried out by adopting 60-100-mesh filter cloth.
Example 1
The self-flocculating filamentous algae is cultured to a stationary phase (about 1g/L dry weight) by using municipal sewage, and a dispersion machine is used for forming a relatively uniform suspension at the rotating speed of 1000 rpm. Placing 90mL of scenedesmus obliquus solution cultured by urban sewage into a 150mL conical flask, and adding 10mL of the uniformly mixed self-flocculating filamentous algae suspension. The initial pH of the mixed algal solution was adjusted to 9 and the calcium ion concentration was 5mmoL/L, and the solution was placed on a shaker at 130rpm for 12 hours. Standing for 30min, and separating algae-laden water with 80-mesh filter cloth to obtain Scenedesmus obliquus with yield of 84%.
Example 2
The self-flocculating scenedesmus is cultured to a stationary phase (about 1g/L dry weight), and a dispersion machine is used for forming a relatively uniform suspension at the rotating speed of 1500 rpm. Putting 90mL of mixed chlorella cultured by urban sewage and scenedesmus obliquus into a 150mL conical flask, and adding 10mL of uniformly mixed self-flocculation scenedesmus suspension. The initial pH of the mixed algal solution was adjusted to 9 and the calcium ion concentration was 5mmoL/L, and the solution was placed on a shaker at 120rpm for 10 hours. After standing for 30min, the yield of the mixed liquid of the oil-producing chlorella and scenedesmus obliquus can reach 86%.
Comparative example 1
The depth of a settling pond is designed to be 10cm, the oily chlorella cultured in the urban sewage to reach the growth stabilization period naturally stands in the settling pond according to the gravilogy principle, the settling rate of microalgae cells is about 60% after 24 hours, and the microalgae body is small, so that disturbance and heavy suspension of the microalgae body are easily caused when supernatant is pumped out by a pump, and the yield of the microalgae is low.
Comparative example 2
The self-flocculating scenedesmus is cultured to a stationary phase (about 1g/L dry weight), and a dispersion machine is used for forming a relatively uniform suspension at the rotating speed of 1500 rpm. Putting 98mL of mixed chlorella cultured by urban sewage and scenedesmus obliquus into a 150mL conical flask, and adding 2mL of uniformly mixed self-flocculation scenedesmus suspension. The initial pH of the mixed algal solution was adjusted to 9 and the calcium ion concentration was 1mmoL/L, and the solution was placed on a shaker at 120rpm for 10 hours. After standing for 30min, the yield of the mixed liquid of the oil-producing chlorella and scenedesmus obliquus is 43 percent.
According to the results and the comparison results, the method for harvesting the oil-producing microalgae in the municipal sewage culture system by using the self-flocculating microalgae is constructed, the harvesting of the oil-producing microalgae by using the self-flocculating microalgae is safer and more environment-friendly compared with the conventional chemical method, and the method has the advantages of low cost and simplicity in operation compared with physical harvesting; meanwhile, the urban domestic sewage has high content of organic matters, nitrogen, phosphorus and other nutrient substances, is beneficial to mass propagation of microalgae, realizes the conversion of the sewage from pollutants to microalgae growth raw materials, and provides a technology with good industrial prospect for microalgae harvesting.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (2)
1. A method for harvesting oil-producing microalgae in a municipal sewage culture system by using self-flocculating microalgae is characterized in that the self-flocculating filamentous algae are cultured to a stationary phase by using the municipal sewage, the dry weight is 1g/L, and a dispersion machine is used for forming a relatively uniform suspension at the rotating speed of 1000 rpm; placing 90mL of scenedesmus obliquus solution cultured by urban sewage into a 150mL conical flask, and adding 10mL of uniformly mixed self-flocculating filamentous algae suspension; adjusting the initial pH of the mixed algae solution to 9, wherein the concentration of calcium ions is 5mmoL/L, and placing the mixed algae solution on a shaker at the rotating speed of 130rpm for mixing action for 12 h; standing for 30min, and separating algae and water with 80 mesh filter cloth.
2. A method for harvesting oil-producing microalgae in a municipal sewage culture system by using self-flocculating microalgae is characterized in that the self-flocculating filamentous algae are cultured to a stationary phase by using the municipal sewage, the dry weight is 1g/L, and a dispersion machine is used for forming a relatively uniform suspension at the rotating speed of 1500 rpm; putting 90mL of mixed chlorella liquid of chlorella cultured by urban sewage and scenedesmus obliquus into a 150mL conical flask, and adding 10mL of uniformly mixed self-flocculation scenedesmus suspension; adjusting the initial pH of the mixed algae solution to 9, wherein the concentration of calcium ions is 5mmoL/L, and placing the mixed algae solution on a shaker at the rotating speed of 120rpm for mixing action for 10 hours; standing for 30 min.
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| CN111908679A (en) * | 2020-07-16 | 2020-11-10 | 重庆工商大学 | Method for removing algae pollutants in water body by improving algae self-flocculation capacity |
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| Flocculation of Chlorella vulgaris induced by high pH: Role of magnesium and calcium and practical implications;Dries Vandamme et al;《Bioresource Technology》;20111231;第115页右栏最后一段至第116页左栏第一段 * |
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