WO2014038753A1 - Method for cultivating and harvesting adhesive microalgae from sewage or waste water to utilize same as biomass - Google Patents

Abstract

The present invention relates to a method for readily converting adhesive microalgae contained in sewage or waste water into biomass, and more specifically, to a method for utilizing adhesive microalgae as biomass at a high efficiency and at low costs by vertically installing a dimensional medium for adhesion of a mesh structure in sewage or waste water before being discharged, carrying out cultivation for a predetermined time period to allow the adhesive microalgae existing in the sewage or the waste water to adhere to the medium for adhesion and grow, and only lifting the medium for adhesion so as to simply and rapidly harvest microalgae without other processes.

Description

Method of cultivating and harvesting adherent microalgae from sewage water to use as biomass

The present invention relates to a technology that can be easily cultured and harvested adherent microalgae contained in the sewage water can be utilized as biomass.

Limited fossil energy resources are being depleted due to the explosive increase in energy demand due to industrialization and population growth, which is a global issue. Accordingly, development of alternative energy resources is urgently needed to meet the increasing energy demand. Recently, biodiesel production using microalgae has been attracting much attention as a raw material of alternative energy resources. Microalgae are photosynthetic microorganisms that fix carbon dioxide to reduce greenhouse gases in the atmosphere, and can be cultured in non-cultivated land using sewage and wastewater, and are non-food resources, and biomass production and lipid production per unit area are terrestrial plants. It is much higher than that.

Microalgae grows rapidly, and biodiesel can be produced from microalgae biomass because it is synthesized and stored as 20 ~ 50% of neutral lipid in neutral lipids. In addition, since microalgae use photosynthesis using solar energy and carbon dioxide in the atmosphere, it has emerged as an alternative that can simultaneously solve the reduction effect of atmospheric carbon dioxide and greenhouse gases, which are the main causes of global warming.

The discharge of sewage and wastewater containing high concentrations of organic matter and inorganic substances such as phosphorus and nitrogen is a major factor in eutrophication. By cultivating microalgae using nutrients contained in sewage and wastewater as nutrients necessary for the growth of microalgae, such a global problem can be solved. Cultivation of microalgae using sewage and wastewater can simultaneously produce microalgae biomass for the treatment of biological sewage and wastewater and the production of biodiesel. In addition, treatment of wastewater using microalgae is an environmentally friendly process that does not generate secondary pollutants, if all of the generated biomass is used. Treatment of wastewater at the same time as cultivation with wastewater of various types of microalgae , such as Chlorella, Scenedesmus, Phormidium, Botryococcus, Chlamydomonas, and Spirulina , has been reported (Rawat et al. Applied Energy 88: 3411-3424. 2011).

Microalgae cultivation is divided into raceway pond and photobioreactor. For the mass cultivation of microalgae, a raceway pond is much less expensive than a photobioreactor and has the advantage of being easily installed. However, the method has low productivity per unit area of the microalgae, and the depth of the raceway pond is about 30 cm or less in order to prevent light shortage when the microalgae are cultured. In addition, it is difficult and expensive to harvest cultured unicellular or floating microalgae for the discharge of sewage and wastewater and the use of microalgal biomass.

Accordingly, the present inventors completed the present invention by developing a technology that can be utilized as biomass energy by culturing and harvesting microalgae with high efficiency from sewage and wastewater to overcome the problems of the prior art and produce microalgae-derived biodiesel. It was.

Accordingly, an object of the present invention is to provide a method of increasing the processing capacity of microalgae per unit area and providing a technique for culturing and harvesting microalgae at low cost and increasing biomass energy production efficiency.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problem, another task that is not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the object of the present invention as described above, the present invention provides a method for utilizing the adherent microalgae as a biomass, comprising the following steps: 1) vertically attached to the sewage storage Culturing the sex microalgae; 2) harvesting the cultured adherent microalgae by simply lifting the attachment medium; And 3) drying the harvested adherent microalgae for use as biomass energy.

In one embodiment of the present invention, the attachment medium may be made of a frame 10, a mesh 20, and a hook hole 30.

In another embodiment of the present invention, the frame may be acrylic or aluminum.

In another embodiment of the present invention, the mesh may be a material selected from the group consisting of polyester, stainless steel, acrylic, nylon, and polyurethane.

In another embodiment of the present invention, the mesh may be made of stainless steel or nylon.

In another embodiment of the present invention, the drying may be natural drying or lyophilization.

In another embodiment of the present invention, the method can remove nutrients from the wastewater by using nutrients for the growth of adherent microalgae.

In the present invention, by culturing adherent microalgae in sewage and wastewater, nutrients in sewage and wastewater can be removed, and the cultured adherent microalgae can be easily harvested to improve biomass (biofuel) and lipid production efficiency. There is an effect that can be increased.

In addition, the present invention can improve the productivity of microalgae by increasing the area that can be attached to the microalgae per unit area by using the attachment medium, and because the adhered microalgae grows by attaching to the attachment medium, sunlight can transmit more deeply. In order to cultivate different microalgae optimized for each light from high light to low light, there is an advantage that can treat a larger amount of wastewater than conventional.

In addition, cultivation of adherent microalgae using sewage and wastewater increases the removal rate of nitrogen and phosphorus as compared to the cultivation method of floating microalgae, thereby satisfying the discharge standard of the discharged water and reducing the eutrophication of the discharged water. The green algae can be suppressed, and the culture medium itself remains transparent, so that the sewage of nitrogen and phosphorus-free sewage can be discharged without any special harvesting process.

Figure 1 shows the difference in the adhesion rate of the microalgae according to the type, luminous intensity, and flow rate of the attachment medium.

Figure 2 shows the difference in transparency between the adherent microalgae culture tank (A) and the floating microalgae culture tank (B).

Figure 3 shows the light transmittance difference between the adherent microalgae culture and the floating microalgae culture tank.

Figure 4 compares the biomass productivity per unit area of floating microalgae and adherent microalgae.

Figure 5 compares the removal rate of nutrients in suspended microalgae and adherent microalgae.

Figure 6 shows the culture, harvesting and drying of adherent microalgae.

Figure 7 shows a comparison of fatty acid composition of microalgae after natural drying and lyophilization.

Figure 8 schematically shows the attachment medium of the present invention (10: frame, 20: mesh, 30: hook hole).

[Description of the code]

10 frame 20 net

30: hook hole

The present inventors have studied to improve light shortage and low productivity, which are disadvantages in conventional microalgae cultivation, and as a result, it is possible to harvest microalgae that can be utilized as biomass even at low cost. The present invention was completed by developing a method for culturing and harvesting adherent microalgae using an attachment medium in wastewater.

Attached microalgae has a large number of diatoms and filamentous algae, so it grows well even at relatively low water temperatures, so there is an advantage that the microalgae can be used as bioenergy by cultivating and harvesting microalgae even in autumn or spring when the water temperature is low.

In order to cultivate and harvest the adherent microalgae having the above advantages with high efficiency, a polycarbonate plate, a nylon mesh, a stainless mesh, and an OHP are used as an attachment medium. The adhesion rate of adherent microalgae was used according to the type of medium, and the difference of the flow rate of the raceway pond and the adhesion rate according to the presence or absence of light were compared. It was found that the rate was the highest, and it was confirmed that the adhesion rate of the adherent microalgae could be increased under conditions exposed to light (see Example 1).

In addition, the present inventors cultivated the adherent microalgae by vertically installing a nylon mesh as an attachment medium in a raceway pond containing effluent from the sewage treatment plant, and when culturing floating microalgae More excellent transparency of the culture tank can increase the unit production of microalgae, nutrients such as nitrogen and phosphorus in the sewage is used to remove and remove the microalgae, and after cultivation simply contains a medium for attachment It was confirmed that the harvesting can be easily performed by raising (see Example 2). That is, it is designed to increase productivity by installing the attachment medium vertically and vertically (see FIG. 2A) when culturing microalgae in a channel-type pond (see FIG. 2A), and by increasing the area of the attachment medium per planar unit area of the culture tank. It was to reduce the additional site area for microalgal culture. In addition, by simply lifting the attachment medium as described above after the microalgae cultivation, it is possible to harvest simply and quickly without any other processing.The attachment medium on which the harvested microalgae are cultured is placed in the sun or in a dryer or connected to a connecting line. It can be easily dried at low cost by hanging and drying, so that the economic effect is excellent.

Accordingly, the present invention may provide a method for utilizing the adherent microalgae as a biomass comprising the following steps:

1) culturing the adherent microalgae by vertically installing the attachment medium in the sewage storage;

2) harvesting the cultured adherent microalgae by simply lifting the attachment medium; And

3) drying the harvested adherent microalgae for use as biomass energy.

The "attachment medium" of the present invention consists of a frame 10, a mesh 20, and a hook hole 30 (see FIG. 8), which is shaped like a window frame, preferably acrylic or aluminum It may be made of a material such as, but can be used without being limited to those that can support the net. In addition, the mesh may preferably be a material such as polyester, stainless steel, acrylic, nylon, or polyurethane, and more preferably stainless steel or nylon may be used, but is not limited thereto. Any material that can be made into a net that can grow can be used.

In addition, when the dried microalgae harvested by the present inventors are dried for use as biomass energy, a method of freeze-drying and freeze-drying in sunlight to see if fatty acid loss occurs according to the drying method As a result, fatty acid content (particularly, palmitic acid content) increased when it was naturally dried in sunlight than freeze-drying, and it was confirmed that the natural drying method is more suitable for use as biomass energy such as biodiesel. (See Example 2).

Accordingly, the adherent microalgae according to the method of the present invention may preferably be dried by natural drying or lyophilization, and most preferably by natural drying in sunlight, but is not limited thereto. .

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the following examples.

Example 1

Establishment of adherent microalgal culture conditions

In order to establish the optimum culture conditions for utilizing microalgae as biomass energy, the present inventors have established the adhesion rate of adherent microalgae according to the type of medium, the flow rate in a raceway pond, and the presence or absence of light. The difference was compared. Polycarbonate plates, nylon mesh, stainless mesh, and OHP film are used as attachment media, respectively, and the light is present when the flow rate is fast or slow. The difference in adhesion rate according to (Light or Dark) was compared.

As a result, as shown in Figure 1, the adhesion rate is low regardless of the flow rate or the light in the medium that is water-resistant, such as polycarbonate and OHP film among the four adhesion medium, stainless steel mesh and nylon mesh In, the adhesion rate of the adherent microalgae was markedly high.

In addition, the flow rate in the channel pond did not significantly affect the adhesion rate of adherent microalgae, but the difference in adhesion rate with or without light appeared to be large. That is, it was confirmed that the adhesion rate of the adhesive microalgae was significantly higher than the light blocking condition.

From the above, the adherent microalgae can be cultured with high efficiency in the net material, especially stainless steel net or nylon net, and it has been confirmed that the light transmittance has a great influence on the culture efficiency. You can see that it is important.

Example 2

Adherent Microalgae Cultivation and Harvesting for Conversion to Biomass

The present inventors operate a 5-ton raceway pond using the discharged water from the sewage treatment plant and harvest the adherent microalgae according to the method of the present invention. Since it was incubated at room temperature in November-December, the water temperature was maintained below 10 degrees, and total nitrogen and total phosphorus concentrations were maintained at approximately 10-15 mg-N / L and 0.1-2 mg-P / L levels, respectively. It allowed species to grow naturally already present in sewage without inoculating certain species. Two water channel ponds were operated as a control and a treatment, which allowed the floating microalgae to grow without the attachment medium, and the treatment was installed vertically and vertically with a nylon mesh in the culture medium (effluent). Adherent microalgae were attached to the medium and allowed to grow, and the waterway pond was operated in a semi-continuous culture, replacing one fifth of the total capacity with fresh effluent daily. Total nitrogen, total phosphorus, total dissolved nitrogen, total dissolved phosphorus concentration, chlorophyll-a, and microalgae dry weight were measured at intervals of 3 to 4 days, and nitrogen, phosphorus removal rate, and biomass productivity were calculated and compared. .

As a result, as shown in Figure 2, the transparency of the adherent microalgae culture tank (treatment) was higher than that of the floating microalgae culture tank (control), and the bottom was clear. In addition, as shown in Figure 3, the light transmittance of the adherent microalgae and the floating microalgae culture tank is not significantly different from the light transmittance of the total light amount on the water surface, when looking at the light transmittance at the bottom, floating microalgae At the bottom of the culture tank, the light transmittance was about 5% between 4 to 10 days and after 10 days of culture, the light transmittance was very low, while the light transmittance at the bottom of the adherent microalgal culture tank was 10 to 20%. The light transmittance between the adhesion medium is 10 to 5%, indicating that the light transmittance is much higher than that of the floating microalgal culture tank, and the amount of light between the adhesion medium after 10 days of culture is 82 to 55 μmol photon m ^{−. 2} s ^-1 is much higher than the floating (2 ~ 24 μmol photon m ^-2 s ^-1 ), it can be seen that sufficient light is supplied for the growth of microalgae.

As a result of comparing the productivity of biomass per unit area, as shown in FIG. 4, when the daily productivity was calculated by the slope value, the adherent microalgae was 12.1 g / m ² / day, and the floating microalgae was 1.8. g / m ² / day showed much higher productivity of adherent microalgae.

As a result of analysis of nitrogen removal rate and phosphorus removal rate, as shown in FIG. 5, in the case of nitrogen removal rate, the adherent microalgae was 31.2% on average, and the floating microalgae was 20.5% on average, and there was a difference in the case of phosphorus removal rate. The average value of adherent microalgae was 77.4% and that of suspended microalgae was 33.3%, which was more than double.

In addition, as shown in Figure 6, by simply lifting the attachment medium after incubation in the attached algae culture tank, the microalgae was harvested simply and quickly without any other processing step, and the microalgae attached medium on the connected line and dried It was. In the case of natural drying in sunlight, the drying time may be different depending on the weather, but on average, it is completely dried in two to three days with it attached to the medium. As a result of comparing the fatty acid composition after drying the microalgae harvested using the method of natural drying and freeze-drying in sunlight, as shown in Figure 7, the fatty acid content of the biomass naturally dried in sunlight using an adhesion medium The conventional freeze-drying method showed a 16% increase in the content of palmitic acid (C16: 0) compared to the fatty acid content of the dried biomass, confirming that the natural drying method in the sun light has a more suitable fatty acid composition for biodiesel production. It was.

From the above, by culturing the adherent microalgae according to the method of the present invention can remove the nutrients of the wastewater, the cultured adherent microalgae can be easily harvested, useful for producing biomass by natural drying in sunlight It can be used to make it easy.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

The adhesive microalgae culturing method of the present invention enables the cultivation of microalgae using sewage water, and can be used for treating green algae from sewage water because it can remove nutrients from the wastewater with higher efficiency than the floating culture method. In addition, the lipid production efficiency is increased, which can be useful for producing biomass energy.

Claims (7)

1. Method for utilizing the adherent microalgae as biomass comprising the following steps:

   1) culturing the adherent microalgae by vertically installing the attachment medium in the sewage storage;

   2) harvesting the adherent microalgae cultured by lifting the attachment medium; And

   3) drying the harvested adherent microalgae for use as biomass energy.
2. The method of claim 1,

   The attachment medium is characterized in that it consists of a frame (10), a mesh (20), and a hook hole (30).
3. The method of claim 2,

   Wherein the frame is acrylic or aluminum.
4. The method of claim 2,

   Wherein said mesh is a material selected from the group consisting of polyester, stainless steel, acrylic, nylon, and polyurethane.
5. The method of claim 2,

   Wherein said mesh is made of stainless steel or nylon.
6. The method of claim 1,

   Wherein said drying is natural drying or lyophilization.
7. The method of claim 1,

   The method is characterized in that the nutrients are removed from the wastewater by using the nutrients for the growth of adherent microalgae.

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