JPH05301097A - Method for purification of treated sewage using microalgae and for simultaneous production of hydrocarbon - Google Patents

Abstract

PURPOSE:To provide a method for production of hydrocarbons with phytoplanktons by using treated sewage as the culture medium thereof to purify the treated sewage. CONSTITUTION:Microalgae which produce hydrocarbons such as Botryococcus br aunii, etc., are cultured in a treated sewage as the culture medium, and the hydrocarbons produced and accMulated by the phytoplanktons are recovered for use. The treated sewage used as the culture medium contains a smaller amt. of inorg. salts of nitrogen, phosphorus, etc., compared to the initial water quality because of the growth of the phytoplanktons. Thus, quality of the treated sewage is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hydrocarbons from sewage-treated water by using microalgae and purifying the sewage-treated water.

[0002]

2. Description of the Related Art Conventionally, when a hydrocarbon is produced by microalgae, an artificial synthetic medium has been used as a medium, and it has been necessary to prepare water and nutrient salts such as nitrogen and phosphorus. However, such a method is very difficult to put into practical use because the culture of microalgae becomes expensive in producing hydrocarbons. Also,
Although there have been attempts to purify sewage treated water with microalgae, microalgae that do not produce useful substances make it difficult to treat the obtained algal cells, and also economically disadvantageous because they do not produce useful substances. Is.

[0003]

The present invention differs from the above-mentioned conventional methods in that it makes effective use of sewage treated water, which is not effectively used by itself and is preferably purified when it is discarded. , To provide a method of purification.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a method for producing hydrocarbons by culturing a hydrocarbon-producing microalgae using sewage-treated water as a medium and reducing the inorganic substances in the sewage-treated water to improve its water quality is provided. To be done.

In the sewage treatment water in the present invention, in addition to general sewage treatment water, sewage discharged from ordinary households and factories is treated aerobically or anaerobically with microorganisms, etc. An aqueous solution in which the amount of organic substances and inorganic substances are reduced is included.

In order to carry out the method of the present invention, treated sewage water as it is, or aseptic treatment, pH and nutrients adjusted if necessary, may be used as a culture solution of microalgae producing hydrocarbons. Good. In this case, as the culturing method, supply of carbon dioxide by combustion exhaust gas, an optical fiber method, an air lift method, or the like can be used, and the culturing condition can be a condition suitable for each conventional microalgae. As the hydrocarbon-producing microalga, conventionally known ones can be used. Examples of such a product include Botrycoccus brauni ( Botrycoccus brauni).
i ) and the like.

By using the treated sewage water as a medium for microalgae producing hydrocarbons as described above,
Hydrocarbons can be produced efficiently, and at the same time, the sewage treatment water used for cultivation can have a lower concentration of inorganic substances than the original water quality. Examples of the inorganic substance include various inorganic salts containing nitrogen and phosphorus.

[0008]

INDUSTRIAL APPLICABILITY The present invention is constructed as described above, and can produce hydrocarbons from sewage-treated water by using microalgae, and at the same time improve the quality of sewage-treated water.

[0009]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The microalgae used in this example are Botryococcus bra
unii is a Berkeley strain. The sewage treatment water is sewage treatment water A and B obtained from two domestic wastewater sewage treatment plants in Ibaraki prefecture.

[0010] 25 ° C. Example 1 Chu13 medium, the B.braunii cultured under conditions that supplied the illuminance 3000 lux, 1% carbon dioxide, 2
The mixture was filtered through a nylon mesh of 0 μm mesh, washed with sewage-treated water A, and filtered. Then, the washed algal cells were transplanted into a 3 liter flask containing 3 liters of sewage-treated water that had been subjected to wet heat sterilization, and cultured under the above conditions. The freeze-dried weight of the resulting algal cells was 0.35 g, and the proportion of hydrocarbons extracted with hexane was 53%. The result of the culture is shown in FIG. The growth of B. braunii was measured as the amount of chlorophyll in the polygonal line 1 in FIG. 1, and finally the concentration was 2.8 times the initial amount. Line 2 shows the nitric acid concentration, but the initial concentration is 7.7.
6 Nmg / 1 was not detected on the 9th day of culture. Line 3 shows the phosphoric acid concentration, but the initial concentration is 0.015 Pm
The g / l decreased to 0.01 Pmg / l or less on the first day of culture.

Example 2 B. braunii cultivated in a Chu13 medium at 25 ° C. under the condition that an illuminance of 3000 lux and 1% of carbon dioxide were supplied were 2
The mixture was filtered through a nylon mesh of 0 μm mesh, washed with sewage-treated water B, and filtered. Then, the washed algal cells were transplanted into a 3 liter flask containing 3 liters of sewage-treated water that had been sterilized by wet heat, and cultured under the above conditions. The freeze-dried weight of the resulting algal cells was 0.34 g, and the proportion of hydrocarbons extracted with hexane was 40%. The results of culture are shown in FIG. The proliferation of B. braunii was measured as the amount of chlorophyll in the polygonal line 1 in FIG. 2, and finally the concentration was 2.8 times the initial amount. Line 2 shows the nitric acid concentration, but the initial concentration is 4.4.
8 Nmg / l was no longer detected on day 7 of culture.
Line 3 shows the phosphoric acid concentration, but the initial concentration is 0.29 Pm
The g / l decreased to 0.01 Pmg / l or less on the 5th day of culture.

Comparative Example 1 B. braunii cultivated in a Chu13 medium at 25 ° C. under the condition that an illuminance of 3000 lux and 1% of carbon dioxide were supplied were 2
The mixture was filtered through a 0 μm mesh nylon mesh, washed with Chu 13 medium, and filtered. Then, the washed algal cells were transplanted into a 3 liter flask containing 3 liters of Chu13 medium that had been sterilized by heat and humidity, and cultured under the above conditions. The freeze-dried weight of the resulting algal cells was 1.34 g, and the ratio of hydrocarbons extracted with hexane was 58%. The result of the culture is shown in FIG. The proliferation of B. braunii was measured as the amount of chlorophyll on polygonal line 1 and finally reached a concentration of 22 times. Line 2 shows the nitric acid concentration, but the initial concentration is 32.1 Nmg /
1 was not detected on the 25th day of culture. Line 3 shows the phosphoric acid concentration, but the initial concentration of 6.64 Pmg / l decreased to 4.21 Pmg / l on the 25th day of culture.

[Brief description of drawings]

FIG. 1 is a graph showing the culture results of Example 1.

FIG. 2 is a graph showing the culture results of Example 2.

FIG. 3 is a graph showing the culture results of Comparative Example 1.

[Explanation of symbols]

 1 Polygonal line showing chlorophyll concentration 2 Polygonal line showing nitric acid concentration 3 Polygonal line showing phosphoric acid concentration

[Procedure amendment]

[Submission date] March 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The microalgae used in this example are Botryococcus bra
unii . The sewage treatment water is sewage treatment water A and B obtained from two domestic wastewater sewage treatment plants in Ibaraki prefecture.

Claims (1)

[Claims] 1. A method for producing a hydrocarbon by culturing a hydrocarbon-producing microalgae using sewage-treated water as a medium to reduce the amount of inorganic substances in the sewage-treated water and improve its water quality.