Mass algal culture system

• US 4,253,271 A
• Filed: 12/28/1978
• Issued: 03/03/1981
• Est. Priority Date: 12/28/1978
• Status: Expired due to Term

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Raymond, Lawrence P.
• Primary Examiner(s): Bagwill, Robert E.
• Application Number:
  US05/974,051
• Time in Patent Office: 796 Days
• Field of Search: 47/1.4, 47/59-65, 210/44, 210/221 P, 210/3
• US Class Current: 47/1.4
• CPC Class Codes: A01G 9/243 Collecting solar energy in general F24S
• CPC Class Codes: C12M 21/02 Photobioreactors culturing algae A01G33/00, A01H4/001, C12N1/12
• CPC Class Codes: C12M 29/18 External loop; Means for reintroduction of fermented biomass or liquid percolate loop type reactors for chemical or physical processes B01J19/2435
• CPC Class Codes: C12M 33/00 Means for introduction, transport, positioning, extraction, harvesting, peeling or sampling of biological material in or from the apparatus chemical or physical laboratory apparatus in general B01L, devices for taking cell samples A61B10/0045, withdrawing or distributing predetermined quantities of fluid B01L99/00
• CPC Class Codes: C12M 37/00 Means for sterilizing, maintaining sterile conditions or avoiding chemical or biological contamination C12M23/38 takes precedence; filtration in general and filters per se B01D24/00-B01D41/00; autoclaves B01J3/04; treatment of microorganisms with electrical or wave energy C12N13/00
• CPC Class Codes: C12M 41/02 of foam foam prevention during gasification of liquids B01D19/02
• CPC Class Codes: C12M 41/26 of pH
• CPC Class Codes: C12N 1/12 Unicellular algae; Culture media therefor as new plants A01H13/00
• CPC Class Codes: Y02A 40/25 Greenhouse technology, e.g. cooling systems therefor
• CPC Class Codes: Y02P 60/12 using renewable energies, e.g. solar water pumping
• CPC Class Codes: Y10S 47/06 Plant growth regulation by control of light thereon

Abstract

An apparatus and process for the culture of algae in a liquid medium is disclosed. The medium circulates through an open trough and is exposed to an atmosphere which is temperature regulated. The nutrient content of the liquid medium is regulated to control the chemical composition growth and reproduction characteristics of the cultured algae. Before it is allowed to strike the medium, sunlight is passed through a filter to remove wavelengths which are not photosynthetically active. Heat energy can be recovered from the filter.

Claims

1. A gas lift pump mechanism for circulating a liquid medium containing an algal culture and for facilitating the separation of suspended substances from said liquid medium comprising:

a substantially vertical stand pipe having a liquid medium inlet and a medium outlet located above said inlet;

first gas inlet means for introducing a sufficient volume of gas into liquid medium inside said pipe to cause said medium to rise therein; and

second gas inlet means, separate from said first gas inlet means, for introducing a stream of minute gas bubbles into said liquid medium inside said pipe which bubbles adhere to suspended substances in said liquid medium and increase the buoyancy of said substances.

2. The pump mechanism of claim 1 further comprising heat exchange means associated with said vertical stand pipe to adjust the temperature of liquid medium as it moves through said pipe.

3. The pump mechanism of claim 1 wherein said first and second gas inlet means are located at different elevations inside said stand pipe.

4. The pump mechanism of claim 3 wherein said first gas inlet means is located above said second gas inlet means.

5. The pump mechanism of claim 1 further comprising:

means for supplying a stream of air to said first gas inlet means and

means for supplying a stream of CO₂ to said second gas inlet means.

6. A process for separately removing impurity substances and suspended algal cells from a continuously recirculating liquid algal culture medium which contains said impurity substances and said cells, said process comprising:

bringing algal cells and impurity substances carried in a continuously recirculating liquid medium into contact with gas bubbles to increase the buoyancy of said cells and of said impurity substances;

moving said liquid medium through a trough at such a rate that the gas bubbles carry relatively small and light impurity substances to the surface of said medium and that said algal cells, which are relatively large and heavier, and which have adsorbed said gas bubbles but are carried downstream by the current and do not rise to said surface;

removing said light impurity substances from said surface at a first location along said trough;

at a second location downstream of said first location, reducing the rate at which said liquid medium moves through said trough so that algal cells with adsorbed gas bubbles rise to said surface at said second location; and

removing a fraction of the algal cells circulating in said medium from said surface at said second location.

7. The process of claim 6 wherein the impurity substances comprise dissolved organic substances which, when contacted with gas bubbles, form a foam that rises to the surface of the medium.

8. A system for mass culture of algae comprising:

a trough defining a channel which is substantially horizontal;

circulation means for moving a flow of an aqueous nutrient medium innoculated with unicellular algae through said channel from one end thereof to the other comprising a gas lift pump having a substantially vertical stand pipe with a medium inlet, a medium outlet located above said inlet and means for introducing a sufficient volume of gas into the aqueous medium inside said stand pipe to cause said medium to rise therein;

said outlet comprising means for separating froth from said medium, delivering said medium to said channel and discharging said froth;

gas-liquid contact means within said gas lift, and separate from said aforementioned means for introducing gas, for bringing algal cells in said medium into contact with minute bubbles containing a substantial proportion of carbon dioxide which bubbles adhere to said cells causing them to rise to the surface of said medium in said trough;

harvesting means for removing said cells from said surface, said harvesting means being located in said trough downstream of said gas lift pump; and

discharge means for said medium connected to said channel downstream of said harvesting means.

9. A system as defined in claim 8 and comprising means for reducing the rate of flow of said medium adjacent said harvesting means to facilitate rise of said algal cells.

10. A system as defiend in claim 8 wherein said harvesting means is located at the opposite end of said trough from said gas lift.

11. A system as defined in claim 10 wherein said discharge means for said medium is connected to said inlet of said gas lift to recirculate said medium.

12. A system for mass culture of microalgae comprising:

a trough having inlet and discharge ends;

an aqueous medium precursor in said trough, said medium precursor comprising sea water in which is dissolved a mixture of nutrient salts which consist essentially of HNO₃, H₃ PO₄, KCl, Na₂ EDTA, and trace amounts of FeCl₃.6H₂ O, (NH₄)₆ Mo₇ O₂₄.4H₂ O, H₃ BO₃, ZnCl₂, CuCl₂.2H₂ O and MnCl₂.4H₂ O;

an amount of KOH sufficient to adjust the pH of said solution to within a range which facilitates a desired reproduction and growth pattern for a selected algal species and to complete an aqueous medium suitable for the culture of said algal species and to fill said trough to a shallow depth;

walls defining an enclosed gas space above the surface of said aqueous medium precursor;

a gas lift pump to circulate said liquid medium through said trough, said pump comprising a substantially vertical stand pipe having a medium inlet, a medium outlet located above said inlet and means for introducing sufficient gas into aqueous medium inside said pipe to cause said medium to rise therein and separate means for introducing minute gas bubbles comprising substantial amount of carbon dioxide into aqueous medium inside said pipe to increase the buoyancy of organic substances and of microalgae in said medium by adsorption of said minute gas bubbles, said inlet and outlet being connected to said trough at locations adjacent said discharge and inlet ends respectively so that circulation of said medium in said trough from said inlet end toward said discharge end is facilitated;

a source of carbon dioxide;

tubing means connected between said means for injecting a stream of minute bubbles and said source of carbon dioxide, for directing a flow of carbon dioxide from said source into said liquid medium;

skimming means for skimming off organic substances raised to the surface of said medium due to adsorption onto minute bubbles in said stand pipe;

harvesting means for skimming off microalgae raised to the surface of said medium;

a container comprising two substantially transparent panels which are closely spaced and joined together to define a water-tight compartment therebetween, said container being positioned such that sunlight passes through said panels and subsequently strikes said medium circulating through said trough;

an aqueous CuSO₄ solution contained in said compartment to serve as a filter which adsorbs infrared and ultraviolet radiation of said light;

mixing means for causing said medium to travel through said trough in a turbulent manner so that individual algal cells are alternately positioned in portions of said medium distant and adjacent to said light source and thus are alternately exposed to maximum intensity light when in said adjacent portion and decreasing light intensity at progressively more distant portions;

means for maintaining the temperature of said aqueous medium within a range conducive to the growth and reproduction of said algal species;

means for extracting heat energy from said CuSO₄ solution; and

means for replenishing nutrient salts in said medium as they are consumed by said microalgae so that sufficient nutrients are maintained to sustain desired algal growth and reproduction rates.

13. A continuous process for mass culture of a selected species of marine microalgae comprising:

filling an algal culture container with a liquid culture medium precursor comprising sea water in which is dissolved a mixture of nutrient salts which consists essentially of HNO₃, H₃ PO₄, KCl, Na₂ EDTA, and trace amounts of FeCl₃.6H₂ O, (NH₄)₆ Mo₇ O₂₄.4H₂ O, H₃ BO₃, ZnCl₂, CuCl₂.2H₂ O and MnCl₂.4H₂ O;

adding an amount of KOH to said precursor sufficient to adjust its pH to a level which facilitates a desired reproduction and growth pattern for a selected algal species and to complete said precursor'"'"'s nutrient content whereby a liquid medium suitable for the growth of said algal species is formed;

innoculating said medium with a culture of said algal species;

circulating said innoculated medium through an open trough of shallow depth by withdrawing medium from one end of the trough and replacing it in the other end;

maintaining the temperature of said innoculated medium within a range conducive to the growth and reproduction of said algal species;

channeling the flow of innoculated medium from said one end of said trough through the vertical stand pipe of a gas lift pump mechanism equipped for the introduction of minute gas bubbles comprising substantial amounts of carbon dioxide into liquid medium passing therethrough to;

a. accomplish said circulating; and

b. bring organic substances and the cells of said algal culture into contact with a stream of minute gas bubbles which are adsorbed thereon to increase the buoyancy of said organic substances and said microalgae so that they tend to rise to the surface of medium in the trough;

moving liquid medium containing dissolved organic substances and algal cells with adsorbed minute gas bubbles through said trough at a rate such that the relatively small and light organic substances with adsorbed gas bubbles rise to the surface of said medium and the relatively large and heavier algal cells with adsorbed gas bubbles are carried by the current and not allowed to rise to said surface;

skimming said organic substances from said surface;

subsequently slowing the rate at which said liquid medium moves through said trough so that algal cells with adsorbed gas bubbles rise to said surface;

skimming algal cells from said surface;

exposing the surface of medium in the trough to sunlight which has been filtered sufficiently to facilitate the photosynthesis of the microalgae by removing light wavelengths which inhibit algal growth and reproduction, while transmitting photosynthetically active wavelengths;

alternately positioning individual cells of the algae in portions of said medium distant and adjacent to said medium surface and thus alternately exposing the cells to maximum light intensity when adjacent to said surface and decreasing light intensity when progressively more distant from said surface;

replenishing nutrient salts in the medium as they are consumed by said microalgae so that sufficient nutrients are maintained in said medium to sustain desired algal growth and reproduction rates; and

injecting CO₂ into said medium in sufficient quantity to maintain a desired alkalinity and nutrient carbon content in said medium.

14. A system for mass culture of marine microalgae comprising:

a trough having inlet and discharge ends;

an aqueous medium precursor in said trough, said medium precursor comprising sea water in which is dissolved a mixture of nutrient salts which, in grams per 100 liters of sea water, consist essentially of 50.7 g. HNO₃ 7.8 g. H₃ PO₄, 4.3 g. KCl, 1.86 g. Na₂ EDTA, 0.020 g. FeCl₃.6H₂ O, 0.00368 g. (NH₄)₆ Mo₇ O₂₄.4H₂ O, 0.00105 g. H₃ BO₃, 0.00040 g. ZnCl₂, and lesser amounts of both CuCl₂.2H₂ O and MnCl₂.4H₂ O;

an amount of KOH sufficient to adjust the pH of said solution to within a range which facilitates a desired reproduction and growth pattern for a selected marine algal species and to complete an aqueous medium suitable for the culture of said algal species and to fill said trough to an average running depth between 0.5 and 5.0 cm.;

walls defining an enclosed gas space above the surface of said aqueous medium precursor;

a gas lift pump to circulate said liquid medium through said trough, said pump comprising a substantially vertical stand pipe having a medium inlet, a medium outlet located above said inlet and means for introducing a stream of gas bubbles into aqueous medium inside said pipe to cause said medium to rise therein and means for injecting a stream of minute gas bubbles into aqueous medium inside said pipe to increase the buoyancy of organic substances and of microalgae in said medium by adsorption of said minute gas bubbles, said inlet and outlet being connected to said trough at locations adjacent said discharge and inlet ends respectively so that circulation of said medium in said trough from said inlet end toward said discharge end is facilitated;

a source of carbon dioxide;

tubing means connected between said means for injecting a stream of minute bubbles and said source of carbon dioxide, for directing a flow of carbon dioxide from said source into said liquid medium;

skimming means for skimming off organic substances raised to the surface of said medium due to adsorption onto minute bubbles in said stand pipe;

harvesting means for skimming off microalgae raised to the surface of said medium;

a container comprising two substantially transparent panels which are closely spaced and joined together to define a water tight compartment therebetween, said container being positioned such that sunlight passes through said panels and subsequently strikes said medium circulating through said trough;

an aqueous CuSO₄ solution contained in said compartment to serve as a filter which adsorbs infrared and ultraviolet radiation of said light;

mixing means for causing said medium to travel through said trough in a vortical path so that individual algal cells are alternately positioned in portions of said medium distant and adjacent to said light source and thus are alternately exposed to maximum intensity light when in said adjacent portion and decreasing light intensity at progressively more distant portions;

means for maintaining the temperature of said aqueous medium within a range conducive to the growth and reproduction of said algal species;

means for extracting heat energy from said CuSO₄ solution; and

means for replenishing nutrient salts in said medium as they are consumed by said mocroalgae so that sufficient nutrients are maintained to sustain desired algal growth and reproduction rates.

15. A continuous process for mass culture of a selected species of marine microalgae comprising:

filling an algal culture container with a liquid culture medium precursor comprising sea water in which is dissolved a mixture of nutrient salts which, in grams per 100 liters of sea water, consists essentially of 50.7 g. HNO₃, 7.8 g. H₃ PO₄, 4.3 g. KCl. 1.86 g. Na₂ EDTA, 0.020 g. FeCl₃.6H₂ O, 0.00368 g. (NH₄)₆ Mo₇ O₂₄.4H₂ O, 0.00105 g. H₃ BO₃, 0.00040 g. ZnCl₂, and lesser amounts of both CuCl₂.2H₂ O and MnCl₂.4H₂ O;

adding an amount of KOH to said precursor sufficient to adjust its pH to a level which facilitates a desired reproduction and growth pattern for a selected marine algal species and to complete said precursor'"'"'s nutrient content whereby a liquid medium suitable for the growth of said marine algal species is formed;

innoculating said medium with a culture of said algal species;

circulating said innoculated medium through an open trough at an average depth of between 0.5 and 5.0 cm. by withdrawing medium from one end of the trough and replacing it in the other end;

maintaining the temperature of said innoculated medium within a range conducive to the growth and reproduction of said algal species;

channeling the flow of innoculated medium from said one end of said trough through the vertical stand pipe of a gas lift pump mechanism equipped for the injection of minute gas bubbles into liquid medium passing therethrough to;

a. accomplish said circulating; and

b. bring organic substances and the cells of said algal culture into contact with a stream of minute gas bubbles which are adsorbed thereon to increase the buoyancy of said organic substances and said microalgae so that they tend to rise to the surface of medium in the trough;

moving liquid medium containing dissolved organic substances and algal cells with adsorbed minute gas bubbles through said trough at a rate such that the relatively small and light organic substances with adsorbed gas bubbles rise to the surface of said medium and the relatively large and heavier algal cells with adsorbed gas bubbles are carried by the current and not allowed to rise to said surface;

skimming said organic substances from said surface;

subsequently slowing the rate at which said liquid medium moves through said trough so that algal cells with adsorbed gas bubbles rise to said surface;

skimming algal cells from said surface;

exposing the surface of medium in the trough to sunlight which has been filtered by passage through a thin layer of an aqueous solution consisting essentially of water in which is dissolved an amount of CuSO₄.5H₂ O sufficient to facilitate the photosynthesis of the microalgae by removing at least ninety-nine percent of all radiation below 350 nanometers and above 700 nanometers from the incident sunlight;

alternately positioning individual cells of the algae in portions of said medium distant and adjacent to said medium surface and thus alternately exposing the cells to maximum light intensity when adjacent to said surface and decreasing light intensity when progressively more distant from said surface;

replenishing nutrient salts in the medium as they are consumed by said microalgae so that sufficient nutrients are maintained in said medium to sustain desired algal growth and reproduction rates; and

injecting into said medium at least 235 g. of CO₂ per 100 liters of medium per day.