Method for treating dense deepwater from Lake Kivu
First Claim
1. A method for treating water extracted from Lake Kivu, said method comprising the steps of:
- (a) extracting water from an extraction depth of Lake Kivu to obtain extracted water;
(b) degassing the extracted water so as to remove at least a portion of carbon dioxide gas from the extracted water and provide degassed water having a density lower than the extracted water and having a pH higher than the extracted water;
(c) photosynthetic treatment of the degassed water by growth of an algal biomass to convert bicarbonate anions to carbon dioxide and hydroxyl anions, such that the pH of the degassed water is increased and magnesium and calcium precipitate out of the degassed water to provide de-densified water and precipitate;
(d) separating the de-densified water from the algal biomass and the precipitate;
(e) optionally adjusting the pH of the de-densified water by adding carbon dioxide thereto, wherein the carbon dioxide is obtained from the degassing step and by combustion of methane also obtained in the degassing step; and
(f) reinjecting into Lake Kivu a return flow of the de-densified water separated from the biomass and precipitate, wherein the de-densified water is reinjected into Lake Kivu at a reinjection depth which is shallower than the extraction depth and which is density-matched with the de-densified water.
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Abstract
A method and system are disclosed for total degassing (CH4+CO2) and density-reducing treatment of dense Lake Kivu deepwater. The invention allows hyper-efficient oxyfuel power generation with return flow water reinjection density-matched at or above ˜150 m without necessity to admix biozone (<80 m) water. This increases the CH4 resource and deflates the gas-rich deepwater layer over time, making Lake Kivu safe against a catastrophe threatening up to 2 million lives. Deepwater from the Main Resource Zone (MRZ, ˜480 m to ˜260 m) is de-densified, then reinjected above the Potential Resource Zone (PRZ, ˜260 m to ˜180 m) within the Intermediate Zone (IZ, ˜180 m to ˜80 m), avoiding wasteful resource dilution of the MRZ or PRZ reserves, and allowing methane extraction from the PRZ and IZ. The water treatment process produces valuable algal biomass and co-harvests Mg-hydroxide in vast amounts, allowing value expansion by massive production of bioproducts and CO2-absorbing eco-cements, concretes and related products.
17 Citations
16 Claims
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1. A method for treating water extracted from Lake Kivu, said method comprising the steps of:
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(a) extracting water from an extraction depth of Lake Kivu to obtain extracted water; (b) degassing the extracted water so as to remove at least a portion of carbon dioxide gas from the extracted water and provide degassed water having a density lower than the extracted water and having a pH higher than the extracted water; (c) photosynthetic treatment of the degassed water by growth of an algal biomass to convert bicarbonate anions to carbon dioxide and hydroxyl anions, such that the pH of the degassed water is increased and magnesium and calcium precipitate out of the degassed water to provide de-densified water and precipitate; (d) separating the de-densified water from the algal biomass and the precipitate; (e) optionally adjusting the pH of the de-densified water by adding carbon dioxide thereto, wherein the carbon dioxide is obtained from the degassing step and by combustion of methane also obtained in the degassing step; and (f) reinjecting into Lake Kivu a return flow of the de-densified water separated from the biomass and precipitate, wherein the de-densified water is reinjected into Lake Kivu at a reinjection depth which is shallower than the extraction depth and which is density-matched with the de-densified water. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system for treating water extracted from Lake Kivu, said system comprising:
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(a) a water degassing system configured to extract water from an extraction depth of Lake Kivu to obtain extracted water and degas the extracted water so as to remove at least a portion of carbon dioxide gas therefrom and provide degassed water; (b) a water treatment system configured to;
(i) photosynthetically treat the degassed water in a biomass containing algae to convert bicarbonate anions to carbon dioxide and hydroxyl anions, such that a pH of the degassed water is increased and magnesium and calcium precipitate out of the degassed water to provide de-densified water and precipitate;
(ii) separate the de-densified water from the biomass and the precipitate; and
optionally (iii) adjust the pH of the de-densified water by adding carbon dioxide thereto, wherein the carbon dioxide is obtained from the degassing step and by combustion of methane also obtained in the degassing step; and(c) a return flow system configured to reinject into Lake Kivu a return flow of the de-densified water separated from the biomass and precipitate, wherein the de-densified water is reinjected into Lake Kivu at a reinjection depth which is shallower than the extraction depth and which is density-matched with the de-densified water. - View Dependent Claims (14, 15, 16)
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Specification