Method and apparatus for converting chemical energy stored in wastewater into electrical energy
A method and apparatus is provided for harvesting electricity from a biofilm retained in a zero chamber, no interphase container, the biofilm having a portion supporting aerobic microbial activity and a second portion supporting anaerobic microbial activity, wherein the first and the second portion are in direct physical contact. A power harvester is electrically connected, directly or indirectly, to the second portion of the biofilm.
1. A method comprising:
(a) forming a biofilm on a substrate exposed to a volume of wastewater having dissolved oxygen, the biofilm having a sufficient thickness to define a gradient between aerobic microorganisms exposed to the wastewater and anaerobic microorganisms proximal to the substrate;
(b) electrically connecting the biofilm to a power harvester, the power harvester being free of an electrical connection to a separate cathode; and
(c) electrically connecting the power harvester to a ground lead.
2. The method of claim 1 , further comprising electrically connecting the substrate to the power harvester.
3. The method of claim 1 , wherein the ground lead is further electrically connected to at least one of the wastewater and a container retaining the volume of wastewater.
4. The method of claim 1 , wherein electrically connecting the biofilm to a power harvester includes electrically connecting the substrate to the power harvester.
5. The method of claim 1 , wherein the volume of wastewater is independent of a PEM membrane.
6. The method of claim 1 , wherein the volume of wastewater is independent of a catalyst.
7. The method of claim 1 , wherein the volume of wastewater is retained in a container, and the container is independent of an interphase for oxygen diffusion.
8. The method of claim 1 , wherein the wastewater is organic.
9. The method of claim 1 , wherein electrically connecting the biofilm includes electrically connecting a portion of the anaerobic microorganisms to the power harvester.
10. A microbial fuel cell comprising:
(a) a container for retaining a volume of wastewater, the wastewater including dissolved oxygen;
(b) a substrate at least partially submerged in the wastewater, the substrate supporting a biofilm exposed to the volume of organic wastewater, the biofilm having a sufficient thickness to define an electron concentration gradient between microorganisms exposed to the wastewater and microorganisms proximal to the substrate;
(c) a power harvester; and
(d) a first electrical conductor between the power harvester and one of (i) the biofilm and (ii) the substrate, wherein the power harvester is free of an electrical connection to a separate cathode.
11. The microbial fuel cell of claim 10 , further comprising a second electrical conductor between the power harvester and a ground.
12. The microbial fuel cell of claim 10 , wherein the substrate is conducting.
13. The microbial fuel cell of claim 10 , wherein the substrate is non-conducting.
14. The microbial fuel cell of claim 11 , wherein the ground is the wastewater.
15. The microbial fuel cell of claim 11 , wherein the ground is the container.
16. The microbial fuel cell of claim 10 , wherein the container is independent of a proton exchange membrane.
17. The microbial fuel cell of claim 10 , wherein the container is independent of a catalyst.
18. The microbial fuel cell of claim 10 , wherein the container is independent of an interphase for oxygen diffusion.
19. The microbial fuel cell of claim 10 , wherein the container is independent of a membrane compartment.
20. A microbial fuel cell comprising:
(a) a container retaining a volume of wastewater, the container being free of a proton exchange membrane and the wastewater including dissolved oxygen;
(b) a substrate at least partially submerged in the wastewater, the substrate supporting a biofilm exposed to the volume of organic wastewater, the biofilm having a sufficient thickness to define an oxygen concentration gradient between microorganisms exposed to the wastewater and microorganisms proximal to the substrate wherein the gradient is sufficient to generate sufficient free electrons;
(c) a power harvester;
(d) a first electrical conductor between the power harvester and one of (a) the biofilm and (b) the substrate; and
(e) a second electrical conductor between the power harvester and a ground, wherein the power harvester is free of an electrical connection to a separate cathode.
21. The microbial fuel cell of claim 20 , wherein the substrate is conducting.
22. The microbial fuel cell of claim 20 , wherein the substrate is non-conducting.
23. The microbial fuel cell of claim 20 , wherein the ground is the wastewater.
24. The microbial fuel cell of claim 20 , wherein the ground is the chamber.
25. The microbial fuel cell of claim 20 , wherein the ground is a common electrical ground.
26. The microbial fuel cell of claim 20 , wherein the container is independent of a proton exchange membrane.
27. The microbial fuel cell of claim 20 , wherein the container is independent of a catalyst.
28. The microbial fuel cell of claim 20 , wherein the container is independent of an interphase for oxygen diffusion.
29. The microbial fuel cell of claim 20 , wherein the container is independent of a membrane compartment.