Proposed system harnesses microbial fuel cell (MFC) and microbial electrolysis cell (MEC) processes for treating wastewater (WW) at individual house and generating electricity and clean water. This system intends to conserve resources at the primary source, hence decreasing energy foot-prints.
A MFC consists of an anode, a cathode, a proton-exchange membrane (PEM) and an electrical-circuit. Bacteria live in the anode and convert WW into CO2, protons and electrons. Under aerobic-conditions, bacteria use O2 as final electron-acceptor to produce water. However, in anode-chamber, O2 will be absent and hence, bacteria has to switch from natural electron-acceptor to an insoluble-acceptor role, so act as the MFC anode (collecting electrons originating from microbial-metabolism). Protons flow through PEM to the cathode, where O2 is chemically-reduced to water.
In MEC, an additional voltage (>0.25 V) is supplied to cell from outside source, which is sufficient to reduce protons-to-hydrogen. As part of energy for this reduction is derived from anaerobic-bacterial activity, total electrical energy that has to be supplied is less than for electrolysis of water in the absence of microbes. Addition of biodegradable-matter (i.e. WW) will enhance microbial-activity in fuel cell and thus increasing voltage generated by it.
As soon as, WW is dispatched to the anode of microbial-fuel cell, bacteria, with the help of water, start reducing the organic-compounds into CO2, protons and electrons. Protons are passed through PEM and electrons are transferred to the cathode through electrical-circuit, allowing current to pass. Protons, electrons and O2 form “clean-water” at cathode, with the help of saltwater present.
For producing this into market, major efforts needs to be placed on the design of membrane that allows protons to pass through chambers, but not the substrate or electron-acceptor in the cathode-chamber (oxygen). Higher power-densities can be achieved using oxygen as electron-acceptor at air-cathodes. Anode and cathode are placed on either side of a tube, with anode sealed against a flat plate and cathode exposed to air on one side, and water on the other. To increase the overall system-voltage, MFCs can be stacked as a series of flat-plates or linked-together in series. In proposed H-configuration, as-long-as two chambers are kept separated, they could be pressed up onto either side of the membrane and clamped together to provide large surface area. With the provision of second-chamber for capturing hydrogen, it is possible to develop proposed system for hydrogen production. Other than MEC and MFC, other components can be installed and maintained by a mechanic.
Water conserving nature of proposed-system will cut-down water bills up to 45%. Only expenditures are maintaining fuel cells (bacteria), PEM, and chambers ($20-30/year). Proposed system reduces resources cost by up to 80%. Installation cost for setup of MFC is ~$700 and ~$420 for MEC, so initial cost is ~$1150. Using this system, current costs (utility cost for individual house) can be brought down to ~$45/month. Initial cost of setting up proposed system will be paid for on account of cost effectiveness. Thus, installation cost will be refunded within a year of initial setup.