Wastewater Treatment Using Microbial Fuel Cells with Peroxide Production
ER-2239
Objective
U.S. forward operating bases (FOBs) often are burdened by water transport and wastewater treatment and disposal. In order to avoid the costs and risks associated with water transport, the military must develop reliable wastewater treatment that focuses on water reuse and is energy neutral or positive. Properly implemented, microbial anaerobic technologies can achieve both goals when treating high strength wastewaters, such as blackwater. Among the options for anaerobic treatment, the microbial fuel cell (MFC) is the most innovative and promising technology today. MFCs catalyze the conversion of waste chemical oxygen demand (COD) directly into electrical power, which results in a higher efficiency of energy collection than indirect methods through methane or hydrogen gas. In addition, the electrical current generated in a MFC can be used to produce hydrogen peroxide (H2O2) at the cathode. This valuable chemical can serve as a disinfectant, be used for the treatment of graywater, or applied to accelerate or enhance the oxidation of organics in blackwater.
The researchers will conduct applications-driven research so that blackwater can be treated using a MFC with concomitant H2O2 production. Power generation by the MFC will be an important secondary benefit. The researchers will develop a MFC that focuses on hydrolyzing and stabilizing the solids contained in blackwater, while providing enough H2O2 to treat the residual COD in the effluent stream, as well as the graywater stream. The high production of H2O2 is achieved by oxidizing the biological oxygen demand (BOD) present in the blackwater solids inside the MFC.
Technical Approach
There are five aims of this project to achieve the project objective. First, the researchers will study the kinetics of microbial hydrolysis of organic solids and of anode respiration in blackwater. The solids hydrolysis of blackwater will most likely be the rate-limiting step during blackwater treatment and power/ H2O2 generation. The studies will fully characterize blackwater hydrolysis rates in the MFC setting. Second, the researchers will test various materials that are suitable for a MFC producing H2O2 from blackwater. This will allow the researchers to select the best anode, cathode, and membrane materials. The researchers will focus on inexpensive carbon-based materials for the anode and the cathode. Third, the researchers will design a process-automation system that will enable the operation of MFCs for field application. System automation has not been researched for MFCs and is an important step towards practical implementation. Development of a MFC-automation system will allow FOBs to maintain the excellent performance of the treatment facility without highly skilled labor. Fourth, the researchers will design, build, and test laboratory-scale prototypes that focus on H2O2 production. To achieve this aim, the researchers will assemble the knowledge obtained from the first three aims in order to build suitable MFC prototypes. The MFC prototypes will be tested and optimized under laboratory-scale conditions using primary wastewater sludge as surrogate for blackwater. The researchers will test the MFC automation with the prototypes, which will aid in MFC optimization. Finally, the fifth aim is to synthesize the knowledge into a preliminary design of a field-demonstration unit to be demonstrated under ESTCP. This will allow a rapid transition of the technology into the field and towards its final implementation.
Benefits
Preliminary calculations show that the MFC will be able to generate at least two times the H2O2 required to completely oxidize the BOD present in the graywater and the MFC effluent. Additionally, the MFC is modestly energy positive, with an electrical energy generation rate of 0.01 kWh/gal. While the net output of power is modest, it surpasses the process objective of energy neutrality, and the H2O2 production has a net energy value of 1.9 kWh/gal. Thus, the approach will benefit the military by making blackwater treatment energy positive and aiding in water reuse through the production of H2O2. More broadly, the technical community will benefit from a better understanding of hydrolysis kinetics in MFCs and the development of control algorithms that can be used to optimize MFCs in the laboratory or in the field.
Points of Contact
Principal Investigator
Dr. César Torres
Arizona State University
Phone: 480-727-9689
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.