Bruce Ritmann studies microbial communities in humans, water, and biofuels. Rittmann's lab is exploring how to manage these microbial communities, and exploit them to an advantage. His work also spans into renewable energy. He is developing technology that uses naturally occurring microorganisms to remove contaminants in water. Professor Rittmann is also using photosynthetic bacteria to develop biofuels.

Rittmann is the director of the Biodesign Swette Center for Environmental Biotechnology, and a faculty member of the School of Sustainable Engineering and the Built Environment. 

He is a member of the National Academy of Engineering and a fellow of AAAS, WEF, IWA, AEESP, ASCE, and NAI. He is reported by the Institute of Scientific Information to be one of the world's most cited researchers. He has also collaborated with Mayo Clinic.