Craig Criddle is interested in the environmental engineering, science, and science literacy needed for clean water, clean energy, and healthy ecosystems. His research focus is environmental biotechnology.  He is best known for large interdisciplinary field projects, studies of microbial ecology in bioreactors, and work on microbial transformations of persistent contaminants. Some current projects include a field-scale evaluation of uranium remediation; DNA-monitoring of microbial community structure at full-scale biological wastewater treatment plants; development of membrane bioreactors for energy recovery and nutrient removal; and studies to elucidate the mechanisms and kinetics of microbial transformation of halogenated solvents.