| Autotrophs | (Environmental Engineering) A group of organisms capable of obtaining carbon for synthesis from inorganic carbon sources such as carbon dioxide and its dissolved species (the carbonates). This group includes plants and algae. |
| Bacteria | (Environmental Engineering) One celled microorganisms which do not have a nuclear membrane. |
| Baghouse filter | (Environmental Engineering) A fabric filter device used to remove particulate air pollutants. |
| Biochemical oxygen demand (BOD) | (Environmental Engineering) The amount of oxygen required to oxidize any organic matter present in a water during a specified period of time, usually 5 days. It is an indirect measure of the amount of organic matter present in a water. |
| Biofilm | (Environmental Engineering) A film of microorganisms attached to a surface, such as that on a trickling filter, rotating biological contactor, or rocks in natural streams. |
| Biogeochemical cycle | (Environmental Engineering) The cycle of elements through the biotic and abiotic environment. |
| Biosynthesis | (Environmental Engineering) Catabolism, the production of new cellular materials from other organic or inorganic chemicals. |
| Carbonaceous biochemical oxygen demand (CBOD) | (Environmental Engineering) The amount of oxygen required to oxidize any carbon containing matter present in a water. |
| Carbonyl | (Environmental Engineering) A functional group with an oxygen atom double bonded to a carbon atom. |
| Catabolism | (Environmental Engineering) The production of energy by the degradation of organic compounds. |