| Nitrogen fixation | (Environmental Engineering) The conversion of atmospheric (or dissolved) nitrogen gas into nitrate by microorganisms. |
| Nonpoint source pollution (NPSP) | (Environmental Engineering) Any pollution from a source which cannot be attributed to a particular discharge point, e.g. from agricultural crops, city streets, construction sites, etc. |
| Oxidative phosphorylation | (Environmental Engineering) The synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using a chemical substrate and molecular oxygen. |
| Pathogenic organism | (Environmental Engineering) An organism capable of causing infection. |
| Phosphorylation | (Environmental Engineering) The synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP). |
| Photoautotrophic | (Environmental Engineering) Organisms which utilize inorganic carbon dioxide for protoplasm synthesis and light for an energy source. See autotrophic and chemoautotrophic. |
| Photophosphorylation | (Environmental Engineering) The synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using solar energy. |
| Phototroph | (Environmental Engineering) Organisms which obtain energy from light using photooxidation. |
| Producers | (Environmental Engineering) Autotrophic organisms which produce protoplasm using inorganic carbon and energy from the sun. |
| Reactive waste | (Environmental Engineering) A waste which; 1) reacts violently with water, 2) forms potentially explosive mixtures with water, 3) is normally unstable, 4) contains cyanide or sulfide in sufficient quantity to evolve toxic fumes at high or low pH, 5) is capable of exploding if heated under pressure, or 6) is an explosive compound listed in Department of Transportation (DoT) regulations. One of EPA's four hazardous waste properties. |