]> In wastewater treatment, a combination of step processes, usually physical in nature, that are designed to remove floating and settleable solids. Examples of process steps are screening and sedimentation. In wastewater treatment, a combination of step processes, usually biochemical in nature, that are designed to remove primarily organic material. Examples of process steps are aeration and trickling filters. Post-secondary treatment of wastewater designed to improve the quality of the water to the point where it can be put to a particular beneficial use. Generally, tertiary treatment steps remove nutrients (e.g., nitrogen and phosphorus) which are poorly removed by secondary treatment. Commonly used steps include coagulation and clarification.