Which term describes a substance that is poisonous to living organisms?

The term that describes a substance that is poisonous to living organisms is "toxic." Toxic substances can cause harm or death through various mechanisms, such as disrupting metabolic processes, damaging tissues, or affecting the nervous system. In the context of wastewater treatment, identifying and understanding toxic substances is crucial, as they can significantly affect both human health and the environment. Treating wastewater effectively requires knowledge of toxic components to ensure the safety of discharged effluents and to protect aquatic life.

While the terms hazardous, contaminant, and chemical waste may relate to harmful substances, they encompass broader definitions. Hazardous substances may not always be directly toxic but can pose risks through various means such as flammability or reactivity. Contaminant refers to any unwanted substance that can impair water quality but isn’t necessarily poisonous. Chemical waste generally refers to discarded materials that can be solids, liquids, or gases, which may or may not be toxic. Thus, the specificity of "toxic" makes it the most accurate term for describing a poisonous substance.