What are the key indicators of wastewater toxicity?

The key indicators of wastewater toxicity include measurements like BOD (Biochemical Oxygen Demand) and the presence of heavy metals. BOD is an important indicator because it reflects the amount of organic matter in the water, which can deplete oxygen levels, harming aquatic life. High levels of BOD suggest that the wastewater may be detrimental to the environment as it can lead to hypoxic conditions, impacting fish and other organisms.

Additionally, the presence of heavy metals indicates potential toxicity, as these compounds can be harmful even in trace amounts. Heavy metals such as lead, mercury, and cadmium can accumulate in organisms and ecosystems, posing significant health risks.

While pH is a critical parameter for understanding the general condition of wastewater, it is not solely indicative of toxicity. Total Suspended Solids (TSS) and nutrient levels might also provide important information regarding wastewater quality, but they do not directly measure toxicity as effectively as BOD and heavy metals do. Thus, the combination of BOD and the presence of heavy metals makes this option the best choice for assessing wastewater toxicity.