Which description best fits the term 'effluent'?

The term 'effluent' specifically refers to treated water that is discharged from a wastewater treatment facility back into the environment. This water has undergone various treatment processes designed to remove contaminants and pollutants, ensuring it meets environmental standards before being released. The treatment process typically includes physical, biological, and chemical methods to effectively reduce harmful substances, making the effluent safe for discharge into bodies of water, such as rivers or lakes, or for reuse purposes.

In contrast, the other options do not accurately define effluent. For instance, it is not limited to solid waste materials or untreated wastewater. Effluent is specifically water that has been treated, not just any release of water, as some may still be non-compliant with environmental regulations. Understanding effluent is vital for ensuring that treated water does not harm aquatic ecosystems and public health when it's released.