What is the primary byproduct of human activity that is treated in wastewater facilities?

The primary byproduct of human activity that is treated in wastewater facilities is sewage. Sewage consists primarily of water mixed with organic matter, human waste, food scraps, and various chemical substances that enter the wastewater system from residential, commercial, and industrial sources. Wastewater treatment facilities are specifically designed to handle this type of waste, ensuring that it is processed to remove harmful substances and pollutants before being released back into the environment or reused.

Surface water, while it may sometimes enter the treatment process, is not a byproduct of human activity in the same sense as sewage. Rainwater is also not treated in wastewater facilities as a primary function; instead, it is typically managed through stormwater management systems. Industrial runoff can be a concern, but it is usually addressed through different regulatory processes and may not constitute the main focus of standard sewage treatment, which targets household and municipal waste.

Overall, sewage is the central material treated at wastewater facilities, as it directly represents the byproducts of daily human activities that need proper management for environmental and public health reasons.