Under which of the following circumstances is a sewage treatment plant legally permitted to bypass normal treatment protocol and discharge large amounts of sewage directly into a lake or river? (a) When the receiving surface water is designated for swimming only, (b) When the population of the surrounding community surpasses the plant's capacity, (c) When combined volumes of storm water and wastewater exceed the capacity of an older plant, (d) When a permit to modernize the plant is denied by the Environmental Protection Agency, (e) When an extended period of drought restricts water flow in a lake or river.

The right option is option C "when combined volumes of storm water and wastewater exceed the capacity of an older plant"

Explanation:

In a situation where by the combine volume of the storm water and waste water exceeds the capacity of the plant, the sewage treatment plant is given the right to legally discharge the sewage directly to the lake or river which is againts the normal treatment protocol under normal circumstance.

This is so in other to prevent the sewage treatment plant from damage in case of over flow of water into the treatment plant. When the water is exceeds the capacity of the plant, they can discharge the water directly to avoid any harm to the plant.