Environmental Science: Water Resources & Pollution

What percentage of Earth's total water is freshwater, and where is the majority of that freshwater stored?

Approximately 3% of Earth's water is freshwater, with about 68-69% of that total stored in glaciers and ice caps.

Distinguish between point source and nonpoint source water pollution.

Point source pollution originates from a single, identifiable location (e.g., a factory pipe), whereas nonpoint source pollution comes from diffuse, multiple sources (e.g., agricultural runoff or urban storm-water).

Define an 'aquifer' and its primary function in the hydrologic cycle.

An aquifer is an underground layer of water-bearing permeable rock, gravel, or sand that stores and transmits groundwater.

What is the primary objective of the 'primary treatment' phase in a municipal wastewater treatment plant?

The physical removal of large solids, grit, and suspended organic matter through screening and sedimentation (settling).

Which reservoir contains the largest percentage of Earth's liquid (non-frozen) freshwater?

Groundwater contains the vast majority of Earth's liquid freshwater, far exceeding the volume found in lakes and rivers.

What is the 'water table' in the context of groundwater hydrology?

The water table is the upper boundary of the zone of saturation, where all pore spaces in the soil or rock are filled with water.

Explain the process of cultural eutrophication and its impact on Dissolved Oxygen (DO).

Excess nutrients (N and P) cause algal blooms; when the algae die, aerobic bacteria decompose them, consuming dissolved oxygen and leading to hypoxia or 'dead zones'.

What does Biochemical Oxygen Demand (BOD) measure, and how does it indicate water quality?

BOD measures the amount of dissolved oxygen needed by aerobic microorganisms to break down organic matter; a high BOD indicates high levels of organic pollution.

Describe the role of 'activated sludge' in the secondary treatment phase of wastewater processing.

It is a biological process where air and a mixture of microorganisms are added to wastewater to rapidly decompose organic matter through aerobic digestion.

Why is the Ogallala Aquifer in the United States considered a non-renewable resource in many regions?

The rate of water extraction for industrial agriculture far exceeds the natural recharge rate from precipitation, leading to significant water table drawdown.