Waste water treatment Flashcards – AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Foundation

Rank groundwater, wastewater and salt water from generally easiest to hardest to make potable.

Groundwater → wastewater → salt water.

Why is groundwater usually the easiest source to make potable?

Rocks naturally filter it, so it often needs less treatment to remove dissolved substances and microbes.

Why does wastewater require substantial treatment to become potable?

It contains sewage, organic matter, microorganisms and other contaminants.

Why is salt water generally the hardest source to make potable?

Dissolved salts must be removed by desalination, which is energy-intensive and expensive; other impurities may also need treatment.

What two factors should be compared when assessing how difficult water sources are to make potable?

The starting level of contamination and the amount of treatment needed to make the water safe to drink.

What is the overall purpose of sewage treatment?

To remove solid material and reduce biological pollution, producing outputs less harmful to release.

What is the sequence of sewage treatment stages, including the two paths after sedimentation?

Screening and grit removal → sedimentation → anaerobic digestion of sludge and aerobic treatment of effluent.

What is the role of screening and grit removal in sewage treatment?

To remove large objects and heavy particles that could interfere with later treatment.

What does sedimentation separate sewage into?

Solid sewage sludge and liquid effluent.

How is sewage sludge treated by anaerobic digestion?

Microorganisms break down its organic matter without oxygen.

How is sewage effluent treated aerobically?

Microorganisms use oxygen to break down remaining organic matter.