Water Treatment
Chemistry makes water safe to drink.
About this topic
Water treatment makes raw water safe to drink. Typical steps are screening to remove debris, coagulation and flocculation (adding aluminium sulfate to make particles clump), sedimentation, filtration through sand and gravel, and disinfection with chlorine, ozone or ultraviolet light. Wastewater treatment adds biological stages where bacteria break down organic matter.
Coagulants such as alum, Al2(SO4)3, form sticky aluminium hydroxide that traps fine particles, which settle out as sludge. Filtration removes the remaining suspended material, and activated carbon can adsorb tastes, odours and organic pollutants. Chlorine kills bacteria and viruses and leaves a residual in the pipes to protect the supply: Cl2 + H2O gives HCl + HOCl. pH is adjusted to prevent pipe corrosion, and fluoride may be added to protect teeth. In desalination, reverse osmosis forces seawater through a membrane under pressure greater than osmotic pressure, or distillation boils it.
Chlorination of drinking water saved millions of lives from cholera and typhoid. At home, boiling, filters or purification tablets make questionable water safe. Hard water contains calcium and magnesium ions, which can be removed by ion exchange resins.
A misconception is that clear water is safe: dissolved chemicals and microbes are invisible. Another is that distilled water is the best to drink, though it lacks minerals; it is used in labs and irons.
Key ideas
- Filtration, coagulation, chlorination
- Hard water has Ca²⁺ and Mg²⁺
- Desalination uses membranes
Quick check
Use cases: where Water Treatment helps
- Homework: review the key idea behind Water Treatment before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Water Treatment without notes.
- Visual learning: play with the interactive lab to see how Water Treatment changes when you adjust its inputs.
- Teaching a friend: explain Water Treatment in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Water Treatment?
Chemistry makes water safe to drink.
What will I learn in Water Treatment?
Filtration, coagulation, chlorination. Hard water has Ca²⁺ and Mg²⁺. Desalination uses membranes.
Is Water Treatment part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Water Treatment lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Water Treatment?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.