Intermediate Topic 719 of 1102 Inorganic Chemistry
Water Treatment
Coagulation, filtration and chlorination make water safe to drink.
In-depth explanation of Water Treatment
Water treatment makes raw water safe to drink by removing suspended solids, microorganisms and dissolved contaminants. Coagulation adds alum or iron(III) salts to neutralize the charges on fine particles, so they gather into larger flocs. The flocs settle in sedimentation tanks and are removed by sand filtration. Disinfection with chlorine, ozone or ultraviolet light kills pathogens, and chlorine leaves a residual that prevents regrowth in the pipes. Advanced treatment can include activated carbon and reverse osmosis.
Going deeper: Water Treatment
Key ideas: Steps: screening, coagulation with alum or FeCl3 (forming floc by Al(OH)3), sedimentation, sand filtration, disinfection with Cl2 (0.2 to 0.5 mg per L residual), ozone or UV. Softening by lime-soda (Ca(OH)2 and Na2CO3) precipitates CaCO3 and Mg(OH)2, or by ion exchange resins that swap Ca2+ for Na+. Reverse osmosis forces water through a membrane above the osmotic pressure. Hardness is expressed as mg CaCO3 per L, with above 180 considered very hard. Dissolved oxygen needed by life is about 5 mg per L; BOD measures organic load.
Common mistakes and connections: Students believe chlorination removes dissolved metals or hardness; it only kills microbes. Boiling does not remove permanent hardness. Excess chlorine can create chlorinated organics like trihalomethanes. Links to alums, hardness of water, osmosis, redox disinfection and equilibrium of carbonate.
Visualization of Water Treatment
Illustrative removal of suspended particles across treatment stages: alum coagulation and settling remove most of the turbidity before disinfection. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Adding alum to river water forms an aluminium hydroxide floc that carries suspended clay to the bottom of the tank.
Frequently asked questions about Water Treatment
What is Water Treatment?
Coagulation, filtration and chlorination make water safe to drink.
Is Water Treatment a beginner, intermediate or advanced topic?
Water Treatment is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Water Treatment?
Study these earlier topics in Inorganic Chemistry first: Nanomaterials, Quantum Dots, Photovoltaic Materials.
What comes after Water Treatment?
The next topics in Inorganic Chemistry are Inorganic Nomenclature and Polyatomic Ions.
Can I practise Water Treatment with quizzes?
Yes. The interactive lesson includes a self-check question on Water Treatment, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Water Treatment fits in Inorganic Chemistry
Water Treatment is topic 104 of 113 in Inorganic Chemistry.