--- title: "Potable Water and Treating Waste Water" description: "Potable water is safe to drink but can contain dissolved substances. Treatment depends on the source, its contaminants and cost. Wastewater treatment separates solids and uses microbes to break down o" canonical: https://lightmysky.com/learn/science/potable-water-and-treating-waste-water-mt_5qsFZJSmMO source: https://lightmysky.com/learn/science/potable-water-and-treating-waste-water-mt_5qsFZJSmMO.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Potable Water and Treating Waste Water Potable water is safe to drink but can contain dissolved substances. Treatment depends on the source, its contaminants and cost. Wastewater treatment separates solids and uses microbes to break down organic waste in the liquid and sludge. Subject: Science · Area: Matter & Materials · Ages 15 to 16 Page: https://lightmysky.com/learn/science/potable-water-and-treating-waste-water-mt_5qsFZJSmMO ## Ready when they can - Describe the steps that turn fresh water into potable water and say what each step removes - Explain how the energy needed for desalination affects its use where fresh water supplies are limited - Distinguish the aerobic and anaerobic stages of sewage treatment by what each one is for ## Lesson: Turning river water into drinking water A common treatment sequence for river water is screening, settling, sand filtration and disinfection. Screens remove large debris. Settling lets suspended solids such as silt sink. Sand filters remove more particles. Chlorine can inactivate many bacteria and viruses. Some microbes resist chlorine, so treatment and testing must match the source. *(drawing: Particle removal comes before disinfection in this example. Other sources can need different or additional treatment.)* Potable means safe to drink: harmful microbes and chemicals must be controlled to safe levels. It does not mean sterile or chemically pure. Potable water can contain dissolved minerals. Chemically pure water contains only water. A clear appearance cannot show whether water is safe. Desalination removes dissolved salts. Distillation evaporates water and collects it after condensation, leaving salts behind. Reverse osmosis pumps water through a membrane under pressure; most salts stay behind. Heating or pumping needs energy. Desalination usually uses more energy than treating fresh water, so cost and available supplies affect the choice. Removing salt alone does not establish drinking-water safety. Screening removes large debris as a separate waste stream. Settling then separates suspended solids, including silt, as sludge. Dissolved organic waste remains in the liquid. In an aerobic tank, air supplies oxygen to microbes that break down this waste. Further settling separates microbial solids from the treated liquid. The liquid must meet discharge requirements before release; it is not automatically drinking water. *(drawing: Screened debris is removed separately. Settled sludge goes to its own treatment. The boxes show the liquid-treatment route.)* Separated sludge can be treated in an anaerobic digester. Unlike the aerobic liquid-treatment tank, this vessel works without oxygen. Microbes break down organic material and produce biogas containing methane, which can be collected as fuel. Treated sludge may be used on land only if it meets the required safety limits. Other sludge needs further treatment or disposal. **Recap.** Potable means safe to drink. Remove particles and disinfect as needed. Desalination removes salts. Aerobic treatment uses oxygen; anaerobic sludge digestion can produce biogas. *Lesson, questions and flashcards written for this dataset.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Choosing How to Separate Mixtures](https://lightmysky.com/learn/science/choosing-how-to-separate-mixtures-mt_U_tJvy3cbB) ## Optional connections - [Testing for Ions and Gases](https://lightmysky.com/learn/science/testing-for-ions-and-gases-mt_PDZjzQJdVt)