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From raw water to the drinking-water tap

Clear river water is not automatically safe to drink. Many surface-water treatment plants use a sequence of coagulation, settling, filtration, and disinfection, with each stage tackling different hazards. The exact treatment depends on the source water and the contaminants the utility needs to remove.

4–5 min

Questions you could explore

  • What can a filter remove that disinfection does not?
  • Why does the sequence depend on the water source?

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Cities and transport

How can three words identify a three-meter square?

A street address can identify a house but struggle with a park entrance or a remote rescue location. The what3words system assigns three-word addresses to a worldwide grid of three-meter squares; open alternatives such as Plus Codes encode locations with letters and numbers. Comparing the systems raises practical questions about reading a location aloud, confusing similar codes, and depending on a proprietary service.

3–5 min

How can three words identify a three-meter square?

Cities and transport3–5 minA street address can identify a house but struggle with a park entrance or a remote rescue location. The what3words system assigns three-word addresses to a worldwide grid of three-meter squares; open alternatives such as Plus Codes encode locations with letters and numbers. Comparing the systems raises practical questions about reading a location aloud, confusing similar codes, and depending on a proprietary service.

Cities and transport

How does a canal lock lift a boat without lifting machinery?

A boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

3–5 min

How does a canal lock lift a boat without lifting machinery?

Cities and transport3–5 minA boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

Cities and transport

Why can irregular buses make you wait longer?

Two services can have the same average gap between buses yet create different average waits. If passengers arrive steadily without consulting a timetable, more of them arrive during long gaps than short ones. Uneven service therefore gives the longest gaps extra weight in the passenger experience.

8–10 min

Why can irregular buses make you wait longer?

Cities and transport8–10 minTwo services can have the same average gap between buses yet create different average waits. If passengers arrive steadily without consulting a timetable, more of them arrive during long gaps than short ones. Uneven service therefore gives the longest gaps extra weight in the passenger experience.

From raw water to the drinking-water tap | Speech Topic | speaking.app