Water Flashcards
What do you call water that is safe to drink ?
Potable water
Criteria for potable water and why does it have to like this
Low levels of dissolved microbes and low levels of dissolved salts. Dissolved salts can be harmful and microbes can cause illness
What is easier to get fresh or sea water and why
Fresh water as removing sodium chloride from sea water takes lots of energy
Where can you collect rainwater
In rivers lakes and rocks underground
How do you make potable water from fresh water
Pass water through filter beds to remove insoluble particles then sterilise it to remove microbes
Methods of sterilisation
Chlorine ozone and ultraviolet light
What is the process that transforms seawater into potable water called?
Desalination
How can desalination be done ?
By distillation or reverse osmosis
Describe the process of distillation
Seawater is heated until boiled. salt remains in the liquid and the steam is collected in a container. the steam is cooled and condensed down to make potable water. Remains are called brine (the concentrated salt water)
Effects of distillation
Lots of energy is needed to boil the water and cool the steam down to condense it. The waste water is very salty and difficult to dispose in the sustainable way without harming marine ecosystem.
Describe the process of reverse osmosis
Water put through a membrane with pores in it. The pores allow water molecules through, but not most ions and molecules.
Effects of reverse osmosis
It requires expensive membranes and produces large volume of waste water therefore the efficiency is low
Waste water cannot be released into the environment without being treated. It contains some pollutants which are.
Harmful bacteria and high levels of nitrogen compounds which can harm aquatic ecosystems. Industrial waste water may contain harmful chemicals such as toxic metal compounds. Agricultural waste water may contain fertilisers or pesticides which can disrupt sensitive ecosystems.
Describe the process of sewage treatment
Screening and grit removal to remove large particles. Sedimentation allows tiny particles to settle out from Stillwater which produces sewage sludge and effluent (the liquid which remains on top). The sewage sludge is digested anaerobically by specific bacteria and affluent is treated with aerobic bacteria to reduce the volume of solid waste.
