Potable Water and Water Treatment
How can sea water be treated to make potable water?
Distillation - to desalinate sea water Membranes - reverse osmosis salty water passed through membranes only allows water molecules through
What is distillation?
Distillation is when the solution is boiled and the vapour is cooled and collected
What are the steps to distilling water in the lab?
Pour salty water in distillation apparatus and heat flask from below Water boils forming steam leaving dissolved salts in flask Steam condenses back to liquid water to be collected Then retest pH and for sodium ions for successful removal
What is reverse osmosis?
Pressure applied to salt water and water gets pushed through a semi-permeable membrane leaving contaminate behind
Why isn't potable water pure water?
Pure water only contains H2O molecules but potable water can contain other dissolved substances
Where do very dry countries where there is neither surface water nor groundwater get their water from?
Sea water
Where are you most likely to get your water supply from if you live in a warm area?
Since surface water dries up first it comes from groundwater
What is flocculation?
a slow stirring process that causes the gathering together of small, coagulated particles into larger, settleable floc particles.
What is turbidity?
cloudiness of water
Why is fluoride added to water?
reduce tooth decay
Why is chlorine added to water?
to kill bacteria
How are fresh water sources treated?
Filtration - wire mesh for large objects, and gravel and sand beds for any other solid bits Sterilisation - kills any harmful bacteria or microbes with ozone or ultraviolet light or bubbling chlorine gas through it
What do the downside to using distillation and reverse osmosis to clean sea water?
Needs lots of energy Really expensive Not practical for producing large quantities of fresh water
What are the two ways rain water can collect as?
Surface water - lakes, reservoirs and rivers Groundwater - rocks called aquifers trap water underground
What are the steps to test water in the lab?
Test pH of water using pH meter if it's too high or low add acid or alkali to neutralise it Test water for presence of sodium chloride - sodium ions do flame test if present flame turns yellow - chloride ions take another sample of water add few drops of dilute nitric acid and silver nitrate solution if present white precipitate forms
What is coagulation?
The process of particles sticking together in clumps.
What is potable water?
Water treated or naturally safe for human consumption