U2 T6 Flashcards
(43 cards)
Proportion of global use of water in %
Agriculture : 70%
Industry: 15%
Domestic uses: 15%
What does abstractive uses involve
Abstractive uses involve removing the water from where it was found
What does domestic uses include
Washing, flushing toilets, food preparation, drinking, watering house and garden plants and recreation.
Tell some differences about the use of water in MEDCs and LEDCs (about restriction and water quality)
In MEDCs the water is purified before use and the amount available does not usually restrict its use. In LEDCs shortage often restrict use to essential activities. The technology may not be available to purify it so water- borne diseases are common.
Name some industries that use large amount of water
Many industries, such as power stations, the chemical industry and some mining and mineral processing industries, require large amount of water.
What does major industrial uses of water include ?
Major industrial uses of water include cooling, heating washing, steam generation, transport as a solvent.
For what are used the cooling towers?
Cooling towers are used to cool condenser water before it is returned to a river.
What is the biggest single agricultural use of water?
Irrigation
Why is water necessary in agricultural uses
- crops and livestock need water to survive , if it is not naturally available the it must be provided —> irrigation
There are 3 main reasons for irrigating crops. What are these?
- To replace water lost in evaporation ô prevent plant dying out
- For growth as it is used in photosynthesis to produce sugar and moist air allows stomata to stay open in full light and absorb maximum CO2
- For the transport of mineral ions, it aids nutrient uptake as nutrients can only be absorbed by roots if they are dissolved in water
On what depends the degree to which water needs to be purified?
It depends upon its intended use. What may be very important for one use may not be so important or another use.
What is the most important large-scale water use where quality is very important ? What criteria are used to assess the water quality?
Public water supply is the most important large-scale water use where quality is very important and supplies may require a lot of treatment. Many physical, chemical and biological criteria are used to assess the water quality for public supply
How must be potable water?
Potable water does not have to be completely pure, but it must not contain unacceptable levels of hazardous materials nor look, taste or smell unpleasant.
How is the concentration (of turbidity) expressed?
As TSS (Total Suspended Solids)
What could you say about turbidity in water?
Suspended solids must be removed because they give water an unpleasant appearance and taste and the settling of suspended solids would block pipes.
What can happen if pH concentration is too high or low?
If water is too acidic it can dissolve copper pipes. If the pHis too high it can make the water taste unpleasant. The ideal range is pH 6.4 to 8.5
What does make the water harder ?
Dissolved calcium ions make the water “harder”
What are the “good” and “bad” thing of hard water
Hard water is good for health as it can help to reduce tooth decay, osteoporosis and heart disease.
But it can react with soap to produce scum and produces solid limescale if the water is heated
What could you say about pesticide concentration? (Toxicity)
All pesticides are toxic, but not necessarily very toxic to humans. Water should be treated to remove virtually all pesticides.
What does heavy metal concentration in water causes?
Heavy metals, such as lead and mercury are neurotoxins and damage the nervous system, but low concentrations cause no detectable damage.
What does dissolved O2 causes in water ?
Low dissolved oxygen levels can make water smell musty or of hydrogen sulfide (=”bad eggs” smell). Some toxic metals are more soluble in water with a low dissolved oxygen content.
Why is chlorine added to water?
Chlorine is added to water to keep it sterile.
What may react with chlorine and reduce its concentration?
Their materials present in the water and the pipe’s wall itself may react with chlorine and reduce its concentration. It may be necessary to add more chlorine or use chloramines, which gradually releases more chlorine,
What could cause sewage contamination of water ?
Sewage contamination of water could cause the spread of many serious diseases caused by pathogens such as cholera and typhoid, but the bacteria that cause these are uncommon, so testing for them would not prove there was no sewage present.
