Water Flashcards
Temporary hardness
Water hardness that can be removed by boiling
Hard water
Water that does not lather easily with soap due to Ca / Mg ions
Permanent hardness
Water hardness that cannot be removed by boiling, removed by
- distillation
- adding washing soda
- ion exchange resin
Ion exchange resin
Swapping ions caysing hardness eg Ca with ones that don’t eg Na (called cation exchange resin)
Deionised water
All ions removed from water
H+ and OH- ions in resin water contains Na+ and Cl-
Steps in water treatment
Screening Flocculation Settling Filtration Chlorination Fluoridation Ph adjustment
Screening
Water passes through wire mesh to remive floating debris
Flocculation
A flocculation agent eg ALUMINIUM SULPHATE is added in order for small dirt particles form larger particles
Settlement / sedimentation
Water is passed in the bottomn of settlement tanks as water levels slowly rise , clear water is taken from the top of the tank
Filteration
Water passes through beds of sand to remove all remaining solids , sand beds are cleaned regularly
Chlorination
Chlorine added to get rid of disease and sterilise if too much added water might taste bad
Fluoridation
Addition of fluorine containing substance eg NaF , helps prevent teeth decay and increases enamel of teeth
BOD
Biochemical oxygen demand
Amount of dissolved 02 used up by biological action
When a sample of h20 is left in the DARK for 5 DAYS at 20*C
Ph adjustment
Too acidic add CALCIUM HYDROXIDE
Too alkaline due to SODIUM CARBONATE used to soften h2o add DILUTE H2SO4
Disadvantages of h2o too acidic
Could CORRODE PIPING
solve by addition of CALCIUM HYDROXIDE
Eutrophication
This is the ENRICHMENT of water in nutrients such as phosphates and nitrates leading to the EXCESSIVE growth of ALGAE
Examples of h20 pollution
Eutrophication (natural/artificial)
Release of TOXIC METAL IONS into water
Toxic metals for h20
Lead (old houses with lead plumbing)
Mercury
How are heavy metals removed from h20
PRECIPITATION with HCL
Primary treatment of sewage
MECHANICAL PROCESS INVOLVING SCREENING AND SETTLEMENT
Steel bars- solids
Grit channels
Tanks , form sludge, settlement / SEDIMENTATION
liquid on top goes to SECONDARY treatment
Secondary treatment if sewage
BIOLOGICAL PROCESS , this is the BACTERIAL BREAKDOWN of sewage
Using ACTIVATED SLUDGE PROCESSES consisting of an AERATION tank followed by SETTLEMENT
Aeration- nutrients in sewage used for growing microorganisms air can be bubbled into tank if dissolved 02 in liquid is low
Sludge sealed in tanks , methane or recycled into aeration tank
Most of BOD removed still contains phosphates and nitrates , tertiary treatment
Tertiary treatment of sewage
Removal of phosphates and nitrates (phosphorourous and nitrogen compounds)
Phosphorous -hoysehold detergents
N- organic materials in sewage
Phosphates removed by PRECIPITATION
Nitrogen removed by BIOLOGICAL DENITRIFICATION
EXPERIMENTS!!!
No!!! go and learn them NOW
