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Water Treatment

Water Treatment. By Loan Quan IB Chemistry SL January 23, 2013. I. Primary Pollutants. Found in: Heavy metals Pesticides Dioxins Polychlorinated (PCBs) Organic matter Nitrates & Phosphate. A. Heavy Metals. It’s poisonous a. Examples: mercury, lead, cadmium

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Water Treatment

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  1. Water Treatment By Loan Quan IB Chemistry SL January 23, 2013

  2. I. Primary Pollutants • Found in: Heavy metals Pesticides Dioxins Polychlorinated (PCBs) Organic matter Nitrates & Phosphate

  3. A. Heavy Metals • It’s poisonous a. Examples: mercury, lead, cadmium b. The metal ions interfere with other ions in the body (ie. Ca2+, Mg2+, Zn2+)

  4. A. Heavy Metals (cont.) • Sources and health hazard of heavy metals a. Mercury 1) source – paint, batteries, agriculture 2) health hazard – nerves & brain damages, symptoms: depression, blindness, insanity, 3) environmental hazard – inhibit growth & kill fish production; biological magnification in food chain ***biological magnification – the builds up of toxic level over time within each successive link in the food chain

  5. A. Heavy Metals (cont.) b. Lead 1) source – lead paint, pipes, pottery 2) h.h. – burning pain in mouth; constipation/diarrhea; severe: kidney, heart, liver failure; brain damage in kids 3) envir. h. – toxic to plants & domestic animals; biological magnification in food chain

  6. A. Heavy Metals (cont.) c. Cadmium 1) source – metal plating, rechargeable batteries, zinc refining products 2) h.h. – kidney & lung cancer, makes zinc ineffective in the body 3) envir. h. – toxic to fish, birth defects in mice

  7. B. Pesticides • Include: insecticides, fungicides, herbicides a. Poisonous  cause pollution when washed off land & into water • Example: DDT (dichloro- diphenyl- trichloroethane) a. structure – b. is a biological magnification

  8. C. Dioxins • Each ring can have up to 4 chlorine atoms • Are presented when wastes contain organochlorine compound are burnt a. Also found in weed killer • Stays in fat and liver cells a. symptoms: liver cirrhosis, heart & memory damage, depression, chlorance – skin disease b. malfunction in fetuses

  9. D. Polychlorinated biphenyls (PCBs) • Have high electrical resistance • Used in electrical transformers & capacitors • Stays in the environment & accumulate in fatty tissue • Reduce reproductive efficiency & impair learning

  10. e. Nitrates • Sources: intense farming/ artificial fertilizers, acid rain • It is soluble  not easily removed during sewage treatment • Set limit of nitrate in drinking water: 50 mg dm-3 a. High level can interact with hemoglobin & affect oxygen transport b. Risk in babies: 1) nitrate converts to nitrite 2) nitrite oxidized Fe2+ to Fe3+ 3) decreases oxygen- carrying capacity  form methaemoglobin (blue baby syndrome) c. Risk in adults: 1) can cause cancer a) nitrate  nitrite  nitrosamine b) nitrosamine = carcinogenic

  11. II. Waste- Water Treatment • Purpose: to remove hazardous materials, reduce BOD, kill microorganisms • There are 3 treatments

  12. A. Primary Treatment • Method: filtration/ screening a. waste water passes into sediment tank  sludge at the bottom is removed 1) flocculation – allows particles to clump together by adding chemical to speed up sedimentation process a) adds: aluminum sulfate & calcium hydroxide  precipitate of aluminum hydroxide Al2(SO4)3 + 3Ca(OH)2 2Al(OH)3 + 3 CaSO4 • Removes: larger insoluble objects a. removes 30-40% of BOD waste

  13. B. Secondary Treatment • Method: aeration/ activated sludge process a. passes through an aeration tank, which is enriched with oxygen b. the sludge settles in sedimentation tank, aerobic bacteria is added to break down organic matter = activated sludge process • Removes: 90% of organic matter • Substances used: oxygen & bacteria

  14. C. Tertiary Treatment • It is expensive, but necessary • Can remove heavy metal ions, nitrates, phosphates, or organic compounds which primary and secondary treatments cannot • chemical precipitation a. removes: heavy metal ions & phosphate 1) phosphate ions decrease by adding calcium or aluminum ion 3Ca2+ +2PO43- Ca3(PO4)2 Al3+ + PO43-  AlPO4 2) heavy metals precipitate as sulfide salt Cd2+ +H2S CdS +2H+

  15. C. Tertiary Treatment (cont.) • Reverse osmosis a. Osmosis: movement of solvent (water) from dilute to concentrated solution b. Semi/partially permeable membrane: allows solvent to pass through, but solute particles cannot c. Methods: 1) sea water is pressurized with at least 70atm (osmotic pressure) 2) pure water passes through the semi- permeable membrane 3) solute (salt) is left behind d. Advantage – significantly reduces salt, most other inorganic material present in the water, and some organic compounds e. Disadvantage - damaged membranes are not easily detected  not be able to know if the system functions normally or not

  16. C. Tertiary Treatment (cont.) • Distillation a. Methods: 1) sea water is heated & passed into evacuated chamber in order to be boiled 2) anything don’t evaporate stays at the bottom to be removed 3) steam is condensed by pipes b. Advantage – removes pathogens c. Disadvantage – expensive to maintain; take 2-5 hours to make 1 gallon of water

  17. C. Tertiary Treatment (cont.) • Ion exchange a. Resins/ zeolites are used to exchange nitrate ions with hydroxide ions 1) X-OH- + NO3-(aq) X-NO3- + OH-(aq) 2) Y-H++ M+(aq) Y-M++ H+(aq) 3) H+ and OH- combine to form H2O b. Removes salt from sea water c. Very expensive

  18. III. Chlorine & Ozone treatment

  19. THE END

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