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Water Treatment

Water Treatment. Drinking Water Quality. Much of the world's drinking water is contaminated and poses serious health threats U.S. Safe Drinking Water Act of 1974 requires EPA to establish national drinking water standards Alternates to Tap Water:

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Water Treatment

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  1. Water Treatment

  2. Drinking Water Quality • Much of the world's drinking water is contaminated and poses serious health threats • U.S. Safe Drinking Water Act of 1974 requires EPA to establish national drinking water standards • Alternates to Tap Water: • Bottled water- is it really from natural spring? Also, puts too many plastic bottles in landfill! • Home filters- point of entry/use

  3. Water Quality Standards • The EPA (Environmental Protection Agency) sets Maximum Contaminant Levels (MCLs) for drinking water • There are standards for numerous contaminants, two of which cause an immediate health threat if exceeded • Coliform bacteria -because they may indicate presence of disease-causing organisms • Nitrate - can cause ‘blue baby syndrome”—nitrate reacts with blood and blood can’t carry as much oxygen

  4. WATER POLLUTION CONTROLS

  5. Point Reduction • A single identifiable location produces pollution, i.e. a discharge pipe, drainage channel, well, etc. • Eliminate lead from gas- decreased lead in water • Better handling of oil (double hulled ships) • Banning of DDT & PCB’s in 1970’s • IPM to reduce pesticides, use fewer fertilizers • Recycling • Industries must separate their wastes to remove metals which can be sold to other companies that use it for their products

  6. Non-Point Reduction • Generally due to runoff, precipitation, leaching, etc. where there isn’t a single pollution source • Much harder to control and identify • Preserving wetlands to filter pollutants • Urban runoff- recycle waste oil instead of sending down drains, pick up trash, minimize fertilization & pesticide application in your yard, banning phosphate detergent use

  7. MUNICIPAL WATER PURIFICATION PLANTS Treats water to send to homes for municipal use.

  8. Municipal Water Purification Plant

  9. 1. Screening 2. Aeration 3. pH correction 4. Coagulation and flocculation 5. Sedimentation 6. Pre-chlorination and dechlorination 7. Filtration 8. Disinfection 9. pH adjustment Water Treatment Plant Stages Depending on the type of treatment plant and the quality of raw water, treatment generally proceeds in the following sequence of stages: • As required, other steps will be added, depending on the chemistry of the treated water.

  10. Initial Stages 1. Screening - removal of any coarse floating objects, weeds, etc. 2. Aeration - dissolving oxygen into the water • promotes helpful bacteria growth • precipitates nuisance metals like iron and manganese. 3. pH correction - preparing for coagulation and to help precipitate metals – mimics acid rain on soils. isis.csuhayward.edu/alss/Geography/ mlee/geog4350/4350c4f01.ppt

  11. Coagulation and flocculation – • add coagulating agent • causes agglomeration (clumping) - sludge/floc • Sedimentation – • Flocsettles out and is scraped and vacuumed off the bottom of large sedimentation tanks. • Water is carefully decanted off the top

  12. Filtering Out What’s Left • Pre-chlorination and dechlorination - mostly to kills algae and much of the remaining bacteria • Filtration (depends on size of plant/volume of water considerations) • Usually a sand filter of some size

  13. Final Touches 8. Disinfection - water completely free of suspended sediment is treated with a powerful oxidizing agent usually one of three types: • Chlorine • Chloramine (chlorine then ammonia) • Ozone- more expensive • UV-light 9. pH adjustment - desired range of 6.5 to 8.5 pH units.

  14. Possible Additional Steps • Heavy metal removal • Troublesome organics: Activated carbon filters for pesticides, phenols and MTBE (gasoline additive)

  15. WASTEWATER TREATMENT PROCESS

  16. Wastewater Treatment • Usually refers to sewage treatment, or domestic wastewater treatment • Process of removing contaminants from wastewater, both runoff and domestic, using the same processes of purification that would occur in a natural aquatic system

  17. Wastewater Treatment • Types of treatment systems include: • Septic Tankstreat small volumes of waste (e.g., from a single household, small commercial/industrial) • WasteWater Treatment Plants (WWTPs)treat larger volumes of municipal or industrial waste.

  18. SEPTIC TANKS

  19. In rural areas or in particular urban communities in the U.S., human wastewater will be treated through individual septic tank systems • Microorganisms breakdown waste • Wastewater is filtered thru soil & rocks of leachfield • If no leachfield, septic truck sucks out waste & sends to WWTP. • Septic tanks are easier & faster to install than sewage system, but prevent fast recycling of water back to ecosystem.

  20. Septic Tanks • Approx. 22 million systems in operation ( 30% of US population) • Suitability determined by soil type, depth to water table, depth to bedrock and topography • Commonly fail due to poor soil drainage

  21. WASTEWATER TREATMENT PLANTS (WWTP’S)

  22. Preliminary treatment • Remove large objects via screens • Ex: sticks, rags, toilet paper, tampons • Clog equipment in sewage treatment plant

  23. Treatment stages - Primary treatment • Typical materials that are removed during primary treatment include • fats, oils, and greases (aka FOG) • sand, gravels and rocks (aka grit) • larger settlable solids including human waste

  24. Treatment stages - Secondary treatment • Degrade biological content (dissolved organic matter) of the sewage • Ex: human waste, food waste, soaps, detergent • Added bacteria and protozoa into sewage • Requires aeration to keep oxygen levels high to promote decomposition • Sludge is sent to landfill or incinerated. If no toxic metals present, could be used for fertilizer

  25. Sludge Treatment - Composting • aerobic process • requires the correct mix of carbon, nitrogen, oxygen and water with sludge • Generate large amount of heat

  26. Sludge disposal • Superheat sludge and convert into small granules that are rich in nitrogen • Sell it to local farmer as fertilizer • Spread sludge cake on the field • Save landfill space

  27. Treatment stages – Tertiary treatment • remove disease-causing organisms from wastewater • 3 different disinfection process • Chlorination • UV light radiation • Ozonation

  28. Chlorination • Most common • Advantages: low cost & effective • Disadvantages: chlorine residue could be harmful to environment

  29. UV light radiation • Damage the genetic structure of bacteria, viruses and other pathogens. • Advantages: no chemicals are used • water taste more natural • Disadvantages: high maintenance of the UV-lamp

  30. Ozonation • Oxidized most pathogenic microorganisms • Advantages: safer than chlorination fewer disinfection by-product • Disadvantage: high cost

  31. Advanced Treatment • Nitrogen removal • Ammonia (NH3) → nitrite (NO2-)→ nitrate (NO3-) • Phosphorous removal • Precipitation with iron or aluminums salt • Lead to eutrophication!! • May cause algae bloom

  32. Summary Link to Water Filter

  33. Reusing Wastewater • Cannot directly mix treated wastewater with treated raw water and supplied as potable (drinking) water. • Can use a dual plumbing system to supply wastewater into facilities for specific, approved uses for which non-potable water (or grey water) is adequate • Processing water in manufacturing process • Irrigation • Car washing • Toilets

  34. Alternatives to WWTP • Effluent sewerage- several septic tanks connected to one mini-treatment plant- no drainfield • Use artificial wetlands • Fairly common in Europe, limited usage in US • Sewage/contaminated water is piped to holding ponds, sediment settles, water passed to wetland where plant roots filter & cleanse, microorganisms decompose

  35. Questions

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