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Drinking Water Treatment. Intakes Surface Water Reservoirs Groundwater.

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Presentation on theme: "Drinking Water Treatment. Intakes Surface Water Reservoirs Groundwater."— Presentation transcript:

1 Drinking Water Treatment

2 Intakes Surface Water Reservoirs Groundwater

3 Aeration: The water is mixed to liberate dissolved gases and to suspended particles in the water column. Flocculation: The materials and particles present in drinking water (clay, organic material, metals, microorganisms) are often quite small and so will not settle out from the water column without assistance. To help the settling process along, "coagulating" compounds are added to the water, and suspended particles "stick" to these compounds and create large and heavy clumps of material. Filtration: The water is run through a series of filters which trap and remove particles still remaining in the water column. Typically, beds of sand or charcoal are used to accomplish this task. Disinfection: The water, now largely free of particles and microorganisms, is treated to destroy any remaining disease-causing pathogens. This is commonly done with chlorination or ultraviolet radiation.

4 Initial Treatment screens Sedimentation (flocculation) 90 – 99% viruses Filtration

5 Final Treatment Disinfection and Fluoridation Chlorine Gas Hypochlorite Sodium Fluoride (NaF) Sodium fluorosilicate

6 Home Water Quality

7 Florida’s Drinking Water

8 Plio-pliestocene (sands) Eocene Limestone Miocene (clays) Limestone Pumped well Confined Aquifer

9 Potential Problems: Hardness Iron + manganese Sulfur (sulfides) Salt/Salinity Pathogens (bacteria/viruses) Metals Organics Can be toxic or nuisance contaminants

10 Nuisance Contamination Hardness Iron Turbidity Color Odor Taste

11 Hardness Calcium + Magnesium Soap scum, scale, cooking problems Classification mg/l or ppm Soft Slightly hard Moderately hard Hard Very Hard 180 & over Calcium Deposits

12 Hardness Treatment Water softeners35 gal/day/person Hard water Soft water Cation Exchange Resin

13 Neg. Charge Na Cation Exchange Resins Ca 2+, Mg 2+ Neg charge Na Mg 2+ Ca 2+ Na 4 Na +

14 Water Hardness and Soap Scum

15 Soap/Detergent SO 4 - Oil drop (C,H,O)

16 - SO 4 Na + Sodium dodecylsulfate Extremely soluble Ca +2 - SO 4 + Less soluble

17 Harmful Contaminants

18 Drinking Water Potable Water Pathogens Harmful Minerals/Metals Organic Chemicals Free of

19 Toxicity Acute Toxicity Chronic Toxicity Within 48 hours Long term Frequent exposure Small amounts Pb, As, Hg

20 Contaminants

21 Heavy Metals Lead0.05 Silver0.05 Mercury MetalMCL (mg/L) MCL = Maximum Contaminant Level

22 Other Metals Trace Metals required metabolic catalysts Manganese Iron Cobalt Copper Zinc Molybdenum Chromium Toxicity = > 40 x requirement

23 Nitrates MCL = 10 mg/L NO 3 - Agriculture Organic Waste Disposal NO 3 - NO 2 - Methemoglobin is a form of hemoglobin that does not bind oxygen. bacteria Infants under 6 months are particularly susceptible

24 Pathogens Coliform bacteria MCL < 1 bacterium / 100 ml Single required test: Sanitary Quality (fecal contamination) Non-coliform bacteriaMCL < 200 bacteria / 100 ml Suggested test: mineral/metal content

25 Treatment Sanitation/Disinfection ChlorinationMost common Boiling UV Radiation

26 Ultraviolet Radiation Bacteria Viruses Mold Yeast Algae Scrambled DNA

27 Home Treatment

28 Ceramic Filtration Carbon Ion Exchange Water Filters 3-stage water filtration

29 Ion Exchange Filters Neg. Charge Na Pb 2+, Hg 2+ Neg charge Na Pb 2+ Hg 2+ Na 4 Na + Finite Capacity Metals

30 The solid carbon block faucet mount filters are reasonably effective in reducing contaminants. These filters, by nature, are quite smalland because filter effectiveness is dependent on contact time of the water with the filter media, a larger, high-quality solid carbon block filter will be more effective at reducing contaminants at the same flow rate. a high-quality solid block activated carbon replacement filter will filter water for between 7 and 10 cents per gallon. 2 gallons of filtered water per day would cost between $50 and $100 per year Most Common Filtration Solid Carbon Block faucet mount filters

31 Activated Carbon Activation by heating Extremely porous with high surface area: 500 m 2 /g

32 Activated Carbon Filtration Particle size removal > 0.5 microns (bacteria, fungi)

33 Activated Carbon Absorption: spontaneous movement of primarily organic contaminants from water to carbon matrix. Pesticides, volatile organics

34 2,4-D TP (Silvex) Alachlor Atrazine Carbofuran Chlordane Endrin Heptachlor Epoxide Lindane Methoxychlor Simazine Toxaphene Benzene Carbon Tetrachloride Chlorobenzene Ethylbenzene Monochlorobenzene MTBE O-Dichlorobenzene P-Dichlorobenzene Styrene Tetrachloroethene Toluene Trichloroethene VOCs Antidepressants Steroids/Hormones Prednisone, Prednisolone, Progesterone, Testosterone, Cortisol/Hydrocortisone Antibiotics Carbon Filter Removal

35 Reverse Osmosis Extremely Effective

36 Osmosis Salt molecule Membrane permeable to Water only Net movement of water Spontaneous movement of water No salts

37 Reverse Osmosis Membrane permeable to Water only Purified water Contaminants to drain pressure

38 Energy intensive Saline/contaminant by-product inefficient: high volume reject water Drawbacks:

39 Chlorine Activated Carbon Filters Tastes Odors Organics Ion Exchange Resins Removal of charged Contaminants (metals) Reverse Osmosis Sediments, viruses, bacteria, dissolved solutes

40 What about Bottled Water?

41 According to a NRDC study, U.S. consumers paid between 240 and 10,000 times more per gallon for bottled water than for tap water For the price of one bottle of Evian, Americans can receive 1,000 gallons of tap water The global consumption of bottled water reached 41 billion gallons in 2004, up 57 percent in just five years. More than 5 trillion gallons of bottled water is shipped internationally each year. Supplying Americans with plastic water bottles for one year consumes more than 47 million gallons of oil The energy required to produce 33 billion liters is equivalent to million barrels of oil In 2007, US consumers purchased more than 33 billion liters of bottled water

42 What’s the Source? More than 25 percent of bottled water comes from a public source. If water is packaged as "purified" or "drinking water," It likely originated from a municipal water supply, and unless the water has been “substantially” altered, it must state on the label that the water comes from a municipal source. Both Aquafina (Pepsi) and Dasani (Coca-Cola) originate from municipal water systems National Resource Defense Council

43 Other terms used on the label about the source, such as “glacier water” or “mountain water," are not regulated standards of identity and may not indicate that the water is necessarily from a pristine area Artesian water, groundwater, spring water, well water - water from an underground aquifer which may or may not be treated. Well water and artesian water are tapped through a well. Spring water is collected as it flows spontaneously to the surface or via a borehole. Ground water can be either. Distilled water - steam from boiling water is recondensed and bottled. Distilling water kills microbes and removes water’s natural minerals Drinking water – water intended for human consumption and sealed in bottles or other containers with no ingredients except that it may optionally contain safe and suitable disinfectants. Fluoride may be added within limitations Purified water - water that originates from any source but has been treated to meet the U.S. Pharmacopeia definition of purified water. Purified water is essentially free of all chemicals. Reverse osmosis is often used.

44 Is it safe? Most bottled water appears to be safe. (NRDC independent testing of 1000 bottles) EPA sets standards for tap water provided by public water systems; the Food and Drug Administration sets bottled water standards based on EPA's tap water standards Most bottled water is treated more than tap water; however, some is treated less or not treated at all. About 22 percent of the brands tested by NRDC contained, in at least one sample, some chemical contaminant

45 can leach into bottled water overtime. polyethylene terephthalate (PET) bottles PET phthalates known to disrupt testosterone and other hormones, One study found that water that had been stored for 10 weeks in plastic bottles contained phthalates, suggesting that the chemicals could be coming from the bottle, the plastic cap or the liner It also appears possible that some as-yet unidentified chemicals in plastics have the potential to interfere with estrogen and other reproductive hormones

46 The study stressed that amounts of antimony were well below official recommended levels. But it also discovered that the levels almost doubled when the bottles were stored for three months The study collected 48 brands of water in PET bottles from its source in the ground at a German bottling plant. The water had 4 ppt of antimony before being bottled, the contents of a new bottle had 360 ppt and one opened three months later had 700 ppt. The health effects of antimony ingestion are not well known Royal Society of Chemistry Publication Antimony The U.S. EPA has established 6.0 parts per billion (ppb) as a safe level

47 88% of water bottles are not recycled In 2005, 2 million tons of plastic water bottles were not recycled In 2006, 2 billion half-liter bottles of water were shipped to U.S. ports Where are all the old bottles?

48


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