Drinking Water Treatment

Intakes

Surface Water

Reservoirs

Groundwater

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.

Initial Treatment

screens Sedimentation(flocculation)

90 – 99% viruses

Filtration

Final Treatment

Disinfection and Fluoridation

Chlorine GasHypochlorite

Sodium Fluoride (NaF)Sodium fluorosilicate

Home Water QualityHome Water Quality

Florida’s Drinking WaterFlorida’s Drinking Water

Plio-pliestocene (sands)

Eocene Limestone

Miocene (clays)

Limestone

Pumped well

Confined AquiferConfined Aquifer

Potential Problems:

• Hardness• Iron + manganese• Sulfur (sulfides)• Salt/Salinity• Pathogens (bacteria/viruses)• Metals • Organics

Can be toxic or nuisance contaminants

Nuisance ContaminationNuisance Contamination

HardnessIronTurbidityColorOdorTaste

HardnessHardness

Calcium + Magnesium

Soap scum, scale, cooking problems

ClassificationClassification mg/l or ppmmg/l or ppm

SoftSoft 0 - 17.10 - 17.1

Slightly hardSlightly hard 17.1 - 6017.1 - 60

Moderately hardModerately hard 60 - 12060 - 120

HardHard 120 - 180120 - 180

Very HardVery Hard 180 & over180 & over

Calcium Deposits

Hardness TreatmentHardness Treatment

Water softeners 35 gal/day/person

Hard water

Soft water

Cation ExchangeResin

Neg. Charge

Na Na

Na Na

Na Na

Na

Na

Cation Exchange ResinsCation Exchange Resins

Ca2+, Mg2+

Neg charge

Na

Na

Na

Na

Mg2+

Ca2+

Na Na

Na Na

Na Na

Na

Na Na

4 Na+

Water Hardness and Soap Scum

Soap/DetergentSoap/Detergent

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

Oil drop(C,H,O)

-SO4Na+

Sodium dodecylsulfate

Extremely soluble

Ca+2-SO4

-SO4

+

Less soluble

Harmful ContaminantsHarmful Contaminants

Drinking WaterDrinking Water

Potable Water

• Pathogens• Harmful Minerals/Metals• Organic Chemicals

Free of

ToxicityToxicity

Acute Toxicity

Chronic Toxicity

Within 48 hours

• Long term• Frequent exposure• Small amounts• Pb, As, Hg

ContaminantsContaminants

Heavy MetalsHeavy Metals

Lead 0.05Silver 0.05Mercury 0.0002

Metal MCL (mg/L)

MCL = Maximum Contaminant Level

Other MetalsOther Metals

Trace Metals required metabolic catalysts

ManganeseIronCobaltCopperZincMolybdenumChromium

Toxicity = > 40 x requirement

NitratesNitrates

MCL = 10 mg/LNO3-

AgricultureOrganic Waste Disposal

NO3- NO2

-

Methemoglobin is a form of hemoglobin that does not bind oxygen.

bacteria

Infants under 6 months are particularly susceptible

PathogensPathogens

Coliform bacteria MCL < 1 bacterium / 100 ml

Single required test: Sanitary Quality

(fecal contamination)

Non-coliform bacteria MCL < 200 bacteria / 100 ml

Suggested test: mineral/metal content

TreatmentTreatment

Sanitation/Disinfection

Chlorination Most common

Boiling

UV Radiation

Ultraviolet RadiationUltraviolet Radiation

BacteriaVirusesMoldYeast Algae

Scrambled DNA

Home Treatment

Ceramic Filtration

Carbon

Ion Exchange

Water Filters

3-stage water filtration

Ion Exchange Filters

Neg. Charge

Na Na

Na Na

Na Na

Na

Na

Pb2+, Hg2+

Neg charge

Na

Na

Na

Na

Pb2+

Hg2+

Na Na

Na Na

Na Na

Na

Na Na

4 Na+ Finite Capacity

Metals

     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

Activated CarbonActivated Carbon

Activation by heating

Extremely porous with high surface area: 500 m2/g

Activated CarbonActivated Carbon

Filtration

Particle size removal > 0.5 microns (bacteria, fungi)

Activated CarbonActivated Carbon

Absorption: spontaneous movement of primarily organic contaminants from water to carbon matrix.

Pesticides, volatile organics

2,4-D2.4.5-TP (Silvex)AlachlorAtrazineCarbofuranChlordaneEndrinHeptachlor EpoxideLindaneMethoxychlorSimazineToxapheneBenzeneCarbon TetrachlorideChlorobenzene

EthylbenzeneMonochlorobenzeneMTBEO-DichlorobenzeneP-DichlorobenzeneStyreneTetrachloroetheneTolueneTrichloroetheneVOCs

AntidepressantsSteroids/HormonesPrednisone, Prednisolone,Progesterone, Testosterone,Cortisol/HydrocortisoneAntibiotics

Carbon Filter Removal

Reverse OsmosisExtremely Effective

OsmosisOsmosis

Salt molecule

Membrane permeable to Water only

Net movement of water

Spontaneousmovement of water

No salts

Reverse OsmosisReverse Osmosis

Membrane permeable to Water only

Purified water

Contaminants to drain

pressure

Energy intensive

Saline/contaminant by-product

inefficient: high volume reject water

Drawbacks:

Chlorine

Activated Carbon Filters

TastesOdors

Organics

Ion Exchange Resins

Removal of chargedContaminants (metals)

Reverse Osmosis

Sediments, viruses, bacteria, dissolved solutes

What about Bottled Water?

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 32-54 million barrels of oil

In 2007, US consumers purchased more than 33 billion liters of bottled water

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

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 meetthe U.S. Pharmacopeia definition of purified water. Purified water is essentially freeof all chemicals. Reverse osmosis is often used.

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

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 inplastic 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 unidentifiedchemicals in plastics have the potential to interfere with estrogen and other reproductive hormones

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 sourcein the ground at a German bottling plant. The water had 4 ppt of antimony before being bottled, the contents of a new bottle had360 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

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?