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Metals and Mercury. Biological pollution. Discovery of coliform bacteria had the greatest impact on municipal water systems and water treatment. 1/3 weight of average uninfected human waste.

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Metals and Mercury


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Presentation Transcript
slide2

Biological pollution

Discovery of coliform bacteriahad the greatest impact

on municipal water systems and water treatment.

1/3 weight of average

uninfected human waste

Not necessarily a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present

Coliforms are naturally present in the environment; fecal coliforms only come from human and animal fecal waste.

slide3

Forms of Water Treatment

Suspended Solids

Flocculation

Sand filtration

Flocculation – bringing together of high numbers

of small particles to create larger particles which

settle out of water quickly.

Advanced treatment uses chlorine disinfection

To remove pathogenic organisms from water.

slide4

Scientists demonstrate that microorganisms can cause disease.

1880s

First application of chlorine disinfectants to U.S. municipal water facilities in Jersey City and Chicago.

1908

First U.S. drinking water bacterial standard.

1915

slide5

Over 1,000 U.S. cities employ chlorine disinfection.

1918

More than 19,000 municipal water systems operate throughout the U.S.

1960

slide6

Biological Pollution and Chlorination

Chlorine is currently employed by over 98 percent

of all U.S. water utilities that disinfect drinking water

slide7

Effectiveness of Chlorination: Typhoid Yardstick

174 per 100,000 persons died of Typhoid in 1891

bacterium Salmonella typhi

Deaths per 100,000

1860 1910 1935

Today: < 40 per 200 million people

slide9

Heavy Metals and Metalloids

Arsenic

Erosion of natural deposits; pesticide waste, runoff from glass & electronics production wastes, treated lumber, groundwater

Mercury

Erosion of natural deposits; discharge from refineries and factories; runoff from landfills, coal burning

Lead

Corrosion of household plumbing systems; natural deposits, paint, fuels, electronics

slide11

Arsenic

Wells in Floodplain

and Delta Sediments

Natural erosion of

arsenic to water-

bearing units.

Well depths between 20m and 100 m

Water Bearing Muds

slide12

WHO/U.S limit: 10 ppb

Bangladesh limit: 50 ppb

Some wells contain 500 - 1000 ppb

Majority of wells > 50 ppb arsenic

slide13

Lead (Plumbum)

Father of all metals

Possible cause of the

dementia which

affected Roman

Emperors and Citizens.

-lead pipes

-lead acetate

sugar of lead

sweetener for wine

Contemporary Sources:

Paint, ceramics, glass, soils, pipes,

Solder, brass faucets, gasoline

slide14

Mercury

Got Fish?

slide15

Mercury Advisories

70% of states

Where does it come from?

slide16

Enters water bodies principally from the atmosphere

Mercury is naturally occurring

(coal, volcanism, rock weathering)

The number 1 anthropogenic source

is the combustion of coal

48 tons of elemental mercury to the atmosphere each year.

slide17

Mercury

The drinking water standard for Mercury is 0.002 mg/L.

1 gram annually

Electrical products such as dry-cell

batteries, fluorescent light bulbs,

switches, and other control equipment

account for 50% of mercury used.

slide18

Fluorescent Lights

A typical fluorescent lamp is composed of a phosphor-coated

glass tube with electrodes located at either end. The tube

contains a small amount of mercury vapor. When a voltage is

applied, the electrodes energize the mercury vapor, causing

it to emit ultraviolet (UV) energy. The phosphor coating

absorbs the UV energy, causing the phosphor to fluoresce

and emit visible light.

Phosphor

Coating

Hg gas

UV

Voltage

slide19

Recycling and Handling

Each year, an estimated 600 million fluorescent lamps are disposed

of in US landfills amounting to 30,000 pounds of mercury waste.

slide20

Forms of Mercury

The dominant inorganic forms are Hgo and Hg2+.

Hg2+ often occurs as HgCl2 (mercuric chloride)

in many aqueous environments.

Hg2+

(inorganic) interacts with soil and sediment

particles (- charge) becoming part of lake

bottom sediments (limits availability)

slide21

- charge

Interaction with Sediment Particles

- charge

Small organic and

Inorganic particles

Hg2+

Hg2+

Hg2+

- charge

slide22

Mercury Bound to Sediments

Mercury, however, can undergo chemical

changes in lakes which render mercury

more environmentally dangerous

Hg2+

Hg2+

sediments

Negatively charged particles bind mercury

And retain it in bottom sediments.

- charge

slide23

Mercury Methylation

Mercury can be converted to more

toxic forms in bottom sediments

under anaerobic conditions

slide24

Mercury Methylation

Methylation: conversion of inorganic forms of mercury,

Hg2+,to an organic form: methyl mercury

under anaerobic conditions

Hg2+(CH3Hg+) metylmercury

Methylmercury is strongly accumulated in the body

and is generally more toxic than inorganic Hg

slide25

Mercury Methylation

  • Requires 4 elements:
  • anaerobic conditions
  • a carbon source (organic sediments)
  • a source of sulfur (SO4-)
  • sulfur reducing bacteria

Occurs primarily in bottom sediments as a byproduct of the life processes of anaerobic sulfate-reducing bacteria (SO4 to HS-) that live in high sulfur, low oxygen environments.

Sulfate Respiration

C6H12O6 + 3SO42- + 3H+ = 6HCO3- + 3HS-

When sulfur accepts electrons it is said to be “reduced”.

slide26

The exact role of sulfate-reducing bacteria

In mercury methylation is poorly understood

However, bacterial sulfate respiration requires sulfate.

The addition of sulfate to water stimulates the metabolic activity of sulfate-reducing bacteria and the inadvertent methylation of inorganic mercury

Sulfate concentrations in EAA runoff and Lake Okeechobee average more than 50 times background concentrations than in the pristine Everglades

Sulfate

slide27

Hg2+ from coal, volcanism, rock weathering, point sources

Water

Sediments

(Bound)

Sulfur reducing bacteria, low O2

methylmercury

Aquatic Organisms

slide28

Enhanced Risk

Methylmercury attaches to proteins in animals (enters food chain)

Methylmercury has a half-life in human blood of about 70 days

(almost twice as long as inorganic mercury (Hg2+).

Methylmercury is strongly accumulated in the body

and is generally more toxic than inorganic Hg

Bioaccumulation: concentration of a chemical in

organisms relative to the amount in water.

Biomagnification: concentration of a chemical in

organisms as it moves up the food chain.

slide30

Bioconcentration and Biomagnification

Chemical Concentration in organism

Chemical Concentration in water

BAF =

slide31

Minamata Bay

Chisso Corporation, a company located in

Kumamoto Japan, dumped an estimated

27 tons of mercury compounds into Minamata Bay

Between 1932 and 1968.

1963

plastics, drugs, and perfumes

acetaldehyde

As of March 2001, 2,265 victims had been officially recognized

(1,784 died) and over 10,000 had received compensation from Chisso

slide32

Assessing Your Risk

http://www.edf.org/page.cfm?tagID=17694

http://www.mercuryfacts.org/fSafeFish.cfm

Nearly all fish and shellfish contain traces of methylmercury.

However, larger fish that have lived longer have the highest

levels of methylmercury because they've had more time to

accumulate it. These large fish (swordfish, shark, king mackerel

and tilefish) pose the greatest risk.

Five of the most commonly eaten fish that are low in mercury are

shrimp, canned light tuna, salmon, pollock, and catfish.

Fish sticks and "fast-food" are commonly made from fish that are low in mercury.