The Water Cycle. The Water Cycle. The Water Cycle. 13,000 Atmosphere (111,000) Ice & Snow 33,000,000 (71,000) (385,000) km 3 (km 3 /yr) (40,000)

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1 The Water Cycle Ice & Snow 33,000,000 (111,000) (71,000) 13,000 Atmosphere km 3 (km 3 /yr) (40,000) (385,000) (425,000) Groundwaters 15,300,000 Oceans 1,350,000,000 The Water Cycle 0.001% Atmosphere Ice & Snow 2.1% 0.2 % Inland Waters (Surface Waters) Groundwaters 0.6% Oceans 97.1% The Water Cycle All Water Fresh Water Readily Available Ground Water 0.6% Lakes 0.006% Biota Rivers Oceans 97.4% 100 liters (26 gal) Ice Caps & Glaciers 2% 3 liters (0.8 gal) Soil Moisture 0.004% liters (1/2 tsp) Atmos H 2 O 0.001% 1

2 The Water Cycle Groundwaters Freshwater found under the earth s surface e.g. Aquifers & Surface waters Freshwater found on the earth s surface Replenished by precipitation (Renewable but finite)» Rivers» Lakes» Ponds» Reservoirs» Wetlands The Water Cycle - Groundwater Aquifers Water Table Vadose Zone Porous Rock The Water Cycle - Groundwater recharge recharge Aquifers Groundwater travels slowly: several millimeters to a few meters per day. 2

3 The Water Cycle - Groundwater Artesian well Aquifers Water table well The Water Cycle - Groundwater Groundwater is a NON-renewable resource It takes 100 s to 1000 s of years for groundwater to accumulate and only a small % is replaced each year. The Water Cycle - Groundwater» The world s largest aquifer, 3.3 B acre-feet, would cover lower 48 states to about 2 feet deep» Every year, 6 million acrefeet withdrawn, about 14 B gallons per day for farming and 330 M gallons per day for human consumption» But recharge is only 185,000 acre-feet per year» Will be depleted some time in the next 200 years 3

4 Water Pollution - Introduction Groundwater Pollution Sources pollutants rain-out HW VOCs evaporate septic system landfill nitrates & phosphates (farm runoff) gasoline storage sewer hazardous waste holding tank leaking well-casings Water Pollution - Introduction Urban Water Pollution Sources organic wastes, garbage, animal droppings, grass and leaves Zinc (Zn) from aging pipes and gutters N & P from fertilizers Copper (Cu) from brake linings, worn pipes and fittings used motor oil storm-drain runoff Water Pollution - Introduction 4

5 Water Pollution - Clean Drinking H 2 O U.S. Popul 270 M U.S. Popul with Muni H 2 O 232 M 86 %» Sources of municipal water include:» Streams, rivers, lakes, aquifers and reservoirs» Most municipal water supplies are treated before being used» Treatment is a 2-4 step process Water Pollution - Clean Drinking H 2 O Treatment is a 2-4 step process 1. Aluminum sulfate [Al 2 (SO 4 ) 3 ] is added to decrease turbidity (i.e. cloudiness). Usual steps 2. The water is filtered through sand, which removes suspended particles and micro-organisms 3. Water may be pumped through charcoal (e.g. a giant Brita filter) 4. Water is disinfected Water Pollution - Disinfection Three methods of disinfection in use: Chlorination Ozonation Radiation Chlorine (e.g. as bleach or as chlorine gas) used to kill microorganisms Most common - least $$$ bad stuff in H 2 O + chlorine worse stuff in H 2 O? 5

6 Water Pollution - Disinfection Three methods of disinfection in use: Chlorination Ozonation Radiation Ozone [O 3 ] used to kill microorganisms Less common, used more in Europe than U.S. - more $$$ Side-effects not well known Water Pollution - Disinfection Three methods of disinfection in use: Chlorination Ozonation Radiation Ultraviolet (UV) radiation used to kill microorganisms Common in Europe - more $$$ No ill-health effects Water Pollution - Treating Wastewater Three steps: Primary Secondary Tertiary screen primary Physical process sand settling tank to secondary treatment or disinfection 11% population served by pri. ONLY primary sludge 6

7 Water Pollution - Treating Wastewater Three steps: Primary Secondary Tertiary Biological process secondary 62% of the population served by primary and secondary primary aeration tank to tertiary treatment or disinfection settling tank sec. sludge digested sewage sludge Water Pollution - Treating Wastewater Three steps: Primary Secondary Tertiary waste in septic system scum wastewater sludge treated water out Water Pollution - Treating Wastewater Three steps: Primary Secondary Tertiary Physical, biological and/or chemical process» Physical - filtration through sand and/or charcoal» Biological - addition of phosphate absorbing microorganisms» Chemical - addition of calcium hydroxide to remove phosphates 23% population Served by primary, secondary and tertiary 7

8 Water Pollution - Treating Wastewater phosphorus tertiary secondary primary chlorination nitrogen viruses dissolved organics pathogenic bacteria sewage solids Disease-causing Agents Municipal water sources generally contains many bacteria, viruses, protozoa, parasitic worms and other infectious agents that cause human or animal diseases Diseases transmitted through water include: Typhoid - bacterium Cholera - bacterium Bacterial dysentery - bacterium Amoebic dysentery - protozoan Polio - virus Infectious hepatitis (type A) - virus Disease-causing Agents EXAMPLE - Summer of 1993, Milwaukee, WI Water supply contaminated by a protozoan cryptosporidium not killed by chlorine - killed by ozone About 400,000 people developed cases of diarrhea and cramps that lasted up to 22 days! About 100 people died. Milwaukee has since spent $36.5 M on an ozonation system to kill parasites at an annual cost of $600,000. 8

9 Monitoring for Sewage Disease-causing agents generally carried into the waste stream by human and animal fecal matter Harmless fecal coliform bacteria are found in the fecal matter of warm-blooded animals E. coli is a specific type of fecal coliform bacteria and is found in our intestines by the BILLIONS Therefore we can test for the presence of E. coli as an indirect indication of fecal contamination and thus disease-causing agents Sewage Sewage - wastewater from toilets, washing machines, showers, etc - includes human wastes, soaps and detergents Carries disease-causing agents Creates oxygen demand Causes enrichment Water Pollution - Oxygen Demand Sewage is decomposed by aerobic microorganisms (CH 2 ) n + O 2 CO 2 + H 2 O carbon dioxide & water sewage is made up of mostly carbon & hydrogen oxygen is dissolved in the water dissolved oxygen (DO) is limited and as the temperature increases the DO decreases bacteria compete with all other organisms for oxygen in the water 9

10 Water Pollution - Oxygen Demand Problems are exacerbated by thermal pollution - as temp rises oxygen levels decrease and stressed fish use it faster O 2 direction of flow We measure the amount of sewage (i.e. organic waste) in terms of BOD & COD Sewage = BOD = Water Pollution - BOD & COD Organic waste that bacteria CAN eat biochemical oxygen demand + Organic waste that bacteria CAN NOT eat COD = chemical oxygen demand COD BOD Water Pollution - BOD Sources Sewage - also referred to as oxygen consuming wastes because of the oxygen required to decompose them Sources: Humans and animals Paper mills Tanneries Slaughterhouses Meat packing plants 10

11 Inorganic Plant Nutrients Fertilizer runoff from agricultural and residential land is a major contributor of inorganic plant and algal nutrients which cause excessive growth of plants.» Two key nutrients: nitrates & phosphates - NO 3 PO -3 4» Excessive growth of plants and algae can cause:» Bad odors» High BOD» Enrichment Inorganic Plant Nutrients Inorganic Plant Nutrients Main sources of nitrates and phosphates include:» Nitrogen-containing human waste» Phosphorus-containing detergents» Nitrates and phosphates in fertilizers» Industrial discharge» Phosphate mining 11

12 Heavy Metal Pollutants Main sources of inorganic pollutants include:» Industries» Mines» Irrigation runoff» Oil drilling» Urban sewer runoff Many are toxic, but we will limit our discussion to lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr) and arsenic (As). Heavy Metal Pollutants U.S. Environmental Protection Agency has established maximum permissible levels in drinking water for 11 metals:» Antimony, arsenic, barium, beryllium, cadmium, chromium, lead, mercury, nickel, selenium and thallium Additionally, they also regulate radium (Ra), uranium (U) and all other alpha and beta emitters Heavy Metal Pollutants - Lead (Pb)» Lead-based paint was banned in the U.S. in 1978, but the EPA estimates that more than 3/4 of all U.S. homes still have lead present.» Most people think of lead poisoning as being an inner-city problem when in fact lead is everywhere. There are many sources of lead contamination.» Natural sources:» Volcanoes» Wind-blown dust 12

13 Heavy Metal Pollutants - Lead (Pb) Anthropogenic sources:» Antiknock agents in gasoline (e.g. tetraethyl lead)» Paint» Solder» Lead-acid batteries» Leachate from incinerator ash» Old factories that lack air-pollution control devices» Pesticide residues (e.g. PbAsO 3 )» Dinnerware (e.g. ceramics, leaded-crystal) Heavy Metal Pollutants - Lead (Pb)» According to the EPA during the mid-1990s more than 10% of all large and medium-sized municipal H 2 O supplies contain lead levels higher than those allowed by the Safe Drinking Water Act - 5 ppb at source» Additionally, tap water often contains HIGHER levels than those present in the municipal supply (e.g. Boston)» The current U.S. Pb drinking water standard is 15 ppb at a 10% action level. Heavy Metal Pollutants - Lead (Pb)» Millions of Americans (many of them children) have damaging levels of lead in their bodies. According to the Agency for Toxic Substances and Disease Registry (located in Atlanta, GA) 17% of American children have blood lead levels that exceed 150 ppb; the dangerous level is set at 100 ppb.» Three groups at greatest risk:» Middle-aged men (hypertension)» Pregnant women (miscarriage, still-birth, premature delivery)» Children (partial hearing loss, hyperactivity, ADD, lowered IQ, learning disabilities) 13

14 Heavy Metal Pollutants - Mercury (Hg)» Small amounts of mercury occur naturally in the environment. However, because it is used in a variety of industrial processes, its presence is widespread.» Sources include:» Combustion of coal - 40 Million tons annually» Industrial wastewater release» Incineration of household trash - batteries, paints, plastics» Mining for precious metals in lesser developed countries (e.g. S. America) Heavy Metal Pollutants - Mercury (Hg)» In its natural state mercury is relatively harmless - probably pass right through your system.» However anaerobic bacteria, easily convert it to an organic form - methylmercury which is readily absorbed by humans and aquatic organisms (e.g. salmon, tuna, swordfish, shark).» Methylmercury persists in the environment and prolonged exposure causes - retardation, kidney failure, irreversible CNS damage and death. Heavy Metal Pollutants -Cadmium (Cd)» Cadmium has many uses. We find it in -» Paints, plastics, Ni-Cad batteries and Cadmium sulfide photodetectors» Even with all these sources, a major concern is its presence as a contaminant in zinc ore» So wherever zinc is used, cadmium is present» Intake of cadmium is known to increase the risk of heart disease... it is also known to displace zinc from the liver 14

15 Heavy Metal Pollutants - Chromium (Cr) Cr(III) is not harmful to humans Cr(VI) is harmful and is generally present as chromate CrO 4-2, which mimics sulfate in the body Heavy Metal Pollutants - Arsenic (As) Arsenic occurs naturally in the environment highest levels lowest levels insufficient data Heavy Metal Pollutants - Arsenic (As) Current std is 50 ppb supposed to be lowered to 10 ppb conc [ppb] > < 5 15

16 Heavy Metal Pollutants - Arsenic (As)» Arsenic occurs naturally in rocks and soil, air, water, plants and humans.» Natural sources include» Volcanoes» Erosion of rocks» Forest fires» Anthropogenic sources include» Wood preservatives» Paints, dyes» Drugs, soaps» Long term exposure can cause skin lesions and keratosis and has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate.» Low exposures have been shown to cause cardiovascular, pulmonary, immunological, neurological and endocrine effects. 16