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Community Chemistry

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Water

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Properties of water Water is less dense as a solid than a liquid. Only naturally occurring compound that does that. Has an unusually high boiling point for a liquid

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Properties of water Has a very high specific heat value (amount of energy needed to raise the temperature 1 o C). 4.2 J/g o C Water is known as The Universal Solvent. Best solvent, able to dissolve almost anything!

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In a water molecule two hydrogen atoms form bonds with one oxygen atom. Gives water more structure than other liquids The region around oxygen has a partial negative charge. The region near the two hydrogen atoms has a partial positive charge. A water molecule is a molecule with opposite ends of the molecule with opposite charges. Properties of water

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Cohesion among water molecules plays a key role in the transport of water against gravity in plants Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels. Properties of water Bonds in H 2 O hold the substance together, a phenomenon called cohesion

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Surface tension, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion. Water has a greater surface tension than most other liquids because bonds among surface water molecules resist stretching or breaking the surface. Water behaves as if covered by an invisible film. Some animals can stand, walk, or run on water without breaking the surface. Properties of water

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Water as a Mixture A mixture that has the same composition throughout the substance is called a homogeneous mixture. A Solution is a mixture that has the solute (the stuff that dissolves) and the solvent (the stuff that does the dissolving). Examples: Kool-Aid, Salt water, Orange Juice, etc

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Acids & Bases To measure the ________ of an acid or base, we look at that substances __________ to produce _________ ions in solution. strength potentialhydrogen We call this the ___ scale pH

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The pH Scale A substance with a pH less than 7 is an ______. acid A substance with a pH greater than 7 is a ______. base A substance with a pH equal to 7 is considered ________. neutral

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pH of Common Substances Timberlake, Chemistry 7 th Edition, page 335 1.0 M HCl 0 gastric juice 1.6 vinegar 2.8 carbonated beverage 3.0 orange 3.5 apple juice 3.8 tomato 4.2 lemon juice 2.2 coffee 5.0 bread 5.5 soil 5.5 potato 5.8 urine 6.0 milk 6.4 water (pure) 7.0 drinking water 7.2 blood 7.4 detergents 8.0 - 9.0 bile 8.0 seawater 8.5 milk of magnesia 10.5 ammonia 11.0 bleach 12.0 1.0 M NaOH (lye) 14.0 8 910 111214 13 34 5 6 2 1 70 acidic neutral basic [H + ] = [OH - ]

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Water Cycle Water covers about three-quarters of Earth's surface and is a necessary substance for life. During their constant cycling between land, the oceans, and the atmosphere, water molecules pass repeatedly through solid, liquid, and gaseous phases (ice, liquid water, and water vapor), but the total supply remains fairly constant.

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Evapotransporation Heat energy from the sun causes water in puddles, streams, rivers, seas or lakes to change from a liquid to a water vapor. This is called evaporation. Evapotranspiration water that is transferred into the atmosphere from evaporation, transpiration (from plants), and perspiration (from animals).

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Condensation Water vapor collects in clouds. As the clouds cool the water vapor condenses into water drops. This is called condensation. These drops fall to the earth as rain, snow or hail.

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Precipitation Water falls to the earth from clouds. Mainly as rain, but sometimes as snow and hail. This is called precipitation.

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Freshwater accounts for only some 6 percent of the world's water supply, but is essential for human uses such as drinking, agriculture, manufacturing, and sanitation. Large reserves are groundwater (4 percent) and icecaps and glaciers (about 2 percent). All other water bodies together accounting for a fraction of 1 percent. So, almost 2/3 of global freshwater is found underground and almost 1/3 is frozen! Freshwater Resources

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Water Use in the World and U.S. The world uses 338,000,000,000 gallons of water per day. The average U.S. person uses 1400 gal/day. (2 x that of a European person) This statistic includes direct and indirect water use. Humans only require 1 gal/day to survive. A person can only go about a week without water. However a person can go 30 days without food.

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Average water requirements Item Gallons used 1 pound of cotton 2,000 1 pound of grain-fed beef800 1 loaf of bread 150 1 car 100,000 1 kilowatt hour of electricity 25 1 pound of rubber 100 1 pound of steel 25 1 gallon of gasoline 10 1 load of laundry 60 1 ten-minute shower 25-50

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Drinking Water in the US The United States has one of the safest water supplies in the world. In recent years, microbial contamination of the water supply has led to highly publicized outbreaks of disease, causing illnesses. How safe is our water? Where do these infectious microbes come from? How is water treated now and whats being done to make it even safer?

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Drinking Water Treatment Water treatment transforms raw surface and groundwater into safe drinking water. Water treatment involves two major processes: physical removal of solids and chemical disinfection. COAGULATION: WATER TOWARDS SEDIMENTATION Coagulation removes dirt and other particles suspended in water. alum and other chemicals are added to water to form tiny sticky particles called floc which attract the dirt particles. The combined weight of the dirt and the alums (floc) becomes heavy enough to sink to the bottom during sedimentation.

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Water Treatment Raw Water Storage Mixing Flocculation Sedimentation Filtration Clear Well Distribution Ozonation Coagulant, pH Adjustment Disinfectant (Cl 2, NaOCl)

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Water Treatment FILTRATION, DISINFECTION & STORAGE: FILTRATION: The water passes through filters, some made of layers of sand, and charcoal that help remove smaller particles. DISINFECTION: A small amount of chlorine is added or some other disinfection method is used to kill microorganisms that may be in the water. STORAGE: Water is placed in a closed tank or reservoir for disinfection to take pace. The water then flows through pipes to home and business in the community WATER FROM SEDIMENTATION

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Water Disinfection Purpose of disinfection: To make Drinking water free of any disease causing bacteria and microbes. Methods of disinfection: There are 3 mainly used disinfection methods at large scale. CHLORINATION OZONATION ULTRAVIOLET RADIATION

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CHLORINATION Chlorine is the most common cost-effective means of disinfecting water in the U.S. The addition of a small amount of chlorine is highly effective against most bacteria, viruses, and protozoa. OZONATION OZONE is Strongest oxidant/disinfectant available. More effective against microbes than chlorination. But, costly and difficult to monitor and control under different condition.

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COAGULATION SEDIMENTATION FILTRATION DISINFECTION STORAGE COMPLETE CYCLE OF WATER TREATMENT:

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What is wastewater treatment? Usually refer to sewage treatment, or domestic wastewater treatment process of removing contaminants from wastewater, both runoff and domestic Residences (kitchen, bathroom) Commercial institutions Industrial institutions (usually require specialized treatment process) Where does wastewater come from? collected and transported via a network of pipes and pump stations to a municipal treatment plant How can it be treated?

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3 stages of water treatment Primary solids are separated Secondary dissolved biological matter is converted into a solid mass by using water-borne bacteria 95% of the suspended molecules should be removed Tertiary biological solids are neutralized then disposed, and treated water may be disinfected chemically or physically

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Sedimentation Treatment Remove grease, oil Solids settle, floating material rise to the surface Produce a homologous liquid for later biological treatment Sludge is pumped to sludge treatment plant Treatment stages Primary treatment

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Filters bed Spread wastewater over microorganism made of carbonised coal, limestone chips or specially fabricated plastic media Degrade biological content (dissolved organic matter) of the sewage Ex: human effluent, food waste, soaps, detergent Added bacteria and protozoa into sewage Treatment stages - Secondary treatment

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Treatment stages Tertiary treatment remove disease-causing organisms from wastewater Chlorination Most common Advantages: low cost & effective Disadvantages: chlorine residue could be harmful to environment 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 Ozonation Oxidized most pathogenic microorganisms Advantages: safer than chlorination fewer disinfection by-product Disadvantage: high cost

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What can the effluent be used for? discharged into a stream, river, bay, lagoon or wetland used for the irrigation of a golf course, green way or park If its sufficiently clean, it can be used for groundwater recharge Nitrogen removal Ammonia (NH 3 ) nitrite (NO 2 - ) nitrate (NO 3 - ) Phosphorous removal Precipitation with iron or aluminums salt Lead to eutrophication May cause algae bloom Advanced Treatment

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Summary

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Onondaga Lake Many different types of contaminants can pollute water and render it unusable. Pollutants regulated in the United States under national primary drinking water standards include: Microorganisms such as cryptosporidium, giardia, and fecal coliform bacteria Disinfectants and water disinfection byproducts including chlorine, bromate, and chlorite Inorganic chemicals such as arsenic, cadmium, lead, and mercury Organic chemicals such as benzene, dioxin, and vinyl chloride Radionuclides including uranium and radium

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Onondaga Lake