INTRODUCTION• Most urban centers in Africa and Asia have no sewage system at all including many cities with populations over one million people. Result is tragic rate of morbidity and mortality in less developed parts of the world.• Water born diseases such as Cholera and Typhoid cause more than 1.5 billion episodes of diarrhea each year, resulting in 4 million deaths annually (UNEP, 1993).
UNUSUAL PROPERTIES OF WATER• 2 Hydrogen to Oxygen chemical bonds form a 105° angle with each other, resulting in a molecule that has a slightly positive charge at one end and a slightly negative charge at the other.
UNUSUAL PROPERTIES OF WATER• This dipolar character means water molecules are attracted to each other.• This dipolar property shows, Water boils at high temperature and need an unusual amount of energy to cause it to vaporize.• This also shows, water has high surface tension to allow heavy objects such as insects to keep on surface, adheres to other surfaces easily.
UNUSUAL PROPERTIES OF WATER• Combination of surface tension and adhesion lets water crawl up the sides of objects- it causes to Sap to rise in trees, Water to raise in soil, and food to move through organisms.• The dipolar property also makes water a very effective solvent since water molecules tend to surround charged ions and effectively neutralize them.
UNUSUAL PROPERTIES OF WATER• Density: Water expands when it freezes. Maximum density at 4°C, below 4°C becomes lighter, hence ice floats on surface. Above 4°C becomes lighter, hence warm water floats on top of cold water in lakes.
UNUSUAL PROPERTIES OF WATER• Melting and Boiling Point: High boiling and freezing (0°C) temperatures, High difference in temperature between Melting point (0°C) and Boiling point (100°C), thus remaining a liquid over most of the globe.
UNUSUAL PROPERTIES OF WATER• Specific Heat: Higher heat capacity (4184J/ kg °C) than any liquid except ammonia, 5 times higher than specific heat of most common heavy solids, such as rock and concrete. As a result it takes longer to heat up and to cool down water than almost anything else. This high heat capacity helps make the oceans the major moderating factors in maintaining the temperature of the surface of earth.
UNUSUAL PROPERTIES OF WATER• Heat Of Vaporization: The heat required to vaporize water (2258 KJ/ kg) is one of the highest of all liquids. It means water vapor stores large amount of energy, energy that is released when the water vapor condenses. This property distributes heat from one place on the globe to another and is major factor affecting the earth’s climate.
UNUSUAL PROPERTIES OF WATER• Water as Solvent: It dissolves more substances than any other common solvent.• Greenhouse Effect: H2O Vapor is in fact the most important green house gas in our atmosphere. H2O Vapor in atmosphere absorbs solar energy. H2O molecules absorb infrared radiation leaving the earth surface.
THE HYDROLOGIC CYCLE:• 97% of water in oceans.• High concentration of salts makes it unusable.• Evapotranspiration removes an amount of water equivalent to a layer about 1 meter thick around the globe each year.• 88% evaporation is from the oceans, 12% Evapotranspiration from land
THE HYDROLOGIC CYCLE:• Removing water from wet surfaces by evaporation, removing water from leaves from leaves of plants by transpiration. Combination of processes is called Evapotranspiration.• The resulting water vapor is transported by moving air masses and eventually condenses and returns to earth.• Over the ocean, there is more evaporation than precipitation.
THE HYDROLOGIC CYCLE:• Over the land, there is more precipitation than Evapotranspiration.• Precipitation – Evapotranspiration = Runoff (The difference between Precipitation and Evapotranspiration on land is water that is returned to the oceans both by flow and ground water flow, as runoff.• 60% of precipitation falling on earth’s land masses is returned to atmosphere.
THE HYDROLOGIC CYCLE:• 40% of collects on surface, flowing into streams and rivers and emptying into oceans, while some seeps into soil to become underground water that slowly moves toward the seas.• This runoff water 47,000 km3/year is a renewable supply of fresh water that can potentially be used year after year without ever depleting the fresh water resources of the world.
STOCKS OF WATER ON EARTH Location Amount 106Km3 Percent of Water SupplyOceans 1338 96.5Glaciers and permanent 24.1 1.74snowGround Water 23.4 1.70Ground ice/ Permafrost 0.30 0.022Fresh water lakes 0.091 0.007Saline lakes 0.085 0.006Swamp Water 0.011 0.008Atmosphere 0.013 0.001Average in stream 0.002 0.002channelsWater in living biomass 0.001 0.001 Source = Shiklomanov (1993)
WATER USAGE• 10 % of world’s runoff is withdrawn for human use each year.• Asia with 60% World’s population has only 36% global runoff.• South America with 5% World’s population has 25% of runoff.• Egypt depends on the Nile for 97% of its surface water supply, while its neighbor Ethiopia, controls all of the Nile’s total flow.
WATER USAGE• Similar circumstances exist all around the globe.• Withdrawal = Consumption + Returns• Following Scatter chart shows Per Capita water availability for North America, Africa and Asia due to growing population (Shiklomanov, 1993, reprinted by permission of Oxford University press).
WATER USAGE 45Per Capita Water Availability thousands m3/ year 40 North America 35 Africa 30 25 Asia 20 15 10 5 0 1920 1940 1960 1980 2000 2020
WATER POLLUTANTS• Withdrawal water is used for some purpose and returned with pollutants.• Agriculture return water contains pesticides, fertilizers, and salts.• Municipal return water carries human sewage.• Power plants return water has high temperature.• Industry return water contains chemical pollutants and organic wastes.
WATER POLLUTANTSPATHOGENS:• Pathogens are disease-causing organisms that grow and multiply within the host.• The resulting growth of microorganisms in a host is called an infection.• Examples of pathogens associated with water include Virus, Bacteria, Protozoan, and Helminthes.• Diseases include Cholera, Malaria, and Dengue.
WATER POLLUTANTSOXYGEN DEMANDING WASTES:• Oxygen Demanding Wastes are usually biodegradable organic substances contained in municipal waste water or influents from certain industries.• These oxidize in receiving body of water. As bacteria decompose these wastes, they utilize oxygen dissolved in water, which reduces remaining amount of dissolved oxygen (DO).
WATER POLLUTANTSOXYGEN DEMANDING WASTES:• Important measure of quality of water source is the amount of dissolved oxygen.• Saturated value of dissolved oxygen (DO) in water is 8-15 mg of oxygen/ liter of water.• For heavy fish population recommended amount of dissolved oxygen (DO) is minimum 5mg/ liter.
WATER POLLUTANTS• Nutrients: Nutrients are chemicals such as Nitrogen, Phosphorus, Carbon, Sulfur, Calcium , Potassium, Iron, Manganese, Boron, and Cobalt, which are essential to the growth of living things.• They are pollutants when their concentrations are sufficient to allow growth of aquatic plants, particularly algae.
WATER POLLUTANTS• Nutrients: There are over 21,000 known types of algae that are grouped into 7 different categories by microbiologists.• When algae die and decompose, their decomposition removes oxygen from H2O making the water unacceptable.
WATER POLLUTANTS• Nutrients: Important nutrients are Carbon, Nitrogen, and Phosphorus.• Carbon is available from alkalinity, atmosphere, and decaying organic matter.• Nitrogen is available from municipal wastewater discharges, runoff from animal feedlots, chemical fertilizers, and atmosphere.
WATER POLLUTANTS• Nutrients:• Nitrogen in water is found in the form of nitrate NO3, which is not toxic. Certain bacteria found in intestinal tract of infants convert nitrates NO3, nitrites NO2.• Phosphorous is available from agriculture runoff in heavily fertilized areas and domestic sewage from human feces and detergents.
WATER POLLUTANTS• Salts: Water naturally accumulates a variety of dissolved solids, or salts, as it passes through soils and rocks on its way to the sea.• These salts include cations and anions.• Cations are Sodium, Calcium, Magnesium, and Potassium.• Anions are Chloride, Sulfate, and Bicarbonate.
WATER POLLUTANTS• Salts: The concentration of dissolved solid is an important indicator of the usefulness of water for various applications.• For drinking water, maximum 500 mg/liter of total dissolved solids (TDS) is suitable.• For crops up to 1500 mg/liter TDS is acceptable with little loss of yield, But above 2100 mg/liter TDS, H2O is unsuitable for irrigation.
WATER POLLUTANTSSALTS:• Fresh water has concentration of total dissolved solids (TDS) less than 1500 mg/liter.• Brackish water has less than 5000 mg/liter TDS.• Saline water has above 5000 mg/liter TDS.• Sea Water contains 30,000 – 34,000 mg/liter TDS
WATER POLLUTANTS• Thermal Pollution: A large steam electric power plant requires an enormous amount of cooling water.• A typical nuclear plant warms about 150,000 m3 / hour of cooling water.• If that heat is released into a local river or lock, the resulting rise in temperature can affect the aquatic life
WATER POLLUTANTS• Heavy metals:• From a physical perspective, metals are characterized by high thermal and electrical conductivity, high reflectivity, and metallic luster, strength and ductility.• From a chemical perspective, metal is an element that will give up one or more electrons to form a cation in an aqueous solution. About 80 elements can be called metals.
WATER POLLUTANTS• Heavy metals:• In terms of their environmental impacts, the most important heavy metals are mercury (Hg), Lead (Pb), Cadmium (Cd), and arsenic (As).• Toxic metals are Aluminium, Beryllium, Bismuth, Cadmium, Chr omium, Cobalt, Copper iron, Lead, Manganese, Mercury, Nickel, Seleni um, Strontium, Thallium, Tin, Titanium, and Zinc.
WATER POLLUTANTS• Heavy metals:• Metals are non-degradable.• Chromium and iron are essential nutrients, but high doses have bad impacts on the body including nervous system and kidney damage, creation of mutations, and induction of tumors.• Metals may be inhaled, and they may be ingested like Lead and Mercury.
WATER POLLUTANTS• Heavy metals:• Liquid Hg is less toxic, but Mercury vapor is highly toxic. Hg vapor enters the lungs and diffuses into blood stream. When this blood reaches the brain, causes serious damage to the central nervous system.• Lead vapor is less toxic, but most dangerous when it is dissolved into its ionic form Pb++.
WATER POLLUTANTS• Heavy metals:• Lead dissolved in blood is transferred to vital organs including kidneys and brain, and causes damage.• Metals are eliminated through kidneys. Chemicals that are toxic to the kidneys are called nephrotoxic. Cd, Pb, and Hg are examples of nephrotoxic metals.
WATER POLLUTANTSPESTICIDES:• Pesticides are the chemicals that kill undesirable organisms.• Some water related pesticides are Insecticides, herbicides, rodenticides, and fungicides.• Pesticides have adverse effect on the life of human, birds, and animals.
WATER POLLUTANTS• Volatile organic compounds (VOC): These are commonly found contaminant in groundwater. They are used as solvent in industrial process. Following are five toxic Volatile organic compounds. Most toxic of five is vinyl Chloride (Chloroethylene). (1) Vinyl Chloride, (2)Tetrachloroethylene, (3)Trichloroethylene, (4)1,2-dichloroethane, (5)Carbon Tetrachloride
STATUS OF SURFACE WATER QUALITY• Body of water is said to be impaired when at least one of the designated beneficial uses, such as fish consumption, is not supported b the quality of water.• These beneficial uses of surface water are given on the next slide. (Source: U.S. EPA, 1994)
BENEFICIAL DESCRIPTOR USEAquatic life The water body provides suitable habitat for survival andsupport reproduction of desirable fish, shellfish, and other aquatic organisms.Fish Consumption The water body supports a population of fish free from contamination that could pose a human health risk to consumer.Shellfish The water body supports a population of shellfish free fromHarvesting toxicants and pathogens that could pose a human health risk to consumer.Drinking Water The water body can supply safe drinking water with conventionalSupply treatment.Primary Contact People can swim in the water body without risk of adverse humanrecreation health effects.Secondary People can perform activities (like Kayaking) on the water bodyContact recreation without risk of adverse human health effects from occasional contact with water.Agriculture The water quality is suitable for irrigating livestock.
STATUS OF SURFACE WATER QUALITYPercent of assessed lake acres impaired by pollution (a) by pollutants (b) bysources of pollution (U.S. EPA, 1994):(a) BY POLLUTANTPriority organic chemicals Siltation Organic Enrichment/ DO Nutrients Metals 0 10 20 30 40 50 Percent
STATUS OF SURFACE WATER QUALITY Percent of assessed lake acres impaired by pollution (a) by pollutants (b) by sources of pollution (U.S. EPA, 1994): (b) BY SOURCE Onsite wastewater disposed Municipal Point SourseHydrologic/ habitat modification Urbon runoff/ storm Sewers Agriculture 0 10 20 30 40 50 60 Percent
STATUS OF SURFACE WATER QUALITY Percent of assessed river miles impaired by pollution (a) by pollutants (b) by sources of pollution (U.S. EPA, 1994): (a) BY POLLUTANTOrganic Enrichment/ DO Peticides Pathogen indicators Nutrients Siltation 0 10 20 30 40 50 Percent
STATUS OF SURFACE WATER QUALITYPercent of assessed river miles impaired by pollution (a) by pollutants (b) bysources of pollution (U.S. EPA, 1994):(b) BY SOURCEHydrologic/ habitat modification Silviculture Industrial point sourse Resourse extraction Urbon runoff/ storm Sewers Municipal Point Sourse Agriculture 0 10 20 30 40 50 60 70 80 Percent
WATER TREATMENT SYSTEMS• Purpose is to bring raw water up to drinking water quality.• Surface water tends to have more contamination, so filtration is a necessity.• Ground water is uncontaminated, has relatively little suspended solids, so filtration is less important.• Ground water may have objectionable dissolved gases and hardness (ions of calcium and magnesium).
WATER TREATMENT SYSTEMSWATER TREATMENT:A treatment plant for surface water includes thefollowing sequence of steps.(1) Screening: To remove large floating andsuspended debris.(2) Mixing the water with chemicals: Chemicalsencourage suspended solids to coagulate intolarge particles, which will settle more easily.(3) Flocculation: Process of gently mixing thewater and coagulant, allowing the formation oflarge particles of floc.
WATER TREATMENT SYSTEMSWATER TREATMENT:(4) Sedimentation and filtration: In theSedimentation, flow is slowed enough so thatgravity will cause the floc to settle. In thefiltration, effluent is cleaned.(5) Sludge processing: The mixture of solids andliquids collected from the settling tank isdewatered and disposed of.(6) Disinfection and fluoridation: To ensure thatthe water is free of harmful pathogens, and tocontrol dental caries.(7) Hardness Removal or Softening: It may beadded as an additional step for ground water.
WATER TREATMENT SYSTEMS WATER TREATMENT:Source Mixing Flocculation Settling Sand Disinfection Tank Basin Tank FilterScreening Fluoridation Addition of Sludge coagulant processing
HAZARDOUS WASTES• Hazardous substances or materials have some commercial value.• There are more than 1000 Hazardous chemicals.• Hazardous waste is a material that has been used, spilled, or is no longer needed.
HAZARDOUS WASTES• Hazardous waste is defined as “Anything which (because of its quantity, concentration, or physical, chemical, or infectious characteristics) may cause or significantly contribute to an increase in mortality; or cause an increase in serious (irreversible, or incapacitating reversible) illness; or pose a substantial present or potential hazard to human health and the environment when improperly treated, stored, transported, or disposed of or otherwise managed.”
HAZARDOUS WASTES• Hazardous substances have following four characteristic attributes:• (1) Reactivity: Reactive substances are instable under control conditions. They can cause explosions and/ or liberate toxic fumes, gases, and vapors when mixed with water.• (2) Ignitability: Ignitable substances are easily ignited and burn vigorously and persistently.
HAZARDOUS WASTES• Hazardous substances have following four characteristic attributes:• (3) Corrosivity: Corrosive substances include liquids with PH less than 2 or greater than 12.5. They are capable of corroding metal containers.• (4) Toxicity: Toxic substances are harmful or fatal when ingested or absorbed.
HAZARDOUS WASTES• Hazardous wastes are organized into following three categories:• (1) Source specific wastes: These include Sludges and wastes waters from treatment and production processes in specific industries.• (2) Generic wastes: These include wastes from common manufacturing and industrial processes.• (3) Commercial chemical products: These include benzene, creosote, mercury and various pesticides.
HAZARDOUS WASTE TREATMENT TECHNOLOGIES:• In the past, there was little treatment, and disposal was often on land.• Treatment technologies have following categories:• (1) Chemical treatment: It transforms waste into less hazardous substances using such techniques as PH neutralization, oxidation or reduction, and precipitation.• (2) Biological treatment: It uses microorganisms to degrade organic compounds in the waste stream.
HAZARDOUS WASTE TREATMENT TECHNOLOGIES:• (3) Physical treatment: It includes gravity separation, phase change systems such as air and steam stripping of volatiles from liquid wastes, various filtering operations including carbon adsorption.• (4) Thermal Destruction Process: These include incineration, and pyrolysis (chemical decomposition of waste brought about by heating the material in the absence of oxygen).
HAZARDOUS WASTE TREATMENT TECHNOLOGIES:• (5) Fixation/ Stabilization techniques: These involve removal of excess water from a waste and solidifying the remainder either by mixing it with a stabilizing agent, such as Portland cement, or vitrifying it to create a glassy substance.