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Lecture 3

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Environmental Science
Michael Petit

Lecture 3: Waterborne Hazards and Human Health Liquid natural capitol • Water generally is a liquid capitol, natural capitol • Why is it natural? Water is available everywhere in nature, we are surrounded by water • Even our body is mostly consisted of water • Earth is a water planet – 71% of our surface is covered with water • Not all of this water is available for us for our consumption • Why? Mostly salty water – we are surrounded by huge oceans and huge seas • Not much fresh water that we can use for human consumption and animal consumption • Why is water so important? No living species (animals, plants, or humans) can survive and live without water • We always think about drinking though water is not just for drinking • Everything in household from cleaning to cooking, industrial purposes, agriculture (for watering plants and crops) • There is a science called geomorphology that discusses sculpting the Earth’s surface • Water is one of the factors that changes the shape of planet Earth – this is called water erosion • One of the types of erosion is water soil erosion - changes, moving of the soil by water – water streams, surface runoff • Moderating climate – mild winter, hot summers (not that hot) • Water is a universal solvent – solve many different chemicals, same is the thing in nature • Water is involved in dissolving and diluting particles – can be good and something that we might not want • Water also dilutes wastes and pollutants – what happens is move water together with water stream/flow and reach rivers, lakes, ponds, oceans • Withdrawal- total amount of water removed from a river, lake or aquifer for any purpose • Some may be returned to the source for reuse • Use about 54% of the world's reliable runoff of surface water and could be using 70-90% by 2025 How much fresh water is available? • Not much fresh water is available on Earth • 97.4% of all water is found in oceans and saline lakes • 2.6% in fresh water is available • Of the 2.6% in fresh water most of it is captured as ice caps and glaciers (1.984%) • Water from ice caps and glaciers is not readily available (might be if global warming continues) • Groundwater composes of a significant amount of the fresh water • Groundwater is available for us but we need to pump it out to use it and consume it and also not use it more than it is replenished • There is only 0.014% of readily available fresh water • Of this, 0.007% is found in lakes, 0.005% as soil moisture, some significant amount of water is in atmosphere as water vapour and some as biota (all living organisms) • There are huge amounts of water stored in leaves and vegetation World’s Problems • Some areas have lots of water but the largest rivers are far from agricultural and population centers • Lots of precipitation arrives during short period but cannot be collected and stored • Shrank of lakes and rivers How do we use the world’s fresh water? • There is a comparison between three countries – Canada, U.S. and China • There is a significant difference in the use of fresh water between these three countries • We are most interested in Canada – 64% of the fresh water is used for power plant cooling, 15% in industry, 12% in public and 9% in agriculture • If you look at the graph of the U.S. much more water is used in the agricultural sector (41%) • United States uses much more water for irrigation in agriculture; China uses even much more (61%) • More specifically how do we use water in households? Too much water is used for conventional use – flushing toilet (30%), showering (35%), laundry (20%), drinking 10% and cleaning (5%) Hydrological poverty • Canada has plentiful water available but what about the people in some areas of the world • People in many developing countries just don’t have enough water for basic things such as drinking or cooking • One out of six people do not have regular access to clean water (safe water to drink) • In many areas such as North Africa and Western Asia people travel far distances to just get a couple of litres of water (they spend half of the day doing it) • They need to do it just to survive (often use polluted water because that is all they can find) • As a result of this diarrheal deaths is very common in developing countries • It is the number one cause of death in children younger than five years old • The biggest risk – 2 million kids die every year due to diarrheal death • Adults are also under high risk but definitely children are at a huge risk Water and Your health • We are in desperate need for help – drinking water and swimming water Drinking Water • It is our right to know what it is that we drink – what other chemicals that we have in a glass of water that we consume today • Our municipals must provide us with record – they are checking our tap water everyday • Provide us with annual reports on local drinking water quality • On water bottles it says naturally pure water – water cannot be 100% pure because water naturally has to have some minerals (no such thing as pure water • We need calcium, potassium, magnesium, sodium and salts • Distillate water is water without salts – our body needs salts • Our tap water comes from Lake Ontario, an example of surface water • Surface water – in urban areas mostly from rivers, lakes and reservoirs • Ground water can also be used for water supply – wells are very common in rural areas • Ground water reservoirs can be very small or extremely huge • There is one ground water reservoir in the U.S. thousands of metres deep underground that runs in 6 states • If we withdraw all this water more than can be naturally replenished that water reservoir will shrink and it will not last forever How is drinking water treated? • What do the municipalities do after they take water from rivers, lakes and reservoirs? • They need to clean it, it is not for drinking • First they leave water in tanks to settle down – it is easier later to purify • Then they add coagulants agents (some specially designed chemicals) for this purpose • The chemicals make clumps that settle down the smaller particles – it is easy to remove them from the water in that way • Water then goes through mechanical filtering and some types of chemical filtering • There are different types of filters to filter bacteria, viruses and protozoa (some microbes that are possibly found in water) • Filters are very good for filtering bacteria but not very good for filtering viruses • There is such a tiny and very small special techniques that need to be used for this types of germs • Water then goes for disinfection (addition of chemicals) • Question 2 on your assignment is about addition of chlorine (one type of disinfectant that can be added to water) • More new and advanced techniques are now often implemented and slowly replace convention disinfection • One is granulated activated charcoal – chemical cleaning mostly of organic contaminants • Ion exchange resins – better with heavy metals (mercury, lead) • Reverse osmosis – is a good technique for metals and inorganic contamination • Ground water is cleaner with less concentration of toxic chemicals • This is because it is naturally filtered – soil (consists of different types of chemicals) is working as a natural filter • Water particulating through the soil reacting from different chemicals purify in that way • Thus groundwater often does not need any treatment – it is pure and clean enough already • Groundwater particulating through the soil can dissolve some minerals • That is how you can get mineral water or alga mineral water depends on the percentage of each mineral • Some people cannot consume mineral water because of their health (because of the rich minerals) or can be used as a mineral supplement Chlorination of Drinking Water; Its Benefits and Risks (Assignment 1) • The most common disinfectants used for as infection of the water are chlorine, chloramines and hypochlorite – all about chlorination, could be different chemicals not just one • Chlorine reacts with organic matter in water – you always have organic matter because of plants, algae, wood debris, anything you can find in water • Some byproducts (DBP) are formed in that process and some of them are so complicated – these chemicals have an adverse affect on health • Recent research says that they have adverse affects but the data is not yet completely clear – we do not have results done on humans mostly on research animals • What are the health problems? These chemicals are cancerous and they can cause spontaneous abortion in pregnant women • Benefits are the killing of all germs which disinfects the water and safe to drink Contaminants in Drinking Water • Do you know what EPA means? U.S. Environmental Protection Agency • If you see CEPA that is the Canadian Environmental Protection Agency • This agency does a lot of work regarding different issues –setting standards for soil, water based on their research •
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