Lecture 1 - Water Pollution (LECTURE)

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Transcript of Lecture 1 - Water Pollution (LECTURE)

Water Resources


Two types of water subject to pollution Surface water rivers, lakes, oceans Uses: drinking, recreational [fishing, boating, swimming], irrigation.

Groundwater- occurs beneath a water table in soils or rocks; subject to pollution from toxic chemicals. Uses: drinking, irrigation, etc

Water Resources

Water resources are sources of water that are useful or potentially useful to humans. It is important because it is needed for life to exist.

Sources Of Fresh Water Surface Water Sub-Surface Water Desalination Frozen Water Ground Water

Surface Water Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, and sub-surface seepage.

Sub-Surface Water Sub-Surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between sub-surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").

- is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become fully saturated with water is called the water table.

Desalination Desalination is an artificial process by which saline water (generally ocean water) is converted to fresh water. The most common desalination processes are distillation and reverse osmosis. Desalination is currently very expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination.

Frozen Water Several schemes have been proposed to make use of icebergs as a water source, however to date this has only been done for novelty purposes. Glacier runoff is considered to be surface water.

Uses Of Fresh Water Uses of fresh water can be categorized as consumptive and non-consumptive (sometimes called "renewable"). A use of water is consumptive if that water is not immediately available for another use. Losses to sub-surface seepage and evaporation are considered consumptive, as is water incorporated into a product (such as farm produce). Water that can be treated and returned as surface water, such as sewage, is generally considered non-consumptive if that water can be put to additional use.

Uses Of Fresh Water Agricultural Industrial Household Recreational Environmental Activities

Agricultural It is estimated that 69% of world-wide water use is for irrigation. In some areas of the world irrigation is necessary to grow any crop at all. Irrigation methods such as overhead sprinkler irrigation are usually less expensive but also less efficient, because much of the water evaporates or runs off. More efficient irrigation methods include drip or trickle irrigation, surge irrigation, and some types of sprinkler systems where the sprinklers are operated near ground level. These types of systems, while more expensive, can minimize runoff and evaporation. Any system that is improperly managed can be wasteful.

Agricultural Aquaculture is a small but growing agricultural use of water. Freshwater commercial fisheries may also be considered as agricultural uses of water, but have generally been assigned a lower priority than irrigation.

Industrial It is estimated that 15% of world-wide water use is industrial. Major industrial users include power plants, which use water for cooling or as a power source (i.e. hydroelectric plants), ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent. The portion of industrial water usage that is consumptive varies widely, but as a whole is lower than agricultural use.

Household It is estimated that 15% of world-wide water use is for household purposes. These include drinking water, bathing, cooking, sanitation, and gardening. Most household water is treated and returned to surface water systems, with the exception of water used for landscapes. Household water use is therefore less consumptive than agricultural or industrial uses.

Recreational Recreational water use is usually a very small but growing percentage of total water use. Recreational water use is mostly tied to reservoirs. If a reservoir is kept fuller than it would otherwise be for recreation, then the water retained could be categorized as recreational usage. Release of water from a few reservoirs is also timed to enhance whitewater boating, which also could be considered a recreational usage. Other examples are anglers, water skiers, nature enthusiasts and swimmers.

Environmental Explicit environmental water use is also a very small but growing percentage of total water use. Environmental water usage includes artificial wetlands, artificial lakes intended to create wildlife habitat, fish ladders around dams, and water releases from reservoirs timed to help fish spawn. Like recreational usage, environmental usage is nonconsumptive but may reduce the availability of water for other users at specific times and places. For example, water release from a reservoir to help fish spawn may not be available to farms upstream.

Sources of wastewater

Municipal wastewater - includes all waste under the control of local authorities or agents acting on their behalf. Schools Street litter Civic amenity site waste Municipal parks Hotels Garden wastes Council office waste Industrial wastewater Airport glycol deicing Rendering plants Tire fire wastewater Fish culture wastewater Dairies Metal plating industries Oily bilges

Agricultural Animal wastes both liquid and solid, The piggery waste is comparable to other animal wastes except that many piggery wastes contain elevated levels of copper that can be toxic in the natural environment. Ascraid worms and their eggs are also common and can infect humans. Silage liquor Fresh or wilted grass or other crops can be made into the semi fermented product called silage which can be stored and used as winter forage for cattle and sheep. The production of silage often involves the use of a n acid conditioner such as sulfuric acid or formic acid. The process of silage making frequently produces yellow-brown strongly smelling liquid which is very rich in simple sugars, alcohol, short-chain organic acids and silage conditioner. The liquor on it own can cause structural problems in concrete pits because of the acidic nature of silage liquor. Pesticide run off and surpluses Inappropriate use of pesticides so that pesticide-containing wastewaters enter the environment can give rise to severe and long lasting ecological damage.

Milking parlor wastes Although milk has deserved reputation as an important and valuable food product, its presence in wastewaters is highly polluting because of its organic strength, which can lead to very rapid de-oxygenation of receiving waters. Milking parlor wastes also contain very large volumes of wash-down water, some animal waste together with cleaning and disinfection chemicals. Slaughtering waste wastewater from slaughtering activities is similar to milking parlor waste although considerably stronger in its organic composition and therefore potentially much more polluting. Vegetable washing water washing of vegetables produces large volumes of water contaminated by soil and vegetable pieces. Low levels of pesticides used to treat the vegetables may also be present together with moderate levels of disinfectants such as chlorine. Fire water Few farms plan for fires, fires are nevertheless more common on farms than on many other industrial premises.

Characteristics of wastewater Municipal gray color, musty odor contains organic components Industrial dependent on processes that produce a water based waste water Agricultural Relates to the treatment of wastewaters produced in the course of agricultural activities.

How wastewater affects people The water we use never really goes away. In fact, there never will be any more or any less water on Earth than there is right now, which means that all of the wastewater generated by our communities each day from homes, farms, businesses, and factories eventually returns to the environment to be used again. So, when wastewater receives inadequate treatment, the overall quality of the worlds water supply suffers. Locally, the amount of wastewater homes and communities produce, its characteristics, and how it is handled can greatly impact residents quality of life. Wastewater has the potential to affect public health, the local economy, recreation, residential and business development, utility bills, taxes, and other aspects of everyday life. Because small community residents, in particular, are more likely to be directly responsible for making decisions about their wastewater, it is important that they know something about its characteristics (that is, its components, strength, volume, and flow) and how certain characteristics can affect their lives.

In the study of groundwater contamination, however, toxic chemicals are the principal pollutants of concern. The 25 most frequently detected contaminants found in groundwater at hazardous waste sites are listed in Table 5.14. Nine of these contaminants are inorganic: lead (Pb), chromium (Cr), zinc (Zn), arsenic (As), cadmium (Cd), manganese (Mn), copper (Cu), barium (Ba), and nickel (Ni).

Rank1 2 3 4 5 6 7 8 9 10

ContaminantTrichloroethylene Lead Tetrachloroethylene Benzene Toluene Chromium Methyl