Project on Surface Water

8/8/2019 Project on Surface Water

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INTRODUCTION

Contaminated surface water generally is associated with human-related activities such as illegaldumping of chemicals, over-application of agricultural chemicals, and improperly constructed or

maintained septic systems. Yet natural chemicals, elements, or particles from the land and in the

subsurface can affect the quality of fresh water, including its potability (drinkability).

A contaminant may or may not be harmful to human health or the environment. Water that is

safe to drink contains no contaminants at levels that may be harmful to health; however, it maystill contain constituents classified as contaminants. "Pure" water does not occur in nature.

In some areas, contamination from natural and human sources has affected the use of these

waters. For example, naturally occurring minerals within bedrock can impair the taste of

groundwater and in some cases limit its use. The spilling, leaking, improper disposal, or

intentional application of chemicals at the land surface can result in runoff that contaminates

nearby streams and lakes, or infiltration that contaminates underlying aquifers

The type and severity of water contamination often is directly related to human activity, which

can be quantified in terms of the intensity and type of land use in the source areas of water tostreams and aquifers. The analysis of patterns of land use and population provides a tool in the

investigation of sites with known contamination, and in the prediction and prevention of futurecontamination of downstream waters. Studies of contamination sources and transport pathways

that affect surface water and groundwater draw upon several disciplines, including hydrology ,geology, biology, soil science, agriculture, physics, chemistry, and engineering.



Surface-Water Contamination and Land Use

A variety of natural and human factors can affect the quality and use of streams, lakes, andrivers, known as surface water. One of the most important factors that can affect the quality of a

surface-water body is the land use within its watershed. A number of studies have shown that the

density of population and housing can affect the concentration of chloride, nitrate, and a varietyof pesticides in streams that drain urban and suburban settings. For example, studies of the water

supplies that serve DHAKA CITY have shown that the lowest chloride and nitrate

concentrations occur in water from areas dominated by forested land, whereas elevated chloride

and nutrient concentrations occur in areas with high densities of housing with septic systems.Chloride concentrations in streams also were linked to the wintertime application of road salt in

the populated a reas.

CAUSES OF SURFACE WATER POLLUTION

Factors that can affect the movement of contaminants from source areas to wells are:

y The chemical nature of the contaminant;

y The physical properties of the soil and aquifer material;y The amount and timing of recharge; and

y The direction and velocity of groundwater movement.

Despite the complexity of contaminant hydrology, the effects of certain land uses ongroundwater quality have been scientifically documented in many areas. For example,relationships have been found between land use and five common groundwater contaminants: n

itrogen, bacteria, road salt, pesticides , and volatile organic compounds .

Hardness.

Elevated concentrations of calcium (Ca) and magnesium (Mg) are derived from rocks andsediments in the subsurface. Limestone is made largely of calcium and magnesium and, as a

result, groundwater that has been in contact with limestone will tend to have high hardness.Calcium and magnesium are common elements, however, and are contained in significant

amounts in many rocks and sediments. If the water is in contact with these geologic materialslong enough, and if the water is slightly acidic or corrosive, the water will contain elevated

concentrations of calcium and magnesium, among other constituents.



Nitrate.

Nitrate (a form of nitrogen) is essential for plant growth, but an overabundance can contaminate

streams and groundwater. In high concentrations it causes methemoglobinemia in infants.

Bacteria.

Human sewage and manure from cattle, hogs, chickens, geese, and other animals contain

bacteria and other pathogens that can cause human illness. Many outbreaks have resulted from



wells contaminated by fecal waste. Land-use data on densities of septic tanks and animalstherefore are useful indicators of the presence of bacteria in wells.

Road Salt.

Storm runoff and snowmelt in areas with salt-treated roads can carry sodium and calciumchlorides into the groundwater. Data on road density, salt application rate, and locations of salt

storage piles can provide useful indicators for detection of elevated chloride concentrations inwells. . In unsewered residential areas, the rate of sewage discharge from domestic septic tanks

can be estimated from population and housing density.

Caused by the excess nutrient andsediments (sequence of event outlined inprior slides).

Major cause is the use of fertilizers,excess erosion from farmland or nutrientrich soils

(deforestation), and disposal ofphosphate bearing compounds (manydetergents) through

sewer systems.

Pesticides.

Pesticides are used to kill unwanted pests, such as termites, ants, and rodents around homes;

nematodes in soil; and fungi and insects in crops. Similarly, herbicides kill undesirable weeds



and grasses in lawns, along roads, and in agricultural areas.

The agency defines water as "safe" if it contains no harmful bacteria or other pathogenic(disease-causing) microorganisms, and the concentrations of individually regulated toxic

chemicals are below drinking-water standards.

Color.

Perhaps the most common cause of coloration in groundwater is the occurrence of iron (Fe) or

manganese (Mn) in the water. Red and brown colors are due to iron; black to manganese or organic matter; and yellow to dissolved organic matter such as tannins

Taste.

In addition to causing color, dissolved iron and manganese in groundwater and surface water

may also impart a metallic taste to the water, even at low concentrations

Odor.

The most common unpleasant odor associated with some groundwater is that resembling thesmell of rotten eggs, produced by the presence of low levels of hydrogen sulfide (H 2 S) gas. This

gas occurs when sulfate (SO 4 ) dissolved in water is transformed to H 2 S by bacteria in the

presence of organic matter.

Volatile Organic Compounds.

Volatile organic compounds (VOCs) have affected groundwater locally throughout the United

States. Many VOCs are carcinogenic ; thus, their presence in groundwater creates a serious problem for water suppliers.



Pollution Sources and Contaminant Pathways.

Soil erosion and water runoff from cropland into nearby streams can be a major source of

sediment, nutrients, and pesticides in watersheds dominated by agricultural land Implementationof soil and water conservation measures, such as buffer strips of undisturbed land between

cropland and adjacent streams, can provide an effective control that reduces contaminant entryinto aquatic systems.

Sediment.

Sediment is eroded and transported mostly during heavy rainfall events and the associated high

streamflows, particularly floods. Sediment can become a problem because its deposition instreams and lakes can ruin the habitat for aquatic plants and animals; it also can fill stream

channels, lakes, and harbors, which then require costly dredging. Studies have shown that theamount of suspended Sediment sources typically are lacking in developed areas,

Wastewater Discharges.

Discharge of wastewater from municipal sewage treatment plants, industrial and commercial

sources, Depleted oxygen levels, combined with elevated concentrations of ammonium that aretypically found in the treated wastewater, can be toxic to benthic (bottomdwelling) fauna and

fish. Municipal wastewaters also contain significant amounts of phosphorus and nitrogen, whichcan cause eutrophication of lakes anestuaries



Emerging Contaminants

The environmental occurrence of recently studied "emerging contaminants" includes human and

veterinary pharmaceuticals, industrial and household ZDVWHZDWHU products (such ascaffeine, detergent byproducts, and insect repellants), and reproductive and steroidal hormones.Reconnaissance studies on a national scale have shown that many organic wastewater

contaminants can persist in waterbodies far downgradient of their discharge points,

How We The Surface Water



Sedimentation: The flocculated particles then settle naturally out of the water.

Filtration:Many water treatment facilities use filtration to remove all particles from the water. Those

particles include clays and silts, natural organic matter, precip-itates from other treatment processesin the

facility, iron and manganese, and microorganisms. Filtration clarifies the water and enhances theeffectiveness of disinfection.

Coagulation (Flocculation & Sedimentation): Flocculation: This step

removes dirt and other par-ticles suspended in the water. Alum and iron salts or synthetic organic

polymers are added to the water to form tiny sticky particles called ³floc,´ which attract the dirt particles.



Disinfection:

Disinfection of drinking water is considered to be one of the major public health advances of the

20th century. Water is often disinfected before it enters thedistribution system to ensure thatdangerous micro-bial contaminants are killed. Chlorine, chlorinates, or chlorine dioxides are

most often used because they are very effective disinfectants, and residual concen-trations can be

maintained in the water system.



CONCLUSION

The total amount of water available on earth has been estimated at 1.4 billion cubic

kilometers, enough to cover the planet with a layer of about 3-km deep. About 95% of the

earth¶s water is in the oceans, which is unfit for human consumption and other use because

of its high salt content; about 4% is locked in the polar ice caps; and the remaining 1%

constitutes all the fresh water in hydrological .

Only 0.1% is available in water in rivers, lakes, and streams, which is suitable for

human consumption. This highlights the significance of the need to preserve our fresh water

resources. The annual precipitation of rainfall over BANGLADESH is 400 million-hectare

meters. The surface water resources carry 17,68,000 million cubic meters out of which only

50% can be put to beneficial uses. In addition, the surface water potential of 4,22,900

million cubic meters is available .

BANGLADESHI river basins cover 83% of the total drainage basin and contribute

to 85% of the total surface flow whereas medium and minor river basins share 8% and8% respectively of the total surface flow. which is affected by pollutants from various

sources such as domestic waste discharges, industrial waste disposal, and other human

activities like bathing, washing and swimming etc. The U NICEF & WWF study sources

affecting water quality of both surface and ground water. The projected demands for the annu

increase by the year 2025 to that in the year 2000 .

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Project on Surface Water