Eutrophication Final
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Transcript of Eutrophication Final
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INTRODUCTION The word eutrophic comes from the Greek word eutrophos
meaning well-fed.
Eutrophication is the process of excessive nutrient enrichment ofwaters that typically results in problems associated withmacrophyte , algal or cyano bacterial(blue-greenalgae),Nodularia spumigena growth.
Natural eutrophication is the process by which lakesgradually age and become more productive due toenrichment with nutrients (Nitrogen and Phosphorus). Itnormally takes thousands of years to progress. However,humans, through their various cultural activities, havegreatly accelerated this process in thousands of lakes aroundthe globe.
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NATURAL EUTROPHICATION Lakes originate as oligotrophic having limited
quantities of nutrients depending upon their modeof formation and composition of originalsediments.
At this stage lakes have only autochonousnutrients which recycle in the absence of anyoutside supply. All the biological production is
completely decomposed after death.
As the nutrients from outside start coming in, theprocess of eutrophication sets in.
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The buildup of nutrients through this slow mode of entrygradually starts increasing the growth of algae.[9]
When algae die and decompose, locked nutrients aremade available to the algal growth.
During each cycle, nutrients are progressively increased
in the water body.
With advancement of eutrophication, production-decomposition equilibrium is lost and an ever increasingorganic matter is introduced in the lakes which ultimately
gets deposited at the bottom.
Slowly, the thickness of the bottom sediments increaseswith time, leading to the formation of marshes and finallyextinction of the water body in the long run.
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ACCELERATED
EUTROPHICATION
The process of eutrophication is greatlyaugmented by increased supply of nutrientsthrough various human activities.
This triggers the algal growth at a much fasterrate, thus, increasing the speed of eutrophication,which otherwise would have been a slow naturalphenomenon.
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ACCELERATED
EUTROPHICATION
The process of eutrophication is greatlyaugmented by increased supply of nutrientsthrough various human activities.
This triggers the algal growth at a much fasterrate, thus, increasing the speed of eutrophication,which otherwise would have been a slow naturalphenomenon.
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Based on the levels of nutrient supplied to it , alake is classified according to the trophic state
Oligotrophic
low in nutrients. Mesotrophic intermediate nutrients.
Eutrophic high in nutrients.
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Sources of Eutrophication
POINT SOURCES: In point sources nutrient wastetravels directly from source to water. Eg.Factories having waste discharge pipes leadingdirectly to a water body can be classified as apoint source. Point sources are relatively easy toregulate. They include:
1. Wastewater effluent (municipal and industrial)
2. Runoff from waste disposal system
3. Runoff and infiltration from animal feedlots
4. Runoff from mines, oil fields, unseweredindustrial site
5. Overflows of storm and sanitary sewers [10]6. Runoff from construction sites
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NON- POINT SOURCES: these are ill-defined
and diffuse. Thsy are difficult to regulate and varyspatially and temporally (with season,
precipatation and other irregular events). Theseinclude:
Runoff from agriculture and irrigation
Runoff from pasture and range
Septic tank leachate
Runoff from construction sites< 20,000 sq. mt.
Runoff from abandoned mines
Atmospheric deposition over a water surface
Other land activities generating contaminants.
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FACTORS AFFECTING
EUTROPHICATION
Land usage : Human alterations & disturbance
Differences in land use patterns
Higher nutrients load correlated with
increased urban & agricultural land
usage Efficiency of chemical cycling &
hydrologic processes
In urban streams: impervious surfaces
decreased contact time between the
runoff water & the soil Factor affecting nutrient & sediment
loads: land form, land use intensity,
material usage
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Geology & physiography of the catchmentarea:[4,7]
nutrient supplied to a water body is inversely proportionalto the volume of the lake
composition of the underlying rock
structure & the type of soil
nutrients input is greater in watersheds with steeper slope
Factors related to water bodies characteristics of the water body modify the effect of
causative factors
affect the productivity indirectly:- distribution, availability& utilization of the nutrient inputs
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Climate Annual energy & water input
Hydrology of the catchment area
Flushing rate of the water body
Length of growing season
Direction & velocity of the wind
Quantity of precipitation
The type & patterns of climate
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Problems caused by
eutrophication
Species diversity decreases and the dominant biota changes Plant and animal biomass increase Turbidity increases Rate of sedimentation increases, shortening the lifespan of the
lake.
Anoxic conditions may develop Increased vegetation may impede water flow and navigation Treatment of drinking water may be difficult and supply can have
an unacceptable taste or odour
Decrease in water transparency
Disssolved oxygen depletion [1] Fish kills
Decrease in perceived aesthetic value of water body
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CONTROL OF
EUTROPHICATION Removing nutrients like nitrogen and
phosphorous before discharging the sewage intowater bodies i.e. better wastewatertreatment.[8,9]
Elimination of phosphate from detergents toreduce the contribution of phosphorous indomestic wastewater being discharged into waterbodies. [2]
Effective disposal of organic matter as sludge andremoval of the algal blooms by dredging.[3]
Applying solutions of chemicals like coppersulphate (an algicide) and chlorine on the surfaceof the water bodies susceptible to
eutrophication.[5]
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References1.Miguez M.G., Mascarenhas F. (2009),Eutrophication of fresh water and
marine ecosystems, ASCE, volume 135, pp. 100-109
2. Wurbs R.A. (2002), A flushing system to clean up coastal lagoons, ASCE,volume 7, pp. 35-423. Siviglia A., Stocchino A., Colombini M. (2009), Aerating circulation, ASCE4. Yeh C.H., Labadie J.W. (1997), Prediction of nutrient concentration in urbanstorm water, ASCE, volume123, pp.336-3435. Arega F., Lee J.H.W, Tang H (2008), Retention of sediments and nutrientloads with peak runoff control, ASCE, volume 134, pp.23-336. Guo Y. (2001), Nutrient loading estimates for lakes, ASCE, volume 6, pp472-4797. Ponce V.M., Osmolski Z, Smutzer D. (1985), Life-cycle assessment oftitanium dioxide coatings, ASCE, volume 113, pp. 1467-14718. Horn D.R. (1987), Phosphorous removal from lake water by combineddosage of ferrous iron and diatomite, ASCE, volume 113, pp.283-2929. Slutzman J.E., Smith J.A. (2006),Sedimantary phosphorous and arsenicinactivation in alum treated lake, ASCE, volume 11, pp432-44110. Islam M.M., Sado K.(1997), Sediment oxygen demand and nutrient fluxesfor tropical reservoir in Singapore, volume 7, pp 346-355
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