• 111/06/15 Environmental Engineering Science 1 Ch1 Overview • 1.A What Is Environmental Engineering Science? – Use of Earth’s Resource, Release Contaminants to Environment, Environmental Impact – Constituents, Impurities, Species, Contaminants, Pollutants – Instead, the central mission of environmental engineering is to develop and apply scientific knowledge through technology to minimize adverse effects that are associated with contaminants in environmental media.
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2015/9/3 Environmental Engineering Science1 Ch1 Overview 1.A What Is Environmental Engineering Science? –Use of Earth’s Resource, Release Contaminants.
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•112/04/21
Environmental Engineering Science 1
Ch1 Overview • 1.A What Is Environmental Engineering Science?
– Use of Earth’s Resource, Release Contaminants to Environment, Environmental Impact
– Instead, the central mission of environmental engineering is to develop and apply scientific knowledge through technology to minimize adverse effects that are associated with contaminants in environmental media.
• A special unit is defined for concentration of charge associated with ions in water. We refer to the ionic charge concentration associated with some species as its normality (N), measured in units of equivalents per liter (eq L-1), where one equivalent represents a net charge equal to one mole of electrons.
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Mass Fraction and Mole Fraction
% percent 1 part species per 100 part solution
‰ per mil 1 part species per 1000 part solution
ppm part per million 1 part species per 106 part solution
ppb part per billpon 1 part species per 109 part solution
ppt part per trillion 1 part species per 1012 part solution
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• Thus, 5 ppb of benzene in air means that there are 5×10-9 moles (3×1015 molecules) of benzene in a mole of air; on the other hand, 5 ppb of benzene in water means that 1g of water contains 5×10-9 g of benzene.
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1.C.2 Material Balance1.C.2 Material Balance
Material balances are applied for both conserved and nonconserved properties of matter. An example of a conserves property is chemical element.
• Conserved properties are not changed by transformation processes. Chemical reactions do not change the amount of a chemical element in a system.
• An example of a nonconserved property is a chemical compound, since reactions change the quantities of compounds.
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1.C.3 Material Balances on Flows• A wastewater stream containing a
contaminant concentration Cw flows at a volumetric rate Qw into a river. Upstream of the discharge, the contaminant concentration in the river is Cr and the volumetric flow rate of water is Qr. Assuming complete mixing of the wastewater stream in the river at the point of discharge, what is the contaminant concentration immediately downstream?
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1.C.3 Material Balances on Flows
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1.C.3 Material Balances on Flows
• SOLUTION :
Qmix=Qr+Qw
QmixCmix= QrCr + QwCw
• Therefore,
Cmix = (QrCr + QwCw )/ (Qr+Qw)• The concentration of contaminants does not
change in the fluid streams as they diverge, so the composition of each branch is the same as in the entering branch.
• Analysis is at the heart of environmental engineering science. We analyze both engineered and natural environmental systems, usually for one of two major purposes: to predict how they will behave or to explain why they behaved as they did.
• Analyses may be conducted at several levels, from simple range-finding
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1.C.4 Engineering Analysis
• Steps : 1.Translate the physical system into a
mathematical representation.
2.Solve the mathematical problem to obtain the result.
3.Interpret the significance of the result for the physical system.
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1.C.5 Control Opportunities
• In the past, the major solution to pollution is dilution.
• Human activities have reached a scale that is sufficient to cause regional and even global environmental impact. It is certainly no longer the case that dilution suffices to solve environmental quality problems.
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1.C.5 Control Opportunities
• The activity that generates the waste is the first link in this chain.
• The next opportunity occurs when waste is present
• The final opportunity occurs after the waste has been released to the environment.
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• Applying pollution control measures at the generating process is known as pollution prevention.
• Control measures applied after the waste has been generated but before it is discharged are termed end-of-the-pipe treatment processes.
• Corrective measures applied after the waste has been released are known as environmental restoration.
1.C.5 Control Opportunities
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1.C.5 Control Opportunities• In water quality engineering, environmental
control is most frequently applied at two points:– to water before it is delivered to the consumer
– to wastewater before it is released to the environment
• Air pollutants control methods focus on the effluent streams that may lead to airborne release of pollutants.
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• Most environmental engineering activities are directly or indirectly motivated by environmental regulations.
• Pollutant regulations are based on technical information concerning :– health effects and other environmental costs of