Lecture One Introduction to Environmental Engineering Roots of environmental engineering are from sanitation and public health John Snow s Theory cholera infected baby diaper was being washed upstream of the broad street well This is the first proof the water is a vehicle for disease MIT first college for joint education in engineering chemistry and biology Silent Spring credited with launching the environmental awareness movement Relationship Public Health waste Environmental Health resources back to public health Environmental Engineering application of science and technology to protect human health from effects of environment protect human health from human activities protect environmental health from human activities Human population is growing exponentially and the amount of resources needed to sustain life exceeds what is available on earth Grand Challenges for Engineering making solar energy economical obtaining energy through nuclear fusion carbon sequestration restoring urban infrastructure access to clean water secure cyberspace 1 3 of earths population is in water stressed regions Aging water and wastewater infrastructure water main breaks Emerging contaminants High Energy Consumption wasting Trace contaminants in water cycle surface water and drinking water wastewater back to surface and drinking water Superfund Sites highly contaminated and abandoned sites Love Canal hooker chemical buried toxic waste then neighborhood was built kids born in area had birth defects Hydrofacking injection of high pressure water chemicals gases down into earth and then horizontally drilled which causes rock layers to crack and release natural gas up the well Desalination necessary for much of our water access Lecture Two Risk Assessment and Chemistry Review Enviromental risks deal with incremental risks Risk Assessment 1 Hazard Identification gather site specific data preliminary assessment of potential human and ecosystem exposure identify possible contaminants contaminant concentrations site characteristics 2a Dose Response Assessment Carcinogens versus non carcinogens causes cancer versus doesn t cause cancer 2b Exposure Assessment Direct and indirect exposure of contaminants drainage and runoff bioaccumulation leaching ingestion inhalation 3 Risk Characterization using data to determine likelihood of humans experiencing forms of toxicity Aspects including socioeconomic political and economic pressures and concerns 4 Risk Management balancing human and environmental health risks with costs of control Chemistry Concept Review Stoichiometry balancing chemical reactions to determine and predict mass of products and reactants and equilibrium states Equilibrium reaction is not favored to left or right side at that moment k C c D d A a B b x mol L Solubility Acid Base reactions Solubility of gases in water oxygen and CO2 involves Henrys Law C K P BOD levels need to be monitored for organisms in water biological oxygen demand Kinetics how fast a reaction occurs Regulations on Environmental Health Safe Drinking Water Act Clean Water Act Clean Air Act Resource Conservation and Recovery Act Lecture Three Mass and Energy Balance Conservation of matter materials and mass balances is used to show that matter is not created or destroyed Water Mass Balance hydrologic budgeting amount water extracted from aquifers is usually much higher than the amount going in irrigation percolation or recharge Density mass volume Concentration grams liter flow rate mass per time ACCUMULATED RATE IN RATE OUT PRODUCED CONSUMED Black Box 1 No Reaction and no accumulation influents going in effluents going out must be equal this means its at steady state 2 No Reaction with Accumulation mass flow rate in not equal to mass flow rate out unsteady state 3 Reaction with No Accumulation fluid flow is at steady state but mass flow has a produced consumed Energy Conservation energy is not created or destroyed but can be changed into unusable energy Efficiency useful energy out energy in Nonrenewable energy sources coal natural gas oil nuclear Renewable hydropower solar waste biomass wind geotherm Lecture Four Reactions Reaction Rate how fast a reaction is happening determined by how fast concentrations are changing Homogeneous solution reaction takes place in a single phase but heterogeneous solutions reaction takes place at surfaces b w phases Zero Order Reactions reaction rate does not depend on concentrations of reactants k mass or mol volume x time First Order Reactions reaction rate is dependent on concentration of one of the reactants k inverse time Second Order Reactions reaction rate is depending on concentration of the reactants k inverse concentration inv Time Linear Plots 0th order time versus concentration 1st order time vs ln concentration 2nd order time vs 1 concentration Lecture Five Reactors Completely mixed system every drop of fluid is homogeneous with all other drops Batch Reactors material added to tank stirring causes reaction to occur then reactor is drained Plug flow reactor fluid flows through reactor is sequence no lateral mixing composition concentrations vary throughout length of reactor Continuous Flow Stirred Tank Reactor Completely Mixed Flow Reactors materials flow into tank mixed then flow out continuously Composition of effluent is the same concentration as everywhere in the tank if influent is consistent then effluent is consistent Hydraulic retention time time that any fluid will remain in a reactor t V Q Ideal reactor all fluid particles have same retention time Batch Reactors inexpensive easy to operate especially with small volumes of wastewater Conservative substance concentration is linear conservative implies that nothing is produced or consumed Non conservative substance concentration is exponential doesn t follow any pattern Plug Flow Reactors pipes and long narrow rivers Conservative substance addition will lead to step increase in concentration Pulse of conservative substance will flow through and flow out of the reactor Ln concentration will be linear Completely Mixed Flow Reactors best for flow rates too large for batch reactors Step increase of conservative substance in influent will lead to gradual square root type increase of effluent conc 1 concentration will be linear Lecture Six Water Cycle Litosphere land transpiration Atmosphere air precipitation Hydrosphere water infiltration back to lithosphere Opposite atmosphere precipitation lithosphere surface runoff hydrosphere