CEE 330 Homework 4 Problem 1 The boiling temperatures of chloroform an anesthetic carbon tetrachloride commonly used in the past for dry cleaning and tetrachloroethylene previously used as a degreasing agent are 61 7 C 76 5 C and 121 C The vapor pressure of a chemical is directly proportional to the inverse of the chemical s boiling point If a large quantity of these compounds were spilled in the environment which compound would you predict to have higher concentrations in the air above the site Explain your answer Solution Since the vapor pressure of a chemical is directly proportional to the inverse of the chemical s boiling point chloroform will have the higher gaseous concentration because it has the lowest boiling point and higher vapor pressure Problem 2 The dimensionless Henry s law constant air water for trichloroethylene TCE at 25 C is 0 4 A sealed glass vial is prepared that has an air volume of 4 mL overlying an aqueous volume of 36 mL TCE is added to the aqueous phase so that initially it has an aqueous phase concentration of 100 ppb After the system equilibrates what will be the concentration in units of g L of TCE in the aqueous phase Solution Set up a mass balance on the glass vial assume no chemical or biological loss Then solve for the TCE equilibrium concentration in the aqueous phase using the dimensionless Henry s constant to substitute for the concentration of TCE in the air phase M total M H 2O M AIR 100 g 1L L L 36 mL Ceq H 2O 36 mL Ceq AIR 4 mL 1L 1000 mL 1000 mL 1000 mL Ceq AIR K H 0 4 Ceq H 2O Substituted Ceq AIR Ceq H2O 0 4 and then solve for Ceq H2O 3 6 g Ceq H2O 0 036 L 0 0016 L Ceq H2O 96 g L Problem 3 Atrazine is an herbicide widely used for corn and is a common groundwater pollutant in the corn producing regions of the United States Use EPIWIN to find Koc for atrazine Calculate the fraction of total atrazine that will be adsorbed to the soil given that the soil has an organic carbon content of 2 5 The bulk density of the soil is 1 25 g cm 3 this means that each cubic centimeter of soil soil plus water contains 1 25 g of soil particles The porosity of the soil is 0 4 Solution Assume a total of 1 cm3 of soil with 0 6cm3 soil and 0 4cm3 of void space to be filled with water Mass of soil particles in 1 cm3 of soil water 0 75g 1 Mass balance of atrazine in bulk soil i e soil pore water g g Total atrazine C w M soil gsoil Vw mL Csoil mL gsoil g mL gOC g Csoil K OC f oc Cw gsoil gOC gsoil mL mL L Note K OC K OC gOC kgOC Total atrazine C w 0 4 K OC f oc C w 0 75 Csoil M soil K OC f oc C w M soil 0 75 K OC f oc Total atrazine C w 0 4 K OC f oc C w 0 75 0 4 K OC f oc 0 75 102 25 0 025 0 75 0 89 0 4 102 25 0 025 0 75 Problem 4 The log Henry constant units of L atm mole and measured at 25 C for trichloroethylene TCE is 1 03 for tetrachloroethylene PCE it is 1 44 for 1 2 dimethylbenzene it is 0 71 and for parathion it is 3 42 a What are the dimensionless Henry s law constants for each of these chemicals b Rank the chemicals in order of ease of stripping from water to air Solution Note that in this problem the Henry s constants are reported as log Henry s constant a LH 2O Pair L atm KH RT H Cwater mole Lair L atm KH L mole H H 2O RT Lair 101 03 L atm mole H trichlor 0 44 0 08205 L atm mole K 298K H tetrachlor 101 44 L atm mole 1 1 0 08205 L atm mole K 298K H dim ethyl 100 71 L atm mole 0 21 0 08205 L atm mole K 298K 10 3 42 L atm mole 1 6 10 5 0 08205 L atm mole K 298K Note that this Henry s constants given in this problem have concentration of chemical in air over concentration of chemical in water Pair Cwater In this unit high Henry s constants means the chemicals prefer to go from water to air H parathion 2 b easiest to hardest tetrachloroethene trichloroethene 1 2 dimethylbenzene parathion Problem 5 Benzene in the wastewater from a manufacturing facility is sent at rate of 2000 kg day to a public wastewater treatment plant where 85 of the organic contaminant is removed before discharging to a local river One hundred km downriver of the discharge point is the intake to a public drinking water treatment plant The river flow rate is 1250 million liter per day River velocity is 0 5 m sec River width is 50 m Sediment concentration in suspended solids 1500ppm with fraction of sediment organic carbon foc is 0 01 Biota concentration is 100g per 100 cubic meter Use EPIWIN to get property data Include summary from EPIWIN and structure of the compound in your report When several values are reported for a given property use the experimental data a Estimate the fraction of benzene in water sediment and biota at the discharge point b Determine whether volatilization of benzene from the river is likely to be significant c Ignore evaporation and compare the concentration of benzne in the influent of drinking water treatment with the MCL set by EPA d Estimate the potential toxicity of the released benzene to aquatic life Solution The MCL set by EPA for benzene is 5 ppb Benzenedischarged to POTW 2000 kg day Benzenedischarged to a local water 2000 1 85 300 kg day a From EPI the property data is the following 3 Water Solubility Exp 1790 mg L 25o C Henry s Law constant 5 55 10 3 atm m3 mole K oc 165 5 L water kg sediment carbon Log BCF 1 072 BCF 11 8 L water kg biota Based on the river flow rate the flow rates of water sediment and biota are Water 1250 106 liter day 1 kg liter 1250 106 kg day Sediment 1250 106 kg day 1500 10 6 kg sediment kg water 0 01 kg sediment C kg day 1500 10 6 kg sediment kg water 18750 kg sediment C day Biota 1250 106 kg day 10 6 kg biota kg water 1250 kg biota day Mass Balance of Benzene in the river Benzene rate of loading Qwater Cw Qsed Csed Qbiota Cbiota Qwater Cw Qsed Cw K oc Qbiota Cw BCF Cw Qwate Qsed K oc Qbiota BCF Benzene rate of loading 300 kg Benzene day Qwater 1250 106 kg water day Qsed K oc 18750 kg sediment C day …