Problem 3: An industry is illegally discharging tetrachloroethene (also called t
ID: 1711962 • Letter: P
Question
Problem 3: An industry is illegally discharging tetrachloroethene (also called tetratchloroethylene, perchloroethylene, or PCE) into a river. The concentration in the river at the point of discharge is 0.05 mg/L. A drinking water treatment plant (DWTP) is located 10.0 km downstream. The water velocity in the river is 0.25 km/day A. What is the hydraulic residence time of the river between the discharge point and the DWTP? B. If PCE degrades with a first-order rate constant k 0.1 d-1, what is the PCE concentration at the DWTP at steady state? C. The oral potency factor for PCE is 5.1 × 10-2 (mg/kg-d)-, If a 70 kg person drinks 2 L of the water from the DWTP every day, is the lifetime cancer risk greater than 1 in one million? Assume no removal of PCE in drinking water treatment. Problem 4: An industry discharges 1,1-dichlorothene (1,1-DCE) into a small, well-mixed lake. The influent concentration into the lake is 0.75 mg/L and the hydraulic residence time of the lake is 3.5 days A. What is the concentration of 1,1-DCE in the lake (at steady state) if 1,1-DCE degrades in the lake with a first-order rate constant k = 0.15 d-19 B. A DWTP takes water from the lake. The oral RfD for 1,1-DCE is 0.009 mg/kg-d. Is the average daily dos from consuming 2 L/d of water from the DWTP greater than the RfD? Assume a 70 kg body weight and no removal in the DWTIP C. The bioconcentration factor for 1,1-DCE is 5.6 L/kg. Is the average daily dose from eating 100 g of fish per day caught from this lake greater than the RfD? Assume a 70 kg body weight. Notes: Proble: Bamboo is a large grass, not a tree. It grows by sending out rhizomes that emerge as shoots. It has a compressive strength higher than conventional concrete and tensile strength nearly as high as steel. Parameters for the logistic model were estimated by fitting the logistic model to data (data from bamboogarden.com/care) Data are: 4, 7, 14 and 60 shoots after 0, 1, 2, and 6 years, respectively. Problems 3 and 4: The degradation rate constants listed are approximate values for the volatilization rate constants (calculated from volatilization half-lives). You can treat them as first-order rate constants for the degradation of the compounds inside their respective control volumes for the purposes of these problemExplanation / Answer
4.
A . Calculate effluent concentration using the following formula.
C = Cin / (1 + kt)
Cin = 0.75 mg/L , k =0.15 d-1 , t = hydraulic residence time = 3.5 days
C = 0.75 mg/L / (1 + 0.15 x3.5) = 0.49 mg/L
Therefore concentration of 1,1-DCE is 0.49 mg/L
B. The effluent concentration of 1,1-DCE is 0.49 mg/L
Therefore Daily dose of consumption of 2L of water contains 1,1-DCE = 0.49 x 2L = 0.98 mg per day
The oral RfD for 1,1-DCE is 0.009 mg/Kg-d
Therefore oral RfD for 70 Kg body weight = (.009 mg/Kg-d) x 70 kg = 0.63 mg per day.
0.98 mg/day > 0.63 mg/day
Therefore daily dose of consuming 2L of water is greater than RfD.
C. BCF = 5.6 L/Kg of fish
Therefore BCF for 100 g of fish consumed per day = 5.6 L x (100/1000) = 0.56 L
Therefore effluent concentration of 1,1-DCE = 0.56 L x 0.49 mg/L = 0.2744 mg per day.
RfD calculated from B for 70 Kg body weight = (.009 mg/Kg-d) x 70 kg = 0.63 mg per day.
0.2744 mg < 0.63 mg
Therefore daily dose of eating 100 g of fish from this lake is less than RfD
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.