FT_Pset02_2008 - Ce feta WWW? Wee-t" 9t, r»- 17. A...

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Unformatted text preview: Ce feta WWW? Wee-t" 9t, r»- 17. A printed circuit board manufacturing plant is discharging the chemical 1,1,1—trichloroethane (TCA) into a river that subsequently flows into a lake, the source of drinking water for a small town. The levels of TCA in this lake currently fail to meet drinking water objectives of 10 ppb. As an environmental specialist with the state department of environmental pro- tection, you have been asked to help determine discharge requirements for the manufacturing plant. By assuming that the lake is a well~mixed system, that concentrations are at steady state, and that the only processes acting on this chemical in the lake are volatilization and biodegradation, how high can the influent concentration of TCA (Cm) be at the point where the river enters the lake? Some pertinent data are TCA (ignore effect of concentration on these rates) Volatilization rate 3 X 104' ,ug/crn2 - sec Biodegradation rate 6 X 10“3 ,uM/day River inflow to lake 200 gal/min River outflow from lake 200 gal/min Lake volume 1.5 X 106 gal Average lake depth 10ft @ fig" 1. On. August 1.0, 1992, at 1535, a pulse injection of food-grade table salt (sodium chloride, NaCl) was made at a point on an experimental stream in the Bickford watershed (see Fig. 2-2) in central Massachusetts. The molarity of chloride as a functicm of time was measured at “site 1” 20 m downstream. a. Estimate the average stream velocity in this reach. 1:). Estimate a dispersion coeificient for {his reach {assume the cloud is “frozen” as it passes site 1). Is the time verses ceneentration curve expected to be exactly Gaussian in this experiment? ;; Bickferd slug test #2. 920810 Ms) A O O O a h .. E w 98 “a: g; 2000 .32.: 1000 it: g U ;' W: is 0 500 1000 1500 2000 2500 M J “t EQLQI pttiolfigaéfiwéfifi. Seconds (0=15:35) @ flaw 2. 1Figure 25? shows the dissolved oxyen and temperature profiles in Upper i Mystic Lake on the Aberjona Watershed. in eastern Massachusetts on '_ September 30, 1991. a. Estimate the minimum possible flux density of downward Fickian I oxygen transport through the thermocline at a depth of approximately 7.5 m. ‘ I b. How could the actual flux density be greater than this estimate, assum— ing the gradient data are accurate? C. If oxygen is being transported downward, why is there essentially no ‘ oxygen in the hypolimnion? S fin Summer P 9 Stratification " ( 3 DO ATemp) Temperature (°C) Tempero’rure (°C) 0? 6‘ 12 1'8 24 00 5 1? :18 I. 24 5 $0 ._ , 15 20 _ 25 r 02468101214 024-8810 Dissolved Oxygen (mg/l) Dissolved Oxygen (mg/i) Epliimnion Yharmociine glimmer: well mixed stratified FIGURE 2“? Measured temperature and oxygen profiles from the Upper Mystic Lake in eastern Massachusetts, on April 1, 1991 and September 30, 1991. (Left) the lake is unstratified and well mixed, during turnover, which occurs in spring and fall. (Right) during summer, this eutrophic (productive) lake becomes depleted in oxygen in the lower layer of water (the hypolimnion), while its upper layer (epilimnion) remains well mixed by the wind and oxygenated by photosyn- thesis and by contact with the atmosphere. An oligotrophic (unproductive) lake may retain its high springtime concentration of oxygen in the hypolimnion throughout the summer [data from Aurilio (1992)]. @l ...
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This note was uploaded on 11/21/2009 for the course CEE 432 taught by Professor Ahmed during the Spring '09 term at Rowan.

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FT_Pset02_2008 - Ce feta WWW? Wee-t" 9t, r»- 17. A...

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