A pollutant entered into a confined aquifer of 5 m thick and porosity 25%. If the seepage discharge through the aquifer is 0.25 m² / s, the travel time of pollutant for 100 m in the aquifer will be (in seconds)

3. A completely mixed pond of volume, V, has an influent steady-state flow, Q, entering with a BOD, concentration of L, and a dissolved oxygen (D.O.) concentration of C, (see the illustration below). Assume a first-order BOD decay constant, k,, and a first-order reaeration coefficient of k, as indicated: Q = 107 L/day k2 Co = 0.23 day 4 mg/L D.O. %3D V = 2 x 108 liters 0.20 day %3D C* =10 mg/L D.O. (saturation level of D.O.) Lo.6 V.C.L a) What would be the allowable maximum influent BOD, concentration (L) in order to maintain the steady-state dissolved oxygen concentration in the pond (C) above 2 mg/L D.O.? b) If the initial BOD, concentration in the pond (at time 0) is 5 mg/L what will the BOD, concentration be three days after the waste input is begun (with L equal to the amount you arrive at in part (a))?

The level of water in the reservoir is 1.25 m. If there is a rainfall of 38 cm occurring in a month, during this period evaporation as measured by the class A pan is 32 cm. What is the level of water in m at the end of the month.

. A water plant with a flow of 20,000 m³/day uses 25 mg/L alum as Al,SO, 18H₂O. The sludge produced consists of the alum precipitates plus 20 mg/L of other material removed by the process. Determine the dry mass of sludge produced per day.

The figure shows the cross section of a levee that is 500 m long and is underlain by a 2-m-thick permeable sand layer. It was observed that the quantity of water flowing through the sand layer into the collection ditch is 250 m³/day. What is the hydraulic conductivity of the sand layer? Elv. 160 m Levee 1 Elv. 150 m 2 m Ditch 125 m I Impervious O Sand

Consider the seawater exchange at the entrance of the Black Sea, which is an enclosed ocean basin in communication with the Mediterranean Sea. The salinity of the bottom layer inflow is 35. The measured volume transport of the upper layer outflow is 12 x 103 m'/s with a salinity of 17.5. The volume of the entire Black Sea has the same density. a) What is the volume transport of the bottom layer inflow to the Black Sea. b) Is the Black Sea an evaporative or precipitation basin? Justify your answer. c) The volume of the Black Sea is 0.6 x 10 km³ and does not change in time. What is the residence time of the Black Sea?

The base of a river in in contact with the top of an aquifer. A truck carrying bags of powdered cyanide is on a bridge crossing the river when a large bump causes one of the bags to fall into the river. The water in the river suddenly becomes polluted by the cyanide with a concentrations of 6.78 mg/L. The aquifer has an average linear ground water velocity of 0.256 m/day. Laboratory analyses data indicates that longitudinal dispersivity can be found through the equation: a = 0.86(log Ls)² where Ls is the length of the straight line path between two points along the path of transport. Find the longitudinal dispersion 108 m downstream from the bridge. Assume that the cyanide solute has a diffusion coefficient of 3.6 x 10 -5 m²/s and the aquifer has a coefficient related to tortuosity (o) equal to 0.8. Find the coefficient of hydrodynamic dispersion.

A canal and a stream run parallel to each other at a separation distance of 400 m. Both of them completely penetrate an unconfined aquifer (K = 3.0 m/day) located above a horizontal impervious bed. The aquifer forms the separation landmass between the two water bodies. The water surface elevations in the canal and the stream are 5.0 and 3.0. i. the uniform infiltration rate that will create a water table divide at a distance of 100 m from the canal ii. the elevation of the water table divide iii. the seepage discharge into the two water bodies iv. Plot the water table.