Environmental Engineering

Questions & Answers

Learning Objectives 1- Get Familiar with the operation of a continuous flow ion-exchange contactor (column) to remove the contaminant nitrate from water. 2-cTo experimentally determine two important ion exchange operating parameters: breakthrough curve and column utilization. 3- To familiarize students with common contaminants removed by ion-exchange and the issue of regenerant disposal.


LABORATORY #7 Disinfection: Chlorination of Wastewater Effluent Note: the original version of this laboratory experiment was written by the Association of Environmental Engineering Professors (Unit Operations and Unit Processes Laboratory Manual, 4th edition, 1998). In Spring 2005, Shamin Begum (graduate assistant) and Dr. Jacimaria Batista modified the laboratory to fit the coliform bacteria equipment available at UNLV. Learning objectives: 1. Students should be able to know what coliform bacteria are and why they were chosen as a measure of microbiological quality of waters. 2. Students should be able to explain the meaning of "concentration vs. time" as applied to disinfection of waters. 3. Students should be able to use an MPN table to interpret experimental data. 4. Students should be able to experimentally determine the inactivation rate constant and the coefficient of dilution.


1. Polychlorinated biphenyls (PCBs) are a widespread sediment contaminant. To sequester this contaminant, an "active cap" consisting of an adsorbent material can be used (Fig. 1). A study was published in 2006 by Murphy et al. to compare the performance of different types of cap material: sand, coke, and activated carbon. (a) Plot in Excel or another spreadsheet software the breakthrough curve for Cout(t)/Cin vs. t exiting the 1.25 cm capping layer, if there is no degradation (see next page for example spreadsheet setup). The range on the time axis for your plot should be selected to clearly observe when complete breakthrough has occurred - note the time scales may be extremely different (by several orders of magnitude) for the three different capping materials; therefore, prepare three separate plots for sand, coke, and activated carbon. Write a sentence explaining the differences in the time to breakthrough for the three materials, in terms of the advection-dispersion-adsorption parameters in Table 1. (b) Repeat part (a) if PCB has a half-life of 50 years and undergoes 1st order decay (biodegradation) in the capping layers. Plot the Cout(t)/Cin vs. t results onto the same plot that you made in part (a) for each capping material. Write a sentence explaining the trend in the final (steady-state) concentration that exits the capping layer for the three different materials when the degradation reaction is included.


2. An air pollution source emits a nonreactive pollutant at a rate of 500 g/s from a stack height of 125 m during a clear night. The plume rise is 75 m. The wind speed is 4 m/s as measured by an anemometer at 10 m height. Use Briggs urban dispersion coefficients and rough terrain. (a) Estimate ground level concentrations in µg/m³ at a distance 4000 m downwind of the source and 50 m orthogonal to the plume centerline (i.e., x = 4000 m, y = 50 m). Assume the dispersion is unbounded at both the ground and above. For this part of the problem, perform the calculations by hand (to practice for an exam scenario). (b) Set up in Excel or another spreadhseet program to compute the ground level concentrations in µg/m³ for the same scenario as part (a) at downwind distances x of [100, 200, 300, ...... 10000] m from the source. When setting up the spreadsheet, you should have columns for x, Oy, G, and C(x.y.z). (c) Compute the ground level concentrations in µg/m³ at x from 100 to 10000 m, assuming the pollutant is perfectly reflected from the ground and unbounded from above. (d) Compute the ground level concentrations in µg/m³ at x from 100 to 10000 m, assuming a fumigation scenario with an inversion height z; of 400 m. (e) Plot all scenarios (b, c, d) on the same graph. Explain the differences between the three concentrations based on the physical description of the model. Discuss which scenario would be the most hazardous.


Q4. A roof is normally exposed to the thermal environment, is composed of the following components, Tiles for roof = 20 mm. Cement mortar = 60 mm. Concrete (ballast) = 130 mm. If the required U-value for roofs is = 0.62 W/m. sq.-degree C. and the heat flow is downwards. i. Calculate the U-value of the existing roof. ii. Calculate the required thick of mineral wool, if its thermal conductivity is 0.042 W/m-C Given that the thermal conductivity of the roof tiles is 0.885 W/m-C, the cement mortar is 0.5W/m-C and the concrete slab is 1.5 W/m-C. Assume the thermal resistance of External is 0.059 m²-°C/W, the roof tiles is 0.0226 m²- °C/W, the cement mortar is 0.0400 m²-°C/W, concrete is 0.1000 m²-°C/W, internal is 0.154 m²-°C/W.


Need to write 2 page research about LEED buildings in Boston and how it helps climate change


There has been a chemical spill in a facility. The chemical has been identified to be a volatile organic solvent. The facility has a ventilation system with a constant flow rate of 12,000 [m^3/min]. And 2 [mg/m^3] of benzene has been detected in the ventilation outlet. The air inlet has zero benzene concentration and the indoor air is very well mixed. What is the generation rate of the organic solvent in the lab [kg/h]?


A well-mixed lake with a surface area of 6.0 [Km^2] and an average depth of 10 m is fed by a stream and rainfall. (Groundwater and runoff are insignificant inputs). The stream's flow rate is 1 [m^3/s], and the concentration of phosphorous in the stream is 1 [mg/l]. Average rainfall is 1 [m/yr], and the rain has a phosphorous concentration of 0.01 [mg/l]. Phosphorous removal by evaporation and by biological processes is negligible. Phosphorous precipitates from the lake's water according to first-order kinetics, with a rate constant of 0.005/d. The outlet stream has a flow rate of 0.2 [m^3/s], which keeps the volume of water in the lake essentially constant. The concentration of phosphorous in the lake is most nearly?


Problem 10. Let's slightly adjust Problem 5 again. Redo problem 5 if SO2 is not conservative and in fact degrades at 0.23/hr; calculate its steady state concentration over the city. (The input and windspeed are still the same).


Assume that your client has contaminated 10 [m^3] of an aquifer with 60 [L] of phenol. The aquifer porosity is 0.25 and the groundwater velocity is .025 [m/d]. The phenol concentration in groundwater samples has been reported, on average, to be 10 percent of its solubility. 1) Find the mass of dissolved and undissolved phenol. 2) Estimate the time for removal of phenol by groundwater. (Assume that there is no abiotic or biotic degradation. (Assume a cross-section area of 10 m^2 for estimation of phenol flux through) Estimate the partial pressure of phenol based on the given concentration. 3) Use the following table from New Hersey Department of Environmental Protection for Phenol chemical properties:


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