EVEG 3110_HW_1_Assigned_01_30_24_moe (1)

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1 Department of Civil and Environmental Engineering Louisiana State University EVEG 3100 Spring 2024 Water and Wastewater Treatment Homework: Assignment #1 Due: Feb. 6, 2024 1. Based on the tabulated information provided below for analysis of a water sample, the total solids concentration of the water (in mg/L) is most nearly? Mass of empty dish 78.012 g Mass dish + dry solids 78.119 g Mass dish + ignited solids 78.108 g Volume of water sample 185 mL A. 5.8×10 -3 B. 5.8×10 -1 C. 5.9×10 1 D. 5.2×10 2 E. 5.8×10 2 2. Based on information presented in Problem 1, the total volatile solids concentration in the water (in units of mg/L) was most nearly? A. 5.8×10 -3 B. 5.9×10 -2 C. 5.9×10 1 D. 5.2×10 2 E. 5.8×10 2 3. Given the following data for a water sample, the total suspended solids (TSS) concentration in units of mg/L is most nearly? Suspended solids data Weight of empty dish + filter disk 2.1200 g Weight dish + filter disk + dry solids 2.1382 g Weight dish + filter disk + ignited solids 2.1325 g Volume of water sample filtered 525 mL Dissolved solids data Mass of empty dish 85.3373 g Mass dish + dry solids 85.3770 g Mass dish + ignited solids 85.3753 g Volume of water sample 85 mL A. 3.5×10 -5 B. 3.5×10 -2 C. 1.1×10 2 D. 2.4×10 2 E. 3.5×10 2

2 4. Based on the data presented in Problem 3, the percentage of total suspended solids that are volatile suspended solids is most nearly? A. 11% B. 19% C. 31% D. 46% E. 68% F. 320% 5. Based on the information presented in Problem 3, the concentration of fixed dissolved solids for the water (in units of mg/L) is most nearly? A. 2.4×10 1 B. 3.2×10 1 C. 4.4×10 2 D. 4.7×10 2 E. 5.0×10 2 6. Based on the information presented in problem 3 above, the percentage of total dissolved solids that are volatile is most nearly? A. 6.8 B. 11 C. 31 D. 68 E. 93 7. A water sample contains 16 mg/L of nitrate (NO 3 - ). The concentration of nitrate expressed in units of parts per million (ppm) is __________________(fill in the blank). 8. 8. Based on the information presented in the preceding problem, the concentration of nitrate expressed in units of moles/L is most nearly? A. 2.6×10 -4 B. 2.6×10 -1 C. 1.6×10 1 D. 6.2×10 1 E. 1.6×10 4 9. Chlorophenols impart unpleasant taste to drinking water at concentrations as low as 5 mg/m 3 . These compounds are formed when the chlorine disinfection process is applied to phenol-containing waters. The unpleasant taste threshold in units of  g/L is most nearly? A. 5×10 -6 B. 5×10 -3 C. 5×10 0 D. 5×10 3 E. 5×10 6

3 10. If a water sample at 25 o C has a [ H + ] concentration of 6.3095 × 10 -8 M, the pH of the water sample is most nearly? A. 5.0 B. 6.0 C. 7.0 D. 8.0 E. 9.0 11. If a water sample at 25 o C has pH=8.3, what will be the [ H + ] concentration in units of molarity? ____________________ (fill in the blank, expressing your answer in scientific notation with two significant figures) 12. A city will be constructing a new water treatment plant to meet their future needs. A commercial analytical lab analyzed a sample from one of the city’s potential water sources for various constituents and reported the following. Analysis of samples from the water sources yielded the following data: CONSTITUENT Sample Conc. (mg/L) Ca 2+ 9.2 Mg 2+ 2.6 Na + 202 K + 5.0 Fe 2+ 0.02 HCO 3 - 410 SO 4 2- 2 Cl - 98 F - 1.4 NO 3 - 0 Suspended solids 3.3 pH 7.0 Assume that you are an engineer assigned to analyze the data. As a first step, your supervisor has asked you to determine if the analysis appears reasonable by performing a charge balance. Specifically, you are asked to calculate the concentrations in units of meq/L for each cation and anion. Your supervisor has instructed you to consider the results to be acceptable if the summation of all cations (in units of meq/L) is within 5% of the summation of all anions (in meq/L). Based on this criterion, do that results appear reasonable? (Specify YES or NO)

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4 13. A water sample was submitted to a commercial laboratory for analysis. The pH of the water is 7.0. The laboratory has reported that the water contains the following constituents at concentrations tabulated below: [Na + ] = 0.85 mg/L, [Cl - ] = 16.6 mg/L [K + ] = 0.52 mg/L, [SO 4 2- ] = 17.3 mg/L [Mg 2+ ] = 45.5 mg/L, [HCO 3 - ] = 374.6 mg/L [Ca 2+ ] = 35.1 mg/L, [NO 3 - ] = 2.6 mg/L Based on the information provided, the hardness of this water expressed in units of meq/L is most nearly? A. 1.8 B. 3.7 C. 5.5 D. 7.1 E. 14.2 14. Based on the information presented in the preceding problem, the hardness of this water in units of mg/L as CaCO 3 is most nearly? A. 88 B. 187 C. 275 D. 353 E. 708 15. There are a number of federal laws and regulations that cover treatment of water and wastewater in the United States. With respect to drinking water supplied to communities, a major piece of legislation is the Safe Drinking Water Act (SDWA). Take a few minutes to read an overview of the SDWA in the following pdf: [ https://www.epa.gov/sites/default/files/2015-04/documents/epa816f04030.pdf ]. A key feature of the regulations resulting from implementation of the SDWA is that the US EPA has developed National Primary Drinking Water Regulations. These regulations specify maximum contaminant levels (MCLs) that are not to be exceeded in public water supplies. A printable list of the MCLs (enforcement standards) as well as secondary standards (non-enforceable guidelines) can be found in the following pdf: [ https://www.epa.gov/sites/default/files/2016-06/documents/npwdr_complete_table.pdf ]. After reviewing the two documents linked above, answer the following question. For the organic compound known as toluene (methylbenzene, chemical formula: C 7 H 8 ), the maximum allowable concentration (in units of mg/L) allowable in public water supplies in the US is most nearly? A. 0.002 B. 0.005 C. 1 D. 10 E. 1000

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