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reply ma as soon as possible 120 points total Due: October 23, 2019 Budget your time...

reply ma as soon as possible
120 points total Due: October 23, 2019 Budget your time carefully TRUE OR FALSE (45 points - 3 points cach): Mark whether the
MULTIPLE CHOICE: (5 points each, 35 points total) Choose the most appropriate answer to the following for those problems requ
Analytical Problems (40 points total) 23. (10 points) A 25.0-m secondary clarifier has an influent total suspended solids con
26. (8 points) The laboratory reported the following data related to the mixed liquor suspended solids concentration in the a
120 points total Due: October 23, 2019 Budget your time carefully TRUE OR FALSE (45 points - 3 points cach): Mark whether the statements as written are "true" or "false". If the statement is false, make minor changes to the statement so that the statement is true. The primary adverse health effect resulting from the disposal of mercury wastes into Minamata Bay was dysentery The flow regime in horizontal velocity grit chambers approaches continuous mixed flow Screening and comminution are preliminary treatment processes. A bar rack is a device consisting of parallel bars evenly spaced that is placed in a waterway to remove debris, suspended solids, and floating solids from a wastewater In pretreatment operations, aeration is usually accomplished by cascades, multiple tray aerators, spray nozzles, or diffused compressed air tanks. Total solids (TS) refers to the residue left behind in a drying dish after igniting at 450+50°C Flow equalization dampens the daily variation in flow rate, along with variations in BOD suspended solids, etc. Oftentimes, grit from horizontal velocity grit chambers is washed to free it from any organic particles that may have been collected on it. The reason grit is removed as much as possible is to prevent wear on pumps, accumulations in acration tanks, clarifiers, and digesters; and clogging of sludge piping A mass balance performed on a steady state process involving a first-order chemical reaction for component using a continuous stirred tank reactor and a plug-flow reactor system, results in a differential equation and an algebraic equation, respectively. The residence time for a particular unit operation is defined as the average time that a fluid clement remains within that unit operation, and can be described mathematically as t-QIV. For a given level of conversion, the continuous stirred tank reactor (CSTR) will provide a smaller reactor volume and smaller detention time than a plug flow reactor. The performance equation describing dispersed plug-flow is given by: CN- 41 cxp [12. (LDL CA (1 + i)exp(1/2 (LID)) - (1-1) exp(1/2 (LID)) where: 1 = [1 + 4% (Divz)). (dimensionless) V = velocity in the radial direction, (length time) L = reactor length, (length) D-longitudinal or axial dispersion coefficient, (length time) rate constant, (time) In dispersed plug-flow reactors, the flow regime is between plug-flow and completely mixed flow. Primary treatment of a wastewater utilizes sedimentation to remove a substantial amount of the suspended solids. 15. MULTIPLE CHOICE: (5 points cach, 35 points total) Choose the most
MULTIPLE CHOICE: (5 points each, 35 points total) Choose the most appropriate answer to the following for those problems requiring short calculations, vowed to show your work to receive full credit 16._ What devices remove materials which would damage equipment or interfere with a process? (a) Grit; (b) Screening: (c) Oxidation: (d) Reduction What represents the heavier inert material in wastewater? (a) Debris: (b) Waste: (c) Screens (d) Grit. Turbidity is wastewater is caused by: (a) Color (b) Hardness (c) Dissolved calcium: (d) Finely divided suspended material The chemicals that are added to distilled water for the BOD test serve what purpose? (a) Assure the presence of dissolved oxygen at all times: (b) Increase the thermal conductivity of the solution (c) Adjust the pH within the desirable range and provide essential elements for growth of the biological microorganisms actually exerting the oxygen demand; (d) Satisfy the natural oxygen demand that might exist in the sample. A mechanical bar screen has bars -inch thick and 1%-inch clear spacing between the bars. If the velocity through the bars is 3.0 ft/sec, then the approach velocity before the bar screen is (a) 3.0 ft/sec (b) 2.8 ft sec (c) 2.14 fusce (d) 3.05 itsee (e) None of the above. For the above problem, determine the associated head loss through the screen, (a) 0.068 ft (b) 0.071 (c) 0.098 (d) 1.00 ft (e) Oft (0) 0.0096 (g) None of the above. A groundwater containing 10.0 m L of CO2 is to be degasified using a multiple tray aerator with four trays. The k value is 0.33. The Co, content of the product water is predicted to be: (a) 10.0 mg/L (b) OmpL (s) 297 mg/L (d) 2.67 mg/L (e) 3.68 mol (0) None of the above
Analytical Problems (40 points total) 23. (10 points) A 25.0-m secondary clarifier has an influent total suspended solids concentration of 3,000 mg L The flow into the clarifier is 17 500 m day. Assume the effluent solids are completely removed from the effluent (ie.. . 01 determine the return (underflow) flow rate required to obtain an underflow solids concentration of 7,500 mg/L. - Inlet well Discharge 24. (6 points) Determine the volume of a tank (in gallons) if it is 12.0 feet deep and has a diameter of 250 feet 25. (6 points) For the above tank, determine the time to fill the tank if the flow rate entering the tank is 1.25 x 10 gallons day.
26. (8 points) The laboratory reported the following data related to the mixed liquor suspended solids concentration in the activated sludge process: Initial weight of filter disk: 0.45 gms Volume of filtered sample: 60 ml Weight of filter disk + filtered residue: 0.775 gms From the data provided, determine the mixed liquor suspended solids concentration. 27. (10 points) A BOD analysis was started on Monday. 30.0 ml of waste with a dissolved oxygen (DO) concentration of zero was mixed with 270 ml of dilution water with a DO concentration of 100 mp L. The sample was put in the incubator. Since the day falls on a Saturday and lab personnel do not work on Saturdays, the final D determination does not get measured until Monday, the day. The final DO was measured at 4.0 mg L. The lab personnel discover that the incubator was mistakenly set at 30°C. Assume a rate constant ki of 0-2 days and is 1.047. From the data provided, determine the 5-day BOD of the sample at 20°C.
0 0
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Answer #1

1) True

2) True

3) True

4) True

5) True

6) Fa(24) Volume of tank = Area x deep = 5887.5 feet = 36682.2 gallonslse

7) True

8) False

9) True

10)

11)True

12) False ( CSTR need larger reaction volume achieve the same reaction rate )

13) True

14) True

15) True

16) a(Grit)

17) d(Grit)

18) d(finely divided suspended material)

19) c

20) (20) Assume , V. = Approach velocity before the bar seren = Velocity through the bar. V, A, = V₂ A₂ Az Wspace 3/4 A = Whart Wc

21) g

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