Sketch a basic drawing of a treatment train and answer questions 1-8 based on the the document provided.

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Attached is a HW assignment for my water treatment and design class. Yo are being asked to complete questions 1-8. I have the textbook if needed.

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EGCE 572 - Water Treatment and Design • • • Complete all questions. Turn in your responses to the questions in order and stapled. There is no need to look up regulations for Ohio. Where the choice is left to you, use values from our textbook. 1 The town of Yellow Springs, Ohio (pop: 3,487), home of YSI Incorporated and Dave Chappelle, is planning to upgrade their water treatment plant (WTP). The source water will come from the Little Miami River, a river that flows through agricultural lands. It is characterized by high turbidity, fecal coliforms, and protozoa. Hardness, alkalinity, and salinity are low. Preliminary testing has shown no issues with excessive nutrients, pesticides, or other anthropogenic contaminants. Design Flow Max. Flow pH Alkalinity 229 LPCD 458 LPCD 6.7 1.55 meq/L Winter Temp. Summer Temp. TDS Turbidity 3°C 19°C 185 mg/L 75 – 175 NTU As a newly-hired engineer, you have been tasked with the preliminary design of the new water treatment plant. Here are your tasks. 1) Sketch a basic drawing of the treatment train including the relevant unit operations and chemical feeds. This is intended as an “outline” to guide you in what you need to design. 2) Design rapid mix, for the coagulation step, that is separated into two (2) basins. a) What volume (m3) must each basin be if the Gt value is 60,000 and the velocity gradient is 916 s-1? b) Should this be calculated with design flow or maximum flow and why? c) If the plan view of each basin is square and the wetted depth is 2.5m, what are the length and width (m)? d) What power input is required to meet the design velocity gradient? 3) An alum (Al2(SO4)3 x 14 H2O) dose of 105 mg/L is added during rapid mix and coagulation. a) The alum is delivered as a slurry with 13% solids by weight and a specific gravity of 1.13. What flow rate of the slurry will be added to the rapid mixers (in L/hr)? Should this be calculated with design flow or maximum flow, and why? b) How much sodium bicarbonate (NaHCO3) would need to be added in kg per day to negate the removal of alkalinity? c) If dewatering of sedimentation residuals brings the solids content of the sludge up to 65%, what is the wet mass of aluminum hydroxide sludge that will be disposed in metric tonnes per week? 2 4) Design conventional flocculation with horizontal paddle wheels and a velocity gradient of 60 s-1 in each cell. Flocculation will be split into two (2) trains with four (4) stages in each train. Each stage is to have one (1) paddle wheel. Paddle boards will be 89 mm wide and there will be two (2) boards per paddle arm with four (4) arms per wheel (8 boards total per wheel). Outer radii of the paddle boards shall be 0.60 m, and 1.10 m. a) Total residence time for flocculation will be 90 minutes. Choose which flow to use and justify your choice. Using that flow, calculate the volume of each stage. Leaving 0.5m of clearance on all sides of the paddle wheel, what are the dimensions of each flocculation stage? Design the length:depth ratio to be 1:1. What length are the paddles (m)? b) Sketch the layout of the flocculation system. Include relevant dimensions. c) What power input (in kW) will be required for the entire flocculation system? Should the equipment be designed for winter or summer temperatures? If electricity is $0.10 per kilowatt-hour, what will be the annual electrical cost of flocculation? For electrical cost, assume downtime and variation of water temperature are negligible factors. d) What rotational velocity (in rpm) will be required to obtain the desired velocity gradient? Assume that due to the shape of the basins the paddles are moving at 70% velocity relative to the water. 5) The sedimentation basins will remove 95% of particles at design flow. A pilot plant has given the following particle counts after flocculation of Little Miami River water. Settling Velocity (m/hr) # of Particles 0.2 251 0.6 389 1.0 821 1.4 1127 1.8 1350 2.2 980 2.6 268 3.0 50 3.4 0 3.8 0 a) What design overflow rate is required to meet the desired particle removal rate (m3/m2hr)? (hint: use data analysis tools in Excel to save time with this calculation) b) What percentage of particles will be removed at maximum flow? c) Design the dimensions of the sedimentation basins (m). Use two (2) basins. Use the same width as the flocculation tanks and a reasonable depth. What is the detention time in sedimentation (hrs)? 3 6) A dual-media filter is to be installed using a design filtration rate of 15 m/hr. Samples of the filter media were sifted through a stack of sieves and the results are shown below. Sieve 8 10 12 14 16 18 20 25 30 35 40 45 50 Pan Sieve Opening (mm) 2.36 2.00 1.70 1.40 1.18 1.00 0.85 0.71 0.60 0.50 0.425 0.355 0.300 ---- Anthracite Weight (g) 11 57 162 281 320 241 67 52 1 0 Sand Weight (g) 0 4 57 125 279 153 75 9 20 a) The density of the anthracite and sand are 1.7 g/cm3 and 2.65 g/cm3, respectively. The anthracite layer is 1.5 m thick and the sand layer is 1.0 m thick. What is the clean-bed head loss of this filter (m)? b) What are the uniformity coefficients of the anthracite and sand media? What does this tell you about the suitability of these two particular media for filtration? c) Calculate the UFRV, UBWV, UFWV, and recovery for this filter if run length is 48 hours, backwash rate is 40 m/hr, backwash duration is 20 minutes, and filter-to-waste duration is 20 minutes. d) Determine a reasonable design for the number of filter cells and the dimensions of each cell (m). Justify your response. 7) Assume that Ohio regulations require 6-log removal of Crytosporidium during disinfection and that the disinfection is occurring with first-order rate kinetics. a) What would be the Ct required for free chlorine? How about for ozone? b) Based on your understanding of this problem, which of those two disinfectants would be preferable? Why is it preferred? Are there other considerations to ensure safe drinking water if that disinfectant is used? c) How long (m) would a 0.65 m diameter pipe contactor need to be to ensure a proper contact time to reach the required disinfection goal? Choose a disinfectant dose based on maximum values permitted while minimizing DBP formation. d) Will dispersion be a significant factor to achieving disinfection goals in that pipe? Choose a reasonable value for the friction factor. 4 8) Now that you have designed the entire water treatment plant, draw out a plan-view plant layout with an emphasis on maximizing space efficiency. You may either sketch it out by hand or draw it using computer software. Be sure to keep all processes to scale and include all processes that you just designed. I am not requesting a schematic, but the actual plan for the plant you propose to build. This should take a bit of time, particularly when it comes to maximizing space efficiency. 5
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