Based on the following water composition, determine the alkalinity, total hardness and carbonate hardness in units of mg/L CaCO3. (Note: you may want to refer back to our notes on units and recall that CaCO3 has 2 eq/mol.) Ion Conc. (mg/L) MW (g/mol) Equiv. Conc. (meq/l) Conc (mg/L as CaCO3) Ca2+ 30 40 Mg2+ 10 24.3 Na+ 12 23 CI- 11 35.5 Alk (HCO3) 110 61

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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1. Based on the following water composition, determine the alkalinity, total hardness and
carbonate hardness in units of mg/L CaCO3. (Note: you may want to refer back to our notes on
units and recall that CaCO3 has 2 eq/mol.)
lon
Conc. (mg/L) MW (g/mol) Equiv. Conc. (meq/l)
Ca²+
30
Mg2+
10
Na+
12
CI-
11
Alk (HCO3) 110
40
24.3
23
35.5
61
Conc (mg/L as
CaCO3)
2. Jar testing conducted with the water described in problem 1 determined an optimum alum dose
of 20 mg/L for particle removal. Based on this alum dose, determine (a) the amount of natural
alkalinity (mg/L as CaCO3) consumed, (b) the amount of alkalinity remaining, and (c) the amount
of alum required (kg/yr) if the treated flow is 10 MGD.
3. The particles created at the conclusion of the rapid mix step associated with the alum addition
in problem 2 have an average diameter of 20 µm and specific gravity of 2.0. During flocculation,
the size increases to 75 µm, but the more open aggregate structure decreases the specific
gravity to 1.9. The water temp is 18 °C. Calculate the settling velocity of both particles. How
does the change in particle properties impact the settling velocity? Make sure to check the
Reynolds Number.
4. For this system, it is proposed to use a mechanical rapid-mix tank to add and mix the alum and a
horizontal-shaft paddle flocculator to aid in floc formation. Use typical design values noted in
the text (or notes) to determine the volume and power required for both units.
5. For the particles in problem 3, determine the percent removal in a sedimentation basin with a
depth of 2.5 m, width of 4 m and length 40 m at a flowrate of 10 MGD. How much do the
particle properties influence removal?
Transcribed Image Text:1. Based on the following water composition, determine the alkalinity, total hardness and carbonate hardness in units of mg/L CaCO3. (Note: you may want to refer back to our notes on units and recall that CaCO3 has 2 eq/mol.) lon Conc. (mg/L) MW (g/mol) Equiv. Conc. (meq/l) Ca²+ 30 Mg2+ 10 Na+ 12 CI- 11 Alk (HCO3) 110 40 24.3 23 35.5 61 Conc (mg/L as CaCO3) 2. Jar testing conducted with the water described in problem 1 determined an optimum alum dose of 20 mg/L for particle removal. Based on this alum dose, determine (a) the amount of natural alkalinity (mg/L as CaCO3) consumed, (b) the amount of alkalinity remaining, and (c) the amount of alum required (kg/yr) if the treated flow is 10 MGD. 3. The particles created at the conclusion of the rapid mix step associated with the alum addition in problem 2 have an average diameter of 20 µm and specific gravity of 2.0. During flocculation, the size increases to 75 µm, but the more open aggregate structure decreases the specific gravity to 1.9. The water temp is 18 °C. Calculate the settling velocity of both particles. How does the change in particle properties impact the settling velocity? Make sure to check the Reynolds Number. 4. For this system, it is proposed to use a mechanical rapid-mix tank to add and mix the alum and a horizontal-shaft paddle flocculator to aid in floc formation. Use typical design values noted in the text (or notes) to determine the volume and power required for both units. 5. For the particles in problem 3, determine the percent removal in a sedimentation basin with a depth of 2.5 m, width of 4 m and length 40 m at a flowrate of 10 MGD. How much do the particle properties influence removal?
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