(a) Why control of pH is considered important and what are the main sources of acidity and alkalinity in natural waters? (b) A 100 – ml sample require 20.2ml of 0.02 NH₂SO4 to reach the phenolphthalein end point, and a total of 25.6ml to reach the Methyl orange end point. Calculate total alkalinity and indicate what fraction corresponds to hydroxides, carbonates and bicarbonates (c) The uptake for a water supply system is located at a location named X3 (see Figure); upstream X3, there are two villages that discharge raw sewage at X1 and X2, and new wastewater treatment systems are needed in both villages in order to reduce the concentration of BOD. Calculate the current concentration of BOD at X3, and the required removal efficiency (% BOD removal) in the new wastewater treatment works (WWTW) to control BOD discharges at X1 and X2, so the BOD at X3 ≤ 10mg/L.

Structural Analysis
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Chapter2: Loads On Structures
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6. Please answer the following questions:
(a) Why control of pH is considered important and what are the main sources of acidity and
alkalinity in natural waters?
(b) A 100 ml sample require 20.2ml of 0.02 NH2SO4 to reach the phenolphthalein end
point, and a total of 25.6ml to reach the Methyl orange end point. Calculate total alkalinity and
indicate what fraction corresponds to hydroxides, carbonates and bicarbonates
(c) The uptake for a water supply system is located at a location named X3 (see Figure);
upstream X3, there are two villages that discharge raw sewage at X1 and X2, and new
wastewater treatment systems are needed in both villages in order to reduce the concentration
of BOD. Calculate the current concentration of BOD at X3, and the required removal
efficiency (% BOD removal) in the new wastewater treatment works (WWTW) to control
BOD discharges at X1 and X2, so the BOD at X3 ≤ 10mg/L.
Transcribed Image Text:6. Please answer the following questions: (a) Why control of pH is considered important and what are the main sources of acidity and alkalinity in natural waters? (b) A 100 ml sample require 20.2ml of 0.02 NH2SO4 to reach the phenolphthalein end point, and a total of 25.6ml to reach the Methyl orange end point. Calculate total alkalinity and indicate what fraction corresponds to hydroxides, carbonates and bicarbonates (c) The uptake for a water supply system is located at a location named X3 (see Figure); upstream X3, there are two villages that discharge raw sewage at X1 and X2, and new wastewater treatment systems are needed in both villages in order to reduce the concentration of BOD. Calculate the current concentration of BOD at X3, and the required removal efficiency (% BOD removal) in the new wastewater treatment works (WWTW) to control BOD discharges at X1 and X2, so the BOD at X3 ≤ 10mg/L.
QR LR
Q₁
L₁
X₂ ↓
River
LR= 5 mg/L ; QR= 1000, L/s
Q1 = 200 L/s ; L1= 200 mg/L; X1 = 0km;
Q2 = 150 L/s; L2 = 500 mg/L; X2 = 8km;
Q3 = 180 L/s ; L3= 10 mg/L; X3 = 16km
k = 0.5 d-1
u = 10km/d
Mg(HCO3)2 = 73;
CaCl₂ = 111;
Ca(HCO3)2 = 81;
MgSO4 = 40;
MgCl2 = 95.
L3
X3
(d) Calculate temporary and permanent hardness of a sample of water which contains
the following dissolving salts in milligrams per litre:
Transcribed Image Text:QR LR Q₁ L₁ X₂ ↓ River LR= 5 mg/L ; QR= 1000, L/s Q1 = 200 L/s ; L1= 200 mg/L; X1 = 0km; Q2 = 150 L/s; L2 = 500 mg/L; X2 = 8km; Q3 = 180 L/s ; L3= 10 mg/L; X3 = 16km k = 0.5 d-1 u = 10km/d Mg(HCO3)2 = 73; CaCl₂ = 111; Ca(HCO3)2 = 81; MgSO4 = 40; MgCl2 = 95. L3 X3 (d) Calculate temporary and permanent hardness of a sample of water which contains the following dissolving salts in milligrams per litre:
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