Chapter 7. Water Quality
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Transcript of Chapter 7. Water Quality
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Dr. BUNRITH SENG
Chapter 7
Water Quality
Mobile : +81 (0) 80 3259 9952
E-mail: [email protected]; [email protected]
Department of Civil Engineering, Zaman University
No. 8, St. 315, 12151 Phnom Penh, Cambodia
Zaman University Department of Civil Engineering
No. 8, St. 315, 12151 Phnom Penh, Cambodia
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Important Water Quality Parameters
Dissolved Oxygen/Oxygen demand
Solids
Nitrogen
Infectious bacteria and viruses
Water quality parameters
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Dissolved Oxygen
The measurement of the rate at which this oxygen is used by microorganisms decomposing organic matter.
Theoretical oxygen demand (ThOD)
Biochemical oxygen demand (BOD)
Chemical oxygen demand (COD)
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Dissolved Oxygen (Cont.)
Theoretical oxygen demand (ThOD)
The oxygen demand for the decomposition of pure materials can be estimated from stoichiometry, assuming that all the organic material completely decomposes.
CaHbOc + O2 CO2 + H2O
CaHbNc Od + O2 CO2 + H2O + NH3
ThOD = C-ThoD + N-ThOD
C-ThOD is due to the decomposition of the carbonaceous (organic) material and N-ThOD is due to the stabilization of nitrogenous material (NH3 to NO3
-)
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Example1: What is the theoretical oxygen demand in mg/L for a
1.67x10-3 molar solution of glucose, C6H12O6, to decompose completely?
Solution:
O6H 6CO 6O OHC 2226126
1 mol 6 mol
1.67 mol x ?mol 2O of mol 02.101
667.1
x
1 mol of O2 = 16x2 =32 g
L
mgO 321 32 02.10 2
2Om
Dissolved Oxygen (Cont.)
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Dissolved Oxygen (Cont.)
Example2: What is the theoretical oxygen demand in liters of air for
a 300 mg/L solution of methylamine, CH3NH2, to decompose completely?
Solution:
32225 NH OH CO 1.5O NCH
31 g 1.5x32 g
0.3 g x g Lgx /O 4645.0
31
323.05.12
1 mol of O2 = 22.4 L O2
1 L of Air = 0.21 L O2
221.0
14.22
32
4645.0
O
air
L
L
mol
LmolThODC
solution
air
L
LThODC 55.1
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Dissolved Oxygen (Cont.)
OH HNO 2O NH 2323
Solution (cont.):
17 g 2x32 g
0.3 g x g
solutionO
air
LL
L
mol
LmolThODN airL
06.221.0
14.22
1
23.0
2
ThOD-N ThODCThOD
Total Oxygen Demand
solutionair/LL 61.306.255.1ThOD
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Dissolved Oxygen (Cont.)
Biochemical oxygen demand (BOD)
The measure of the amount of oxygen required by aerobic bacteria and other microorganisms to stabilize decomposable organic matter.
A very low rate of O2 consumption would indicate:
Contamination is absent,
The available microorganisms are uninterested in consuming the available organics, or
The microorganisms are dead or dying.
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BOD Bottle 300 mL
BOD Measurement
Dissolved Oxygen (Cont.)
The standard BOD test is run in the dark at 20oC for 5 days (BOD5).
Dark: algae may be presented and will produce O2 in
the bottle if light is available. 20oC: The rate of oxygen consumption is
temperature dependent. 5 days: Standard duration (it can be measured
shorter or longer than 5 days).
BOD is a difference of DO at initial and final day of the measurement.
FI DODOBOD Where: DOI : Initial DO, mg/L DOF : Final DO, mg/L
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Dissolved Oxygen (Cont.)
BOD Measurement
Sample A:
FI DODOBOD
mg/L 628 BOD
Sample B:
mg/L ?08 BOD
BOD of sample B is greater than 8 mg/L. It must be diluted.
Sample C: mg/L 401048 BOD
Sample B is diluted with distilled water at a ratio 1:10.
Note:
mg/L 2FDO
mg/L 2DO
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Dissolved Oxygen (Cont.)
Example: The five-day BOD of an influent to an industrial
wastewater treatment plant is expected to be about 800 mg/L based on similar wastewaters. What dilutions should be used in a five-days BOD test?
Solution:
Assume that o The saturation is about 10 mg/L o The remaining at least 2 mg/L in the bottle
Then, The drop BOD should be 10 – 2 = 8 mg/L At least 2 mg/L of DO is to be used
Average
1008
800D
4002
800D
Dilution Factor
200D
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Dissolved Oxygen (Cont.)
The reaction in BOD bottle
CONSUMED
DO of Rate
PRODUCED
DO of Rate
OUT
DO of Rate
IN
DO of Rate
DACCUMULATE
DO of Rate
CONSUMED
DO of Rate
DACCUMULATE
DO of Rate
rVVdt
dz
Where: z : Dissolved oxygen, mg/L
z0: Initial dissolved oxygen, mg/L
t : Time
V: Volume of BOD bottle, mL
r: Reaction rate
zkdt
dz1
First-ordor reaction
tkezz 1
0
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Dissolved Oxygen (Cont.)
Balance of Oxygen in the Bottle
yzL Where: y : DO already used or demanded at any time, t, mg/L
z : DO still required to satisfy the ultimate demand, mg/L
L : ultimate demand for oxygen, mg/L
zyL
tkeLyL 1
0
)1( 1tkeLy
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Dissolved Oxygen (Cont.)
Chemical oxygen demand (COD)
A laboratory method that essentially determines the ThOD. This include both biodegradable and nonbiodegradable organic matters.
Sample + K2Cr2O7 + H2SO4
Heating
3 hours
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10-3m 1 m
Colloidal Suspended Dissolved
Solid Particle Size
• Can be removed by a membrane or glass-fiber with nominal pore size of 1.2m
• Consists of organic and inorganic matters
• Can be removed by sedimentation
• Can be removed by a membrane
• Consists of organic and inorganic matters
• Hardly/impossibly be removed by sedimentation
• Can be removed by a membrane
• Consists of organic and inorganic matters
• Hardly/impossibly be removed by sedimentation
Solids
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3 type of solid determinations
o Total solids (TS)
o Total suspended solids (TSS)
o Total dissolved solids (TDS)
o Total suspended solids (TSS)
o Volatile suspended solids (VSS)
o Fixed suspended solids (FSS)
Total suspended solids
FSSVSSTSS
Total dissolved solids
o Total dissolved solids (TDS)
o Volatile dissolved solids (VDS)
o Fixed dissolved solids (FDS)
FDSVDSTDS
TDSTSSTS
Solids (Cont.)
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Experimental Procedure
Sample Filter with Glass fiber ( = 2m) (V mL)
Retained on the filter
Filtrate
Drying Owen
TDS (m1)
TSS (m`1)
Burning
Furnace of 530-550oC for 15-20 min
180 oC for 1h
103-105oC for 1h
FDS (m2)
FSS (m`2)
V
mmLmgVSS
`
2
`
1)/(
V
mmLmgVDS 21)/(
Solids (Cont.)
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Solids (Cont.)
Evaporating Dish
Glass fiber filter
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Example: A laboratory runs a solids test. The weight of the crucible
= 48.6212g. A 100 mL sample is placed in the crucible and the water is evaporated. The weight of the crucible and dry solids = 48.6432 g. The crucible is placed in a 600oC furnace for 24hr and cooled in a desiccators. The weight of the cooled crucible and residue, or unburned solids = 48.6300 g. Find the total, volatile and fixed solids.
Solution:
Solids (Cont.)
mg/L 22010
100
6212.486432.48 6
mL
gTS
mg/L 8810
100
6212.486300.48 6
mL
gFS
mg/L 132 88220 VS
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o Nitrogen is the largest single component of the earth’s atmosphere (78.08% by volume, 75.5% by weight) and their compounds play a vital role in water resources, in the life processes of all living organisms
o Nitrogen is an essential nutrient for biological growth, normally comprising about 12-14% of the mass of cell protein.
o Forms of nitrogen in the environment range from organic and ammonium nitrogen (oxidation state minus 3), through nitrogen gas (zero), to nitrite (plus 3) and nitrate (plus 5).
o Organic and ammonium nitrogen are the main forms present in municipal wastewater and are often measured together as Total Kjeldahl Nitrogen (TKN). Total organic nitrogen present is often such that during biological treatment it is all used in cell synthesis.
Org-N = TKN ─ NH4+
Nitrogen
Overview
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Nitrification
Denitrification
Nitrogen (Cont.)
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Nitrogen (Cont.)
Measurement
A photometer used for measuring light penetration through a colored sample
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Bacteriological Measurements
Waterborne Diseases
Typhoid
Cholera
Shigellosis
Enteroviral diseases
Giardiasis
Cryptosporidiosis
Salmonellosis
Hepatitis
Others
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Bacteriological Measurements (Cont.)
The bacteriological quality of pathogenic organisms in water is commonly measured the Coliforms (150 strains of E-coli).
Coliforms (E-coli) were chosen to be the indicator organisms because:
Normal inhabitants of the digestive tracts of warm-blooded animals
Plentiful and hence not difficult to find
Easily detected with a simple test
Generally harmless except in unusual circumstances
Hardy surviving longer than most known pathogens
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The capture of gas in a tube where lactose is fermented by coliform
organisms.
- No coliforms + Have coliforms
Bacteriological Measurements (Cont.)
Laboratory Testing
Petri dish culture (cell culture plating)
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Drinking Water Quality Standard
Drinking water quality by EPA under the Safe Drinking Water
Act (SDWA)
USA Standard
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Drinking Water Quality Standard (Cont.)
Drinking water quality by EPA under the Safe Drinking Water Act (SDWA)
USA Standard
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Drinking Water Quality Standard (Cont.)
Drinking water quality
standard
CAMBODIA
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Wastewater Discharge Standard
No Parameters Unit Allowable limits for pollutant substance
discharging to
Protected public water
area
Public water area
and sewer
1 Temperature 0C < 45 < 45
2 pH 6 – 9 5 - 9
3 BOD5 ( 5 days at 200 C ) mg/l < 30 < 80
4 COD mg/l < 50 < 100
5 Total Suspended Solids mg/l < 50 < 80
6 Total Dissolved Solids mg/l < 1000 < 2000
7 Grease and Oil mg/l < 5.0 < 15
8 Detergents mg/l < 5.0 < 15
9 Phenols mg/l < 0.1 < 1.2
10 Nitrate (NO3 ) mg/l < 10 < 20
11 Chlorine ( free ) mg/l < 1.0 < 2.0
12 Chloride ( ion ) mg/l < 500 < 700
13 Sulphate ( as SO4 ) mg/l < 300 < 500
14 Sulphide ( as Sulphur ) mg/l < 0.2 < 1.0
15 Phosphate ( PO4 ) mg/l < 3.0 < 6.0
Effluent standard for pollution sources discharging wastewater to public water areas or sewer
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Category I
The sources of pollution of category I
that are subject to the prior permit from
the Ministry of Environment when the
amount of their effluent exceed ten
cubic meter per day ( 10 M3 /day ) but
not including the amount of water
volume used for cooling the engine.
Category II
The sources of pollution of category II
that shall be necessarily required to apply
for the permission from the Ministry of
Environment.
No Type of pollution sources Category
1 Canned food and meat manufacturing I
5 Flour manufacturing I
6 Sugar manufacturing I
7 Pure drinking water manufacturing I
15 Cigarette manufacturing I
16 Garment manufacturing without
chemical washing
I
17 Hotel I
18 Restaurant I
19 Animal farm I
20 Slaughter – house I
21 Garage and car cleaning I
25 Sewage treatment plant I
37 Leather manufacturing II
38 Soap and detergent manufacturing II
40 Landfill site II
41 Textile or synthetic textile II
43 Pulp and paper manufacturing II
Pollution sources required having a permission from Ministry of Environment before discharging or transporting their wastewater
Wastewater Discharge Standard (Cont.)
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Water Quality Standard in public water areas for bio-diversity conservation
No Parameter Unit Standard Value
1 pH mg/l 6.5 – 8.5
2 BOD5 mg/l 1 – 10
3 Suspended Solid mg/l 25 – 100
4 Dissolved Oxygen mg/l 2.0 - 7.5
5 Coliform MPN/100ml < 5000
1- River
2- Lakes and Reservoirs
No Parameter Unit Standard Value
1 pH mg/l 6.5 – 8.5
2 COD mg/l 1 – 8
3 Suspended Solid mg/l 1 – 15
4 Dissolved Oxygen mg/l 2.0 - 7.5
5 Coliform MPN/100ml < 1000
6 Total Nitrogen mg/l 1.0 – 0.6
7 Total Phosphorus mg/l 0.005 – 0.05
Wastewater Discharge Standard (Cont.)
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No Parameter Unit Standard Value
1 pH mg/l 7.0 – 8.3
2 COD mg/l 2 – 8
4 Dissolved Oxygen mg/l 2 - 7.5
5 Coliform MPN/100ml < 1000
5 Oil content mg/l 0
6 Total Nitrogen mg/l 1– 1.0
7 Total Phosphorus mg/l 0.02 – 0.09
3- Costal Water
Water Quality Standard in public water areas for bio-diversity conservation (Cont.)
Wastewater Discharge Standard (Cont.)
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No Parameter Unit Standard Value
1 Carbon tetrachloride µg/l < 12
2 Hexachloro-benzene µg/l < 0.03
3 DDT µg/l < 10
4 Endrin µg/l < 0.01
5 Diedrin µg/l < 0.01
6 Aldrin µg/l < 0.005
7 Isodrin µg/l < 0.005
8 Perchloroethylene µg/l < 10
9 Hexachlorobutadiene µg/l < 0.1
10 Chloroform µg/l < 12
11 1,2 Trichloroethylene µg/l < 10
12 Trichloroethylene µg/l < 10
13 Trichlorobenzene µg/l < 0.4
14 Hexachloroethylene µg/l < 0.05
15 Benzene µg/l < 10
Water Quality Standard in public water areas for public health protection
Wastewater Discharge Standard (Cont.)
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