BEIRUT ARAB ARAB UNIVERSITY FACULTY OF ENGINEERING CIVIL & ENVIRONMENT ENVI RONMENTAL AL ENGINEERING ENGINEER ING DEPT. DEPT.
Water Quality Qual ity FALL 2016-2017 2016- 2017
Global Distribution Distribution of Earth’s Earth’s Water
Objectives of Water Treatment The principal objective of water treatment is to provide potable water that is chemically and biologically safe for human consumption. It should also be free from unpleasant tastes and odors. Water treatment objective is to produce both "potable" and "palatable". - Potable: - Water that can be consumed in any desired amount without concern for adverse heath effects. - Palatable: - it is a water that is pleasant to drink but not necessarily safe. Water treatment aims at producing water that satisfies a set of drinking water quality standards at a reasonable price to the consumers. Removal of solids in water. Solids maybe suspended, dissolved or colloidal.
Substances in Water Categories of substances that may be present in source waters include:
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Microbiological substances , such as: viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations and wildlife. Inorganic substances, such as salts and metals, which can be naturally occurring or result from urban storm water runoff, industrial or domestic wastewater discharges, oil and gas production, mining or farming. Pesticides and herbicides that may come from a variety of sources such as: agriculture, storm-water runoff and residential use. Organic substances synthetic and volatile, are by-products of industrial processes and petroleum production and can come from gas stations, urban storm-water runoff and septic systems. Radioactive materials which can occur naturally or result from nuclear power production and mining activities.
Physical Characteristics •
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Turbidity: is the clarity of water, measured in Nephlometer Turbidity Unit (NTU). Color: is removed from water through the coagulation and filtration stages.
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Taste & Odor
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Temperature
Chemical Characteristics Inorganic substances: include highly toxic metals, such as arsenic, cadmium, lead, and mercury; nitrites (N02) and nitrates (N03). Organic substances: classified using the three groups: •
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Synthetic organic chemicals (SOCs) are compounds used in the manufacture of a wide variety of agricultural and industrial products. They include primarily insec-ticides and herbicides. Volatile organic chemicals (VOCs) are synthetic chemicals that readily vaporize at room temperature. These include degreasing agents, paint thinners, glues, dyes. Trihalomethanes (THMs) are the by-products of water chlorination.
Biological Characteristics
Water for drinking & cooking must be free of pathogens (bacteria, virus, protozoa and worms)
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Coliform bacteria are used as an indicator organisms whose presence suggests that the water is contaminated.
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Water Quality Standards •
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EPA has set standards for more than 80 contaminants that may occur in drinking water and pose a risk to human health. The contaminants fall into two groups according to the health effects that they cause.
Acute effects occur within hours or days of the time that a person consumes a contaminant. Chronic effects occur after people consume a contaminant at levels over EPA’s safety standards for many years. The drinking water contaminants that can have chronic effects are chemicals (such as disinfection by-products, solvents, and pesticides), radio nuclides (such as radium), and minerals (such as arsenic). Examples of these chronic effects include cancer, kidney problems, etc…
BEIRUT ARAB UNIVERSITY FACULTY OF ENGINEERING CIVIL & ENVIRONMENTAL ENGINEERING DEPT.
Population Forecast
FALL 2016-2017
Population Forecast Population Forecast consists of mathematical models which are used to analyse changes in population numbers. There are several factors affecting changes in population: Increase due to births Decrease due to deaths Increase/Decrease due to migration Increase due to annexation All the above data can be obtained from the census population records.
Why is population forecasting important?
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Design of water & wastewater facilities is based on projected population of a particular city, estimated for the design period. Population forecasting is an integral part of design. It is essential to take into account the population at the end of the design period.
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Any underestimated value will make system inadequate for the purpose intended;
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Overestimated value will make it costly.
Why is population forecasting important?
Fundamental to planning (Assumptions and estimates used in determining water/sewage flows have a permanent effect on planning decisions and outcomes)
Premature and excessive investments in works
System failure and hence increasing customer complaints
Environmental impact
Essential to service provider so as to know the spare capacity of the system
Ability to accept new/unexpected demands
…Population Forecasting There are various mathematical methods to forecast population.
Arithmetic progression Geometric progression Incremental Increase Method Graphical Method Comparative Graphical Method
The most used methods are: Arithmetic progression Geometric progression
When can projections be carried out? Projections are likely to be carried out for the design of a system. A service provider should have knowledge of current demand/flow and anticipated future projections at all times. Projections should be determined:
Once the needs of the service are already known and the objectives determined
Stakeholder requirements have been identified
Adequate raw data on existing flows/demands is available
Population Densities Density No.
Classification of area
Capita / hectare
1.
2. 3.
Residential area: . small apartments
100 - 250
. apartments
240 - 700
. large apartments
750 - 1250
Commercial areas
50 -
70
Industrial areas
20 -
30
Water consumption ratio for different uses Percent No.
Classification
of total Average
1.
Domestic
50 %
2.
Commercial
15 %
3.
Industrial
15 %
4.
Public and un-accountable
20 %
Total
100 %
Fire Demand
No
Population
Required fire discharge
.
(capita)
(lit / sec . )
1
10,000
20
2
25,000
25
3
50,000
30
4
100,000
40
5
More than 200,000
50
Arithmetic Method -
Is suitable for large & old cities with considerable development.
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Using this method for small, average or new cities will give low results than the actual values.
The basic model for arithmetic change in population size is: Pn = P + a * n
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P denotes initial size, Pn denotes population at target year
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n: Number of periods
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a: average increase
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Geometric Increase Method In this method, the percentage increase in population from decade to decade is assumed to remain constant. The basic model for geometric change in population size is: Pn = P (1 + r )n
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P denotes initial size,
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Pn denotes population at target year
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n: Number of periods
Each period having a % of increasing more than 25% or negative value must be omitted from the calculation.
Example Predict the population for the years 2025, 2035, and 2045from the following census figures of a town using geometric & arithmetic methods. Year
1945
1955
Population:
60
65
(thousands)
1965 1975 1985
63
72
79
1995
2005
2015
89
97
120
…Solution Year
Population:
Increment
Percentage Increment
(thousands)
per Decade
per Decade
1945
60
-
-
1955
65
+5
(5÷60) x 100 = +8.33
1965
63
-2
(2÷65) x 100 = -3.07
1975
72
+9
(9÷63) x 100 = +14.28
1985
79
+7
(7÷72) x 100 = +9.72
1995
89
+10
(10÷79) x 100 = +12.66
2005
97
+8
(8÷89) x 100 = +8.98
2015
120
+23
(23÷97) x 100 = +23.71
Net values
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+62
+80.75
Averages
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10.33
11.53%
…Solution (using Arithmetic method) Solution •
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Population for 2025 = Population 2015 + a*n = 120 + 10.33*1 = 130.33 Population for 2035 = Population 2015 + a*n = 120 + 10.33*2 = 140.66 Population for 2045 = Population 2015 + a*n = 120 + 10.33*3 = 150.99
…Solution (using Geometric method) Solution •
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Population for 2025 = Population 2015 x (1+i/100) t = 120 x (1+11.53/100), where i = 11.53 , t = 1 = 133.83 Population for 2035 = Population 2015 x (1+i/100) t = 120 x (1+11.53/100)2, where i = 11.53 , t = 2 = 149.26 Population for 2045 = Population 2015 x (1+i/100) t = 120 x (1+11.53/100)3, where i = 11.53 , t = 3 = 166.47
Water for Fire-Fighting
Qf 1 Qf 2
=
=
P * 3182/60
=
64 P 1 0.01 P −
P: Population in thousands
L/sec
=
L/sec
