Water and Wastewater Engineering

Water Quality & Supply

Raw Water Source The various sources of water can be classified into two categories: Surface sources Ponds and lakes Streams and rivers Storage reservoirs , and Oceans Sub-surface sources or underground sources Springs Infiltration wells , and Wells and Tube-wells

Spring A spring is any natural occurrence where water flows on to the surface of the earth from below the surface, A spring formed where surface water has infiltrated the Earth's surface (recharge area), becoming part of the area groundwater. The groundwater then travels through a network of cracks and fissures - openings ranging from intergranular spaces to large caves The water eventually emerges from below the surface, in the form of a spring.

Infiltration Wells Digging or drilling a well near the banks of a stream or river is the cheapest and simplest method of development. The well should be close enough to the river channel to collect both water flowing underground and water seeping in through the channel, as shown in Figure . Generally, this will provide a very good supply of water throughout the year. Even if the river dries up during times of little rain, water will be available from the ground. The water will also be filtered naturally. Water from the stream passes through the sand and silt in the river bank and impurities are removed. The degree of purification will depend on the extent of contamination of the stream and on the soil type. In many cases, the purification process will be sufficient to make treatment unnecessary. A hand pump, windmill or power pump can be installed to extract the water and pump it through the system.

DRINKING WATER REGULATIONS If water analysis indicates a water system is exceeding a maximum contamination level (MCL) for a contaminant, the system must either stop providing the water to the public or treat the water to reduce the contaminant concentration to below the MCL.

Primary drinking-water standards Potential chronic effects are the reason why metals such as lead and cadmium, organic pollutants such as solvents, and pesticides are regulated. The EPA sets primary standards for many of the pollutants. Setting standards involves two steps. (1) It determines a maximum contaminant level goal (MCLG), a level not expected to cause adverse health effects even over a lifetime of exposure. (2) Because achieving the MCLG is not always possible, the EPA also sets an achievable maximum contaminant level (MCL).

Secondary drinking-water standards Secondary standards are designed to protect ‘‘public welfare”. They are guidelines for substances that affect the water’s aesthetic qualities, such as taste, odor, and color, but that do not pose a health risk. They are unenforceable unless individual states treat them as enforceable.

Water Quality Physical Parameters Physical parameters define those characteristics of water that respond to the sense of sight, touch, taste, or smell. The six most commonly considered physical characteristics are suspended solid, temperature, taste and odour, colour

Water Quality Physical Characteristics a) Suspended solid – measured in mg/L Sources: (i) Inorganic compounds such as clay, silt, sand (ii) Organic compounds such as fine organic matter, human waste Effect: (i) Aesthetic (affect turbidity and transparency of water (ii) Health aspect (iii) Adsorption point/centre for chemicals and micro- organisms

Water Quality

Water Quality b. Turbidity – measured in NTU/FTU (nephelometric / Formazin turbidity units) Sources: (i) Inorganic compounds such as clay, sand (ii) Organic compounds such as plant fiber, human waste Effect: (i) Aesthetic (ii) Health aspect (iii) Adsorption point/centre for chemicals and micro- organisms

Turbidity – measured in NTU/FTU Water Quality Turbidity – measured in NTU/FTU

Water Quality (i) Inorganic compounds such as minerals, metals, c. Odour and Taste Sources: (i) Inorganic compounds such as minerals, metals, salts (all of them give taste to water but no odour) (ii) Organic compounds from petroleum and/or degradation of organic matters (odour and taste) Effect: (i) Aesthetic (ii) Health problem

Water Quality d. Temperature – measured in ˚C or ˚F Sources: (i) Effect from ambience (ii) Industrial activities such as cooling system Effect: (i) Disturb biological activities such as micro- organism and aquatic life (ii) Chemical properties such as the degree of gas solubility, density and viscosity

Water Quality Chemical Parameters The chemical characteristics of water are numerous.  Every substance that dissolves in water can be called a chemical water quality characteristic.  Chemical parameters are includes total dissolved solid, alkalinity, hardness, metals, organic compounds, and nutrients.

Water Quality Chemical Characteristics a) Total Dissolved Solid (TDS) Sources: (i) Inorganic compounds such minerals, metal and gases (ii) Organic compounds such as product from degradation of organic matter or organic gas Effect: (i) cause taste, colour and odour problem (ii) Health aspect (iii) small amount of TDS – water become corrosive Note: Recommended TDS concentration for drinking water supply is 500 mg/L

Water Quality b) Alkalinity Definition: the quantity of ions in water to neutralize acid or measure of water strength to neutralize acid - Main constituents are bicarbonate (HCO3- ),carbonate (CO32- ) and hydroxide (OH- ) ions. Sources: (i) Mineral dissolved in water and air (ii) Human activities such as fertilizers, detergent, pesticide etc. Effect: (i) Non pleasant taste (ii) Reaction between alkaline constituent and cation (positive ion) produces precipitation in pipe.

Water Quality Fertilizer Agriculture pesticide

Water Quality c) Hardness Definition: a measure of “multivalent” cations in water such as Ca2+, Mg2+, Fe2+, Mn3+ Sources: (i) Natural mineral on earth Effect: (i) Excessive soap usage (ii) Precipitate form on hardware (iii) Precipitate in pipe – temperature and pH increased Note: Recommended Iron concentration in Water Supply is 0.3 mg/L Desirable concentration of Mn in Drinking water is 0.01 – 0.05 mg/L

Effects on water supply Water Quality Effects on water supply Iron deposit on valve pipe

Water Quality d) Metals – non toxic and toxic Non Toxic Dangerous for health if the concentration is high Example: Ca2+, Mn2+, Fe2+, Zn2+, Al3+, + etc. Source: (i) Mineral, readily available from nature Effect: (i) Colour, odour, taste and turbidity (ii) Deteriorate health (at high concentration)

Water Quality d) Metals – non toxic and toxic Toxic Stored up in food chain Example: Pb2+, Hg2+, Cd2+ etc. Source: (i) Human activities such as mining and industries Effect: (i) Dangerous diseases such as cancer, abortion and deformation in new born baby Note: For Domestic Water Supply Metals level should be: Pb < 0.05 mg/L Hg < 0.02 mg/L Cd < 0.01 mg/L

Water Quality e) Nutrients - Important elements - N, P Nitrogen (N) Note: For Domestic Water Supply Nutrients level should be: NO3- < 10.0 mg/L NO2- < 1.0 mg/L e) Nutrients - Important elements - N, P Nitrogen (N) Sources: (i) Major sources are domestic and industrial (ii) Decomposition to a simple compound (iii) Animals and human wastes; chemicals (fertilizers) Effect: (i) NO3- poisoning in human and animal babies (ii) Excessive algae breeding and aquatic plants

Water Quality e) Nutrients (cont.) Phosphorus (P) Sources: (i) Readily present in soil (ii) Chemicals (fertilizers) (iii) Domestic and human wastes etc. Effect: (i) Excessive algae breeding and aquatic plants (ii) 0.2 mg/L – disturb coagulation process in water treatment plant Note: For Domestic Water Supply Nutrients level should be: PO4- < 50.0 mg/L

Causes of water pollution Pathogens The most important biological organisms in water are pathogen These organisms are capable of infecting and transmitting diseases to human Pathogens are not native to aquatic system and usually require an animal host for growth and reproduction. Major groups of pathogens of interest in water supply and treatment are bacteria, viruses, protozoa, fungus and algae.

Causes of water pollution Pathogen Indicator The presence of pathogenic microorganisms is shown by indicator organisms. Their presence shows that pollution has occurred and suggests the nature, type and level of pollution. Indicator micro-organisms properties; Can be used for all type of waters, Always present when pathogen is absent, Easily experimented and give reliable results, Not be a pathogen itself

Water Quantity Estimation

Quantity = Per capita demand x Population Water Quantity Estimation The quantity of water required for municipal uses for which the water supply scheme has to be designed requires following data: Water consumption rate (Per Capita Demand in liters per day per head) Population to be served       Quantity = Per capita demand x Population

Water Consumption Rate It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following classes: Sl.No Types of consumption Normal range ( lit/capita/day) Average % 01 Domestic consumption 65-300 160 35 02 Industrial and Commercial demand 45-450 135 30 03 Public uses including fire demand 20-90 45 10 04 Losses and Waste 45-150 62 25

Factors Affecting Water Use Many factors affect the amount and timing of water use: population size and character: climate; the types of water uses in the region; the cost of water; public commitment to environmental protection and restoration; public attitude toward conservation and wastewater reuse; water management practices; federal, state, local government laws and ordinances; and tourism. Population. The amount of water used in a locality is directly related to the size, distribution, and composition of the local population. Forecasts of future water use depend,in part, on population forecasts as well. Climate. The amount of water used in a locality is influenced by its climate. Lawn irrigation, gardening, bathing, irrigation, cooling, and many other water uses are directly affected.

Types of Water Uses. The type and scale of residential, commercial, industrial, and agricultural development in an area define the levels and timing of water uses. Economic Conditions. Economic health is reflected in all aspects of resource management and development. Inflation and other economic trends influence the availability of funds for water supply, wastewater treatment, and environmental and other programs, and they affect the attitudes of individuals as well. Environmental Protection. Social attitudes toward environmental protection and enhancement strongly affect water allocation and use. Water use forecasts must take into account the amount of water that is to be dedicated to environmental protection and restoration. This quantity can be substantial.

Conservation. Attractive alternatives to developing new water supplies are conservation practices and the reuse of wastewater and storm water. These approaches, although not a panacea, can at least delay the need for additional water supplies and/or the development of new facilities. Management Practices. water management practices, including interbasin transfers, saline water conversion, water reclamation and reuse, and many other practices influence water use trends . The impact of technological change on water use can be significant. Tourism. Some states, have annual tourist populations that significantly exceed their resident populations. The impacts of such occurrences must be recognized when forecasting future water demands.

Population Forecasting Methods The various methods adopted for estimating future populations are given below. The particular method to be adopted for a particular case or for a particular city depends largely on the factors discussed in the methods, and the selection is left to the discretion and intelligence of the designer. Arithmetic Increase Method Geometric Increase Method Incremental Increase Method Decreasing Rate of Growth Method Simple Graphical Method Comparative Graphical Method Ratio Method Logistic Curve Method

Pn = Pi + nI Arithmetic Increase Method This method is based on the assumption that the population increases at a constant rate; i.e. dP/dt=constant=k; Commonly used for short term estimates (1-5 years) only Can be used for big/old city which is almost fully developed Pn = Pi + nI Pn = number of population in year n Pi = number of current population n = number of year per decade I = average population growth rate per decade

Population is assumed to increase in proportion to the number of population present Based on percentage of population increment between decades Suitable for rapidly developing cities Pn = Pi (1 + i/100)n i = average percentage of population growth per decade

Pn = Pi + n(I + m) Combination of arithmetic and geometric method Incremental Increase Method The population for a future decade is worked out by adding the mean arithmetic increase to the last known population as in the arithmetic increase method, and to this is added the average of incremental increases, once for first decade, twice for second and so on. Combination of arithmetic and geometric method m = average increment growth per decade Pn = Pi + n(I + m)

Decreasing Rate of Growth Method In this method, the average decrease in the percentage increase is worked out, and is then subtracted from the latest percentage increase to get the percentage increase of next decade. Simple Graphical Method In this method, a graph is plotted from the available data, between time and population. The curve is then smoothly extended up to the desired year. This method gives very approximate results and should be used along with other forecasting methods.

Comparative Graphical Method In this method, the cities having conditions and characteristics similar to the city whose future population is to be estimated are selected. It is then assumed that the city under consideration will develop, as the selected similar cities have developed in the past.

Ratio Method In this method, the local population and the country's population for the last four to five decades is obtained from the census records. The ratios of the local population to national population are then worked out for these decades. A graph is then plotted between time and these ratios, and extended up to the design period to extrapolate the ratio corresponding to future design year. This ratio is then multiplied by the expected national population at the end of the design period, so as to obtain the required city's future population. Drawbacks Depends on accuracy of national population estimate. Does not consider the abnormal or special conditions which can lead to population shifts from one city to another.

The curve is S-shaped and is known as logistic curve. Logistic Curve Method The three factors responsible for changes in population are : Births Deaths, and Migrations Logistic curve method is based on the hypothesis that when these varying influences do not produce extraordinary changes, the population would probably follow the growth curve characteristics of living things within limited space and with limited economic opportunity. The curve is S-shaped and is known as logistic curve.

Logistic Curve

Predict the population for the years 1981, 1991, 1994, and 2001 from the following census figures of a town by different methods.

Intake Structure The basic function of the intake structure is to help in safely withdrawing water from the source over predetermined pool levels and then to discharge this water into the withdrawal conduit (normally called intake conduit), through which it flows up to water treatment plant.

Intake Structure

Factors Governing Location of Intake As far as possible, the site should be near the treatment plant so that the cost of conveying water to the city is less. The intake must be located in the purer zone of the source to draw best quality water from the source, thereby reducing load on the treatment plant. The intake must never be located at the downstream or in the vicinity of the point of disposal of wastewater. The site should be such as to permit greater withdrawal of water, if required at a future date. The intake must be located at a place from where it can draw water even during the driest period of the year. The intake site should remain easily accessible during floods and should not get flooded. Moreover, the flood waters should not be concentrated in the vicinity of the intake.

Conveyance There are two stages in the transportation of water Conveyance of water from the source to the treatment plant. Conveyance of treated water from treatment plant to the distribution system. In the first stage water is transported by gravity or by pumping or by the combined action of both, depending upon the relative elevations of the treatment plant and the source of supply. In the second stage water transmission may be either by pumping into an overhead tank and then supplying by gravity or by pumping directly into the water-main for distribution.

HOMEWORK 1 a) Calculate water used by sectors; domestic, industry and commercial, public, water losses and fire-fighting Given Water demand = 270 Lpcd Pop. = 50 000 peoples

2) A community has experienced the growth in population and water use shown below. Estimate the population in the year 2010 using the following methods: Arithmetic; Geometric and Incremental Increase Year 1950 1960 1970 1980 1990 Population 8000 8990 11300 14600 18400

3) A community has experienced the growth in population and water use shown below. Estimate the population in the year 2001 using the following methods: Arithmetic; Geometric and Incremental Increase Year 1921 1931 1941 1951 1961 1971 1981 1991 Population 6420 8250 10700 12372 15225 17925 21010 24100