Community Water Supply PDF - Textbook

CHAPTER TWO COMMUNITY WATER SUPPLY  Out line Introduction Occurrences and sources of water Public health importance of water Impurities of water Water and disease Protection of water sources Water treatment Water tasting  Introducti...

CHAPTER TWO COMMUNITY WATER SUPPLY  Out line Introduction Occurrences and sources of water Public health importance of water Impurities of water Water and disease Protection of water sources Water treatment Water tasting  Introduction There is an old saying which states that “Water is life “ “Water is guilty unless proved innocent” The quality & quantity of water provided for a community is relative to the Socio-economic status of the country as a whole  Introduction cont…. According to WHO survey 80% of all illnesses in developing countries are water-associated. The use of unsafe water causes high prevalence of diarrheal diseases among children resulting in high infant and child mortality rates.  Introduction cont…. The provision of safe and adequate water supply programs requires integrated efforts of different concerned sectors including the community to be benefited for its effective achievements.  Introduction cont…. In Ethiopia the problems related to water supply are attributed mainly to lack of maintenance of the previously constructed systems, lack of community involvement when the earlier water systems were built, lack of spare parts and local maintenance capabilities, etc.  Introduction cont.…. According to the health indicators of MOH, the safe water coverage in 1992 E.C. for urban areas was 83.5% and 24.7% in the rural parts of the country where the majority of the population is living. Basic service parameters of a drinking-water supply should normally be taken into consideration: Quality: whether the supply has regularly verified water quality Quantity (service level): the proportion of the population with access to different levels of drinking-water supply Accessibility: the percentage of the population that has reasonable access to an improved drinking-water supply; Affordability: the tariff paid by domestic consumers; Continuity: the percentage of the time during which drinking- water is available (daily, weekly and seasonally) 2.1. Occurrence and Source of water Global Occurrence of water Water is located in all regions of the earth. The problem is that the distribution, quality, quantity and mode of occurrence are highly variable from one locality to another. Over 72% of the earths surface is covered by water  Global occurrence cont.…. Out of the 72% of the earth’s surface water, 97.2% is in the ocean, which is unfit for human consumption, as it is too salty to be used for drinking and irrigation without desalination. 2% of the remaining water lies frozen in glaciers and in icecaps, and is mostly unreachable. The tiny usable portion is about 0.8% of the total, which is neither evenly distributed nor properly used.  2.2. Sources of Water Improved drinking-water sources: – piped water into dwelling, yard or plot – public tap or standpipe – tubewell or borehole – protected dug well – protected spring – rainwater collection Unimproved drinking-water sources: – unprotected dug well – unprotected spring – cart with small tank or drum provided by water vendor – tanker truck provision of water – surface water (river, dam, lake, pond, stream, canal, irrigation channel) – bottled water  2.2. Sources of Water…. The different sources of water can be classified as; 1. Ground water: the total precipitation which has percolated downward into the porous space in the soil and rock where it remains, or from which it finds its way out to the surface. Groundwater is by far the most practical and safe in nature. Examples of ground water are springs and wells  Advantages of groundwater: Disadvantages of groundwater It is comparatively likely to be It needs pumping unless it free from disease causing micro- comes from a spring organism. It may contain excess amounts It can be used without further of dissolved minerals. treatment if properly protected and treated immediately after the It is poor in oxygen content. completion of construction work on the well or other source where groundwater is available. It is not exposed for evaporation and is used as natural storage in underground. It is most practical and economical to obtain and distribute. Groundwater can be found near a family or a community.  Sources of Water Cont.….. 2. Surface Water: Surface water is non- uniformly distributed over the earth’s surface. As the rain reaches the surface of the earth, it becomes surface water or runoff. Surface water includes rivers, streams, lakes, ponds etc.  Sources of Water Cont.….. 3. Rain Water: In regions where rainfall is abundant and frequent, rainwater can be a good source of water supply for individual families and for small communities. Advantages of Rainwater: It is a reliable source even if it rains once or twice a year only. It is cheap and a safe means of water supply that may not need pipes or pumps and is available at the doorstep.  Sources of Water Cont.….. Since the cistern will be in a closed container, it will not permit spreading of diseases which are often found in an unprotected source such as rivers or ponds. Women and children, who are normally water carriers in Ethiopia and other African countries, will be relieved of the burden of walking long distances to fetch inadequate supply. It is a system that can be used even in arid and semi- arid areas. Since rainwater is soft, little soap is needed for laundry purposes. It is the purest of all other sources.  Sources of Water Cont.….. 4. Ocean: Ocean water is unfit for human consumption even though it comprises the largest portion of water on the earth's surface To make the ocean water fit for domestic purposes; it must pass through a process known as desalination (a process of removal of salt from water).  2.3. Public Health importance of water Physiological needs: 70% of our body by weight; about 2.0-2.5 litres per day needs; survival with out water very hard; most food contains water: milk about 90%, fish about 80%; Water intake balance: 2-2.5L intake (1.5L drink, 0.6- 1. 0L food, 0.3-0.4L body oxidation); equal loss (1.5L urine, 0.4-0.6L sweat, 0.35-0.4L breathing, 0.1-0.14L faeces; generally half of intake lost by skin and lung, and half of it by urine and faeces); Domestic use: cleaning, washing, swimming, livestock watering  Public Health importance cont… Recreational purposes: swimming, boating, fishing, skiing, (lakes Langano, Ziqay, etc.) Other uses: agriculture, transportation, power production, industrial use, etc. Lack of safe adequate water is still a major problem globally and nationally: – Globally: 23% urban and 64% of rural population in developing countries lack safe water; – More than 80% of diseases in developing countries is due to lack of safe water supply and sanitation; dysentery, typhoid fever, diarrhoeal diseases, helminthiasis, skin and eye infections are the leading causes of morbidity.  Public Health importance cont…. Country status (Ethiopia): Only 26% of the total population gets safe water (83% urban; 20% rural) with the over all mean 50% the bottles should be exposed for 2 consecutive days If the temperature exceeds 50°C 1 hour exposure is sufficient 2. Filtration a. Bio-sand Filter How does it work? A bio-sand filter is a concrete or plastic box that is filled with layers of sand and gravel. Water is into the top of the filter and collected in a safe storage container Pathogens and turbidity are removed by physical and biological processes in the filter sand b. KanchanTM Arsenic Filter How does it work? Adaptation of the biosand filter Layer of rusty nails, which remove the arsenic Brick chips are used on top of the nails to keep them from moving around Pathogens and turbidity are removed by physical and biological processes in the filter sand c. Life-Straw How does it work? Membrane filter – very small holes (20 nan- ometers) in the blue cartridge Pathogens are removed by physical processes Fill the bucket with water Drink from the light blue tap using a clean cup d. Ceramic Candle Filter How does it work? Hollow cylinders made from clay mixed with a combustible material like sawdust, rice husks or coffee husks. Colloidal silver is sometimes used to help with pathogen removal. One or more candles are attached into the bottom of a container. Water is poured into the container and flows through the candle, and is collected in another container that has a tap at the bottom. This system also provides safe storage until the water is used. Household water treatment cont… 3. Combination of Technologies Disinfectant powder Coagulant and disinfectant How does it work? - Bishan Gari - Water Pur : ferric sulfate (a flocculants) and calcium hypochlorite (a disinfectant).  2.7.2. Large Scale Water treatment (Municipal water Treatment) Steps in Municipal Water Treatment 2.1. Ground water treatment Aeration Disinfection Storage distribution 2.2.Surface water treatment Screening  Coagulation Mixing  Sedimentation filtration  disinfection  Storage distribution Large Scale Water treatment cont…….  Aeration- is the addition of air (oxygen) to the water. -to reduce substances which cause objectionable color, odor and taste in water.  Sedimentation or Storage - is the process in which the water is made quiescent (rest) for a given period of time so that suspended heavy (settle able) particles are permitted to be deposited or settled to the bottom of the sedimentation basin or tank. Large Scale Water treatment cont……. Flocculation or Coagulation:- is the process of removing turbidities, Color, bacteria through the aid of coagulant. - Coagulant:- is chemicals applied to water in order to accelerate the process of natural (plain) sedimentation. - For a very minute unsettle able particles. -Coagulants most commonly used are; Aluminum sulphate (Alum), ferrous sulphate. Large Scale Water treatment cont…….  Filtration- is one of the most important & oldest practices of water purification method. -Types of sand filters;-  Slow sand filter  Rapid sand filter  Pressure filter -remove from about 97% to 99% of bacteria compared to the original number in the raw water. Large Scale Water treatment cont……. Disinfections – for destruction or at least complete inactivation of harmful microorganisms present in the water. -It is carried out using chemical or physical means. -Physical disinfections :- -Boiling -UV light Large Scale Water treatment cont……. Disinfections – for destruction or at least complete inactivation of harmful microorganisms present in the water. -It is carried out using chemical or physical means. -Physical disinfections :- -Boiling -UV light Large Scale Water treatment cont……. UV light -effective method for clear H2O -Does not have residual effect -Its effectiveness reduced for water containing NH3, SO4, Fe Large Scale Water treatment cont……. Chemical disinfection:- -A good chemical disinfectant possesses the following important Characteristics Quick & effective in killing microorganisms present in H2O Readily Soluble in H2O Capable of providing a residue Not imparting test, odor, and color to water Not toxic to human & animal life Easy to detect and measure in water Easy to handle, transport, apply & control Readily available at moderate cost Large Scale Water treatment cont……. -Chemicals used for disinfectant are :- Chlorine Chlorine compounds Iodine- high dose is required, not effective for turbid water. Ozone- eliminate compounds that give taste & color to water Potassium permanganate- effective against vibrio cholera. Large Scale Water treatment cont……. Chlorination -The most common forms of Chlorine that is readily available in rural areas & small communities are :- Calcium hypo chlorite powder (Ca (OCl2) Sodium hypo chlorite solution (NaOCl)= barachina High-test hypo chlorite (HTH 70%) -It reacts rapidly with H2s, Mn, Fe & No3.(reducing compounds) i.e. when reacts with chlorine results no disinfecting effect Large Scale Water treatment cont……. Chlorine demand :- the amount of chlorine used by reducing compounds & organic matter. Residual chlorine :- the amount of chlorine left over in the water after the water is completely disinfected. -exists in water as hypochlorous acid (HOCl) or hypochlorite ion (OCl) -is measured by orthotoilidine test (OT). Large Scale Water treatment cont……. De-chlorination:-removing of excess amount of chlorine in water. Methods of de-chlorination -Sodium thiosulphate -Granular activated carbon -Aeration -Boiling  Water Testing The important parameters of water quality from different water sources are :- 1.Physical Parameters 2.Chemical characteristics of water 3. Microbiological characteristics of water quality  Water Testing-----cont’d 1.Physical Parameters – Turbidity- muddy appearance due to flood, inorganic substances or wash water elements – Colour– due to the presence of colour organic matter. Metals (Fe & Mg), industrial wastes. – Taste & smell (odour)- due to the presence of organic substances, increased biological activity, industrial pollution. – PH- due to industrial wastes, inorganic substances  Water Testing-----cont’d 2.Chemical characteristics of water Hardness - the presence of Ca & Mg content in water. There are two types of hardness, these are:- ◦ Temporary hardness - presence at bicarbonates of Ca &Mg -Removed by boiling - Permanent hardness - presence of chlorides and sulphates of Ca &Mg. -Not removed by boiling rather by adding sodium carbonate  Water Testing-----cont’d  Water which contains :- - 0-75 mg/l of dissolved salt ------soft -75-150ml/l of dissolved salt ------moderately hard -150-300mg/l of dissolved salt------hard -300mg/l of dissolved salt ------- very hard  Causes of hardness - Soil formation of a locality - Contact of water with hardness causing minerals  Water Testing-----cont’d Disadvantages of hard water -Great wastage of soap -Adverse effect on cooking -Decrease the life of fabrics -Not good for the skin (hands) -Not suitable for industrial process -May cause digestive disorder -May block pipes  Water Testing-----cont’d Fluoride:- -Dental or skeletal fluorisis:-Excess fluoride -Dental caries, a weakening of the teeth:-Lack of fluoride Nitrate:- Excess linked to methaemaglobinamenia in infants (‘blue baby’ syndrome )  Water Testing-----cont’d 3. Microbiological characteristics of water quality the content of bacteria & viruses the most important parameter of drinking water quality Indicative of fecal contamination:- It is not practicable to test the water for all organisms that might possibly contain. Instead, the water is examined for specific type of organism, which originate in large number from human & animal waste.  Water Testing-----cont’d  Ideally, drinking water should not contain any Pathogenic organisms & should also be free from bacteria indicative of pollution with faces.  These indicators of fecal Pollution are :- 1.Coli form organisms (total) coli forms) -Originates from man and animal faces & soil 2. Faecal Coli form organisms (thermo tolerant) -Originate from human faces, commonly known as E. coli THE END