RURAL WATER SUPPLY SYSTEMS
Graduate School of the Environment, Macquarie University, Sydney, Australia
Faculty of Engineering, University of Technology, Sydney, Australia
2. Need for Alternative Water Supply Systems
3. Water Sources
4. Rainwater-based Rural Water Supply Systems
5. Groundwater-based Water Supply Systems
6. Surface Water Supply Systems
7. Water Distribution Systems
Water supply for drinking and domestic uses is an essential basic requirement for households and communities. Unlike in large urban settlements, for small communities in rural and outback areas conventional methods of water sourcing, extraction, and supply are not cost effective. Especially so in the rural areas of developing countries, which need simple, alternative methods to satisfy their domestic water needs. Water supply to such rural communities can be sourced from rainwater, groundwater or spring/surface water. Through simple rainwater harvesting techniques, household as well as community needs for water in arid and semi-arid regions, where no other water sources are available or feasible, can be met. Groundwater is, by far, the most practicable choice for safe water supply. There is a wide range of low-cost groundwater extraction techniques available. In areas where groundwater is not available in adequate quantities, the next best available option for water supply is from surface water sources. Often, surface water sources are more contaminated than groundwater, which necessitates treatment of water and hence increases the costs of water supply projects. There are simple treatment methods available to provide minimal levels of treatment to produce safe water free of microbial contamination. Depending on the quality of raw water, a treatment method can be selected from a limited choice of low-cost treatment methods to achieve better water quality. Distribution of water from a central source to the community is also an important aspect of water supply. For rural communities, distribution can be done through stand posts and yard tap connections via a branched network of pipes.
Water is an indispensable natural resource for the survival and well being of human kind. It is also essential for production of food, energy that contributes to the economic and industrial development of a society. Safe and reliable supply of water is therefore essential for individual welfare and for community development. The first and foremost consequence of lack of safe water for community consumption is diseases. Infectious diseases, affected by the availability or the lack of protected water supply systems, may take the following forms:
Infections spread through water supplies (water-borne diseases such as typhoid, cholera, gastroenteritis).
Infections transmitted through living carriers found in water bodies (water-based diseases such as schistosomiasis, which is through an aquatic snail that burrows through skin).
Infections spread by insects that depend on water (water-related diseases such as malaria, yellow fever spread through mosquitoes).
Infections due to the lack of sufficient water for personal hygiene (water-washed diseases such as scabies, trachoma).
World Health Organization (WHO) estimates that as much as 80% of all diseases in the world is associated with water. Available evidences indicate that most of the health benefits from safe water are attainable at service levels of 30–40 liters per capita per day. Hence, the role of organized water supply in the prevention of water-borne diseases and in the promotion of public health can be well appreciated. It has been established that this role is best fulfilled when every house in a given community is connected to the public water supply system. But for most developing countries, this ideal is still unattainable due to financial and other constraints. According to the Human Development Report of United Nations Development Programme (UNDP), as of 1996, more than 31% of the population in developing countries are yet to have access to safe water and more than three-fourths of this population lives in the rural areas.
2. Need for Alternative Water Supply Systems
Traditionally, the people in rural areas have obtained water from unprotected ponds or tanks, wells, cisterns and sometimes streams and rivers. These water sources are frequented daily for collecting drinking and cooking water, washing clothes, bathing, livestock washing, etc. Mostly, these waters are unsafe for consumption due to contamination by fecal matters as well as by their heavy use. Consequently, the populations suffer from frequent epidemics. To supply potable water to all such communities by an ideal comprehensive water supply system that supplies water with a quality matching international standards, is not feasible. Water quality standards which have less bearing on health (such as hardness of water, or the presence of iron and manganese or chlorides normally included in any drinking water of quality standards) can possibly be relaxed unless this causes technical problems, and so long as the rural population finds the water acceptable. This will help to minimize financial constraints in providing safe drinking water. Considering the present situation of rural communities, where water from polluted sources is carried over long distances and used directly, any simple improvement in service and water quality could be expected to have a large beneficial impact on health. That is to say that what is needed is an effective short-term alternative to the ideal situation. Such an alternative to achieve an overall low-cost water supply scheme consists of:
an appropriate water source;
an appropriate water extraction method from the source;
low-cost water treatment systems, wherever required;
an appropriate water distribution system.
3. Water Sources
Basically, all sources of freshwater originate from rainfall, which is slightly acidic due to dissolution of carbon dioxide in the atmosphere. In the form of surface run-off, it will gather considerable amounts of organic and mineral matters, soil particles, microorganisms, etc. When the surface run-off infiltrates into subsoil it forms groundwater. As the groundwater level increases and rises above surface level due to varying land formations, it oozes out as springs. Perennial springs are the fountainheads of surface water bodies such as streams, rivers and lakes. The source of water has a major effect on water system design and hence costs. Water from different sources varies in quality and hence requires varying degrees of treatment. The process of choosing the most suitable source for water supply largely depends on the local conditions. A source of water supply can be identified at any of the above stages of water cycle, provided it can supply in sufficient quantities for most periods of the time in a year. Thus, water supply for rural communities can be organized with use of rainwater, groundwater, and, spring and surface water.
4. Rainwater based Rural Water Supply Systems
Rainwater can be considered as a source of water supply in regions where the pattern of rainfall permits its harvesting. Rainwater harvesting is possible in countries where rainfall is heavy, with long intervals with no rainfall. It can be a suitable source in arid and semi-arid areas where people live in scattered settlements and no other sources are available. Rainwater harvesting may serve well for household as well as community level supplies. It can also be used in conjunction with supply from other sources when their supplies are unpredictable in nature. Rainwater harvesting at household level is done by storage of rainwater through roof catchments and at community level by storage through ground catchments.
4.1. Roof Catchment and Storage
Rainwater with reasonable qualities can be collected using rooftop areas that can be stored to provide individual households in rural areas with adequate water supplies. By directing the rainfall on the roof areas to flow through simple collection gutter arrangements, water that would otherwise join surface run-off can be gainfully utilized. Roofs made of tiles, slates, corrugated iron/tin or asbestos sheets are more suitable. Thatched and lead sheet roofs are not suitable because of health hazards. A typical roof catchment and storage arrangement is shown in Figure 1.
Figure 1. Roof catchment and storage
The roof guttering should slope evenly towards a downpipe to avoid sagging and hence pooling of water that may become a breeding place for mosquitoes. It may be helpful to arrange to divert the first flush of water from a roof collection, as it will wash with it the accumulated dust and impurities such as bird droppings, dead leaves, etc. The roof and guttering should be cleaned regularly. A wire mesh placed over the top of the downpipe would prevent it from becoming clogged with washed-off materials.
The amount of rainwater that can be harvested will depend on the area of the roof. The storage tank, however, has to be of sufficient capacity to take care of the longest dry season in a normal year. To take care of exceptionally dry years, another 50% surplus storage can be added. The minimum basic drinking and domestic water requirement of a family of six persons is 40 liters per day. Thus, for an average dry season of 3 months, the water storage required will be 3 × 30 × 40 × 1.5 = 5400 L.
4.2. Ground Catchment and Storage
By appropriately preparing a piece of surface on ground, it can be used as a catchment for harvesting rainwater for small communities. Part of the rainfall will serve to wet the ground or get lost due to evaporation or infiltration. A considerable reduction in such losses can be attained by making the catchment surface smooth and impervious using clay, tiles, asphalt or plastic sheets. Ground catchment involves land alterations for contouring, clearance of rocks and vegetation, simple soil compaction, preparation of surface (tiling, etc.) to reduce infiltration, construction of ditches along contours and construction of storage tanks. Arrangements in a ground catchment for rainwater harvesting are shown in Figure 2.
Figure 2. Ground catchment and storage
Storage facilities for ground catchment rainwater harvesting system can be either above-ground or below-ground. Whichever the type of storage, it should be protected from contamination by providing an adequate enclosure that prevents entry of pollutants. Dark storage conditions using a tight cover is required to prevent algal growth and mosquito breeding. There is a wide choice of materials of construction of storage tanks. Small storage containers can be built up of clay, wood or water-proofed bamboo frameworks. While large storage tanks can be constructed using stone or brick masonry works, ferro-cement or reinforced cement concrete works better.
Ground catchments for community water supply need proper management and maintenance. It may be necessary to provide fencing or hedging to protect against damage and contamination. Trees and shrubs can be planted around catchment to limit the entry of wind blown materials and dust into the catchment area.
5. Groundwater-based Water Supply Systems
Among the various sources of supply, groundwater is by far the most practicable choice. Groundwater can be extracted either from perennial springs or from open wells/tube wells, as they normally yield safe drinking water in rural areas. Exceptions are areas of fissured limestone where groundwater may be contaminated by intrusion of surface run-off. In areas where groundwater is available at moderate depths, constructing a number of wells fitted with hand operated pumps is by far the cheapest means of providing a good water supply.
5.1. Extraction Devices
Extraction of water from wells can be done with use of simple technologies that can be manually operated. Traditionally, there were number of water lifting devices that were being used in various parts of the world. These include, rope and bucket devices, counterpoise lifts and the Archimedes screws. With simple modifications, these traditional methods can be made more efficient in operation and at the same time protecting the source from contamination. Some of the modified versions of these simple water-lifting technologies are:
sanitary rope and bucket system;
5.1.1 Sanitary Rope and Bucket System
The sanitary rope and bucket systems are designed for open dug wells and are simple to maintain. The design was developed by WHO and is shown in Figure 3. This simple arrangement apart from providing good service also protects the well from pollution. It contains a wooden roller fixed to the side walls of the well around which the rope winds. One end of the rope is permanently fixed with the roller and the bucket tied to the other end. The top end of the bucket is attached with a weight to enable it to tilt when it touches the water surface in the well. As the roller is rotated, the bucket with water raises up to the stop hook level where it is tilted due to the hook and water is emptied on to a trough and flows out through a small pipe fitted to the trough to aid collection (Figure 3).
Figure 3. Sanitary rope and bucket system
The arrangements are simple and can be changed to fit the local conditions. The cover for the well should be removable to facilitate cleaning and maintenance of the well and the rope and bucket mechanism.
5.1.2 Bucket Pumps
The schematic arrangement of a bucket pump to extract water from open well is shown in Figure 4. In this arrangement, small buckets are attached to an endless chain. The chain is rotated on sprockets using a handle. As the buckets move down and dip into water, they get filled. Further rotation brings to the top and to run around the sprocket, as they empty into a collection trough attached with a pipe. Depending on the local conditions and availability of materials, the buckets can be replaced with earthenware jars or wooden or metal boxes and the sprockets with bicycle wheels to run the endless chain.
Figure 4. Bucket pump
5.1.3. Chain Pumps
Chain pumps operate similar to bucket pumps. The difference is that rubber discs instead of buckets are attached to the endless chain that runs over the sprocket at the top (Figure 5). During its upward motion, the chain travels through a pipe immersed below the minimum water level of the well. As the chain is pulled upward, the rubber discs mechanically support water along the pipe to lift water up to the spout, from where it is drawn out thorough a small pipe arrangement.
Figure 5. Chain pump
Figure 6. Operation of a hand pump
5.1.4. Hand Pumps
Hand pumps are the most commonly used extraction devices to lift water from shallow wells as well as tube wells in rural areas. They may be of either reciprocating, positive displacement or plunger pump type. The hand pumps operate the same way as with drinking soda water through a straw or filling a syringe. The general principle of operation of hand pumps (Figure 6) is as follows:
As shown in A, the pump after priming is raised by pressing the operating handle downwards. The water seal above the plunger prevents air from passing through and creates a partial vacuum in the pump cylinder. The atmospheric pressure on the water in the well is greater than the pressure inside the cylinder thereby opening the check valve, and with the force of the air, water in the pipe moves upwards following the plunger. The space in the cylinder below the plunger is filled with air from the pipe.
The plunger stops at the top of the cylinder and the check valve closes under its own weight, thus trapping the air in the cylinder.
On the next downward movement of the plunger, the air trapped between the plunger and the check valve is compressed. When the pressure of this air exceeds the atmospheric pressure above the plunger and the weight of the plunger valve and that of the priming water, the air lifts open the plunger valve and escapes through the priming water as shown at B.
The next upward movement of the plunger, more air is drawn out of the pipe and the water rises further/higher, eventually flowing into the cylinder under the plunger as shown at C.
With cylinder and pipe full of water as at C, the check valve closes by gravity, trapping water in the cylinder.
On the next downward movement, the plunger reaches the bottom of the cylinder and the plunger valve closes, thus trapping water above the plunger as shown at D and E.
The next upward movement of the plunger lifts out the water as shown at F and at the same time more water forces into the cylinder through the check valve. Thereafter, for each successive movement, step F is repeated.
Some of the commonly used hand pumps are:
shallow well lift pump;
deep well lift pump;
reciprocating force pumps;
Shallow well lift pumps. They are the simplest of all hand pumps operating on the above described principle (Figure 7a). Because of their reliance on atmospheric pressure to push water up the suction pipe, use of shallow well pumps is limited to conditions where the water table is not more than 6.7 m from the plunger.
Figure 7a. Shallow well lift pump
Figure 7b. Deep well lift pump
Deep well lift pumps. Deep well lift pumps operate in the same manner as that of shallow well pumps. As the name indicates, they are more useful to lift water when the water table is deeper than 6.7 m from ground level. The main difference of these hand pumps from that of shallow well pumps is the location of the suction cylinder (Figure 7b). The cylinder is submerged in the water to avoid pressure losses due to priming. The selection of deep or shallow well pumps depends on the water level in the well below the surface and not the total depth of the well or tube wells.
Reciprocating force pumps. The force pumps are nothing but lift pumps (shallow or deep) that discharge water under pressure, by closing the top end of the pump. They are useful to pump water into reservoir and pressure tanks. They can be either the shallow well type where the plunger is located above the water surface or the deep well type where it is located below the water surface (Figures 8a,b). The force pumps usually have an air chamber to even out the discharge flow. On the upward stroke of the plunger, the air in the air chamber is compressed and is expanded during the downward stroke to maintain a flow at the discharge while the plunger goes down. The trap tube serves to trap air in the air chamber, preventing it from leaking out around the plunger rod.
Figure 8a. Shallow well pressure pump
Figure 8b. Deep well pressure pump
Diaphragm pumps. In a diaphragm pump, an elastic membrane (diaphragm) is lifted to draw water through the inlet valve. When the diaphragm is depressed, liquid is forced out through the outlet valve. The pedal pump and the Petro pump are some variations of this principle which have high potential for rural water supply systems.
Figure 9. Pedal pump
Pedal pumps. These are also known by the name ‘Hydro-Pompe Vergnet’ and it operates in a novel mode. As shown in Figure 9, this pump is operated by a foot pedal, at ground level that alternately stretches and contracts a flexible diaphragmatic hose located inside a rigid cylinder immersed in the well. The operation of this pump is as follows:
The rigid cylinder surrounding the diaphragm is primed and the foot pedal is pressed down into the cylinder forcing water in the cylinder into the diaphragmatic hose thereby expanding its volume.
The increased volume of the diaphragmatic cylinder increases the pressure of the water in the rigid cylinder surrounding it, resulting in the closure of the suction valve and opening of the discharge valve.
The water in the rigid cylinder is forced to the surface through the discharge valve. As the operator lifts his foot, relieving pressure within the pilot system, the diaphragmatic hose contacts to its initial position, reducing the pressure of water within the rigid cylinder.
The decrease in pressure in the rigid cylinder closes the discharge valve and opens the suction valve, refilling the rigid cylinder. As the operator presses the pedal again, the cycle is repeated.
The pilot cylinder and pipe including the diaphragmatic hose is filled with water from the surface at the time of installation. Except for a refilling valve, this system is completely closed, thereby reducing the potential of contamination of the well water.
Petro pumps. Petro pumps were developed in Sweden. In these pumps, the cylinder consists of an elastic rubber hose, reinforced by two layers of spirally wound brass coated steel and equipped with a stainless steel check valve (Figure 10). The discharge valve housing is attached to a string of 20 mm galvanized pipe serving both as the pump connecting rod and the drop pipe. The upper end of the pipe string with the delivery spout is connected to the pumping head. As the handle is pushed down, the pipe string is lifted, stretching the reinforced rubber hose thereby decreasing its volume. The increase in pressure within the hose opens the discharge valve, and water is forced through the pipe string to the surface. On the return stroke, the rubber hose expands to regain its original volume. The suction valve is opened at this stage allowing the entry of fresh water. The obvious advantage is that there is practically no mechanical friction during pumping reducing mechanical failures due to wear and tear. The use of the drop pipe as a pump rod results in considerable savings in piping costs.
Figure 10. Petro pump
6. Surface Water Supply Systems
There are instances when groundwater cannot be used as a source of water in rural communities due to one or more of the following reasons:
groundwater is not available in sufficient quantity;
groundwater is only available at great depths;
quality of the groundwater is not acceptable for direct consumption due to high mineral or organic matter content or color.
In such cases, surface water, either from springs, streams/rivers, lakes or ponds needs to be used as the source of water supply. Surface water invariably originates from rainfall and is a mixture of surface runoff and groundwater. Surface waters commonly have low mineral contents and hardness, high turbidity and bacterial count since they are more often than not exposed to serious pollution due to domestic and industrial wastes. A rural water supply system based on surface water sources will have the following components:
An appropriate water intake system.
A simple water treatment system.
6.1. Water Intake Systems
A water intake is a structure placed in a surface water source to extract water from surface water source for further use. They are normally located at locations where best quality of water is available. The water intake structures allows to withdraw water from a surface source at more than one level to cope with the variations in the depth of water or from the deepest point. They may also act as pretreatment systems in some cases. When placed near the water surface, the intake system may draw floating debris, algae and aquatic plants. When it is placed too close to the bottom, it may draw turbid water containing suspended matters. It is ideal that the intake point is about 0.3 to 0.45 m below the water level. Intake systems for extracting water from small streams will often need a small barrage to provide sufficient depth of water above intake pipe. Some of the simple water intake structures for a rural water supply system are:
fixed level intake;
floating level intake;
Figure 11a. Fixed level intake
Figure 11b. Floating level intake
Figure 11c. Infiltration gallery
6.1.1 Fixed Level Intake
This is the simplest of water intake systems as shown in Figure 11a. The location of the intake point is selected and the bed of the water body closely around this point is prepared by spreading a thick layer (0.45 to 0.6 m) of gravel. The intake pipe with its mouth covered with a screen is placed through this bed protruding just above this bed. A wooden crib is placed around the bed and the pipe, in the case of rivers or streams, to protect the intake system from occasional floods or high velocity flows during rain.
6.1.2 Floating Level intake
The floating level intake consists of a flexible pipe attached to a rigid conduit by means of a flexible joint (Figure 11b). The other end of the flexible pipe has perforations to let the water into the pipe and is attached to a light-weight plastic or rubber ball that keeps the flexible pipe floating. In place of balls, well-sealed empty oil drums can also be used as a float. The floating mechanism is fixed on a suitable frame to prevent it from dislocation. Such an arrangement is suitable for sources where the water level fluctuates widely during different seasons.
6.1.3. Infiltration Galleries
Infiltration galleries are open-jointed pipes running just beneath the bed of river, stream or lake and encased by a layer of fine sand and gravel (Figure 11c). The gravel and fine sand medium act as a filtration unit as the water trickles through them towards the open joints of the collection pipes. The collection pipes slope towards a collection well from where water can be pumped out for further treatment or distribution.
6.2. Water Treatment Systems
6.2.1. Slow sand Filtration
The major problem in using surface water as the source of water supply in tropical developing countries is the turbidity. Suspended and colloidal particles and silt generally cause turbidity in water. If the turbidity is less than 1 NTU (Nephlometric Turbidity Unit) water can be directly distributed, and if bacterial contamination is suspected disinfection by chlorination could be the only treatment required for water before distribution. For higher turbidity levels of raw water, slow-sand filtration has often been the choice for treatment at rural, small-scale level.
Filtration is the purification process in which raw water is passed through a porous medium to remove undesirable physical, chemical and bacteriological characteristics. During such passage, suspended and colloidal matters that cause turbidity are removed due to the straining/screening action of the porous medium. Bacteria and other microorganisms also are reduced by this action of the medium. Chemical constituents undergo favorable changes that result in improved water quality. Finely graded sand is predominantly used as the medium of filtration in water treatment. In slow sand filtration, water is filtered at the rate of 0.1 to 0.3 m3m–2 of the filtration area per hour.
The advantages of slow sand filtration are:
It is simple, robust and reliable.
It is relatively labor intensive with low capital cost.
It requires little of any foreign material to be imported or skill and is within the capabilities of local communities to implement, operate and maintain.
It is able to bring a simultaneous improvement to the raw water with respect to color, turbidity, hardness and pathogenic organisms
The major problem in applying slow sand filtration is the rapid clogging of pores of the filter media. Experience of tropical countries operating slow sand filters shows that when the average turbidity of raw water exceeds 20 NTU, it requires cleaning so frequently that it can not produce treated water with reliable qualities in adequate quantities. For such cases, some form of pretreatment of raw water will help to achieve greater reliability of water supply.
Some of the simple and appropriate pretreatment systems are as follows:
River bed filtration or infiltration galleries. This has been discussed earlier under water intake systems
Storage basins. Storage basins help to remove suspended matters as also pathogens from raw water before treatment. These are simple water-retaining structures (Figure 12a) constructed of earthen embankments with retention times in the range of a few weeks to few months. In order to avoid loss of water due t seepage they may be lined with stabilized soil or masonry. In addition to pretreatment, the storage basins improve the reliability of water supply during drought periods.
Sedimentation basins. Sedimentation basins also function in the same way as the storage basins albeit shorter retention times (in the order of few hours to few days). The most common configuration is a continuously operated rectangular box made of concrete or masonry (Figure 12b).
Roughing filters. These filters use filter media such as coconut fibers, burnt rice husk, coarse gravel, pea gravel, etc., and are operated at high filtration rates to produce effluent with qualities that are satisfactory for further slow sand filtration.
Figure 12a. Storage basin
Figure 12b. Sedimentation basin
The selection of pretreatment method depends on the turbidity and bacteriological quality of raw water.
6.2.2. Alternative Filtration Technologies
There are some alternatives to slow sand filtration that have been developed for water treatment in small rural communities. Series filtration systems and dual media filters are among the prominent among these alternatives.
Series filtration systems. Series filtration systems consist of two stages of filtration. In the first stage, filter media made up of shredded coconut husks is used to remove the bulk of suspended matter from raw water. A bed of burnt rice husk as a medium in the second stage of filtration "polishes" the already rough-treated water to achieve a desirable quality of water. As both types of media are mostly locally available and often discarded materials in rural communities of tropical countries, this system works out to be very cheap. There is no need for cleaning of the media, as fresh media at little or no cost can replace them. Researches have revealed that burnt rice husks as a filter medium show a significant absorption capability for taste, odor and color removal when compared to slow sand filters.
Dual media filter. As the name implies, a dual media filter consists of two filtration beds made-up of different media. Researches have shown that a dual media filter consisting of a coconut fiber bed over burnt rice husk could run for two to three months producing water of excellent clarity with raw water turbidity of about 100 NTU at a filtration rate of 0.2 m3m–2. A drawback with this kind of filters is the inconvenience in cleaning the beds which requires their removal from the system. Discarding the used-up media and replacing with new filter media is a better way to overcome this difficulty.
6.2.3. Selection of Treatment Systems
Table 1 provides general guidelines for selection of treatment system for rural water supply.
Table 1. Guideline for selection of treatment system in rural areas
7. Water Distribution Systems
Distribution of water to the ultimate consumers namely the households, is as important as extraction and treatment of water. In cases of groundwater-based water supply systems for rural areas, mostly the location of wells and hand pumps become the distribution point. However, a distribution system will be necessary in many cases of surface-water based systems, particularly when the extraction point is located farther from the area where the population intended to be served lives. Moreover, villages will eventually need a distribution system that serves people at a closer location to households. The type of distribution system that can be adopted in a rural area depends on the level of service that has been planned for that area. This in turn depends on the social, financial and political character of the community.
7.1. Methods of Water Transportation
Water can be transported through the distribution systems to the consumer end through any of the following methods:
thorough gravity flow;
through direct pumping;
through pumping for elevated storage and gravity flow.
Water distribution through gravity flow is possible when the water source or the extraction point is located at sufficiently higher elevation to the area being served. It is the ideal method of transporting water, as it will not require pumps and energy for their operation. However, except hilly areas or areas located close to hills, occasions where water can be distributed by gravity are very rare.
Where it is not possible to transport water by gravity, it can be done using pumps. This is the least desirable method as any breakdown of pump or failure of power supply will completely disrupt the water supply. Especially so in the rural areas of developing countries where a power supply is highly unpredictable.
An appropriate method to overcome such difficulties is pumping water to an elevated storage tanks and distributing through gravity.
7.2. Types of Distribution Networks
Water can be distributed through either a branched network or a looped network (Figures 13a,b). The looped network is more efficient than a branched network, but involves complicated design and construction. This is also not suitable for rural areas where the dwellings are far apart and hence will require long pipings and large numbers of fittings. A low cost water distribution will not be possible with a looped network unless the community is densely or closely populated. The branched network is less complicated to design and construct and hence more suitable for small communities and rural areas. This system has a disadvantage that when the supply is terminated at one point for repairs or maintenance, the entire downstream population will lose their supply.
Figure 13a. Branched network system
Figure 13b. Looped network system
7.3. Types of Consumer Outlets
The distributed water is ultimately made available to the consumer through consumer outlets or connections. The type of outlet depends on the planned level of service and the financial viability of the consumers.
Distribution systems that are appropriate for rural areas of developing countries are:
yard tap connections.
It is common that water distribution in small towns and villages of developing countries comprise both the above systems.
7.3.1. Public Standposts
In urban areas of developing countries, the urban squatter settlements are generally provided with water through public standposts as an intermediate step towards the ideal of direct house connections. In rural areas, this is the chief means for the majority of the population in rural areas. The planning of public standposts should consider the following aspects:
Locations of standposts
Number and discharge capacities
Height of collection platform
Drainage around the standpost
Various types of standposts are shown in Figures 14a,b,c are:
Multiple tap standposts
Figure 14a. A simple standpipe
Figure 14b. A multiple tap standpost
Figure 14c. Cistern type standposts
Figure 15. Yard tap connection
7.3.2. Yard Tap Connections
Figure 15 shows a yard tap connection with water meter. In this type of outlet, a service connection with a tap is provided to a household from the supply main. This type of connection does not require any in-house plumbing.
: Mechanical arrangements or devices used to extract groundwater from open wells and tube wells.
: Planning and arranging to collect rainwater as a source for domestic water uses.
Water intake structures
: Civil engineering structures constructed to extract water from surface water sources.
Water distribution systems
: Pipe network arrangements to transport water from source or water treatment plants to consumers/households.
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IRC (1978). Public stand posts for developing countries. Bulletin Series #11. WHO International Reference Center for Community Water Supply, The Hague, Netherlands. [Proceedings of an international expert meeting held in Accra, Ghana that describes technological, economic, socio-cultural and management aspects of public stand posts.]
IRC (1979). Public Stand Post Water Supplies—Design Manual. WHO International Reference Center for Community Water Supply, The Hague, Netherlands. [Details of planning and design aspects of water supplies using public stand posts.]
IRC (1981). Small community water supplies—echnology of small water supply systems in developing countries. International Reference Center for Community Water Supply and Sanitation, The Hague, Netherlands. [Comprehensive document detailing all technological aspects of small water supply systems for developing countries]
Letterman R. D. (1999). Water Quality and Treatment: A Handbook of Community Water Supplies, 5th edition, McGraw-Hill Inc., Washington DC. [Comprehensive overview of drinking water quality standards, public health issues and detailed information on different water treatment processes.
Schulz C. R., and Okun D. A. (1984) Surface water treatment for small communities in developing countries. Wiley Interscience, New York [An excellent overview on simple water treatment options in community water supplies. Also gives detailed design of water treatment plants suitable for Africa, Asia and South America, with a number of case studies.]
Thanh N. C., and Hettiaratchi J. P. A. (1982). Surface Water Filtration for Rural Areas: Guidelines for Design, Construction, and Maintenance. Environmental Sanitation Information Center, Bangkok, Thailand. [Provides design, construction and operation details of simple water filtration systems for rural areas of developing countries.]
Vigneswaran S., Tam D. M., and Visvanathan C. (1983). Water filtration technologies for developing countries. Environmental Sanitation Review #12. Environmental Sanitation Information Center, Bangkok, Thailand. [Comprehensive overview of history and development of water filtration technologies and details of appropriate low-cost filtration technologies for developing countries.]
M. Sundaravadivel is an Environmental Engineer with the Central Pollution Control Board, Ministry of Environment and Forests, Government of India. He holds a Bachelors Degree in Civil Engineering and a Masters Degree in Environmental Engineering. He has been working in the field of environmental management and industrial pollution control since 1989, particularly in the area of environmental audit, waste minimization and cleaner production in agro-based industries. He has also been an engineering consultant for planning, design and development of wastewater collection and treatment systems for many large cities of India. Currently, he is engaged in research on ‘environmental economic approaches for liquid and solid waste management in small and medium towns of developing countries’ at the Graduate School of the Environment, Macquarie University, Sydney, Australia.
S. Vigneswaran is currently a Professor and Head of Environmental Engineering Group in Faculty of Engineering, University of Technology, Sydney, Australia. He has been working on water and wastewater research since 1976. He has published over 175 technical papers and authored two books (both through CRC press, USA). He has established research links with the leading laboratories in France, Korea, Thailand and the USA. Also, he has been involved in number of consulting activities in this field in Australia, Indonesia, France, Korea and Thailand through various national and international agencies. Presently, Dr. Vigneswaran is coordinating the university key research strengths on "water and waste management in small communities", one of the six key research centers funded by the university on competitive basis. His research in solid liquid separation processes in water and wastewater treatment namely filtration, adsorption is recognized internationally and widely referred.