Technological Options of Rural Water Supply



If the PSF has been properly constructed, the only items likely to need replacement and repair are the movable parts, i.e. filter media, the lid etc. The repair of the lid should be within the competence of any local carpenter or mason. The filter media may be replaced as and when needed. The pump handle fulcrum pins should be greased regularly. This will prevent the handle from wearing out fast and make pumping easy.

  • After the filter media is replaced, open the washout pipe of the filter chamber to drain accumulated water and then close the washout.
  • Place bricks on top of the filter media under the dynamic roughing filter chamber to reduce disturbance and scouring of the filter media under impact of water.
  • Pump water until the filtered water enter the storage chamber.
  • The initial filtered water should be drained out through the washout pipe of the storage chamber.
  • Close the washout pipe of the storage chamber. The water level in the storage chamber will raise to the level of the outlet pipe.
  • Collect water from the storage chamber by opening the tap.

 Since these are small units, the committee involvement in operation & maintenance is absolutely essential to keep the system operational. The PSF is an effective technology for removing bacteria from pond water where turbidity level is less than 90 NTU.

Cleaning- Outside wall of PSF, platform, drain and surrounding places of PSF should be cleaned up at least twice a month and waste water should dispose properly using in the kitchen garden, any other agriculture field or making soak pit for recharging.


Rainwater harvesting is the accumulation and deposition of rainwater for reuse on-site, rather than allowing it to run off. Rainwater can be collected from rivers or roofs, and in many places the water collected is redirected to a deep pit or reservoir with percolation, or collected from dew or fog with nets or other tools. Its uses include water for gardens, livestock, irrigation, domestic use with proper treatment, and indoor heating for houses etc. The harvested water can also be used as drinking water, longer-term storage and for other purposes such as groundwater recharge.

System setup:

Rainwater harvesting systems can be installed with minimal skills. The system should be sized to meet the water demand throughout the dry season since it must be big enough to support daily water consumption. Specifically, the rainfall capturing area such as a building roof must be large enough to maintain adequate flow. The water storage tank size should be large enough to contain the captured water.

In shallow Tubewell technology, hand pumps are operated in a suction mode. A suction pump draws water from a shallow depth by creasing a vacuum in the suction pipe. The suction hand pump can practically extract water from a depth of 7.5m from ground level.Deep-set Hand pump:Shallow tube wells operated under the suction mode are not able to withdraw water in low water tyable areas. The low water table are is increasing with the excessive withdrawal of groundwater for different purpose.Water can be abstracted from a depth beyond the suction limit using intermediate technology. Conventional Deep-set hand pumps can abstract water from depth of 30 m from the ground level, depending on the technological advancement of the hand pump. Usually conventional Deep-set hand pump are designed to draw water from 20m from ground level in the country.  

DUG WELL / RING WELL                

In the Chittagong hilly areas, Sylhet & northern parts of Bangladesh, construction of hand pump tube wells is not always possible due to adverse hydro geological and stony soil conditions. Construction of protected dug wells / ring well can be good option for water supply in these areas. Ring well provides water free from iron and arsenic. Hence dug wells are a potential source of ground water in acute arsenic and iron problems areas.
TARA HANDPUMP TUBE WELL                   

In Bangladesh, the groundwater table during monsoon in most places remains within the suction limit. But due to extensive use of groundwater for irrigation, the groundwater table is falling and in the dry season it goes beyond the suction limit in many part of the country.  As a result Shallow Tube well is inoperable in dry season. To overcome the problems Conventional Deep-set Hand Pump was developed and used. But due to cumbersome maintenance problem and corrosion of GI and MS connecting rod under research and development activities the Tara hand pump has been developed in Bangladesh to tap water from up to 15m below ground surface. The Tara hand pump is a force mode pump in which the piston of the pump operates below the static water level to eliminate the limitation of suction mode hand pumps to operate in the low water table areas. The cylinder of the pump is set at 18m below the ground surface and a PVC hollow pump rod set vertically operates the piston. The pump is operated by a person holding the handle fitted at the top end of the pump rod and pulling and pushing the pump rod vertically. Due to leakage in the PVC column pipe, the tube well become permanently chocked within shorter time frame. To overcome the problem, extractable Tara Hand Pumps have been introduced. 


SHALLOW SHROUDED TUBEWELL (SST) :In the high salinity coastal areas it has been found that fresh water is available in small pockets of shallow aquifers composed of fine sand at 15 to 20 m depth. This is due to accumulation of rainwater in the upper aquifer. However, the particle size of soil and the thickness of the aquifer are not suitable for installing a normal tubewell. To get water through these very fine-grained aquifers, an artificial sand packing is required around the screen of the tubewell. This artificial sand packing, called shrouding, increase the yield of the tubewell and prevents entry of fine sand into the screen. The 15 to 20 m deep tubewells, installed as above are called Shallow shrouded tubewell (SST). The SSTs are fitted with NO. 6 handpumps operating under suction mode.

VERY SHALLOW SHROUDED TUBEWELL (VSST) :This is a low-cost hand pump tube well about 8m in depth with a short strainer depending on the aquifer thickness and shrouded with coarse sand. The VSST is designed to collect water from very shallow aquifers formed by displacement of saline water by a continuous flow of accumulated fresh water. The lenses of fresh water formed by this process are found beneath old ponds in coastal areas. In many places, ponds dry up but fresh water in shallow aquifers remains beneath the pond. Immobile preserved aquifers are also found at shallow depths at various locations in the coastal area. A VSST is a convenient method for withdrawal of fresh water in limited quantities. In many places, the water produced by VSSTs becomes saline due to rising of water caused by over-pumping. Installation of low capacity pumps may prevent over exploitation of shallow aquifers. The system is considered suitable for drinking water supply for small settlements where water demand is low. A VSST is not different from an SST expect in the depth of well.

                                     RO PLANT / DESALINATION PLANT                                         
Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential, a thermodynamic parameter. Reverse osmosis can remove many types of molecules and ions from solutions, including bacteria, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The movement of a pure solvent is driven to reduce the free energy of the system by equalizing solute concentrations on each side of a membrane, generating osmotic pressure. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications. However, key differences are found between reverse osmosis and filtration. The predominant removal mechanism in membrane filtration is straining, or size exclusion, so the process can theoretically achieve perfect exclusion of particles regardless of operational parameters such as influent pressure and concentration. Moreover, reverse osmosis involves a diffusive mechanism, so that separation efficiency is dependent on solute concentration, pressure, and water flux rate.[1] Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.

                                          SURFACE WATER TREATMENT PLANT                                                    

The amount and type of treatment applied by a public water system varies with the source type and quality. Many ground water systems can satisfy all federal requirements without applying any treatment, while others need to add chlorine or additional treatment. Country is developing a ground water rule that will specify the appropriate use of disinfection and will address other components of ground water systems to assure public health protection. Because surface water systems are exposed to direct wet weather runoff and to the atmosphere and are therefore more easily contaminated, regulations require that these systems treat their water. Disinfection of drinking water is one of the major public health advances of the 20th century. However, the disinfectants themselves can react with naturally occurring materials in the water to form unintended byproducts which may pose health risks. A major challenge for water suppliers is balancing the risks from microbial pathogens and disinfection by products The Stage 1 Disinfectants and Disinfection By products Rule and the Interim Enhanced Surface Water Treatment Rule together address these risks..The most commonly used processes include filtration, flocculation and sedimentation, and disinfection for surface water. Some treatment trains also include on exchange and adsorption. Water utilities select a combination of treatment processes most appropriate to treat the contaminants found in the raw water used by the system.















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