One of the activity implemented in Koyalmedu village, Vanur block under CFLI project
(2008 to 2009)
C.5 Drinking water supply:
The drinking water supply for the village used to come from a bore well located at a distance of 1 km from the village. During the summer time the Total Dissolved Solids (TDS) goes up to 2000. The women of the Koyalmedu village requested that the bore well water be tested and suitable arrangements be made to treat the bore well water. A sample of the bore well water was taken and tested at the EMS lab, Auroville. The result of the tested water is given below in table 7:
Table 7:
Sl.NO. / Parameters / Results / Drinking Water Standard1 / pH / 6.6 / 6.5 – 8.5
2 / TDS / 1810 / 500
3 / Total Hardness / 750 / 300
4 / Calcium / 120 / 75
5 / Magnesium / 112 / 30
6 / Chlorides / 750 / 250
The EMS lab, Auroville, stated that the total hardness and magnesium concentration of the water is higher than the permissible limit and that prolonged usage may lead to cardiac- and diuretic problems since the water in its present form will act as laxative and also will form scales on the pipes of the distribution system. They recommend to implement reverse osmosis system to avoid the above mentioned problems.
M/s. Water Technologies, Coimbatore were approached for installing a reverse osmosis unit suited to the village which will reduce the total dissolved solids to 50ppm. Now the unit has been installed and handed over to WUA for operation and maintenance. A brief description of the RO equipment installed at the village is given in Appendix 1.Water samples of the filtered water, rejected water and the well water from the over head tank were taken and tested in the wet chemistry laboratory of the Centre for Water Resources, AnnaUniversity, Chennai-25. The results are presented in the table 8 below:
Table 8
Parameter / Overhead tank Water / RO Reject / RO Treatedmg/litre
pH / 7.7 / 0.83 / 6.31
EC(us/cm) / 10450 / 12125 / 279
TDS(mg/l) / 6895 / 7928 / 158
CarbonateasCo3 / 0 / 0 / 0
Bicarbonate / 1348 / 1856 / 34
Calcium / 116 / 148 / 4
Magnesium / 89 / 103 / 2
Sulphate / 652 / 786 / 6
Chloride / 1095 / 1145 / 25
Sodium / 3596 / 4128 / 56
Potassium / 38 / 44 / 3.5
For the installation of RO system, a room for housing the system and for storing the treated water was constructed.
The system will be maintained by the WUA as stated above. It was decided in the meeting that the community will be charged Re.1/pot (20 liters) and the money will be collected at the end of each month. A separate account will be maintained for the collected water which will be used for repair and maintenance of the RO system. It was also decided that a small token amount will be given as service charge to the local person who is going to manage this RO system and who has been given adequate training to operate the system. Permission for installing the RO system was obtained from CFLI funding agency (before taking up the work).
Appendix 1:Functions of Drinking Water Plant
Reverse Osmosis: Reverse Osmosis is a process of water purification using special membranes to make water safe from bacteria and chemicals. The RO system works by a simple process of passing water through a module made of membranes. Water free from all impurities and toxic chemicals is collected as permeates. The toxic chemicals, germs and salts are flushed out to give you safe and sweet water.
Stages of the Purification Process:
- Advanced Technology is able to produce High Quality Water: It not only rejects most organics and salts from the water but also removes residual synthetic detergents, bacteria, viruses and suspended microscopic matters.
- Flexibility in Usage: High rate of rejection over a wide range of solids in the feed water.
- Spiral Wound Membrane: The spiral wound construction of the separator combines alternating layers of semi permeable thin layer composite (TLC) membrane and open flow Channel. This provides an extremely high membrane “are-to-flow” volume ratio which ensures Maximum effectiveness in fluid Sperry and particle removal.
- Low Energy Cost: Only operates under mechanical pressure.
- Low Chemical Cost: Addition of chemicals is not required unless the feed water has unusual characteristic.
Process:
Stage 1: Raw water is pumped to the sand filter filled with pebbles, this takes care of physical dust in the water.
Stage 2: Activated Carbon removes Color, Odor, Chlorine etc.
Stage 3: 5 Micron Filter – prevents the dust below 5 micron
Stage 4: 1 Micron Filter - prevents the dust below 1 micron
Stage 5: RO Membrane converts the hard water into sweet Mineral Water by rejecting most organics and salts from the water itself and also removes residual synthetic detergents, bacteria, viruses and suspended microscopic matters.