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The hypothesis having excessive fluoride and hardness levels in ground water in combination
is said to have been associated with the onset o f CKDu. Provision o f good quality drinking
water devoid o f fluoride and hardness to levels less than nephrotoxic levels would be
considered o f paramount importance. In this respect, several types o f water filters have been
introduced to CKDu affected areas o f which RO units are the most popular filters. Hence, this
research aims at investigating the effectiveness o f domestic RO units in removing fluoride and
hardness levels reported in CKDu affected areas under different climatic conditions for a period
covering dry and wet seasons. Two monsoons and the 2nd inter monsoon were simulated in the
laboratory and the removal o f fluoride and hardness by the RO unit were evaluated according
to the drinking water guidelines.
Northeast monsoon was subdivided into extreme wet and wet to dry periods. Hardness and
fluoride concentrations in the raw water during above periods were 110 ppm and 578 ppm and
fluoride concentrations were 0.52 ppm and 2.93 ppm respectively. In the above periods
hardness values obtained in the permeate were 12 ppm and 24 ppm and the fluoride was
com pletely removed during extreme wet period and 0.15 ppm fluoride was observed in wet to
dry period. In the 2nd inter monsoon, hardness and fluoride concentrations in raw water were
1032 ppm and 7 ppm respectively and in the permeate 40 ppm hardness and 0.39 ppm of
fluoride were observed. A ll the above fluoride and hardness values in the permeate do not
com ply with the required drinking water guidelines. Southwest monsoon was subdivided in to
three periods namely extreme dry, dry and dry to wet. In extreme dry period hardness and
fluoride in raw water were 1230 ppm and 15.5 ppm respectively. In the permeate hardness
concentration varied from 48 ppm -184 ppm and fluoride concentrations varied from 0.19 ppm1.67 ppm. At the latter stage both the fluoride and hardness values have exceeded the required
drinking water guideline values. This happen when all the adsorption sites o f the filter unit get
saturated with the increase o f the raw water concentration and then excess amount o f water
constituents w ill pass through the RO membrane. Flow rate was dropped from 0.24 litres/min
to 0.03 liters/min during these periods implying that the membrane o f the unit has started to
get clogged. A s the performance o f the RO unit depends on the initial constituent’s
concentration in the raw water, according to this study people can use RO unit for a period of
6 months without getting clogged
