Abstract:
Clear appearance is one of the characteristic features of safe drinking water. Removal
of colour and turbidity gives clear appearance to water. Production of clear drinking
water from most raw water sources involves use of coagulant to remove turbidity.
There are a number of substances that are available for treating turbidity, while some
effective natural flocculating agent, providing a low-cost household solution to the
critical need for potable water in rural riparian communities. The objective of this study
was to determine the optimum conditions of efficient turbidity removal of three
conventional coagulants, Ferric chloride (FeCl3), Poly Aluminium chloride (PACL)
and Aluminiumsulphate (ALUM, Al2(SO4)3.xH2O) and three natural vegetable
coagulants, Moringa (M. oleifera) seeds, Nirmali (S. potatorum) seeds and Cow Peas;
and also to compare the cost effectiveness and treatment efficiency of natural
coagulants. The influence of pH and coagulant dosages on the coagulation process was
studied where the conditions were optimized corresponding to the best removal of
turbidity. To obtain the optimum dose of the coagulant, jar tests were conducted over
the various coagulant sample ranges. To investigate the optimum pH for coagulation
process, the above procedure was repeated over the range 5 to 7 pH values of the raw
water. The optimum pH for PACL, Alum, FeCl3, Moringa, Nirmali and Cowpea were
6.0, 6.5, 6.5, 5.5, 5.5 and 6.5 respectively and the optimum coagulant dosages of
PACL, Alum, FeCl3, Moringa, Nirmali and Cowpea were 20 ml (0.2 g), 40 ml (0.8 g),
40 ml (0.4 g), 80 ml (1.6 g), 80 ml (0.8 g) and 40 g respectively for 500 ml raw water.
Of the materials tested, alum showed the highest turbidity removal efficiency. Higher
dosages did not significantly increase turbidity removal and were not economical.
