Comparative study of the effects of Herbal and chemical Coagulants in the clarification of raw water

The use of aluminum sulphate in clarifying raw waters raises many concerns about its impact on human health. Thus, the present study was initiated to compare the effects of Moringa oleifera and aluminum sulphate besides evaluating the association between M. oleifera or aluminum sulphate with Opuntia ficus-indica or syntofloc for water treatment. The essays were carried in Jar Test using waters of 352.80 Nephelometric Turbidity Units (NTU). The monitoring of different physico-chemical and microbiological parameters at different doses and after different decanting time was used to determine optimal conditions and evaluate the effectiveness of treatment. The results showed that it took fewer doses and less decanting time for aluminum sulphate than moringa to obtain the same residual turbidity. The use of 0.9 g/L of moringa removed 99% of turbidity after 12 h of decanting. Successive use of moringa (0.9 g/L) with O. ficus-indica extract (0.6 ml) reduced the decanting time to 15 min. However, this treatment eliminated only about 57% of total coliforms. The moringa/cactus association, although highly effective, remains less than the treatment based on aluminum sulphate and synthofloc. This "organic" association is nevertheless an ideal alternative because of its great capacities that could be further optimized. Key words: Coagulation-flocculation, turbidity, Moringa oleifera, aluminum sulphate, Cactus.