A preliminary study of Opuntia stricta as a coagulant for turbidity removal in surface waters

Natural polymers,extracted from plants,can be used as coagulants for water treatment in addition to metal salts and synthetic polymers. natural materials may offer benefits such as local production,lesser health hazards and affordability for developing world. opuntia stricta plant,a cactus specie native to mexico,has been explored in this study for its efficacy as coagulant. efficiency of opuntia stricta was assessed on the basis of turbidity removal from lab prepared and surface water samples. the effect of water ph on its performance was also analyzed. the study results revealed that removal efficiency of opuntia stricta for turbidity removal remains consistent within a wide ph range (ph 5 to 10),in contrast to other coagulants which are ph dependent. furthermore,ph of the water remains constant during coagulation and ph adjustment may not be required for subsequent treatment processes,which is often needed in case metal coagulants are used. residual turbidity below 20 ntu is conveniently achieved by using opuntia stricta even when it is used at very low doses. formation of exceptionally large flocs and their linear configuration reveals the possibility that mechanism of coagulation by opuntia stricta is adsorption and inter-particle bridging. © pakistan academy of sciences.