Statistical modelling of turbidity removal applied to non-toxic natural coagulants in water treatment: A case study

An investigation into two non-toxic natural coagulants abundantly growing in different countries, cactus (Opuntia spp.) and okra was performed on monthly river water samples (one-year period). The studied case was the Euphrates river/Al-Mashroo canal/Iraq. Six statistical models were interpreted and tested describing the residual turbidity after coagulation-flocculation for the three studied cases (optimum-coagulant-dose, optimum-flocculator-velocity-gradient and optimum-flocculation-time). According to the environmental parameters recorded during the study and the statistical analyses, two facts were concluded. The first fact was that controlling the optimum-flocculator-velocity-gradient of the coagulation-flocculation process gave the highest contribution ratio of the models. The second fact was that the most significant environmental parameter (statistically) in the coagulation-flocculation process was the initial turbidity. This was proved for the two natural coagulants under study. Also, from the results of the study, it was concluded that the two natural coagulants were of similar coagulation-flocculation properties, and they were competent for turbidity removal.