Effective turbid water treatment using natural eco-friendly coagulants derived from oat and onion seeds

Conventional chemical coagulants are used for potable water treatment, which requires unsustainable mining and transformation of raw materials for their production with costly sludge disposal. Natural coagulants are potential alternatives to chemical coagulants. This study emphasized the use of natural eco-friendly coagulants (oat and onion seed) for turbid water treatment. Coagulant seeds were characterized by different techniques such as SEM, EDX, FTIR, and zeta potential analyzer. Response surface method (RSM) was used to optimize the coagulation process. The effect of initial water turbidity, pH, coagulant seed extract dose, slow mix time, and settling time on the efficiency of turbidity removal was studied. The relation between removal efficiency and the main three significant operational parameters (initial water turbidity, pH, and coagulant extract dose) was fitted to a quadratic model. The optimal removal was achieved at alkaline and neutral media (pH = 7-11 for oat extract and pH = 7-9 for onion extract). The turbidity removal efficiency was 99% using 6 ml/L oat extract dose and 98.9% using 4 ml/L onion extract dose at pH equal to 8 and initial turbidity of 190 NTU. The effect of using oat extract or onion extract with alum was studied, and the results indicated that the optimum dose was found to be 1 ml/L of a natural extract with 10 mg/L alum. Furthermore, oat and onion extract aids were able to decrease the organic load in the treated water. Oat and onion seed extracts were proven to be efficient and eco-friendly natural coagulants or coagulant aids for surface water treatment.