Application of Thymus Species as Natural Coagulant for Elimination of Turbidity of Water and Its Comparison with the Conventional Coagulant

Introduction: The most important pollutant in surface water sources is turbidity. The aim of the study is to determine the most effective thyme plant extract as a natural coagulant to remove water turbidity and compare it with alum as a chemical coagulant.. Materials and Methods: In this study, plant extracts obtained from Thymus vulgaris (Tv), Thymus kotschyanus (Tk), and Thymus eriocalyx (Te) were used as natural coagulants for elimination of water turbidity. Then, the best of plant extract was confirmed by ninhydrin and FTIR analyses and the effect of simultaneous use of plant extract with chemical coagulant of aluminum sulfate (alum) was investigated in the hybrid ratio of 1:1, 2:1, and 1:2. Then, the effect of parameters include of pH, coagulant dose, turbidity removal efficiency, and the most suitable solvent for coagulant extraction were studied. Results: The results of this study showed that among the natural coagulants, Tv had a higher efficiency in elimination of water turbidity, and the highest amounts of turbidity elimination for Tv, alum, and Tv/alum hybrid coagulants was 94, 90, and 96, respectively. According to the results of this study, the most effective solvent for preparing plant extracts was 1M KCl solvent. Conclusion: The natural coagulant removes more turbidity from water than the chemical coagulant, and the simultaneous use of natural and chemical coagulants with a 1:1 ratio was more effective.