Evaluation of Coriandrum sativum Leaves and Stems as Natural Coagulants for Sustainable Drinking Water Treatment

Natural coagulation processes are essential for the removal of colloidal particles by aggregating them into larger flocs that can easily settle in sedimentation basins—a method known for its simplicity and cost-effectiveness. This study aimed to enhance the efficiency of a water treatment plant through the use of a natural product, cilantro (Coriandrum sativum), as an adsorbent. Both fresh and dried cilantro leaves and stems were utilized. Comprehensive analyses were conducted on various physicochemical parameters of water samples, both before and after treatment, including the concentration of selected heavy metals. Additionally, biological assessments were performed to determine total bacterial and algal counts, as well as the presence of diatoms, protozoa, and pathogenic helminths. Water samples were collected from a conventional water treatment facility situated at the endpoint of freshwater streams in the Daqahliya governorate. The samples underwent a pretreatment process using natural coagulation/flocculation with cilantro as the adsorbent, tested via a jar flocculator apparatus. Results indicated that dried cilantro stems achieved the highest turbidity removal efficiency at 76.33% with an optimal dosage of 0.6 g/L. Dried leaves followed with 69% efficiency at 0.3 g/L. Fresh stems and fresh leaves showed removal efficiencies of 35.4% and 33%, respectively, both at a dosage of 0.3 g/L and within a pH range of 6 to 7. In conclusion, one-sixth of people do not have access to any kind of safe and improved water supply within one kilometer of their residence. So cilantro presents promise as a sustainable, low-cost natural coagulant for enhancing water treatment and meeting the rising demand for clean water.