A sustainable bioremediation approach for treating real contaminated urban river water using natural coagulants from durian and rambutan seeds

The Surabaya River serves as the primary source of clean water for the city of Surabaya, however, its water quality has been declining due to pollution, necessitating an effective and sustainable water treatment solution. Therefore, this study aims to explore the potential of durian and rambutan seeds as bio-coagulants for treating the Surabaya River water. Coagulation-flocculation experiments via jar test were conducted and run for the duration ranging from 0 to 120 mins. Floc morphology and the Fourier transform infrared spectroscopy (FTIR) were used to understand the coagulation-flocculation mechanism. Kinetic modeling by using the Syafiuddin and the Khambhaty models evaluated statistically by using determination coefficient (R²), root mean squared error (RMSE), maximum error (E max ), and minimum error (E min ) was conducted to understand kinetic behavior and the numerical optimization was conducted by using generalized reduced gradient nonlinear method. The durian seed extract at a dose of 1 mL achieved higher turbidity reduction of 61.73%, outperforming the rambutan seed extract, which only achieved 42.03%. FTIR analysis confirmed the presence of bioactive compounds such as tannins and polyphenols, which interact with positively charged colloidal particles. Flocs morphology and formation by rambutan seeds tended to be simpler and more limited compared to durian seeds. The total cost which include raw materials, energy consumption by equipment, and labor for treating 1 L of real contaminated water was estimated to be 3.51 USD for durian seeds and 3.15 USD for rambutan seeds. • A sustainable bioremediation from durian and rambutan seeds was proposed • The proposed bioremediation method can treat real polluted river water • Bioactive compounds interact with positively charged colloidal particles • Cost for treating 1 L of contaminated river water ranged from 3.15 to 3.51 USD