This study investigates the effectiveness of the coagulation–flocculation process using inorganic coagulants to improve the quality of palm oil mill effluent (POME) and evaluate the agronomic potential of the resulting solid residue. Coagulation treatment with a dosage of 2 kg coagulant per 20,000 L POME significantly reduced total suspended solids (TSS) by 97% and total phosphorus by 31%, indicating high treatment efficiency. Conversely, excessive coagulant dosage (3 kg) led to particle restabilization and reduced removal performance. X-ray fluorescence (XRF) analysis of the coagulated solids revealed an enrichment of mineral oxides, including SiO2, P2O5, SO3, CaO, and Fe2O3, which are beneficial for soil fertility and plant growth. These elements contribute to improved soil pH, phosphorus availability, and plant resistance to biotic and abiotic stress. Meanwhile, soluble elements such as K2O and Cl remained in the liquid phase, preventing salt accumulation in the solids. The findings demonstrate that coagulation–flocculation not only enhances wastewater quality but also produces a value-added by-product suitable for use as organo-mineral fertilizer or soil ameliorant. This approach aligns with the principles of the circular economy by converting industrial waste into sustainable agricultural inputs.
Pamungkas et al. (Thu,) studied this question.