<![CDATA[Peat water is a potential alternative water resource in Indonesia, particularly in the peatlands of Sumatra and Kalimantan. However, its high acidity and elevated concentrations of natural organic matter (NOM) prevent its direct use as drinking water. Since the physicochemical characteristics of peat water vary among regions, chemical dosage requirements and ionic behavior may differ under identical operating conditions. Therefore, as a preliminary optimization phase, this study comparatively evaluated the coagulation–flocculation performance of peat water collected from Sumatra and Kalimantan using the Jar Test method. Polyaluminium chloride (PAC) was employed as the primary coagulant, while burnt lime (CaO) and hydrated lime (Ca(OH)?) were evaluated as alkaline agents. Treatment performance was assessed based on initial baseline ionic responses, including pH, total dissolved solids (TDS), and electrical conductivity (EC). Statistical analyses were performed using two-way analysis of variance (ANOVA) followed by Tukey's honestly significant difference (HSD) test at a 95% confidence level. The results showed that sampling location, chemical treatment, and their interaction significantly affected all measured parameters (p < 0.001). Hydrated lime combined with PAC effectively increased pH, whereas TDS and EC responses varied according to treatment dosage and peat water origin. Among the evaluated treatments, HL200-PAC80 produced pH values closest to the Indonesian drinking water standard, whereas HL200-PAC20 applied to Kalimantan peat water resulted in the lowest residual TDS and EC. These findings demonstrate that regional variations in peat water characteristics strongly influence coagulation–flocculation performance, providing a foundational basis for site-specific dosage optimization prior to main-stage NOM and color removal processes. Contribution to Sustainable Development Goals (SDGs):SDG 6: Clean Water and SanitationSDG 11: Sustainable Cities and CommunitiesSDG 13: Climate ActionSDG 15: Life on Land]]>
