Reduction of River Water Turbidity Using Natural Coagulant from Nagara Bean (Vigna unguiculata subsp. cylindrica) Powder

In the Banjar Regency of Indonesia, where merely 72.55% of the population has access to potable water and river water turbidity (53 NTU) above national regulations (<3 NTU), the identification of effective and sustainable water treatment methods is imperative. This study examined the effectiveness of locally-sourced Nagara bean (Vigna unguiculata subsp. cylindrica) powder as a natural coagulant in water treatment. Employing a posttest-only control group experimental design, we evaluated several doses (400, 600, and 800 mg/L) and contact durations on river water samples, with turbidity reduction as the principal outcome measure. Statistical analysis employing Two-way ANOVA and post-hoc Tukey HSD testing indicated that optimal performance occurred at a dosage of 600 mg/L with a contact period of 60 minutes, yielding a 54.7% reduction in turbidity (from 77.46 NTU to 35.1 NTU). This performance exceeded that of other natural coagulants, including tamarind and Moringa seeds. The research revealed a non-linear dose-response relationship, emphasizing the intricacy of the coagulation process and the necessity for accurate dosage. The findings indicate that Nagara bean powder presents a sustainable and economical substitute for chemical coagulants in water treatment in areas with inadequate infrastructure; nevertheless, additional research is required to investigate wider dosage ranges and diverse water quality circumstances.