Assessment of Rainwater Harvesting Quantity and Treatment Quality Using Combined Silica Sand–Activated Carbon–Membrane Filtration in Sungai Langka Village, Indonesia

Clean water scarcity remains a critical challenge in many regions of Indonesia, particularly in rural areas such as Sungai Langka Village, Pesawaran Regency, Lampung Province. This study investigates rainwater harvesting (RWH) as an alternative clean water source by developing a combined filtration–adsorption treatment system consisting of three sequential columns—silica sand, activated carbon, and filter membrane—operated in continuous-flow mode. The research objectives include determining rainwater harvesting potential, optimizing the treatment system through artificial water testing, and evaluating treated rainwater quality against regulatory standards. Analysis of rainfall data from 2015–2024 using the Gumbel distribution method yielded a 2-year return period design rainfall of 99.86 mm, corresponding to harvesting potentials of 7.12 m3/hour and 2.94 m3/hour for galvanized iron and asbestos roofs, respectively. System optimization with artificial water demonstrated effective contaminant removal under extreme conditions, achieving up to 62.54% TDS removal and 82.19% Fe removal. Treatment of actual rainwater successfully adjusted pH from 6.83 to 7.65, reduced TDS from 37 to 22 mg/L (40.54%), and decreased Fe concentration from 0.64 to 0.07 mg/L (89.06%), with an Fe adsorption capacity of 0.252 mg/g. All treated water parameters met the Indonesian Minister of Health Regulation No. 2/2023 standards for sanitary hygiene water, confirming the system as a practical and affordable point-of-use solution for improving clean water access in water-scarce rural communities.