Carbon–Neutral Granular Filtration for Sustainable and Safe Rainwater Harvesting in Urban Malaysia

Abstract This work aims to design a granular filter-based carbon–neutral rainwater treatment system. Granular filters are capable of cleaning rainwater while leaving a carbon–neutral trace to promote environmentally friendly rainwater collection techniques by examining the filtration performance and impact on the environment. The elimination of pollutants and impurities from collected rainwater through granular filters highlights the significance of meeting water quality requirements. The system uses three filters (F1, F2, and F3) for the treatment process where palm (oil) fruit shell-activated carbon, coconut shell-activated carbon, coarse sand, and fine sand are used as raw materials. The physicochemical quality of rainwater (harvested at four different locations) in Selangor, Peninsula Malaysia, from February to March 2022 has been investigated in this study. The analysis covers seven essential properties, such as ammoniacal nitrogen, biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD), dissolved oxygen (DO), pH, total dissolved solids (TDS), and Turbidity. The obtained results indicate that the harvested purified rainwater generally meets World Health Organization (WHO), National Water Quality Standards for Malaysia (NWQSM), and Ministry of Health, Malaysia (MOH) standards, with pH ranging from 6.5 to 9 and BOD 5 within recommended limits. The parameters at the initial filtration maintain the acceptable limit for drinking water quality. However, after the feasibility study of 10–30 L of filtration, the DO range (7.77 to 8.67 mg/L) indicates ambient gas concentration. BOD 5 value exceeds the limit of 9.11 mg/L after 30 L of filtration for the F3 column. The system has potential applications in drinking, gardening, agriculture, and toilet flushing. Based on important physicochemical factors, the parameters at the first filtering keep the drinking water quality within an acceptable range. Nonetheless, further conductivity and mineral content testing is advised for a thorough study of drinking water. The results of this study thus support the larger objective of encouraging water sustainability and reducing the carbon footprint in water treatment procedures, which is to improve environmentally friendly rainwater harvesting technologies.