Integration of riverbank filtration with multistage filtration for sustainable water supply in rural areas of West Bengal

Abstract

This study assesses the effectiveness and sustainability of combining riverbank filtration (RBF) with multistage filtration techniques, including roughing filters, slow sand filters, and activated carbon, to address the challenge of removing emerging contaminants in rural areas of West Bengal, India. Through a comprehensive approach, the research evaluates the sustainable withdrawal quantity of sub-surface water in the riverbank via pumping tests and well field design, assesses the effectiveness of RBF and multistage filtration systems individually and in combination, and investigates novel methods to enhance water quality and mitigate emerging contaminants. Pumping tests and well field design indicated a sustainable withdrawal quantity with transmissivity measurements averaging 1956 m²/day, ensuring long-term water availability and minimal ecological disruption. The proposed well field design, comprising seven wells spaced 52 meters apart and each pumping 800 m³/day, maintained drawdown within acceptable limits. Mechanical sieve analysis guided the selection of appropriate gravel pack materials, ensuring optimal filtration efficiency. The combined use of RBF with multistage filtration techniques demonstrated superior effectiveness in removing emerging contaminants from raw water sources, surpassing performance expectations with significant contaminant removal rates and minimal fouling. Chemical tests confirmed compliance with permissible limits for parameters such as pH, TDS, nitrate, sulphate, iron, and ammonia, while bacteriological tests highlighted the necessity for continuous monitoring due to fluctuating contamination levels. The multistage filtration system notably reduced endosulfan concentration from river water to well water, achieving substantial percentage removal and enhancing water safety, thus validating the integrated approach as a viable solution for sustainable water supply in rural West Bengal.