From Local Resources to Safe Water: Circular Approaches for Decentralized Water Treatment

Access to safe water remains a challenge in low-income and rural regions, where conventional purification can be unaffordable or unsustainable. Cocoa production waste, particularly cocoa pod husk, can be valorized as a precursor of activated carbon, while natural zeolites provide a complementary adsorptive and ion-exchange medium. This bibliometric review, complemented by a qualitative narrative synthesis, examines circular-economy strategies based on locally available adsorbent materials for decentralized water treatment. Bibliographic records were retrieved from Scopus using a structured search strategy and screened according to predefined eligibility criteria. A final corpus of 472 articles published between 2016 and 2026 was analyzed in VOSviewer using fractional counting and complementary Author Keywords and All Keywords co-occurrence networks. The reviewed evidence indicates complementary removal mechanisms and suggests that hybrid integration may improve efficiency, durability, and regeneration while valorizing agricultural residues and locally available minerals. The synthesis considers adsorption capacity, empty-bed contact time, removal targets, regeneration, and hydraulic performance. Important gaps remain regarding variable pH, competing ions, long-term stability, scale-up, reproducibility, and community adoption. The evidence supports a methodological pathway based on optimizing cocoa-residue activation, integrating the resulting carbon with zeolite media, and evaluating hybrid filters under realistic laboratory and field conditions. Within a circular-economy framework, this approach may contribute to locally grounded, low-cost drinking-water solutions for rural communities.