Sustainable turbidity removal in urban water treatment using dual-layered crushed overburnt bricks and sand filters

Urbanization and climate change intensify global water security challenges, particularly as turbidity hinders disinfection and destabilizes treatment processes. Although rapid gravity sand filtration is widely employed, its efficiency diminishes under conditions of high particulate loads. This study introduces a dual-layer filter that utilizes industrial waste, specifically crushed overburnt brick (COB), as the primary filtration medium. This medium is layered above sand and stabilized by a geotextile separator to prevent media migration. the system's performance was compared systematically to a conventional filter across influent turbidities ranging from 0 to 300 NTU. The optimal configuration, consisting of 30 cm of COB and 30 cm of sand, demonstrated superior efficacy by maintaining effluent turbidity below 5.17 NTU and achieving an average removal rate of 96.99%. It extended filter runs by up to 70%, increased the unit filter run volume by 53.7%, and reduced backwash water consumption by 39% at high turbidity levels. The geotextile ensured hydraulic integrity, while the high porosity of COB (38%) facilitated deeper particle penetration and slower head loss development. Depth analysis confirmed that a COB layer of at least 22.5 cm is critical for resilience under high-turbidity conditions. This research validates a circular economy solution by transforming brick waste into a high-performance filter medium. The engineered system offers a scalable, low-maintenance, and resource-efficient technology for enhancing water treatment robustness in turbidity-prone, resource-constrained environments.