Resource recovery pathways for grit from faecal sludge and wastewater pre-treatment

This study explores the under-researched potential of grit generated from wastewater (WW) and faecal sludge (FS) treatment in low-income settings. It characterized grit from both streams during wet and dry seasons and identified viable reuse pathways. FS grit was found to have high organic carbon (30.3%), nitrogen (2.9%), and cation exchange capacity (90.6 meq/100 g), supporting its reuse as a soil conditioner. The WW grit contained over 98% sand-sized particles, making it suitable as a partial replacement for sand in non-structural concrete. Additionally, the physical characteristics of both grit types support their use as bulking agents in composting and in landscaping or road subbase applications. However, both grit types exceeded safe pathogen thresholds, with E. coli counts above 10⁵ CFU/100 mL, necessitating pre-treatment. The study highlights that FS treatment plants produce more grit (6.2 m³/1000 m³) than WW systems (0.077 m³/1000 m³), reinforcing the need for strategic management. The findings show that both FS and WW grit possess distinct, complementary qualities that, when treated and applied appropriately, offer valuable opportunities for resource recovery in the sanitation and construction sectors. This supports circular economy objectives and provides a pathway to more sustainable grit management in low- and middle-income countries.