Abstract
Recovering valuable resources from sewage sludge addresses resource scarcity but carries risks of releasing pathogens and toxic pollutants when applied to land. This study applied a structured quality monitoring and risk assessment framework to evaluate a soil improver derived from sewage digestate, using a Norwegian case study. Product quality, regulatory compliance, and health and environmental risks were assessed based on extensive monitoring and quantitative risk models. The soil improver met key standards for nutrient content and pathogen inactivation. However, zinc concentrations exceeded regulatory thresholds in 38% of samples. Microbial risks from E. coli O157:H7 and Salmonella spp. remained below the WHO benchmark of 10−6 DALYs per person per year across all exposure scenarios. Health risks from heavy metal uptake via wheat consumption were within acceptable limits (cumulative risk quotient: 0.5 median, 0.9 at the 95th percentile). Environmental risk assessment of 168 chemicals, including heavy metals, PAHs, PFAS, and pharmaceuticals, indicated a cumulative risk quotient of 3.4, primarily driven by heavy metals (57%). Long-term risk analysis projected a 1.1-fold increase in heavy metal risk over 50 years, indicating potential accumulation. This study demonstrates the practical application of an integrated framework to guide safe and sustainable reuse of wastewater-derived products, balancing circular economy objectives with human health and environmental protection.