Investigating combustion derived runoff from solid waste dumpyard fire suppression activities: chemical profile and environmental risks

In many developing countries, increasing waste volumes are often dumped in unlined, poorly managed sites that are prone to frequent fires. Firefighting typically involves excessive water spraying, which produces large volumes of combustion derived runoff (CDR), a toxic liquid similar to landfill leachate. This runoff can severely pollute nearby ecosystems. This study presents the first comprehensive field assessment of CDR from a municipal solid waste (MSW) fire under tropical conditions. It combines ecotoxicological indicators, spatial modelling, and risk evaluation tools, based on the Brahmapuram dumpyard fire breakout in Southern India as a case study. This site, located in a tropical region, received about 400 m³ of water per day during the fire to suppress flames and smoke. While previous studies have focused on air emissions or general leachate, the environmental impact of CDR, particularly its flow into soil and water, has remained largely unexamined. This research fills that gap by analyzing fire residues, CDR, soil, sediment, and nearby surface and groundwater for contamination. Results showed that CDR had characteristics of stabilized landfill leachate, with low biodegradability (BOD : COD ratio is 0.11) and high toxicity, making it difficult to treat using conventional biological processes. Soils exposed to CDR had extreme heavy metal contamination, with a pollution load index over 100. The leachate pollution index was lower than those in past reports due to the dilution effect of water spraying. However, the overall mass of trace metals reaching downstream areas was higher due to the large CDR volume. Spatial mapping confirmed heavy metal enrichment in CDR affected zones. Leachability tests also suggested that up to 25% of metals in fire residues could percolate over time, posing serious long-term risks to soil and water. The study calls for immediate updates to fire suppression strategies, including engineered containment, environmental monitoring, and post-incident leachate management to reduce long-term ecological harm.