Toxicity assessment of sanitary landfill leachate before and after Fenton treatment process

Sanitary landfills are widely accepted and promoted as the environmentally friendly way to properly dispose of solid waste. However, a harmful aspect is the leachate generation and management, which are currently recognized as one of the greatest challenges in the environmental engineering field. Due to the high leachate recalcitrance, Fenton treatment has been accepted as a viable and efficient treatment process, which significantly reduces the organic matter: 91 % of COD; 72 % of BOD5; and 74 % of DOC. However, the acute toxicity of leachate must be assessed, mainly after the Fenton process, with the view of performing a low-cost biological post-treatment of the effluent. Despite the high redox potential, degrading 185 organic chemicals compounds identified in raw leachate, the present work reports a removal efficiency of almost 84 %, counting 156 organic compounds removed, and almost 16 % of persistent compounds. After Fenton treatment, 109 organic compounds were identified, beyond the persistent fraction of almost 27 %, wherein 29 organic compounds remained unchanged after Fenton treatment, counting 80 new short chain and lower complexity organic compounds formed. Despite the biogas production ratio increase (3-6 times), and significant enhancement of the biodegradable fraction susceptible to oxidation in respirometric test, a higher reduction in the oxygen uptake rate (OUR) was identified after Fenton treatment due to persistent compounds and their bioaccumulation. Additionally, the D. magna bioindicator parameter indicated that treated leachate is three times more toxic than raw leachate.