Chemical safety assessment of transformation products of landfill leachate formed during the Fenton process.

Organic chemicals identified in raw landfill leachate (LL) and their transformation products (TPs), formed during Fenton treatment, were analyzed for chemical safety following REACH guidelines. The raw LL was located in the metropolitan region of Campina Grande, in northeast Brazil. We elucidated 197 unique chemical structures, including 154 compounds that were present in raw LL and 82 compounds that were detected in the treated LL, totaling 39 persistent compounds and 43 TPs. In silico models were developed to identify and prioritize the potential level of hazard/risk these compounds pose to the environment and society. The models revealed that the Fenton process improved the biodegradability of TPs. Still, a slight increase in ecotoxicological effects was observed among the compounds in treated LL compared with those present in raw LL. No differences were observed for aryl hydrocarbon receptor (AhR) and antioxidant response element (ARE) mutagenicity. Similar behavior among both raw and treated LL samples was observed for biodegradability; Tetrahymena pyriformis, Daphnia magna, Pimephales promelas and ARE, AhR, and Ames mutagenicity. Overall, our results suggest that raw and treated LL samples have similar activity profiles for all endpoints other than biodegradability.

Fenton treatment of sanitary landfill leachate: optimization of operational parameters, characterization of sludge and toxicology.

This investigation aimed to refine the operational parameters of the Fenton process, to compare Fenton-treated and non-treated leachate with respect to physicochemical variables and toxicity towards Daphnia magna, and to characterize the sludge. The optimal conditions for the Fenton treatment involved the use of a reagent containing 12 g Fe2+ L-1, H2O2/Fe2+ molar ratio of 9 and pH 2.0, with oxidation, flocculation and sedimentation times of 30, 10 and 15 min, respectively. Under these conditions, the values of the majority of parameters, including chemical oxygen demand (COD), biochemical oxygen demand, dissolved organic carbon, true color (TC), carbohydrates, proteins, phosphorus, total solids, total volatile solids, dissolved volatile solids, Kjeldahl nitrogen, N-NH3 and iron, were reduced significantly after treatment. However, sludge production rate remained somewhat high (98 kg m-3 of treated leachate), although the specific resistance to filtration of the sludge was moderate (12 × 109 cm g-1). While the Fenton process achieved a satisfactory removal of COD (87%) and TC (91%), the treated leachate contained organic compounds that were resistant to oxidation and remained toxic towards D. magna. Hence we conclude that the Fenton process alone is not appropriate for treatment of leachate, because it could negatively affect the ecosystem in receiving water bodies, but it could represent a viable alternative for the pretreatment of landfill leachate.