Bioensaios de fitotoxicidade e biodegradabilidade em amostras de um lixiviado de aterro sanitário tratado pela reação ferrioxalato

Abstract

The phytotoxicity and biodegradability of the sanitary landfill leachate (SLL) samples treated by the ferrioxalate reaction was evaluate. Thus, using the lab-scale photoreactor based on the batch system, an ferrioxalate reaction with pH of the solution 6 and 100 mg Fe L -1 (1:3 of Fe: oxalic acid) was performed, and samples were taken during the treatment to follow bioassays. Biodegradability was evaluate by Zahn-Wellens tests, while the phytotoxicity assays was performed using the Lactuca s. germinations. Using different dilutions, variables responses such as germination index (GI), absolute and relative germination (AG and RG), relative growth of the hypocotyl and radicle (RGH and RGR) as well as its inhibitions (IRGH and IRGR); was analyzed. In addition, lethal concentrations of 50% tested organisms was calculated (LC 50 ). In such conditions, a good responses of COD, BOD, DOC and absorbance at 254 nm reductions were obtained, as well as biodegradability conditions were increased (BOD/COD) confirmed by the biodegradability assays. According to the Zahn-Wellens tests, the untreated SLL consist in a low portion of biodegradability compounds in terms of BOD/COD ratio (0.18), which can be increase during the ferrioxalate treatment, leading a ~ 0.4 ratio after ~ 55 mM of H 2 O 2 consumed. However, the beneficial chemical oxidation of toxic compounds (LC 50 ~ 15%) was confirmed by the phytotoxicity assays, since the LC 50 increased to ~ 44%.