Toxicity evaluation of the landfill leachate after treatment with photo-Fenton, biological and photo-Fenton followed by biological processes.

The objective of this study was the toxicity evaluation of landfill leachate samples both raw and after treatment by photo-Fenton (PF), biological (Bio) and photo-Fenton followed by biological (PF-Bio) processes. The organisms Artemia salina and Lactuca sativa were exposed to the leachate in different dilution. In the phytotoxicity evaluation, the inhibition of root (RGI) and radicle (RAGI) growth, and the number of germinated seeds (GR) were evaluated. In the ecotoxicity analysis, the 50% lethal dose (LD50) for each type of treatment was evaluated. The raw leachate, and after treatments PF, Bio and PF-Bio presented COD of 12,797, 1,347, 1,685, 220 mg/L and BOD5 of 4,251, 1,060, 692 and 89 mg/L, respectively. The GR was 0, 95, 25 and 40%, RGI was 100, 83, 100, 93%, whereas RAGI was 100, 72, 100 and 79% in the raw leachate and after treatments PF, Bio and PF-Bio, respectively. LD50 values of 0.25, 0.40, 0.38 and 0.54 were obtained for the raw effluent and after the PF, Bio and PF-Bio treatments, respectively. Smaller values of COD, BOD5, ecotoxicity and phytotoxicity were observed in the effluent after the PF-Bio treatment, indicating that this is the most environmentally suitable system for the treatment of landfill leachate.

Groundwater quality monitoring of the Serra Geral aquifer in Toledo, Brazil.

In this work, a physical-chemical, elemental and microbiological groundwater monitoring was performed on wells of the Serra Geral aquifer, located in the western region of the Brazilian state of Paraná, along with an evaluation of the elemental composition of soil sediments in the region of groundwater monitoring. The monitoring was carried out in 10 wells distributed throughout the rural area of the municipality of Toledo-PR. Elemental analyses were performed using the analytical technique of total reflection X-ray fluorescence spectrometry. From the results obtained, it was observed that in some wells, iron and lead concentrations were above the maximum limits allowed by the Brazilian legislation in some months, demonstrating that the evaluated groundwater is susceptible to contamination. By the analysis of the soil sediments, the presence of iron and lead in the region soil/rock was verified, which may be associated to rainwater percolation making it necessary to periodically monitor the groundwater consumed by the population of the municipality of Toledo-PR.

Determination of the mass transfer limiting step of dye adsorption onto commercial adsorbent by using mathematical models.

Reactive blue 5G dye removal in a fixed-bed column packed with Dowex Optipore SD-2 adsorbent was modelled. Three mathematical models were tested in order to determine the limiting step of the mass transfer of the dye adsorption process onto the adsorbent. The mass transfer resistance was considered to be a criterion for the determination of the difference between models. The models contained information about the external, internal, or surface adsorption limiting step. In the model development procedure, two hypotheses were applied to describe the internal mass transfer resistance. First, the mass transfer coefficient constant was considered. Second, the mass transfer coefficient was considered as a function of the dye concentration in the adsorbent. The experimental breakthrough curves were obtained for different particle diameters of the adsorbent, flow rates, and feed dye concentrations in order to evaluate the predictive power of the models. The values of the mass transfer parameters of the mathematical models were estimated by using the downhill simplex optimization method. The results showed that the model that considered internal resistance with a variable mass transfer coefficient was more flexible than the other ones and this model described the dynamics of the adsorption process of the dye in the fixed-bed column better. Hence, this model can be used for optimization and column design purposes for the investigated systems and similar ones.