Dra. Yéber-Ortiz, María

This study aimed to improve the sustainability of the kraft pulp production process by recovering Pinus radiata and Eucalyptus grandis wastewater generated during the bleaching process. The effluents were obtained from the first alkaline extraction stage (E0) of the ECF bleaching sequence used to produce white Kraft cellulose, considering that this stage is where the highest contamination by phenolic compounds occurs and the effluent exhibits an intense color. A photochemical oxidation system, utilizing TiO2/S2O82-/UV, was implemented to generate in situ two highly oxidizing radical species, with high redox potential, a hydroxyl radical (HO• 2.8 eV ) and a sulfate radical (SO4•- 2.5-3.1 eV), which promote rapid degradation of contaminants. To obtain the optimal response, we employed the 2n model to construct a matrix of 15 experiments, utilizing the Box-Behnken design. According to the experimental variables studied, phenolic compounds were completely removed from the Eucalyptus effluent (0.0312 min-1) and 80% of them were removed from the pine effluent (0.0102 min-1), at pH 5.0 with 0.6 gL-1 of persulfate and 1.0 gL-1 of titanium dioxide. Under these conditions, the bioavailability of effluents from Pinus radiata and Eucalyptus grandis increases from 0.16 and 0.26 to 0.90, after the treatment. The excellent bioavailability of the effluents obtained after the treatment demonstrates that the process used is efficient in recovering wastewater from the pulp industry and that the treated water could be reused in the same process or returned to the ecosystem, without harming the environment.

Electrocoagulation of landfill leachate has been widely investigated, however, only few reports include the reuse of the treated water. In this work, treated leachate is evaluated as irrigation water. The main obstacle is the high Sodium Absorption Ratio. Reducing this indicator involves decreasing Na+ and increasing Mg2+ or Ca2+. Sodium concentration reduction is difficult by electrochemical methods (E0 = −2.71 V); Ca2+ increasing is not feasible as it precipitates. Hence, the use of different Al-Mg anodes was tested tending to increase Mg2+ concentration in the treated water The alloy 88%wtAl-12%wtMg was able to remove 52.9% of COD, 98.1% of turbidity, 97.9% of color, obtaining a SAR of 8.2 meq·L−1, total hardness (TH) of 64.2 meq·L−1 and a soluble sodium percentage (SSP) of 75.8 meq·L−1. This was achieved by working at a current density of 15 mA cm−2, a treatment time of 15 min and a pH 5.0. The phytotoxicity of the treated leachate was evaluated by the germination index using Lactuca Sativa L., reaching a value of 83.2%, which is considered excellent for irrigation water. During growth, 3–4 primary leaves were observed in seedings after 21 days, similar to when potable water was used. The results demonstrate that electrocoagulation is an adequate treatment technique for the reuse of landfill leachate if appropriated materials are used as anodes working in well selected operational variables.

High-colored wastewater generated during the cellulose bleaching process causes the inhibition of biological activity when released into the environment. This study aimed to evaluate the bacterium’s capacity, identified as RGM2262, to degrade a complex phenolic structure such as lignin, which is found in high concentrations in the effluents generated during the production of cellulose, raw material for the manufacture of paper. To determine the values of the experimental variables that allow for a greater degradation of organic matter, an experimental model was carried out through experimental design. Thus, the experimental matrix was obtained with the variables pH 7 (−1) to 9 (+1) and a treatment time of 1 day (−1) to 5 days (+1). The results show that, at pH 8 and pH 9, both treatments—with bacteria in bio-films and without bio-films—were efficient. On the second day of treatment, 100% of the color and the phenolic structure were removed, with a similar rate constant, and at the same time, 80% COD and 70% of TOC, respectively.