Advanced oxidation of bleached eucalypt kraft pulp mill effluent.

In this study a poorly biodegradable (BOD/COD = 0.3) industrial alkaline ECF bleaching filtrate was treated using different advanced oxidation processes to evaluate their use in combined chemical-biological treatment aimed at increasing recalcitrant COD removal and improving final effluent quality. Oxidative treatments included ozonation combined with hydrogen peroxide (2, 5, 10, 20 mmol L(-1) O3/0.7, 2, 5, 10 mmol L(-1) H2O2) and photocatalysis with hydrogen peroxide (UV/2, 4 and 8 mmolL(-1) H2O2) and with TiO2 (UV/TiO2/0.7 and 4 mmol L(-1) H2O2). The O3/H2O2 process increased effluent biodegradability by up to 68% as a result of increasing BOD and decreasing COD. Increasing the O3 dose had a greater effect on biodegradability improvement and lignin and colour removal efficiencies than increasing the H2O2 dose. A combined oxidant dose of 5 mmol L(-1) O3 and 2 mmol L(-1) H2O2 resulted in 75% lignin removal, 40% colour removal and 6% carbohydrate loss without mineralizing the organic carbon. The photocatalytic processes led to a decrease in effluent biodegradability through combined decrease in BOD and increase in COD and did not result in efficient lignin or colour removal. Photocatalytic oxidation was apparently inhibited by the high chloride and COD levels in the alkaline filtrate, and may be more efficient in recalcitrant COD removal if performed after biological.

A comparative study of Trypanosoma cruzi enzyme polymorphism in South America.

1. The electrophoretic patterns of 13 loci were used to compare the three main T. cruzi zymodemes (Z) circulating in North/Northeastern Brazil (Br 1 through 3) with the four principal zymodemes present in Southeastern (BrA through D) Brazil. 2. Nei's standard genetic distances (D) obtained by paired comparison of the Brazilian zymodemes indicate the presence of four divergent groups, separated by D = 1.18. Zymodemes BrB and BrD presented heterozygous patterns for six and three loci, respectively, for alleles coding for isoenzymes of the BrA/Br 2 and BrC zymodemes. 3. The 7 principal Brazilian zymodemes were in turn compared with the 11 other zymodemes thus far identified in South America (Colombia, Bolivia, Paraguay and Chile). Numerical taxonomy demonstrated the presence of three main infraspecific categories ('groups') separated by D greater than 1.08. Each of these 'groups' could be divided into 2 or 3 subgroups at D greater than or equal to 0.50. 4. The wide range of zymodemes within a group separated by a genetic distance ranging from 0 to 0.95, the presence of zymodemes with variable numbers of heterozygous patterns (1 to 6), the detection of two homozygous zymodemes circulating sympatrically with their corresponding heterozygous zymodemes, and the circumstantial evidence that the majority of zymodemes carrying heterozygous profiles are found in the domestic sector of subtropical regions and always associated with Triatoma infestans, indicates that genetic recombination can also occur presently under certain conditions.