Abstract In this paper, a couple of pretreatments were applied to raw cheese whey to increase its biodegradability in an anaerobic reactor. The first stage consisted of coagulation/flocculation using Carica papaya seeds as a biocoagulant, and the second stage was a study of Fenton and photo-Fenton processes. The cheese whey was collected from a dairy industry plant and characterized according to physicochemical parameters to check the pollution potential (chemical oxygen demand — COD of 55.96 g L−1 and biochemical oxygen demand — BOD of 21.51 g L−1). The coagulation/flocculation process provided high turbidity removal (94–96%). After preliminary experiments with Fenton reactions in coagulated whey, a central composite design, a desirability function and a response surface were applied to obtain the optimal operating conditions (reaction time: 90 min, H2O2: 1.95 M; H2O2/Fe2+ ratio: 55) resulting in 66.4 and 62.6% of COD and TOC removals, respectively. The kinetic evaluation of photo-Fenton reaction under optimal conditions revealed the potential minimization of iron (H2O2/Fe2+ ratio: 65) and reaction time (60 min) to achieve 70.1% of COD removal under visible ultraviolet light irradiation (UV/vis). After applying the coagulation/flocculation and photo-Fenton processes, an increase in biodegradability was achieved (BOD5/COD > 0.4), allowing the application of the biological process. The batch treatment in a UASB reactor achieved 86–88% COD removal from the 24th day of operation. The proposed hybrid process eliminated between 96–98% of total COD.

Resumo Neste artigo, dois pré-tratamentos foram aplicados ao soro de queijo bruto para aumentar sua biodegradabilidade na aplicação de um reator anaeróbio. A primeira etapa consistiu na coagulação/floculação utilizando sementes de Carica papaya como biocoagulante, e a segunda etapa foi o estudo dos processos Fenton e foto-Fenton. O soro foi coletado em uma fábrica de laticínios e caracterizado quanto a parâmetros físico-químicos para verificar o potencial poluidor (demanda química de oxigênio — DQO 55,96 g L−1 e demanda bioquímica de oxigênio — DBO de 21,51 g L−1). O processo de coagulação/floculação promoveu a remoção de nível alto de turbidez (94–96%). Após testes preliminares das reações Fenton no soro coagulado, houve a aplicação do delineamento de composto central, da função desejabilidade e da superfície de resposta para obter as condições ótimas de operação (tempo reacional: 90 min, H2O2: 1,95 M e razão H2O2/Fe2+: 55), resultando em 66,4 e 62,6% de remoção de DQO e TOC, respectivamente. A avaliação cinética da reação foto-Fenton nas condições otimizadas revelou o potencial da minimização da concentração de ferro (razão H2O2/Fe2+: 65) e do tempo reacional (60 min) para atingir 70,1% de remoção de DQO sob irradiação de luz ultravioleta visível (UV-vis). Após aplicação dos processos de coagulação/floculação e foto-Fenton, um aumento da biodegradabilidade foi alcançado (DBO5/DQO > 0,4), possibilitando a aplicação do processo biológico. O tratamento batelada em reator anaeróbio de manta de lodo de fluxo ascendente (UASB) promoveu 86–88% de remoção de DQO a partir do 24º dia de operação. O processo de tratamento híbrido proposto eliminou entre 96 e 98% da DQO total.

Abstract This study evaluated extracellular production of biopolymer using fungus Mucor racemosus Fresenius and glycerol as a carbon source. Initially employing conical flasks of 500 mL containing 100 mL of cultive medium with 0.18 ± 0.03 g.L–1 of microorganisms, the results showed that the best conditions of the variables studied were: initial concentration of glycerol 50 g.L–1, fermentation time of 96 h, inoculum cultivation time of 120 h, and aeration in two stages–the first 24 hours without aeration and 72 hours fermentation with aeration of 2 vvm and 2 g.L–1 of yeast extract. The experiments conducted in a Biostat B fermenter with a 2.0 L capacity that contained 1.0 L of medium showed production of 16.35 g.L–1 gum formed and 75% glycerol consumption. These conditions produced a biopolymer with the molecular weight and total sugar content of 4.607×106 g.mol–1 (Da) and 89.5%, respectively.

The biosorption of lead by the brown alga Sargassum filipendula was studied. pH 4.0 was the optimum value for the biosorption of lead. Isotherms indicated that for solutions containing 0.03 ± 0.001 up to 3.27 ± 0.04 mmol/L of lead, 2.0g/L was the optimum biomass concentration. The Langmuir model was fitted to represent the experimental data, and the kinetics of biosorption presented equilibrium in 30 min. The continuous system operated for 56 hrs presenting a 100% binding of ionic lead, which corresponds to an accumulation of 168 g lead, equivalent to a load of 1.7 mmol ionic lead/g Sargassum filipendula. The results that were obtained in a continuous system showed a gradual saturation of the biomass in the reactors