Sludges generated in the biological processing of sewage are complex mixtures, the constituents of which pose risks to public health and the environment. Anaerobic digestion is considered the most sustainable option for treating sludge because it offers the possibility of generating biogas. The aim of this study was to compare the quantities, properties, biodegradabilities and biochemical methane potentials (BMP) of primary sludge (PS) generated by a primary decanter with acidogenic sludges produced by upflow anaerobic (UA) reactors operating at solids retention times (SRTs) of 2, 4, 6 and 8 days (Samples S2, S4, S6 and S8, respectively). Sludges from both pre-treatments were submitted to alkaline solubilization in order to determine the efficiency of the process in disrupting extracellular complexes. Based on the levels of total solids (TS) present, the primary decanter was found to generate higher quantities of excess sludge (yield of 3.1 gTS∙d−1) than UA reactors operating at low SRTs (yields in the range 1.69 to 0.64 gTS∙d−1). The concentrations of dissolved materials in PS and Samples S2 and S8 were considerably higher after alkaline solubilization, with respective increases of 8, 14 and 28-fold in dissolved organic carbon, 12, 20 and 40-fold in chemical oxygen demand, 25, 31 and 59-fold in proteins, and 17, 21 and 63-fold in carbohydrates. In addition, the BMP value for S8 was some 13% higher than that recorded for PS while the kinetic constant for gas production by S8 was 1.8-fold greater than that of PS. It is concluded that a pre-treatment combining anaerobic digestion at low SRT and alkaline solubilisation would lead to improved performance in subsequent stages of anaerobic digestion and, consequently, increased efficiency in biogas production.

RESUMO Usualmente, o tratamento convencional de águas com altas densidades de cianobactérias e concentração de cianotoxinas não garante efluente consoante o padrão de potabilidade vigente (1,0 µg.L-1 de microcistina). Etapas adicionais fazem-se necessárias, destacando-se a adsorção por carvão ativado granular ou pulverizado. Neste contexto, o objetivo geral deste trabalho foi avaliar em escala de bancada a remoção de microcistina em água natural por adsorção em colunas de carvão ativado granular de casca de coco, após as etapas de clarificação e filtração em areia. Os resultados mostraram que o transpasse no carvão de maior granulometria ocorreu em menor tempo de contato (2 h), quando comparado ao de menor granulometria. Tais resultados abrem perspectiva de emprego em escala real por garantir efluente com concentração inferior ao que estabelece a Portaria 2914 por mais tempo e utilizando menor massa de carvão.

ABSTRACT Conventional treatment process of natural waters with high densities of cyanobacteria and cyanotoxins usually presents low efficiency according to the present drinking water standard (maximum permissible value of 1.0 µg.L-1 of microcystin). Additional steps, such as activated carbon, commonly become necessary to achieve the maximum permissible value of microcystin (1.0 µg.L-1) set up by Brazilian Drinking Water Regulation 2914. In this context, the main objective of this work was to evaluate microcystin removal from natural waters by means of two granular activated carbons after clarification and sand filtration in bench scale. The results pointed out that the breakthrough happened in activated carbon with highest grain sizes in lower contact time (2 h) , when compared with that with smaller grain sizes. These results open the perspective of an application of the activated carbon in actual scale, assuring the treated water quality in compliance with the Brazilian Drinking Water Standards Regulation 2914.

O objetivo desse trabalho foi investigar a degradação de 17α-etinilestradiol em solução aquosa usando um reator fotocatalítico heterogêneo em batelada com radiação ultravioleta e TiO2 como catalisador. Com a finalidade de obter as condições ideais, um planejamento fatorial 23 foi realizado com concentração inicial de 15 e 30 mg L-1, concentração de TiO2 de 0.02 e 0.05%, variou-se o pH em 5.0 e 9.0 e tempo total de reação de 240 min. O perfil da degradação e parâmetros cinéticos foram determinados com concentração inicial de 15 e 30 mg L-1, 0.02% de TiO2e pH 7.0. Com concentração inicial de 15 mg L-1 de 17α-etinilestradiol a eficiência de degradação foi 100% após 120 min independente da concentração de TiO2 e pH. Contudo menos que 50% do substrato foi degradado quando a concentração inicial utilizada era de 30 mg L-1 (0.05% TiO2e pH 5.0). A concentração inicial do substrato foi um fator limitante para a fotocatálise heterogênea. A reação também foi fortemente influenciada pela concentração de TiO2. Todas as degradações seguiram cinética de primeira ordem. Para concentração de 17α-etinilestradiol de 15 mg L-1, o tempo de meia vida (t1/2) foi 64.16 min e a constante cinética foi 0.108 min-1, enquanto para a concentração de 30 mg L-1, a degradação do poluente aconteceu em dois estágios, com valor de t1/2 de 44.71 e 433.12 min.

We investigated the degradation of 17α-ethynylestradiol in an aqueous solution using a batch heterogeneous photocatalytic (HPC) reactor with ultraviolet (UV) light and TiO2catalyst. In order to determine appropriate operating conditions, a 23factorial experiment was conducted with initial an substrate concentration of 15 or 30 mg L-1, TiO2concentration of 0.02 or 0.05%, pH of 5.0 or 9.0 and total reaction time 240 min. Degradation profiles and kinetic parameters were determined with an initial substrate concentration of 15 or 30 mg L-1, 0.02% TiO2and pH 7.0.With17α-ethynylestradiol at 15 mg L-1, degradation efficiency was 100% after 120 min independent of TiO2 concentration and pH. However, less than 50% of the substrate was degraded when the initial concentration was 30 mg L-1 (0.05% TiO2and pH 5.0). Initial substrate concentration was a limiting factor for HPC, although the reaction was also strongly influenced by TiO2 concentration and the interaction between initial substrate concentration and TiO2concentration. All degradations followed first-order kinetics. With 17α-ethynylestradiol at 15 mg L-1, the half-life time (t1/2) was 64.16 min and the rate constant was 0.108 min-1, while at 30 mg L-1, substrate degradation proceeded in two stages, the t1/2 values of which were 44.71 and 433.12 min.

O processo de digestão anaeróbia de resíduos sólidos orgânicos com baixa concentração de sólidos é realizado com substrato contendo em média cerca de 5% (percentagem em peso) de sólidos totais. Os problemas de ordem técnica associados a este tipo de tratamento, estão relacionados ao estudo das configurações de reatores que possam viabilizar uma boa eficiência de transformação do material carbonáceo em um período relativamente curto de tempo. Portanto, neste trabalho foi estudado o processo de digestão anaeróbia de resíduos sólidos orgânicos (RSO) com baixa concentração de sólidos em um reator anaeróbio compartimentado (RAC). O reator anaeróbio compartimentado tinha capacidade unitária de 2200 litros e foi operado com tempo de retenção de sólidos de 90 dias. A eficiência de transformação média de STV foi de 75% e o biogás produzido continha em média 60% de gás metano.

The process of anaerobic digestion of organic solid wastes with low concentration of solids is accomplished with substratum containing on average about 5% (percentage in weight) of total solids. The problems of technical order associated to this kind of treatment, are related to the study of the reactors configurations that can make possible a good transformation efficiency of the organic matter in a relatively short period of time. Therefore, in this work it was studied the process of anaerobic digestion of organic solid wastes with low concentration of solids in a compartmented anaerobic reactor (CAR). The compartmented anaerobic reactor had unitary capacity of 2200 liters. The reactor was fed daily with fresh organic solid wastes and with 90 days of solid retention time. The average efficiency of transformation of VTS was of 75% and the biogas produced contained on average 60% of methane gas.