Dissolved organic matter (DOM) and pH are important factors affecting heavy metal uptake by sludge particulates. Copper(II) and Nickel(II) uptake behavior by primary and secondary sludge particulates was studied under various pH and DOM conditions. A three‐variable model, incorporating effects of pH and DOM, was developed to describe heavy metal uptake. Results show that heavy metal uptake by sludge particulates can be better described by the three‐variable model than by the modified Langmuir model in a wide pH range.

A água é primordial à vida na Terra e essencial para a humanidade, porém as múltiplas e complexas atividades humanas alteram este recurso. Este estudo teve como objetivo avaliar as condições físico-químicas e bacteriológicas de água do rio Amazonas na orla de Macapá, Estado do Amapá. O estudo foi realizado em três pontos, no trecho entre a foz do igarapé das Pedrinhas e foz do canal do Jandiá, considerando as variações espaciais e temporais em períodos sazonais. Foram realizadas coletas para análise das seguintes variáveis: turbidez, oxigênio dissolvido, potencial hidrogênionico, temperatura, fósforo total, nitrato, sólidos totais, demanda bioquímica de oxigênio, coliformes termotolerantes e nitrogênio total. Para as análises estatísticas dos dados foram utilizados métodos de Estatística descritiva, teste nãoparamétrico Kruskal-Wallis e Coeficiente de variação. Os resultados obtidos foram avaliados individualmente e comparados com os limites estabelecidos pela Resolução 357/2005 do Conselho Nacional de Meio Ambiente (CONAMA), utilizando como referência "águas doces classe 2". As variáveis DBO e fósforo total apresentaram desconformidade com a resolução. Os resultados do Índice de Qualidade de Água (IQA) indicaram que a água na orla de Macapá, no período menos chuvoso e chuvoso foi classificada, como "boa" e "ótima", onde a turbidez e DBO, foram preponderantes para o decréscimo do IQA na estação menos chuvosa. Conclui-se que no período de menor vazão, o aporte de desejos lançados próximo ao posto de captação de água para o abastecimento público, pode deteriorar a qualidade da água e comprometer a saúde da população. Palavras-chave: abastecimento de água, efluentes, recursos hídricos, saneamento básico, urbanização.

The presence of dissolved organic matter (DOM) in a wastewater treatment system can significantly affect the uptake of heavy metals by sludge particulates. The characteristics of DOM, its concentration, and the solution pH are important parameters governing the heavy metals uptake reaction. The characteristics of DOM of various wastewater and sludge (primary, secondary, and tertiary) samples collected from four municipal wastewater treatment plants were investigated. Results showed that the dissolution of DOM from sludge is significantly affected by pH and suspended solids concentration. Results also showed that DOM contains two discrete acid groups that are available for metals complexation. The site concentration and acidity constants were determined by an alkalimetric titration method. For all DOM samples studied, the acidity constants, pKab and pKaB, were 5.3 and 9.5, respectively. Based on the acidity constants and the Fourier transform infrared spectra, it is believed that the acid sites consist of carboxylic and amino functional groups. The density of the first acid site was approximately 10−5 mol/mg chemical oxygen demand for all samples studied. However, the density of the second acid site varied significantly among the DOM samples investigated.

The bacterioplankton diversity of coastal waters along a latitudinal gradient between Puerto Rico and Argentina was analyzed using a total of 134,197 high-quality sequences from the V6 hypervariable region of the small-subunit ribosomal RNA gene (16S rRNA) (mean length of 60 nt). Most of the OTUs were identified into Proteobacteria, Bacteriodetes, Cyanobacteria, and Actinobacteria, corresponding to approx. 80% of the total number of sequences. The number of OTUs corresponding to species varied between 937 and 1946 in the seven locations. Proteobacteria appeared at high frequency in the seven locations. An enrichment of Cyanobacteria was observed in Puerto Rico, whereas an enrichment of Bacteroidetes was detected in the Argentinian shelf and Uruguayan coastal lagoons. The highest number of sequences of Actinobacteria and Acidobacteria were obtained in the Amazon estuary mouth. The rarefaction curves and Good coverage estimator for species diversity suggested a significant coverage, with values ranging between 92 and 97% for Good coverage. Conserved taxa corresponded to aprox. 52% of all sequences. This study suggests that human-contaminated environments may influence bacterioplankton diversity.

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