RESUMO
Manganese is the Earth's crust's third most abundant transition metal. Decades of increased mining activities worldwide have inevitably led to the release of large amounts of this metal into the environment, specifically in water resources. Up to a certain level, manganese acts as an essential micronutrient to maintain health and support the growth and development of microorganisms, plants, and animals, while above a specific limit, manganese can cause toxicity in aquatic and terrestrial ecosystems. There are conventional ways to remove manganese from water, such as chemical precipitation, sorption, and biological methods. However, other treatments have yet to be studied much, such as reverse osmosis (RO), which has demonstrated its effectiveness in the removal of heavy metals and could be a suitable alternative for manganese removal if its energy consumption is reduced. This research presents mathematical and statistical modeling of the behavior of a system in laboratory-scale RO. The principal finding was that it is possible to remove Mn using the RO operated with low pressures without decreasing the sustainable removal efficiency. Reducing the operating costs of RO opens the possibility of implementing RO in different contexts where there are problems with water contamination and economic limitations.
RESUMO
Household slow sand filter (HSSF) performance in continuous and intermittent flows was evaluated when influent water was treated with a natural coagulant extracted from Opuntia cochenillifera. The water under study, used as influent, had a turbidity of 111 ± 17.3â NTU. When clarifying the water with O. cochenillifera, the best condition obtained was 30â â mgâ L-1 in natural pH (without correction), generating clarified water with turbidity satisfactory to filters operation (7.83 ± 2.32â NTU). The results indicated a better performance of continuous flow HSSF in turbidity removal (79.2% ± 8.39%) and higher efficiency of intermittent flow HSSF in the removal of E. coli (2.86 log ± 0.79 log for 12â â h pause period and 2.41 log ± 0.42 log for 4â â h pause period). For the sake of comparison, the evaluated HSSFs had the same production (60â Lâ day-1). The impact on the interruption of the 96-h feed into the HSSFs was analysed and the results indicated a significant change in the quality of the filtered water after resuming the operation. This fragility of technology must be considered when it is implemented as lack of water can be a reality in the target communities. Acute toxicological assays with C. xanthus larvae showed no toxicity for pretreated and filtered water; however, more testing should be performed.
Assuntos
Opuntia , Purificação da Água , Escherichia coli , Filtração , AreiaRESUMO
Introdução: O conhecimento sobre a concentração de fluoreto nas águas de consumo humano é importante para a prevenção e controle da cárie e da fluorose dentária nas populações. Objetivo: Descrever as características dos estudos e os resultados por eles produzidos sobre monitoramento dos teores de fluoreto nas águas de consumo humano publicados em revistas científicas especializadas no período de 2008 a 2012. Método: Foi realizada uma revisão sistemática da literatura científica na qual foram incluídos estudos na forma de artigos que apresentassem temática centrada no monitoramento da concentração do fluoreto na água de consumo humano. Os estudos foram identificados por busca bibliográfica nas bases de dados: LILACS, PUBMED/MEDLINE e EMBASE. Artigos, com qualquer tipo de desenho metodológico, publicados nos idiomas português, inglês e espanhol, foram incluídos. Resultados: Quarenta e oito artigos foram incluídos para a extração das características e resultados referentes à pergunta da pesquisa. Conclusão: A atividade de monitoramento estava articulada à vigilância como ação do Estado em dezoito estudos (37,5%). O método eletrométrico foi usado em 39 (81%) estudos. Apenas dois estudos utilizaram o método da Alizarina, sugerindo-se o seu desuso. A classificação em categorias de tipo "adequado" e "inadequado" (dicotômica), a qual reduz as opções de interpretação e atribuição de significado às características das amostras, predominou na apresentação dos resultados.
Introduction: Knowledge on the concentration of fluoride in water for human consumption is important for the prevention and control of dental caries and dental fluorosis in populations. Objective: To describe the characteristics of the studies and the results on monitoring of fluoride levels in water for human consumption published in specialized journals in the period 2008-2012. Methods: A systematic review of the scientific literature was performed. Only articles on monitoring of fluoride concentration in drinking water were included. Studies were identified by literature searching in databases: LILACS, PUBMED / MEDLINE and EMBASE. Articles with any type of methodological design, published in Portuguese, English and Spanish were included. Results: Forty-eight articles were included for the extraction of features and results related to the research question. Conclusion: The monitoring activity was articulated to the surveillance as an action provided by the State in eighteen studies (37,5%). The electrometric method was used in 39 (81%) studies. Only two studies used the method of Alizarin, suggesting its disuse. The dichotomous categorization "appropriate" and "in appropriate" which reduces the options of interpretation and attribution of meaning to the sample characteristics predominated in the presentation of the results.