Challenges for bathing in rivers in terms of compliance with coliform standards. Case study in a large urbanized basin (das Velhas River, Brazil).

This paper presents a case study on the prospects of bathing in a large water course (das Velhas River, Brazil), which crosses the important metropolitan region of Belo Horizonte (25 municipalities), receiving several point and diffuse discharges. The studies were carried out based on a mathematical simulation of thermotolerant coliforms over 227 km of the river, using an adaptation of the Qual2E model (model Qual-UFMG). Simulations of intervention scenarios were made for the current conditions, with three reference flows for the das Velhas River, tributaries and direct contribution: Q7,10 (representative of low-flow conditions), Q50 (average conditions) and Q10 (rainy season). The intervention scenarios simulated were: (a) current conditions without intervention; (b) scenario with effluent disinfection in the two largest wastewater treatment plants in the basin (around 2.4 million inhabitants); (c) scenario with 95% sewage collection and treatment, with disinfection in all municipalities of the study area; (d) scenario with the calculation of values required for the coverage of sewage treatment and coliform removal efficiencies based on a mathematical optimization process. The monitoring data and results of all simulations indicated improvement in coliform concentration as the river flows downstream. However, results suggested that disinfection per se is not enough. Even under hypothetical conditions of excellent sanitary infrastructure for a developing country, coverage of collection and treatment of 95% of the generated sewage, and treatment with disinfection at all wastewater treatment plants, concentrations of thermotolerant coliforms in das Velhas River are likely to be above the maximum allowable of 1,000 MPN/100 mL for bathing purposes. The mathematical optimization indicated the need for very high percentages of sewage treatment coverage (near 100%, i.e. universality of collection and treatment) and implementation of disinfection in most treatment plants in the basin, and highlighted the fact that both items play equally important roles.

Association between biotic and abiotic parameters and the occurrence of cyanobacteria in a Brazilian reservoir.

The water reservoir of Vargem das Flores, Brazil, has been subject to eutrophication problems. The occurrence of cyanobacterial blooms in this water body has raised concerns regarding the presence of toxic metabolites. In order to understand the factors that promote the proliferation and distribution of cyanobacteria in the reservoir, physicochemical parameters, species composition, and toxicity of the reservoir water column were analyzed at monthly intervals over a 3-year period (2004-2007) using a range of analytical techniques. The results showed that cyanobacteria were absent in the dry period, returning after the onset of stratification. A succession pattern was observed within this group. The Aphanocapsa genus was dominant in the last rainy period of the study (October 2006 to March 2007). However toxicity was only detected when the genera Microcystis and Sphaerocavum were present (October 2005). The principal components analysis showed negative correlation between cyanobacteria and orthophosphate. The change of dominant cyanobacteria along the 3 years of study and the final prevalence of nontoxic genera in the reservoir is an evidence of water quality improvement in response to the management techniques implemented in the reservoir basin.

Emissão de gases de efeito estufa no ciclo de vida do etanol: estimativa nas fases de agricultura e industrialização em Minas Gerais / Greenhouse gas emissions in the life cycle of ethanol: estimation in agriculture and industrialization stages in Minas Gerais, Brazil

O presente estudo apresenta uma estimativa da emissão de gases de efeito estufa (CO2, CH4 e N2O) nas etapas de agricultura e industrialização de cana-de-açúcar para produção de etanol em usinas localizadas no Estado de Minas Gerais. Princípios de Avaliação do Ciclo de Vida foram considerados na quantificação das emissões. Consideraram-se as emissões no consumo de combustíveis, utilização de insumos da agricultura, liberação de N2O no solo, emissões na queima da cana-de-açúcar e utilização de produtos químicos em 11 destilarias. Os resultados mostram uma emissão total de 1.539,60 kg CO2eq/ha·ano, com maior proporção para as emissões decorrentes da queima de cana-de-açúcar e consumo de combustíveis, os quais, em conjunto, representam mais de 50 por cento do total de emissões.

This research presents an estimate of greenhouse gas emissions (CO2, CH4 e N2O) in the stages of agriculture and sugarcane industrialization for the production of ethanol in mills located in the state of Minas Gerais, Brazil. Life Cycle Assessment principles were considered in the quantification of emissions. The use of fuels, agricultural inputs, N2O emissions on soil, sugarcane burning emissions and use of chemical products of 11 mills were considered in this study. The results show a total emission of 1,539.60 kg CO2eq/ha·year, considering as the main key sources: sugarcane burning and use of fuels, which account for more than 50 percent of the total emissions.

Qualidade da água durante a formação de lagos profundos em cavas de mineração: estudo de caso do lago de Aguas Claras, MG / Water quality during the filling of deep mining lakes: case study of Aguas Claras pit lake, MG

O trabalho apresenta os resultados do monitoramento de qualidade da água durante o processo inicial de formação do Lago de Aguas Claras, cuja gênese é decorrente do enchimento da cava exaurida de uma mineração de ferro. Em sua configuração final o lago possuirá uma área de 0,7 km² e uma profundidade máxima de 234 m, o que o posicionaria atualmente como o ambiente hídrico mais profundo do país. Constata-se o predomínio de uma boa qualidade de água, com baixo grau de mineralização, excelentes condições de oxigenação e ausência de contaminação orgânica e mineral. No aspecto hidrobiológico destaca-se a frequente alternância no predomínio de grupos algais, indicando a instabilidade de ecossistemas que se encontram em processo de formação.

The paper presents the results of a broad monitoring program carried out during the beginning of the filling process of Lake Aguas Claras, Brazil. This lake was created after the exhaustion of an iron ore mining activity. In its final conformation the lake will have a surface area of 0,7 km² and the maximum depth of 234 m, which will make it the deepest lake in the country. The results of a two years monitoring program show the prevalence of good water quality (well oxygenated, low degree of mineralization, absence of organic and mineral contamination), but also a quite interesting shift in the dominance of phytoplanktonic groups, indicating the high instability of lakes that are undergoing a process of formation.