The aim of the current study is to compare the chemical oxygen demand (COD) removal efficiency of a Venturi device to that of an orifice plate. The inlet pressure in the devices was optimized and the degradation kinetics was analyzed. In addition, the synergistic effect resulting from the combination between cavitation and H₂O₂ was investigated. An experimental apparatus was built to achieve these goals. A sucrose solution and an effluent from a sucrose-based soft drink industry were treated. Results showed that the Venturi device recorded 90% COD removal efficiency after three treatment minutes. On the other hand, the orifice plate recorded 90% COD removal efficiency after 9 min. The degradation kinetics-reaction order was 3.5, except for the highest Venturi inlet pressure (7.3 bar), which led to coalescence of cavities and to reduced degradation rate. The synergistic coefficient (Sc) was 185.20 and showed that the hybrid process (HC + H₂O₂) was much more efficient than the cavitation process applied alone. The high COD concentration in the effluent generated by the soft drink industry (2,512.8 mg L^-1) was significantly decreased by 72%. The combined use of cavitation and Venturi has significant potential to remove high organic matter concentrations in short treatment periods.

Apesar de sua importância do ponto de vista social e econômico, e de serem mais protegidas que as águas superficiais, as águas subterrâneas podem ser contaminadas por diversas fontes, comprometendo sua qualidade para abastecimento e demandando alto investimento financeiro e de recursos humanos para sua remediação. Nesse contexto, o objetivo do presente estudo foi analisar a qualidade da água subterrânea em 8 (oito) poços distribuídos nos bairros da cidade de Uberaba-MG e avaliar o risco à saúde com base na concentração de metais potencialmente tóxicos e de íons nitrato. Os parâmetros analisados na estação seca e chuvosa foram de caráter microbiológico (Coliformes totais e termotolerantes), físico (condutividade, temperatura, turbidez e cor) e químico (pH, metais potencialmente tóxicos, alcalinidade, demanda química de oxigênio, fósforo total, nitrato, cloreto e dureza). Todos os poços analisados apresentaram coliformes totais e termotolerantes em pelo menos uma estação. Ao comparar com a legislação vigente, os parâmetros cor, DQO, fósforo total, ferro, cádmio, chumbo, níquel, manganês e cromo apresentaram valores acima dos limites permitidos, principalmente no período seco. A análise de risco à saúde mostrou-se significativa para quatro poços estudados, sendo cádmio o parâmetro com os maiores coeficientes de risco, seguido por cromo. Essas alterações precisam ser constantemente monitoradas a fim de conhecer a real qualidade da água subterrânea para consumo. Assim, os resultados encontrados contribuem para o delineamento de estudos futuros, servindo como subsídio para gestores ambientais e de saúde pública.

The presence of natural organic matter (NOM) in water does not present direct risk to the human body or to the environment. However, its presence along with other pollutants can lead to countless issues and damage human health and the environment. The hydrodynamic cavitation (HC) phenomenon started being used in the early 21st century as a process capable of treating supply-water and wastewater based on pollutant and pathogen degradation. Process effectiveness increases when it is combined to chemical agents, creating an advanced oxidation process (AOP). Although several studies have presented broaden applications for the HC process, its use for NOM removal from supply-water was not yet assessed; therefore, it remains a gap in scientific knowledge. The aim of the current study is to assess HC potential in NOM removal. In order to do so, the experiments were carried out in bench scale hydrodynamic cavitation system operated at batch model within 15-min duration period-of-time. In addition, decantation experiments (24-h period-of-time) were performed in order to check HC influence on molecules found in reaction medium after the exposure of NOM to the phenomenon. NOM was produced by a synthetic humic acid (HA) matrix at fixed concentration of 100 ppm. In total, 16 experiments were carried out; each experiment was featured by the following pair: pH (2.6, 3.0, 3.5 and 5.5) and hydrogen peroxide (0, 1, 5 and 30 mL). The best removal efficiencies (34%-36%) were observed in the most acidic pH ranges (2.6-3.0) at H2O2 concentration of 15mL. Results have presented high NOM removal efficiency (approximately 90%) after decantation at the most acidic pH ranges, as well. It can be explained by the fact that hydrodynamic cavitation in acid solution can break molecular structures suspended in the liquid medium, which favors decantation. Based on the present study, hydrodynamic cavitation with hydrogen peroxide addition can remove NOM from water; moreover, pH control is an essential factor for process development.

Air quality monitoring by automatic stations, although efficient, does not allow evaluating the effects of pollution on living organisms and communities. Thus, the aim of the present study was to use lichens of the Parmotrema tinctorum species in active air quality biomonitoring. We used a new methodology of chlorosis area analyses in QGis software, as low-cost and complementary tool to physicochemical methods. Samples of the aforementioned species were exposed to atmospheric pollution for 30 consecutive days in the dry and rainy seasons, in urban and industrial regions. The chlorosis rate (34% of the lichen thalli, on average) and the accumulation of sulfur (1.1 g.kg-1, on average) were higher in the samples of lichens exposed in the industrial region, in the dry season. There was a moderate-to-high positive correlation between chlorosis rate and lichen content of nitrogen, sulfur, iron and zinc, in the dry season, mainly with sulfur (r = 0.71). The results confirmed the sensitive of P. tinctorum to atmospheric pollution, even after a short exposure time. Such new active biomonitoring methodology (chlorosis analysis in the QGis) can be used in future studies of air quality assessment by environmental and health surveillance managers.