RESUMO
In sewage treatment plants, physicochemical parameters are highly controlled since treated sewage can be returned to water bodies or reused. In addition, pollutants such as heavy metals also deserve attention due to their potential toxicity. In general, these characteristics of sewage and treated water are evaluated independently, with the support of Brazilian legislation that does not require a routine for the analysis of metals as frequent as for the physicochemical parameters. In this work, 66 samples of raw sewage, treated sewage, and effluents from two treatment plants in the city of Bauru, São Paulo, Brazil, were evaluated to assess the efficiency of the treatment plants in the removal of metals. In addition, the influence of these pollutants on the quantification of physicochemical parameters was evaluated. The quantification of metals was performed using inductively coupled plasma optical spectroscopy (ICP-OES), and Spearman's test was applied to evaluate correlation between physicochemical parameters and metal content. The main metals found in the samples were Ba, Mn, Zn, Cu, Se, Fe, and Al. The results indicate that concentrations of metals in the aquatic environment can significantly affect the physicochemical parameters, since high concentrations of metals can interfere mainly in the pH, chemical oxygen demand, and dissolved oxygen.
Assuntos
Metais Pesados/análise , Esgotos/química , Eliminação de Resíduos Líquidos , Brasil , Monitoramento Ambiental , Esgotos/análise , Purificação da ÁguaRESUMO
Community on-site separation of wastewater is a treatment approach that leads to more efficient processes. Black water has high organic matter content and can be a suitable feedstock for anaerobic treatment systems. Biological methane production (BMP) tests were conducted using Plackett-Burman design to screen the effects of adding Fe, Ni, Cu, Co, Mn, Ba and Se, with simulated black water (SBW) as the substrate. In the inoculum, most metals were found mainly in the organic matter/sulfide and residual fractions except for Mn, which was present at 12.3% in the bioavailable fractions (exchangeable and carbonates), and Ba, which was evenly distributed among all the fractions. Ba had a significant negative effect on methane production and Mn addition enhanced the toxic effect. A specific methanogenic activity (SMA) between 18% and 27% lower than the control, was predicted at a total Ba concentration of approximately 1000-1200â mgâ L-1. Similar SMA was predicted at Ba concentration between 400 and 600â mgâ L-1 when 0.55â mgâ L-1 of Mn is added. Se and Cu additions demonstrate the potential to improve the methane production from SBW. The SMA was predicted to reach 12â mLCH4â gCOD-1â d-1 when Cu and Se are supplied at total concentrations of 3.0â mgâ L-1 and 0.98â mgâ L-1, respectively.