RESUMEN
Fuel station run-off (FSR) and carwash wastewater (CWW) are potential sources of heavy metals contamination in surface waters. High levels of heavy metals can have dire consequences on the ecosystem in receiving waterbodies. Ghanaians demand (and supply) of fuel and vehicle cleaning services has increased sharply with population and economic growth and the trend will continue. In this study, a microwave plasma atomic emission spectrometer was used to analyze the levels of Cr, Cu, Ni, Pb, and Zn in CWW and FSR from ten fuel stations and ten carwash facilities in the Oforikrom and Ejisu Municipalities in the Ashanti Region of Ghana. An experimental sand filter bed augmented with charcoal was used to treat the CWW and FSR. The efficacy of the treatment and the potential ecological risk posed by the untreated CWW and FSR were assessed using single- (contamination factor, CF) and multi-element ecological risk indicators (potential ecological risk index, PERI). The findings showed that CWW contained 0.07 mg/L Cr, 0.20 mg/L Cu, 0.02 mg/L Ni, 1.16 mg/L Pb, and 0.58 mg/L of Zn, while, FSR contained 0.05 mg/L Cr, 0.09 mg/L Cu, 0.17 mg/L Ni, 0.31 mg/L Pb, and 0.18 mg/L Zn. Copper levels in CWW and FSR were positively correlated (0.8), suggesting similar sources of contamination. CF revealed that Cr, Cu, Ni, and Zn in CWW and FSR posed low to medium risk, while Pb posed high risk. The PERI also ranked Pb in all samples as extreme pollution, and Ni as severe pollution in FSR. The charcoal augmented sand filter effectively removed Pb (96%), Cu (61%), and Zn (79%) in both CWW and FSR. Therefore, Ghana EPA and Department of Urban Planning policies should include the construction of a charcoal-augmented sand filtration system at FS and CW facilities to intercept and treat wastewater and run-off before discharge.
RESUMEN
The removal of EDCs in activated sludge processes can be enhanced by increasing solid and hydraulic retention times (SRT and HRT); it has been suggested that the improvement in removal is due to changes in microbial community structure (MCS). Though the influence of SRT and HRT on chemical removal and MCS has been studied in isolation, their synergistic impact on MCS and the removal of estrogens and nonylphenols in activated sludge remains unknown. Hence, we investigated how both parameters influence MCS in activated sludge processes and their ulterior effect on EDC removal. In our study, an activated sludge pilot-plant was fed with domestic sewage fortified with 100 and 1000 ng/L nonylphenols or 2 and 15 ng/L estrogens and operated at 3, 10 and 27 d SRT (constant HRT) and at 8, 16 and 24 h HRT (constant SRT). The MCS was assessed by phospholipid fatty acids (PLFA) analysis, and the archaeal and bacterial diversities were determined by 16S rRNA analysis. From the PLFA, the microbial abundance ranked as follows: Gram-negative > fungi > Gram-positive > actinomycetes whilst 16S rRNA analysis revealed Proteobacteria > Bacteroidetes > Others. Both PLFA and 16S rRNA analysis detected changes in MCS as SRT and HRT were increased. An SRT increment from 3 to 10 d resulted in higher estrone (E1) removal from 19 to 93% and nonylphenol-4-exthoxylate (NP4EO) from 44 to 73%. These findings demonstrate that EDC-removal in activated sludge plants can be optimised where longer SRT (>10 d) and HRT (>8 h) are suitable. We have also demonstrated that PLFA can be used for routine monitoring of changes in MCS in activated sludge plants.
RESUMEN
Anaerobic treatment of municipal wastewater offers the prospect of a new paradigm by reducing aeration costs and minimizing sludge production. It has been successfully applied in warm climates, but does not always achieve the desired outcomes in temperate climates at the biochemical oxygen demand (BOD) values of municipal crude wastewater. Recently the concept of 'fortification' has been proposed to increase organic strength and has been demonstrated at the laboratory and pilot scale treating municipal wastewater at temperatures of 10-17°C. The process treats a proportion of the flow anaerobically by combining it with primary sludge from the residual flow and then polishing it to a high effluent standard aerobically. Energy consumption is reduced as is sludge production. However, no new treatment process is viable if it only addresses the problems of traditional pollutants (suspended solids - SS, BOD, nitrogen - N and phosphorus - P); it must also treat hazardous substances. This study compared three potential municipal anaerobic treatment regimes, crude wastewater in an expanded granular sludge blanket (EGSB) reactor, fortified crude wastewater in an EGSB and crude wastewater in an anaerobic membrane bioreactor. The benefits of fortification were demonstrated for the removal of SS, BOD, N and P. These three systems were further challenged with the removal of steroid estrogens at environmental concentrations from natural indigenous sources. All three systems removed these compounds to a significant degree, confirming that estrogen removal is not restricted to highly aerobic autotrophs, or aerobic heterotrophs, but is also a faculty of anaerobic bacteria.
