Efficiency of selected wastewater treatment processes in removing estrogen compounds and reducing estrogenic activity using the T47D-KBLUC reporter gene assay.

The occurrence of endocrine-disrupting compounds (EDCs) consisting of natural and synthetic estrogens, namely estrone (E1), 17ß-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2) was quantified in wastewater samples. The aim of this study was to assess the removal efficiency for the selected estrogens (E1, E2, E3 and EE2) and reduction of estrogenic activity in wastewater samples from wastewater treatment plants (WWTPs) using different processes. Solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were used to quantify the selected estrogens in wastewater samples. Estrogenic activity was assessed using the T47D-KBluc gene reporter assay. Results revealed a decrease in estrogen concentrations observed in the effluents of all the WWTPs, except for E2 at Daspoort where no removal was noted. In general, the highest removal for total estrogens was observed at Phola (84%) combining three processes (AP, BF and wetland). The AS at Daspoort had a highest removal of 75% for E3; while at Zeekoegat the highest removal reached 61% for EE2. The PST at Daspoort had no removal recorded for all the compounds, except for the EE2 (33%). The AP and BF systems at Phola contributed to a higher removal of selected compounds. Downstream of the wetland at Phola no removal was recorded for E3; while the highest removal reached 61% for E1. The best performance in terms of the overall influent-to-effluent removal efficiency was observed at Phola WWTP, where E1 removal of 85% was recorded. The highest estrogenic activity in the effluent was reported at Phola, with an average estradiol equivalent (EEQ) value of 6.3 ± 6.7 ng/L. However, no anti-estrogenic activity was detected in any of the samples. The daily mass load discharged from the effluent of the three WWTPs was higher for E1 recorded at Zeekoegat (8002.3 ± 6416.3 mg/d), followed by Daspoort (3509.8 ± 849.0 mg/d) and finally Phola (176.1 ± 34.9).

Microbial diversity of Emalahleni mine water in South Africa and tolerance ability of the predominant organism to vanadium and nickel.

The present study aims firstly at determining the microbial diversity of mine-water collected in Emalahleni, South Africa and secondly isolating and characterizing the most dominant bacterial species found in the mine water in terms of its resistance to both V(5+) and Ni(2+) in a modified wastewater liquid media. The results revealed a microbial diversity of 17 orders, 27 families and 33 genera were found in the mine-water samples with Marinobacteria (47.02%) and Anabaena (17.66%) being the most abundant genera. Considering their abundance in the mine-water samples, a species of the Marinobacter genera was isolated, identified, and characterised for metal tolerance and removal ability. The MWI-1 isolate (Marinobacter sp. MWI-1 [AB793286]) was found to be closely related to Marinobacter goseongensis at 97% of similarity. The isolate was exposed to various concentrations of Ni(2+) and V(5+) in wastewater liquid media and its tolerance to metals was also assessed. The MWI-1 isolate could tolerate V(5+) and Ni(2+) separately at concentrations (in terms of MIC) up to 13.41 ± 0.56 mM and 5.39 ± 0.5 mM at pH 7, whereas at pH 3, the tolerance limit decrease to 11.45 ± 0.57 mM and 2.67 ± 0.1 mM, respectively. The removal of V(5+) and Ni(2+) in liquid media was noted to gradually decrease with a gradual increase of the test metals. A significant difference (p<0.05) between V(5+) and Ni(2+) removal was noted. Marinobacter sp. MWI-1 achieved the maximum permissible limit of 0.1 mg-V(5+)/L prescribed by UN-FAO at 100 mg/L, while at 200 mg/L only V(5+) was removed at approximately 95% and Ni(2+) at 47%. This study suggests that mine-water indigenous microorganisms are the best solution for the remediation of polluted mine water.

Microwave-assisted synthesis, characterization and antibacterial activity of Ag/ZnO nanoparticles supported bentonite clay.

Composites of silver-zinc oxide nanoparticles supported on bentonite clay were synthesized by the microwave-assisted synthesis method for use as an antibacterial material. Silver nitrate was used as the precursor of silver nanoparticles while zinc oxide nanoparticles were commercially sourced. The composites were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared (FTIR) and BET surface area measurements. XRD spectra showed peaks of silver confirming the formation of the silver and not of the silver nitrate or any other impurity of the metal. Meanwhile TEM confirmed the formation of silver and zinc oxide nanoparticles on the clay layers, with particle sizes ranging from 9-30 nm and 15-70 nm, respectively. The antibacterial activities of the composites were evaluated against Gram negative Escherichia coli bacteria and Gram positive Enterococcus faecalis bacteria by the disc diffusion method. Whereas both composites of Ag-clay and ZnO-clay showed good antibacterial activity against bacteria, a better antibacterial activity was observed with Ag/ZnO-clay composite. The results therefore reveal that Ag/ZnO-clay composite is a promising bactericide that can be used for deactivating microbes in water.

Breakthrough analysis for water disinfection using silver nanoparticles coated resin beads in fixed-bed column.

This study demonstrates the use of silver nanoparticles coated resin beads in deactivating microbes in drinking water in a column filtration system. The coated resin beads are characterized using X-ray diffraction (XRD), Fourier transform infra-red (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) to confirm the functional groups, morphology and the presence of silver nanoparticles on the surface of the resin. The performance of the coated resin is evaluated as a function of bed mass, initial bacterial concentration and flow rate using Escherichia coli as model microbial contaminant in water. The survival curves of E. coli are expressed as breakthrough curves (BTCs), which are modeled using sigmoidal regression equations to obtain relevant rate parameters. The number of bed volumes processed at breakthrough point and capacity of the bed are used as performance indicators. Results show that performance increases with a decrease in initial bacterial concentration, an increase in flow rate and an increase in bed mass.