Mass loading and emission of thirty-seven pharmaceuticals in a typical municipal wastewater treatment plant in Hunan Province, Southern China.

The occurrence, fate, mass loading and environmental emission of 37 pharmaceuticals were studied through an integrated approach involving both dissolved and adsorbed phase at a typical wastewater treatment plant in Hunan Province, Southern China. The results displayed the prevalence of 24 and 23 compounds in dissolved phase of influent and effluent, respectively. Fourteen compounds were found adsorbed onto sludge with a mean concentration ranging from 0.85 to 2900µg/kg dry weight. Twelve compounds exhibited high adsorption potential onto suspended particulate matter (SPM) with a mean fraction ranging from 8.8% (trimethoprim) to 97% (tetracycline). Furthermore, SPM showed a diverse absorbability in influent and effluent water circumstance. The overall elimination varied from -16% for lincomycin to 99% for paracetamol, while macrolides were able to withstand the whole treatment process. Mass balance analysis indicated that degradation was the predominant removal pathway for most compounds, and adsorption onto sludge combined with a minor portion of degradation explained for the reduction of tetracyclines and fluoroquinolones, whereas macrolides were recalcitrant to both two processes. The total mass loading was estimated to be up to 2800mg/d/1000 inhabitants and most compounds exhibited lower or comparable level comparing to the global published data. The total environmental emission was estimated up to be 1000mg/d/1000 inhabitants, and a value of 650mg/d/1000 inhabitants was obtained when considering merely the dissolved phase. This work would be helpful for the better understanding of ultimate fate and real pollution of pharmaceuticals in the water environment.

Development of ultrasound-assisted emulsification microextraction based on solidification of a floating organic droplet for determination of organochlorine pesticides in water samples.

An ultrasound-assisted emulsification microextraction based on the solidification of a floating organic droplet followed by gas chromatography with electron capture detection was developed for the simultaneous determination of 13 organochlorine pesticides in water samples. In the proposed method, ultrasound was applied to achieve the emulsification without addition of any dispersive solvent. In consequence, the volume of extraction phase remained unaffected by the ion strength of aqueous phase and high extraction recoveries were obtained. It was also found that dilution of the floating phase with acetone was necessary for preventing peak splitting in chromatogram. Under optimal conditions, the proposed method provided good sensitivity (the detection limits of organochlorine pesticides ranged from 1.3 to 3.9 ng/L) and good repeatability of extraction (below 6.5%, n = 5). The recoveries in reservoir and river water samples were between 75.8% and 96.9%.

Speciation and determination of bioavailable arsenic species in soil samples by one-step solvent extraction and high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

A new analytical method was developed to determine the bioavailable arsenic species (arsenite, arsenate, monomethylarsonic acid, and dimethylarsonic acid) in soil samples using high-performance liquid chromatography with inductively coupled plasma mass spectrometry. Bioavailable arsenic was extracted with ammonium phosphate buffer by a simplified one-step solvent extraction procedure. To estimate the effect of variables on arsenic extraction, a two-level Plackett-Burman factorial design was conducted to screen the significant factors that were further investigated by a separate univariate approach. The optimum conditions were confirmed by compromising the stability of arsenic species and the extraction efficiency. The concentration of arsenic species was determined in method blank and soil-certified reference materials both spiked with standard solutions of arsenic species. All the target arsenic species were stable during the whole extraction procedure. Furthermore, the proposed method was applied to release bioavailable arsenic from contaminated soil samples, showing that the major arsenic species in soil samples were inorganic arsenic: arsenite and arsenate, of which the latter was dominant.

A dual membrane UF/RO process for reclamation of spent rinses from a nickel-plating operation--a case study.

The objective of this work was to conduct treatability studies on rinse wastewater from process lines of a typical nickel-plating plant for reuse. The study comprised of three steps: (1) a plant process review and the treatability of different combinations of simulated spent rinses in the laboratory; (2) a variability monitoring of a combined rinse at the plant and a treatability study on a combined rinse in the laboratory; (3) a pilot study for reclamation of the combined rinse on site. The study established an optimum dual membrane ultrafiltration (UF)/reverse osmosis (RO) process for treating a combined liquor of spent alkaline, acidic and nickel-plating rinses which resulted in a treated water of a quality suitable for reuse as substitute for town water for the purpose of rinsing. The results of this study provided a good guide to the selection of a UF pretreatment combined with an RO membrane unit as the treatment system. The pilot plant had successfully operated for 6 months, consistently producing a high quality product water (< 95 microS cm-1) at an overall water recovery of 67.5%. The quality of reclaimed water was better than town water used at the factory. The product water from the pilot plant has been used as substitute of town water for in-process rinsing at the factory with no detrimental effects for 3 months.