Emissions from a desktop 3D printer based on fused deposition modeling (FDM) technology were measured in a test chamber and indoor air was monitored in office settings. Ultrafine aerosol (UFA) emissions were higher while printing a standard object with polylactic acid (PLA) than with acrylonitrile butadiene styrene (ABS) polymer (2.1 × 10(9) vs. 2.4 × 10(8) particles/min). Prolonged use of the printer led to higher emission rates (factor 2 with PLA and 4 with ABS, measured after seven months of occasional use). UFA consisted mainly of volatile droplets, and some small (100-300 nm diameter) iron containing and soot-like particles were found. Emissions of inhalable and respirable dust were below the limit of detection (LOD) when measured gravimetrically, and only slightly higher than background when measured with an aerosol spectrometer. Emissions of volatile organic compounds (VOC) were in the range of 10 µg/min. Styrene accounted for more than 50% of total VOC emitted when printing with ABS; for PLA, methyl methacrylate (MMA, 37% of TVOC) was detected as the predominant compound. Two polycyclic aromatic hydrocarbons (PAH), fluoranthene and pyrene, were observed in very low amounts. All other analyzed PAH, as well as inorganic gases and metal emissions except iron (Fe) and zinc (Zn), were below the LOD or did not differ from background without printing. A single 3D print (165 min) in a large, well-ventilated office did not significantly increase the UFA and VOC concentrations, whereas these were readily detectable in a small, unventilated room, with UFA concentrations increasing by 2,000 particles/cm(3) and MMA reaching a peak of 21 µg/m(3) and still being detectable in the room even 20 hr after printing.

A new aerobic bacterium was isolated from the sediment of a freshwater pond close to a contaminated site at Amponville (France). It was enriched in a fixed-bed reactor fed with 2,6-dichlorophenol (2,6-DCP) as the sole carbon and energy source at pH 7.5 and room temperature. The degradation of 2,6-DCP followed Monod kinetics at low initial concentrations. At concentrations above 300 μM (50 mg · liter−1), 2,6-DCP increasingly inhibited its own degradation. The base sequence of the 16S ribosomal DNA allowed us to assign the bacterium to the genus Ralstonia (formerlyAlcaligenes). The substrate spectrum of the bacterium includes toluene, benzene, chlorobenzene, phenol, and all fourortho- and para-substituted mono- and dichlorophenol isomers. Substituents other than chlorine prevented degradation. The capacity to degrade 2,6-DCP was examined in two fixed-bed reactors. The microbial population grew on and completely mineralized 2,6-DCP at 2,6-DCP concentrations up to 740 μM in continuous reactor culture supplied with H2O2as an oxygen source. Lack of peroxide completely stopped further degradation of 2,6-DCP. Lowering the acid-neutralizing capacity of the medium to 1/10th the original capacity led to a decrease in the pH of the effluent from 7 to 6 and to a significant reduction in the degradation activity. A second fixed-bed reactor successfully removed low chlorophenol concentrations (20 to 26 μM) with hydraulic residence times of 8 to 30 min.

Chlorinated phenols (CP) are frequently found as harmful soil contaminants. Depending on the environment, CP may persist for extended periods of time. The influence of environmental factors on the degradation of 2,6-dichlorophenol (2,6-DCP) in unsaturated soil was examined using Ralstonia basilensis RK1 as inoculum for bioaugmentation. The disappearance of 2,6-DCP in soil microcosms was caused by bacterial mineralization. This was proved using U-14C-labeled 2,6-DCP. After 5 days of incubation, 61% of the initial activity was detected as 14CO2, while only 20% of the radioactivity remained in the soil, and 2,6-DCP was not detected. The relative importance of individual factors and possible two-factor interactions was assessed using a fractional-factorial experimental design. The following individual factors were identified as important:  2,6-DCP concentration, temperature, inoculum size, and the presence of an additional substrate. The strongest factorial interaction was observed between bacterial inoculation and 2,6-DCP concentration. For practical reasons, the influence of oxygen, organic matter, and the age of the contamination were not included in the factorial design; however, these factors were analyzed separately and found to significantly affect the biodegradation of 2,6-DCP. The findings of this study are important for the design of bioremediation techniques as well as the prediction of natural attenuation.

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