Bioremediation of Crude Glycerol by a Sustainable Organic-Microbe Hybrid System.

Klebsiella pneumoniae with crude glycerol-utilizing and hydrogen (H2)-producing abilities was successfully isolated from return activated sludge from Shatin Sewage Treatment Works. The H2 production strategy used in this study was optimized with crude glycerol concentrations, and 1,020 µmol of H2 was generated in 3 h. An organic-microbe hybrid system was constructed with metal-free hydrothermal carbonation carbon (HTCC) microspheres to enhance the H2 production under visible light (VL) irradiation. Under optimized VL intensity and HTCC concentration, an elevation of 35.3% in H2 production can be obtained. Electron scavenger study revealed that the photogenerated electrons (e-) from HTCC contributed to the additional H2 production. The variation in intercellular intermediates, enzymatic activity, and reducing equivalents also suggested that the photogenerated e- interacted with K. pneumoniae cells to direct the metabolic flux toward H2 production. This study demonstrated the feasibility of using an organic-microbe hybrid system as a waste-to-energy technology.

Integrated photocatalytic-biological treatment of triazine-containing pollutants.

The degradation of triazine-containing pollutants including simazine, Irgarol® 1051 and Reactive Brilliant Red K-2G (K-2G) by photocatalytic treatment was investigated. The effects of titanium dioxide (TiO2) concentration, initial pH of reaction mixture, irradiation time and ultraviolet (UV) intensity on photocatalytic treatment efficiency were examined. Complete decolorization of K-2G was observed at 60 min photodegradation while only 15 min were required to completely degrade simazine and Irgarol® 1051 under respective optimized conditions. High-performance liquid chromatography (HPLC), gas chromatography/mass spectrometry (GC/MS) and ion chromatography (IC) were employed to identify the photocatalytic degradation intermediates and products. Dealkylated intermediates of simazine, deisopropylatrazine and deethyldeisopropylatrazine, and Irgarol® 1051 were detected by GC/MS in the initial phase of degradation. Complete mineralization could not be achieved for all triazine-containing pollutants even after prolonged (>72 h) UV irradiation due to the presence of a photocatalysis-resistant end product, cyanuric acid (CA). The toxicities of different compounds before and after photocatalytic treatment were also monitored by three bioassays. To further treat the photocatalysis-resistant end product, a CA-degrading bacterium was isolated from polluted marine sediment and further identified as Klebsiella pneumoniae by comparing the substrate utilization pattern (Biolog™ microplate), fatty acid composition and 16S rRNA gene sequencing. K. pneumoniae efficiently utilized CA from 1 to 2000 mg/L as a good nitrogen source and complete mineralization of CA was observed within 24 h of incubation. This study demonstrates that the biodegradability of triazine-containing pollutants was significantly improved by the photocatalytic pre-treatment, and this proposed photocatalytic-biological integrated system can effectively treat various classes of triazine-containing pollutants.