The effect of continuous Zn (II) exposure on the organic degradation capability and soluble microbial products (SMP) of activated sludge.

This study describes the change of organic degradation capability and soluble microbial products (SMP) generated in activated sludge under continuous exposure to Zn (II) in a sequencing batch reactor (SBR). In 338 days of operation, the added Zn (II) concentrations were gradually increased from 50 to 100, 200, 400 to 600 and 800 mg/L. Results showed that after adaptation, the activated sludge could endure 400mg/L Zn (II) without showing evident reduction in organic degradation ability (92±1% of chemical oxygen demand (COD) removal in stable state). However, when 600 and 800 mg/L Zn (II) were applied, the effluent water quality significantly deteriorated. Meanwhile, under increasing Zn (II) concentrations, the SMP content in the activated sludge, together with its main biochemical constituents, first increased slightly below 400mg/L of Zn (II), then rose sharply under 600 and 800 mg/L Zn (II). Furthermore, a close correlation was found between SMP content and effluent soluble COD in both the Experimental Reactor and Control Reactor. In addition, the Zn (II) concentrations in the effluent and SMP extraction liquid were further analyzed and discussed to reveal the role that SMP constituents played in defense and resistance to the toxicity of Zn (II).

[FTIR and XRD analysis of hydroxyapatite from fossil human and animal teeth in Jinsha Relict, Chengdu].

Diagenetic effect during burial on the hydroxyapatite in enamel and dentin from fossil human and animal teeth was examined, using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). For the enamel and dentin of all fossil teeth, XRD patterns exhibit bulge line and overlap between major reflections of hydroxyapatite, and the crystallinity of hydroxyapatite is low. For each infrared spectrum, H2O and OH(-) have distinct peaks of absorbance, and PO4(3-) and CO3(2-) ions have intensive infrared vibration modes at the fundamental wave numbers. The component of hydroxyapatite of all fossil teeth is similar to the modern biological hydroxyapatite. Furthermore, the index (PCI) which reflects the hydroxyapatite crystallinity of each sample ranges from 2.4 to 4.0 while the index (BPI) reflecting the amount of type B carbonate to phosphate indicates that the values of CO3(2-) content in hydroxyapatite are rather high, accordingly the crystallinity of all fossil hydroxyapatites are poor. It could be concluded that little alteration of hydroxyapatites from fossil human and animal teeth occurred in the process of diagenesis in Jinsha Relict, Chengdu, China.