Macromolecular composition and anaerobic degradation of the sludge produced in a sequencing batch reactor

The effect of sequencing batch reactor (SBR) operating conditions on sludge macromolecular composition and the effect of sludge macromolecular composition on the anaerobic degradation of the sludge produced in SBR was investigated in this work. A SBR, fed with synthetic wastewater, was operated at different air flow rates. The resulting sludge was analyzed in terms of protein, carbohydrate, phospholipid and polyhydroxybutyrate concentrations. Methane production during anaerobic digestion of the sludge was also measured. Ammonium, nitrite, nitrate, dissolved oxygen and chemical oxygen demand (COD) track studies in the SBR were carried out in order to relate SBR performance and sludge macromolecular composition. The lowest air flow rate at which the SBR was operated was 2 l min-1, in which case the dissolved oxygen concentration was lower than 0.5 mg l-1 in the SBR and partial denitrification occurred during the feeding phase. An increased air flow rate caused a decrease in protein concentration, as well as an increase in carbohydrate concentration. Polyhydroxybutyrate (PHB) concentration in the sludge was independent of air flow rate. At different air flows, the methane production rates were similar, but the total volume of methane was greater during anaerobic digestion of the sludge produced at low air flow rates. These results indicate a strategy by which changes in sludge composition can optimize the operation of anaerobic sludge digesters.

Production and recovery process of polyhydroxybutyrate (PHB) from waste activated sludge.

Polyhydroxybutyrate (PHB) is bacterial storage polyester, currently receiving much attention because of its biodegradable potential. Production of microbial polymers is expensive due to supplementary carbon source and downstream processing cost. The present study aimed at reducing the fermentation carbon source cost by using waste activated sludge and wastewater, and evaluating the use of proper solvent for the recovery of PHB from activated sludge to minimize the downstream cost. To improve the recovery process efficiency, different strategies for the extraction and recovery of the polymer from the waste activated sludge were applied. The maximum solubility of PHB (80%) was observed in chloroform, and precipitation with methanol (95%) was observed. Impurities interference in the PHB recovery process was also studied. By using these optimized recovery processes with optimized C:N ratio 10, the maximum product recovery was observed to be 62.3% (w/w). The results are presented and discussed in this paper.

Study on appraisement and determination GHB levels in hair / 法医学杂志

OBJECTIVE@#The possibility for the identification of GHB administration through hair analysis was investigated to provide method and information for toxicology examination of GHB. METHODS A GC/MS assay for GHB in hair was developed. Endogenous levels of GHB in hair, time course of GHB in hair, relationship between GHB levels in hair and hair color or administration dose were also established by guinea pig model.@*RESULTS@#Endogenous levels of GHB in guinea pig black hair and human black hair were (3.01 +/- 1.41) ng/mg (n=28) and (1.02 +/- 0.27) ng/mg (n=20), respectively. GHB levels in black hair were increased by GHB administration and related with drug dosage, and also much higher than in brown and white hair.@*CONCLUSION@#Analysis of GHB in hair is suitable for investigation of GHB abuse in forensic toxicology and GHB level in segmental analysis compared with endogenous level of GHB may provide useful information about GHB administration.

Surface properties and microporosity of polyhydroxybutyrate under scanning electron microscopy

This study was designed to investigate the surface properties especially surface porosity of polyhydroxybutyrate (PHB) using scanning electron microscopy. PHB granules were sprinkled on the double-sided sticky tape attached on a SEM aluminium stub and sputtered with gold(10nm thickness) in a Polaron SC515 Coater, following which the samples were placed into the SEM specimen chamber for viewing and recording. Scanning electron micrographs with different magnification of PHB surface revealed multiple pores with different sizes.