In this study, kaolinite from a lead-zinc mining district, which was spiked with cadmium, has been treated by electrokinetics to investigate effects of treatment time and applied voltage gradient. The results showed that the increased test duration had induced a higher removal rate of cadmium. Being treated for 7 days, cadmium was removed from kaolinite dramatically. It was also found that higher removal rate happened when a higher voltage gradient was applied and cadmium accumulated near the cathode because pH increased. Increase of pH near the cathode caused accumulation of cadmium. Moreover, it was observed that cation exchange membrane which was placed between kaolinite and cathode could make pH lower than the initial value and avoid the higher pH near the cathode. As a result, the high concentration accumulation of cadmium near the cathode was avoided.

Phosphorus removal performance in an aerobic/aerobic sequencing batch reactor (SBR) supplied with glucose as carbon source was investigated. It was found that there was no phosphate release concomitant with the storing of poly-β-hydroxyalkanoate (PHA) during the anaerobic phase. Whereas, glycogen was soon built up followed by rapid consumption, at the same time, glucose was depleted rapidly. Based on the analysis of different fractions of phosphorus in activated sludge, the relative ratio of organically bound phosphorus in sludge changed at the end of anaerobic and aerobic phases. The ratios were 45.3% and 51.8% respectively. This showed that the polyphosphate broke down during the anaerobic phase to supply part of energy for PHA synthesis. The reason why there was no phosphate release might be the biosorption effect of extracellular exopolymers (EPS). It was also proved by the analysis of EPS with scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). The phosphorus weight percentage of EPS at the end of anaerobic phase was 9.22%.

To investigate the microbial communities of phosphate-accumulating organisms (PAOs) cultivated under different carbon sources, three sequencing batch reactors were operated supplied with sewage, glucose and sodium acetate as carbon sources respectively. The results of denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified 16S rDNA fragments demonstrated that β-protebacteria, Actinomyces sp. and γ-protebacteria only exited in 1# reactor. The microbiological diversity of 1# reactor exceeded the other two ones. Flavobacterium, Bacillales, Actinomyces, Actinobacteridae and uncultured bacteria (AF527584, AF502204, AY592749, AB076862, AJ619051, AF495454 and AY133070) could be detected in the biological phosphorus removal reactors.

To investigate the relations between the characteristics of biological fouling layer and the fouling rate of membrane in membrane bioreactors used for wastewater treatment, a comprehensive study by atomic force microscopy (AFM), scanning electron microscopy (SEM) and high pressure liquid chromatography (HPLC) was carried out with comparative analysis of two fouled membranes which operated in mixed activated sludge liquor and its supernatant, respectively. The layer surface morphology was characterized with SEM and AFM. Further, to discuss the layer formation mechanism, the molecular weight distribution of soluble microbial products (SMPs) was investigated with HPLC. The results show that AFM is an appropriate technique to characterize the biological fouling layer morphology at nanometer level. AFM reveals the layer microstructure characteristics greatly relate to the fouling rate of membrane by three-dimensional images, profile analyses and roughness computations. In the mixed activated sludge liquor, the membrane with the better filterability has rougher fouling layer. The rougher fouling layer is contributed to the role of bigger microbial flocs, which can prevent the SMPs from directly attaching on the membrane surface and keep holes in the flocs overlaps.