Study of microfiltration behaviour of oily wastewater.

Crossflow microfiltration experiments were carried out with oily wastewater using alpha-Al(2)O(3) membranes with 0.05 microm pore size. The influence of parameters such as transmembrane pressure (TMP), crossflow velocity (CFV), oil concentration, pH and salt concentration on the microfiltration behaviors were studied based on the measurements of permeate flux, total organic carbon (TOC) removal efficiency, and size and zeta potential of the emulsion droplets. The results showed that there were different degrees of effect on the membrane separation performance by these parameters. The TOC removal efficiencies higher than 92.4% were achieved under all experimental conditions. A non-steady model of accumulation volume of permeation was developed. It was found that the calculated values were in good agreement with the experimental results. Sensitivity analysis was also conducted to identify the degree of influence of the parameters on the accumulation volume of permeation. The results indicated that the accumulation volume of permeation was significantly affected by the TMP.

Biosorption and desorption of copper (II) ions by Bacillus sp.

Batch biosorption experiments were conducted to investigate the removal of Cu2+ ions from aqueous solutions by a series of bacterial strains isolated from a local activated sludge process. The characteristics of 12 isolates were identified and examined for their ability to bind Cu2+ ions from aqueous solution. Among the isolates, two species exhibited biosorption capacity >40 mg of Cu/g of dry cell. Isotherms for the biosorption of copper on bacterial cells were developed and compared, and the equilibrium data fitted well to the Langmuir and Freundlich isotherm models. The biosorption of copper increased significantly with increasing pH from 2.0 to 6.0 regardless of the species. More than 90% of copper sorbed on the cells of Bacillus sp. could be recovered by washing with 0.1 M HNO3 for 5 min. The performance of two different desorption processes was also tested and compared. The results show that five biosorption and desorption cycles are a better operation process than five successive biosorptions followed by one desorption to remove and recover copper from aqueous solution. The biosorbent could be used for at least five biosorptions and desorption cycles without loss of copper removal capacity. It can be concluded that the activated sludge or sludge-isolated bacteria could be a potential biosorbent for copper removal.