Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.

Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.     

Effect of powder painting procedures on the filiform corrosion of aluminium profiles

In this work, the filiform corrosion behaviour of powder painted aluminium profiles was studied, and the coating barrier properties together with adhesion to the substrate were analysed. Samples coated with a traditional painting procedure (one powder layer application followed by curing), and other samples coated using a special cycle to obtain wood grain effect were compared using accelerated filiform corrosion tests. Moreover, in order to better understand the degradation mechanisms of painted metal substrates, thermal stresses were applied to accelerate the natural weathering. The effects of the thermal aging were analysed by electrochemical impedance spectroscopy.     

The research seminar on computer algebra in 2005–2006

An annual report on meetings of the scientific research seminar on computer algebra is presented.     

Radiographisch-densitometrische Holzeigenschaftsuntersuchungen an Douglasien aus unterschiedlich durchforsteten Versuchsflächen

From two experimental areas with different thinning grades of a mixed stand of Douglas-fir and spruce, increment cores were taken from 40 Douglas-fir trees, chosen at random in a height of 1.3 m. The properties ring width, latewood percentage, average density, maximum and minimum density were examined from one part of the material by the x-ray densitometric method. The oven-dry density of the remaining part of increment core was examined for additional control. Based on the existing sample data, a significantly higher ovendry density was determined in the untreated area of higher stand density (376 stems/acre) than for the thinned stand (214 stems/acre). The specific gravity (at 10% moisture content) determined by x-ray densitograms shows no statistically valid difference on the average. The possible factors for this result are still being discussed. Further investigations of interactions between individual properties of the Douglas-fir samples obtained by the x-ray densitometric method are being carried out by multiple linear regression analysis.     

Hydrogen peroxide: Control of its content in water objects

A brief review of existing methods designed to determine hydrogen peroxide in aqueous media has been presented. Particular attention has been given to biosensor devices enabling us to exercise simple and express control of concentration of the specified compound.