Dynamics of aluminum leaching from water purification sludge.

In this investigation, the shrinking core model is used to study the rate of aluminum salt leaching from water purification sludge (WPS). This model, which describes the aluminum leaching rate, can be developed to maximize the Al(III) recovering efficiency. Laboratory results indicate that when the mixing speed exceeds 80rpm, the effect of film diffusion control on the leaching process is greatly reduced, such that any further increase in the mixing speed does not affect the Al(III) leaching rate.

Monitoring and control of UV and UV-TiO2 disinfections for municipal wastewater reclamation using artificial neural networks.

The use of ultraviolet (UV) irradiation as a physical wastewater disinfection has increased in recent years, especially for wastewater reuse. The UV-TiO(2) can generate OH radicals, which is highly effective to inactivate microorganisms in wastewater disinfection. However, both UV and UV-TiO(2) disinfections create multiple physical, chemical, and bio-chemical phenomena that affect their germicidal efficiency.

A novel method for on-line evaluation of floc size in coagulation process.

Chemical coagulation is a simple and widely used water treatment process. A jar test based on the residual turbidity in the treated water was used to evaluate the optimal conditions for floc formation. However, the final residual turbidity does not show up variation of turbidity and floc formation during the flocculation process.

Simultaneously monitoring the particle size distribution, morphology and suspended solids concentration in wastewater applying digital image analysis (DIA).

The efficiency of particle sedimentation in wastewater treatment is seriously affected by particle size distribution and morphology. A laser particle size analyzer is typically to analyze particle size distribution in wastewater. However, using this analyzer for on-line monitoring is difficult.

Measurements of wastewater true color by 4/6 wavelength methods and artificial neural network.

The ADMI (American Dye Manufactures' Institute) 3 and 31 wavelength (WL) methods are the most popular measurements of the wastewater true color. However, significantly different measured results were found between the ADMI 3 and 31 WL methods for the same sample. This finding indicates that the ADMI 3 and 31 WL values should not be directly substituted for each other, resulting in the incomparability of these two color values.

Evaluating the efficiency of coagulation in the removal of dissolved organic carbon from reservoir water using fluorescence and ultraviolet photometry.

The present study used ultraviolet absorption (UVa) and the florescence intensity (FI) to evaluate the coagulation efficiency for removing dissolved organic carbon (DOC) in the raw water from Min-Ter, Li-Yu-Ten and Yun-Ho-Shen reservoirs in Taiwan. The results indicated that the ratio of DOC removal rate and FI removal rate was maintained at about 1 at various coagulant dosages. However, the ratio of DOC removal rate and UVa removal rate decreased as the coagulant dosage increased.

Effect of phosphate on removal of humic substances by aluminum sulfate coagulant.

The presence of humic acid may change the way phosphate is absorbed or stabilized by soil and how it influences the growth of plants. The binding of phosphate with the humic substance requires bridging between phosphate ions and humic acid by metal ions, such as aluminum or iron ions. The bridging reaction can take place in peat and allophane soil under acidic conditions, altering the effectiveness of the phosphate in soil.

Influence of eutrophication on the coagulation efficiency in reservoir water.

Water from the three reservoirs, Min-ter, Li-yu-ten and Yun-ho-shen, was examined for concentration of chlorophyll a, ultraviolet absorption (UV(254)), fluorescence intensity (FI), concentration of dissolved organic carbon (DOC), and fractionation of dissolved molecules by molecular weight. The water samples were collected over the change from spring to summer (May to July but before the typhoon season) when the water temperature and extent of eutrophication increase. Analytical results indicate that the concentration of DOC is proportional to the concentration of chlorophyll a, but not to the values of UV(254) and FI.

A study of coagulation mechanisms of polyferric sulfate reacting with humic acid using a fluorescence-quenching method.

A fluorescence-quenching method is developed to assess the effect of pH on the coagulation mechanism of humic acids (HA) reacting with metal ions. A polyferric sulfate (PFS) synthesized in our laboratory is adopted as the coagulant to simplify the hydrolysis process and increase the experimental precision. The following results are discovered.

Comparison of hydrolysis/coagulation behavior of polymeric and monomeric iron coagulants in humic acid solution.

Fluorescence quenching is commonly used to study the extent of metal binding to humic acid or fulvic acid. By studying this phenomenon, the hydrolysis and precipitation behaviors of polymeric and monomeric iron coagulants in the coagulation of humic acid were evaluated. Combined measurements of fluorescence intensity and dissolved organic carbon were performed to distinguish the hydrolysis and organic matter binding of polymeric and monomeric iron salts in coagulating high molecular weight organic compounds.