Nonlinear modelisation of heavy metal removal from aqueous solution using Ulva lactuca algae.

After extensive analysis, Ulva lactuca dried algae, collected from the Monastir coastal zone, was proven to be successful as an adsorbent for the removal of certain inorganic pollutants. The main objective of this study was the nonlinear modeling of heavy metal removal from an aqueous solution, using a freely available and well analyzed biomaterial, as well as the evaluation of its efficacy on various metal ion sorptions. Although relatively low specific surface area, compared to more conventional adsorbents, the selected biomaterial displays very interesting retention capacities when used with aqueous inorganic pollutants. The pseudo, first and second-order kinetic models were used to investigate the kinetic retention mechanism. Assuming the nonlinear form, the results indicate that the retention mechanism is diffusion controlled. Concerning the heavy metal uptake capacity, it was found that the selected biomaterial has a retention capacity of 67 mg g(-1) of Ni(II), 112 mg g(-1) of Cu(II), 127 mg g(-1) of Cd(II) and 230 mg g(-1) of Pb(II).

Vat dye sorption onto crude dehydrated sewage sludge.

In this work, sewage sludge is used as a textile dye adsorbent. A sample of crude dehydrated sewage sludge issued from an urban wastewater treatment plant (high-rate aeration, activated sludge process, Sahline, Tunisia) is utilized for vat dye retention. The main objective of this work is to evaluate the "efficiency" of the crude material on vat dye sorption. However, no treatment to modify any of the adsorbent properties was considered. Although the relatively low specific surface area (about 3.2m(2)g(-1)) compared to more conventional adsorbents, the used material shows very interesting retention capacities when used with water pollutants. The pseudo, first and second order kinetic models have been used to investigate the retention mechanism. When linearized, the pseudo-second order fit, for the both used dyes, in a better way the obtained experimental results than the pseudo-first order kinetic model. For equilibrium dye uptake amount it is found that the used material has a capacity (Langmuir Freundlich monolayer) of 73.1mg/g to fix the VAT RED 10 and 58.7 mg/g to fix the VAT ORANGE 11.

The anaerobic treatment of sewage and granule formation in upflow anaerobic sludge blanket reactor.

The granulation process was examined using synthetic wastewater containing glucose in a 1 liter laboratory upflow anaerobic sludge blanket (UASB) reactor. The anaerobic biotransformation of glucose was investigated during the granulation process. Anaerobic unacclimated sludge and glucose were used as seed and primary substrate, respectively. Massive initial granules were developed after three months of start-up. The effect of operational parameters such as influent glucose concentrations, pH, Volatile Fatty Acids (VFA) were also considered during granulation. The presence of a large concentration of sulphate in the sludge of a mesophilic (37 degrees C+/-1 degrees C) UASB reactor treating sewage resulted in severe process disturbance, with a complete inhibition of the propionate-degrading ability of the sludge. Severe inhibition of acetate removal was also observed, with concentrations of propionic acid and acetic acid in the reactor effluent of 1.72% and 18.88%, respectively. Hydrogen sulfide (H2S) is formed from the anaerobic decomposition of organic matter containing sulfate by sulfate-reducing bacteria. This gas is toxic at rate exceeding 2% tolerable by a reactor. The result shows the rate of hydrogen sulfide production was 3.8 %.