Hidrologia: Pesquisa Atual

In this study, coagulation-flocculation process was optimized using PFS, PFPD₁, PFPD₂ and PFPD₃. The response surface methodology was used to investigate the effect changes in the level of coagulant dose and coagulation pH have on turbidity and COD removal. In addition, the optimum combination of coagulant dosage and coagulation pH that yields the maximum removal of turbidity, and COD were determined. The results revealed that the optimum conditions for the four coagulants were dosage of 388 mg/L and pH of 7.6 for PFS; dosage of 388 mg/L and pH of 7.45 for PFPD₁; dosage of 351 mg/L and pH of 8.0 for PFPD₂; dosage of 419 mg/L and pH of 7.64 for PFPD₃. The model showed that for turbidity removal, the effectiveness of the coagulants in decreasing order was PFS>PFPD₁>PFPD₂>PFPD₃ while for COD removal, the order was PFPD₂>PFPD₃>PFS>PFPD₁. The verification experiments demonstrated a good agreement between experimental data and model values. Therefore, the RSM approach was appropriate for optimizing the coagulation-flocculation process.

Carboxymethyl chitosan have been investigated for many biomedical applications as well as for the removal of metal ion and cationic dye from aqueous solution. But, carboxymethyl chitosan is soluble in water and therefore, it is difficult to reuse. The aim of the work was to prepare cross-linked O-carboxymethyl chitosan (OCMCTS) with different degree of substitution for the removal of Crystal Violet (CV) cationic dye from aqueous solution. The influence of the parameters such as initial pH of the dye solution, initial dye concentration, adsorption temperature, degree of substitution of OCMCTS and adsorption time on the adsorption capacity was studied using batch method. The results showed that the adsorption capacity of modified CTS increased from 28.49 mg/g to 239.54 mg/g. The kinetic study of OCMCTS showed that it follows the pseudo-second-order kinetic rather than pseudo-first-order kinetic. The adsorption equilibrium showed that the experimental data could be best fitted to the Langmuir equation. The desorbed OCMCTS can be reused to absorb the cationic dyes. Therefore, cross-linked OCMCTS may be favorable adsorbent and could be employed as low-cost alternatives for the removal of cationic dyes in wastewater treatment.

The purpose of this paper is to estimate the amount of landfill gas (LFG) generation from Jebel Chakir landfill which is the first largest landfill in Tunisia. To achieve that LandGEM model was used in predicting the amount of LFG generation. It was found that the LFG generation reaches its peak value of 2.61×107 m3/year by the year 2011, one year after the landfill closure. Furthermore, the power that can be obtained from the landfill in case of LFG recovery was estimated to be 35.5 GWh, providing a significant power generation opportunity at Jebel Chakir landfill. Utilizing the biogas will not only generate a green energy, but also will create a source of revenue through selling the certified emission reduction regulated by Clean Development Mechanism of Kyoto protocol.