Renewable adsorbents from the solid residue of sewage sludge hydrothermal liquefaction for wastewater treatment.

Solid residue from hydrothermal liquefaction (HTL) of nutrient rich feedstock presents a promising source to recover valuable nutrients, such as phosphorus, in the solid form. The present work shows for the first time the potential of utilizing the waste residue remaining after nutrients extraction from HTL of sewage sludge, as renewable adsorbents. A parametric study was undertaken to investigate the influence of chemical activation conditions (temperature, residence time, activation agent loading, washing after activation) on raw and partially demineralized HTL solids. Kinetic and equilibrium adsorption investigation was undertaken for the removal of methylene blue (MB) from aqueous solution. For comparison purposes, a commercial activated charcoal (AC) was used. Demineralization was found to have a significant influence in the adsorption capacity of the resultant adsorbents. Three adsorbents were found to follow the Langmuir adsorption model, while the acid washed demineralized adsorbent had higher adsorption capacity than AC and was found to follow the Freundlich adsorption model. The superior performance of the acid washed demineralized adsorbent was verified from the kinetic study where all adsorbents were found to best fit the pseudo-second order model. Adsorption capacities for MB at equilibrium were 367.1, 332.3, 297.4 and 87.6 mg/g, for acid washed demineralized adsorbent, AC, demineralized adsorbent, and raw adsorbent, respectively. Finally, the most promising adsorbents were assessed for their adsorption capacity to remove pharmaceuticals present in a real wastewater treatment effluent. Results indicated ultimate concentration for all targeted compounds below the detection limits for acid washed demineralized adsorbent, AC and demineralized adsorbent. Future implementation of HTL technology in wastewater treatment facilities, will not only provide an efficient way to valorize sewage sludge into bio-crude and nutrients, but can also enhance technology integration by providing the precursors for renewable adsorbents needed in tertiary treatment of wastewater.

Orphelins du SIDA dans la region de Dakar : enquete sur leurs conditions de vie en vue d'une strategie d'intervention pour leur prise en charge

Cette etude dans laquelle les auteurs tentent de cerner les conditions de vie des orphelins comporte cinq chapitres. Le 1er chapitre porte sur la problematique et met en relief les risques auxquels sont eposes les orphelins du Sida. Le 2eme regroupe le cadre conceptuel et la revue de litterature ; le 3eme et le 4eme portent sur la description des methodes utilisees et l'interpretation des donnees obtenues. Le dernier chapitre decrit le role du travailleur social et fait des recommandations pour la prise en charge des orphelins