الفهرس | Only 14 pages are availabe for public view |
Abstract This study contributes to the exploration and development of the use of the Fenton and the photo-Fenton’s reagents for alum sludge conditioning and oily-wastewater treatment. In Ireland, a double fold increase of drinking water treatment sludge is predicted by the end of the next decade. Currently, organic polymers are adopted in alum sludge conditioning. However, there are increasing concerns regarding the use of these organic polymers because of the unknown and long-term effects of the potential release of excess polymer to the surrounding environment when the sludge is landfilled. Therefore, as an initiative action, alternative conditioning of aluminium-based drinking water treatment sludge using Fenton reagent (Fe2+/H202) was examined. Focuses were placed on effectiveness and factors to affect such a novel application of Fenton process. Experiments have demonstrated that considerable improvement of alum sludge dewaterability evaluated by capillary suction time (CST) can be obtained at the relativelly low concentrations of Fenton reagent. A Box-Behnken experimental design based on the response surface methodology (RSM) was applied to evaluate the optimum of the influencing variables, i.e., iron concentration, hydrogen peroxide concentration and pH. The optimal values for Fe2+, H202, and pH were found to be 21 mg g’ OS-’ (dry solids), 105 mg g’ OS-’ and 6, respectively, at which the eST reduction efficiency of 48±3 % can be achieved, this agreed with the values predicted by an established polynomial model in this study. Experiments have been conducted to test the effectiveness of Fenton’s reagent (Fe2+ and H202) containing the ferrous salts of chloride, sulphate or oxalate, Fenton-like reagent (Fe3+/H202) containing ferric salts of chloride and sulphate and the traditional coagulation method using FeCh for alum sludge conditioning at a constant hydrogen peroxide and iron salt concentrations of 125 and 20 mg g-OS-’, respectively. The effectiveness of these methods on the dewaterability of the alum sludge demonstrated that the maximum % of Specific Resistance of Filtration (SRF) and CST reached 74% and 47% and (64% and 38%), for Fenton and Fenton-like reagents, respectively. The ferrous chloride salt is the recommended salt which showed the maximum dewaterability. Moreover, the optimum pH was 6 (without any adjustment). However, this value may differ according to the iron salt used. Temperature had a positive effect on the sludge conditioning with Fenton’s reagent |