11 12In the present work, homogenous (photo-Fenton) and heterogeneous photo-assisted systems 13 (Fenton/TiO 2 /UV, Fenton/ZnO/UV and Fenton/TiO 2 /UV/Air) were investigated for the treatment of a 14 diesel-oil wastewater emulsion. The augmentation of the photo-Fenton process by heterogeneous TiO 2 15 increased the reaction rate, in terms of COD reduction efficiency from 61% to 71%. Furthermore, the 16 COD removal efficiency was increased to 84% when air was bubbled through the reactants. However, 17 if the Fenton/TiO 2 /UV/Air process is to be utilized as a treatment for this wastewater, the separation of 18 the TiO 2 from the treated effluent would need further consideration. 19 20

The objective of this study is to develop a mathematical model which would confidently predict the rate of substrate degradation of an oil-water emulsion in a laboratory-scale completely-mixed continuous flow reactor using the photo-Fenton treatment process. Two models are developed from first principles and the predicted substrate removal rates for both models are compared with experimental data. The principal conclusions of the study are that both models produce good correlations with the experimental data at moderate to long hydraulic retention times, but, at short hydraulic retention times, there is some divergence between the predicted and measured data. This disparity may be attributable to a greater degree of short-circuiting through the reactor at short hydraulic retention times.

This is an electronic version of an article published in Chemical Engineering Communications, Experiments have been conducted to test the effectiveness of Fenton's reagent (containing the 22 ferrous salts of chloride, sulphate or oxalate), Fenton-like reagent (containing ferric salts of chloride 23 and sulphate) and the coagulation method using FeCl 3 for an alum sludge conditioning at a constant 24 hydrogen peroxide and iron salt concentrations of 125 and 20 mg/g DS (dry solids), respectively. 25The effectiveness on dewaterability of the alum sludge demonstrated that the maximum reduction 26 (%) of SRF (specific resistance to filtration) and CST (capillary suction time) of 74 % and 47 %, 27 respectively, can be obtained when Fenton's reagent was adopted for sludge conditioning. Such 28 reduction of 64% for SRF and 38% for CST can be achieved when Fenton-like reagents were 29 applied. 30 2 31

The anaerobic biodegradability of domestic sewage for four Egyptian villages and four Egyptian cities was determined. The sewage of the Egyptian villages and cities represented a very strong sewage with an average total COD of 1100 and 570 mg/l, respectively. The biodegradability of the Egyptian-villages sewage (73%) was higher than that of the cities (66%). The results of a mathematical-model indicates that at applying a UASB reactor for the treatment of Egyptian villages and cities sewage, an optimum HRT of, respectively, 16 and 8 h is required. At these HRTs, a total COD removal and a conversion to methane of, respectively, 62-70% and 59-64% can be achieved for the sewage of Egyptian cities and, respectively, 71-77% and 67-69% will be obtained for the villages sewage. The model results show also that at a treatment of villages sewage in a two-step (anaerobic filter + UASB reactor) system a higher total COD removal can be achieved (77-81%) at a short HRT of 10 h (4+6 h).

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