Thesis (Ph.D.) – Cairo University. Faculty of Engineering.

Includes Bibliographical References.

Coagulation is critical process in drinking water treatment involving colloid charge neutralization followed by aggregation into floes that are amenable to solid/liquid separation with subsequent processes such as filtration. Most of water treatment plants use alum AI/SO 4)314-H2 0, as a coagulant due to its effectiveness in treating awide range of water type and relatively low cost. Alum sludge produced from water treatment plants contains aluminum hydroxide mixed with suspended solids in raw water. The aim of this research is to study aluminiumsulphate (alum) recovery from alum sludge in aqueous solution by acidification process using sulphuric acid, and compare the results of applying the acidification method to the alum sludge produced from different clarifier types. Bench scale tests were performed for alum sludge samples from three different water clarifier typesto evaluate the process. The results of the experimental works showed that the recovered alum volume produced from pulsator system after acidification process is the best value with percent recovery 98%, then the high rate system with percent recovery 96.4%, and the classical system with percent recovery 94%. All these percentage achieved at the liquid sludge. The concentration of recovered alum occurred by acidifying the sludge produced from classical clarifier, the high rate type and the pulsator type are 20.2%, 18.5% and 13.90% respectively. The recovered alum can reduce turbidity with percentage 84.2% in the classical clarifier type, 79.52% in the high rate clarifier type and 76.47 in the pulsator clarifier type. A mixture of recovered alum and fresh alum can also be used to improve the coagulation process.

Text in English, Summaries in English and Arabic.