Purification of drinking water through rapid sand filtration often involves the addition of alum to achieve more effective removal of suspended solids and color from the raw water. A by-product of this operation is the material referred to as alum sludge. Direct discharge of water treatment sludge to a watercourse was a standard practice for years. Receiving wasters will be severely affected by episodic increases in aluminum [Al] which can have significant biological and physical as well as chemical consequences in dilute acidic surface wasters. The main health concern with Al is its neurotoxicity, which is the capacity of chemical, biological, or physical agents to cause adverse effects on the nervous system. It has been postulated that Al might be an etiologic factor for Alzheimer's disease. The organic matter and fine clay particles in alum sludge are valuable resource that can be reclaimed and reused for a beneficial purpose. Disposal is a costly and wasteful way of dealing with alum sludge. This study aimed at evaluating the use of alum sludge as a coagulant aid for improvement of the treatment efficiency of wastewater treatment plants. Alum sludge samples were collected from Bab Sharqy Water Treatment Plants, Alexandria. Wastewater samples were collected from East Sewage Treatment Plant of Alexandria. The alum sludge waste was characterized by neutral to slightly alkaline pH, difficult to be handled due to very high moisture content, having low content of total solids; volatile solids; and SVI, and high content of settleable solids; COD; and aluminum concentrations. Wastewater was characterized by neutral to slightly alkaline pH, high turbidity; total suspended solids; BOD; COD; and O-phosphates, and low settleable solids. The use of alum sludge as a coagulant aid for improvement of the treatment efficiency of wastewater treatment plants exhibited good coagulant proprieties for the removal of BOD, COD, and phosphates with increase of TSS. As land application of alum sludge improves the soil structure and fertility, it is recommended to use treatment wastewater by alum sludge in Alexandria green belt area.