The present study deals with the removal of phosphorus from wastewater by using oven-dried alum sludge (ODS) as adsorbent that was collected from Al-Qadisiya treatment plant (Iraq); it was heated in an oven at for 24？h and then cooled at room temperature. The sludge particles were then crushed to produce a particle size of 0.5–4.75？mm. Two modes of operation are used, batch mode and fixed bed mode, in batch experiment the effect of oven-dried alum sludge doses 10–50？g/L, pH of solution 5–8 with constant initial phosphorus concentration of 5？mg/L, and constant particle size of 0.5？mm were studied. The results showed that the percent removal of phosphorus increases with the increase of oven-dried alum sludge dose, but pH of solution has insignificant effect. Batch kinetics experiments showed that equilibrium time was about 6 days. Adsorption capacity was plotted against equilibrium concentration, and isotherm models (Freundlich, Langmuir, and Freundlich-Langmuir) were used to correlate these results. In the fixed bed isothermal adsorption column, the effect of initial phosphorus concentration ( ) 5 and 10？mg/L, particle size 2.36 and 4.75？mm, influent flow rate (Q) 6 and 10？L/hr, and bed depth (H) 0.15–0.415？m were studied. The results showed that the oven-dried alum sludge was effective in adsorbing phosphorus, and percent removal of phosphorus reaches 85% with increasing of contact time and adsorbent surface area (i.e., mass of adsorbent 50？g/L with different pH). 1. Introduction Wastewater or contaminated water is a big environmental problem all over the world, in industrial plants; contaminants may be a result of side reactions, rendering the water stream an effluent status. These impurities are at low-level concentration but still need to be further reduced to levels acceptable by various destinations in the plant. Surface waters contain certain level of phosphorus (P) in various compounds, which is an important constituent of living organisms. In natural conditions the phosphorus concentration in water is balanced; that is, accessible mass of this constituent is close to the requirements of the ecological system. When the input of phosphorus to water is higher than it can be assimilated by a population of living organisms, the problem of excess phosphorus content occurs. Regulatory control on phosphorus disposal is evident all over the world recently [1–3]. Strict regulatory requirements decreased the permissible level of phosphorus concentration in wastewater at the point of disposal (i.e., 1？mg/L). This has made it very important to find
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