|Abstract||Construction dewatering is an operation used to remove shallow groundwater infiltrated into a construction site; this technique is used in most of the construction projects. After collecting the water from the construction site, the water is either discharged to the sea, injected in deep groundwater aquifers, or treated and reused in some other applications. In this study, treatment of dewatered construction water by waste steel slag was performed. The impact of the mass of steel slag, the contact time, steel slag particle size and pH were studied on the quality of dewatered construction water. It was found that the maximum removal percentage of suspended solids was 97%, which occurred when 5 grams of steel slag were in contact with the dewatered construction water. The uptake amount (q) was 63.12 mg of suspended solid per gram of steel slag. It was observed that equilibrium was achieved after a contact time of about 40 minutes. The impact of steel slag particle size was studied, where two different sizes of steel slag particles were considered namely, 425 and 75 nm. An uptake value (q) of 72.24 mg/g and 64.36 mg/g were obtained for steel slag particle size 425 nm and 75 nm, respectively. The impact of pH was studied, where it was found that at pH value of 12, the removal percentage of suspended solids was higher than pH of 2, where the uptake amount of suspended solids was 80 mg/g. In addition, the performance of steel slag was compared to a commercial chemical coagulant, where steel slag had a higher uptake amount of 72.24 mg/g compared to 60.62 mg/g for the commercial coagulant.