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In this study, zeolite was prepared from cheap local Egyptian clay (kaolin) and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, SEM. The prepared zeolite was used as a binder for immobilization of the metals Cd 2þ , Cu 2þ , Ni 2þ , Pb 2þ , and Zn 2þ in contaminated sewage sludge. Different leaching tests were conducted to determine the efficiency of the prepared zeolite for metal stabilization. The leaching of the metals from stabilized sludge decreased as the zeolite amount increased. It was found that 10% of zeolite is sufficient for the stabilization of all metal ions under investigation. It was suggested that the metal uptake mechanism by zeolite was by an ion-exchange mechanism. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 0.83 MPa, which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.

Wastewater from an oil and soap company provided the material of this study. The company discharges 31,000 m3/d of untreated wastewater into the Nile River. The wastewater was highly contaminated with organic and inorganic pollutants. An end-of-pipe treatment scheme was devised of dissolved air flotation with/without alum followed by biological degradation. The biological unit was compact and comprised an aeration tank based on a completely mixed activated sludge process followed by a high rate settler. The unit was operated at two organic loads, namely 1.44 and 2.88 kg BOD5/m3/d. The results obtained showed that this scheme of treatment produced a high quality effluent suitable for disposal into surface water or reuse. Also, the high rate settler acted as a biological reactor as well as a settler for finely divided organic matter.

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