**2.2. NORM in sludge**

Radioactive molecules containing radium which were not incorporated into scale can be found in sludge, produced sands, and produced waters. Before the treatment investigations, the activity concentrations of the main three radium isotopes were measured in sludge [41]. It is found that the average activity level of Ra226, Ra228, and Ra224 for samples taken from Abu Rudeis region, Government of Sinai–Egypt, were 11950, 1750, and 1900 Bq/kg, respectively. Due to the accumulated TE-NORM wastes in huge amounts and release of high activity concentrations to the environment and the workers, treatment approaches are suggested to reduce the human and environmental hazard potential. Sludge is composed of dissolved solids which precipitate from produced water as its temperature and pressure change. Sludge generally consists of oily, loose material often containing silica compounds, but may also contain large amounts of barium.
