**5. New Approaches Used in the Treatment of NORM and TE-NORM Produced from Sludge Waste Obtained from Oil and Gas Production**

In oil and gas production, the TE-NORM may be solid waste as scale and/or sludge and produced water. Our literature shows that TE-NORM contains activity concentrations of Ra226 ranging from undetectable levels to 1000 kBq/kg [52] and the activity level concentrations of Ra226 in TE-NORM can be much higher than the exemption levels established by IAEA [53]. As mentioned before, the recommended exemption level for uranium-series is: U238 = 1 Bq/g and Ra226 = 10 Bq/g. For thorium decay, a chain is: Th232 = 1 Bq/g, Ra228 = 10 Bq/g, and Ra224= 10 Bq/g.

It is important to focus on the environmental and health impacts from the uncontrolled release of TE-NORM wastes [54, 34, 23]. Treatment of these wastes is of increasing interest because accumulation of large amounts with a significant activity may cause health risks to the workers through exposure, inhalation of radon (Rn222) decayed from radium, and/or ingestion of waste dust during the periodical maintenance of the equipment used. Treatment of TE-NORM wastes from many industries still needs more efforts. The traditional methods used before include subsurface disposal, volume reduction, use of scale and/or sludge inhibitors, recycling, and leaching using chemical solutions [55–57]. In addition, a simple extraction process is carried out using saline solutions and chemical solutions [41, 58] to removal of Ra226, Pb210, Rn220, Th232, Ra228, and Ra224 from TE-NORM wastes produced from oil and gas industry.

Sequential chemical treatment for radium in sludge or scale to reduce its activity concentration in oil and natural gas production fields is recommended. The proposed treatment method was carried out on the basis of two approaches using chemical solutions through four successive steps.

Successive four steps were used to leachate the radium species in the waste of TE-NORM [59].

Before the treatment investigations, the activity concentrations of the main three radium isotopes were measured. It is found that the average activity level of Ra226, Ra228, and Ra224 were 11950 ± 1700, 1750 ± 200, and 1900 ± 250 Bq/kg, respectively. Due to the high accumulation of radium species in huge amounts and high activity concentrations causing health hazards to the environment and the workers, sequential chemicals treatment approaches are suggested as a new trend to reduce the human and environmental hazard potential.
