**4.4. Liquid TE-NORM waste**

TE-NORM in slurry form (e.g., waste water or solids mixed with water) can be re-injected into deep formations for disposal [18]. There are three classes for injection:

Class (I): This option is used for any liquid TE-NORM wastes. Over 90% of all produced water resulting from oil and gas operations is injected through wells into permeable disposal formations, which lie below underground sources of drinking water (USDW), and surrounded by impermeable layers. After injection, the well is closed, sealed with cement, and capped, effectively isolating injected materials from the surface. Injection costs vary based on volume, depth, formation pressure and permeability, and other factors. The cost of injecting a slurry could be comparable, or slightly higher.

Class (II): Well injection, when TE-NORM concentrations prevent disposal in class (I). The used wells in this class are deeper and are constructed to give great protection against potential migration of injected fluids to (USDW). Disposal in class (II) well is to some degree more expensive than class (I) injection. Also, transportation costs would be higher, as limited number of class (II) disposal wells exist.

contaminated with mercury and TE-NORM. After melting, the radiological measurements showed that the produced metal did not contain any detectable residual of TE-NORM, and can be re-used again in steel works. About 98% of TE-NORM were bound to the slag and ~2% were detected in the filter dust, mainly consisting of the nuclides 210Pb and 210Po. The secondary waste produced is ∼43% of the total weight of the material supplied, whereas TE-NORM waste

Chemical separation of the radionuclides incorporated in the contaminated equipment (pipelines, tubes, pumps) is carried out by melting at 1400°C, to further fractionation of radionuclides in melt, slag, or dust. The analysis of data showed that most of 238U and 232Th series are transferred from melt (dense main component, contains only 1% of the remainder radioactivity) into the slag (light minor component, contains only 98% of the total radioactiv‐ ity). All activity of 210Pb was concentrated in the filter dust, because it is evaporated at normal melting temperature above 1300°C [47]. Equipment should be decontaminated to less than 0.4

For TE-NORM-contaminated scale, sludge, and soils with very low levels of radioactivity, a suitable disposal option is to spread over the ground and mix with non contaminated soils, to dilute the contaminated soils and reduce the radioactivity level to background levels. This type of disposal is often the most cost-effective [48]. Subsurface disposal options include under‐ ground injection and down hole encapsulation. This type of disposal is widely acknowledged as one of the most environmentally sound methods of disposing TE-NORM-contaminated

**i.** Underground injection, established by mixing a TE-NORM-contaminated waste with

**ii.** Down hole encapsulation, entails placing TE-NORM-contaminated scale, sludge,

TE-NORM in slurry form (e.g., waste water or solids mixed with water) can be re-injected into

Class (I): This option is used for any liquid TE-NORM wastes. Over 90% of all produced water resulting from oil and gas operations is injected through wells into permeable disposal formations, which lie below underground sources of drinking water (USDW), and surrounded by impermeable layers. After injection, the well is closed, sealed with cement, and capped, effectively isolating injected materials from the surface. Injection costs vary based on volume, depth, formation pressure and permeability, and other factors. The cost of injecting a slurry

deep formations for disposal [18]. There are three classes for injection:

cement in a slurry, then injecting the formed mixture into a deep subsurface forma‐

tubes, and other small pieces of the production equipment (e.g., valves, filters, pumps, screens) inside the casing of a well, which is to be plugged with cement and then

for beta and gamma emitter, before any release.

consists of ~95% of slag and ~5% coarse dust [45].

for alpha emitters or 4 Bq/cm2

sludge. The two common forms of subsurface disposal are:

**4.3. Solid TE-NORM waste**

tion.

abandoned.

**4.4. Liquid TE-NORM waste**

could be comparable, or slightly higher.

Bq/cm2

96 Advances in Petrochemicals

Class (III): Deep well injection, these wells consist of injecting liquid wastes contaminated by TE-NORM fluids into the well at sufficiently high pressure to create a fracture in permeable shale formations. After the scale/water mixture is displaced into the fracture, then the pressure is reduced, and the fracture closes.

The scale is trapped between the fracture wells and is incapable of re-entering the well bore. Deep well injection is generally regarded as an effective method for the disposal of TE-NORM waste because it does not depend on the mechanical integrity of the well to prevent potential subsurface contamination.

When the radium ions are present in the produced water, any drops in pressure and temper‐ ature can lead to the solubility products of their sulfates and carbonates being exceeded. This is the main cause for precipitation of radium as sulfate and carbonate scales on the inner walls of production tubules, well heads, valves, pumps, separators, water treatment vessels, gas treatment and oil storage tanks. Particles of clay or sand co-produced from the reservoir may also act as catalytic surfaces for initiating scale deposition or may adsorb the cations. Daifullah and Awwad [49] found that oil shale is a good adsorbent for Hg(II) from aqueous solution. Shales normally contain at least 35% clay minerals, and a significant fraction contains potas‐ sium as an essential constituent. Removal of mercury (II) from wastewater was studied using camel bone charcoal [50]. Shales can adsorb the series radionuclides [51]. Common anthropo‐ genic sources of mercury include nuclear fuel production as part of the uranium purification and isotope separation process (235U and 238U). Mercury in the form of Hg(II) also enters aquatic environments from industrial and nuclear fuel wastes. The feasibility of using oil shale for removal of Hg(II) has been addressed. Also, it was found when using seawater to enhance oil recovery, it will increase the sulfate concentration of the produced water and enhance scale deposition. So, new trends should be used to solve these problems.
