Naturally occurring radon assessment in Al-Rustumia wastewater treatment plant
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Wastewater samples were collected from Al-Rustumia wastewater treatment plant. The methodology which was used to measure radon activity levels was long-term air measurements with passive solid-state alpha track detector CR-39. The collected samples include wastewater before and after treatment for 5 months which started from September 2017 to January 2018. The results show that the average values of radon activity level for untreated and treated wastewater samples were 0.049 Bq L−1 and 0.036 Bq L−1, respectively. Dissolved radon concentrations for the study samples were also calculated and their values were 1.270 Bq L−1 and 0.937 Bq L−1, respectively. The calculated radon surface exhalation rate for wastewater samples before treatment was 0.048 Bq m−2 h−1 and after treatment was 0.035 Bq m−2 h−1. These values are lower than the maximum acceptable radon levels as given by United States Environmental Protection Agency. As well as, the results reveal that radon activity level decreases after treatment process implementation, and there are no considerable variations with different times of the year.
KeywordsRadon Al-Rustumia WWTP Dissolved radon CR-39
Wastewater reuse is an essential part of water needs which enhances the preservation of purity of freshwater as well as decreasing the environmental pollution and the total supply costs. Developments in technology encourage the developing countries to take efforts toward the wastewater reuse (Al-Jayyousi 2003; Al-Hamaiedeh and Bino 2010).
Rapid growth of population, urbanization, development of sanitation service, and scarcity of freshwater increase the demand for the reuse of treated wastewater (Shaker et al. 2014; Alobaidy et al. 2010; Yadav et al. 2002; Qadir et al. 2009).
Wastewater originates from many sources, e.g., domestic, which is concerned as the largest source, commercial, and industrial sources (Eriksson et al. 2002; Flowers 2004). Irrigation with treated wastewater should be managed carefully in order to reduce the negative environmental impacts and can be more useful to the environment (WHO 2005).
The use of treated wastewater for irrigation, which is currently widely used, is suggested as an alternative way for irrigation due to scarcity of freshwater (DHWA 2002). Hence, TWW should be examined carefully in order to make certain that it meets Iraqi National Standards set by the Regulation 25 of 1967.
In previous studies on wastewater of Al-Rustumia plant, different indices such as Comprehensive Pollution Index (CPI) and organic pollution index (OPI) and hazardous parameters such as electrical conductivity (EC), total dissolved solids (TDS), sodium (Na+), sodium adsorption ratio (SAR), soluble sodium percent (SSP), residual sodium carbonate (RSC), chloride (Cl−),biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), and pH have been measured, in order to distinguish the contamination of the wastewater and furthermore to assess its appropriateness for irrigation purposes (Shakir et al. 2017; Ismail 2013). However, there is lack of researches on naturally occurring radioactivity and radon on wastewater of Al-Rustumia plant.
Transportation of radioactive materials (such as uranium, radium, thorium, radon, and other nuclides), from the geological formations and soils that contain them to the water that moves through it. These radioactive materials may dissolve in the water itself or linked to suspended particles in the water.
Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) may enter the sewage framework from ground and surface water, plants and sustenance and in addition from manufacture releases (e.g., water treatment plants, mining and oil enterprises, manures, gadgets, earthenware production, foundries, and paper factories).
Man-made radioactive materials may also be found in the environment due to accidents and weapon testing, for example, radionuclides produced from nuclear reactors processes, accelerators, industrial activities, researches, and nuclear medicine.
Radon occurs naturally in the environment; it is one of 238U decay series products and provides a continuous source of radiation. Radon has low solubility in water (ICRP 2014) which is temperature dependent, and it decreases at higher temperatures (Battino 1979). Radon is trapped by plant organs by diffusion, adsorption, and permeation (Tavera et al. 2002; Vives et al. 2011).
The objective of this research is to measure radon activity concentrations in the untreated and treated wastewater samples collected from Al-Rustumia (WWTP) by using solid-state nuclear track detector CR-39 and to assess its appropriateness for irrigation purposes.
Materials and methods
Baghdad, the capital city of Iraq, is situated on the Tigris River, and it is 25 km apart from the nearest point to Euphrates River to the west. Tigris River meets Diyala River at the southeast of Baghdad and borders its eastern suburbs. The population of Baghdad, as of 2016, is approximately 8,765,000, making it the largest city in Iraq. In the period between 1960 and 1980, the sewerage network was founded to work on the principle of separate systems. In 1980, a combined system was established and has been adopted since then. The capacity of the zero stage, which was created in 1960, was 40,000 m3 day−1 which served about 24% of Baghdad’s inhabitants only by full sewage processing. The first extension (stage 1) was added and partly combined with the zero stage in 1974 with capacity equal to 45,000 m3 day−1. Finally, the second extension (stage 2) was combined with capacity equal to 90,000 m3 day−1 in 1981. Thus, the total capacity of the system became 175,000 m3 day−1 and serves the east bank of Tigris River.
Wastewater samples were collected from Al-Rustumia (WWTP) and analyzed to measure the radon levels before and after treatment. The samples were collected for 5 months which started from September 2017 to January 2018 in order to study the variation of radon concentrations with the variation of weather temperatures.
Results and discussion
CRn, Cdis, and RERS for wastewater samples before and after treatment
Bq m−2 h−1
Bq m−2 h−1
It is clear from the obtained results that the treated wastewater samples do not perform any important source of radiation risk and can be considered safe to reuse in irrigation in so far as radon concentration is concerned. However, values of radon activity in untreated and treated wastewater samples are less than the EPA contaminant level (11.1 Bq L−1) (Tawfiq et al. 2015).
The average values of CRn for untreated and treated wastewater samples were 0.049 Bq L−1 and 0.036 Bq L−1, respectively, which are below the world permissible value of 11.1 Bq L−1 given by USEPA (2012).
The average values of Cdis for untreated and treated wastewater samples were 1.270 Bq L−1 and 0.937 Bq L−1, respectively.
Overall average surface exhalation rate of radon RERS for untreated and treated wastewater samples were 0.048 Bq m−2 h−1 and 0.035 Bq m−2 h−1, respectively.
Radon activity level decreases after the treatment process.
No remarkable variations found in radon activity level of the wastewater samples during the period of study.
Therefore, as from radiological point of view, the treated wastewater taken from Al-Rustumia WWTP is safe to be reused in irrigation and does not pose any considerable radiation hazards.
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