Coal Fly Ash for Removal of Radionuclide from Water

Abstract

Coal Bottom Ash and Coal Fly Ash are a solid waste created from the combustion of coal. In the past few years, there has been a keen interest in finding the best ways to manage this waste. This has been a crucial subject, especially for environmental researchers. Coal ashes have unique characteristics, which is why they were used in fields such as waste-water treatment, building materials, and in agriculture. 

A current investigation features the performance of radiological assessment of Waste Water Treatment (WWT). This is done with the help of coal ashes, which are used as filters. The process is still under investigation and features up to four stages. Three of the four stages include Coal Bottom Ash Filtration, Coal Fly Ash Filtration, and Sand Filtration.

Two techniques were employed to help evaluate the Radiation risk as a result of Coal ashes. The two methods include gamma Ray spectrometer and dosimetry alpha that involves the use of LR115 detector.

Introduction 

The effects of chemicals on human health and the environment have triggered an ever-growing concern. Therefore, it is imperative to understand the close relationship between ecosystem and human health. The rate at which chemicals are introduced into the environment is increasing worldwide. There is a wide range of chemicals that are harmful and toxic to organisms. They can be distinguished into four main groups. These include inorganic substances such as human and veterinary pharmaceuticals, persistent organic pollutants, inorganic elements, and radioactive substances (Subramanian, Seemann, Merl-Pham, Hauck, Stewart, Atkinson, & Azimzadeh, 2017).

The United Nations Environment Programme, alongside the European Environment Agency, raised awareness about the problems related to severe exposure to potentially harmful substances. The ever-increasing concern about toxic compounds in the environment is also manifested by the escalating number of European Union directives and national and international conventions that are related to chemicals Lu, Niu, Chen, Jin, Yang, Xiu, & He, 2016).

Pathways to Radiation Dose

It is vital to approximate the radiation doses for exposure pathways from releases to the ground and surface water and atmospheric releases. Also, the doses from radiation will originate from y radiation that is emitted from storage silos. 

Uranium isotopes are the most crucial contributors to the dose that results from atmospheric releases. It is also accurate to conclude that inhalation is the most significant pathway. According to the surface water releases, the most crucial radionuclides are 226Ra, 228Ra, 234U, 99Tc, and 238U. There was no screening conducted for groundwater releases.

The primary role of the dose assessment is to ensure unbiased estimates of dose, alongside uncertainties that could help in epidemiologic studies that are under consideration. Up to this level, the focus can be concentrated on individuals that resided within an 8-km radius around the site between 1951 and 1988.

The report manifests an impressive effort to employ measurements in order to validate model estimates. For instance, RAC picked Metrologic parameters for many years, but there was no site data available. It is clear that the authors are loath to utilize climatic data from Dayton airport or Cincinnati. However, they made accurate decisions and came up with a rigorous analysis of why it is crucial to use Cincinnati data that are adjusted for the local patterns. Currently, the only best method that exists is the Monte Carlo sampling technique for employing the Cincinnati data (Exposure pathways 1993).

1. Atmospheric Releases

The main pathways of exposure are ingestion, inhalation, and external radiation originating from deposited radionuclides. The concentration of radionuclides will be approximated for outdoor conditions, but only for inhalation estimates. Nevertheless, because most individuals spend most of their time indoors, it is vital to come up with an indoor estimation as well.

Any discussion of methodology is not featured or discussed in the report. Neither does it contain any parameter values that are needed for the estimation of indoor air concentrations.

The body has presented numerous concerns regarding ingestion estimates. NCRP (National Council on Radiation Protection and Measurements) issued a report that claimed that potatoes, meat, bakery products, fresh fruits, and dairy products are the main foods that contribute to uranium intake.

2. Gamma Radiation from Storage Silos

Large amounts of natural radionuclides are available in K-65 silos and also metal oxide silo. These are the radionuclides that emit y radiation, which might be the source of possible exposure. All details on source term might have been considered. Therefore, there is no Gap in this part of the pathways analysis. The initial results of the validation of the model are interesting. 

The literature on Specific Activity of Fly Ash and Other Pertaining Material 

Thermal power plants are responsible for the production of most electricity. They do this by combusting coal and the operating facilities. It is because of this activity that many types of secondary products are produced. Any material that is formed as a result of the combustion of coal is known as Coal-Combustion Product (CCP). Out of all the CPPs that have been reported globally, Coal Fly Ash is the most common one. According to the reports received, Coal Flyash is a substance that comes in a powder form and is collected by gadgets that collect dust. These gadgets are usually installed in thermal power plants. Coal is usually used as the primary source of fuel in the installation process.

Some challenges are related to Flyash, such as the need for a vast area of land for disposal, and the fact that it is highly toxic, especially if it finds its way to the groundwater. There has been a conclusion that Flyash is one of the leading causes of air and water pollution in various parts of the world. It mainly has an impact on the construction industry. It, therefore, acts as the cardinal resource for environment and waste management. Until a decade ago, Flyash was regarded as waste material globally. However, in the current time, it is seen as the environment’s only saving grace.

In the current study, the Monte-Carlo technique alongside the United States Environmental Protection Agency’s Storm Water Management Model to create awareness on the problem of production of H2S in sewer networks. In the process, there is a suggestion of a tool that can be used for optimal SM placement in the sewer networks pipes. Also, it can be beneficial when it comes to maximizing the benefits of the application of technology. After the optimal locations for SM Unit placement have been identified, the response of the network after sewer mining is employed. The sewage that is pumped out from the system also gets examined. The study also tends to focus on optimal pumping scheduling with regard to minimizing the production of hydrogen sulfide.

Different Techniques of Water Treatment 

Water is believed to be naturally pure because it contains atoms of oxygen and nitrogen that are strongly bonded. However, organic materials find their way into the water, especially when they get into contact with other minerals. Exposure to chemicals and humanmade pollutants are other reasons why water might not be able to retain its purity long enough. When such things happen, water loses its drinkability as it contains harmful and toxic substances from various pollutants. Thankfully, there is a wide range of water treatment methods that can be used to make it safe for human and animal consumption. Though not all of them are excellently effective, they can be used to reduce the level at which unsafe water is distributed around the globe. 

A wide range of water treatment methods could be used depending on location and the level at which the water is polluted. The pollutants available can also be used to determine the best method to use.

1. Coagulation / Flocculation

Coagulation is a water treatment method that entails the addition of liquid aluminium sulfate or polymer or alum to untreated or raw water. This mixture leads to the coagulation or binding of dirt particles that are supposed to be removed. Once the particles have attached together, they form a layer known as flocs. Settling or filtration can be used to get rid of the larger dirt particles.

2. Sedimentation

If dirt particles and flocs are out through a treatment process, they end up in sedimentation basins. In this section, water is bound to move slowly, which makes the large dirty particles to settle at the bottom. Flocs that find their way to the bottom are referred to as sludge. This is further taken to dried lagoons. In Direct Filtration, there is no sedimentation step because the filtration is enough to remove the flocs.

3. Filtration

This process involves passing water through a filter. The filter is perfectly positioned to remove dirt particles from water. Therefore, filters feature sand, gravel, and at times crawd anthracite. The process enables the gathering of impurities that are found on the water surface. This then enhances the overall effectiveness of disinfection. Backwashing is used to clean the filters on a regular basis.

4. Disinfection

Before raw or untreated water is let into the distribution chamber, it gets disinfected so that disease-causing bacteria are all removed. Parasites and viruses are also ridden. Since chlorine is highly effective, it is also applied.

5. Sludge Drying

Solids that got gathered and removed through sedimentation are taken to drying lagoons.

The literature on 222Rn Internal Dose

222Rn is an inert radioactive gas and, therefore, can be transported easily into the atmosphere via emanation, exhalation, and migration. Research measurements have pointed out that the concentration of 222Rn varies during the summer and winter months. It also changes during wet and dry seasons (Ahmad, Nasir, Rizwan, Ullah, & Bakhsh, 2019).

The changes in the concentration of 222Rn can impact the electric field of the atmosphere along the boundary layer that is located near the ground.

Changes in radon concentration can affect the atmospheric electric field. At the boundary layer near the ground, short-lived daughters of 222Rn can be used as natural tracers in the atmosphere. 

In this work, factors controlling 222Rn pathways in the environment and its levels in soil gas and outdoor air are summarized. 222Rn has a short half-life of 3.82 days, but the dose rate due to radon and its radioactive progeny could be significant to the living beings. Epidemiological studies on humans pointed out that up to 14% of lung cancers are induced by exposure to low and moderate concentrations of radon. Animals that breed in ground holes have been exposed to the higher doses due to radiation present in soil air. During the years, different dose-effect models are developed for risk assessment on human and non-human biota. This work has reviewed research results of 222Rn exposure of human and non-human biota (Ahmad, Nasir, Rizwan, Ullah, & Bakhsh, 2019).

Gamma Spectroscopy 

Gamma Spectroscopy is a vital tool for studying the properties of nuclei and also to determine the decay schemes. It can also be used to explore nuclei that respect nuclear models. In an experiment, a germanium detector of very high purity with an initial resolution of around 0.15% is employed. Of the three detectors, the largest should have an approximate efficiency of 30% when compared to the standard 3×3” Nal detector.

In the current experiment, a rotational bond available in the nucleus 166Er is measured. After that, it becomes possible to calculate the momentum of inertia and gamma energies. The results are then compared to the model of a liquid or rigid rotator. Other studies can be devised for the study of complicated decay schemes of particular heavy nuclei. The same can be done to determine the level scheme by applying the Ritz’ combination technique. Also, a large passive shield can be used to find the measurements of weak radiation from the samples.that are derived from material or environmental analysis. This is usually done with the help of nuclear activation techniques.

Generally, gamma spectroscopy is used to study nuclear reactions and high spin states that result from the capture reactions. Gamma spectroscopy is also a vital tool that is used in material analysis, computer tomography, and geological exploration.

The literature on Monte Carlo Simulation 

This chapter features the research work related to monte Carlo simulation. Though it is a little brief, it covers every detail of the subject. It encompasses some of the most used techniques in a wide range of fields. Also, it is worth noting that some sections are related to surveys that were done around the Monte Carlo Method. This is done to provide the readers with detailed information that they deserve to learn from the method (Keramati, Ghorbani, Fakhri, Khaneghah, Conti, Ferrante, & Golaki, 2018).

The literature review of the method is vital in helping to plan the actual research. Monte Carlo is one of the most versatile numerical methods that have been widely used by researchers and scholars globally. Since it is independent of dimension, it is quite robust, but also a bit slow. In the research, there is a vivid description of how the Monte Carlo method can be applied. The technique is mainly used for integration problems such as sampling methods, convergence theory, and variance reduction techniques.

The points available in the quasi-random sequence are mostly correlated to achieve greater uniformity. The final quadrature method, also known as quasi-Monte Carlo, entails an impressive convergence rate. It is vital to comprehend the relevance and nature of Monte Carlo simulation deeply. It is equally vital to gain an understanding of the simulations and also how to analyze the final results and the mathematical methods that are employed to conduct the simulations (Keramati, Ghorbani, Fakhri, Khaneghah, Conti, Ferrante, & Golaki, 2018).

Monte Carlo simulation is a greatly important technique that can be used to analyze and predict uncertain scenarios. It is, therefore, used to come up with a probabilistic analysis of a wide range of events. Different software has manifested positive Monte Carlo Simulation in various domains such as engineering, finance, and mathematics (Ahmad, Nasir, Rizwan, Ullah, & Bakhsh, 2019).

Monte Carlo Simulation in Water Treatment 

There has always been a lot of pressure on water resources. It has also increased exponentially due to ever-growing urbanization. Climate impacts and population growth are some of the things that have contributed to lots of pressure on water resources. This means that there is a constant need for the development of innovations that could be used for waste-water treatment. The same goes for reuse technology. In the same context, a decentralized technology regarding waste-water reuse is one for sewer mining. It is primarily based on the extraction of waste-water from the waste-water systems, purifying it on site, and then producing recycled water that is applicable for non-portable uses.

Despite the considerable benefits of these technologies, there are several challenges that make it hard to implement successfully. Sewer mining interferes with biochemical processes inside the sewers and also affects the build-up of hydrogen sulfide. This ten results in corrosion, odour and several health-related challenges.

This study suggests a tool (Monte Carlo Method) that could be used to minimize the production and build-up of hydrogen sulfide. Environmental Protection Agency’s Storm Water Management Model (SWMM), alongside Monte-carlo method, are used to carry out simulations of the network. There is also an examination of the response of the network after sewage has been extracted from the same. The study aims at dealing with optimal pumping scheduling. The entire methodology is employed in a sewer network found in Greece for achieving beneficial results (Keramati, Ghorbani, Fakhri, Khaneghah,  Conti, Ferrante, & Golaki, 2018).

The method can be used for assisting in the selection of appropriate locations for the implementation of sewer mining. This can be done with the primary focus of getting rid of hydrogen sulfide, which is linked with numerous problems, while also ensuring that the high level of the need for pure water is satisfied.

Wrap Up

Coal Bottom Ash and Coal Fly Ash are a solid waste created from the combustion of coal. In the past few years, there has been a keen interest in finding the best ways to manage this waste. This has been a crucial subject, especially for environmental researchers. Coal ashes have unique characteristics, which is why they were used in fields such as waste-water treatment, building materials, and in agriculture. 

A current investigation features the performance of radiological assessment of Waste Water Treatment (WWT). This is done with the help of coal ashes, which are used as filters. The process is still under investigation and features up to four stages. Three of the four stages include Coal Bottom Ash Filtration, Coal Fly Ash Filtration, and Sand Filtration.

Two techniques were employed to evaluate the Radiation risk as a result of Coal ashes. The two techniques include gamma Ray spectrometer and dosimetry alpha that involves the use of LR115 detector.

 

References

Ahmad, N., Nasir, T., Rizwan, S., Ullah, H., & Bakhsh, M. (2019). Evaluation of 222Rn and 226Ra concentrations in cement and limestone of Sheikh Buddin Hill, Pezu, Pakistan using different techniques. International Journal of Environmental Analytical Chemistry, 99(7), 683-691.

Exposure pathways. (1993). [Denver, Colo.]: Colorado Dept. of Health [Disease Control and Environmental Epidemiology Division].

Keramati, H., Ghorbani, R., Fakhri, Y., Khaneghah, A. M., Conti, G. O., Ferrante, M., … & Golaki, M. (2018). Radon 222 in drinking water resources of Iran: a systematic review, meta-analysis and probabilistic risk assessment (Monte Carlo simulation). Food and chemical toxicology, 115, 460-469.

Lu, C., Niu, L., Chen, N., Jin, K., Yang, T., Xiu, P., … & He, M. R. (2016). Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys. Nature communications, 7(1), 1-8.

Subramanian, V., Seemann, I., Merl-Pham, J., Hauck, S. M., Stewart, F. A., Atkinson, M. J., … & Azimzadeh, O. (2017). Role of TGF beta and PPAR alpha signaling pathways in radiation response of locally exposed heart: integrated global transcriptomics and proteomics analysis. Journal of proteome research, 16(1), 307-318.

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