Hazardous Wastes and Contaminated Sites in Environment.

Introduction

Innovation is destruction……..It is creation of something new and refreshing yet it also gives birth to malice – the destruction of the very essence of innovation. This evilness is in the form of hazardous wastes spreading in every corner of Earth and causing harm to environment and eventually health of human beings.

The hazardous wastes could be in any form like liquids, solids, contained gases, or sludges, or could be the parts of the manufacturing processes or commercial products not of use, like cleaning fluids or pesticides. According to The University of Texas Harris County Psychiatric Center (UTHCPC), the hazardous wastes could be categorized into following three types: Chemical, Radioactive, Medical/Infectious. (UTHCPC, 2008: Online) A chemical waste is a waste when owing to the disposal of large quantity in number; its physical or chemical characteristics may lead to rise in mortality level or severe illness among human beings or severe threat and risk to environment. Ignitability, Corrosivity, Reactivity and Toxicity are considered as the basic characteristics of chemical wastes.

Medical/Infectious wastes require special handling to give protection to human health and environment and if not properly treated may transmit infectious diseases. Microbiological wastes constitute any discarded medical or pharmaceutical waste materials, many kinds of animal wastes including carcasses of animals, human and pathological wastes and sharps. Radioactive waste which is generated by laboratories “is low-level radioactive waste from the use of by-product materials and naturally occurring or accelerator-produced radioactive material (NARM)” (The University of Texas, 2006: Online) where reactor-produced radioactive material, known as radiolabelled chemicals, is a by-product material and uranium and thorium salts are naturally occurring or accelerator-produced radioactive material. (The University of Texas, 2006: Online)

Waste disposable methods vary differently in different ways; these are: Landfill, Incineration, Resource recovery, Recycling and Composting and Anaerobic digestion. Landfill is considered a traditional method of disposal of waste materials and is used in many countries. During ancient period, this practice was often undertaken in disused quarries, mining voids or borrow pits. A landfill if accurately designed and managed properly can be inexpensive method for disposing of waste materials that reduces the effect on the local environment. Landfills can be of two types: secure or sanitary. A secure landfill consists of a liner, which is generally low permeability clay. Modern landfill is designed in way that it includes methods like leachate known as clay or plastic lining material. Hereby, the disposed waste materials are turned into compact form to increase the density, to stabilize the new landforms and are covered to prevent mice or rats from entering and to decrease the quantity of wind blown litter. (Action Environmental services 2008: Online) Many of the landfills also have landfill gas extraction system, which is installed after closure to pump out the gas generated by the decomposing waste materials and this is done by the use of perforated pipes or flare off system or burnt in a gas engine to generate electricity. Flaring off the gas is better method than other methods as it is good for environment, as it consumes the methane, which is generally harmful for environment. Methane is far more intoxicating green house gas than carbon dioxide. (Action Environmental services 2008: Online)

There is also a deep concern that hazardous materials disposed of to the landfill create hazardous impact on environment. They may still be in a state of instability, in other words, they still could be flammable or reactive or they may dissolve in the liquid that percolates through the leachate. If this leachate gets an escape route from the site, it may make ground water too contaminated. To reduce this impact, it is wise to make the waste immobilize and that could be done through the methods of fixation, encapsulation, certain biological treatment methods like Land treatment, Langooning and bioremediation methods etc. (Tedder & Pohland, 1998: 29).

Incineration is disposal of waste materials involving combustion of waste at high temperatures. Under this method, the waste materials are disposed at higher temperatures. Waste materials easily get transferred into heat or residual solid ash and or emitted in a gas form. Waste materials are burnt in the furnace/boilers where the steam or electricity is produced. It also involves modern air pollution control systems and emission monitors. (Denison, R.A. & Ruston, 1990). This system is also known as energy from waste facility (EfW). This process is commonly used in Japan where the land is scarce, as it does not involve enough of land area as required by landfill. Sweden and Denmark also use this system of disposal. (Action Environmental services 2008: Online).

But by simply burning the materials at higher temperatures cannot break down complex chemical chains like dioxin. The requirement is the use of the gas or oil burners and air blowers to increase the temperature high enough to break the molecules, or the exhaust gases can also be passed through the heated tubes to increase the magnitude of thermal breakdown. (Action Environmental services 2008: Online).

Resource recovery is a recent phenomenon in waste management and can be considered as an important resource, which can be exploited for commercial use. There are various ways by the way resources can be extracted and recycled from waste materials. Certain contents of the wastes can also be converted into electricity. These different methods may be known as resource recovery or recycling. (Action Environmental services 2008: Online) In many of the developing nations, it involves rag pickers or manual labourers who would gather salvage materials through rags and sell them off in the recycling market. This system is very cost effective yet involves exploitation of labourers who easily get prone to diseases, injury and reduced life span.

Recycling means reuse of waste materials for some other use. This system involves collection and again using the waste materials of everyday use like newspapers and drink bottles. They are collected and are distinguished in different categories to form new products. In many countries, recycling is done through collection of waste materials from dedicated bins and collection vehicles. In many countries, the most common recycled materials are aluminium beverage cans, steel, food and aerosol cans, HDPE and PET bottles, glass bottles and jars, paperboard cartons, newspapers, magazines, and cardboard etc. Other types of plastic (PVC, LDPE, PP, and PS) are also recyclable, although these are not as commonly collected. These items are usually composed of a single type of material, making them relatively easy to recycle into new products. The recycling of complex products (such as computers and electronic equipment) is more difficult and costly, due to the separation and reprocessing required. The cost of this method is comparatively more and environment benefits are also less. The benefit to environment is more profound in this method as it requires less quantity of energy, water and other resources to recycle materials as compared to the production of new materials. For example, to recycle 1000 kg of aluminum cans can save approximately 5000 kg of bauxite ore being mined and can prevent in the generation of 15.17 tons CO2eq greenhouse gases (source: ALCOA Australia). Besides recycling of steel can save 95% of the energy used to refine virgin ore (source: U.S. Bureau of Mines).

Plant materials, food scrapes and other paper products are constantly being recycled by the use of the process known as biological composting or digestion methods for the purpose to decompose the organic matter and kill pathogens and the organic material formed can be used for agricultural or landscaping purposes by recycling as mulch or compost. (Action Environmental services 2008: Online).

There are several disadvantages in this method as separate factories are required for recycling of materials causing more pollution and also more energy consumption for transport, sorting, cleaning and storage. In recycling process when different products are broken down, it produces pollutants like chemical stews.

Radio Active Hazardous Wastes and its management

Radioactive hazardous waste materials as defined by the International Atomic Energy Agency (IAEA) are “materials that contains or is contaminated with radionuclides at concentrations or radioactivity levels greater than clearance levels established by the appropriate authority and for which no use is foreseen.” (Australian Radiation Protection and Nuclear Safety Agency, 2006: Online) Though Australia did not classify radioactive waste materials yet for convenience radioactive waste is divided into five different categories: Very Low Level, A, B, C and S. Very low level radioactive wastes can be disposed by users under the scheme the Code of practice for the disposal of radioactive wastes by the user. These wastes consist of radioactive contents more than the exempt waste but they are less than the upper limit fixed for in the process mentioned in user disposal code. Category ‘A’ consists of radioactive wastes of short life, which includes light contaminated items like cardboard, paper, plastics, protective clothing, rags, glassware, laboratory trash or equipment, certain consumer products and industrial tools or equipment. It may also contain contaminated bulk waste materials from light contaminated soils or from mineral processing. Category ‘B’ consists of solid waste materials having more quantities of beta- or gamma-emitting radionuclides than Category ‘A’ waste. This category consists of gauges and sealed sources, which are commonly used in industry, medical diagnostic and therapeutic sources or devices, and small objects of contaminated equipment. Other category ‘C’ has waste materials arising out of contaminated soils, or contaminated plants or equipments whereas category ‘S’ are the wastes, which are part of sealed sources like gauges or bulk wastes containing radionuclides at higher concentrations. Wastes coming under category ‘S’ cannot be disposed near the surface and has to be retained in storage until an alternative method is adopted for their disposal. (Australian Radiation Protection and Nuclear Safety Agency, 2006: Online).

Nuclear wastes could be solid or liquid wastes, containing radioactive isotopes at several levels considered as disposable. They do not harm if they are properly taken care of or handled with care but can cause harm if dispersed in environment.

To facilitate the disposal of the radioactive wastes, they are generally stored at the site of origin or in a centralized place of storage. Many countries have created a system of low-level waste repositories to dispose of conditioned and packaged low level solid radioactive wastes. These repositories are found near the surface disposal areas like trenches, concrete vault enclosures or other suitable locations, which are underground such as boreholes. Some of the repositories under use today are Centre de l’ Aube in France, Rokkasho-mura in Japan, El Cabril in Spain, Drigg in the United Kingdom, Barnwell and Richland in the United States, Vaalputs in South Africa and Dukovany in the Czech Republic. Conditioned (or packaged) intermediate level waste is generally stored in engineered aboveground facilities. (Australian national nuclear research and development organization.

Many countries are now adopting the methods for the development of geological disposable methods for the disposal of spent fuel and high-level radioactive waste. But there are many other effective ways to create barriers between the waste materials and the environment and the safest method suggested is the “immobilisation of the radioactivity and isolation in storage”. (ANSTO: Online). These methods are chosen according the level and type of activity of the waste. The radioactive wastes that form the Low level and short-lived can be disposed with the help of drums, and can be covered with the cement. The waste materials at intermediate level needs higher level of containments and immobilization techniques including encapsulation in cement, putting it in a glass form or in a bitumen material, or immobilisation into Synroc, a synthetic rock formulation process which is developed in Australia. (ANSTO: Online)

New technologies have also come up for the treatment of low level radio active waste materials and they include vitrification, plasma arc furnace treatment, and molten metal treatment and they all require very high temperatures whereby “at these temperatures, the water is evaporated, and dry materials such as paper, wood, and plastic are vaporized”. (ANSTO: Online) What are left are small quantity of residues containing radioactive materials and large quantity of gases and these gases are collected, taken as sample, treated and then released. The two most important technologies are The Synroc (ANSTO) technology, which has evolved itself to give treatment to the number of waste materials and “lock up the radionuclides in a highly stable matrix” (ANSTO: Online) and now the research is being undertaken overseas to conduct disposal methods known as “partitioning and transmutation”. (ANSTO: Online) In this method, many of the components of radioactive waste materials will be converted in the less hazardous form. But till now success rate of this method is not known.

Reference

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