Classification and effects of hazardous wastes
The hazardous waste thus includes: (i) Radioactive wastes, (ii) Biomedical wastes
(i) Radioactive Wastes
Radioactive elements decay to produce alpha (a), beta (b) and gamma (c) rays and pose threat to human health. The sources of radioactive materials include:
(a) mining and processing units generating radio isotope
(b) refinery and full fabrication units
(c) discharge from nuclear reactions
(d) radio isotope used in industry, agriculture, medicine and research work
Fortunately, most of the radionuclide's which emit radiations do not persist for a long time in our environment. However, Sr-90 and 1-137 are slow decaying and produce hazardous effects on human life.
Radiation has deleterious effects on living cells. These effects are classified as 'somatic' and 'genetic.'
It is the damage to organism itself. The effect may appear in a short period of time if massive dose is taken. For smaller dose, it takes time and the effect may manifest in malignancies such as leukemia or cancer.
In this case, organism unexposed to radiation can get affected. The radiation might cause gene mutations and chromosome aberrations, as well as changes in number of chromosomes.
Thus, the damage passes from one generation to other generation. The changes result in abnormalities in the offspring. The damage is the maximum in the reproductive organs, the digestive tract and developing embryos.
Disposal of Radioactive Wastes:
Site selection is the most important criteria for radioactive waste disposal. While selecting the site, the climatic conditions of that area, topography and geology should be taken into account so that erosion by wind or flood water does not take place.
The wastes can be disposed off, in ground or in water (ocean). Soil, however, is found to be good absorber of radioactive materials and thus, disposal in ground is a better option.
Radioactive wastes of high level are incorporated in borosilicate glass or ceramic matrix, low level radioactive wastes, i.e., containing strontium can be put in ordinary tank and then sealed.
Nowadays they are buried in suitably designed and constructed underground repositories which remain free from all sorts of disruption by seismic or tectonic activity, for millions of years. The burial location of the radioactive waste is around 500 meters deep.
For low level radioactive wastes, (very small concentration of radioactive materials) the wastes are kept buried for nearly 13 years and finally disposed off in the sea. Before disposing into the sea the toxicity level of the waste is measured and only when it is found to be below harmful levels it is disposed off.
Salt is also a powerful absorber of radiations. Thus, the waste can be buried under salt heaps in vacated mines, covered with 1 to 3 meters of thick layer of soil, sand gravel and crushed rock.
(ii) Biomedical Wastes:
Solid or liquid waste generated from hospitals, clinics, research, testing laboratories and drug companies forms the major component of biomedical waste. Biomedical waste includes:
1. Human or animal anatomical waste and body fluids, consists of tissues, organs, waste body parts, body fluids, blood. For animals these are generated due to the experimental use in research.
2. Microbiological wastes, consists of laboratory culture stocks or specimens of microorganisms, human and animal cell culture used in research.
3. Waste sharps, consists of needle, blades, syringes or laboratory glass used for punctures or cuts.
4. Discarded, expired medicines, glass equipments used for pathological activity, dressings and liquid wastes generated from washing during the use of equipment.