hazardous wastes

Hazardous wastes

Hazardous substances are chemical that can be harmful to human and organisms. Most of these substances are toxic materials, such as DOT, solvents and lead from both manufactured sources  and natural sources.

A toxic substance as classified as hazardous waste if it handled and disposed of such way that it poses a human health and environment. In other word a toxic substance is hazardous if there is some risk of exposure and harm.

In the world most hazardous waste can be traced to three industrial sources  chemical manufacturing, ,primary metal manufacturing, petroleum refining together they produce about 75 per cent of today hazardous waste stream.

A) Waste produced directly from raw materials processing in chemical, metal and petroleum plant themselves,
b)Wastes produced from secondary manufacturing operations such as plastics and paper plants that use the chemical and petroleum products.
c)Other products include such as pesticides paints that are finally discarded in the environment.

 There are at least six main classes of hazardous waste based on waste composition.

.. Heavy metals (eg.lead,zinc and arsenic)
.. Synthetic organic compounds (e.g. PCB,DDT,DIOXINE)
..Petroleum products (grease,oil,and gasoline )
 ..Biological substances (e.g. Bacteria and plant toxins ) 
..Radioactive materials (e.g. nuclear fuel rods and nuclear medical materials.

These waste are distributed  in the environment by virtually all major land uses. However land uses industry and agriculture are responsible for delivery of most hazardous wastes to the environment. These land uses-are major contributions of organic compounds, heavy metals and acids to soil air and water systems.

Transportation  is also an important hazardous waste delivery agent, especially of petroleum products, mainly through spills and leakage storage tanks.  

Whereas more than  I million square miles of croplands in the world receiving pesticide treatment this is clearly the most wide spread means of hazardous waste distribution to the land .In addition some pesticides residues from farm fields are further dispersed by the atmosphere .  

Waste  management in general could be broadly classified into two main categories the preventive (addressing the cause of waste generation ) and curative (  controlling the harm full effects of wastes.)

.. De materialization of production.
.. Recycling wastes back into production.
..Recovery  of ingredients and or treatment of wastes.
..Dispersal, dumping or storage
De materialization of production, recycling, and concept of cleaner production, industrial metabolism ,and industrial eco-system addressing both preventive and curative approaches.

Treatment of hazardous wastes
Treatment of hazardous waste has  so far involved physical,thermal,chemical  or biological process. More recently biotechnology has provided new options for dealing with hazardous wastes but some of these methods using micro organism have not yet been applied on a scale that would allow proper assessment of their effectiveness.

Finally these remains the necessity of dumping or storing hazardous wastes, which again  has its problems. The volumes of hazardous  chemical waste treated in different ways. It shows that disposal on land or at sea is by far , the most common approach for managing hazardous  wastes. Land fills contaminate   soil causing changes in its micro ecology. Leachates from land fills contaminate surface and ground water with harmful compounds  making such water un usable and threat to human health.

Disposal on the marine environment has diverse harmful effects such as the reduction, alternation  or contamination of fauna or oxygen depletion.

Hazardous waste tend to run down  hill to least regulated and least expensive disposal option unless market forces an such that they direct hazardous waste management  to more appropriate option. The main attraction of land fills is their low cost. For centuries now lightly corrosive and  toxic residues of mining and metal refining process have been accumulating in the neighbor hood of these operation in many part of world without due consideration of their divesting impacts on local environment or damages to human health.

Some hazardous waste are exported to other developed countries that have special treatment facilities but considerable amounts are spited always to less developed region mainly Africa the Asia where they are dumped under highly dangerous conditions. 

It is necessary that scientists and  engineer to search alternative method of disposing the waste chemical to each identified chemical and process to dispose of these chemicals and to save the   environment.