The human population is ever growing. Hand in hand with this growing population new human settlements have come up and industries have been set up to fulfill the basic needs. New means of agriculture is adopted by using fertilizers am pesticides to increase the productivity.
All these and much more are practiced for comfortable living. In the bargain, wastes from domestic and industrial activities are dumped into the environment. Consequently, environmental pollution has reached an alarming level and the environment has suffered an irreparable damage. Solid, liquid and gas wastes from the industries; run off fertilizers and pesticides from the agricultural land; am domestic sewage from urban areas has reached a limit beyond disposal.
The problem has been compounded by oil sleeks from crude petroleum tankers. Most causes of this pollution are deliberate. Stringent pollution control legislations are enforced in developed countries Pollution is being monitored and minimized by employing modern techniques. However in developing countries, modern and effective waste treatment facilities are lacking poor financial situations. Conventional waste treatment practices like cesspits, septic tanks, sewage farms, gravel beds, percolating filters and activated sludge processes with anaerobic digestion have been in use in these countries from time immemorial these are less effective and sometimes nonproductive.
The over dependence on the conventional waste treatment facilities is exemplified by the transient break down of, facility in Zermatt, Switzerland. Typhoid broke out following the breakdown of this facility The serious dimensions of environmental pollution are exemplified by severs landmark episodes. The oil tanker, Amoco Cadiz leaked 67 million gallons of crude petroleum into the sea in 1978. A US Air Force fuel storage facility leaked in Charleston, South Carolina in 1975. By 1985, the contamination had spread to residential areas.
The giant oil tanker, Exxon Valdez leaked thousands of tons of crude petroleum along the beaches of Prince William Sound in the Gulf of Alaska in 1998. Underground water sources also show dangerous levels of contaminations. Due to this reason, the underground water sources in the valley of the river Po in North Italy were abandoned forever. Similar underground water pollution has been identified in the river bed of the river Rhine, Netherlands. Bhopal gas disaster in the Union Carbide factory and an accident at the Chernobyl Nuclear Facility are only a few episodes, which remind us of the dreaded dimensions of the environmental pollution.
Thousands of human and other lives were lost in these accidents. In most of the aforementioned cases, synthetic organic compounds, not formed by natural biosynthetic processes, are formed and released into the environment. Such compounds are known as xenobiotics. A few xenobiotics cannot easily be degraded even by microorganisms. These chemical compounds are known as recalcitrants.
Biotechnology offers an opportunity for cleaning the polluted environment in a more effective and time- bound manner. This method was successfully applied to the beaches along Prince William Sound and the Gulf of Alaska. The same method was applied to Charleston, South Carolina to decontaminate the toluene soaked soil. CLASSES OF POLLUTANTS
Hundreds of pollutants, some of which are xenobiotics, are released into the environment either deliberately or accidentally. Some of these are bio-degradable, while others are not under natural conditions. Genetically engineered microorganisms could break down these synthetic organic non-bio-degradable Compounds, which their normal counterparts could not. Some important classes of pollutants are discussed below. 1. Animal and human excreta (Domestic sewage).
2. Biodegradable waste from domestic practice (Domestic sewage). 3. Industrial sewage. (a) Non-halogenated aromatic chemicals: Polycyclic aromatic hydrocarbons (PAHs), Benzene, Phenol, Napthalene, Benzopyrene and Benzoflourene. (b) Halogenated aromatic chemicals: Dry-cleaning solvent (Carbon teU'&ChlQl'ide^ Polychlorinated biphenyls (PCBs), Polybrominated biphenyl (FBB) and Cn'iorop'nenols, cspcda-H-j 4 Heavy metals: Arsenic, Lead, Cadmium and Mercury. 5. Crude Petroleum.
6. Radioactive elements and compounds.