INTRODUCTION

There are many innovative biological technologies for the treatment of wastewaters and sludges. Four such technologies that have now become widely accepted worldwide are considered below: these are stabilization ponds, the use of plants and wetlands, biological nutrient removal (BNR) systems and composting. However, it is in the area of biotechnology that many of the new technologies are evolving. Biotechnology is the exploitation of living organisms, generally micro-organisms, or biological processes in an industrial or commercial situation to provide desired goods or services. Biotechnology is not a distinct discipline but rather a result of four traditionally separate disciplines: biochemistry, microbiology, engineering and chemistry, interacting with each other. Although the term biotechnology has only become widely studied as a subject in its own right since the mid-1970s, humans have used many biotechnological processes for centuries, such as the exploitation of yeasts in baking and brewing, or bacteria to ripen cheese. New strains of micro-organisms can be developed which produce a desired substance in far greater quantities or degrade a particular substrate far more efficiently than the original parent strain. While this can be achieved by careful culturing and selection, the most important advance is the development of genetic manipulation, known ubiquitously as genetic engineering. This involves the transfer of genetic material from one cell to another to modify that cell s behavior to benefit some industrial process. Turning the bacterial cell into a factory capable of producing enzymes, vaccines, amino acids, steroids or other cellular products such as insulin and interferon...