[Extract] The world population started to increase at a faster rate from the early 1800s which inevitably led to the generation of the wastes in the forms of the solids, liquids and gases. These wastes contributed significantly to the ill health of the population since then and forced scientists, microbiologists and others to find ways to treat them. Fig. 1 shows the population increase in every fifty years since 1800 along with scientific findings that are related to the improvement of human health. The figure also shows the industrial development that occurred alongside which obviously deteriorated the environment further. The naturally occurring aerobic and anaerobic processes in carbon, nitrogen, phosphorus, and sulphur cycles helped the scientists to further their knowledge on treating all the three forms (solids, liquid and gaseous) of the wastes to reduce their impact on the environment as well as the health of the humans and other living organisms
