Nitrates are very important for the growth of plants and are useful to human beings and all living organisms as it is a source of nitrogen which forms the building blocks of molecules such as amino acids and DNA and proteins. Though there are many uses but in excess they cause a serious damage to the human health, animals, fish and plants. Denitrification is done by many processes like Blending, Distillation, Reverse Osmosis, Ion Exchange, Membrane Separation, and Biological Denitrification. In this book the removal of nitrate from sewage water is estimated by rotten fruits. Biological Denitrification is easy, environmental favorable, economical and required less maintanence.