The invention is directed to an apparatus for delivering activated microorganisms to an environment to be treated. The apparatus has a bioreactor containing microorganisms, a supply of organic and inorganic nutrients and a controller. The controller maintains the conditions of the bioreactor so as to maintain the microorganisms in the exponential phase of growth. Although the apparatus is continuous, the controller also doses a portion of the fluid in the bioreactor to the environment to be treated. The invention also provides a method for the biological treatment of wastes and an organic and inorganic nutrient composition used to feed the microorganisms in the bioreactor.