Behaviour of Enteric Micro-organisms during Composting of Rural Sewage Sludge

Introduction The spreading of sludge will only be possible on the condition of being able to guarantee to farmers and consumers the harmlessness of this practice. To minimize the potential risk for the health of humans and animals, it is necessary to coordinate sludge applications in time with planting, grazing or harvesting operations. For these reasons, sludge could not be applied continuously and must be stored in tanks during about 6 months before application. In this context, we studied the effect of sludge co-composting on survival of bacteria present in sludge stored in a tank of a rural water treatment plant. Enumeration of bacteria covered one whole compost cycle lasting from fresh sludge to mature compost for a period of 7 months. Temperature and bacterial densities were measured in three relevant locations on the pile including the side of the incoming air flow (incoming air area), the bottom (in the middle of the pile) and the top of the pile (outcoming air area).