IMPACT ON SOIL MICROBIAL PROPERTIES AMENDED WITH BIOSOLIDS COMING FROM SEWAGE TREATMENT PROCESSES IN SENEGAL

The aim of this study was to assess the genetic structure of the total community and nitrifying bacteria (ammonia oxidizing bacteria AOB) on horticultural soils amended with an activated or stabilized sludge. DNA extraction, PCR and denaturing gradient gel electrophoresis (DGGE) analysis were performed on soils in laboratory controlled conditions for 21 days. The addition of stabilized or activated sludge in a soil resulted in changes of the total bacterial community structure compared to a control soil without amendment. The incubation of this sludge and soil mixture during 21 days implied an evolution of the diversity of total bacterial community. Sludge amendment did not have a major impact on the nitrifying community (AOB). However, the time of incubation has to be extended to show the long term effect, and long term observations have to be managed when repeated addition or high amendment of sludge is made.