Microbiological quality of sewage sludge in Greece disposed for agricultural use

For the disposal of sewage, sludge landfill is currently the practice adopt ed in Greece. Thirteen wastewater treatment plants located throughout Greec e (islands excluded) were investigated over a period of 1 year in order to determine sludge microbiological quality. The time of exposure of the sampl es to environmental conditions and stress varied considerably, from a few h ours to several months. The mean values for total coliforms were 4 to > 240 0/100 ml and for faecal coliforms <3 to >2400/100. Salmonellae were isolate d from all plants with the exception of two. Parasites were isolated from f ive treatment plants. There was no difference in the bacterial indicator co unts of faecal pollution or the presence of salmonellae and parasites accor ding to the time of disposal of the sludge to the fields. The samples taken from the soil, or from flowers and vegetables which grow in the area of th e sludge disposal were mostly negative for faecal pollution bacteria indica tors. Salmonellae and parasites were not recovered from any samples. Five o f the 16 serotypes reported from the National Salmonella Reference Center w ere present in the sludge samples.