بررسي ميزان سالمونلادر لجن هضم شده خروجي از هاضم هاي بيهوازي تصيفه خانه فاضلاب شهري

A Survey on the Amount of Salmonella in Digested Sludge of Anaerobic Digesters in Municipal Wastewater Treatment Plant

Objective : In some part of Iran such Isfahan province some farmers tend to use the digested sludge as soil conditioner or fertilizer , and some of the mentioned sludge may content of pathogenic bacterial agents , such as Salmonella . The aim of the present study was therefore, to assess level of contamination by Salmonella products of which are used solely for agricultural purposes . Methods : Peroidic sampling and counting of the level of Salmonella were according to the method presented by American Public Health Association (APHA) and the United State Environmental Protection Agency (EPA). Results : The results showed that the average number of Salmonella in the digested sludge of waste water treatment plant number 1 and Shahinshar , based of the most probable number were 24 and 11 per 4g dried sludge solids, respectively, and were higher than the standard 3 per 4g of dried sludge solids. Hence none of these two plants satisfied U.S. Government Environmental Protection Agency, for use of the sludge in agricultural works. The results taking from statistical analyese using Pearsonʹs correlation coefficien showed that there was a meaningful relationship berween the percentage of reduction of stabilized sludge (organic materials ) and Salmonella for plant number 1 (p=0.009 and r =0.9907 ) and Shahin-Shar digested sludge (p=0.001 and r =0.9885) . Conclusion : These results suggest the greater reduction of the volatile solids correlates with larger reduction in the level of Salmonella .