Microbiological assessment of sewage sludge hygienization in the process of composting with the use of Salmonella Enteritidis

Abstract

Abstract. The aim of the study is to assess effectiveness of sewage sludge composting efficiency on the basis of survival of Salmonella Enteritidis bacteria. Carriers containing a strain of S. Enteritidis were added to three layers of a compost pile made of dehydrated sewage sludge from a mechanical-biological wastewater treatment plant and wheat straw. The maximum time of the bacteria survival was established which was found to be the longest in the bottom part of the heap and was 58 days, whereas in the top layer of the pile the survival time of the microorganisms was the shortest, which is 49 days. In the thermophilic stage the highest generated temperatures were from 66 to 73 o C for a period of 7 days. It found reflection in the fastest rate of Salmonella bacilli inactivation. A thermophilic stage was also found in the middle layer of the pile which lasted for 5 days throughout which period the temperature ranged from 66 to 72 o C. Temperatures in the bottom part of the pile were found to be lower, from 30 to 61 o C, whereas temperature above 60 o C was reported only for 2 days.

Assessment of microbial contamination of atmospheric air in a selected wastewater treatment plant

“…This is confi rmed by studies (Breza-Boruta and Paluszak 2007) in which the highest fungal content (4600 CFU•m -3 ) was found at the control point located 150 meters from the treatment plant, while in the aeration chambers and in the compost storage area the number of these microorganisms did not exceed 2000 CFU•m -3 . Budzińska et al (2011) also showed that the content of fungi was signifi cant at the control station outside the wastewater treatment plant. At this point, the average number of these microorganisms was higher than at the grit sand catcher and aeration chambers, and comparable to the place of storing sewage sludge.…”

“…In research conducted by Budzińska et al (2011) the highest amount of mesophilic bacteria was isolated in the spring and summer period at grids point (2020 CFU•m -3 ) and in the autumn and winter period at the SBR reactor (1562 CFU•m -3 ). In own studies, a relatively high concentration of bacteria was also found at the aeration chamber, however, their number was more than three times lower (495 CFU•m -3 ) (Fig.…”

“…Research carried out in many wastewater treatment plants indicates that the largest group of actinomycetes occurs at the composting and sewage sludge storage sites (Breza-Boruta and Paluszak 2007, Budzińska et al 2011, Budzińska et al 2013). In the Wastewater Treatment Plant in Tuchów, the actinomycetes were the group of microorganisms that occurred in the air in the smallest quantities (maximum 25 CFU•m -3 ).…”