SURVIVAL OF MODEL BACTERIAL STRAINS AND H ELMINTH EGGS IN THE COURSE OF MESOPHILIC ANAEROBIC-DIGESTION OF PIG SLURRY

The effect of methanogenesis on the survival of model bacterial strain s (Escherichia coli EC 5, Staphylococcus aureus SA 11, Enterococcus fa ecium CCM 4231) and non-embryonated helminth eggs (Ascaris suum) was i nvestigated in pig slurry. Two pilot-plant experiments were carried ou t in two anaerobic digesters (800 and 1 000 litre) in a mesophilic the rmal range (35-37 degrees C). The mean hydraulic retention time of the digesters was 20 days. The methanogenesis process was monitored by de termining the following chemical parameters: pH, N-NH3, total dry matt er (kg/day); organic matter (kg/day) production of methane by supplied and degraded organic matter (m(3)/kg). The results obtained allow us to state that the anaerobic stabilization of pig slurry in the mesophi lic temperature range resulted in total devitalization of model bacter ial strains E. coli EC 5 and Ent. faecium CCM 42311 St. aureus SA 11 c ells, exposed to the above mentioned conditions, were also reduced in their number from 10.04 to 3.27 and from 8.69 to 2.77 log cfu/ml. It i s assumed that the longer retention time of excrements in the digester could also result in total devitalization of St. aureus SA 11 cells. From the microbiological point of view, the above mentioned facts indi cate a sufficient hygienization effect of the anaerobic fermentation o n the contaminated pig excrements. The survival of A. suum eggs was li ttle affected by the 20-day anaerobic mesophilic digestion of pig slur ry. Only 17 or 18% (F1, F2) of the non-embryonated A. suum eggs were d amaged after the 20-day exposure.