[Use of hydrated lime for disinfection of sewage sludge containing Salmonella typhimurium and Ascaris suum as model pathogens].

Hydrated lime was lethal to the strain of Salmonella typhimurium (Sk 14/39) after 60 min of exposure. In the control without addition of hydrated lime this strain was still viable after 168 hours, counting 6.1 x 10(5) pathogens/l ml sludge. 168-hr disinfection of primary sludges with 10 g/l hydrated lime showed no significant reduction in the viability of Ascaris suum eggs. In three experiments, the number of viable eggs was reduced only by 3.6%. Indicator microorganisms, except psychrophilic ones that survive for only 24 hr, were destroyed after 60 min of exposure. The temperature of stabilized sludges did not vary considerably during experiments, ranging between 21 and 25 degrees C. With the addition of Ca(OH)2, sludge pH increased to the values for COD, organic matters and total nitrogen were reduced throughout the experiments. The values for sludge dry residues remained unchanged.