Pathogens are inactivated or killed through disinfection to provide for safe sludge handling and land application. Most common are thermal and chemical disinfection methods, e.g. by addition of lime. Thermal processes require sludge heating to a certain temperature and maintaining it at this temperature for a certain duration, which depends on the temperature. Common time-temperature relationships are e.g. 30 minutes at 70 °C, or 1 day at 55 °C. Thermal disinfection of liquid sludge (pasteurization) can be performed prior to or during biological stabilization. Sludge can also be disinfected by thermal sludge drying.
Thermal disinfection processes include recovery of the majority of the heat, e.g. with sludge-sludge heat exchangers. To prevent clogging and blocking of such heat exchangers, we recommend prior screening with our Strainpress® Sludgecleaner. This sludge screen reliably removes disturbing solids, such as hair and fibres, from raw sludge and substantially improves heat exchanger operation. The removed screenings are simultaneously compacted in this machine.
Sludge is not only dried in our HUBER Middle-Temperature Belt Dryer BT, but simultaneously disinfected, if the dryer is operated at sufficient temperature with sufficient sludge retention time. We could prove this recently at one of our full-size belt dryer installations, where the sludge reached a temperature above 70 °C for over 20 minutes.