Thermal hygienization of excess anaerobic sludge: a possible self-sustained application of biogas produced in UASB...

The main current trends in final disposal of sludge from Wastewater Treatment Plants (WTP) include: safe use of nutrients and organic matter in agriculture, sludge disinfection and restricted use in landfill. As to sludge hygienization, helminth eggs have been used as a major parameter to determine the effectiveness of such process, and its inactivation can be reached by means of thermal treatment, under varying temperature and other conditions. In such context, the objective of this research was to determine how effectively biogas produced in UASB reactors could be used as a source of calorific energy for the thermal hygienization of excess anaerobic sludge, with Ascaris lumbricoides eggs being used as indicator microorganisms, and whether the system can operate on a self-sustained basis. The experiments were conducted in a pilot-scale plant comprising one UASB reactor, two biogas holders and one thermal reactor. The investigation proved to be of extreme importance to developing countries, since it leads to a simplified and fully self-sustainable solution for sludge hygienization, while making it possible to reuse such material for agricultural purposes. It should be also noted that using biogas from UASB reactors is more than sufficient to accomplish the thermal hygienization of all excess sludge produced by this system, when used for treating domestic sewage.