Athens - Psyttalia

The Psyttalia Wastewater Treatment Plant (WWTP) is the final recipient of domestic sewage and pre-treated industrial wastewater from the Greater Athens area in Greece. 

In order to improve the energy footprint of the WWTP, the application of the thermal hydrolysis process (THP) was preferred to the option of constructing additional anaerobic digestion tanks. Since August 2015, approximately half of the generated waste activated sludge (WAS) has been treated by a Cambi B6-4 system. The thickened primary sludge stream by-passes THP and is mixed with the hydrolysed WAS stream before entering four of the plant's eight digesters. The four other digesters treat the remaining non-hydrolysed WAS load.  

After more than a year of THP operations, the dewaterability of the mixed sludge significantly improved, while biogas generation and digester efficiency in terms of solids destruction increased. The THP unit also substantially reduced energy use and costs for the sludge drying plant of Psyttalia.