Reclamation with phytoremediation of area affected by sewage sludge at the Thessaloniki Wastewater Treatment Plant in Sindos (Greece)

The present research focused on the experimental investigation of phytoreclamation of areas affected by sewage sludge disposal and improving the quality of the sludge. It was conducted in two stages: laboratory and pilot applications. This paper reports on the first stage, which tested, under greenhouse conditions, the possibility of using various species of plants cultivated in the sludge from the Thessaloniki Wastewater Treatment Plant (ThWWTP, Greece) with different amendments. The results of the 30-day experiment showed that the quality of the output sludge material varied significantly in comparison to the input sludge material. These variations were considered as positive, as the output sludge obtained texture and structure, aeration conditions were improved, and the content of some trace metals, excess nutrients (e.g., P), and salts (of Na) were reduced. These were all influenced by both the type of treatment and the plant species used. In conclusion, the best treatments, T1, T3, and T4 (soil/sludge mixture 70%/30%, soil/sludge/gravel mixture 50%/25%/25%, and soil/sludge/gravel mixture 45%/45%/10%, respectively), and the best suited plant species, Helianthus annuus L. and Zea mays L., were proposed to be used in the pilot application (in situ) at the site within the ThWWTP.