A review of sludge characteristics in Lithuania's wastewater treatment plants and perspectives of its usage in thermal processes

Sludge samples were collected from seven wastewater treatment plants in the cities of Vilnius, Kaunas, Klaipeda, Siauliai, Panevezys, Alytus and Silute which had populations of 528, 307, 159, 107, 97, 57 and 17 thousand inhabitants, respectively, in 2013. These cities utilized different waste water treatment technologies, and the primary industrial activities in the places selected varied. Heavy metal concentrations and ash melting temperatures were determined based on an analysis of the sludge content, and conclusions for agricultural application and energy production were made. For energy production, co-incineration with municipal waste or wood and gasification are the most reliable ways to utilize sewage sludge. Implementation of such technologies is beginning and further research into these methods is occurring at both the local and international levels.