The mass balance of sewage sludge digestion process

Abstract

In Romania, in the coming years, the amount of wastewater collected by sewage systems will be constantly growing. NTPA-011 in Government Decision 188/28.02.2002, updated until 19.10.2011, provides that until December 31st. 2018 all agglomerations areas between 2000 and 10000 population equivalent to be provided with sewerage networks [1].. Many of these human agglomerations are metropolitan areas located near the county capitals. Wastewater collected in these areas are (will be) transported by gravity or by pumping them in municipal wastewater treatment plants already built. Therefore the amount of treated wastewater will increase, causing at the same time, the increase of the processed sludge quantities, and therefore the increase of the specific energy consumption in wastewater and sludge treatment processes. To compensate this increase of energy consumption, wastewater treatment plants operators must find the best solutions for energy recovery from sewage sludge through anaerobic digestion process with the biogas production and thermal treating with heat and electricity recovery [6; 7; 8; 9; 10]. The purpose of this article is to describe the specific features of an anaerobic digestion process for sludge derived from municipal wastewater. The article presents a calculation summary of mass balance on sludge treatment line.