Sewage sludge eliminating by capitalizing on its energy potential

Abstract

There is an increased concern about the constantly mounting amounts of sewage sludge due to different factors, in particular population growth and urbanization. Therefore, besides common sewage sludge disposal, innovative solutions are required, such as by energy recovery. The present research aimed at evaluation of the energy potential of sewage sludge from a Romanian municipal wastewater treatment plant. A viable and sustainable solution for the removal of sludge is the "transfer" of this so-called waste, in pellets, without any addition of binders. The results of our research may be used to solve two problems, namely, removal of a waste and recovery of energy. The combustion of sewage sludge in the treatment plant offers the following advantages: (i) eliminated transport of the sludge with the significantly decrease over time of the costs for sewage sludge management; (ii) incineration with other solids; (iii) substitution of purchased natural gas or electric energy with local generated energy; cogenerated heat is used in the station for drying the sludge; and (iv) independence of the WWTPs operators from the large energy companies. The results of our study-the fuel properties of seven investigated sewage sludge samples, their determined calorific values and elemental analysis, showed the great energy potential of this type of waste. Experiments to create pellets from sewage sludge through greenhouse solar drying, were also developed and assured the energetic validation by combustion.