| Abstract |
A dynamic development of sewer networks and municipal wastewater treatment plants (WWTPs) leads to the formation a large amounts of municipal sewage sludges (MSSs) which have to be disposed. One of the MSS disposal practices is thermal conversion in mono-incineration plants. Nowadays, there are 11 such installations in Poland, with the total capacity 160,300 Mg d.w. of MSSs per year. This paper presents a comprehensive analysis of wastes generated in Polish MSS mono-incineration plants. As a consequence of MSSs incineration, various types of waste are generated including, for example, bottom and fly ash, dust or solid waste. The most valuable waste is sewage sludge ash (SSA), which can be used in other industries, as fertilizer or construction sectors. In the circular economy (CE) model, SSA should be treated as a secondary source of raw materials, such as phosphates (replacement of nutrients by P-rich ashes in fertilizers) or sand (replacement of sand by ashes in construction materials). Current practices of SSA management include landfilling, recovery at WWTPs or management by external companies (recovery, disposal or collection). To preserve the utility value of SSA, it should be stored selectively, and then directed to raw materials recovery. This creates the possibility of turning waste into a secondary resource, after meeting certain conditions which depend on which product the waste is directed to. Moreover, this waste management practice is recommended in the Polish documents regarding the usage of SSA, and it can strengthen the accomplishment of the European Green Deal, which is the newest roadmap for making the EU's economy sustainable and circular. |