# Municipal Sewage Sludge Disposal in the Republic of Poland
## 6 Conclusions  
The solution to the municipal sewage sludge economy is becoming an increasingly important issue. Directives are being implemented in the European Union countries. According to European regulations, management methods involving storage are currently being replaced by methods leading to the stabilization of sludge and safe recycling. Depending on the quality of the municipal sewage sludge produced and the technology adopted by its producer, it can be processed via recovery or disposal processes. Municipal sewage sludge can be subjected to processing to change its properties and obtain products for reuse or waste with other codes. Based on legal regulations directly influencing the decision regarding the method of MSS management in Poland, it should be emphasized that a very important aspect of the solution for municipal sewage sludge management is the analysis of the possibilities of their disposal at the province/region/country level. An important component of the solution is the physicochemical composition of the sludge itself, particularly the content of heavy metals. The presence of heavy metals in quantities higher than those specified in the Regulation [31] excludes the possibility of using sewage sludge in agriculture or for compost production. In such cases, it is reasonable to use thermal disposal methods (incineration, co-incineration). In such a case, the solution would be a standard installation for thermal processing of sewage sludge for several sewage treatment plants in the province/region. Moreover, in locating sewage treatment plants in areas with no agricultural areas or areas covered by legal protection, the solution may be composting or incineration/co-incineration, and the production of fertilizers or generation sorbents. Currently, in Poland, the most popular method of disposal of municipal sewage sludge is its use in agriculture for crops (27.1%) and thermal processing (-18%). Much of municipal sewage sludge is also used for compost production or land reclamation. Sludge disposal according to the R10 method (i.e., surface treatment with agricultural or environmental benefits) is the relatively cheapest method, where the fertilizing potential of the stabilized and dewatered sewage sludge itself, rich in biogenic compounds such as N or P, is used. The main disadvantage of this process is the need to have access to an appropriate amount of land on which the sewage sludge can be applied (the application of which is subject to very rigorous requirements). In the case of converting sludge into compost under the R3 method, a product is produced that can be used as a fertilizer. Compost improves the physical, chemical, and biological properties of the soil. It improves soil fertility by slowly releasing nutrients such as nitrogen, phosphorus, and potassium. This solution is also widely used in Poland. The method aimed at significantly reducing the flow and mass of sewage sludge produced, and the process of incineration or co-incineration of this waste is also used in Poland. This method is, however, energy-intensive, but, in the case of its use, there are no rigorous requirements regarding the physicochemical characteristics of the sludge. Additionally, in the case of mono-incineration of sewage sludge, it is possible to recover phosphorus from the ashes after incineration, which is in line with the assumptions of the circular economy. Owing to the circular economy (CE), great emphasis is placed on technological solutions enabling recovery or reuse. One recovery method that fits into the circular economy is phosphorus recovery from municipal sewage sludge. Several technologies are known for recovering phosphorus from sewage sludge, both after the thickening and dewatering process, as well as from ashes after the incineration process. The circular economy trend also includes the technology of transforming municipal sewage sludge into waste sorbents (biochar). In addition, this technology can contribute to reducing the amount of raw materials used to produce classic commercial adsorbents.