**Figure 4.**

*Methods of sludge disinfection. Combination of different methods is indicated by asterisks of the same color. By Izydorczyk et al. [34, 51–61].*

*Application of the Sewage Sludge in Agriculture: Soil Fertility, Technoeconomic, and Life-Cycle… DOI: http://dx.doi.org/10.5772/intechopen.104264*

The disinfection approaches should be optimized to minimize potential adverse impacts, such as antimicrobial resistance [62]. Another inherent problem with all sludges rich in nutrients is pathogen regrowth. Offensive odors serve as indicators of microbial regrowth because they are produced as bacteria break down proteins and other organic compounds containing nitrogen and sulfur [63].
