The opening of the book sets the stage by explaining the authors’ motivation to rewrite and update previously presented papers on sewage treatment. They argue for the superiority of natural methods, simplifying the treatment process and outlining the challenges associated with artificial treatments, including their higher demands and costs. Through initial observations, the authors introduce key concepts regarding the efficacy of aerobic and anaerobic processes, illustrating their findings with examples from established sewage farms. The introduction establishes both the historical context of sewage treatment developments and the authors' intent to clarify these complex processes for a broader audience. (This is an automatically generated summary.)