Sewer systems are an integral part of our modern civilization and are an imperative underground infrastructure asset that our society relies on. In Western Europe alone, 92% of the resident pollution is connected to sewer systems. This extensive coverage of sewerage systems presents an ideal habitation for microorganisms to strive. Sewers can be considered continuous flow bioreactors. They are always colonized by bacteria, either in a planktonic state traveling along the pipe with the water flow or dragged in sediment, or organized as biofilms. Many studies have been devoted to the detrimental effects of microorganisms on sewer systems made of concrete. However, their metabolic activity can also be beneficial, lead to more effective wastewater treatment, or be beneficial for concrete pipes. This aspect has not been thoroughly studied to date and requires further investigation. Therefore, in this Review, we highlighted the positive and negative activity of biofilms and their participation in five proposed mass exchange points in gravity sewers. Furthermore, we systematized and reviewed state of the art regarding methods that could be potentially used to remove or engineer these biological structures to increase the sustainability of sewers and achieve a better pre-treatment of wastewater. We have also indicated research gaps that could be followed in future studies.

下水道系统是我们现代文明的一个组成部分，是我们社会所依赖的必不可少的地下基础设施资产。仅在西欧，92% 的居民污染与下水道系统有关。污水系统的这种广泛覆盖为微生物提供了理想的栖息地。下水道可以被认为是连续流动的生物反应器。它们总是被细菌定植，要么以浮游状态随水流沿着管道移动，要么被拖入沉积物中，要么组织成生物膜。许多研究致力于微生物对混凝土下水道系统的有害影响。然而，它们的代谢活动也可能是有益的，导致更有效的废水处理，或有利于混凝土管道。迄今为止，这方面尚未得到彻底研究，需要进一步调查。因此，在这篇评论中，我们强调了生物膜的积极和消极活动以及它们参与重力下水道中五个提议的质量交换点。此外，我们系统化并审查了可能用于去除或设计这些生物结构以提高下水道的可持续性并实现更好的废水预处理的方法的最新技术水平。我们还指出了可以在未来研究中遵循的研究差距。我们对可能用于去除或改造这些生物结构的方法进行系统化和审查，以提高下水道的可持续性并实现更好的废水预处理。我们还指出了可以在未来研究中遵循的研究差距。我们对可能用于去除或改造这些生物结构的方法进行系统化和审查，以提高下水道的可持续性并实现更好的废水预处理。我们还指出了可以在未来研究中遵循的研究差距。