The importance of sewer biofilms

Abstract

In spite of being under ground and out of sight, sewers are important parts of the urban infrastructure for transporting used, contaminated water for safe treatment. Within sewers, during the transport of waste water, processes take place, transforming the chemical components of the waste water. These processes are largely carried out by bacteria, a significant part of which live in biofilms. These microbial processes impact the sewers by causing odor and corrosion of the sewer pipes, leading to the need costly repair and control strategies. The biofilms may also impact the environment by contributing to greenhouse gasses in the atmosphere and pollution in natural aquatic environments. However, improved understanding of the function of biofilms and the novel techniques and approaches for manipulating biofilms may provide us with strategies for controlling these problems. Moreover, such advances may allow us to design in-sewer biofilms for beneficial purposes such as in-pipe treatment of waste water, potentially leading to decreased environmental impact. © 2016 The Authors. WIREs Water published by Wiley Periodicals, Inc. How to cite this article:WIREs Water 2016Water , 3:487-494. doi: 10.1002Water /wat2.1144 INTRODUCTION S ewers are extremely important components of urban infrastructure that helps keep the urban environment safe from flooding and prevents the spread of water-borne diseases by safely transporting waste water to the waste water treatment works and through the transport of rain water from urban surfaces.1 Naturally, the focus on sewer design and construction has been on the function of the sewer networks with respect to safe transport of water to fulfill this vital role within urban infrastructure. However, over the years, the understanding of sewer function has been expanded, so that expectations of the urban drainage systems is now also to help minimize the impact of urban activities on the natural environment 2,3 and to prevent odor from waste water in the urban environment. 4 In light of increasing expectations, it is necessary now, more than ever, to design robust sewer networks to fulfil the expected design life of 50-100 years. Existing sewer networks are under increasing strain mainly due to population growth, increasing urbanization, and climate change. The increasing strain on the sewers manifests itself as operational failures leading to flooding events, increased loads on treatment facilities leading to poor quality of water discharge, and leaks linked to enhanced structural deterioration due to concrete corrosion. Early on in the history of the modern sewer networks, it was discovered that the degradation of the materials that the sewers are built from, i.e., mostly concrete, is a consequence of the environment within the sewers. 5 This has led to an increased focus on the processes taking place inside the sewers during the transport of the waste water. 6 It is now generally recognized that the chemical transformations of the waste water and the environmental conditions in the sewers...

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