Changes in Microbial Biofilm Communities during Colonization of Sewer Systems

Abstract

bThe coexistence of sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) in anaerobic biofilms developed in sewer inner pipe surfaces favors the accumulation of sulfide (H 2 S) and methane (CH 4 ) as metabolic end products, causing severe impacts on sewerage systems. In this study, we investigated the time course of H 2 S and CH 4 production and emission rates during different stages of biofilm development in relation to changes in the composition of microbial biofilm communities. The study was carried out in a laboratory sewer pilot plant that mimics a full-scale anaerobic rising sewer using a combination of process data and ). This contrasting trend coincided with a stable SRB community and an archaeal community composed solely of methanogens derived from the human gut (i.e., Methanobrevibacter and Methanosphaera). In turn, CH 4 emissions increased after 1 year of biofilm growth (327.6 ؎ 16.6 mg COD-CH 4 liter ؊1 day ؊1 ), coinciding with the replacement of methanogenic colonizers by species more adapted to sewer conditions (i.e., Methanosaeta spp.). Our study provides data that confirm the capacity of our laboratory experimental system to mimic the functioning of full-scale sewers both microbiologically and operationally in terms of sulfide and methane production, gaining insight into the complex dynamics of key microbial groups during biofilm development. W astewater collection systems, or sewers, consist of an underground network of physical structures-installations composed of pipelines, pumping stations, manholes, and channels that convey wastewaters from their source to the discharge point, usually a wastewater treatment plant (WWTP). Sewer systems thus prevent the direct contact of urban populations to fecal material and potential microbial pathogens, greatly reducing the spread of infectious diseases. Sewers have traditionally been considered only hydraulic transport systems for sewage, although they are in fact "reactors" where complex physicochemical and microbial processes take place. Wastewater microorganisms are diverse and abundant, and they are exposed to a wide range of both inorganic and organic substrates as well as changing conditions along their transport through sewers (1). In this regard, wastewater transport through the pipes facilitates the formation of microbial biofilms that grow attached to the inner surface of sewer pipes (2). Different factors, such as large surface area, low flow velocity near pipe walls, and nutrient availability, may favor microbial colonization of pipe surfaces and biofilm growth. Formation of fully functional biofilms occurs in different steps, from surface conditioning, adhesion of microbial "colonizers," initial growth, and glycocalyx formation, followed by secondary colonization and growth (3).Anaerobic conditions in sewer pipes favor the accumulation of both sulfide (H 2 S) and methane (CH 4 ) as end products of different microbial metabolisms, i.e., anaerobic respiration of organic matter by sulfate-reducing bacteria (SRB) and methanogenic archae...

From grass to gas: microbiome dynamics of grass biomass acidification under mesophilic and thermophilic temperatures

“…4, Leach Bed). The occurrence of Methanosaeta in biofilms has been reported previously [53, 54]. This result highlights the need for a separate analysis of leach-bed samples and associated biofilms.…”

Soil biofilms: microbial interactions, challenges, and advanced techniques for ex-situ characterization

“…For example, with anaerobic biofilms developed on the surfaces of sewer pipes, sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) compete with each other for substrates including organic matter, acetate and hydrogen. SRB were dominant in the initial phase of biofilm formation but, on maturation, methanogenic colonizers were better adapted and replaced the SRB (Auguet et al, 2015). Competition pressure for nutrients is particularly high among phylogenetically similar strains in soil, marine and other natural environments (Hawlena et al, 2010;Schoustra et al, 2012;Patin et al, 2016).…”

Assessment of Chemical Inhibitor Addition to Improve the Gas Production from Biowaste

“…However, it is to be noted that the harmful effect of molybdate supplementation on the SRB and methanogens and therefore, on the H2S and CH4 generation makes this treatment an interesting option on other fields, as sewerage system. Since, anaerobic conditions in sewer pipes favor the accumulation of both H2S and CH4 and these compounds have detrimental effects on the sewer system, with different consequences for both the installation and its surroundings (Auguet et al 2015) (such as malodor, health hazards due to the well-known toxicity of H2S, and corrosion of both the inner surface of pipes and the inlet zones of waste water treatment plants, etc)…”

“…Besides, it greatly affects the flammability of biogas when used directly in burners (Rasi et al 2007;Muñoz et al 2015). In addition, H2S causes malodor and health hazards due to the well-known toxicity and material corrosion tendencies (Auguet et al 2015). The nutritional requirements of SRB include an inorganic electron acceptor which is usually provided by sulphate ion and an electron donor which essentially consist of VFA or H2 and occasionally sugars and long chain fatty acids.…”

“…Studies involving use of inhibitors to suppress activity of SRB and, consequently, promote growth of methanogens have been reported in literature (Ranade et al 1999;Isa and Anderson 2005;Patidar and Tare 2005;Chen et al 2008). However, other studies documented that SRB and methanogens could have a symbiosis between them (Vossoughi et al 2003;Zahedi et al 2013a;Auguet et al 2015), although these organisms are constantly competing as electron acceptors. Therefore, the feasibility of using SRB inhibitor for the control of sulphate reduction and the improvement of methane production in biological reactor are not established.…”