Effects of disinfectant and biofilm on the corrosion of cast iron pipes in a reclaimed water distribution system

Abstract

Chlorine CorrosionReclaimed water distribution system a b s t r a c tThe effects of disinfection and biofilm on the corrosion of cast iron pipe in a model reclaimed water distribution system were studied using annular reactors (ARs). The corrosion scales formed under different conditions were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), while the bacterial characteristics of biofilm on the surface were determined using several molecular methods. The corrosion scales from the ARs with chlorine included predominantly a-FeOOH and Fe 2 O 3 , while CaPO 3 (OH)$2H 2 O and a-FeOOH were the predominant phases after chloramines replaced chlorine. Studies of the consumption of chlorine and iron release indicated that the formation of dense oxide layers and biofilm inhibited iron corrosion, causing stable lower chlorine decay. It was verified that iron-oxidizing bacteria (IOB) such as Sediminibacterium sp., and iron-reducing bacteria (IRB) such as Shewanella sp., synergistically interacted with the corrosion product to prevent further corrosion. For the ARs without disinfection, a-FeOOH was the predominant phase at the primary stage, while CaCO 3 and a-FeOOH were predominant with increasing time. The mixed corrosioninducing bacteria, including the IRB Shewanella sp., the IOB Sediminibacterium sp., and the sulfur-oxidizing bacteria (SOB) Limnobacter thioxidans strain, promoted iron corrosion by synergistic interactions in the primary period, while anaerobic IRB became the predominant corrosion bacteria, preventing further corrosion via the formation of protective layers. ª

Effect of sulfate on the transformation of corrosion scale composition and bacterial community in cast iron water distribution pipes

“…IRB were considered to promote corrosion either by reductively dissolving the protective ferric oxides or by enhancing corrosion itself (Iwona and Christine, 1999). Nevertheless, recent studies indicated that IRB could play corrosion inhibition roles by forming a protective biofilm or reducing dissolved O 2 diffusion (Dubiel et al, 2002;Herrera and Videla, 2009;Wang et al, 2012).…”

Corrosion of galvanized pipes in the hot water supply system

“…Two different classes of microorganisms cause steel pipes corrosion: aerobic and anaerobic types with completely different types of corrosion reactions [11,24]. Microorganisms influence corrosion in several ways [22]: using oxygen by aerobic organisms leads to formation of anodic areas.…”

“…1a, a layer of sediment appeared around the pipe perimeter: tubercles up to 10 mm thick, which resulted in a decrease of effective cross section of the 100 mm pipe by 36 %. The metal surface under sediment has deep ulcers (up to 50% of the wall thickness, Figure 1b In recent years to study the processes occurring in steel and cast iron pipes, people are increasingly using modern methods of pipeline condition monitoring and studying morphology and composition of corrosion deposits [11], including SEM/EDS, which allows reinterpreting the observed facts.…”

Growth kinetics and chlorine resistance of heterotrophic bacteria isolated from young biofilms formed on a model drinking water distribution system

“…This exopolymer matrix confers resistant properties to the whole system via the limitation of the effectiveness of disinfection by consuming the oxidants used, such as chlorine or chloramines. The inactivation mechanism includes the reductive power of the biofilm itself (Wang et al, 2012) and the slow diffusion of oxidants in the biofilm (Lee et al, 2011). In addition, the resilience of biofilm bacteria exposed to oxidant stress (Mathieu et al, 2009) makes chlorination appear to be a relatively ineffective disinfection procedure against biofilms compared to bulk water bacteria.…”