“…Several technologies have been employed to upgrade lagoons, such as extended aeration of aerated lagoons (Melcer et al, 1995), trickling filters (Archer & O’Brien, 2005; Avsar et al, 2008), rotating biological contactors (RBCs) (Hassard et al, 2015) and constructed wetlands (Butterworth et al, 2016; Cameron et al, 2003). In recent years, studies have outlined the use of rock or aggregate‐based attached growth systems (Mara & Johnson, 2006; Mattson et al, 2018; Swanson & Williamson, 1980), stationary in‐lagoon fixed‐film media (Gan & Champagne, 2015; Shin & Polprasert, 1988; Srinivas, 2007) and moving bed biofilm reactor (MBBR) systems (Delatolla et al, 2010; Hoang, 2013; Wessman & Johnson, 2006) to upgrade lagoons either by enhancing microbially mediated nitrification or by increasing the lagoon system’s volumetric or loading capacity. Numerous studies have recently demonstrated the effectiveness of nitrifying attached growth technologies, such as the MBBR to enhance TAN removal performance at the end of lagoons to meet stringent ammonia effluent guidelines at ultra‐low (0.6–3.0°C) temperatures (Ahmed et al, 2019; Almomani et al, 2014; Delatolla et al, 2010; Hoang, 2013; Patry et al, 2019; Young et al, 2016b).…”