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Natural Algal Photobioreactors for Sustainable Wastewater Treatment
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
D. M. Mahapatra, N. V. Joshi, G. S. Murthy, T. V. Ramachandra
Wastewater comprises of organic matter (degraded/partially degraded/inert), particulate/dissolved nutrients/minerals, heavy metals, xenobiotic compounds, pharmaceuticals and emerging contaminants. Various strategies have been employed for removal of nutrients through application of pond systems. For nitrogen (N), the main pond process involved is ammonia volatilization (Kayombo et al., 2010) that often occurs when there is a significant increase in the pond pH due to high photosynthesis. The other processes for N removal comprise of sludge sedimentation, nitrification, de-nitrification, ANAMMOX, etc. (USEPA, 2011; Mahapatra et al., 2013b). The algal ponds have been very efficient in the removal of N as observed in our earlier studies (Mahapatra et al., 2013b; Ramachandra et al., 2016, 2017a, b, c, 2018). Various design configurations have also aided in rapid nutrient removal as in case of the combined pond systems with wetlands that are usually called hybrid systems (Yeh et al., 2010; Ramachandra et al., 2016, 2017a, b, c, 2018). The high rate advanced algal facultative pond systems have also shown higher nutrient removal rates at relatively low HRT (Nurdogan and Oswald, 1995; Veenestra et al., 1995; Veeresh et al., 2010; Craggs et al., 2012). One of the major challenges in the treatment of wastewater is the heavy metals that have very dangerous impacts both on the environment and to human health (Ogunfowokan et al., 2008). Pond systems largely benefit in reducing the concentrations of heavy metals such as Cu, Cr and Ni from pulp and paper mill effluent (Achoka, 2002); Zn and Fe (Batty et al., 2008); Co and Cr (IV) from textile mill effluent (Mona et al., 2011); Pb from industrial w aste (Banerjee and Sarker, 1997) and Al and Ni from acid mine drainage (Kalin and Chaves, 2003). Ponds have been also responsible of higher organic matter removal especially through the initial anaerobic zone or anaerobic pond systems. This has been also accomplished in facultative pond systems where the organic matter is removed in two stages, i.e. a first stage where the organic matter is broken down to soluble organics, carbon dioxide and dissolved mineral nutrients by the bacteria action, and during the second stage the dissolved organics, carbon dioxide and nutrients are taken up by the algal communities. This produces oxygen that is again taken up by the heterotrophic bacteria for decomposition of organic matter, and this cycle repeats. Whereas under high organic loading, in the anaerobic stage, hydrolysis, acidogenesis, acetogenesis and methanogenesis takes place, which converts the bulk of the organic matter to methane, carbon dioxide and water (Chanakya et al., 2012). Just after such processes, the predominance of heterotrophic bacteria and algae increases due to increased mineralization and availability of dissolved soluble nutrients. Various studies have reported treatment of poly aromatics such as PCBs and dissolved organic matter through pond processes (Musikavong and Wattanachira, 2007; Badawy et al., 2010). The pond systems have also demonstrated their utility in treatment of other xenobiotic compounds such as pesticides (Ahmad et al., 2004), pharmaceuticals (Spongberg et al., 2011) and emerging pollutants such as hormones like estrogen (Gomez et al., 2007).
Spatial fractionation of phosphorus accumulating biofilm: stratification of polyphosphate accumulation and dissimilatory nitrogen metabolism
Published in Biofouling, 2022
Didrik Villard, Torgeir Saltnes, Gjermund Sørensen, Inga Leena Angell, Sondre Eikås, Wenche Johansen, Knut Rudi
Ammonium oxidation is considered the rate limiting step of nitrification and is catalyzed by ammonium oxidase, encoded by amoA. Interestingly, the amoA gene was found to be strongly associated with the deeper part of the biofilm, further suggesting that oxygen penetrates to the deeper layers of the biofilm in the oxic zones of the process. Ammonium can also be oxidized anaerobically by anaerobic ammonium oxidation (anammox), a process that has drawn considerable attention as a cost-effective method for nitrogen removal from wastewater (Kuenen 2008). However, no match was found between the 16S rRNA gene analysis and known anammox bacteria in the MiDAS database. It is therefore unlikely that nitrification is driven through anammox in the Hias process. In addition to amoA, the denitrifying gene nar was also strongly associated with the deeper part of the biofilm. This indicates that both nitrification and nitrate reduction occur in the deeper layers of the biofilm.
Subsea tunnel reinforced sprayed concrete subjected to deterioration harbours distinct microbial communities
Published in Biofouling, 2018
Sabina Karačić, Britt-Marie Wilén, Carolina Suarez, Per Hagelia, Frank Persson
The ammonia-oxidising archaeon Nitrosopumilus sp. was observed at a particularly high abundance and ammonia-oxidising bacteria within the Nitrosomonadaceae were consistently detected. Nitrite-oxidising bacteria within Nitrospina, as well as Nitrospira, were also common, as were anammox bacteria within Ca. Scalindua. The autotrophic nitrogen converters were typically marine clades, well adapted to low substrate concentrations and able to tolerate low oxygen environments (Lücker et al. 2010; Park et al. 2010; Lücker et al. 2013) or anoxic conditions (Schmid et al. 2007), which may assist in explaining their abundance in the biofilms having a range of DO concentrations (Figure 8). Concrete deterioration associated with the activities of nitrifying bacteria has been observed in various concrete infrastructures (Cwalina 2008; Noeiaghaei et al. 2017). In the Oslofjord tunnel the nitrifiers may have contributed to the deterioration of the sprayed concrete, but only to certain degree given the low concentrations of nitrogen species in the water. Iron-oxidising bacteria of Mariprofundus sp. were detected in the biofilm at high abundance. They oxidise Fe(II) to Fe(III) at microaerophilic conditions and neutral pH, as was detected in the biofilm. During growth, Mariprofundus cells excrete extracellular stalks rich in polysaccharides and Fe(III). Such twisted stalks rich in iron were observed by SEM (Figure 7, Table 3), confirming their activity in the biofilm. The stalks are structures for deposition of metabolic products, which prevent cell encrustation and increase the solubility of Fe(II), thereby increasing the corrosion process (Chan et al. 2011; McBeth et al. 2011). The presence of Mariprofundus helps to explain the observed corrosion of the steel fibres in the sprayed concrete, the orange biofilm colour, and the high iron concentration in the biofilms (Table 2). The biofilm also contained high concentrations of precipitated manganese. However, no known manganese-oxidising bacteria were detected in the biofilms, as similarly observed in a preliminary investigation in the Oslofjord tunnel (Karačić et al. 2016). Yet, microorganisms resembling Leptothrix discophora were previously observed by SEM on samples collected at the Pump Station in 2005, when the water flow was much lower (Hagelia 2011a). Profound biogenic manganese oxidation has, however, been detected without identification of any known manganese-oxidising bacteria based on 16S rRNA gene sequences (Cao et al. 2015), suggesting that this trait is not only restricted to the phylogenetically diverse group of established manganese oxidisers. In addition, the biofilms contained a diversity of heterotrophic bacteria typically found in marine water and sediment including members of the marine benthic group JTB255 (Mußmann et al. 2017), Saprospiracae (McIlroy and Nielsen 2014), Kordiimonadaceae (Xu et al. 2014) and Marinicella (Rua and Thompson 2014). These organisms were presumably utilising the small bioavailable fraction of organic matter in the water as well as organic matter from internal cycling of biofilm components.