Sustainable Solutions for Environmental Pollution, Volume 2. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
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Жанр произведения: Биология
Год издания: 0
isbn: 9781119827641
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and floating mats, in more “rugged” environments to study problems such as death of macrophytes, deformation and/or sinking of floating mats, and protection against plant predators (e.g., swans and ducks).

      Characteristics that influence the effectiveness of FT-CWs are water depth, aquatic vegetation chosen, harvesting or maintenance of aquatic plants, presence of aeration in primary treatment, and seasonal fluctuations in temperature (Pavlineri et al., 2017; Prajapati et al., 2017; Shahid et al., 2018). Initially, natural FT-CWs were used to treat wastewater (Shahid et al., 2018). The application of FT-CWs has become more common in recent years, with the first applications in lakes and rivers in Germany and Japan (Shahid et al., 2018). Since then FT-CWs has become more broadly adopted, such as in the treatment of domestic and mine wastewater, agricultural and storm water runoff, eutrophic water bodies (Pavlineri et al., 2017; Shahid et al., 2018). Applications to improve water quality can be to introduce FT-CWs into various effluent treatment plants (domestic, agricultural, industrial, and mining) (Pavlineri et al., 2017; Prajapati et al., 2017).

      1.10.3 Electro-Bioremediation

      Recent developments in electro-microbiology are paving the way for new technologies to improve bioremediation processes without the addition of any chemicals in polluted aquatic environments to be treated. Moreover, electro-bioremediation makes it possible to obtain direct degradation products through electrochemical management of microbial consortium and to control greenhouse gases (GHG) or other noxious gas emissions (Namour and Jobin, 2018).

      Our definition of electro-bioremediation excludes the electrokinetic (EK) techniques (Reddy and Cameselle, 2009; Barba et al., 2018; Kaushal et al., 2020). EK is mainly aiming at extracting pollutants after transport over long distances in an electric field. But the application of weak electric fields can have a negative effect on the pollutant-degrading biofilm, electrolyze the pore water, cause pH changes at the cathode, and produce reactive oxygen or chlorine species with antimicrobial effects near the anode (Liu et al., 1997).

      In electro-bioremediation, instead of optimizing the collection of as many electrons as possible or injecting energy to catalyze the degradation of pollutants, electron flows are regulated via an external resistance control in order to maintain an anodic microbial consortium in optimal conditions for the biodegradation of OM. The maximal potential difference between oxygenated superficial water and anoxic sediments generally reaches approximately 800 mV (Ryckelynck et al., 2005; Donovan et al., 2008; Zhang et al., 2011; Yang et al., 2015; Gonzalez-Gamboa et al., 2017). The greater the TEA potential difference, the higher the energy gain for the bacteria. The external resistance is therefore the relevant parameter to control the performance of the anode biofilm (Ren et al., 2011). A proper anodic potential poised between 0 and 100 mV (NHE) can both enhances OM oxidation (bioremediation enhancement) and cuts noxious gas production (H2S, CH4, and N2O) generated at lower potentials (Jeon et al., 2012). Indeed, electro-bacteria competing with methanogens for OM have half-saturation coefficients lower than methanogens: e.g., Geobacter sulfurreducens: 10μM (Esteve-Nunez et al., 2005) versus Methanosaetaceae: 169μM and Methanosarcinaceae: 3.4mM (Qu et al., 2009). Electrobioremediation stimulates OM removal without chemical or energy inputs, so the operational cost can be significantly lower with other remedial methods. But it is able to lead to higher treatment efficiencies than other bioremediation technologies (Logan et al., 2006; Huang et al., 2011; Wang and Ren, 2013).

      Three levels of electro-bioremediation setups exist: 1) bench tests on lab-scale microbial fuel cell (MFC) with a volume <1L; 2) pilot tests on semi-industrial devices (>1 L); and 3) in-field tests on quasi-full-scale. The two first levels deal with Sediment MFCs, and only the last one concerns actually Benthic MFCs.

      1.10.4 Bench Tests

      Since electro-bioremediation involves a microbial consortium, it takes time to become operational: prior enrichment of the electrodes (bio-augmentation) accelerates the biodegradation capacities (Venkidusamy et al., 2016). The potential difference measurement between the anode and the cathode provides a way to monitor the set up progress of the microbial consortium, and its stabilization time varies with the device size. In bench tests it stabilizes after about 10 days: it takes 2 to 3 days in marine sediment (Najafgholi and Rahimnejad, 2016); 10 days in swamp sediment (Gonzalez-Gamboa et al., 2017) and Diesel-fed sludge (Venkidusamy et al., 2016); 13 days in tidal mud (An et al., 2010); and around 20 days in waterlogged soil (Yu et al., 2017; Zhang et al., 2020b). In pilot tests, it stabilizes about some tens of days: 35 days in TF-CWs (Arends et al., 2014; Schievano et al., 2017) crude oil contaminated marine sediment (Hamdan and Salam, 2020), and waste-contaminated river sediment (Yang et al., 2015); over 40 days in FSF-CWs (Oon et al., 2016). In field-experiments, because of the size, the voltage stabilization time is supposed to be longer.

      1.10.5 Pilot Tests