Surfactant enhanced soil washing (SW) and soil flushing are efficient processes for polycyclic aromatic hydrocarbons removal from contaminated soils. However, management of soil washing solutions is a complex challenge for environmental engineering (Trellu et al., 2016). This study investigated the implementation of a combined process coupling anodic oxidation (AO) using boron-doped diamond anode – an electrochemical advanced oxidation process – and aerobic biological treatment (BT) for proper handling of a synthetic SW solution containing phenanthrene, Tween® 80 and humic acids (Figure 1). As a sole process, AO required a treatment duration of 5 h and a current intensity of 1 A to remove 95% of phenanthrene and Tween® 80 as well as 71% of COD. Such operating conditions resulted in high electrical energy consumption (67 kWh (kg COD)-1). In contrast, BT alone allowed a total degradation of both phenanthrene and Tween® 80 after 2.4 d of treatment, but an insufficient removal of COD (44%) was observed due to the production of non-biodegradable by-products. In order to promote synergistic effects, AO and BT were combined and two different treatment strategies were investigated depending on whether AO was used as pre- or post-treatment. Optimal pre-treatment time and current intensity during the AO pre-treatment were determined by following the evolution of the biological oxygen demand of the pre-treated SW solution. Microtox® analysis also showed that AO pre-treatment decreased the acute toxicity of the initial SW solution. Moreover, degradation of initial compounds led to the production of easily biodegradable by-products such as carboxylic acids. Therefore, the combination of the AO pre-treatment (3 h, 500 mA) with the BT treatment resulted in 80% COD removal. The opposite combination (BT/AO) led to 76% and 93% COD removal after AO post-treatment at 500 mA for 3 h and 5 h, respectively. Thus, non-biodegradable by-products from the BT were removed in an effective way by the AO process. Finally, such combined process appears as a sustainable way to enhance both effluent quality and process cost-effectiveness.
Treatment of soil washing solution by anodic oxidation and biological treatment: A combined approach / Trellu, C.; Ganzenko, O.; Papirio, S.; Oturan, N.; Huguenot, D.; van Hullebusch, E. D.; Esposito, G.; Oturan, M. A.. - (2016). (Intervento presentato al convegno 67th Annual Meeting of the International Society of Electrochemistry tenutosi a L'Aia nel 22-26 Agosto).
Treatment of soil washing solution by anodic oxidation and biological treatment: A combined approach
Papirio S.;Esposito G.;
2016
Abstract
Surfactant enhanced soil washing (SW) and soil flushing are efficient processes for polycyclic aromatic hydrocarbons removal from contaminated soils. However, management of soil washing solutions is a complex challenge for environmental engineering (Trellu et al., 2016). This study investigated the implementation of a combined process coupling anodic oxidation (AO) using boron-doped diamond anode – an electrochemical advanced oxidation process – and aerobic biological treatment (BT) for proper handling of a synthetic SW solution containing phenanthrene, Tween® 80 and humic acids (Figure 1). As a sole process, AO required a treatment duration of 5 h and a current intensity of 1 A to remove 95% of phenanthrene and Tween® 80 as well as 71% of COD. Such operating conditions resulted in high electrical energy consumption (67 kWh (kg COD)-1). In contrast, BT alone allowed a total degradation of both phenanthrene and Tween® 80 after 2.4 d of treatment, but an insufficient removal of COD (44%) was observed due to the production of non-biodegradable by-products. In order to promote synergistic effects, AO and BT were combined and two different treatment strategies were investigated depending on whether AO was used as pre- or post-treatment. Optimal pre-treatment time and current intensity during the AO pre-treatment were determined by following the evolution of the biological oxygen demand of the pre-treated SW solution. Microtox® analysis also showed that AO pre-treatment decreased the acute toxicity of the initial SW solution. Moreover, degradation of initial compounds led to the production of easily biodegradable by-products such as carboxylic acids. Therefore, the combination of the AO pre-treatment (3 h, 500 mA) with the BT treatment resulted in 80% COD removal. The opposite combination (BT/AO) led to 76% and 93% COD removal after AO post-treatment at 500 mA for 3 h and 5 h, respectively. Thus, non-biodegradable by-products from the BT were removed in an effective way by the AO process. Finally, such combined process appears as a sustainable way to enhance both effluent quality and process cost-effectiveness.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
