In this study two pilot scale Horizontal Subsurface Flow Constructed Wetlands (HSFCWs) near Lecce, Italy, planted with different macrophytes (Phragmites australis and Typha latifolia) and an unplanted control were assessed for their effectiveness in removing paracetamol. Residence time distributions (RTDs) for the two beds indicated that the Typha bed was characterized by a void volume fraction (porosity) of 0.16 and exhibited more ideal plug flow behavior (Pe=29.7) than the Phragmites bed (Pe = 26.7), which had similar porosity. The measured hydraulic residence times in the planted beds were 35.8 and 36.7 h when the flow was equal to 1 m3/d. The aim of this study was to assess the behavior of BTEX and paracetamol within pilot scale horizontal subsurface flow constructed wetlands built at Sternatia di Lecce, Italy. Specific objective of the experiments is to measure BTEX and paracetamol removal in HSFCWs planted with two different macrophyte species (Phragmites Australis and Typha Latifolia) and compare the removal in the planted reactors with removal in an unplanted control reactor to estimate the relative importance of various potential removal mechanisms. Generally BTEX removals were quite low ranging between 46 to 55%. The latter is probably due to the microbial communities associated with the plant rhizosphere which create an environment conducive to degradation for many volatile organic compounds. The initial concentration of each constituent of BTEX was 0.5 mg/l. The residual concentrations at the sampling points at the end of the phragmites field ranged between 0.23 mg/l (Xylenes and Ethylbenzene) to 0.26 mg/l for Toluene. The final residual concentrations in the typha field ranged between 0.22 mg/l (Xylenes) to 0.26 mg/l (Toluene). In the no planted field the final residual concentrations ranged between 0.26 mg/l (Xylenes) to 0.28 mg/l (Benzene). Greater HRTs (more than 5 days), should be necessary for achieving comparable removal rates for all substances of BTEX. The Phragmites bed exhibited a range of paracetamol removals from 51.7% for a Hydraulic Loading Rate (HLR) of 240 mm/d to 87% with 120 mm/d HLR and 99.9% with 30 mm/d. The Typha bed showed a similar behavior with percentages of removal slightly lower, ranging from 46.7% (HLR of 240 mm/d) to >99.9% (hydraulic loading rate of 30 mm/d). At the same HLR values the unplanted bed removed between 51.3% and 97.6% of the paracetamol. In all three treatments the paracetamol removal was higher with flow of 1 m3/d and an area of approx. 7.5 m2 (half bed) than in the case of flow equal to 0.5 m3/d with a surface treatment of approx. 3.75 m2. A first order model for paracetamol removal was evaluated and half lives of 5.16 to 10.2 h were obtained.
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|Titolo:||Constructed wetlands for recalcitrant organics and emerging pollutants removal|
|Data di pubblicazione:||2012|
|Nome del convegno:||International Symposium of Sanitary and Environmental Engineering, 9th Ed. - SIDISA 2012 - Sustainable Technology for Environmental Protection|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|