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- Evaluation of different substrates to support the growth of Typha latifolia in constructed wetlands treating tannery wastewater over long-term operationPublication . Calheiros, Cristina S. C.; Rangel, António O. S. S.; Castro, Paula M. L.The aim of this study was to investigate the performance of horizontal subsurface flow constructed wetlands planted with Typha latifolia treating tannery wastewater under long-term operation. Two expanded clay aggregates (Filtralite® MR3–8-FMR and Filtralite® NR3–8-FNR) and a fine gravel-FG were used as substrate for the constructed wetland units plus one unit with FMR was left as an unvegetated control. The systems were subject to three hydraulic loadings, 18,8 and 6cm d⁻¹, and to periods of interruption in the feed. The relationship between the substrate, plant development and removal efficiency, especially of organic matter, was investigated. Organic loadings up to 1800 kg BOD5 ha⁻¹ d⁻¹ and 3849 kg COD ha⁻¹ d⁻¹ were applied leading to mass removals of up to 652 kg BOD₅ ha⁻¹ d⁻¹ and 1869 kg COD ha⁻¹ d⁻¹, respectively. The three different substrates were adequate for the establishment of T. latifolia, although the clay aggregates allowed for higher plant propagation levels. The units with FNR and FMR achieved significantly higher COD and BOD₅ removal when compared to the FG and to the unplanted units. The systems proved to be tolerant to high organic loadings and to interruptions in feed suggesting this technology as a viable option for the biological treatment of tannery wastewater.
- Constructed wetlands for tannery wastewater treatment in Portugal: ten years of experiencePublication . Calheiros, Cristina S. C.; Rangel, António O. S. S.; Castro, Paula M. L.Wastewaters from tannery industry are complex in composition and providing adequate treatment can be difficult. Constructed wetlands (CW) are regarded as an alternative treatment to the conventional biological systems, as a developing cost-effective and environmentally friendly phytoremediation technology. The present review compiles and integrates information on CWs technology for the needs of the tannery sector. The following issues arise as crucial for the implementation of such systems, namely i) an accurate wastewater characterization and an effective pretreatment before reaching the CW, ii) choosing the plants species better adapted to the imposed conditions, iii) substrate selection and iv) range of organic loadings applied. The examples practiced in Portugal give indication that horizontal subsurface flow systems, with expanded clay media, are a suitable option to be considered when dealing with high organic loading tannery wastewater (up to c.a. 3800 kgCODha−1d−1), being resilient to a wide range of hydraulic variations. Plants such as Phragmites and Typha have shown to be adequate for tannery wastewater depuration, with Arundo donax proving resilient to high salinity wastewaters. The flexibility of implementation allows the CW to be adapted to different sites with different configurations, being suitable as main secondary or tertiary treatment stage.
- Biological processes for industrial wastewater treatment- case study in the leather industryPublication . Calheiros, Cristina S. C.; Rangel, António O. S. S.; Castro, Paula M. L.
- Constructed wetland with a polyculture of ornamental plants for wastewater treatment at a rural tourism facilityPublication . Calheiros, Cristina S. C.; Bessa, Vânia S.; Mesquita, Raquel B. R.; Brix, Hans; Rangel, António O. S. S.; Castro, Paula M. L.Sewage management in remote rural and mountain areas constitutes a challenge because of the lack of adequate infrastructure and economic capability. Tourism facilities, in particular, possess a special challenge because of huge variability in sewage production and composition as a consequence of variations in number of guests and their activities. Constructed wetlands (CWs) are recognized as a robust and economical ecotechnology capable of meeting these challenges. A horizontal subsurface flow CW system was established at a guest house located in a rural and mountain area of Portugal. The substrate of the bed was an expanded clay substrate, and the system was planted with a polyculture of ornamental flowering plants (Canna flaccida, Zantedeschia aethiopica, Canna indica, Agapanthus africanus and Watsonia borbonica). The load and composition of sewage varied significantly seasonally (17–579 kg COD ha−1 d−1), but removal efficiencies of BOD and COD were generally high (>90%) and independent of the loading conditions. The system also reduced PO43− (up to 92%), NH4+ (up to 84%) and total coliform bacteria (up to 99%). The ornamental polyculture provided an aesthetic pleasing system with different appearance during the seasons. Of the five species tested, four grew well (C. flaccida, C. indica, Z. aethiopica and W. borbonica), whereas A. africanus was outcompeted. The system owner cut flowers from the CW system and used them for decorations at the guest house. It was demonstrated that CW systems planted with a polyculture of ornamental plant species, besides the water treatment function, possess several additional benefits including aesthetics and biodiversity enhancement.