© IWA Publishing 2011 Water Practice & Technology Vol 6 No 3 doi:10.2166/wpt.2011.050 Analysis of the reclamation treatment capability of a constructed wetland for reuse F. Pedrero*, A. Albuquerque**, L. Amado***, H. Marecos do Monte**** and J. Alarcón* *Department of Irrigation, National Council for Scientific Research (CEBAS-CSIC,) Apdo. 164, 30100 Espinardo, Murcia, Spain. Email: fpedrero@cebas.csic.es **Department of Civil Engineering and Architecture, University of Beira Interior, Edificio 2 das Engenharias, Calçada Fonte do Lameiro, 6201-001 Covilhã, Portugal. Email: ajca@ubi.pt ***Department of Civil Engineering, Polytechnic Institute of Guarda, Av. Dr. Francisco Sá Carneiro, n.º 50, 6300-559 Guarda, Portugal. Email: ligia@ipg.pt ****Department of Civil Engineering, High Institute of Engineering of Lisbon (ISEL), R. Conselheiro Emídio Navarro, 1, 1950- 062 Lisbon, Portugal. Email: hmarecos@dec.isel.ipl.pt A research project was conducted during 2008-2009 in Portugal to evaluate the potential of reclaimed water from constructed wetlands for irrigation reuse. A 21 month monitoring campaign was set up in a Filtralite- based horizontal subsurface flow bed. Results showed a significant fluctuation of the hydraulic loading rate that has influenced the hydraulic retention time and the wastewater characteristics over time and, therefore, the removal efficiencies for BOD5, COD, TSS, nitrogen and phosphorus were lower than the reported values for CW performance. If the hydraulic loading rate could be properly controlled the treatment performance, as well as the quality of the reclaimed water, can be improved considerably. The effluent concentrations of conductivity (EC), BOD5, COD, TN, K, Ca, Mg and phytotoxic elements (Na, Cl and B), showed a suitable quality for irrigation reuse according to different international standards, although it is necessary to improve the removal of phosphorous and a final disinfection must be implemented to decrease the pathogenic content. Keywords: constructed wetlands, irrigation, reclaimed water, reuse, treatment capability Water supply and sanitation will be one of the main future challenges in a world of growing population and industrialisation. The growing awareness of water resource scarcity, the competition for water resources and the negative impact of polluted water on human health and the environment, demand the development of adequate strategies for water management. Next to the development of new management strategies to supply fresh water, reclaimed water will play an important role in tackling the existing and occurring water problems (UNESCO, 2009). Approximately half of the European countries, representing almost 70% of the population, are facing water stress issues today (AQUAREC, 2003). Portugal presents some features of Mediterranean climate, particularly in the half of the country located at south of river Tagus. Under a natural regime, according to Marecos do Monte (2007), 57.5% of the country mainland suffers a water deficit that may brings serious consequences to the economy. Constructed wetlands (CW) is considered a low cost wastewater treatment process for small populations and rural areas (Kadlec et al., 2000 Korkusu, 2005) and it seems a suitable system to deal with loads fluctuations (Albuquerque et al., 2009) and to produce a final effluent for reuse (Masi and Martinuzzib, 2007 Marecos do Monte and Albuquerque, 2010). Rural areas in Portugal cover 85% of the territory and 32% of the population in mainland Portugal (INE, 2007). From 1999 to 2006 the percentage of the population served with wastewater treatment plants (WWTP) has increased from 55% to 70% (INE, 2007), in order to Abstract INTRODUCTION

Water Practice & Technology Vol 6 No 3 doi:10.2166/wpt.2011.050 fulfill the requirements of the 1991/271/EEC Directive. In rural areas, strongly investments have been made in low cost WWTP during the last decade, especially in CW treatment systems with horizontal subsurface flow (HSSF). In southern Europe, reclaimed water is used predominantly for agricultural irrigation (44% of the projects) and for urban or environmental applications (37% of the projects) (Bixio et al., 2006). Currently, the use of reclaimed water in Portugal is increasing, although is limited almost exclusively to agriculture irrigation and landscape irrigation. This practice may bring important advantages for the integrated water management in rural areas with water shortage such as the Cova da Beira region, where 60% of the population lives in agglomerates with less than 2000 inhabitants. These rural areas are covered by an irrigation plan to improve agriculture activities and have several golf courses projects and SPA resorts that need large amounts of water. Therefore, the reclaimed water produced in the almost 300 WWTP may be seen as an alternative source for those activities with important environmental and economics benefits. Nnevertheless, some reuse opportunities require a polished effluent since the content of nutrients, heavy metals, microorganism and organic residuals may be not suitable for application. Therefore, the selection of reuse options should be made taking into account a rational analysis on the reclaimed water quality over time, reuse guidelines, climatologically parameters, requirements for polishing treatment and reuse projects cost-effectiveness. A research project (EVAWET) launched in 2007 aims to evaluate both the performance of CW located in rural areas of Portugal and the suitability of reclaimed water for irrigation results. The results of November 2007 to November 2009 are presented and discussed in this paper. A 21 month monitoring campaign (November 2007 to November 2009) was set up in a HSSF CW located at Vila Fernando (Portugal), that started 6 months after its star-up. The bed was colonized with Phragmites australis, filled with Filtralite MR 4-8 mm (a Leca that allows a void ratio of 0.45) and had 23x18 m (length x width), a water depth of 0.5 m and was designed for 800 p.e., maximum flow rate of 50 m3 d-1, maximum hydraulic loading rate (HLR) of 12 cm d-1, minimal hydraulic retention time (HRT) of 4 d, BOD5 from 200 to 400 mg L-1 and COD from 500 to 700 mg L-1. The campaign included the daily measurement of flow-rate (entrance of the HSSF bed) and the collection of monthly samples (a single sampling approximately at the same day and hour) at the influent and effluent of the bed to determine pH, temperature, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH4- N), nitrate nitrogen (NO3-N), total nitrogen (TN), total phosphorus (TP), electric conductivity (EC), sodium (Na), calcium (Ca), potassium (K), chloride (Cl), total coliforms (TC), fecal coliforms (FC), E. Coli, and helminths eggs (HE). In the last sampling month it was also measured magnesium (Mg), boro (B), cadmium (Cd), chromium (Cr), cooper (Co), nickel (Ni), plumb (Pb) and zinc (Zn). Mg was needed to estimate the Sodium Adsorption Ratio (SAR) and B and the heavy metals are fitotoxic parameters and were necessary evaluating their levels. Temperature, pH and electrical conductivity (EC) were measured directly using a Tritilab TIM 900 (Radiometer, France). COD was determined with cuvette tests LCK 614 (50-300 mg L-1) and a CADAS 100 Lange spectrometer (Hach-Lange, Germany) following the standard DIN 38409-4. TN, NH4-N and TP were obtained using the cuvette tests LCK 138 (1-16 mg TN L-1), LCK 238 (5- 40 mg TN L-1), LCK 303 (2-47 mg NH4-N L-1) and LCK 350 (2-20 mg TP L-1) and the same MATERIAL AND METHODS