Reclaimed water from small wastewater treatment facilities in the rural areas of the Beira Interior region (Portugal) may constitute an alternative water source for aquifer recharge. A 21-month monitoring period in a constructed wetland treatment system has shown that 21,500 m(3) year(-1) of treated wastewater (reclaimed water) could be used for aquifer recharge. A GIS-based multi-criteria analysis was performed, combining ten thematic maps and economic, environmental and technical criteria, in order to produce a suitability map for the location of sites for reclaimed water infiltration. The areas chosen for aquifer recharge with infiltration basins are mainly composed of anthrosol with more than 1 m deep and fine sand texture, which allows an average infiltration velocity of up to 1 m d(-1). These characteristics will provide a final polishing treatment of the reclaimed water after infiltration (soil aquifer treatment (SAT)), suitable for the removal of the residual load (trace organics, nutrients, heavy metals and pathogens). The risk of groundwater contamination is low since the water table in the anthrosol areas ranges from 10 m to 50 m. Oil the other hand, these depths allow a guaranteed unsaturated area suitable for SAT. An area of 13,944 ha was selected for study, but only 1607 ha are suitable for reclaimed water infiltration. Approximately 1280 m(2) were considered enough to set up 4 infiltration basins to work in flooding and drying cycles. (C) 2011 Elsevier B.V. All rights reserved.

Most of the wastewater treatment systems in small rural communities of the Cova da Beira region (Portugal) consist of constructed wetlands (CW) with horizontal subsurface flow (HSSF). It is believed that those systems allow the compliance of discharge standards as well as the production of final effluents with suitability for reuse. Results obtained in a nine-month campaign in an HSSF bed pointed out that COD and TSS removal were lower than expected. A discrete sampling also showed that removal of TC, FC and HE was not enough to fulfill international irrigation goals. However, the bed had a very good response to variation of incoming nitrogen loads presenting high removal of nitrogen forms. A good correlation between mass load and mass removal rate was observed for BOD5, COD, TN, NH4-N, TP and TSS, which shows a satisfactory response of the bed to the variable incoming loads. The entrance of excessive loads of organic matter and solids contributed for the decrease of the effective volume for pollutant uptake and therefore, may have negatively influenced the treatment capability. Primary treatment should be improved in order to decrease the variation of incoming organic and solid loads and to improve the removal of COD, solids and pathogenic. The final effluent presented good physical-chemical quality to be reused for irrigation, which is the most likely application in the area. Addresses: [do Monte, Helena Marecos] High Inst Engn Lisbon ISEL,

The experiments concerning the irrigation of three crops (a cereal, a forage crop and an oil–bearing crop) with the final effluent of a plant consisting of a facultative pond treating urban wastewater are described. Control plots were irrigated with potable water and given commercial fertilizers. The results of three years of experiments concerning the crop yields, crop quality both chemical and microbiological are presented. The slightly better crop yield obtained in the plots effluent irrigated lead to the conclusion that the nitrogen content of the facultative pond effluent can replace the nitrogen from commercial fertilizers; subsequent fertilizer savings ranged from US$ 228/ha to US$ 533/ha. Crop composition shows very little or no change due to effluent irrigation. Crop contamination was virtually nil.

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.

The results of two years of experiments about irrigation of sorghum, maize and sunflower with municipal wastewater treated by primary sedimentation and high-rate biofiltration are described. Control plots were irrigated with potable water and given commercial fertilizers. Identical crop yields were obtained for the three treatments,which leads to the conclusion that the nitrogen content of wastewater can replace the nitrogen from commercial fertilizers; subsequent fertilizer savings ranged from US$67/ha up to US$184/ha. No significant crop composition changes were noticed. Soil contamination was negligible at harvest.