This publication provides guidance to water-sector decision makers and planners on how to deal with the quality dimension of groundwater resources management in the World Bank's client countries. There is growing evidence of increasing pollution threats to groundwater and some well-documented cases of irreversible damage to important aquifers. This guide has been produced in the belief that groundwater pollution hazard assessment must become an essential part of environmental best practice for water supply utilities. The guide is particularly relevant for the World Bank's Latin American and Caribbean Region, where many countries have initiated major changes to modernize their institutional and legal framework for water resources management, but may not yet have considered groundwater at the same level as surface water, because of lack of awareness and knowledge of groundwater issues and policy options.

Resumen: Este estudio evaluó la eficiencia de eliminación de materia orgánica (DQO), nitrógeno (NH4+, NO3 -) ortofosfatos, y coliformes totales y fecales en cuatro humedales construidos de flujo subsuperficial horizontal a escala piloto usando dos especies de plantas locales. Dos sistemas fueron plantados con Cyperus ligularis y dos con Echinochloa colonum. El experimento constó de un tanque de almacenamiento de 760 litros (tratamiento primario), desde donde se vertió el agua residual, mediante tubería de PVC, al sistema de humedales. Cada humedal fue rellenado con grava granítica de unos 8 mm de diámetro y porosidad de 0.4. Una vez al día y durante cuatro meses, se adicionó a los humedales un caudal de 42 l.día-1, para mantener un tiempo de residencia hidráulico de tres días. Las muestras de agua residual (afluente y efluente) se recolectaron tres veces por semana para determinar la concentración de DQO y nutrientes. Una vez por semana se determinó coliformes fecales y totales. La eliminación de DQO, amonio, nitrato y ortofosfatos fue de 93, 65, 71 y 32%, respectivamente, para C. ligularis, y de 85, 54, 67 y 57%, respectivamente, para E. colonum. La eficiencia de eliminación de bacterias coliformes fue de 99.9% para ambas especies. Los resultados indicaron que hubo una diferencia significativa (P < 0.05) en la eliminación de los principales contaminantes en el humedal plantado con C. ligularis, indicando una mayor capacidad de esta especie para el tratamiento del agua residual doméstica. | Abstract: This study evaluated the removal efficiency of organic matter (COD), nitrogen (NH4 -, NO3 ~) orthophosphate and total and fecal coliforms in four horizontal subsurface flow pilot scale constructed wetlands using two species of local plants. Two systems were planted with Cyperus ligularis and two Echinochloa colonum. The experiment consisted of sedimentation tank of 760 L (primary treatment) from where water was poured, through PVC pipe to constructed wetlands system. Each wetland was filled with gravel of a diameter of 8 mm and porosity of 0.4. Once a day during four months, wetlands added a flow rate of 42 L.day-1 to maintain a hydraulic residence time of three days. Wastewater samples (influent and effluent) were collected three times by week for COD and nutrients concentrations. Once a week the fecal and total coliforms were analyzed. Removal efficiency of COD, ammonium, nitrate and orthophosphate were of 93%, 65%, 71% and 32% respectively for C. ligularis and of 85%, 54%, 67% and 57% respectively for E. colonum. Removal efficiency of total and fecal coliforms was on 99.9% for both species. The results indicated no significant difference (P < 0.05) in the removal of principals contaminants in the wetland planted C. ligularis indicating higher ability of this species for the treatment of domestic wastewater