Water Qual. Res. J. Canada, 2006 • Volume 41, No. 4, 410–417 Copyright © 2006, CAWQ 410 Performance of Laboratory-Scale Wetlands Planted with Tropical Ornamental Plants to Treat Domestic Wastewater Florentina Zurita, 1 Jose de Anda 2 * and Marco A. Belmont 3 1 Centro Universitario de la Ciénega, Universidad de Guadalajara, Av. Universidad 1115, Ocotlán, Jalisco, Mexico 2 Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A. C. Normalistas 800, 44270 Guadalajara, Jalisco, Mexico 3 Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, Louisiana, United States 70803 This work proposes an innovative wastewater treatment system that consists of a constructed subsurface flow wetland planted with ornamental flowers of high market value. In addition to the benefit of the water treatment, this cash crop pro- vides a profitable business by producing commercial flowers that can meet all biological and safety requirements in order to be commercialized. This characteristic of the treatment system makes it very valuable for application in developing countries. Five different species of ornamental plants were studied from September 2004 to January 2005. Several water quality para- meters were evaluated at the inlet and outlet of a laboratory-scale system. COD was reduced by more than 75% in all cases; BOD and nitrogen were removed by more than 70%, except in one cell; phosphorus was reduced by more than 66% and the dissolved oxygen increased from 0.175 to 5.8 mg L –1 . Total and fecal coliforms were removed in the wetland by more than 99.3%. According to these results, it is feasible to couple ornamental flower production with wastewater treatment. A pilot-scale study is recommended in order to validate the preliminary results under more realistic conditions. Key words: ornamental plants, constructed wetlands, subsurface wetlands, wastewater treatment, municipal wastewater, Lake Chapala * Corresponding author; janda@ciatej.net.mx Introduction The world is experiencing significant growth in human population, and fresh water is becoming a scarce resource. Lakes represent a major source of such fresh water, but are coming under increasing pressure through exploitation by agriculture, industry, drinking water and hydroelectricity generation. This is particularly the case in tropical developing countries. Many authors (Ryding and Rast 1989; Welch 1992; Maniak 1997) suggest that the most effective long-term measure for the control of eutrophication in a water body is the reduction of the input of external nutrients. One way to reduce the nutrients coming from point sources, is to remove them by biological treatment. Unfortunately, the cost of installation and operation of a wastewater treatment plant (WWTP) does not permit the municipal governments of developing countries to invest in such technologies (Kivaisi 2001; Belmont et al. 2004). Lake Chapala is the most important natural lake in Mexico and the main fresh water supply for Guadalajara City. The primary tributary to Lake Chapala is the Lerma River. Large quantities of domestic, agricultural and industrial sewage from the entire Lerma-Chapala basin still flow untreated into the watershed and eventually into the lake, resulting in excessive inputs of phosphorus (P) and nitrogen (N), both known to cause eutrophication (de Anda and Shear 2001). Human water demand from Lake Chapala surpasses the surface supply and groundwater recharge rate (de Anda et al. 1998). This has resulted in a hydrologic imbalance in the lake basin. In addition, high nutrient concentrations in the lake have led to degraded water quality, resulting in growth of floating aquatic vege- tation and blue-green algae. The adverse environmental impacts are clearly reflected in the considerable reduction of native and migratory fauna and in the severe reduction of the water storage volume. A solution to reduction of the severe environmental impacts and eutrophication of Lake Chapala is to develop a cost-effective treatment technology, namely a constructed subsurface flow wetland (SSFW), which could permit a significant reduction of nutrient contami- nation along the Lerma River and around the lake shore. The proposed treatment system is less expensive than the existing commercial systems, and is easier to build and operate (Linsley et al. 1992; Seoánez-Calvo 1999; Kivaisi 2001; Belmont and Metcalfe 2003; Dallas 2004). SSFW are useful not only for the control of pollution with nutri- ents but also to remove persistent organic pollutants from wastewater and runoff (Belmont et al. 2006). This sewage treatment system allows the develop- ment of a profitable business by producing commercial ornamental flowers that meet all biological safety requirements in order to be delivered to the market.