2. Methodology2.1. Sources of effluent, sample collection and analysisTwo rubber factories/sites (Factories A and B) were chosen forthis study. The factories were situated along the Ikpoba River whichruns across the Eastern end of Benin City, South-South, Nigeria. Theentire experiment (baseline wastewater quality monitoring, treat-ment in the macrophyte pond, and utilization of resulting effluentfor growing maize plants) began in November 2003 and endedin March, 2006. The efficiency of water lettuce based macrophytepond to treat wastewater from rubber processing industries wasmonitored for three months for each inoculation by varying theretention time. In order to obtain reliable physicochemical andbiological parameters of wastewater from the factories prior to totreatment in the macrophyte pond, baseline wastewater qualitymonitoring was performed for one year, starting from November01, 2003 to November 01, 2004.2.2. Establishment of water lettuce based pond systemsA batch system of storage ponds was established to comparewith a real field macrophyte pond. The ponds were established inplastic pots in the Screen House at the Department of Crop Sci-ence, University of Benin, Nigeria. Wastewater quality monitoringwas carried out on these pots in order to determine the effectivesof a water lettuce based pond for treatment of rubber processingwastewater