Wastewater Treatment Using Constructed Wetland With Water Lettuce (Pistia Stratiotes) Oladipupo. S. OLADEJO*, Olabamiji. M. OJO, Oluwaseun. I. AKINPELU, Oluwajuwonlo. A. ADEYEMO, Abimbola. M. ADEKUNLE Abstract- A laboratory-scale free water surface-flow constructed wetland was set up at the Department of Civil Engineering; Ladoke Akintola University of Technology (LAUTECH) Ogbomoso, Nigeria in May 2013 to demonstrate the performance of sand- based constructed wetland, using Water Lettuce. The experiment was carried out to demonstrate the enhanced removal efficiency for Water Lettuce with constructed wetland in treating kitchen wastewater, from a nearby Campus restaurant- Alata milk and honey. The nutrient removal and performance evaluation of the constructed wetland in treatment of kitchen wastewater against retention period of ten days was investigated. During the 10-day retention period, the sand- based constructed wetland set up with Water Lettuce had improved the wastewater quality significantly as it had reduced 75.66% of Turbidity, BOD5 by 83.43%, NO-3 by over 50%, 90% of SO-4 , 46.2% of Cl- and Conductivity by 46.2% and Dissolve Oxygen by 58%. The pH increased by 23%, while the initial offensive odour of the raw water was no more noticeable. The final effluent was found to be suitable for non-drinking purposes like crop irrigation and keeping aquatic animals. However, it was noted that a 7- day detention time was optimal for the treatment of domestic wastewater from kitchen. The treatment system was found to be economical, as the cost of construction only was involved and maintenance cost very minimal. It was environmentally friendly as it was free from offensive odour and insect invasion. The prototype scale is recommended for in-situ use, especially for wastewater from kitchen. Keywords- Constructed wetland, kitchen wastewater, Laboratory scale, Nutrient removal, Retention period, Water Lettuce I. INTRODUCTION ONSTRUCTED wetlands are engineered to duplicate the processes occurring in natural wetlands, where the main purpose of the structure is to remove the contaminant or pollutant from the wastewater [1]. The constructed wetland is an integrated system consisting of water, plants, microorganisms and the environment, in which can be manipulated to improve water quality. The constructed wetland is a new green technology, which has been recognized and accepted as a creative, cost-effective and environmental friendly system when compared to the expensive conventional treatment systems. Recently, the multiple values and functions of the constructed wetlands, has been widely used for treating a variety of wastewaters of many sectors.. Thus, an extensive research and practical application is being gained in order to operate the system effectively. Dr. Oladejo, Oladipupo. Seun. is a Senior Lecturer at Department of Civil Engineering, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso Nigeria. E-mail: osoladejo@lautech.edu.ng Olabamiji. M. Ojo, Oluwaseun. I. Akinpelu, Oluwajuwonlo. A. Adeyemo, Abimbola. M. Adekunle are research students at Department of Civil Engineering, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso Nigeria. In the last few decades , the constructed wetlands are widely applied for the purification of storm water, agricultural, domestic and also industrial wastewater treatment. The use of constructed wetland on industrial pollutants is increasingly utilized and these represent a promising alternative method to treat the various types of industrial wastewater using the new technology of constructed wetlandsIn recent years, increasing production and disposal of wastewater have caused an accelerated pollution of receiving water bodies. Hence, to reduce the harmful impact of the wastewater discharge, there is the need to remove the main nutrients such as nitrogen and phosphorus as well as the organic content of the wastewater prior to disposal. This can be effectively achieved by the conventional treatment technology, but the working expenses and energy requirements of such treatment systems are rather high and in many cases hinder by economic constraints which often leads to the desertion of such various treatment plants in the country (Nigeria) due to lack of funding and consequently maintenance on the part of the responsible agency. However, several investigations have shown that wetlands may act as efficient water purification systems and nutrient sinks [2]; [3,4]; [5]; [6]. Constructed wetlands are artificial wastewater treatment system consisting of shallow (usually less than 1 m deep) ponds or channels, which have been planted with aquatic plants, and rely upon natural microbial, biological, physical and chemical processes to treat wastewater [7]. These systems of wastewater treatment offer several potential advantages as compared to conventional treatment system, this include; simple construction (can be constructed with local materials), require less skill to operate and maintain, process stability under varying environmental conditions, Utilization of natural processes, and lower construction, operation and maintenance costs. There are two basic types of constructed wetland namely; free water surface flow constructed wetland in which the flow of water is above the sediment surface, and subsurface flow constructed wetland in which the flow of water is primarily below the sediment surface. These systems use wetland plants, soils and their associated microorganisms to remove contaminants from wastewater [8, 9]. The pollutant removal mechanisms in a constructed wetland plant comprise several physical, chemical, biological and biochemical processes and this include; sedimentation, filtration, aerobic and anaerobic microbial degradation, plant uptake, soil sorption, precipitation and so on [4]; [10]; [13] . Water lettuce is important in the treatment of waste water. The use of water plants in waste water treatment is economical, is a natural way of treating water. Water lettuce C International Journal of Chemical, Environmental & Biological Sciences (IJCEBS) Volume 3, Issue 2 (2015) ISSN 2320–4087 (Online) 119