CONSTRUCTED WETLANDS IMPLANTED WITH IRIS VERSICOLOR, JUNCUS SP. AND PHRAGMITES AUSTRALIS AS A POTENTIAL TREATMENT FOR GREENHOUSE EFFLUENTS

Greenhouse effluents are usually highly charged with nutrients, including nitrate and phosphate, which often may cause serious environmental problems when rejected without any treatment. In addition, the wastewater is often contaminated with pathogens, such as Pythium sp., often found in hydroponic systems. New regulations, instored within the next few years in Canada, will undeniably change effluent management practices for greenhouse growers. The use of constructed wetlands to treat these highly charged effluents may become a possible option to reduce the impact on the environment. A greenhouse experiment was performed in order to test the effect of three plants species (Iris versicolor, Juncus sp. and Phragmites australis) cultivated in wetlands to reduce the nutrient charge and the amount of pathogen propagules in greenhouse effluents. Small scale wetlands (0.15 m2) were constructed using coarse sand and implanted with either one of the 3 plants tested or left as an unplanted control. Wetlands received a volume of reconstructed greenhouse effluents in order to maintain a retention time of 7 days. Samples of the wetlands effluents were taken on a regular basis to evaluate the EC, pH and the N and P content. Microbial activity within the wetlands was also evaluated on a weekly basis. Total and nitrifying microorganisms were assessed. Results are discussed in terms of efficiency of the solution treatment through the constructed wetlands for the nutrient aspect. The effect of the different plant species on the microbial activity and its consequence on the efficiency of the wetland is also discussed. This work resulted in a better understanding of the processes involved in the use of constructed wetlands for the treatment of greenhouse effluents.