EFFECTS OF PLANT HARVESTING ON NUTRIENTS REMOVAL IN CONSTRUCTED WETLANDS.

Insufficient access to clean water and sanitation has become one of the most universal problems affecting human health in developing countries, water resources are facing high pollution rate due to improper management of wastewater. Ecological technologies such as constructed wetlands are promising innovative solutions for this universal problem. Constructed wetlands are engineered wastewater treatment systems that include treatment segments such as physical, chemical, and biological processes like in natural wetlands. Plant harvesting practice is one management strategy that can prevent these systems from clogging and loss of surface area, the effects of this management strategy need to be assessed related to the performance of wetlands. The aim of this thesis was to investigate the effects of plants harvesting on nutrients removal (N, P, and COD) in constructed wetlands. This is a literature review and experimental based thesis. The literature review involved reviewing 5 studies about effect of harvesting plants in constructed wetlands. The experiment part involved data analysis from 6 experimental wetlands, with 3 wetlands that have been harvested in 2015 and 2016, another 3 wetlands that have never been harvested. Results from literature review indicated that plant harvesting in wetland has a significant effect in nutrients removal. Experiment results indicated that there was significant difference between these wetlands in TN and NO3-N removed when the entire operation period was considered (P=0.005). But when each season was considered separately statistical differences were only observed during first summer after harvesting for TN removal. For NO3-N, differences between wetlands were observed in first summer and winter only. For summer, harvested wetland performed better than non-harvested wetland, but in winter non-harvested wetland performed better than harvested in terms of NO3-N removal. For winter, the reason to this could be that, some of plants parts decay and provided denitrification bacteria with a carbon source which accelerates denitrification process. According to this study, plants harvesting in wetland generally has a positive effect on nutrient removal such as TN, TP, COD, and BOD. Therefore, this practice could be recommended as the best wetland plants management to improve and maintain nutrient removal in constructed wetlands