Feasibility studies of a constructed wetland to treat contaminated water

Abstract

Among the vast number of methods that can be applied for the treatment of contaminated water, mine water was identified one of the best methods of treating of abandoned as the subsurface flow constructed wetlands through pytoextraction. Therefore further research was carried out to the applicability of constructed wetland to treat polluted water at abandoned quarry in Ragama (Prison Quarry). The main objective of the study was to measure the removal efficiencies of BOD, COD, NH3, NO3", PO43" using Thypha Latifolia (Cattail). The hydraulic retention time was 8 days. The concentration of Nitrate, Orthophosphate and Ammonia was monitored twice a week and BOD and COD were monitored once a week in order to determine their removal rates. While monitoring the removal efficiencies, the mechanisms of N, P and COD removals were identified. The mechanisms are based on the principle of mass conservation. The main nitrogen removal mechanisms identified were plant uptake and denitrification. It is assumed that ammonia and nitrate removal from wetlands by macropytes depended on the biomass of the roots. Average Nitrate and Ammonia removal from the planted cell was 42.9% and 27.8%, respectively, whereas the removal efficiency of Ortho Phosphate was 17.5% in the planted tank. Typha latifolia was identified as a suitable wetland plant which can remove nitrogen compounds in contaminated water.