Pollutants Removal in Sewage Wastewater Efficiency and Kinetic of Ammonia Nitrogen Removal through Subsurface Vertical Flow Constructed Wetlands (SSVFCW)

Aims: The removal of some pollutants such as ammonia nitrogen, Total Kjeldahl Nitrogen (TKN), chemical oxygen demand (COD), biological oxygen demand (BOD5), phosphate and some solids (total (TS), fixed (TFS) and volatile (TVS)) from sewage wastewater was investigated in vertical subsurface flow constructed wetlands (SSVFCW).

Study Design: The bed of the constructed wetland is composed of gravel and Canna indica is used as vegetation.

Place and Duration of Study: The study was conducted at the Federal University of Santa Maria, southern Brazil, under subtropical climate from June to September 2019.

Methodology: Three kinds of samples of water collected (Raw, septic tank and outlet from the wetland) one time per week were analyzed according to American standards. Anions were analyzed by gas chromatography using 930 compact IC Flex Metrohm. Statistical analysis performed using ANOVA and U test of Mann-Whitneyto investigate the statistical difference were performed by STATISTICA and Origin software.

Results: A total of 10 samples of each kind of water were collected and analyzed. In the conditions of this study, the removal percentage is 89.88, 88.00, 84.93, 84.62, 84.31, 72.94, 41.71, 15.63 respectively for COD, TKN, NH4+-N, TVS, BOD5, TS, TFS and PO43--P. Environment temperature, hydraulic retention time have an effect on the performance of the wetlands system. The effect of the contact time shows that adsorption process is a partway of ammonia nitrogen removal in the wetland. Among the three models of kinetic studied to describe the removal of ammonia nitrogen, Stover-Kincannon and second order models showed a better fit than the first order model.

Conclusion: The nitrification and adsorption are the principal process of ammonia removal in the wetland. The plant has been found to be very efficient on the removal of ammonia nitrogen, TKN, COD, BOD5 while phosphate removal has been found too weak.