Effects of Different Substrates and Hydraulic Retention Time (HRT) on the Removal of Total Nitrogen and Organic Matter in a Sub-Surface Horizontal Flow Constructed Wetland

By N. Shuib and K. Baskaran.

Published by The Sustainability Collection

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Article: Print $US10.00
Article: Electronic $US5.00

The aim of this study was to investigate the treatment efficiency of constructed wetlands (CWs) planted with phragmites australis and scirpus maritimus. The wetland systems operated under horizontal subsurface flow using three different substrates at varied hydraulic retention times. Each wetland type consisted either of 0.36 m² alum sludge (AS), gravel (G), or zeolite (Z) as substrate. All systems were subjected to two hydraulic retention times (HRT) of 4 and 3 days respectively. Each wetland bed received 0.012 m³/d to 0.03 m³/d of synthetic wastewater corresponding to a hydraulic loading rate of 0.035 to 0.067 m/d and a COD loading rate of 0.026 kg COD (m2/d)╶ ¹ to 0.035 kg COD (m2/d). The constructed wetland using zeolite as the substrate achieved significantly higher COD and TN removal with the 4 day HRT compared to gravel and alum sludge substrates. The average COD removal efficiency whilst using zeolite was approximately 88%, followed by 78% for gravel and 67% for alum sludge. Average removal efficiency for total nitrogen was 96% in zeolite, 43% for gravel and 20% for alum sludge. Changing the HRT to 3 days, showed a slight decreased in the COD removal efficiency to 85 % using zeolite. However, the gravel and alum sludge substrates showed an increase in COD removal reported as 93% and 91% respectively. Similar removal patterns were found for nitrogen at the three days retention time. Nitrogen removal by zeolite and gravel were found to be low and approximately 3% for zeolite and 29% for gravel. Total nitrogen removal efficiency using alum sludge increased slightly to 4%. It was observed that the substrate type and retention times had a major effect on the removal efficiency of organic matter and total nitrogen in CWs.

Keywords: Zeolite, Gravel, Alum Sludge, Constructed Wetland, Hydraulic Retention Time, Horizontal Subsurface Flow

The International Journal of Environmental, Cultural, Economic and Social Sustainability, Volume 7, Issue 5, pp.227-242. Article: Print (Spiral Bound). Article: Electronic (PDF File; 978.938KB).

N. Shuib

PhD. Student, School of Engineering, Deakin University, Waurn Ponds, Victoria, Australia

I was born on 20 of June 1968 in a small village in Malaysia. I finished my first degree in Civil Engineering at Universiti Teknologi Malaysia in 1999. In 2004, I finished my Master’s Degree also in Civil engineering at Universiti Sains Malaysia. For my Master’s Degree, I did research on the potential of alum sludge as a constructed material. I worked as a lecturer at Universiti Teknologi Mara from 2004 to 2008. Currently, I am doing my PhD at Deakin University, Australia. My area interest is in constructed wetland systems. I am doing research on how to treat agricultural wastewater by using hybrid constructed wetland systems. So far I am in year two at Deakin university.

Prof K. Baskaran

Associate Dean (International), PhD Supervisor, School of Engineering, Deakin University, Victoria, Australia

Associate Professor K. Baskaran has more than 27 years of professional experience in Civil Engineering. The first four years of his professional career, he worked as a Civil Engineer with various international civil engineering and building contractors in Sri Lanka. The remaining 23 years, he has worked in leading tertiary institutions in Australia and Thailand conducting extensive research in various aspects of water reclamation and reuse, treatment processes for municipal and industrial wastewater. His research interests are water and wastewater treatment technology, environmental biotechnology and bioremediation and water reclamation and reuse. He is currently Interim Head of School, School of Engineering and has previously held the positions of Chair of the Access, Equity and Equal Opportunity Committee; Director of Postgraduate Programs; Deputy Dean, of the Faculty of Science and Technology; and Acting Associate Dean (International) of the Faculty of Science and Technology.

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