Effects of Constructed Wetlands Plants on Phosphorus Removal from Domestic Wastewater in Gaborone, Botswana
Abstract
The United Nations, Sustainable Development Goal (SDG) Target 6.3. aims at “halving the proportion of untreated waste water and substantially increasing recycling and safe reuse globally” by 2030. To achieve this target, sustainable and context-specific wastewater treatment systems are urgently needed. Constructed wetlands (CW) is one of the wastewater treatment technological options available. CW have been widely accepted and acknowledged as simple, low cost, alternative and appropriate domestic wastewater treatment technology. CW were piloted by the Department of Water Affairs, Gaborone, Botswana to assess their treatment performance. Specifically, the study investigated the effects of CW plants on Phosphorus (P) removal from domestic wastewater. The first CW cell (CA) was a control which was filled with sand only, the second cell (CB) was planted with Typha Latifolia, the third (CC) with Cyperus Papyrus and the fourth (CD) with Phragmites Mauritianus. Each cell had a surface area of 100m2and received a wastewater discharge of 4m3/day. River sand with porosity of 0.44 and particle size diameter ranging from 2-7mm was used as plants growing media. Wastewater samples were analysed in accordance with Standard Methods for Examination of Water and Wastewater. The results showed that the P treatment performance efficiencies for CA, CB, CC, and CD were 93.6%, 97.4%, 98.1% and 98.4% respectively. Despite that there was CW plants contribution towards P removal from domestic wastewater, there was however no statistically significant performance difference (p>0.05) in P removal between the CW cells planted with different plant species. The mean effluent P concentrations from the different CW cells were; CA 0.62mg/l, CB 0.28mg/l, CC 0.19mg/l and CD 0.16mg/l. Thus, the mean P concentration from the effluent of C1 was above the Botswana Bureau of Standards Limits of 0.5mg/l. Hence the effluent was non-compliant with Botswana standards for the discharge of effluent into the environment.
Tanzania Journal of Engineering and Technology (Tanz. J. Engrg. Technol.) publications are written as a basis for academic discussions. Whereas effort is made by the Editorial Board to screen out inaccurate or misleading statements, data or opinions, Tanz. J. Engrg. Technol. wishes to make it clear that the contents of the articles are the sole responsibility of the authors. Accordingly, the Editorial Board and editors, publisher, College of Engineering and Technology and the University of Dar es Salaam accept no responsibility or liability whatsoever for the opinions, inaccurate or misleading data or statement and views expressed by the authors.
However, the College of Engineering and Technology, the publisher of the Journal, reserve all rights of the articles published in the Journal. Whereas the contents of the articles are available electronically without cost, no part of the publication may be transmitted in any form or reproduced electronically or mechanically, except for short extract in critical scholarly review, research or discourse with an acknowledgement.
