Ecological Engineering 71 (2014) 384–393 Contents lists available at ScienceDirect Ecological Engineering journal h om epa ge: www.elsevier.com/locate/ecoleng Performance of vertical flow constructed wetlands for faecal sludge drying bed leachate: Effect of hydraulic loading Ebenezer Soh Kengne a,∗ , Ives Magloire Kengne a , Wilfried Arsene Letah Nzouebet a , Amougou Akoa a , Hung Nguyeng Viet b,c , Linda Strande c a Department of Plant Biology, Faculty of Science, University Yaoundé I, PO Box 812, Yaoundé, Cameroon b Department of Environmental Health, Hanoi School of Public Health (HSPH), 138 Giang Vo, Hanoi, Vietnam c Eawag: Swiss Federal Institute of Aquatic Science and Technology, Sandec Department of Water and Sanitation in Developing Countries, Überlandstrasse 133, PO Box 611, 8600 Dübendorf, Switzerland a r t i c l e i n f o Article history: Received 25 July 2013 Received in revised form 11 May 2014 Accepted 11 July 2014 Keywords: Developing countries Faecal sludge Loading rates Resource recovery VFCW Leachate a b s t r a c t The discharge of raw faecal sludge directly into the environment is a common practice that threatens environmental and public health in low-income countries. Planted drying beds are a promising and low- cost option for treatment of faecal sludge and the production of fodder plants, but current research shows the leachate quality does not meet guidelines for discharge. This paper investigates the use of Vertical Flow Constructed Wetlands (VFCWs) planted with Echinochloa pyramidalis for polishing of leachate from faecal sludge drying beds. At a pilot-scale, three hydraulic loads (50, 100 and 150 mm/d) were applied with single loadings once a week on VFCWs (corresponding to 31 ± 9, 63 ± 19, 94 ± 28 g/m 2 /month of BOD 5 ; 21 ± 6, 42 ± 12, 63 ± 19 TKN; and 2 ± 1; 4 ± 4; 6 ± 6 PO 4 –P, respectively, for hydraulic loading rates of 50, 100 and 150 mm/d). Infiltration flow rate, plant growth, rhizospheric bacteria, and leachate characteristics were monitored. VFCWs were effective in reducing on average more than 80% of the pollutants monitored (COD, BOD 5 , NH 4 –N, TKN, PO 4 –P, and faecal bioindicators), which met all National Cameroon and WHO guidelines for safe reuse in agriculture, except for total nitrogen and faecal indicators. Results confirmed a correlation between plant density and rhizospheric bacteria growth with increasing hydraulic load. These are important results, demonstrating that VFCWs can operate efficiently at multiple hydraulic loadings, and are hence adaptable to different sized treatment schemes. It also illustrates that if plant production for fodder is a goal, increased loading rates are preferable as they achieve overall treatment goals and result in greater plant production. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Faecal sludge (FS) is produced from onsite sanitation tech- nologies (e.g. pit latrines, septic tanks), and is the result of the collection, storage or treatment of combinations of excreta and blackwater, with or without greywater from these technologies (Montangero and Strauss, 2002; Tilley et al., 2008). Adequate treatment of FS prior to end use or discharge to the environ- ment are imperative to provide human and environmental health ∗ Corresponding author. Present address: Department of Plant Biology, Higher Teachers Training College, University of Bamenda. PO Box 39 Bamenda, Cameroon. Tel.: +237 77 15 74 22; fax: +237 2222 1320. E-mail addresses: sohkengnee@yahoo.fr (E.S. Kengne), ives kengne@yahoo.fr (I.M. Kengne), lewila2007@yahoo.fr (W.A.L. Nzouebet), hung.nguyen@unibas.ch (H.N. Viet), linda.strande@eawag.ch (L. Strande). protection (Feachem et al., 1983; Koné and Strauss, 2004; Mara and Cairncross, 1989). There have been many attempts at imple- menting conventional wastewater treatment technologies (e.g. rotating biological contactors, activated sludge), but they have not been well adapted to the African context for a number of reasons, among which the high cost of installation, the avail- ability of a reliable energy supply, and local skills and human resources are prominent. Hence, more “natural” or passive sys- tems also termed low-cost technologies (Strauss et al., 1997) such as planted drying beds for sludge and wastewater (i.e. vertical flow constructed wetlands (VFCWs)) provide a promising alterna- tive. Their use for treatment of wastewaters, including municipal, surface, storm, industrial, and agricultural has been well estab- lished (Cofie et al., 2006; Cooper, 2005; Kadlec and Wallace, 2009; Liénard et al., 2004; Stefanakis and Tsihrintzis, 2012; Vymazal, 2007). Preliminary research (Kengne et al., 2011; Stefanakis and http://dx.doi.org/10.1016/j.ecoleng.2014.07.041 0925-8574/© 2014 Elsevier B.V. All rights reserved.