Ecological Engineering 37 (2011) 1878–1888 Contents lists available at ScienceDirect Ecological Engineering jo u r n al hom ep age: www.elsevier.com/locate/ec oleng Optimization of waste stabilization pond design for developing nations using computational fluid dynamics David O. Olukanni 1 , Joel J. Ducoste ∗,2 Department of Civil Engineering, Covenant University, P.M.B. 1023, Ota, Ogun State, Nigeria a r t i c l e i n f o Article history: Received 31 October 2010 Received in revised form 14 April 2011 Accepted 6 June 2011 Available online 21 July 2011 Keywords: Wastewater Waste stabilization pond Disinfection CFD Optimization a b s t r a c t Waste stabilization ponds (WSPs) have been used extensively to provide wastewater treatment throughout the world. However, no rigorous assessment of WSPs that account for cost in addition to hydrodynamics and treatment efficiency has been performed. A study was conducted that utilized com- putational fluid dynamics (CFD) coupled with an optimization program to optimize the selection of the best WSP configuration based on cost and treatment efficiency. The results of monitoring the fecal coliform concentration at the reactor outlet showed that the conventional 70% pond-width baffle pond design is not consistently the best pond configuration as previously reported in the literature. The target effluent log reduction can be achieved by reducing the amount of construction material and tolerating some degree of fluid mixing within the pond. As expected, the multi-objective genetic algorithm optimization did produce a lower-cost WSP design compared to a SIMPLEX optimization algorithm, however, with only a marginal increase in the effluent microbial log reduction. Several other designs generated by the CFD/optimization model showed that both shorter and longer baffles, alternative depths, and reactor length to width ratios could improve the hydraulic efficiency of the ponds at a reduced overall construction cost. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Conventional wastewater treatment technologies used in most industrialized nations are currently not potential options in many developing countries to provide environmental and public health protection. Developing nations have difficulty in sustaining the required energy and chemical consumption needed to success- fully operate the technologies used in conventional wastewater treatment plants (Kivaisi, 2001). In addition, these technologies require considerable technical expertise, which is often not avail- able in developing nations to successfully operate these treatment plants. Consequently, developing nations are unable to incorporate these technologies as part of a wastewater treatment master plan. Development of proper wastewater treatment has been a crucial topic in Africa for the prevention of many types of transmittable diseases. In Nigeria, the high construction cost for a conventional wastewater treatment plant has been a major barrier for the imple- ∗ Corresponding author at: Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 208 Mann Hall, Campus Box 7908, Raleigh, NC 27696-7908, United States. Tel.: +1 919 515 8150; fax: +1 919 515 7908. E-mail addresses: oluisone@yahoo.com (D.O. Olukanni), jducoste@ncsu.edu (J.J. Ducoste). 1 Tel.: +234 08030726472. 2 Work done as a Visiting Research Scholar, North Carolina State University. mentation of these conventional technologies by local authorities as well as in many other countries in Africa (Agunwamba, 1994, 2001b; Olukanni and Aremu, 2008). Among the current processes used for wastewater treatment, WSPs has been consistently selected as the unit process choice for wastewater treatment in developing nations due to their low cost and efficient operation in tropical regions (Agunwamba, 2001a; Mara, 1997, 2004; Abbas et al., 2006; Kaya et al., 2007; Naddafi et al., 2009). Agunwamba et al. (2004), Hamzeh and Ponce (2007), and Mara (2004), Mara and Pearson (1998), describe WSPs as large shallow basins enclosed by natural embankments in which decom- position of organic matter in wastewater is processed naturally (biologically). WSP compared to other technologies are a relatively simple technology; but contain a complex ecological system, which consists of algae, virus, protozoa, rotifers, insects, crustaceans, and fungi. These microbial communities stabilize the organic waste and lower the effluent pathogen levels (Kehl et al., 2009). The WSP system typically consists of a series of continuous flow anaerobic, facultative, and maturation ponds (Mara, 2004; Babu et al., 2010). The anaerobic pond, which is the initial treatment reactor, is designed to eliminate suspended solids and some of the soluble organic matter. The residual organic matter is further removed through the activity of algae and heterotrophic bacteria in the facultative pond. The final stage of pathogens and nutrients removal takes place in the maturation pond. The prime mecha- 0925-8574/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2011.06.003