Application of a Multi-Criteria Decision Support Tool in Assessing the Feasibility of Implementing Treated Wastewater Reuse

Introduction

Freshwater scarcity, which is being experienced globally, needs conservative measures to maximize usage. It is a well established fact that water demand already exceeds supply in many parts of the world, and many more areas are expected to experience this imbalance in the near future. In order to meet an ever increasing demand for freshwater, past efforts have centred on the development of additional water resources schemes i.e. water supply interventions such as the exploitation of distant surface water and deeper groundwater sources, construction of new dams and desalination (Friedler & Hadari, 2006). However, implementation of these measures usually requires significant capital investment (planning, construction, operation, maintenance, and replacement) and is frequently accompanied by negative long term environmental effects such as the depletion of renewable water resources, deterioration of water quality, seawater intrusion, and alteration of ecosystem dynamics. Efforts to augment existing water supply have gone a long way to mitigate the negative effects of freshwater scarcity. However, other feasible and more environmentally attractive initiatives have been developed to complement water supply interventions. The separation of potable and non-potable water for various uses via dual reticulation systems has increasingly been investigated in many parts of the world as a means to meet the growing demand for non-potable water requirements that have traditionally used potable water (Hurlimann and Mckay, 2007).

Treated municipal wastewater represents a significant potential source of reclaimed water for some beneficial reuses. As developing country populations continue to grow from rural to urban areas, the number of centralized wastewater collection and treatment systems will also increase, creating significant opportunities to implement wastewater reuse systems to augment water supplies and, in many cases, improve the quality of surface waters (USEPA, 2004). Chang and Ma (2012) carried out a comparative analysis on the influencing factors on fresh water and reclaimed wastewater consumption in Beijing. The result shows that main factors affecting the promotion of wastewater reclamation in Beijing include water price, reclaimed wastewater quality, acceptability and local administrative orders.

Agrafioti, E and Diamadopoulos (2012) presented a strategic plan on the feasibility of recycling treated municipal wastewater for agricultural irrigation on the Greek island of Crete. In order to screen out and evaluate technologies appropriate for reclamation treatment to ensure the safe reuse of reclaimed water, Wei et al. (2012) developed a toxicity based assessment of treatment technologies while Paulo et al. (2012) Presented a natural systems of treating segregated domestic wastewater stream for reuse. Santos et al. (2012) also developed a simple, low-cost and easy maintenance experimental system for greywater reuse that provides high reduction of SS, COD and BOD.

Mojid et al. (2012) reported that the wheat cultivation irrigated with wastewater in Bangladesh promotes plant leaf growth but its effectiveness in improving the leaf area index (LAI) decreased with its elevated quantity in irrigation. The levels of faecal contamination of vegetable crop irrigated with tertiary-treated municipal wastewater were studied by Cirelli et al. (2012). The result shows that the microbiological quality of the products (i.e., eggplant and tomato) was generally maintained.

Treatment technologies for wastewater reuse are already well established with varied degrees of success in many countries such as Singapore, Israel, Jordan, Namibia, United States of America (USA), Australia, Germany and many European countries (Po et al., 2004). In South Africa, research on and practice of wastewater reuse for diverse non-potable uses has grown in the last 8 years (Carden et al., 2007). However, the practice of wastewater reuse system in South Africa is still in its infancy and as such, there is a paucity of reliable information relating to the costs and benefits, public opinion and decision support tools for assessing the feasibility of implementing treated wastewater reuse systems in different South African communities. This research is therefore focused on developing a decision support tool (named Waswarplamo: Wastewater Reuse Planning Model) for assessing the feasibility of implementing wastewater reuse.