Cost–Benefit Evaluation of Decentralized Greywater Reuse Systems in Rural Public Schools in Chile

Abstract

Water scarcity is one of the most important climatic threats in recent times. In Chile, the north and north-central areas, with predominantly arid or semi-arid climates, have been strongly affected by the low availability of water, as well as by overexploitation of water resources derived from the negative effect caused by some sectors of the economy such as agriculture and mining. Only 53% of households in rural areas in Chile have access to drinking water from a public network. To date, some pilot greywater treatment systems have been implemented in rural public schools. This paper presents an economic analysis of pilot systems for greywater treatment from three case studies. The results showed that the implementation of these systems would not be economically feasible, since the initial investment costs can exceed USD 5200, which is not offset by the water savings. However, other benefits, such as thermal regulation, better life quality, and the feeling of well-being and satisfaction of students and teachers should be considered to be paramount for the evaluation of treatment systems. In addition, current levels of treated greywater could allow irrigation of 6.24, 5.68, and 3.56 m2/person in the Alejandro Chelén, El Guindo, and Pedro de Valdivia schools, respectively. These results contribute to a better understanding of the social role that should be applied to the evaluation of ecological systems that save water and improve the well-being of the population.

Light or Dark Greywater for Water Reuse? Economic Assessment of On-Site Greywater Treatment Systems in Rural Areas

“…The annual discount rate (r) used for the analysis was 8.16% with an evaluation period of 20 years. The discount rate was determined following the same procedure described by Rodríguez et al [14]. For this, financial indices and capital asset pricing model (CAPM) from waste and environmental services industry [28] were used.…”

“…(a) Capital costs Capital costs (C c ) include the costs associated with the purchase of the installation of filtration systems and/or biological treatment modules (if applicable), pumps, pipes, fittings and storage tanks. Following the analysis developed by Rodríguez et al [14], Equation (1) was used to determine the associated capital costs.…”

“…Following the procedure of Rodriguez et al [14], the environmental cost (C n ) included in the economic analysis corresponds to the noise pollution caused by electric pumps during the operation of the greywater reuse systems. Since the pumps are used close to the source of the greywater, their location in a place further from the school facilities is not feasible since it would require a greater investment in other items, such as plumbing.…”

“…For example, rural communities are more sensitive to water scarcity than urban areas due to the inherent complexities of their location and the difficult access to technological treatment systems. Rodríguez et al [14], showed that the implementation of pilot systems for greywater treatment in rural public schools in the Coquimbo Region are not economically feasible in a 10-year projection. This is mainly because capital costs and operating costs are not amortized by water savings in the long term.…”

Treatment and Effective Utilization of Greywater: A Preliminary Case Study

“…However, quantitative microbial risk assessment can be included to check the microbial risk involved in the non-potable reuse of greywater [27]. Furthermore, economic analysis can be planned in the future [28]. For possible water reuse in the agricultural sector, the retention of nutrients (i.e., total nitrogen and orthophosphate) must also be investigated [29].…”