Decentralized greywater treatment for reuse: a cost – benefit study for knowledge-based urban development (KBUD) Parks

Abstract

Decentralized treatment systems are an alternative to the traditional centralized plants, which treat domestic effluent in big cities. Decentralization is important in areas that are far from the city center, and they can facilitate the reuse in the same building, transforming the place in a more sustainable region. These systems can be well applied in Knowledge-based urban development (KBUD) Parks, mainly the fourth-generation ones which also consider the environment as a keystone of development.  Thus, our aim was to verify the decentralized greywater treatment system feasibility to produce non-potable water to be reused in an office at the International Hub for Sustainable Development (HIDS), a KBUD of fourth generation. In a bibliographic review Wetland was considered the best option and the cost-benefit analysis was carried out. Demand and production estimation of greywater (includes water from sources such as sinks, showers, bathtubs, washing machines, and kitchen appliances, except for water from toilets) was based on field collected data at University of Campinas (UNICAMP) departments. As a Result, the system is designed to treat 135 m³ of water per month, leading to saving 22.65 m³ per month of water. Monthly, economical saving will be US$ 415. Based on cost estimates, the savings generated would recover the system's initial investment in less than three months of use, having an internal rate of return (IRR) of 34.9% in 1 year.  Thus, the cost-benefit is substantial, given that the return on investment is quick. Therefore, system is feasible and interesting from a sustainable perspective.