Environmental analysis of servicing centralised and decentralised wastewater treatment for population living in neighbourhoods

Abstract

The planning and construction of large-scale wastewater infrastructure, such as sewerage networks and wastewater treatment plants, is undertaken by the public sector or by publicly regulated monopolies. Only on smaller scales can infrastructure be managed by private companies or through local collective initiatives. Within this framework of water cycle management, there is an increasing movement of the population towards cities where economic activity is concentrated. This scenario is particularly pronounced in certain regions of the world and makes it necessary to rethink whether decentralised treatment offers a way of ensuring the servicing of wastewater treatment in new urban developments, alleviating pressure on facilities that are at the limit of their capacity.In this study four systems were evaluated: two centralised and two decentralised configurations, from an environmental and economic perspective, posing as working hypothesis how different wastewater treatment schemes influence the carbon footprint of the population living in a neighbourhood. The analysis of the results identifies that the decentralised systems present a reduction in the carbon footprint of residents of around 20–23 % depending on the technology considered. In addition, reclaimed water can meet the water quality requirements for irrigation of the green areas in the neighbourhood. Although decentralised systems have higher construction costs, they can be amortised due to lower energy consumption, so the payback time is estimated to be 8–9 years, lower than that of centralised systems. Considering the problems associated with changing and replacing existing networks, decentralised wastewater treatment systems is especially recommended for new dwelling developments, based on its environmental and economic indicators.