Environmental performance of wastewater reuse systems: impact of system boundaries and external conditions

Abstract

Wastewater reclamation will be a significant part of future water management and the environmental assessment of various treatment systems to reuse wastewater has become an important research field. The secondary treatment process and sludge handling on-site are, especially, electricity demanding processes due to aeration, pumping, mixing, dewatering, etc. used for operation and are being identified as the main contributor for many environmental impacts. This study discusses how the environmental performance of reuse treatment systems may be influenced by surrounding conditions. This article illustrates and discusses the importance of factors commonly treated as externalities and as such not being included in optimization strategies of reuse systems, but that are necessary to environmentally assess wastewater reclamation systems. This is illustrated by two up-stream and downstream processes; electricity supply and the use of sludge as fertilizer commonly practiced in regions considered for wastewater reclamation. The study shows that external conditions can have a larger impact on the overall environmental performance of reuse treatment systems than internal optimizations could compensate for. These results imply that a more holistic environmental assessment of reuse schemes could provide less environmental impacts as externalities could be included in measures to reduce the overall impacts.