Life cycle assessment (LCA) of three wastewater denitrification scenarios (none, woodchip, activated sludge) for the treatment of RAS effluent

Description

Abstract
Nitrogen emissions from aquaculture wastewater represent a key environmental challenge in farming
practices, potentially contributing to eutrophication and ecosystem degradation. While various
treatment technologies with different removal efficiencies are employed to mitigate these emissions
through denitrification in RAS, few studies have comprehensively evaluated the environmental
impacts associated with their construction, operation, and removal efficiency.
Current end-of-pipe treatment approaches span a spectrum from low-input woodchip biofiltration to
chemically balanced activated sludge systems, all designed to reduce effluent nitrogen emissions. The
selection of appropriate techniques depends on ammonium nitrate concentration (i.e., recirculation
intensity), production scale, available space, and discharge permits. Yet, a thorough understanding of
their environmental impacts remains critical as these methods are increasingly implemented. Previous
research has identified potential N₂O formation during incomplete denitrification in woodchip
biofilters, highlighting the need to evaluate environmental impacts using LCA. At the same time, LCA
studies of activated sludge systems in aquaculture remain absent from the literature.
This study evaluates the environmental impacts of three different wastewater denitrification
scenarios: no biofiltration, woodchip biofiltration, and activated sludge, using a functional unit of 1 m³
of treated aquaculture effluent, scoped for a 600-ton farm operation, and provides a comparative
analysis of these treatments. These data enable informed decision-making regarding trade-offs
between end-of-pipe treatment methods, particularly through evaluating greenhouse gas emissions
per cubic meter of treated wastewater to establish environmental benefit thresholds. This research
enhances transparency regarding aquaculture wastewater treatment impacts and identifies potential
pathways for reducing overall environmental impacts.

Period	9 Oct 2025
Event title	7th NordicRAS Workshop on Recirculating Aquaculture Systems
Event type	Workshop
Location	Aalborg, DenmarkShow on map