Is it More Sustainable to Treat Sewage or Dump it in the Ocean?

Abstract:

It is commonly argued that sustainable sewage management requires a shift from the conventional linear, end-of-pipe approach to more adaptive, iterative sanitation solutions, but that the inertia in the existing system hinders such a shift. This case-study analyzes reasons as to why jurisdictions may chose to discharge untreated sewage to the ocean rather than to follow the resource-recovery trend argued for in the academic literature. Our study is based on an analysis of the reasoning behind “Plan Director 2006-2020” in Buenos Aires, Argentina, which includes extending the central sewer system to over five million people living in underserviced areas and conveying the sewage to a central discharge station. Our study suggests that the decision to discharge untreated sewage into the ocean via Rio de la Plata rests on four firmly rooted perceptions:

1. Centralized sewer systems are better than distributed systems, irrespective of scale, 2. Sewage treatment generates sludge and sludge management incurs considerable risks and costs, not least in densely populated areas where access to land is limited, 3. The benefits of resource recovery are overrated and the costs are underestimated and last but not least, 4. The ocean has an enormous self-purifying capacity.

Each of these four perceptions is discussed in light of the literature, with a focus on the scientific knowledge that is used to frame risks and benefits related to the two policy options (discharging at sea vis-à-vis resource recovery) in particular inferred causal links, and how uncertainty is handled.