Global nitrogen and phosphate in urban wastewater for the period 1970 to 2050

TLDR

The study estimates global nitrogen and phosphorus emissions from sewage for 1970–2050 across four Millennium Ecosystem Assessment scenarios. The authors model emissions using country‑specific projections of population, economic growth, urbanization, sewage system development, and wastewater treatment installations. Projections indicate global sewage N and P emissions will roughly double by 2050, driven by developing countries, with some regions declining, and even optimistic treatment scenarios fail to curb overall flows.

Abstract

This paper presents estimates for global N and P emissions from sewage for the period 1970–2050 for the four Millennium Ecosystem Assessment scenarios. Using country‐specific projections for population and economic growth, urbanization, development of sewage systems, and wastewater treatment installations, a rapid increase in global sewage emissions is predicted, from 6.4 Tg of N and 1.3 Tg of P per year in 2000 to 12.0–15.5 Tg of N and 2.4–3.1 Tg of P per year in 2050. While North America (strong increase), Oceania (moderate increase), Europe (decrease), and North Asia (decrease) show contrasting developments, in the developing countries, sewage N and P discharge will likely increase by a factor of 2.5 to 3.5 between 2000 and 2050. This is a combined effect of increasing population, urbanization, and development of sewage systems. Even in optimistic scenarios for the development of wastewater treatment systems, global N and P flows are not likely to decline.