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Direct Discharges of Domestic Wastewater are a Major Source of Phosphorus and Nitrogen to the Mediterranean Sea
journal contribution
posted on 2016-07-13, 00:00 authored by Helen R. Powley, Hans H. Dürr, Ana T. Lima, Michael D. Krom, Philippe Van CappellenDirect discharges
of treated and untreated wastewater are important
sources of nutrients to coastal marine ecosystems and contribute to
their eutrophication. Here, we estimate the spatially distributed
annual inputs of phosphorus (P) and nitrogen (N) associated with direct
domestic wastewater discharges from coastal cities to the Mediterranean
Sea (MS). According to our best estimates, in 2003 these inputs amounted
to 0.9 × 109 mol P yr–1 and 15 ×
109 mol N yr–1, that is, values on the
same order of magnitude as riverine inputs of P and N to the MS. By
2050, in the absence of any mitigation, population growth plus higher
per capita protein intake and increased connectivity to the sewer
system are projected to increase P inputs to the MS via direct wastewater
discharges by 254, 163, and 32% for South, East, and North Mediterranean
countries, respectively. Complete conversion to tertiary wastewater
treatment would reduce the 2050 inputs to below their 2003 levels,
but at an estimated additional cost of over €2 billion yr–1. Management of coastal eutrophication may be best
achieved by targeting tertiary treatment upgrades to the most affected
near-shore areas, while simultaneously implementing legislation limiting
P in detergents and increasing wastewater reuse across the entire
basin.