Direct Discharges of Domestic Wastewater are a Major Source of Phosphorus and Nitrogen to the Mediterranean Sea

Abstract

Direct 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 x 10 9 mol P yr −1 and 15 x 10 9 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

Nitrogen dynamics in a highly urbanized coastal area of western Japan: impact of sewage-derived loads

“…Although this has been improved via the development of sewage treatment systems, the removal of nitrogen requires advanced processing, and relatively large proportions of nitrogen are still discharged in treated sewage effluent to coastal areas due to the absence of this treatment. Powley et al (2016) estimated that nitrogen inputs from the direct discharge of treated and untreated wastewater from coastal cities to the Mediterranean Sea are of the same order of magnitude as riverine inputs. The effects of excess nitrogen supply from wastewater treatment effluent influence ecosystem structure, as well as nitrogen cycling in receiving waters (Waiser et al 2011;Drury et al 2013).…”

Reproduction of Spatio-Temporal Patterns of Major Mediterranean Phytoplankton Groups from Remote Sensing OC-CCI Data

“…It exhibits an oligotrophic regime (Krom et al, 1991), notwithstanding relatively external high inputs of essential nutrients (Ludwig et al, 2009;Huertas et al, 2012;Powley et al, 2016). Nevertheless, local physical structures generate convergences zones, which are reflected in the distinct biogeochemical properties of the two Mediterranean sub-regions, the Western and the Levantine.…”

A Quantitative Management Tool Reflecting Impact of Nutrient Enrichment from Mariculture in the Levantine Basin

“…Following the construction of the Aswan high dam in the 1960s across the Nile river, it has become even more so, since the Nile was an important supply of nutrients to the South East Levantine basin in general and the Israeli coastal zone in particular (Nixon, 2003;Krom et al, 2004). It has been suggested that the anthropogenic nutrient loads, originating from various sources could replace, at least in part, the Nile nutrient supply to the Israeli coastal zone (Powley et al, 2016). Among these sources, mariculture and wastewater treatment facilities can input nutrients directly or indirectly into the coastal zone.…”