Recreational Water Quality of Mar del Plata (Argentina) Beaches after Outfall System

After 30 years of technical and economic difficulties, the submarine outfall of Mar del Plata (Argentina) began operation in December 2014. The outfall consists of a HDPE pipe of 4120 m long and 2 m diameter, installed perpendicular to the coast. It includes a 540 m diffuser system comprising 89 ports of 150 mm diameter discharging alternatively every 6 meters north and south. It was designed for a future flow of 9m3/s, although the present sewage flow average is 2.8m3/s in winter and 3.5m3/s in summer. The water depth of the discharge is between 12 and 13.5 m. The new WWTP, inaugurated in 2018, have coarse and fine grids, grit chambers and degreasers prior to 3 mm rotary sieves.

The paper presents the results of the beach recreational quality monitoring program undertaken since 1995, which shows the evolution of microbiological indicators of faecal contamination (Escherichia coli and fecal enterococci) in the city’s coastline, 45 kilometres long, before and after operation of the outfall. It also includes the beach management mitigation programme to preserve recreational marine water quality while the submarine outfall was being constructed 2008 - 2013, specifically; the pretreatment effluent chlorination based on the use of “Virtual Beach” an empirical model, in order of showing a methodology that could be applied to other cities in the region.

The 2014-2015 summer results showed the immediate effect of the submarine outfall in maintaining the water quality of Mar del Plata beaches, without the need for chlorination until today. Therefore, the new submarine outfall achieved the objective of protecting the health of the bather population and the tourism industry. At present Submarine outfall with a WWTP allows works on the certification of beaches and promote the economic development of the city

In addition, Escherichia coli and enterococci bacterial decay measurements in the far field, including precision salinity measurements are presented. Preliminary information from the T90 study is provided for better understanding and adjustment of variables that explain the results found at beaches, as well as to make a contribution for future outfall modeling at similar latitudes.