Problems related to an existing marine outfall: Marmaris - an example

Abstract

Marmaris is a tourist city on the South-west Coast of Turkey. A sewage disposal project for Marmaris with an estimated population of 39,000 (excluding the temporary tourist population) for the year 2012, was completed in 1982. The sewage disposal system consisted of wastewater collection, treatment and deep sea discharge. The length of discharge pipe was determined as 520 m and a diffuser was placed 20 m below the sea level, so that the total coliform concentration at the protection zone boundary could be less than 1000/100 ml.

Following the approval of the project, a wastewater collection and marine disposal system was constructed. The material of the discharge pipe was selected as glass reinforced plastic (GRP). The pipe was buried up to a point 10 m below sea level, so that effects of hydrodynamic forces would be minimized. After that point, the pipe was supported at some location by grout bags due to the uneven sea bed. A few years later, it was recognized that the discharge pipe was broken. The fragile GRP material had fractured as a result of the sliding of some of the supports with resultant free spanning conditions. As a result, the pipe had broken at one point. Although the breakage was repaired, recent data have shown that the water quality in Marmaris Bay has a tendency to be worsening; consequently, adding biological treatment units to the present system is advisable.