In the Plaine Wilhems system, sewage is sent to the Saint Martin treatment plant. There the treatment consists of screening, disintegration of solids and removal of grit. Then the effluent is discharged out to sea at Pointe Moyenne through a 600 metres out fall. In the Coromandel system, the treatment consists of screening, disintegration of solids and removal of grit before discharge into the sea at Pointe aux Sables through an out fall. All the out falls discharge at shallow depth or on the surface.
Little dilution takes place before the waste waters reach the surface.
As a result the reef opposite the Pointe Aux Sables discharge is dead. The government has elaborated a National Sewerage Master Plan for Mauritius with the help of the Severn Trent water authorities and Gibb Partners. Though the report is confidential it appears that in the long term a proliferation of sea out falls around the coast line is not envisaged. The four existing shallow out falls will eventually be decommissioned. In the aforesaid plan, two levels of sewage treatment is being considered.