Scientists to probe outlet brine risks to sealife

Scientists have been commissioned to investigate whether brine waste from two proposed 150 Ml/d seawater reverse osmosis desalination plants could damage or alter the marine environment along the KwaZulu-Natal coastline in South Africa.

The studies, to be coordinated by south Africa’s Council for Scientific and Industrial Research (CSIR) will be part of a proposal by utility Umgeni Water to build one or two desalination plants to boost Durban’s dwindling fresh water supplies.

One of the studies will examine the environmental impacts of pumping daily about 180 Ml of concentrated brine into the sea near Tongaat north of Durban and and at Illovu south of the city.

The brine was expected to be about 1.7 times more saline than sea water. Umgeni said that a diffuser on the outlet pipes would ensure that the brine effluent was diluted to about 3% above normal salinity levels within 10 m of the diffuser points. The brine would be pumped to sea through outlet pipes extending 350-500 m offshore.It antiquated that potential environmental impacts were likely to be restricted to a small area close to the dispersal pipeline.

In a recent draft report CSIR said brine disposal caused “significant detrimental effects” on coastal environments in parts of the Middle East and other coastlines with shallow water and low wave and tidal energy.

CSIR said brine could sink and smother the seabed unless it was dispersed rapidly by currents.

It cited studies undertaken in the early 1990s that concluded that brine discharges reduced populations of fish, plankton, and coral in the Red Sea
Spanish researchers who in 2007 documented significant changes in sea life populations close to a desalination plant near Alicante.

The CSIR has recommended further studies into the effect of different water temperatures on marine life, since the brine water discharges were likely to be about 1.5ºC above normal sea temperature.