Mossel Bay desalination usage quandary for council

The Mossel Bay Town Council in South Africa is debating what to do with its new 15,000 m³/d seawater desalination plant because all the town’s water supply dams are full.

Although a desalination plant had been envisaged in the longer term to supplement the municipality’s water sources as well as to keep pace with development requirements, the district around Mossel Bay was in November 2009 declared a disaster area because of the worst drought in the 132 years that records had been kept.

When construction of the project commenced in June 2010, it was estimated that the Wolwedans Dam, Mossel Bay’s main source of water, would run dry in October 2010. The prognosis was also that the drought could continue for several more years. Sufficient rain since October 2010 has resulted in all Mossel Bay’s dams being virtually full at the moment.

The Town Council at its monthly meeting on 29 September 2011 gave approval to the municipality to take up a loan of R 30 million (US$ 3.5 million) for the partial financing of the seawater desalination plant that was completed in September 2011 at a cost of R 210 million (US$ 24.5 million).

Several options for the operation of the plant are being considered at present. One is to operate the plant at its full capacity of 15,000 m³/d, while another is to operate it at a minimum rate of 2,500 m³/d.

Another option is to mothball the plant until it is required, depending on the town’s water demand. The council says that this is an expensive option for a plant of this size.