Treatment of Arabian Sea Water for Industrial/Domestic Use

I live in Karachi, which is a port city at Arabian Sea or the Indian Ocean. Karachi is a big industrial city and all the water comes from a Canal River Indus.

Can anyone suggest how we can treat the sea water for industry/domestic use in an economical way?

A few years ago Siemens Pakistan installed a Desalination/power plant but it failed soon due to some technical problems. Karachiates are facing serious water scarcity problems.