In 1991, the Water and Electricity Department of Abu Dhabi WED) commissioned a two million imperial gallons per day (9000 m(3)/d) seawater reverse osmosis plant in Jabel Dhana, United Arab Emirates. Initially, the high salinity, hot Gulf seawater RO plant being operated on open sea intake has suffered from biological fouling, low plant availability and high total water cost. Today the plant is operating with a new simplified process, the availability has reached 98% and the running cost has substantially been reduced. The plant represents an outstanding example of the application of several biofouling control technologies recently developed for RO seawater desalination plants. This paper presents in detail the various actions taken at Jabel Dhana to control biological fouling, increase the plant availability to 98% and reduce the plant running cost.