The effect of hydraulic energy recovery in a small sea water reverse osmosis desalination system; experimental and economical evaluation

This paper presents the experimental results of a small Sea Water Reverse Osmosis desalination system equipped with a hydraulic energy recovery unit of the Eco systems Clark pump type. The system is installed at the Agricultural University of Athens, and has been in continuous operation since January 2004. The system has a maximum fresh water production of 2.6 m3/day, with an average quality of 250 μS/cm, using two spiral wound SWRO membranes connected in series. The feed water is a NaCl solution with an Electrical Conductivity of 35 mS/cm, typically isoosmotic with the sea water. The only electrical consumption of this system is a brushless DC motor directly coupled to a feed water rotary vane pump. This motor is powered from a small battery bank of 310 Ah. The measured specific energy consumption reached up to 3 kWh/m3, while other small sea water reverse osmosis systems without energy recovery reported specific energy consumption as high as 10-20 kWh/m3. The measured low energy consumption of the present system makes it suitable for future coupling with renewable energy systems such as photovoltaics and wind generators.