A reverse osmosis potable water plant at Alicante University: first years of operation

In 1996, construction was started at Alicante University for a reverse osmosis desalination plant, which began operating in 1997. The water produced has been used for irrigation of the green zones of the campus. The plant was working discontinuously, during trial periods, and when regular supplies of water for irrigating the gardens and green zones on the campus were necessary. The plant draws its supply from a salt water aquifer on which the university is situated. The average water conductivity is around 6,000 µS/cm. The cost of water production from desalination in 1997 was 37.59 pesetas/m3, 40.07 pesetas/m3 in 1998 and 32.52 pts/m3 in 1999.

About 50% of the water consumed at Alicante University is used for irrigation of the green zones. The plant obtains its water supply from a brackish water aquifer on which the university is situated, and whose average conductivity is around 6000 µS/cm. The membranes used in the plant are 8040UHY-ESPA from Hydranautics. Due to the use of these membranes and to the flow of the water produced, the working pressure is 12 kg/cm2. It is important to point out that the plant is fitted with a variable frequency device that controls the operation of the high-pressure pump. By controlling the flow of the water produced and the value of conductivity, the correct functioning of the RO process has been checked. The average conductivity of the product water during the periods of operation was less than 300 µS/cm, increasing from the second year. The fluctuations observed in the conductivity of the product water may be due to the continuous start- up and shut-down of the plant as the water supplied depends on the amount required for irrigation and watering. The working pressure was constant during the whole year as the plant is fitted with a variable frequency device that controls the working pressure keeping it at the level predetermined at the time of start-up the plant (12 kg/cm2). In 1997 the cost of production of the water obtained by desalination was 37.59 pts/m3 , 41.07 pts/m3 in 1998 and 32.52 in 1999. It has been estimated that the cost of water extracted from the aquifer and used for irrigation without being desalinated is 3.5 pts/m3. Adding the savings obtained by desalination to that obtained by the direct application of salt water, the total saving amounts to 7,250,000 pts in 1997, 10,000,000 in 1998 and 12,500,000 in 1999.