Untitled

Kuwait Institute for Scientific Research (KISR) and the Ministry of Electricity and Water (MEW) collaborated over the past 15 years in developing and adapting the seawater reverse osmosis (RO) technology to the Gulf seawater conditions (one and half time the salinity of open seas and large temperature variations between summer and winter in the range of 35°C and 10°C, respectively). The development process went through several stages involving performance evaluation of three types of membrane configurations under various operating conditions and using different types of feed water pretreatment techniques. It went also through the evaluation of various commercially available energy recovery systems and the development of a new system. During this period, the RO research program evaluated the performance of ten different seawater membranes, cleaning and restoration techniques and procedures, using various potential agents. Furthermore, computer aided design program and process design and optimization procedures were developed specifically for Gulf seawater conditions. The studies also involved two-phase evaluation of multistage flash/reverse osmosis (MSF/RO) hybrid systems. Cost assessment of product water from RO under different operating conditions and various system configurations was always an important integrated part of each research project.

The research activities carried out at the DROP over the past 15 years had resulted in many important achievements in RO system’s performance including: 1. The reliability of the reverse osmosis technology in Kuwait under the severe conditions of the Gulf seawater; very high salinity (5% salt content) and temperature variation between winter and summer (10–35°C) as indicated by four years of continuous successful operation of three commercial reverse osmosis units at DROP. 2. High load factor of the reverse osmosis plants (exceeding 90%) has been achieved. 3. Operational results obtained from DROP, proved that polyamide and composite seawater RO membranes are reliable to produce desalinated water for a long period (more than three years). 4. Hollow fiber and spiral wound modules are reliable to desalinate Gulf seawater, while the plate and frame modules are not suitable due to technical and economic reasons. 5. Substantial reduction in capital and operating costs (estimated at 25% of the total water product costs) through a single-stage desalination system instead of a two-stage system. 6. The cost of unit water production using seawater RO technology is less by one third compared to the cost of the same unit produced by MSF. 7. CAD program capable of predicting RO membrane performances within reasonable accuracy over time under normal operating conditions pertinent to Gulf seawater has been developed. 8. Design criteria and technical specifications for commercial seawater RO plants were established. 9. Preliminary evaluation of seawater RO implementation in Kuwait was made. 10. Experimental testing of MSF/RO hybrid systems have demonstrated significant gains in product water recovery, reductions in electric energy consumption, hence reduced overall product water unit cost. 11. Long-term evaluation of Pelton wheel energy recovery systems proved to be reliable and have no negative effect on RO plants availability. However, these machines exhibit an overall mechanical efficiency within the range of 70 to 80%. 12. Energy recovery using pressure exchanger device has been developed, tested, and proved 0.022 0.175 0.046 0.030 0.084 0.015 RO membranes Variable costs: Labor Chemicals Energy Spare parts and maintenance 0.245 0.048 Depreciation US$*/m3 *1 KD = US$ 3.33 0.816 KD/ m3 Total costs: 0.070 Fixed costs: 06.12 34.29 12.24 18.78 71.43 08.98 19.59 28.57 0.619 0.186 0.008 0.084 0.029 0.016 0.137 0.021 0.028 0.049 04.30 45.16 15.60 08.60 73.66 11.29 15.05 26.34 % total 0.836 0.251 0.015 0.095 0.011 0.046 0.167 0.037 0.047 0.084 KD/m³ 05.97 37.85 04.38 18.33 66.53 14.74 18.73 33.47 % total KD/m³ KD/m³ % total 4,550 m³/d 27,300 m³/d 4,550 m³/d 0.653 0.196 0.009 0.095 0.011 0.017 0.132 0.036 0.028 0.064 KD/m³ 04.59 48.47 05.61 08.68 67.75 18.37 14.28 32.65 % total 27,300 m³/d RO using beachwell MSF/RO hybrid system 0.902 0.271 0.015 0.095 0.030 0.046 0.186 0.037 0.048 0.085 KD/m³ 05.54 35.05 11.07 16.98 68.64 13.65 17.71 31.36 % total 4,550 m³/d 0.713 0.214 0.009 0.095 0.029 0.017 0.150 0.036 0.028 0.064 KD/m³ 04.20 44.40 13.56 07.94 70.10 16.82 13.08 29.90 % total 27,300 m³/d RO using surface seawater Table 1 Comparison of unit product water cost of seawater desalination for spiral wound RO membrane configuration under different operating conditions. Energy recovery was included in all cases 0.022 0.201 0.046 0.030 0.110 0.015 RO membranes Variable costs: Labor Chemicals Energy Spare parts and maintenance 0.271 0.048 Depreciation US$*/m3 *1 KD = US$ 3.33 0.902 KD/ m3 Total costs: 0.070 Fixed costs: 05.54 40.59 11.07 16.97 74.17 08.12 17.71 25.83 0.709 0.213 0.009 0.110 0.029 0.016 0.164 0.021 0.028 0.049 04.22 51.64 13.62 07.52 77.00 09.86 13.14 23.00 % total 0.909 0.273 0.015 0.117 0.011 0.046 0.189 0.037 0.047 0.084 KD/m³ 05.49 42.86 04.03 16.85 69.23 13.55 17.22 30.77 % total KD/m³ KD/m³ % total 4,550 m³/d 27,300 m³/d 4,550 m³/d 0.786 0.218 0.009 0.117 0.011 0.017 0.154 0.036 0.028 0.064 KD/m³ 04.13 53.67 05.04 07.80 70.64 16.51 12.85 29.36 % total 27,300 m³/d RO using beachwell MSF/RO hybrid system 0.976 0.293 0.015 0.117 0.030 0.046 0.208 0.037 0.048 0.085 KD/m³ 05.12 39.93 10.24 15.70 70.99 12.63 16.38 29.01 % total 4,550 m³/d 0.786 0.236 0.009 0.117 0.029 0.017 0.172 0.036 0.028 0.064 KD/m³ 03.81 49.58 12.29 07.20 72.88 15.26 11.86 27.12 % total 27,300 m³/d RO using surface seawater Table 2 Comparison of unit product water cost of seawater desalination for hollow fiber RO membrane configuration under different operating conditions. Energy recovery was included in all cases highly efficient. Overall device efficiencies above 90% are attainable. 13. Feasible research areas to enhance the development of seawater RO technology were identified. Research projects were aimed at improving the state of development of the RO technology, establishing technical and economic data base needed for decision-making for future application of the technology in Kuwait.