Improved industrial water management through membrane processes — the case of a large thermo-electric power plant

Advanced membrane technology can significantly improve water management in large, land-locked power plants such as the Agios Dimitrios Power Station in Northern Greece. A review of the present water treatment facilities and of water requirements in this power station was carried out, to identify potential areas of improvement. Six alternative designs were studied, which included membrane treatment and recycling of industrial wastewater as well as membrane treatment of at least part of raw feed-water, in order to determine the most attractive ones. It was shown that membrane processes can improve water management, resulting in significant reduction of required raw water and in reduced total annual treatment cost. Other potential benefits of a membrane based water treatment plant include better and more stable quality of water produced as well as an extra assurance that the power station can better cope with future raw water limitations due to natural or legislative reasons. Out of the six alternative designs considered, the most attractive ones are identified using economic and environmental criteria.

Advanced membrane technology can significantly improve water management in large “landlocked” power plants such as the Agios Dimitrios Power Station in Northern Greece. Indeed, Table 7 Electricity needs for raw water transportation and water treatment system Alternative cases Electricity needs (GWh/y) % Reduction of electricity needs Existing Case #1 Case #2.1 Case #2.2 Case #3.1 Case #3.2 Case #4 40.787 50.242 43.109 37.472 35.196 34.133 38.768 – –23.2 –5.7 8.1 13.8 16.3 4.9 recycling of wastewater that cannot be adequately treated by conventional technology, and treating by membranes at least part of raw feed-water, can result in significant reduction of required raw feed-water as well as of annual water treatment cost. Other potential benefits of an installed membrane plant include better and more stable overall quality of produced water as well as an extra assurance that the power plant could better face natural or administrative/legal feed-water limitations. It is pointed out, however, that consideration should also be given to required capital investment for such a membrane installation, by employing usual economic criteria. Based on the above considerations, one of the studied alternatives, representing an RO system for treatment-recycling of blow-down, to be used as ion exchange feed-water, is quite attractive, both economically and environmentally, leading to an annual cost reduction of approx. 6% and to raw water savings of 5%, as well as to drastic reduction of polluting chemicals employed for ion exchange regeneration. Another attractive alternative case, substituting part of the existing lime treatment technology, leads to an annual cost reduction of approx. 3.8% and to much greater raw water savings (21%), with similar drastic reduction of chemicals as in the previous case and significant net reduction of electric energy requirements by approx. 6.65 MWh/y or 16.3%, in comparison to the present water treatment system.