COMPARISON OF TECHNICAL AND ECONOMIC INDICATORS OF BAROMEMBRANE AND ION EXCHANGE TECHNOLOGIES OF WATER DESALATION

Abstract

The capital costs for the implementation of the previously proposed resource-saving low-waste method of combined water softening and desalination have been determined. Calculations were made for one, important stage of water treatment — its desalination. It is shown that regardless of manufacturers and sellers of membranes and devices, all data are satisfactorily described by the same curves. In logarithmic coordinates, the functions of the cost of membranes and devices from their performance are linear at high correlation coefficients, have almost the same angular coefficients, equal to 0.66 and 0.71, respectively, and the straight lines are close to parallel and are separated from each other by 1 unit. This indicates that the cost of membranes is on average ten times less than the price of a reverse osmosis installation, regardless of the performance of the equipment. Variant of the implementation of the process with the use of reverse osmosis equipment and concentration of the retentate for further direct use in the proposed method or processing into products disposed at the water treatment plant (WTP) were considered. It was found that sufficient retentate concentration is achieved only in five reverse osmosis steps. The share of the cost of the retentate concentration equipment is from 25 to 28 % of the capital costs for the reverse osmosis equipment and increases insignificantly with the growth of the WTP productivity. When equipping the WTP with reverse osmosis modules with a productivity equal to the productivity of the installation as a whole, or 100 m³/h, the capital costs are approximately the same. As the productivity of the module decreases to the value common on the market (40–48 and less m³/h), the cost of WTP increases. The performed set of calculations showed that a rational variant of the WTP configuration is the use of reverse osmosis equipment with a capacity of 80–100 m³/h, which is manufactured to order. Ion exchange installations are inferior to reverse osmosis installations in terms of capital costs. However, this applies to installations equipped with modules with a capacity of 80 m³/h or more. With a lower productivity of the modules, the advantage of reverse osmosis is lost. With a module capacity of less than 50 m³/h, reverse osmosis is not competitive with ion exchange in terms of capital costs.