On the economic comparison of reverse osmosis
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Many years ago, the use of water treatment membranes involved an issue of economic comparison. The critical point for comparing the economics of reverse osmosis and conventional ion exchange is about 500ppm TDS. When it is greater than 500, reverse osmosis is more economical.； As the price of membrane elements decreases and the cost per unit of water production decreases, the critical point should now be around 150 mg/L. This post was last edited by johncom on 2009-2-24 18:35 ]
LZ, are you ready for your news? The critical point is 150. Why are the prices of membrane treatment equipment on the market still high and the cheap ones have poor treatment effects?
On the one hand, it depends on the level of water quality TDS, on the other hand, it depends on the treatment water volume and effluent water quality requirements. For less than 1T/H, conventional ion exchange (anion and cation resin exchange) is more economical. An RO greater than 10T/H is more reasonable. If the water quality requirements are high, reverse osmosis + ion exchange is required.
The raw water has high salt content. When the water volume is large, reverse osmosis or other membrane treatment methods are more economical, simple to operate, low acid and alkali consumption, long operation cycle, and low environmental pollution. Processes that require demineralized water generally use single-stage reverse osmosis plus a two-stage mixed bed or bipolar reverse osmosis plus a single-stage mixed bed. The effluent meets the standards of secondary demineralized water or primary demineralized water.
How did the original poster calculate the TDS of 150 mg/L? I have heard of 500 in the past, but 150 seems a bit low, and there is also a limit on the system output, which seems to require a system of 30-50m3/h or more. In addition, for the economic comparison of reverse osmosis, it mainly depends on the operating cost of the RO system and the total investment cost comparison. The investment cost can be recovered in the shortest time through saved operating costs. For the RO system, the most critical operating costs are the cost of raw water and electricity. The cost of membrane replacement is only a small part, so it cannot be said in general terms about how much TDS there is.
I also agree that the comparison of system economics should be carried out under the condition of determining the processing volume.