Raw water consumption for desalinated water
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The raw water consumption for desalinated water is related to factors such as the process chosen for its production and the quality of the water. I would like fellow sea water professionals to discuss which desalination process results in relatively lower raw water consumption (i.e., a higher raw water utilization rate) What is the typical utilization rate of raw water? How high can it go?
Currently, the ultrafiltration + secondary reverse osmosis process is generally used, with an overall yield of 60-70%.
In terms of the utilization rate of the raw water, ion exchange seems to have a higher utilization rate, reaching over 90%. The main resource consumed is water used for regeneration; generally, about 5% each is used for acid and alkali regeneration. The exact amount depends on the salt content of the raw water – a higher salt content requires more frequent regeneration, thus leading to greater consumption of raw water； For RO + ion exchange or EDI, the typical water recovery rate is around 60-70%, with the exact value depending on factors such as the salinity and hardness of the raw water. In any case, whatever process is adopted should be subject to economic and technical comparison, taking into account both the investment costs and the cost of producing water per ton.
The recovery rate of water produced by reverse osmosis is generally 65–72%, which is more than 20% higher than that of electrodialysis; thus it can be considered to have a high recovery rate.
The ion exchange method requires relatively less consumption, but it is costly and involves high labor intensity. The consumption rate for reverse osmosis is around 25%–30%, resulting in low operating costs and reduced labor intensity.
The reverse osmosis process has the highest investment cost but also the best performance. The water recovery rate can theoretically reach 75%. There is now a method for re-RO recovery of concentrated wastewater, which can further reduce raw water consumption.