Technical discussion: What is the economic viability of producing demineralized water using reverse osmosis-ion exchange?

The quality of the water produced is good, but the recovery rate is generally around 75%, resulting in high water costs.

Reply to 2# Professional Ethics: Although the initial investment is higher, this device offers significant economic benefits in terms of saving acid, alkali, water, and electricity. In terms of protecting the water environment, it is incomparable to the ion exchange method. But it should also be noted: what are the specific economic benefits? A decision can only be made after detailed calculations and comparisons of water quality, raw materials, electricity, water prices, and other factors.

The demineralized water produced by the reverse osmosis system has excellent quality. It eliminates the previous shortcomings of the old systems, such as severe equipment corrosion, short operating cycles, frequent regeneration, high consumption of acids and bases, high workload for operators, and low level of automation. However, there are also the following issues: First, the membrane elements of the RO system require regular low-pressure flushing, which results in high consumption of fresh water per ton of demineralized water produced ； Second, the one-time equipment investment is too high; just 4 sets of RO units require 4 million yuan. To this end, it is recommended to recycle the low-pressure washing water for the membrane and the backwash concentrate into the waste residue recirculation system ； At the same time, calculations for the optimal chemicals must be carried out to extend the overhaul cycle of the RO system. Overall, the use of reverse osmosis technology for producing demineralized water results in a reduction of 2 yuan in the cost per ton of demineralized water produced, thereby yielding good economic benefits. It also reduces the discharge of acidic and alkaline waste fluids, offering favorable environmental benefits; this clearly shows that reverse osmosis technology has great potential for widespread adoption.

If the water obtained through ion exchange meets the process requirements, there is no need to consider the dual-membrane method. If space is sufficient, again, there is no need for this method. The costs associated with membrane replacement and cleaning can be a hassle. The 25% of concentrated water that is generated will give the folks in the wastewater treatment system a headache.

For water with a salt content of more than 200 mg/L, the reverse osmosis process is preferred; for water with a salt content below 200 mg/L, it depends on the levels of acid and alkali prices in the surrounding area.

Sometimes a limit of 300 mg/L is set; in such cases, reverse osmosis is more cost-effective when the concentration exceeds this limit, while ion exchange is more cost-effective when it is below this limit

Both ion exchange and RO certainly have their limitations; each method has its own arguments, and are there any more authoritative opinions?