A client approached me and told that a technician said that if TDS of product water is more than 15, membrane should be replaced because”BUTAS” na raw ung membrane.
Upon hearing this, I almost” FAINTED” because that comment is so destructive on the part of WRS owners. Imagine,that would entail unreasonable expenses in spite of the fact that membrane is still in good working condition.
As per technicality, membrane efficiency is being monitored based on % rejection, if we are to refer on membranes brochure, efficiency is within 98 to 99. +%,however these results were obtained on specific operating condition used by the manufacturer, since, we will not be using the same operating specification here, then it is expected that we will be getting a different result in terms of efficiency.
As a safety factor, we just consider the 95% rejection rate, so mathematically speaking, if feed TDS is 100 ppm, product water is 5 ppm considering the 95% rejection rate. If this result is achieved then there is nothing wrong with the membrane and if rejection rate will become higher, let’s say 99% efficiency, still, nothing is wrong with the membrane, it is better or even best.
Now, if feed TDS will be higher, let’s say 300 ppm, at 95% efficiency then product TDS will be 15, and if we are to adapt what the technician commented, then, we can conclude the membrane is ‘BUTAS’, Crazy!!!!
Always remember that product TDS always depends on feed TDS, if feed TDS is high, product TDS is also high and if feed TDS is higher, then product TDS will also be higher.
Always consider the rejection rate before concluding that your membrane is ‘BUTAS’
Basic formula is feed TDS minus product TDS divide feed TDS times 100,then you get the % rejection rate.FYI
- Orly Shanghai
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