Hello friends,
I am working on the design of the RO system for mining wastewater. I have 115 ppm of BOD in feed. I am always confuse about what should be the maximum limit of BOD in RO feed. Majority of big companies like DOW specifies 5 - 10 ppm of max BOD is allowed in RO feed. However, they are not specifying that whether it should be soluble BOD or insoluble BOD. If we have 100 ppm of soluble BOD than I don't see any reason why we can not use RO. If it is insoluble; than it depends on particle size. I would highly appreciate if some one can give me information about what should be the maximum BOD/COD concentration in RO feed and which type of BOD / COD is allowed? (like soluble, insoluble etc.). Also BOD and COD are generalized terms. There are many compounds fall in this category. Does someone has some type of article or document that includes different type of BODs and CODs and tell us whether they can pass through RO or not.
Many Thanks.
Soluble BOD adversely effect on RO and cause biofouling. Then it is difficult to recover the RO performance.
That is why there is a limit 5-10 ppm. You need to lower the BOD by pretreatment. You can not use RO directly with 100 BOD.
It is not about compounds passing through the RO. it is related to biofouling (cloning the membrane and microbial growth on the RO membrane. This will clog the membrane and will not perform well (your flow rate will reduce and pressure will increase. With biofouling you need a lot of cleaning and some time it is not recoverable).
BOD and COD limit in drinking water should be Zero. In various cases BOD up to 5 ppm is considered as safe.
Agrée with Mr. Amila, it will be more practical to keep low BOD to maintain the efficiency of RO.
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