The ionic force produced by the layer of ammonium ions on the active layer of the RO and NF membranes is a result of ammonia retention.
The layer of ammonium ions on the membrane surface does not represent a significant additional resistance in the process. How- ever, the increase in NH4+ concentration leads to a high ionic force, producing a decrease in the charge on the membrane, thus reducing AR.
The best membrane for the removal of ammonia compounds in aquaculture is obtained on the basis of a combination of two factors, flux and AR, where the membrane flux for NF270 was more than twice the flux of the others membranes. The limit value for ammonia concentration using the membrane is calculated on the basis of AR. The flux for NF270 for the maximum concentration to be treated is a feed concentration of 11.45 mg/L ammonia, with an operating concentration of 154.08 L/m2 h, giving AR of 75.3% at 16 bar.