Phosphorus removal from domestic and industrial wastewater is a key factor in preventing eutrophication of surface waters. Biological phosphorus removal (BPR) in activated sludge systems is one of the most economical and efficient methods for phosphorus removal. The TKN (Total Kjeldahl Nitrogen)/COD ratio indicates the inhibitory effect of nitrate (NO3-) and nitrite (NO2-) in BPR. Nitrate is the by-product of nitrification. It can be introduced into the anaerobic zone by the returned sludge from final clarifiers. Nitrate depletes the limited amount of the readily biodegradable substrate required for the growth of PAOs. Therefore, it is important to control TKN. Therefore AppliTek introduces the on-line TOTAL KJELDAHL NITROGEN (TKN) ANALYZER that generates results every 20 minutes if needed. We also supply also COD analyzer, if you would like to calculate the TKN/COD ratio.