- An Aerated Submerged Biological Filter was used to promote biological nitrification of a synthetic saline wastewater. Black PVC corrugated plates were used to make the structured packing of the 6 liter reactor. Nitrate, nitrite, and ammonia concentrations, pH and DO were periodically measured, according to APHA (1985). In spite of the deleterious effect of salinity, it was possible to obtain nitrogen removal efficiencies as high as 95% for a 25 g/L salt concentration after a three-day reaction in the batch reactor. Continuous operation using a NaCl concentration of 25 g/L was tested using three different hydraulic retention times: 7, 15, and 25 hours. An increase in ammonia removal was observed when the retention time was increased from 7 to 15 hours. However, no further notable increase was obtained for a 25 hour retention time, showing that nitrogen removal tends towards a maximum limit of about 80%