Evaluation of Activated Sludge with a Submerged Fixed Bed in the Removal of Phosphorus and Nitrogen Compounds from Hospital Wastewater

Aerobic treatment processes with fixed growths exhibit a high efficiency not only in the removal of organic materials and phosphorus but also in the nitrification process (conversion of ammonium to nitrate) in wastewater. The present study aims to evaluate the performance of activated sludge with a submerged fixed bed in the removal of phosphorus and nitrogen compounds from wastewater. For this purpose, a reactor was initially constructed and commissioned before the activated sludge with a submerged fixed bed was loaded. A total number of 225 samples were collected from the wastewater treatment plant at Farabi General Hospital in Kermanshah to evaluate the removal efficiency of ammonia nitrogen, total nitrogen, nitrite, nitrate, and phosphate over three different retention times (2.9 hours of aerobic and 1.1 hours of anaerobic operation; 3.6 hours ofaerobic and 1.4 hours of anaerobic operation; and 4 hours of aerobic and 1.5 hours of anaerobic operation). Phosphorus, ammonia nitrogen, nitrite, and nitrate measurements were performed according to the Standard methods 4500-P, 4500-NH3, 4500-NO2, and 4500-NO3, respectively. Results showed that the highest phosphorus removal (53%) was achieved with Phase III of the system (i.e., 4 hours of aerobic plus 1.5 hours of anaerobic operation) while the highest ammonia nitrogen removal (97%) and TKN (96%) were achieved in Phase II of the system (i.e., 3.6 hours of aerobic and 1.4 hours of anaerobic operation). Significant differences (Pvalu