A comparison of floating and sunken media biological aerated filters for nitrification

✍ Scribed by Allan Mann; Leopoldo Mendoza-Espinosa; Tom Stephenson

• Publisher: Wiley (John Wiley & Sons)
• Year: 1998
• Tongue: English
• Weight: 223 KB
• Volume: 72
• Category: Article
• ISSN: 0268-2575
• DOI: 10.1002/(sici)1097-4660(199807)72:3<273::aid-jctb902>3.0.co;2-l

✦ Synopsis

The versatility of the biological aerated Ðlter (BAF) has made it an important process in wastewater treatment. These submerged three-phase Ðxed media reactors have been used in a wide variety of applications in wastewater treatment, such as primary treatment (solids removal), secondary treatment (COD and BOD removal), and tertiary treatment (nitriÐcation). The aim of this work was to investigate the biological start-up of two such reactors to remove suspended solids (SS), total COD (tCOD) and ammonia, one containing a sunken medium (relative density 1É05) and the other containing a Ñoating medium (relative density 0É92), both identical in shape and size. The reactors (0É054 m3 media) were run in parallel in upÑow mode using secondary effluent as the process liquid at a Ñowrate of 0É2 dm3 min~1 and air : liquid ratio of 10 : 1. Overall, Ñoating media performed better than sunken media for SS, tCOD and ammonia removal, probably due to the compression of the bed due to the buoyancy force of the media and the Ñow of air and liquid acting upwards. Bed compression improved solids removal and appeared to have promoted the growth of bacteria. Temperature had a greater impact on nitriÐcation than on carbonaceous matter removal. The Ñoating medium reactor was more resistant to low temperature shocks than the sunken medium reactor but the latter showed a faster recovery time as temperature increased. Although the backwashing frequency used was satisfactory, performance may have improved if the backwashing had been carried out only when reactor performance began to decline. NitriÐcation was shown to follow a reaction rate between zero and half order. Thus, ammonia removal was generally independent of ammonia concentration and more a †ected by the presence of carbonaceous matter.