FULL-SCALE DEMONSTRATION OF A FREE-MOVING MEDIA IFAS PROCESS FOR ENHANCING NITRIFICATION PERFORMANCE

This paper presents the significant results, findings and conclusions of a full-scale demonstration project on the application of an integrated fixed film activated sludge (IFAS) system using a free-floating plastic media. The purpose of the project was to attain complete nitrification and partial denitrification in an existing plant without adding bioreactor tankage or settling capacity. The study was conducted in a 7.5 ML/d module of the Christies Beach WWTP in South Australia over 8 months, commencing in April 1999. The performance of the IFAS trial train was limited by low dissolved oxygen conditions in the media zones. The aeration system was unable to meet the oxygen demand as a result of turning off a number of the aeration lines in the tank to induce a roll pattern to mix the media. However, batch tests conducted on media and mixed liquor removed from the trial train provided a clear indication of the enhancement in nitrification rates provided by the media. Analysis and simulation of the batch test results showed that adding media doubled the effective nitrification rate.