Efficiency of nitrification in trickling filters using different filter media

The efficiency of nitrifying trickling filters varies with media type. Thre e sizes of crushed Leca (dried expanded clay) and three types of plastic me dia (Kaldnes rings, Norton rings, and a rolled mat of Finturf artificial gr ass) were tested in columns 1.5 m high and 11 cm in diameter. Synthetic wat er containing 1.5 mg total ammonia nitrogen (TAN) l(-1) and 1 mg PO43- 1(-1 ) was added at a rate of 0.5 1 min(-1) and a temperature of 15 degrees C. T he nitrification rate stabilised 7-8 weeks after start-up in the Leca fract ions and artificial grass columns. For the other two media, no positive sta bilization was observed over the duration of the experiment (140 days). At the end of the experimental period, the nitrification rate was 100% in the Leca fraction columns, 80% in the Kaldnes ring columns, 60% in the Norton r ing columns and 40% in the artificial grass columns. The nitrification rate was between 0.1 and 0.2 g TAN m(-2) day(-1) in the different columns, and the hydraulic load was below 0.25 m(3) m(-2) day(-1). (C) 2000 Elsevier Sci ence B.V. All rights reserved.