Denitrification by gel beads In order to analyze the denitrifying characteristics of the gel beads, 0-30g of gel beads as put into a 1.5-l Roux bottle with 1 1 of denitrifying medium (10) and denitrification was carried out for 20 d at 30°C under dark anaerobic conditions
(the medium was sparged with nitogen gas for several minuts during each sampling period). The medium with gel beads was gently agitated with a magnetic stirrer (approximately 100rpm) in order to maintain its homogeneity. The composition of the denitrifying medium was as follows (g/l): glucose 1.0, KN03 1.08, KH2P04 0.11, (NH&SO4 1 .O, yeast extract 0.1, thiamine-HCl 1 x 10 3, nicotinic acid 1 x lop3 and biotin 1 x low5 (10).