Nitrification of biofilters packed with four different substrates for treating mariculture wastewater

To explore mariculture wastewater removal capacity by biofliter and to acquire the parameters of nitrification kinetics in biofilter for promoting RAS applied study and extensive application, Bamboo Ring, Maifan Stone, Ceramic Pellet and Plastic Ball (PE) substrates were packed into different biofilters. The physical chemistry characters of substrates, COD and ammonia nitrogen removal capacity were investigated and evaluated by simulated mariculture wastewater under five C/T ratio (COD/TA N=0, 0.8, 2, 6, 12). The results showed that 1) COD and TAN removal capacities of biofilter packed with Maifan Stone substrate were the highest under low C/T (<6), with the highest rate of 850 and 21 g/(m3·d) (C/T = 0.8) respectively. The second was the Bamboo Ring substrate, with the highest rate of 750 and 23 g/(m3·d) (C/T = 6) respectively. As carbon concentration improving, the TAN removal rate decreased and COD removal rate increased. 2) Under the condition of 15–22℃ and HRT 0.5 h, nitrobacteria number for different substrates reached a plateau and matured in 40–50 d, Bamboo Ring in 50 d, others in 40 d. Choosing different substrate can impact the running stability of biofilter. Substrate is closely related with biofilm maturation duration and nitrification process, and affects nitrifying capacity obviously. Bamboo Ring substrate can remove TAN with the highest rate under higher C/T (>6) ratio condition and has a potential in RAS production.