Abstract：The experiment studied the accumulation of nitrite nitrogen in biofilter packed with bamboo ring while treating Cynoglossus semilaevis mariculture wastewater with high salinity and low ammonia nitrogen loading. Some operating parameters were carried out, including influent organic loading, ammonia nitrogen loading, temperature, pH and dissolved oxygen as well as the denitrification to the influence of nitrite nitrogen accumulation. When the influent organic loading was 0.65~0.75kg/(m3×d), the ammonia nitrogen loading was 0.058~0.077kg/(m3×d), the temperature for 20.9~22.2℃, pH for 7.50~8.14℃ and the dissolved oxygen was under 7.43~9.73mg/L, the low dissolved oxygen in biofilter was the primary cause for nitrite nitrogen accumulation. Meanwhile, the influential factors on nitrite nitrogen accumulation were investigated, including the low dissolved oxygen, the carbon nitrogen ratio (C/N) and the carbon source type in the denitrification process. The denitrification process was potential to create nitrite nitrogen accumulation under the operating conditions. It was confirmed that the denitrification process was affected in the nitrite nitrogen accumulates through further study on nitrogen compounds concentration variation in the biofilter and the denitrifying bacteria. The conclusion showed clearly that the denitrification promoted the nitrite nitrogen accumulates.
