Denitrification performance of bamboo shavings-iron coupled system for low C/N ration wastewater

To address the problem of insufficient removal of total nitrogen (TN) from low C/N ratio effluent, fibrous bamboo shavings were used as a solid carbon source and elemental iron powder as an iron source, and the coupling of the two materials was used for nitrogen removal. Static denitrification experiments were conducted to investigate the effect of different Fe/C mass ratios on nitrate-nitrogen (NO₃ ⁻-N) removal and to determine the appropriate Fe/C ratio for the coupled system. On this basis, the dynamic denitrification test was divided into a control group of simple bamboo shavings (1^#) and a test group of coupled fillers (2^#) to study their denitrification performance. The results of static tests showed that the NO₃ ⁻-N removal rate of the coupled system with the addition of iron powder was higher than that of the simple bamboo shavings system, but when Fe/C was greater than 0.125: 1, the improvement of NO₃ ⁻-N removal was not significant. Taking into account the denitrification effect and cost, Fe/C ratio of the coupled fillers in the dynamic test was determined to be 0.125∶1. The dynamic test results showed that, when the influent TOC was <2 mg/L , TN was (40.93±2.04) mg/L, and hydraulic retention time of 18 h, the denitrification efficiency of 1^# and 2^# stabilized after running about 10 d. 12-81 d, the effluent TOC of both groups were low, and the average TN removal rates of 1^# and 2^# were 32.99% and 75.58%, respectively, and TN removal rate of 2^# increased by 129% higher than that of 1^#; both groups had some nitrite nitrogen (NO₂ ⁻-N) accumulation, but the NO₂ ⁻-N concentration of 2^# was about 47% lower than that of 1^#; the average concentration of total iron in the effluent of 2^# was lower than the limit value of Surface Water Environmental Quality Standard (GB 3838-2002), and there was no excessive iron release and obvious ammonia nitrogen (NH₃-N) accumulation. In conclusion, the bamboo shavings-iron coupled system has significant denitrification efficiency and low secondary effects. China is rich in bamboo resources and has a wide source of iron, and the bamboo shavings-iron coupled system can be used for TN removal of low C/N ratio domestic wastewater.