Effect of low aeration rate on simultaneous nitrification and denitrification in an intermittent aeration aged refuse bioreactor treating leachate

Three intermittent aeration aged refuse bioreactors (ARBs), A, B, and C, with aeration rates of 670, 1340, and 2010 L/m3 aged refuse·d in stage 1, and 670, 503, and 335 L/m3 aged refuse·d in stage 2 were constructed to evaluate the effect of low aeration rate on leachate treatment by simultaneous nitrification and denitrification (SND). Results show that SND can be achieved and improved by reasonably adjusting the aeration rate of the ARB. In stage 1, the average chemical oxygen demand (COD) removal rates of ARBs A, B, and C were 91%, 92%, and 93%, respectively. The ammonia nitrogen (NH4+-N) removal rate of the three ARBs approached 100%. The total nitrogen (TN) average removal rates were 68%, 59%, and 57%. The average SND efficiency values were 73%, 66%, and 65%. In stage 2, the COD removal rates of ARBs A, B, and C decreased from the original values of 85%, 92%, and 93% to 84%, 81%, and 80%. The NH4+-N removal rate decreased from above 99% to 90%-92% in ARB B and from above 99% to 87%-91% in ARB C. The TN removal rates of ARBs B and C increased to 59% and 53% on day 15 from the initial values of 49% and 43% and were maintained at 49%-61% and 50%-60%. The SND efficiency of ARBs B and C improved, and the average values were 68% and 70% after day 15. These values were higher than the 66% of ARB A during the same period. Comprehensively considering the COD, NH4+-N, TN removal rate, and SND efficiency, the optimal aeration rate of 670 L/m3 aged refuse·d is therefore suggested in this study.