Organic removal by denitritation and methanogenesis and nitrogen removal by nitritation from landfill leachate.
A system consisting of a two-stage UASB and anoxic-oxic reactor was used to enhance COD and nitrogen removal from landfill leachate. To improve denitrification efficiency, the raw leachate with recycled final effluent was pumped into the first-stage UASB (UASB1) to carry out simultaneous denitrification and methanogenesis. The results over 180 d show that the maximum organic removal rate in UASB1 and UASB2 was 12.5 and 8.5 kgCODm(-3)d(-1) in the oxic zone of the A/O reactor, respectively. The COD and biochemical oxygen demand (BOD5) removal efficiency of the system was 80-92% and about 99%, respectively. Without controlling temperature (17-30 degrees C) and dissolved oxygen (0.5-4.0 mgL(-1)), the maximum NH4+-N removal rate was 0.68 kg NH4+-Nm(-3)d(-1), and about 99% of NH4+-N removal was obtained by nearly complete nitritation. The 81-93% total nitrogen removal was obtained by complete denitrification in the UASB1 and in the anoxic zone of the A/O reactor. Fluorescence in situ hybridization (FISH) analysis of the sludge samples from A/O reactor showed that ammonia oxidizing bacteria (AOB) consisted 4% of the eubacterium, while nitrite oxidizing bacteria (NOB) counted less than 0.2% of that. The study shows that the main factors achieving and maintaining nitritation are a proper range of free ammonia concentration obtained by dilution recycled final effluent that inhibits NOB but not AOB; effective control on aeration time by indication of "ammonia valley" on pH profile; and highly efficient denitrification and its reproducing alkalinity to result in pH above 8.5.
Peng
Yongzhen
Y
Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Environmental and Energy Engineering College, Beijing University of Technology, Beijing 100022, China. pyz@bjut.edu.cn
Zhang
Shujun
S
Zeng
Wei
W
Zheng
Shuwen
S
Mino
Takashi
T
Satoh
Hiroyasu
H
D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors; D017404:In Situ Hybridization, Fluorescence; D008697:Methane / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012037:Refuse Disposal; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods
D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D009584:Nitrogen; D008697:Methane