Process Control Of Shortcut Nitrification And Functional Microbial Community In A SBR For Anaerobic Digested Piggery Wastewater Treatment

The anaerobic digested piggery wastewater contains high ammonia and CODconcentration, and it has to be treated before discharging to the environment. The CODcan be dislodged by normal aerobic activated sludge processes, but the removal ofnitrogen in the anaerobic digestion liquor is still a problem.By using a sequencing batch reactor (SBR) to treat anaerobic digested piggerywastewater, this study investigated the effects of the temperature, ammonia nitrogenloading rate (NLR), aeration time and aeration rate on shortcut nitrification. Theshortcut nitrification was established in SBR at both28°C and15°C with dissolvedoxygen (DO) from1to2mg/L. But the ammonia removal and nitrite accumulation rate(NAR) decreased from71.1%and96.7%to52.8%and85.4%, respectively, when thetemperature dropped from28°C to15°C. When NLR increased from0.56to2.18kg/(m~3·d) at28°C, though the ammonia removal decreased to48.6%, a NAR as high as96.8%was obtained, indicating an excellent shortcut nitrification had occurred in theSBR. To obtain a superior ammonia oxidation at a higher NLR, extension of aerationtime was performed. But the excessive aeration resulted in an increase in nitrate and adecrease in NAR, which was unfeasible for the shortcut nitrification process in the SBR.The increasing of aeration rate influenced the ammonia removal. The ammonia removaland nitrite accumulation rate (NAR) were61.8%and96.6%, respectively, when theaeration rate was0.2L/min. The ammonia removal and nitrite accumulation rate (NAR)were68.9%and94.4%, respectively, when the aeration rate increased to0.4L/min. Athigher NLR the increasing of the aeration rate can raise the ammonia removal rate andkeep the shortcut nitrification of the system.The DGGE band patterns showed that no significant shift in functional microbialcommunity had happened in the SBR system during all six operation phases, exceptslightly lower abundance of microbiological population in the second phase. Thepolymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) andsequence analysis revealed that the AOB in the SBR system mainly affiliated to thegenera Nitrosomonas and Nitrobacter. The NOB amplified with Nitrospira-targetingprimer pairs affiliated to the genera Acinetobacter, Arthrobacter, Leifsonia.When the temperature decreased from28°C to15°C and the aeration time andaeration rate changed, the population abundance and community structure ofammonia-oxidizing bacteria changed slightly, which infered the ammonia oxidizationcould be maintained in all tested conditions. The determination of nitrite oxidizingbacteria showed that the changes of its community structure was very limited, and that some species only detected at low NLR.