Start-up And Operation Performance Of Novel Biological Nitrogen Removal Processes

Novel biological nitrogen removal processes such as single reactor high activity ammonia removal over nitrite(Sharon) process and anaerobic ammonium oxidation(anammox) process have attracted much attention of quantities of environmental engineers due to their high efficiency, cost-effectiveness and little secondary pollution. Their special treatment performance in ammonium-concentrated wastewater ensures them to outcompete other traditional biological nitrogen processes. Accumulation of nitrite has been the key point for the start-up of Sharon process; and for anammox process, its application in low(or normal) temperature and high salinity environment has always puzzled researchers. This dissertation mainly focuses on two aspecsts: As for anammox process, its start-up and stable operation in anaerobic biofilter are studied. In addition to this, low temperature and halotolerant anammox bacteria is adapted from freshwater anammox bacteria. As for Sharon process, the effects of substrate concentration, environmental conditions and operation conditions on the start-up phase are researched.The main conclusions from the research are as follows:1. For anammox process in freshwater environment, an anammox biofilter with polypropylene loop as carries and flow-buffering region can reach a total nitrogen removal rate(TNRR) of 22.94 kg-N·m-3·d-1. Substrate loading strategy and hydraulic loading strategy can both promote the performance of anammox reactor. By using hydraulic loading strategy, the substrate inhibition limit value of nitrogen can be elevated. Thus, combination of these two strategies can achieve quick start-up of anammox. Low pH can lead to remarkable decrease of anammox reactor performance, which can be recovered by the adjustment of pH and influent substrate concentration.2. For anammox process in seawater environment, after 145 days of salinity acclimation under moderate temperature(37℃), freshwater originated anammox sludge was fully adapted to seawater, with a TNRR of 2.80 kg-N·m-3·d-1, by using seawater with increasing salt concentrations. A TNRR of 4.56 kg-N·m-3·d-1 can also be reached by further acclimation under low temperature(10℃). The anaerobic ammonium oxidizing rate first increased, then decreased, and finally increased again when the seawater content was gradually increased from 0‰ to 30‰. A seawater content of 20‰ was the critical point during the acclimation. In terms of morphological characteristics, cell shape of the halotolerant anammox bacteria was irregular and pilus-like appendages were developed on the cell wall. Change in the bacterial community composition after salinity acclimation was also observed through DGGE. The dominant anammox strain was identified as "Candidatus Kuenenia Stuttgartiensis" based on the sequence of the 16 S rDNA gene. The activity decrease caused by low temperature can be weakened by acclimation. Further acclimation can even lead to activity increase.3. For the start-up of Sharon process under room temperature, ammonium conversion rate and nitrite accumulation rate can both keep around 50%, when ammonium concentration, pH and aeration rate keeps around 149.12-176.88 mg·L-1, 8.44 and 16 L·h-1, respectively. Nitrite accumulation can be achieved by controlling the proportion of aerobic phase and anoxic phase.