Study of the alternating-aerobic-anoxic (AAA) process in a single-reactor biological fluidized bed system

One of the serious environmental problems that the human beings are facing is the nitrogenous pollution. It comes along with the perturbed nitrogen cycle in the nature and is mostly caused by human activities. NH4 +, NO2–-N, and NO3 --N are three major nitrogenous pollutants widely seen in the environment and known by most people. They are also the target compounds this thesis primarily focuses on. Traditional nitrogen removal techniques apply the nitrification process to biodegrade NH4+, but accumulate NO3 --N in the treated body. The alternating-aerobic-anoxic process combines both nitrification and denitrification in one system. Therefore, it can not only remove NH4+ by nitrification but also eliminate NO3--N by denitrification. NO2 --N exists in the system as an intermediate product of both nitrification and denitrification. The AAA process also shows the capability of removing TOC, which is oxidized under the aerobic condition and consumed by heterotrophs in the anoxic stage. If the organic carbon source is directly obtained from the existing waste stream, costs on adding external carbon will be saved. Successfully applying the biological fluidized bed reactor to the AAA process is proved in this thesis. Its advantages include saving space, eliminating sludge problems, and removing carbon and nitrogen efficiently. Due to the alternating aeration, the aeration/non-aeration ratio is one of the important factors affecting the performance of the AAA process. For free NH4+ and easily biodegradable carbon (e.g. glucose), the optimal aeration/non-aeration ratio is within a close range around 1. For a complex aromatic amine (e.g. aniline), due to its low denitrification rate, the non-aeration duration should be correspondingly increased and this makes the aeration/non-aeration ratio less than 1. Accumulation of the organic carbon in the anoxic stage is the distinguished result of a longer non-aeration process when dealing with slowly biodegradable organic compounds. Applying the results of this thesis to the design of the AAA process for the joint aquacultural project between the University of Pennsylvania and the Delaware River Port Authority of Pennsylvania and New Jersey is expected in the near future. The success of the AAA process in removing aniline claims its potential application to removing toxic nitrogen containing organic compounds