The Deammonification Process in Moving Bed Biofilm Reactors

Reference should be written as: " Yang, J. (2016). The deammonification process in moving bed biofilm reactors. PhD thesis. TRITA LWR PHD-2016:05 ". SUMMARY In order to decrease the risk of eutrophication in natural water bodies, the requirements for wastewater treatment plants' (WWTPs) discharge has become stricter than previously. Around 15-20% of the nitrogen load in the mainstream comes from reject water which is produced in sludge treatment line. The partial nitritation/anammox process, which is also called deammonification, appears to be a good alternative to treat reject water. However, for this process to be effective, control strategies which are reliable and require less maintenance are needed. In this thesis, different control strategies were studied at pilot scale in order to optimise the deammonification process operated in a Moving Bed Biofilm Reactor (MBBR) for reject water treatment. Meanwhile, the processes were monitored by microbial activity tests, Specific Anammox Activity (SAA), Oxygen Uptake Rate (OUR), and Nitrate Uptake Rate (NUR) tests, in order to measure the anammox, ammonium and nitrite oxidizers and denitrifiers activity, respectively. Intermittent aeration and redox (ORP) as control parameters were studied. The results showed that intermittent aeration, with 15min non-aerated period in one hour cycle, could reduce the aeration time without any loss of process efficiency. A Redox value of pE=0 gave the best operational condition. When the redox value was fixed at 0, the aeration could adjust itself even if there was different nitrogen loads applied in the system. Pilot scale plants with deammonification MBBR were operated at decreasing temperatures and diluted influent nitrogen concentrations towards to mainstream conditions. The reactor was run at different temperatures (25-19°C) to test the process stability and it showed that the process started to become unstable when the temperature was at 19°C. Free ammonia (FA) concentration in the reactor increased even though the nitrogen load and DO concentration were adjusted. Moreover, a new treatment line with combined Upflow Anaerobic Sludge Blanket (UASB) reactor and MBBR with deammonification process was established, with the aim of being applied in the mainstream treatment. The study results indicated that when the influent of deammonification process shifted from reject water to UASB effluent, which corresponded to an inlet ammonium concentration of 100 mg/l, the deammonification started to show unstable performance. During the whole operation, anammox and ammonium oxidizers were the dominating groups of bacteria. Due to the increased attention on global warming and greenhouse gas emissions, …