Nitrogen Removal by a Nitritation-Anammox Bioreactor at Low Temperature

Abstract

dCurrently, nitritation-anammox (anaerobic ammonium oxidation) bioreactors are designed to treat wastewaters with high ammonium concentrations at mesophilic temperatures (25 to 40°C). The implementation of this technology at ambient temperatures for nitrogen removal from municipal wastewater following carbon removal may lead to more-sustainable technology with energy and cost savings. However, the application of nitritation-anammox bioreactors at low temperatures (characteristic of municipal wastewaters except in tropical and subtropical regions) has not yet been explored. To this end, a laboratory-scale (5-liter) nitritation-anammox sequencing batch reactor was adapted to 12°C in 10 days and operated for more than 300 days to investigate the feasibility of nitrogen removal from synthetic pretreated municipal wastewater by the combination of aerobic ammonium-oxidizing bacteria (AOB) and anammox. The activities of both anammox and AOB were high enough to remove more than 90% of the supplied nitrogen. Multiple aspects, including the presence and activity of anammox, AOB, and aerobic nitrite oxidizers (NOB) and nitrous oxide (N 2 O) emission, were monitored to evaluate the stability of the bioreactor at 12°C. There was no nitrite accumulation throughout the operational period, indicating that anammox bacteria were active at 12°C and that AOB and anammox bacteria outcompeted NOB. Moreover, our results showed that sludge from wastewater treatment plants designed for treating high-ammonium-load wastewaters can be used as seeding sludge for wastewater treatment plants aimed at treating municipal wastewater that has a low temperature and low ammonium concentrations. N itrogen removal from wastewater treatment is necessary because of the significant adverse environmental impact of ammonia/ammonium, such as eutrophication and toxicity to aquatic life, on the receiving bodies. Generally, carbonaceous waste is removed in the first stage of wastewater treatment, which is followed by nitrogen removal systems. Conventionally, the removal of nitrogen (ammonium) is accomplished by the combination of nitrification and denitrification processes. Both of these are energy consuming and are associated with high costs. Moreover, these processes have an additional environmental impact due to high biomass production and greenhouse gas (CO 2 , N 2 O, etc.) emission, which promote global warming.Anaerobic ammonium-oxidizing (anammox) bacteria convert ammonium and nitrite directly to dinitrogen gas (N 2 ) under anoxic conditions. Since they were first detected in a denitrifying pilot plant by Mulder et al. in 1995 (1), anammox bacteria have been found in various oxygen-limited natural (2-4) and manmade ecosystems. The application of the anammox process in wastewater treatment results in significant energy reduction (60%) and greenhouse gas emission (90%) compared to those of traditional biological nitrogen removal processes (5-7). In fullscale nitritation-anammox wastewater treatment plants, ammonium-oxidizing bacteria (AOB) convert approx...

Deterioration of the anammox process at decreasing temperatures and long SRTs

“…This indicates that the optimum temperature, for anammox biomass cultivated at 30°C, 25°C and 20°C, is equal to or higher than the maximum temperature (=30°C) tested in these experiments. A change in temperature optimum for anammox bacteria, cultivated at different temperatures, has been reported in literature for a C. Brocadia fulgida-like strain and a marine anammox strain [29,35]. Nonetheless, this observation was not confirmed in other studies [34].…”

Enhanced ammonia removal at room temperature by pH controlled partial nitrification and subsequent anaerobic ammonium oxidation

“…Although the measurement of the organic matter content in the influent and effluent of the SBR-Anammox system was not performed, the previous characterization of the pretreated pig slurry used to fed the CSTR-partial nitritation reactor indicated that some slowly biodegradable organic matter was present (around 100 mg C·L -1 ) which could be used for denitrification. Another reason of the lower nitrate production respect to the ammonia consumption could be attributed also to the moderate temperatures, since Hu et al [10] observed that the NO 3 -/NH 4 + ratio for the anammox bacteria in a nitritation-anammox SBR decreased from 0.18 to 0.04 when the operational temperature was decreased from 25 to 12 °C.…”

“…Despite the fact that the optimum performance of Anammox bacteria is obtained at 30-40 ºC [8], some studies demonstrated that it is possible the operation of Anammox systems at lower temperatures [9][10][11]. In fact this occurs naturally in the environment, since Anammox bacteria have been detected in various marine and freshwater mediums at low temperatures [12].…”

Lysozyme and Penicillin Inhibit the Growth of Anaerobic Ammonium-Oxidizing Planctomycetes

“…If they were not completely lysed after incubation, the lysozyme-treated cells were pelleted by centrifugation for 5 min at 1,200 ϫ g. Then, the pellet was washed with 10 ml of synthetic medium (37) without substrates 3 times or until it was free of EDTA and lysozyme. The cells were resuspended in 10 ml synthetic medium containing 2 mM ammonium and nitrite, followed by anammox activity tests, as previously described (38), with modifications. In short, 10 ml cells was transferred to a 30-ml serum bottle after the pH was adjusted to 7.3.…”