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A full‐scale biofilm‐enhanced aerated lagoon using fixed submerged media was monitored using automated water quality monitoring stations over the span of one year to quantify its nitrification performance. The system was operating at a high organic loading rate averaging 5.8 g total CBOD5/m2 of media per day (23.9 g total CBOD5/m3 of lagoon per day), a total ammonia nitrogen loading rate averaging 0.9 g NH4‐N/m2 day (3.7 g NH4‐N/m3 day), and temperatures ranging from 1.6 to 20.8°C. The system showed an extended seasonal nitrification period compared with a simulated aerated lagoon system of the same dimensions. This extension of complete nitrification with approximately 1 month was observed in the fall despite the decrease of operating temperature down to 4°C. During this maximum nitrification period, substantial denitrification occurred, and the effluent un‐ionized ammonia ratio was reduced. A temporary loss of nitrification was also experienced in relation to an episode of elevated suspended solids concentration. Measured biofilm characteristics, namely the detachment dynamics and the biofilm thickness, were used to explain this temporary nitrification loss. During wintertime, a low nitrate production was still observed, suggesting year‐long retention of nitrifying bacteria in the biofilm. Practitioner points: Nitrification in a highly loaded biofilm‐enhanced aerated lagoon is mainly affected by operating temperature. Maximum nitrification is observed during the warmer months and occurs even at high organic loading rates (>5 g CBOD5/m2 day).Compared with a simulated suspended growth system, the biofilm‐enhanced lagoon shows a significantly extended nitrification period. The extension is observed at the end of the summertime maximum nitrification period.Low amounts of nitrate still produced during winter in the biofilm‐enhanced aerated lagoon suggest year‐long retention of autotrophic nitrifying biomass in the biofilm.Nitrification in the biofilm‐enhanced aerated lagoon is negatively impacted by the presence of important quantities of accumulated solids that resuspend when their digestion starts as temperature increases. [ABSTRACT FROM AUTHOR]

This study aims to investigate moving bed biofilm reactor (MBBR) nitrification rates, nitrifying biofilm morphology, biomass viability as well as bacterial community shifts during long-term exposure to 1 °C. Long-term exposure to 1 °C is the key operational condition for potential ammonia removal upgrade units to numerous northern region treatment systems. The average laboratory MBBR ammonia removal rate after long-term exposure to 1 °C was measured to be 18 ± 5.1% as compared to the average removal rate at 20 °C. Biofilm morphology and specifically the thickness along with biomass viability at various depths in the biofilm were investigated using variable pressure electron scanning microscope (VPSEM) imaging and confocal laser scanning microscope (CLSM) imaging in combination with viability live/dead staining. The biofilm thickness along with the number of viable cells showed significant increases after long-term exposure to 1 °C. Hence, this study observed nitrifying bacteria with higher activities at warm temperatures and a slightly greater quantity of nitrifying bacteria with lower activities at cold temperatures in nitrifying MBBR biofilms. Using DNA sequencing analysis, Nitrosomonas and Nitrosospira (ammonia oxidizers) as well as Nitrospira (nitrite oxidizer) were identified and no population shift was observed between 20 °C and after long-term exposure to 1 °C. [ABSTRACT FROM AUTHOR]

Attached growth biological treatment systems are a promising solution to ammonia removal in cold-temperature climates. Environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy in combination with fluorescent in situ hybridization (FISH) was used to investigate the effects of 4 months of exposure to 4 °C on nitrifying biofilm and biomass. These molecular and microscopic methods were modified to minimize loss of mass and distortion of in situ perspectives. Environmental scanning electron microscopy revealed that nitrifying biofilm did not exhibit significant changes in volume with exposure to 4 °C. Confocal laser scanning microscopy in combination with FISH showed that the number of ammonia-oxidizing bacteria (AOB) cells present in the biofilm was statistically consistent during exposure to 4 °C. The RNA content of AOB cells remained sufficient for FISH enumeration. The number of nitrite-oxidizing bacteria cells remained steady during exposure to 4 °C; however, the RNA content of the cells appeared to decrease with exposure to 4 °C, thereby preventing their enumeration using FISH. Water Environ. Res., 84, 328 (2012). [ABSTRACT FROM AUTHOR]

Abstract: Stormwater biofilters have the ability to remove nutrients from stormwater. Reliable pollutant removal during the cold season is particularly important due to the comparably high contamination levels. However, the removal performance might be negatively affected by low temperatures. A biofilter column study was conducted in thermostat-controlled climate rooms (at 2, 7 and 20°C) to investigate the effect of low temperatures on nutrient removal. Phosphorus and suspended solids removal were significantly correlated and consistently very high (typically in excess of 90% and 95%, respectively, at all temperatures). This is important for the successful implementation of biofilters in cold climates since phosphorus is commonly of principal concern, often being the limiting factor for eutrophication in freshwater ecosystems. Unfortunately, nitrogen removal was poor and leaching was shown, which increased with temperature. The increasing nitrate–nitrogen production rates with temperature were well described by the Arrhenius relationship with temperature coefficients Q 10 in the range which is typically used to describe temperature effects on nitrification. Thus, temperature effects have to be considered when nitrogen removal is targeted and the biofilter might be exposed to cold temperatures. [ABSTRACT FROM AUTHOR]

The rate of nitrification within a laboratory-scale Biological Aerated Filtration treatment system at 4°C was investigated during an exposure time of approximately four months (acclimatized experiments). In addition, shock experiments from 20°C to 4°C and from 4°C to 20°C were performed. The acclimatized experiments demonstrated that the exposure time the system remained at low temperature strongly affects the rates of nitrification. Nevertheless, the experiments showed that significant nitrification rates are maintained for up to 115 days at 4°C. The rate of ammonia removal after an exposure time of 115 days at 4°C was shown to be as high as 16% of the rate of removal observed at 20°C. The 20°C to 4°C shock experiment demonstrated a 56% decrease in the rate of ammonia removal. On the other hand, the 4°C to 20°C shock experiment demonstrated an increase in the relative rates of ammonia removal of up to 300% when compared to rates of removal measured after 115 days at 4°C. Thus, although the rates of nitrification have been shown to decrease significantly as a function of exposure time at 4°C, the process has demonstrated important rates of ammonia removal at 4°C for the approximate span of the North American winter. [ABSTRACT FROM AUTHOR]

Abstract: Though microbial activity is known to occur in frozen soils, little is known about the fate of animal manure N applied in the fall to agricultural soils located in areas with prolonged winter periods. Our objective was to examine transformations of soil and pig slurry N at low temperatures. Loamy and clay soils were either unamended (Control), amended with 15NH4-labeled pig slurry, or amended with the pig slurry and wheat straw. Soils were incubated at −6, −2, 2, 6, and 10 °C. The amounts of NH4, NO3 and microbial biomass N (MBN), and the presence of 15N in these pools were monitored. Total mineral N, NO3 and 15NO3 increased at temperature down to −2 °C in the loam soil and −6 °C in the clay soil, indicating that nitrification and mineralization proceeded in frozen soils. Nitrification and mineralization rates were 1.8–4.9 times higher in the clay than in the loamy soil, especially below freezing point (3.2–4.9), possibly because more unfrozen water remained in the clay than in the loamy soil. Slurry addition increased nitrification rates by 3–14 times at all temperatures, indicating that this process was N-limited even in frozen soils. Straw incorporation caused significant net N immobilization only at temperatures ≥2 °C in both soils; the rates were 1.4–3.4 higher in the loam than in the clay soil. Nevertheless, up to 30% of the applied 15N was present in MBN at all temperatures. These findings indicate that microbial N immobilization occurred in frozen soils, but was not strong enough to induce net immobilization below the freezing point, even in the presence of straw. The Q 10 values for estimated mineralization and nitrification rates were one to two orders-of-magnitude larger below 2 °C than above this temperature (13–208 versus 1.5–6.9, respectively), indicating that these processes are highly sensitive to a small increase in soil temperature around the freezing point of water. This study confirms that net mineralization and nitrification can occur at potentially significant rates in frozen agricultural soils, especially in the presence of organic amendments. In contrast, net N immobilization could be detected essentially above the freezing point. Our results imply that fall-applied N could be at risk of overwinter losses, particularly in fine-textured soils. [Copyright &y& Elsevier]

The communities of Bacteria , Archaea and Fungi in a full-scale moving bed biofilm reactor in Rukatunturi (Ruka, Finland, in the Polar Arctic Circle) were analyzed in order to observe their ecological role in the operation of this system at low temperature. The bioreactor achieved efficient removal performances organic matter (>96%) and for ammonium (>95%), however a modest removal for total nitrogen (>63–75%). Bacteria dominant phylotypes changed in relation to the different functions: Trichococcus and Polaromonas for denitrification, Trichococcus and Simplicispira for organic matter removal, and Devosia and Thermomonas for nitrification. Bacteria predicted metagenome related to nitrification confirmed ammonium oxidation in nitrification chamber, and reduction of nitrate and nitrite in the denitrification and organic matter removal chambers. Dynamics of Fungi , dominated by Trichosporonaceae and Ascomycota clones, were linked to aeration conditions but not to substrate concentrations. Archaea communities, dominated by Methanobrevibacter genus and Thermoplasmatales -related clones, were not affected by aeration or substrate concentrations. The results obtained offer a valuable insight into the ecological role of microbial communities in full-scale moving bed biofilm reactor operating under extremely low temperatures. • Bacteria communities were sensitive to aeration and substrate concentrations. • Fungi communities were sensitive to aeration conditions. • Archaea communities were not affected by aeration and substrate concentrations. • NH 4 + and NO 3 − removal occurred in the nitrification and denitrification chambers. • Top contribution of nosZ and nirK occurred in the organic matter removal chamber. [ABSTRACT FROM AUTHOR]