Elzbieta Plaza

Structure and composition of biofilm communities in a moving bed biofilm reactor for nitritation-anammox at low temperatures.

It is a challenge to apply anaerobic ammonium oxidation (anammox) for nitrogen removal from wastewater at low temperatures. Maintenance of anammox- and aerobic ammonia oxidizing bacteria (AOB) and suppression of nitrite oxidizing bacteria (NOB) are key issues. In this work, a nitritation-anammox moving bed biofilm pilot reactor was operated at 19-10°C for 300 d. Nitrogen removal was decreasing, but stable, at 19-13°C. At 10°C removal became unstable. Quantitative PCR, fluorescence in situ hybridization and gene sequencing showed that no major microbial community changes were observed with decreased temperature. Anammox bacteria dominated the biofilm (0.9-1.2 × 10(14) 16S rRNA copies m(-2)). Most anammox bacteria were similar to Brocadia sp. 40, but another smaller Brocadia population was present near the biofilm-water interface, where also the AOB community (Nitrosomonas) was concentrated in thin layers (1.8-5.3 × 10(12) amoA copies m(-2)). NOB (Nitrobacter, Nitrospira) were always present at low concentrations (<1.3 × 10(11) 16S rRNA copies m(-2)).

Mainstream wastewater treatment in integrated fixed film activated sludge (IFAS) reactor by partial nitritation/anammox process

In this study the system based on the combination of biofilm and activated sludge (IFAS - integrated fixed film activated sludge) was tested and compared with a system that relies only on biofilm (MBBR - moving bed biofilm reactor) for nitrogen removal from municipal wastewater by deammonification process. By introduction of suspended biomass into MBBR the nitrogen removal efficiency increased from 36 ± 3% to 70 ± 4% with simultaneous 3-fold increase of nitrogen removal rate. Results of batch tests and continuous reactor operation showed that organotrophic nitrate reduction to nitrite, followed by anammox reaction contributed to this high removal efficiency. After sCOD/NH4-N ratio decreased from 1.8 ± 0.2 to 1.3 ± 0.1 removal efficiency decreased to 52 ± 4%, while still maintaining 150% higher removal rate, comparing to MBBR. Activity tests revealed that affinity of NOB to oxygen is higher than affinity of AOB with half-saturation constants of 0.05 and 0.41 mg/L, respectively.

Combination of upflow anaerobic sludge blanket (UASB) reactor and partial nitritation/anammox moving bed biofilm reactor (MBBR) for municipal wastewater treatment

In this study the combination of an upflow anaerobic sludge blanket (UASB) reactor and a deammonification moving bed biofilm reactor (MBBR) for mainstream wastewater treatment was tested. The competition between aerobic ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) was studied during a 5months period of transition from reject water to mainstream wastewater followed by a 16months period of mainstream wastewater treatment. The decrease of influent ammonium concentration led to a wash-out of suspended biomass which had a major contribution to nitrite production. Influence of a dissolved oxygen concentration and a transient anoxia mechanism of NOB suppression were studied. It was shown that anoxic phase duration has no effect on NOB metabolism recovery and oxygen diffusion rather than affinities of AOB and NOB to oxygen determine the rate of nitrogen conversion in a biofilm system. Anammox activity remained on the level comparable to reject water treatment systems.

Microbial adaptation, process performance and a suggested control strategy in a pre-denitrifying system with ethanol dosage

Biological nitrogen removal in activated sludge processes is dependent on sufficient supplies of easily metabolized carbon compounds for the denitrifying bacterial population. An external carbon source can increase denitrification rates and compensate for deficiencies in the influent C/N ratio. Plant performance and microbial adaptation were studied in a pre-denitrifying pilot-scale activated sludge plant with and without ethanol. Total nitrogen removal efficiency was 67 and 35% for the ethanol and reference line, respectively. The process responded rapidly to ethanol but one sludge age was necessary for full bacterial adaptation. An initial rapid increase suggests enzyme induction rather than alterations in bacterial species composition. Increased enzyme activity was explained by an increase in turn-over rate of biomass. Low effluent nitrate concentration was a result of the simultaneous use of influent COD and ethanol. Fluctuations in influent COD did not affect denitrification capacity with ethanol. Sludge settling properties were moderately better in the process without ethanol addition. An automatic control strategy for carbon dosage using feedforward from influent carbon and nitrate in the recirculated flow was simulated. Simulations with an adaptive linear quadratic controller demonstrated that the desired nitrate concentration at the end of the anoxic zone could be maintained despite relatively large disturbances.

Evaluation of deammonification process performance at different aeration strategies.

In a deammonification process applied in the moving bed biofilm reactor (MBBR) oxygen is a crucial parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterised by the ratio between non-aerated and aerated phase times (R) and dissolved oxygen concentrations (DO). The series of batch tests were conducted with variable DO concentrations (2, 3, 4 mg L(-1)) and R values (0-continuous aeration; 1/3, 1, 3-intermittent aeration) but with the same initial ammonium concentration, volume of the moving bed and temperature. It was found that the impact of DO on deammonification was dependent on the R value. At R=0 and R=1/3, an increase of DO caused a significant increase in nitrogen removal rate, whereas for R=1 and R=3 similar rates of the process were observed irrespectively of the DO. The highest nitrogen removal rate of 3.33 g N m(-2) d(-1) (efficiency equal to 69.5%) was obtained at R=1/3 and DO=4 mg L(-1). Significantly lower nitrogen removal rates (1.17-1.58 g N m(-2) d(-1)) were observed at R=1 and R=3 for each examined DO. It was a consequence reduced aerated phase duration times and lesser amounts of residual nitrite in non-aerated phases as compared to R=1/3.

N2O emissions from a one stage partial nitrification/anammox process in moving bed biofilm reactors.

Nitrous oxide (N2O) emissions from wastewater treatment are getting increased attention because their global warming potential is around 300 times that of carbon dioxide. The aim of the study was to measure nitrous oxide emissions from one stage partial nitrification/anammox (Anaerobic Ammonium Oxidation) reactors, where nitrogen is removed in a biological way. The first part of the experimental study was focused on the measurements of nitrous oxide emissions from two pilot scale reactors in the long term; one reactor with intermittent aeration at 25 °C and the other reactor with continuous aeration at 22-23 °C. The second part of the experiment was done to evaluate the influence of different nitrogen loads and aeration strategies, described by the ratio between the non-aerated and aerated phase and the dissolved oxygen concentrations, on nitrous oxide emissions from the process. The study showed that 0.4-2% of the nitrogen load was converted into nitrous oxide from two reactors. With higher nitrogen load, the amount of nitrous oxide emission was also higher. A larger fraction of nitrous oxide was emitted to the gas phase while less was emitted with the liquid effluent. It was also found that nitrous oxide emissions were similar under intermittent and continuous aeration.

Ammonium removal by partial nitritation and Anammox processes from wastewater with increased salinity

This work is dedicated to the biological treatment of wastewater with increased salinity using a combination of partial nitritation and Anammox processes. Two one-stage deammonification moving bed biofilm reactors were operated with the increase in NaCl concentration every two weeks by 5 and 2.5 g/L. The strategy with a step of 5 g/L of salinity increase led to complete inhibition of the process at the salinity level of 15 g/L. The strategy with a step of 2.5 g/L gave possibility to adapt bacteria to the elevated salinity. After reaching the salinity level of 10 g NaCl/L, the reactor was operated during 92 days with a nitrogen removal rate of 0.39 ± 0.19 g N/(m2·day) (0.078 ± 0.038 kg N/m3·day) and an average nitrogen removal efficiency of 59%. It was shown that conductivity cannot be used for monitoring the process when a reactor is treating wastewater with increased salinity, whereas pH can be correlated to effluent ammonium concentration regardless of wastewater salinity.

Community structure of partial nitritation‐anammox biofilms at decreasing substrate concentrations and low temperature

Partial nitritation‐anammox (PNA) permits energy effective nitrogen removal. Today PNA is used for treatment of concentrated and warm side streams at wastewater treatment plants, but not the more diluted and colder main stream. To implement PNA in the main stream, better knowledge about microbial communities at the typical environmental conditions is necessary. In order to investigate the response of PNA microbial communities to decreasing substrate availability, we have operated a moving bed biofilm reactor (MBBR) at decreasing reactor concentrations (311–27 mg‐N l−1 of ammonium) and low temperature (13°C) for 302 days and investigated the biofilm community using high throughput amplicon sequencing; quantitative PCR; and fluorescence in situ hybridization. The anammox bacteria (Ca. Brocadia) constituted a large fraction of the biomass with fewer aerobic ammonia oxidizing bacteria (AOB) and even less nitrite oxidizing bacteria (NOB; Nitrotoga, Nitrospira and Nitrobacter). Still, NOB had considerable impact on the process performance. The anammox bacteria, AOB and NOB all harboured more than one population, indicating some diversity, and the heterotrophic bacterial community was diverse (seven phyla). Despite the downshifts in substrate availability, changes in the relative abundance and composition of anammox bacteria, AOB and NOB were small and also the heterotrophic community showed little changes in composition. This indicates stability of PNA MBBR communities towards decreasing substrate availability and suggests that even heterotrophic bacteria are integral components of these communities.

Combination of ion exchange and partial nitritation/Anammox process for ammonium removal from mainstream municipal wastewater

In this study, a new technology of nitrogen removal from mainstream municipal wastewater is proposed. It is based on ammonium removal by ion exchange and regeneration of ion exchange material with 10-30 g/L NaCl solution with further nitrogen removal from spent regenerant by partial nitritation/Anammox process. Influence of regenerant strength on performance of ion exchange and biological parts of the proposed technology was evaluated. Moreover, the technology was tested in batch mode using pretreated municipal wastewater, strong acid cation (SAC) resin and partial nitritation/Anammox biomass. It was shown that with ion exchange it is possible to remove 99.9% of ammonium from wastewater while increasing the concentration of ammonium in spent regenerant by 18 times. Up to 95% of nitrogen from spent regenerant, produced by regeneration of SAC resin with 10 g/L NaCl solution, was removed biologically by partial nitritation/Anammox biomass. Moreover, the possibilities of integration of the technology into municipal wastewater treatment technology, and the challenges and advantages are discussed.

Horizontal Flow Filtration Bed: Impact on Removal of Natural Organic Matter and Iron Co-Existing in Water Source

Removal of natural organic matter and iron co-existing in water source is a challenge and a major problem in the developing world where the most commonly applied process in water treatment is pre-chlorination which results in early formation chlorinated by-products. Results from this study proved that horizontal roughing filter system with natural pumice is a promising option for pre-treatment of such waters. The filter recorded average reductions of total and ferrous iron of 39% and 89%, respectively, and trihalomethanes formation potential of 35% after 1 hour and 29% after 6 hours along the filter. Further reductions of 49% and 61% were achieved when the pretreated water was subjected to coagulation.