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• MABRs were exposed to different aeration patterns and scouring frequencies. • Oxygen dynamics were analyzed at different depths during intermittent aeration. • Aeration and scouring had a major impact on the oxygen profiles within the biofilms. • N 2 O emissions differed between the different MABR operation strategies. This study investigated the effects of aeration and scouring strategies on the performance of Membrane Aerated Biofilm Reactors (MABRs) and the distribution of oxygen and nitrous oxide in the biofilm. Four flat sheet MABRs were operated with synthetic feed under different conditions: two with intermittent aeration (iMABR) and two with continuous aeration (cMABR). Scouring was induced by bubbling dinitrogen gas through the reactor bulk at low and high frequencies (LF and HF). In the iMABRs, a partial nitritation biofilm initially developed, but the biofilm adapted to the aeration strategy over time and became nitrifying. The cMABRs directly developed a nitrifying biofilm without a significant phase of partial nitritation. Limiting oxygen availability improved the overall performance with regards to total nitrogen (TN) removal by providing a better environment for anaerobic ammonium oxidation (Anammox) while limiting complete nitrification. Oxygen profiles were measured in the iMABR over time at different biofilms depths, showing that intermittent aeration led to various oxygen concentrations and temporal variations in the oxygen availabilities at different depths of the biofilm. Also, N 2 O emissions from the MABRs differed greatly between the different systems, but still remained lower compared to other reactor configurations for nitrogen removal, making the MABR technology a worthy alternative. The results showed large differences between the operating strategies of the MABRs and can help to gain more insight into the specific properties of MABRs for nitrogen removal. [Display omitted] [ABSTRACT FROM AUTHOR]

Domestic used water treatment systems are currently predominantly based on conventional resource inefficient treatment processes. While resource recovery is gaining momentum it lacks high value end-products which can be efficiently marketed. Microbial protein production offers a valid and promising alternative by upgrading low value recovered resources into high quality feed and also food. In the present study, we evaluated the potential of hydrogen-oxidizing bacteria to upgrade ammonium and carbon dioxide under autotrophic growth conditions. The enrichment of a generic microbial community and the implementation of different culture conditions (sequenced batch resp. continuous reactor) revealed surprising features. At low selection pressure (i.e. under sequenced batch culture at high solid retention time), a very diverse microbiome with an important presence of predatory Bdellovibrio spp. was observed. The microbial culture which evolved under high rate selection pressure (i.e. dilution rate D = 0.1 h −1 ) under continuous reactor conditions was dominated by Sulfuricurvum spp. and a highly stable and efficient process in terms of N and C uptake, biomass yield and volumetric productivity was attained. Under continuous culture conditions the maximum yield obtained was 0.29 g cell dry weight per gram chemical oxygen demand equivalent of hydrogen, whereas the maximum volumetric loading rate peaked 0.41 g cell dry weight per litre per hour at a protein content of 71%. Finally, the microbial protein produced was of high nutritive quality in terms of essential amino acids content and can be a suitable substitute for conventional feed sources such as fishmeal or soybean meal. [ABSTRACT FROM AUTHOR]

The fractionation of nitrogen (as ammonia/ammonium) and phosphorus (as phosphate ions) present in the dairy manure digestate was investigated using a nanofiltration membrane NF270. The filtration and separation efficiencies were correlated to pH across the range 3 < pH < 11. Filtration at pH 11 enabled higher permeate flux of 125–150 LMH at 20 bar, however rejection of ammonia was high at 30–36% and phosphate was 96.4–97.2%. At pH 3 and pH 7, electrostatic charge effects led to higher permeation of ammonium and thus more efficient separation of nitrogen. The rejection of phosphorus was relatively constant at any given pH and determined as 83% at pH 3, 97% at pH 7 and 95% at pH 11. The fractionation of nitrogen and phosphorus from complex aqueous solutions was demonstrated to be highly dependent on the charge of the membrane and ionic speciation. Solutions rich in nitrogen (as ammonia/ammonium) were obtained with almost no phosphorus present (<1 ppm) whilst the purification of the PO 4 –P was achieved by series of diafiltration (DF) operations which further separated the nitrogen. The separation of nutrients benefited from an advantageous membrane process with potential added value for a wide range of industries. The analysis of the process economics for a membrane based plant illustrates that the recovery of nutrients, particularly NH 3 –N, may be commercially feasible when compared to manufactured anhydrous NH 3 . [ABSTRACT FROM AUTHOR]

Inorganic nitrogen species have three states including ammonia nitrogen ( NH 4 + /NH 3 ), nitrite ( NO 2 − ) and nitrate ( NO 3 − ) and are often found in the disinfection system. However, no available literature could be found on their role and fate in photocatalytic disinfection systems. In this study, batch experiments were conducted to investigate bacteria inactivation, H 2 O 2 generated and inorganic nitrogen variation to understand the role and fate of inorganic nitrogen species during UVA/TiO 2 disinfection and evaluate effects of initial pH and bacteria levels on the role and fate. NH 4 + /NH 3 and NO 2 − inhibited the photocatalytic disinfection process obviously. It could be confirmed through that H 2 O 2 yield used for pathogen inactivation was dependent on NH 4 + /NH 3 and NO 2 − levels. The NH 4 + /NH 3 remaining, NH 4 + remaining and NO 3 − yields in only NH 4 + /NH 3 photocatalytic oxidation experiments were obviously different from the corresponding values in the photocatalytic disinfection experiments with NH 4 + /NH 3 , which confirmed that photocatalytic disinfection had an obvious effect on the fate of NH 4 + /NH 3 . However, photocatalytic disinfection had slight effects on the fate of NO 2 − and NO 3 − . Escherischia coli inactivation rate was the highest in neutral solutions (Initial pH 7) while the lowest in alkaline solutions (Initial pH 8.5). The decrease of NH 4 + /NH 3 in alkaline solutions was the most significant. In turn, the photocatalysis of NO 2 − was more evident in acidic solutions. E . coli inactivation was reduced with the increase of initial E . coli concentrations. The initial bacteria concentrations significantly influenced the increase of NH 4 + /NH 3 , NH 4 + and NO 3 − , but slightly impacted the decrease of NO 2 − . [ABSTRACT FROM AUTHOR]

Abstract: Increased popularity of attached-growth wastewater treatment systems (e.g. biological aerated filtration processes—BAF) has created the need for a rapid and reliable method of characterizing biofilms. In addition to the mass of the biofilm that may serve as a control parameter for attached-growth treatment systems, the nitrogen content of the biofilm is also of great interest with increasingly strict nitrogen removal guidelines. Existing methods that may be used to analyse biofilms in such processes involve complex sample preparation and microbiological expertise that limit their application in many biofilm wastewater treatment studies and at existing treatment facilities as a feasible method of monitoring the biofilm. This paper describes a simple technical procedure that enables biofilm samples attached to polystyrene beads to be characterized in terms of the biofilm mass and the nitrogen content of the biofilm. The proposed protocol incorporates an agitation procedure that demonstrates 99.9% removal of the biofilm from polystyrene beads; a modified TSS procedure that measures the removed biofilm mass; and subsequently a modified total Kjeldahl nitrogen (TKN) procedure that enables the nitrogen content of the biofilm to be measured directly on the filter. Moreover, this protocol allows numerous beads to be analysed with limited manipulation and without the loss of critical mass. [Copyright &y& Elsevier]

• Assessment of variation in qPCR analysis of biological nitrogen removal microbiome. • Comparison of qPCR results between labs highlights the limitations with comparability. • The impact of DNA extraction was highest was followed by choice of primers. • The extent of variability between labs depends upon the sample type. • The extent of variability between labs differed for each target microorganism. Quantitative PCR (qPCR) is broadly used as the gold standard to quantify microbial community fractions in environmental microbiology and biotechnology. Benchmarking efforts to ensure the comparability of qPCR data for environmental bioprocesses are still scarce. Also, for partial nitritation/anammox (PN/A) systems systematic investigations are still missing, rendering meta-analysis of reported trends and generic insights potentially precarious. We report a baseline investigation of the variability of qPCR-based analyses for microbial communities applied to PN/A systems. Round-robin testing was performed for three PN/A biomass samples in six laboratories, using the respective in-house DNA extraction and qPCR protocols. The concentration of extracted DNA was significantly different between labs, ranged between 2.7 and 328 ng mg−1 wet biomass. The variability among the qPCR abundance data of different labs was very high (1−7 log fold) but differed for different target microbial guilds. DNA extraction caused maximum variation (3–7 log fold), followed by the primers (1–3 log fold). These insights will guide environmental scientists and engineers as well as treatment plant operators in the interpretation of qPCR data. Image, graphical abstract [ABSTRACT FROM AUTHOR]