Nitric oxide (NO) and nitrous oxide (N2O) emissions from nitrifying ecosystems are a serious threat to the environment. The factors influencing the emission and the responsible microorganisms and ...pathways were studied using a laboratory-scale nitrifying reactor system. The nitrifying culture was established at growth rates relevant to wastewater treatment plants (WWTPs). During stable ammonia oxidation, 0.03% of ammonium was emitted as NO and 2.8% was emitted as N2O. Although mixed cultures were used, clear responses in emission of ammonia oxidizing bacteria (AOB) could be detected and it was concluded that the denitrification pathway of AOB was the main source of the emissions. Emissions of nitrogen oxides in the system were strongly influenced by oxygen, nitrite, and ammonium concentrations. Steady state emission levels greatly underestimate the total emission, because changes in oxygen, nitrite, and ammonium concentrations induced a dramatic rise in NO and N2O emission. The data presented can be used as an indication for NO and N2O emission by AOB in plug-flow activated sludge systems, which is highly relevant because of the atmospheric impact and potential health risk of these compounds.
In this study we investigated the feasibility of producing polyhydroxyalkanoate (PHA) by microbial enrichments on paper mill wastewater. The complete process includes (1) paper mill wastewater ...acidogenic fermentation in a simple batch process, (2) enrichment of a PHA-producing microbial community in a selector operated in sequencing batch mode with feast-famine regime, (3) Cellular PHA content maximization of the enrichment in an accumulator in fed-batch mode. The selective pressure required to establish a PHA-producing microbial enrichment, as derived from our previous research on synthetic medium, was validated using an agro-industrial waste stream in this study. The microbial enrichment obtained could accumulate maximum up to 77% PHA of cell dry weight within 5 h, which is currently the best result obtained on real agro-industrial waste streams, especially in terms of biomass specific efficiency. Biomass in this enrichment included both Plasticicumulans acidivorans, which was the main PHA producer, and a flanking population, which exhibited limited PHA-producing capacity. The fraction of P. acidivorans in the biomass was largely dependent on the fraction of volatile fatty acids in the total soluble COD in the wastewater after acidification. Based on this observation, one simple equation was proposed for predicting the PHA storage capacity of the enrichment. Moreover, some crucial bottlenecks that may impede the successful scaling-up of the process are discussed.
► We obtain one enrichment with high PHA-producing capacity on paper wastewater. ► We find acidification is the crucial step in the PHA-producing process. ► We find PHA-producers play a major role in the overall PHA content in biomass. ► We prove PHA-producing process can be integrated with wastewater treatment.
Microplastics have aroused increasing concern as they pose threats to aquatic species as well as human beings. They do not only contribute to accumulation of plastics in the environment, but due to ...absorption they can also contribute to spreading of micropollutants in the environment. Studies indicated that wastewater treatment plants (WWTPs) play an important role in releasing microplastics to the environment. Therefore, effective detection of the microplastics and understanding their occurrence and fate in WWTPs are of great importance towards microplastics control. In this review, the up-to-date status on the detection, occurrence and removal of microplastics in WWTPs are comprehensively reviewed. Specifically, the different techniques used for collecting microplastics from both wastewater and sewage sludge, and their pretreatment and characterization methods are reviewed and analyzed. The key aspects regarding microplastics occurrence in WWTPs, such as concentrations, total discharges, materials, shapes and sizes are summarized and compared. Microplastics removal in different treatment stages and their retention in sewage sludge are explored. The development of potential microplastics-targeted treatment technologies is also presented. Although previous researches in microplastics have undoubtedly improved our level of understanding, it is clear that much remains to be learned about microplastics in WWTPs, as many unanswered questions and thereby concerns still remain; some of these important future research areas are outlined. The key challenges appear to be to harmonize detection methods as well as microplastics mitigation from wastewater and sewage sludge.
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•The detection, occurrence and behavior of microplastics in WWTPs are reviewed.•The collection, pretreatment and characterization of microplastics are analyzed.•The concentrations, materials and properties of microplastics are summarized.•The microplastics removal in WWTPs and retention in sewage sludge are explored.
This model-based study investigated the mechanisms and operational window for efficient repression of nitrite oxidizing bacteria (NOB) in an autotrophic nitrogen removal process. The operation of a ...continuous single-stage granular sludge process was simulated for nitrogen removal from pretreated sewage at 10 °C. The effects of the residual ammonium concentration were explicitly analyzed with the model. Competition for oxygen between ammonia-oxidizing bacteria (AOB) and NOB was found to be essential for NOB repression even when the suppression of nitrite oxidation is assisted by nitrite reduction by anammox (AMX). The nitrite half-saturation coefficient of NOB and AMX proved non-sensitive for the model output. The maximum specific growth rate of AMX bacteria proved a sensitive process parameter, because higher rates would provide a competitive advantage for AMX.
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•Residual ammonium triggers effective nitrite-oxidizing bacteria (NOB) repression.•NOB repression is due to oxygen competition with ammonia-oxidizing bacteria.•KO2,NOB/KO2,AOB ratio was found to be the most critical factor for NOB repression.•Anammox doubling time proved to be a sensitive parameter for NOB repression.
In this study, we investigated during 400 days the microbial community variations as observed from 16S DNA gene DGGE banding patterns from an aerobic granular sludge pilot plant as well as the from a ...full-scale activated sludge treatment plant in Epe, the Netherlands. Both plants obtained the same wastewater and had the same relative hydraulic variations and run stable over time. For the total bacterial population, a similarity analysis was conducted showing that the community composition of both sludge types was very dissimilar. Despite this difference, general bacterial population of both systems had on average comparable species richness, entropy, and evenness, suggesting that different bacteria were sharing the same functionality. Moreover, multi-dimensional scaling analysis revealed that the microbial populations of the flocculent sludge system moved closely around the initial population, whereas the bacterial population in the aerobic granular sludge moved away from its initial population representing a permanent change. In addition, the ammonium-oxidizing community of both sludge systems was studied in detail showing more unevenness than the general bacterial community.
Nitrosomonas
was the dominant AOB in flocculent sludge, whereas in granular sludge,
Nitrosomonas
and
Nitrosospira
were present in equal amounts. A correlation analysis of process data and microbial data from DGGE gels showed that the microbial diversity shift in ammonium-oxidizing bacteria clearly correlated with fluctuations in temperature.
Biogrouting is a biological ground improvement method, in which microorganisms are used to induce carbonate precipitation in the subsurface in order to increase the strength and stiffness of granular ...soils. In this paper the results of a large-scale experiment
(
100
m3
)
are presented, in which the feasibility of biogrouting as a ground improvement method is investigated using techniques and equipment similar to those used in potential applications. In situ geophysical measurements were used to monitor the biogrouting process during treatment and indicated that the stiffness had increased significantly after one day of treatment. The results of unconfined compressive strength tests on samples which were excavated after treatment were used to assess the distribution of mechanical properties throughout the cemented sand body, which correlated quite well with the results of the in situ geophysical measurements. The stiffness increase could be quantified as a function of the injected volume of grouting agents and the distance from the injection points. These results will serve as an important benchmark for future applications of biomediated ground improvement.
Particulate and slowly biodegradable substrates form an important fraction of industrial wastewater and sewage. To study the influence of suspended solids and colloidal substrate on the morphology ...and performance of aerobic granular sludge, suspended and soluble starch was used as a model substrate. Degradation was studied using microscopy, micro-electrode measurements, batch experiments and long term laboratory scale reactor operation. Starch was removed by adsorption at the granule surface, followed by hydrolysis and consumption of the hydrolyzed products. Aerobic granules could be maintained on starch as sole influent carbon source, but their structure was filamentous and irregular. It is hypothesized that this is related to the low starch hydrolysis rates, leading to available substrate during the aeration period (extended feast period) and resulting in increased substrate gradients over the granules. The latter induces a less uniform granule development. Starch adsorbed and was consumed at the granule surface instead of being accumulated inside the granules as occurs for soluble substrates. Therefore the simultaneous denitrification efficiencies remained low. Moreover, many protozoa and metazoans were observed in laboratory reactors as well as in pilot- and full-scale Nereda
® reactors, indicating an important role in the removal of suspended solids too.
Anammox (anaerobic ammonium oxidation) bacteria are important for the nitrogen cycle in both natural environments and wastewater treatment plants. These bacteria have a strong tendency to grow in ...aggregates like biofilms and granular sludge. To understand the formation of anammox aggregates, it is required to unravel the composition of the extracellular polymeric substances (EPS), which are produced by the bacteria to develop into aggregates and granules. Here, we investigated anionic polymers in anammox granular sludge, focussing on sialic acids and sulfated glycosaminoglycans. Quantification assays and fluorescent stains indicated that sialic acids and sulfated glycosaminoglycans were present in the anammox EPS (1.6% equivalents of sialic acids and 2.4% equivalents of sulfated glycosaminoglycans). Additionally, the potential genes for the biosynthesis of sialic acids and sulfated glycosaminoglycans were analyzed in the anammox draft genomes. The finding of these components in anammox granular sludge and previously in other nonpathogenic bacteria pointed out that sialic acids and sulfated glycosaminoglycans are worth investigating in the context of a broader function in microbial communities and biofilm systems in general.
Anammox Growth on Pretreated Municipal Wastewater Lotti, Tommaso; Kleerebezem, Robbert; van Erp Taalman Kip, Charlotte ...
Environmental science & technology,
07/2014, Letnik:
48, Številka:
14
Journal Article
Recenzirano
Autotrophic nitrogen removal from municipal wastewater enables development of energy autarkic wastewater treatment plants. In this study we report the evaluation of the anammox process in a granular ...sludge fluidized bed lab-scale reactor continuously fed with the actual effluent of the A-stage of the WWTP of Dokhaven, Rotterdam. The reactor was anoxic, and nitrite was dosed continuously to support anammox activity only. The system was operated for more than ten months at temperatures between 20 and 10 °C. COD was also consumed during the process, but heterotrophs could not outcompete anammox bacteria. Volumetric N-removal rates obtained were comparable or higher than those of conventional N-removal systems, with values higher than 0.4 g-N L–1 d–1 when operated at 10 °C. The biomass specific N-removal rate at 10 °C was on average 50 ± 7 mg-N g-VSS–1 d–1 during the last month of operations, almost two times higher than previously reported activities at this temperature. FISH analysis revealed that the dominant anammox species was Candidatus Brocadia Fulgida throughout the experimentation. Evidence for growth of anammox bacteria at mainstream conditions was demonstrated for the entire temperature range tested (10–20 °C), and new granules were shown to be actively formed and efficiently retained in the system.
The influence of different carbon sources (acetate to propionate ratios), temperature and pH levels on the competition between polyphosphate- and glycogen-accumulating organisms (PAO and GAO, ...respectively) was evaluated using a metabolic model that incorporated the carbon source, temperature and pH dependences of these microorganisms. The model satisfactorily described the bacterial activity of PAO (
Accumulibacter) and GAO (
Competibacter and
Alphaproteobacteria-GAO) laboratory-enriched cultures cultivated on propionate (HPr) and acetate (HAc) at standard conditions (20
°C and pH 7.0). Using the calibrated model, the effects of different influent HAc to HPr ratios (100–0, 75–25, 50–50 and 0–100%), temperatures (10, 20 and 30
°C) and pH levels (6.0, 7.0 and 7.5) on the competition among
Accumulibacter,
Competibacter and
Alphaproteobacteria-GAO were evaluated. The main aim was to assess which conditions were favorable for the existence of PAO and, therefore, beneficial for the biological phosphorus removal process in sewage treatment plants. At low temperature (10
°C), PAO were the dominant microorganisms regardless of the used influent carbon source or pH. At moderate temperature (20
°C), PAO dominated the competition when HAc and HPr were simultaneously supplied (75–25 and 50–50% HAc to HPr ratios). However, the use of either HAc or HPr as sole carbon source at 20
°C was not favorable for PAO unless a high pH was used (7.5). Meanwhile, at higher temperature (30
°C), GAO tended to be the dominant microorganisms. Nevertheless, the combined presence of acetate and propionate in the influent (75–25 and 50–50% HAc to HPr ratios) as well as a high pH (7.5) appear to be potential factors to favor the metabolism of PAO over GAO at higher sewage temperature (30
°C).
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