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Polyhydroxyalkanoate (PHA) production has been the focus of considerable research to increase productivities and reduce production costs. In this study, a fermented confectionary industry wastewater was used as feedstock for mixed microbial culture PHA production. The feedstock was dominated by lactate and ethanol (60-90 % of all soluble fermentation products). The culture selection reactor was inoculated with municipal activated sludge and was operated at an organic loading rate (OLR) of 100 Cmmol·L

Glycogen-accumulating organisms (GAOs) have been previously observed to be more competitive in anaerobic volatile fatty acid (VFA) uptake as compared to polyphosphate-accumulating organisms (PAOs) at high temperatures in enhanced biological phosphorus removal (EBPR) systems. However, previous evidence regarding the impact of temperature on GAOs has exclusively focused on Competibacter. Defluviicoccus vanus GAOs (DvGAOs) make up another very important GAO group and have been found in EBPR plants; however, their competitiveness at high temperature for anaerobic VFA uptake was previously unknown. The rate of uptake of VFAs by both DvGAOs reactors enriched with acetate or propionate was much lower than those of Candidatus Accumulibacter phosphatis PAOs operated under similar conditions, showing that PAOs displayed a competitive advantage at high temperature, unlike previous observations with Competibacter. This study provides new insight into our understanding of GAOs in EBPR processes, where the impact of temperature on PAO-GAO competition is highly dependent on the phylogenetic identity of the GAO present in the system. New strategies for promoting EBPR performance at high temperatures are proposed on the basis of the results of this work.

Polyphosphate (polyP) accumulating organisms (PAOs) are the key agent to perform enhanced biological phosphorus removal (EBPR) activity, and intracellular polyP plays a key role in this process. Potential associations between EBPR performance and the polyP structure have been suggested, but are yet to be extensively investigated, mainly due to the lack of established methods for polyP characterization in the EBPR system. In this study, we explored and demonstrated that single-cell Raman spectroscopy (SCRS) can be employed for characterizing intracellular polyPs of PAOs in complex environmental samples such as EBPR systems. The results, for the first time, revealed distinct distribution patterns of polyP length (as Raman peak position) in PAOs in lab-scale EBPR reactors that were dominated with different PAO types, as well as among different full-scale EBPR systems with varying configurations. Furthermore, SCRS revealed distinctive polyP composition/features among PAO phenotypic sub-groups, which are likely associated with phylogenetic and/or phenotypic diversity in EBPR communities, highlighting the possible resolving power of SCRS at the microdiversity level. To validate the observed polyP length variations via SCRS, we also performed and compared bulk polyP length characteristics in EBPR biomass using conventional polyacrylamide gel electrophoresis (PAGE) and solution 31P nuclear magnetic resonance (31P-NMR) methods. The results are consistent with the SCRS findings and confirmed the variations in the polyP lengths among different EBPR systems. Compared to conventional methods, SCRS exhibited advantages as compared to conventional methods, including the ability to characterize in situ the intracellular polyPs at subcellular resolution in a label-free and non-destructive way, and the capability to capture subtle and detailed biochemical fingerprints of cells for phenotypic classification. SCRS also has recognized limitations in comparison with 31P-NMR and PAGE, such as the inability to quantitatively detect the average polyP chain length and its distribution. The results provided initial evidence for the potential of SCRS-enabled polyP characterization as an alternative and complementary microbial community phenotyping method to facilitate the phenotype-function (performance) relationship deduction in EBPR systems.

Mixed culture anaerobic processes are important to environmental systems, including the global carbon cycle, and industrial and environmental biotechnology. Mixed culture metabolic modelling (MM) is an essential tool to analyse these systems. MM predicts microbial function based on knowledge or assumption of cellular metabolism. It may be developed based on observations at the process level - biochemical process modelling (BPM) or fundamental knowledge of the cell being modelled - cellular level modelling (CLM). There is a substantial gap between these two fields, with BPM not considering genetic constraints, particularly where this may be important to interspecies interactions (e.g. amino acid transfer), and CLM commonly not considering mass transfer principles, such as advection/diffusion/migration. No unified approach is useful for all applications, but there is an increasing need to consider genetic information and constraints in developing BPM, and translate BPM principles (including mass-transfer and inorganic chemistry) for application to CLM.

Advanced real time – Instrumentation, Control, and Automation (Art-ICA) controllers are an advanced control solution for biological nutrient removal wastewater treatment plants. Art-ICA has been previously shown to be capable of enhancing nutrient removal performance in BNR plants, at lower energy expenditures. However, the impact that this control solution has on the greenhouse gas emissions from full-scale wastewater treatment plants has not previously been addressed. This work addresses the effect of art-ICA on the performance, energy consumption and greenhouse gas emissions of two full-scale WWTPs, Chelas and Castelo Branco (Portugal). The raw wastewater, nitrous oxide emissions, energy consumption and water discharges were quantified in two independent trains operated under different operational modes, conventional operation and art-ICA control. The implementation of the art-ICA strategy improved the effluent quality and reduced the operational costs, resulting in a better performance of these WWTPs. The art-ICA controllers activation led to a reduction of 54% and 7–10% of the total nitrogen effluent and in the specific energy consumption, respectively. Moreover, process control with art-ICA did not have a negative impact on the N2O emissions of the plants, and contributed to lower global warming potential by the facilities. The lower indirect carbon dioxide production due to lower energy consumption contributes to the observation that art-ICA control is environmentally preferable to conventional control.

Diclofenac is a pharmaceutical active compound frequently detected in wastewater and water bodies, and often reported to be persistent and difficult to biodegrade. While many previous studies have focussed on assessing diclofenac biodegradation in nitrification and denitrification processes, this study focusses on diclofenac biodegradation in the enhanced biological phosphorus removal (EBPR) process, where the efficiency of this process for diclofenac biodegradation as well as the metabolites generated are not well understood. An enrichment of Accumulibacter polyphosphate accumulating organisms (PAOs) was operated in an SBR for over 300 d, and acclimatized to 20 μg/L of diclofenac, which is in a similar range to that observed in domestic wastewater influents. The diclofenac biotransformation was monitored in four periods of stable operation and linked to the microbial community and metabolic behaviour in each period. Nitrification was observed in two of the four periods despite the addition of a nitrification inhibitor, and these periods were positively correlated with increased diclofenac biodegradation. Interestingly, in two periods with excellent phosphorus removal (>99%) and no nitrification, different levels of diclofenac biotransformation were observed. Period 2, enriched in Accumulibacter Type II achieved more significant diclofenac biotransformation (3.4 μg/gX), while period 4, enriched in Accumulibacter Type I achieved lower diclofenac biotransformation (0.4 μg/gX). In total, 23 transformation products were identified, with lower toxicity than the parent compound, enabling the elucidation of multiple metabolic pathways for diclofenac biotransformation. This study showed that PAOs can contribute to diclofenac biotransformation, yielding less toxic transformation products, and can complement the biodegradation carried out by other organisms in activated sludge, particularly nitrifiers.

Nitrous oxide (N2O) is a powerful greenhouse gas (GHG) whose production and emission must be minimised from wastewater treatment plants (WWTPs) to avoid undesirable impacts to climate change and the ozone layer. WWTPs operated in tourist regions undergo large seasonal changes to the influent loading rates of organic matter, nitrogen and phosphorus, which operators must respond to by changing their operational conditions. This study examines the impact of a change in low to high season on the N2O emissions of an activated sludge WWTP in a well-known tourist region in the Algarve, Portugal. While literature studies have suggested that increases in the nitrogen and organic loading rates can promote increased N2O emissions, we have found higher N2O emissions in the low season (7.4% kgN2O-N·kgNH4-N−1), where these loading rates were lower. It was found that the impact of accompanying operational changes to the WWTP outweighed any change caused by the increased loading rate, where the aeration rate showed a significant correlation with N2O emission dynamics. The location of the N2O fluxes observed as well as the dissolved vs gaseous N2O levels suggested that the hydroxylamine oxidation pathway was likely to be of higher relevance towards N2O production as compared to nitrifier denitrification. This study contributes towards the understanding of operational factors impacting N2O emissions at full-scale WWTPs and potential mitigation strategies.

UIDP/04378/2020 UIDB/04378/2020 LA/P/0140/2020 SFRH/BD/110673/2015 The production of polyhydroxyalkanoates (PHA) by mixed microbial cultures (MMC) has been studied as an alternative to pure cultures in order to reduce the price of PHA through use of open systems and low-cost substrates, such as agro-industrial sub-products. However, the widespread applicability of this process depends on the optimization of operational factors impacting PHA productivity. This study addresses the impact of biomass withdrawal strategy on the performance of MMC selection reactors and consequently on biomass productivity and global PHA productivity. Two selection reactors were operated in parallel under similar conditions, except for the timing of biomass withdrawal, at the end of the famine phase (Reactor 1, R1) versus at the end of the feast phase (Reactor 2, R2) at an organic loading rate of 100 Cmmol.L−1.d−1 and solids retention time of 4 days. The biomass selected in both conditions had similar PHA storing capacity as shown by the similar yields of PHA per substrate obtained in the accumulation assays; however, R1 reached a higher biomass productivity (about 4-fold higher than R2). This study demonstrated that removing the excess biomass at the end of the famine phase resulted in a much higher global PHA productivity and that the key parameter affecting the global PHA productivity of the 2-stage system was the volumetric biomass productivity. Results obtained provide important insight into how MMC systems can be best operated to maximize PHA productivity. publishersversion published

Conventional wastewater treatment technologies for biological nutrient removal (BNR) are highly dependent on aeration for oxygen supply, which represents a major operational cost of the process. Recently, phototrophic enhanced biological phosphorus removal (photo-EBPR) has been suggested as an alternative system for phosphorus removal, based on a consortium of photosynthetic microorganisms and chemotrophic bacteria, eliminating the need for costly aeration. However, wastewater treatment plants must couple nitrogen and phosphorus removal to achieve discharge limits. For this reason, a new microalgae-bacterial based system for phosphorus and nitrogen removal is proposed in this work. The photo-BNR system studied here consists of a sequencing batch reactor operated with dark anaerobic, light aerobic, dark anoxic and idle periods, to allow both N and P removal. Results of the study show that the photo-BNR system was able to remove 100% of the 40 mg N/L of ammonia fed to the reactor and 94 ± 3% of the total nitrogen (Influent COD:N ratio of 300:40, similar to domestic wastewater). Moreover, an average of 25 ± 9.2 mg P/L was simultaneously removed in the photo-BNR tests, representing the P removal capacity of this system, which exceeds the level of P removal required from typical domestic wastewater. Full ammonia removal was achieved during the light phase, with 67 ± 5% of this ammonia being assimilated by the microbial culture and the remaining 33 ± 5% being converted into nitrate. The assimilated P corresponded to 2.8 ± 0.23 mg P/L, which only represented, approximately, 1/9 of the P removal capacity of the system. Half of the nitrified ammonia was subsequently denitrified during the dark anoxic phase (50 ± 24%). Overall, the photo-BNR system represents the first treatment alternative for N and P from domestic wastewater with no need of mechanical aeration or supplemental carbon addition, representing an alternative low-energy technology of interest.

Phototrophic mixed cultures (PMC) have been found to be a promising technology to produce polyhydroxyalkanoates (PHA), however, work performed thus far has focussed mainly on the use of synthetic feedstocks and operational conditions that differ from those expectable in full-scale processes. The goals of this work were to study, for the first time, the capability of PMCs to produce PHA using real fermented domestic wastewater as feedstock under mixing/light/temperature conditions that are naturally found in outdoor open systems. Various operational strategies were evaluated in this study to increase PHA productivity, namely the poly(3-hydroxybutyric-co-3-hydroxyvaleric) copolymer (PHBV) by PMC systems. Two lab-scale photobioreactors were operated in parallel, with transient illumination (12 h light/12 h dark) and subjected to feedstock fluctuations under two culture selection strategies that best suit the oxidative conditions of high rate algal ponds (HRAPs) which are commonly applied in wastewater treatment plants (WWTP). Under a permanent carbon feast regime (selection strategy 1), the PMC became highly enriched in phototrophic purple bacteria (PPB), and two complementary conditions that can improve the selection of PHA accumulating bacteria were discovered: phosphate cycling, where 20% PHA/VSS (86HB:14HV in a C-mol basis) with a light phase productivity of 0.23 g PHA/L•d_light phase was attained; and transitioning from selection under low organic loading rate (OLR) to high OLR where 17.6% PHA/VSS (60HB:40HV in C base) with a light phase productivity of 0.18 g PHA/L•d_light phase was achieved. Under a feast and famine regime (selection strategy 2), a PMC consortium of microalgae and PPB was obtained, and a multiple pulse feeding strategy during the first hours of the light phase in the selector reactor led to a 26.1% PHA/VSS (36HB:64HV in C base) content, with a productivity of 0.26 g PHA/L•d_light phase and 0.52 g PHA/L•d_feast phase. An accumulation test under higher light intensity led to 30.8% PHA/VSS (85HB:15HV on a C-mol basis) with a productivity of 2.67 g PHA/L•d, along the 8 h of accumulation.

Accumulibacter is a well-known group of organisms, typically considered to be polyphosphate accumulating organisms (PAOs), but potentially capable of glycogen accumulating organism (GAO) metabolism under limiting influent phosphate levels. Metabolic features of Accumulibacter are typically linked to its phylogenetic identity at the Type or clade level, though it is unclear the extent to which Accumulibacter diversity can correlate with its capacity to perform P removal. This paper investigates the fine-scale diversity of Accumulibacter and its link with enhanced biological phosphorus removal (EBPR) performance under various operating conditions, to understand the conditions and community structure leading to successful and unsuccessful EBPR operation. For this purpose, the organic carbon feeding rate and total organic carbon concentration were varied during three distinct operational periods, where influent phosphate was never limiting. Accumulibacter was always the dominant microbial group (80% of all bacteria according to quantitative fluorescence in situ hybridisation - FISH) and low levels of Competibacter and other GAOs were consistently observed (15% of all bacteria). Steady state was achieved in each of the three periods, with average phosphorus removal levels of 36%, 99% and99%, respectively. Experimentally determined stoichiometric activity supported the expression of a mixed PAO/GAO metabolism in the first steady state period and the typical PAO metabolism in the other two steady state periods. FISH quantification and amplicon sequencing of the polyphosphate kinase (ppk1) functional gene indicated that Accumulibacter clade IIC was selected in the first steady state period, which shifted to clade IA after decreasing the carbon feeding rate in steady state period 2, and finally shifted back to clade IIC in the third steady state period. Fine-resolution Ppk-based phylogenetic analysis revealed three different clusters within Accumulibacter clade IIC, where clusters IICii and IICiii were linked to poor EBPR performance in period 1, and cluster IICi was linked to good EBPR performance in period 3. This study shows that the deterioration of EBPR processes through GAO activity at non-limiting P concentrations can be linked to organisms that are typically classified as PAOs, not only to known GAOs such as Competibacter. Intra-clade phylogenetic diversity within Accumulibacter showed that some clusters actually behave similarly to GAOs even without influent phosphate limitation. This study highlights the need to closely re-examine traditional interpretations regarding the link between the microbial community composition and identity with the performance and metabolism of EBPR systems.

Rapid and continuous ammonium adsorption from mainstream coupled with side-stream ammonium recovery and adsorbent regeneration could enable ammonium recovery from domestic wastewater. This study describes the use of tailored poly­(acrylic acid)-based (NaPAA) hydrogels as effective sorbents for ammonium removal from domestic wastewater. Modified NaPAA hydrogels having 60% ionization and 4.8 mol % N′,N′-methylenebisacrylamide as the cross-linker reduced the overall swelling by 92% from 407 to 31 g/g because of higher cross-linking density. At hydrogel loadings of 2.5–7.5 g/L, the NaPAA hydrogels achieved ammonium concentrations of 8.3 ± 0.6 to 10.1 ± 0.1 mg/L NH4–N, which corresponds to removal efficiencies of 53–77% after 10 min of contact time in real domestic wastewater. At the same hydrogel loadings, the ammonium removal efficiency of NaPAA hydrogels in synthetic wastewater was found to be comparable to that in real sewage (71% vs 69%, respectively), suggesting that the sorption performance is only marginally affected by organic constituents found in domestic wastewater. In addition, the NaPAA hydrogels removed 25–51% ammonium in 10 min from synthetic streams having 200–400% higher ionic strengths than those commonly observed in sewage. Furthermore, simulation studies showed that a discharge concentration of ∼1.9 mg/L NH4–N, well below the commonly applied discharge limits in most regions, can be achieved using mainstream ammonium removal by NaPAA hydrogels followed by biological assimilation from the growth of ordinary heterotrophic organisms.

This study evaluates the predictive capacity of the META-ASM model, a new integrated metabolic activated sludge model, in describing the long-term performance of a full-scale enhanced biological phosphorus removal (EBPR) system that suffers from inconsistent performance. In order to elucidate the causes of EBPR upsets and troubleshoot the process accordingly, the META-ASM model was tested as an operational diagnostic tool in a 1336-day long-term dynamic simulation, while its performance was compared with the ASM-inCTRL model, a version based on the Barker & Dold model. Overall, the predictions obtained with the META-ASM without changing default parameters were more reliable and effective at describing the active biomass of polyphosphate accumulating organisms (PAOs) and the dynamics of their storage polymers. The primary causes of the EBPR upsets were the high aerobic hydraulic retention times (HRTs) and low organic loading rates (OLRs) of the plant, which led to periods of starvation. The impact of these factors on EBPR performance were only identified with the META-ASM model. Furthermore, the first signs of process upsets were predicted by variations in the aerobic PAO maintenance rates, suggesting that the META-ASM model has potential to provide an early warning of process upset. The simulation of a new viable operational strategy indicated that troubleshooting the process could be achieved by reducing the aerated volume by switching off air in the first half of the aeration tank. In this new strategy, the META-ASM model predicted a simultaneous improvement in the biological phosphorus (P) and nitrogen (N) removal due to the enhancement of the hydrolysis and fermentation of the mixed liquor sludge in the new unaerated zone, which increased the availability of volatile fatty acids (VFAs) for PAOs. This study demonstrates that the META-ASM model is a powerful operational diagnostic tool for EBPR systems, capable of predicting and mitigating upsets, optimising performance and evaluating new process designs.

Denitrifying sulfur conversion-associated enhanced biological phosphorous removal (DS-EBPR) system is not only a novel wastewater treatment process, but also an ideal model for microbial ecology in a community context. However, it exists the knowledge gap on the roles and interactions of functional microorganisms in the DS-EBPR system for carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) bioconversions. We use genome-resolved metagenomics to build up an ecological model of microbial communities in a lab-scale DS-EBPR system with stable operation for more than 400 days. Our results yield 11 near-complete draft genomes that represent a substantial portion of the microbial community (39.4%). Sulfate-reducing bacteria (SRB) and sulfide-oxidizing bacteria (SOB) promote complex metabolic processes and interactions for C, N, P and S conversions. Bins 1-4 and 10 are considered as new potential polyphosphate-accumulating organisms (PAOs), in which Bins 1-4 can be considered as S-related PAOs (S-PAOs) with no previously cultivated or reported members. Our findings give an insight into a new ecological system with C, N, P and S simultaneous bioconversions and improve the understanding of interactions among SRB, SOB, denitrifiers and PAOs within a community context.

Achromobacter denitrificans PR1 has previously shown potential to degrade the antibiotic sulfamethoxazole, whereby sulfamethoxazole biotransformation was stimulated in the presence of biogenic substrates. This study examined the biotransformation kinetics of sulfamethoxazole and its two main conjugates, N4-acetyl-SMX and SMX-N1-Glucuronide, by activated sludge and activated sludge bioaugmented with A. denitrificans PR1. SMX biotransformation under both anoxic and aerobic conditions was tested, with and without the addition of acetate as growth substrate, to understand the range of applicable conditions for bioaugmentation purposes. Biological process models, such as the pseudo-first order kinetic and cometabolic models, were also applied and, following the estimation of kinetic parameters, could well describe data measured in bioaugmented and non-bioaugmented AS batch experiments under various test conditions. Experimental and modelling results suggest that (i) retransformation of the two conjugates to SMX in AS occurred under both aerobic and anoxic conditions, and (ii) biotransformation kinetics of SMX can vary significantly depending on redox conditions, e.g., SMX was biotransformed by AS only under aerobic conditions. Notably, SMX biotransformation was significantly enhanced when PR1 was bioaugmented in AS. Addition of acetate as biogenic substrate is not necessary, as PR1 was capable of enhancing the SMX biotransformation by using the carbon sources present in wastewater. Overall, bioaugmentation by means of A. denitrificans PR1 could be a viable strategy for enhancing SMX removal in AS wastewater treatment plants (WWTPs).

Mixed microbial cultures (MMCs) are an effective method for polyhydroxyalkanoates (PHA) production. There are several models established to describe the metabolism of this process. Substrate competition was commonly found in the uptake of multiple volatile fatty acids (VFAs), thus this behavior should be considered in process modeling. In this study, a metabolic model is developed to describe for the first time the substrate competition among four commonly used VFAs (acetate, propionate, butyrate and valerate) in PHA production by MMCs. An inhibition parameter was introduced to describe the inhibition of butyrate and valerate on the uptake of acetate and propionate. The modeled results showed good agreement with experimental data within 95% confidence interval. This model enhanced the understanding of the metabolism of substrate uptake in PHA production, providing a successful approach to predict PHA composition and optimize the process efficiency when four competing VFAs are supplied.

In this study, a sequencing batch reactor (SBR), operated with transient carbon availability (feast and famine) and different nutrients loads, was used to select cyanobacteria accumulating poly (3-hydroxyalkanoate) (PHB) and carbohydrates from a mixed wastewater-borne microbial culture. The SBR was operated with 12 h aerobic light and 12 h anaerobic dark phases, evaluating the effect of three different operational conditions consisting on; 1) carbon limitation, 2) carbon and phosphorus limitation and 3) phosphorus limitation. Once a steady state was reached in each operational period of the SBR, part of the biomass was collected and submitted to separate batch tests in order to investigate the maximum PHB and carbohydrates accumulation levels. Batch tests were performed during 24 h of illuminated aerobic condition and 24 h of dark anaerobic condition, while inorganic carbon was constantly present. During the SBR operation, inorganic carbon was mostly used for biomass and carbohydrate production, showing very low PHB accumulation levels (

The emission of the greenhouse gas nitrous oxide (N2O) can occur during biological nutrient removal. Denitrifying enhanced biological phosphorus removal (d-EBPR) systems are an efficient means of removing phosphate and nitrogen, performed by denitrifying polyphosphate-accumulating organisms (d-PAOs). The aim of this work was to study the effect of various combinations of electron acceptors, nitrate (NO3−), nitrite (NO2−), and N2O, on the denitrification pathway of a d-EBPR system. Batch tests were performed with different electron acceptor combinations, to explore the denitrification pathway. Reverse transcriptase-qPCR (RT-qPCR) and high-throughput sequencing, combined with chemical analysis, were used to study gene expression, microbial diversity, and denitrification kinetics. The potential for N2O production was greater than the potential for its reduction in most tests. A strong correlation was observed between the N2O reduction rate and the relative gene expression of nitrous oxide reductase per nitrite reductase (nosZ/(nirS + nirK)), suggesting that the expression of denitrifying marker genes is a strong predictor of the N2O reduction rate. The d-EBPR community maintained a core population with low variations throughout the study. Furthermore, phylogenetic analyses of the studied marker genes revealed that the organisms actively involved in denitrification were closely related to Thauera sp., Candidatus Accumulibacter phosphatis, and Candidatus Competibacter denitrificans. Moreover, Competibacter-related OTUs seem to be important contributors to the N2O reduction capacity of the system, likely scavenging the N2O produced by other organisms. Overall, this study contributes to a better understanding of the microbial biochemistry and the genetics involving biological denitrification removal, important to minimize N2O emissions in wastewater treatment plants.

In enhanced biological phosphorus removal (EBPR), Tetrasphaera can potentially be an abundant and important polyphosphate accumulating organism (PAO), however ongoing questions remain concerning its storage compounds, phosphorus (P) removal capabilities and metabolic behaviour. This study investigated each of these points in an enriched Tetrasphaera culture (95% biovolume). The enriched Tetrasphaera culture fermented amino acids, while also converting and storing diverse amino acids as aspartic and glutamic acid within cells. Subsequent intracellular consumption of these two amino acids during the aerobic phase supports their importance in the metabolism of Tetrasphaera. Polyhydroxyalkanoate (PHA) cycling was also observed in this study, in contrast to some previous studies on Tetrasphaera. While exhibiting anaerobic phosphorus release and aerobic uptake, the highly enriched Tetrasphaera culture was unable to completely remove phosphorus in sequencing batch reactors (SBR) cycles, with an average removal efficiency of 72.3 ± 7.8%. This is unlike a previous study containing both Tetrasphaera (70%) and Accumulibacter (22%), which regularly performed complete phosphorus removal under otherwise similar operational conditions, at efficiencies of > 99%. Notably, the phylodiversity of organisms belonging to Tetrasphaera was substantially different in the present work, consisting mainly of organisms within Clade 2, likely impacting PHA cycling. These results suggest that the contribution of Tetrasphaera towards P removal is highly dependent on the composition of its Clades within this microbial group and an observed higher abundance of Tetrasphaera in WWTPs does not necessarily imply overall higher P removal. This study improves our understanding of the role of Tetrasphaera within EBPR systems and key factors impacting its metabolism.

Biological nitrogen (N) removal via the short-cut pathway (NH4+-N→NO2−-N→N2) is economically attractive in wastewater treatment plants (WWTPs). However, biological phosphorus (P) removal processes remain a bottleneck in these systems due to the strong inhibitory effect of nitrite or its protonated form (HNO2, free nitrous acid - FNA) on polyphosphate accumulating organisms (PAOs). In this study, a novel combined nitrogen and phosphorus removal strategy was verified and achieved in a biological short-cut nitrogen removal system via side-stream sludge treatment with FNA, and the mechanisms impacting this process were investigated. The side-stream FNA treatment process applied here led to a significant reduction in the real sludge retention time (SRT) in the mainstream (approximately 2.7 days) based on the biocidal effect of FNA to the majority of the organisms. This work also found that around 40% of the P uptake activity was still maintained at a much higher FNA level of 38 μg N/L with potential PAOs, which highly broadened the current knowledge of PAOs community. An economic analysis revealed advantages of the proposed as compared to conventional biological nitrogen and phosphorus removal (13% savings in total cost), biological short-cut nitrogen removal (via FNA treatment) with chemical phosphorus precipitation (21% savings) and conventional biological nitrogen removal with chemical precipitation (27% savings). Overall, this study presents a novel and viable retrofit strategy in integrating biological short-cut nitrogen removal with EBPR for next generation WWTPs.

The main objective of this paper is to develop a methodology for modelling dry and wet weather operational costs applied to the Alcântara Water Resource Recovery Facility (WRRF), which is the largest Portuguese WRRF. Following data collection and intensive data treatment and validation, dry weather patterns of WRRF performance were combined with specific operational costs and described by a conceptual model. The impact of infiltration flows on operational costs was identified. The model simulations show a significant variation of distribution costs during wet weather periods compared with dry weather periods. The methodology can be used for predicting dry and wet weather operational costs and for defining dry weather tariffs and wet weather tariffs. Moreover, the analysis of the dry and wet weather period can also be used for infiltration quantification.

Denitrifying enhanced biological phosphorus removal (EBPR) systems can be an efficient means of removing phosphate (P) and nitrate (NO3−) with low carbon source and oxygen requirements. Tetrasphaera is one of the most abundant polyphosphate accumulating organisms present in EBPR systems, but their capacity to achieve denitrifying EBPR has not previously been determined. An enriched Tetrasphaera culture, comprising over 80% of the bacterial biovolume was obtained in this work. Despite the denitrification capacity of Tetrasphaera, this culture achieved only low levels of anoxic P-uptake. Batch tests with different combinations of NO3−, nitrite (NO2−) and nitrous oxide (N2O) revealed lower N2O accumulation by Tetrasphaera as compared to Accumulibacter and Competibacter when multiple electron acceptors were added. Electron competition was observed during the addition of multiple nitrogen electron acceptors species, where P uptake appeared to be slightly favoured over glycogen production in these situations. This study increases our understanding of the role of Tetrasphaera-related organisms in denitrifying EBPR systems The authors thank the Portuguese Fundação para a Ciência e Tecnologia (UID/Multi/04378/2013, AMB/120581/2010), UCIBIO (FCT/MEC UID/Multi/04378/2013, POCI-01-0145-FEDER-007728), the European Commission (Water JPI project 196 (WaterWorks2014 ERA-NET Co-funded Call): “Smart decentralized water management through a dynamic integration of technologies (Watintech)”) and the Spanish Government through project CTM2015-66892-R for financing. Ricardo Marques acknowledges the PhD grant (SFRH/BD/74515/2010) provided by the Portuguese Fundação para a Ciência e Tecnologia. Spanish and Portuguese Governments are acknowledged for Acciones Integradas (PRI-AIBPT-2011-1232) and Luso-Espanhola action E-61/12. The European Commission is also acknowledged through COST action ES1202 (Water 2020). A. Ribera-Guardia acknowledge the FPIPhD grant (BES-2012-052753) provided by the Spanish Government

This study aims at investigating the denitrification kinetics in two separate enriched cultures of denitrifying polyphosphate accumulating organisms (dPAO) and denitrifying glycogen accumulating organisms (dGAO) and compare their N2O accumulation potential under different conditions. Two sequencing batch reactors were inoculated to develop dPAO and dGAO enriched microbial communities separately. Seven batch tests with different combinations of electron acceptors (nitrate, nitrite and/or nitrous oxide) were carried out with the enriched biomass from both reactors. Results indicate that in almost all batch tests, N2O accumulated for both cultures, however dPAOs showed a higher denitrification capacity compared to dGAOs due to their higher nitrogen oxides reduction rates. Additionally, the effect of the simultaneous presence of several electron acceptors in the reduction rates of the different nitrogen oxides was also assessed in dPAOs and dGAOs This study was funded by the Spanish Government (MINECO) (CTM 2011-27163 and CTM 2015-66892-R), the European Commission (FP7-PEOPLE-2011-CIG 303946) and the Portuguese Fundação para a Ciência e Tecnologia (PTDC/AACAMB/12058/2010, UID/Multi/04378/2013 , PhD grant SFRH/BD/74515/2010). Spanish and Portuguese Governments are acknowledged for Acciones Integradas (PRIAIBPT- 2011-1232) and Luso-Espanhola action E-61/12. The European Commission is also acknowledged through COST action ES1202 (Water 2020). M. Pijuan and A. Ribera-Guardia acknowledge the Ramon y Cajal research fellowship (RYC-2009-04959) and the FPIPhD grant (BES-2012-052753) respectively provided by the Spanish Government

Polyhydroxyalkanoates (PHAs) production with phototrophic mixed cultures (PMCs) has been recently proposed. These cultures can be selected under the permanent presence of carbon and the PHA production can be enhanced in subsequent accumulation steps. To optimize the PHA production in accumulator reactors, this work evaluated the impact of 1) initial acetate concentration, 2) light intensity, 3) removal of residual nitrogen on the culture performance. Results indicate that low acetate concentration (, 29 pages, 4 figures, 4 tables

This study demonstrates that META-ASM, a new integrated metabolic activated sludge model, provides an overall platform to describe the activity of the key organisms and processes relevant to biological nutrient removal (BNR) systems with a robust single-set of default parameters. This model overcomes various shortcomings of existing enhanced biological phosphorous removal (EBPR) models studied over the last twenty years. The model has been tested against 34 data sets from enriched lab polyphosphate accumulating organism (PAO)-glycogen accumulating organism (GAO) cultures and experiments with full-scale sludge from five water resource recovery facilities (WRRFs) with two different process configurations: three stage Phoredox (A2/O) and adapted Biodenitro™ combined with a return sludge sidestream hydrolysis tank (RSS). Special attention is given to the operational conditions affecting the competition between PAOs and GAOs, capability of PAOs and GAOs to denitrify, metabolic shifts as a function of storage polymer concentrations, as well as the role of these polymers in endogenous processes and fermentation. The overall good correlations obtained between the predicted versus measured EBPR profiles from different data sets support that this new model, which is based on in-depth understanding of EBPR, reduces calibration efforts. On the other hand, the performance comparison between META-ASM and literature models demonstrates that existing literature models require extensive parameter changes and have limited predictive power, especially in the prediction of long-term EBPR performance. The development of such a model able to describe in detail the microbial and chemical transformations of BNR systems with minimal adjustment to parameters suggests that the META-ASM model is a powerful tool to predict and mitigate EBPR upsets, optimise EBPR performance and to evaluate new process designs.

Glycogen accumulating organisms (GAOs) are thought to compete with polyphosphate accumulating organisms (PAOs) for the often-limiting carbon sources available in wastewater, deteriorating enhanced biological phosphorus removal (EBPR) performance at high temperatures. Fermentation liquids are often used to provide an additional carbon source supply in EBPR processes, where butyrate is known to be an important volatile fatty acid (VFA) produced in sludge fermentation. Nevertheless, the impact of butyrate on the PAO-GAO competition is not well understood especially at high temperature. The results of this study demonstrate that butyrate, as a supplemental or sole carbon source, could be promising for EBPR in tropical climates. When the carbon source was gradually changed from acetate to butyrate, a substantial PAO population was found under both conditions, despite a substantial shift in the abundance of Candidatus Accumulibacter phosphatis (decreased from 37.4% to 13.9%) to Rhodocyclaceae (increased from 2.0% to 14.5%), where both organisms likely played an important role in P-removal. Thus, a relatively stable P removal performance was realized throughout the whole operation period. Nevertheless, butyrate had a negative impact on GAOs. The biomass concentration and microbial diversity continually decreased in the GAO reactor, and Candidatus Competibacter phosphatis reduced from 27.3% to 6.2%, where the dominant population was replaced by Zoogloea. With the addition of butyrate as carbon source, the total amount of synthesized PHAs reduced in both PAO and GAO cultures and the composition of PHA was greatly changed. The presence of a novel PHA fraction (PHH) may disturb the microbial activity in the aerobic phase, where the GAO culture was more severely affected. Glycogen cycling also seemed to be limited in both reactors. This could reduce the GAO metabolism in both cultures and favor PAOs and P removal. Furthermore, the biomass growth rate of the PAO culture was higher than that of GAO when fed with butyrate, which also provides PAO a competitive advantage. All the above results indicate that butyrate could not be well metabolized by GAOs, but could provide PAOs a competitive advantage. Thus, mixed VFAs (i.e. acetate, propionate and butyrate) are likely to favor PAOs over GAOs in EBPR processes operated in warm climates, where the impact of substantial butyrate fractions represents an advantage towards successful process operation. Nanyang Technological University The authors are grateful for the financial support provided by the Advanced Environmental Biotechnology Centre (AEBC) of Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, Singapore, and the Research Fund for the Doctoral Program of Singapore and Interdisciplinary Graduate School of Nanyang Technological University.

Currently, the feast and famine (FF) regime is the most widely applied strategy to select for polyhydroxyalkanoate (PHA) accumulating organisms in PHA production systems with mixed microbial cultures. As an alternative to the FF regime, this work studied the possibility of utilizing a permanent feast regime as a new operational strategy to select for PHA accumulating photosynthetic mixed cultures (PMCs). The PMC was selected in an illuminated environment and acetate was constantly present in the mixed liquor to guarantee a feast regime. During steady-state operation, the culture presented low PHA accumulation levels, likely due to low light availability, which resulted in most of the acetate being used for biomass growth (Yx/s of 0.64 ± 0.18 Cmol X/Cmol Acet). To confirm the light limitation on the PMC, SBR tests were conducted with higher light availability, at similar levels as would be expectable from natural sunlight. In this case, the Yx/s reduced to 0.11 ± 0.01 Cmol X/Cmol Acet and the culture presented a PHB production yield on acetate of 0.67 ± 0.01 Cmol PHB/Cmol Acet, leading to a maximum PHB content of 60%. Unlike other studied PMCs, the PMC was capable of simultaneous growth and PHB accumulation continuously throughout the cycle. Thus far, 60% PHA content is the maximum value ever reported for a PMC, a result that prospects the utilization of feast regimes as an alternative strategy for the selection of PHA accumulating PMCs. Furthermore, the PMC also presented high phosphate removal rates, delivering an effluent that complies with phosphate discharge limits. The advantages of selecting PMCs under a permanent feast regime are that no aeration inputs are required; it allows higher PHA contents and phosphate removal rates in comparison to FF-operated PMC systems; and it represents a novel means of integrating wastewater treatment with resource recovery in the form of PHA.

Wastewater effluent discharges have been considered as one of the main sources of synthetic chemicals entering into the aquatic environment. Even though they occur at low concentrations, pharmaceutically active compounds (PhACs) can have an impact on ecological toxicity that affects aquatic organisms. Moreover, new regulations in development toward preserving water quality reinforces the increasing need to monitor and abate some PhACs in wastewater treatment plants (WWTPs), where they are typically only partially eliminated. Unlike most previous reviews, we have focussed on how the main biological and chemical molecular factors impact the biotransformations of key PhACs in biological WWTP processes. Biotransformations have been found to be an important contributor towards the removal of PhACs from WWTP effluents. This review paper critically assesses these aspects and the recent advances that have been achieved in wastewater treatment processes for biodegradation of 7 PhACs; namely the non-steroidal anti-inflammatory drug (NSAID) diclofenac (DCF); the macrolide antibiotics azithromycin (AZM), erythromycin (ERY) and clarithromycin (CLR); the two natural estrogens estrone (E1) and 17β-estradiol (E2), and the synthetic estrogen 17α-ethinylesradiol (EE2). These represent the micropollutants of the EU Watch list in Decision 2015/495/EU that are most relevant to WWTPs due to their frequent detection. The metabolic pathways, transformation products and impact of relevant factors to biological WWTP processes is addressed in this review. The biokinetics of PhAC biodegradation in different engineered bioprocesses is also discussed. Promising technologies and operational strategies that are likely to have a high impact on controlling PhAC releases are highlighted and future research needs are also proposed.

Anaerobic digestion has been shown to be an effective treatment for high organic matter wastes, while producing clean energy. However, anaerobic digesters in some companies must support variations of substrate composition due to the seasonality of feedstocks. In this study, a two-stage anaerobic digestion system was operated treating three different fruit pulp wastes in a sequential operation. The effect of substrate shifts and operational conditions on acidogenesis, biogas production/composition and overall system performance was assessed. Substrate shifts did not cause long-term instability issues. No evident association was found between operational condition changes on the profile of fermentation products and acidification degrees (53.7%–76.4%) in the acidogenic stage. However, substrate composition affected the gas production in the acidogenic stage, whereas it had no effect on the gas production in the methanogenic stage. The initial substrate composition affected the percentage of hydrogen (H2) (0–34%) in the biogas produced in the first stage. Consistently high methane (CH4) yields (0.30–0.37 LCH4 g−1 CODdegraded) were obtained in the methanogenic stage. The biogas produced in the second stage (0.5–2.1 LCH4 L−1 d−1) was rich in CH4 (75.9–80.6%) regardless of the operational conditions tested. The CH4 produced could be used to generate energy up to 79.5 kJ Lreactor−1 d−1 while the H2 production in the acidogenic reactor, when treating fruit pulp waste with high content of sugars, could further increase this energy by up to 22.4% (H2 content between 25 and 30%). This process has shown to be robust in treating seasonal wastes from a fruit juice industry, supporting full scale application.

This study investigated the effects of different carbon sources on enriched Accumulibacter PAO cultures at high temperature (30 °C) and compared the carbon transformation with low temperature (20 °C) cases reported in literature, revealing several key metabolic differences. While PAOs seemed to prefer propionate anaerobically as compared to other VFAs at high temperature, high aerobic glycogen replenishment was realized with propionate as the anaerobic carbon source, a trait not previously observed at low temperatures. Therefore, it was found that propionate is not correlated with high P removal by Accumulibacter PAO at high temperatures. A combined substrate of acetate, propionate and perhaps butyrate seemed to be a better carbon source combination, since the total VFA uptake rate increased by up to 46%, and this increased the aerobic P-removal efficiency by up to 38.4% and reduced the glycogen recovery by more than 63% compared to the use of only propionate as substrate. This study improves our understanding of how to stimulate successful EBPR operation in warm climates by augmenting the P removal performance of PAOs. Nanyang Technological University The authors are grateful for the financial support provided by the Advanced Environmental Biotechnology Centre (AEBC) of Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, Singapore, and the Research Fund for the Doctoral Program of Singapore and Interdisciplinary Graduate School of Nanyang Technological University

Polyhydroxyalkanoates (PHAs) are biobased, biodegradable polymers that can be produced efficiently by mixed microbial cultures (MMCs) at low cost. Substrate preferences have been found to vary depending on the microbial composition in the MMCs. In this study, the competition between the uptake of different substrates has been related for the first time to the abundance of certain microbial communities. With a higher abundance of Plasticicumulans enriched in the culture, the inhibitory effect of butyrate and valerate on the uptake of acetate and propionate increased and the hydroxybutyrate:hydroxyvalerate (HB:HV) ratio in the final PHA polymer approached the theoretical value calculated from the volatile fatty acid (VFA) composition. This finding can help understanding of the metabolism of PHA accumulating microorganisms and thus predict better the VFA consumption and PHA composition.

An indigenous plant growth-promoting bacterium isolated from Peganum Harmala rhizosphere in the arid ecosystem was found to solubilize and accumulate phosphates. This isolate was identified as Pseu...

Achromobacter denitrificans strain PR1, previously found to harbour specific degradation pathways with high sulfamethoxazole (SMX) degradation rates, was bioaugmented into laboratory-scale membrane bioreactors (MBRs) operated under aerobic conditions to treat SMX-containing real domestic wastewater. Different hydraulic retention times (HRTs), which is related to reaction time and loading rates, were considered and found to affect the SMX removal efficiency. The availability of primary substrates was important in both bioaugmented and non-bioaugmented activated sludge (AS) for cometabolism of SMX. High HRT (24 h) resulted in low food to microorganism ratio (F/M) and low SMX removal, due to substrate limitation. Decrease in HRT from 24 h to 12 h, 6 h and finally 4 h led to gradual increases in primary substrates availability, e.g. organic compounds and ammonia, resulted in increased SMX removal efficiency and degradation rate, and is more favorable for high-rate wastewater treatment processes. After inoculation into the MBRs, the bioaugmentation strain was sustained in the reactor for a maximum of 31 days even though a significant decrease in abundance was observed. The bioaugmented MBRs showed enhanced SMX removal, especially under SMX shock loads compared to the control MBRs. The results of this study indicate that re-inoculation is required regularly after a period of time to maintain the removal efficiency of the target compound. (c) 2018 Elsevier B.V.

Polyhydroxyalkanoates (PHA) bioplastics, which are produced by pure and mixed culture biotechnology, are high-performance and truly biodegradable materials. The use of organic wastes as feedstocks for PHA production has been widely documented, though the focus has been on increasing PHA yield; knowledge of the resulting polymer quality and processability has been lacking. In this chapter, it is shown that copolymer composition, blend composition, thermal properties, molecular weight, type of processing and other characteristics such as microstructure and crystallisation kinetics all govern the mechanical properties, but property-structure relationships are complex, and therefore more research in this space is needed, regardless of the feedstock. Still, there is no doubt that organic wastes can be used as feedstocks for PHA production—particularly if they are pretreated—and there is now interest in commercialisation of PHA bioplastics from such wastes. But further advances are tempered with the conclusion that, for organic wastes to be viable feedstocks, the waste must be relatively abundant, concentrated and readily degradable. For some perspective, mass flows of organic wastewater streams from some relevant Australian industries are presented. It is shown that only if all the wastes from any given industry were collected and consolidated would there be sufficient feedstock for production of industrially relevant volumes of PHA.

The biodegradation of dyes remains one of the biggest challenges of textile wastewater. Azo dyes are one of the most commonly employed dye classes, and biological treatment processes tend to generate recalcitrant aromatic amines, which are more toxic than the parent dye molecule. This study aimed to isolate bacterial strains with the capacity to degrade both the azo dye and the resulting aromatic amines towards the development of a simple and reliable treatment approach for dye-laden wastewaters. A mixed bacterial enrichment was first developed in an anaerobic-aerobic lab-scale sequencing batch reactor (SBR) fed with a synthetic textile wastewater containing the model textile azo dye Acid Red 14 (AR14). Eighteen bacterial strains were isolated from the SBR, including members of the Acinetobacter, Pseudomonas and Oerskovia genera, Oerskovia paurometabola presenting the highest decolorization capacity (91% after 24 h in static anaerobic culture). Growth assays supported that this is a facultative bacterium, and decolorization batch tests with 20–100 mg AR14 L−1 in a synthetic textile wastewater supplemented with yeast extract indicated that O. paurometabola has a high color removal capacity for a significant range of AR14 concentrations. In addition, a model typically used to describe biodegradation of xenobiotic compounds was adjusted to the results, to predict AR14 biodegradation time profiles at different initial concentrations. HPLC analysis confirmed that decolorization occurred through azo bond reduction under anaerobic conditions, the azo dye being completely reduced after 24 h of anaerobic incubation for the range of concentrations tested. Interestingly, partial (up to 63%) removal of one of the resulting aromatic amines (4-amino-naphthalene-1-sulfonic acid) was observed when subsequently subjected to aerobic conditions. Overall, this work showed the azo dye biodegradation potential of specific bacterial strains isolated from mixed culture bioreactors, reporting for the first time the decolorization capacity of an Oerskovia sp. with further biodegradation of a recalcitrant sulfonated aromatic amine metabolite.

A comprehensive assessment of full-scale enhanced biological phosphorus removal (EBPR) plants (five plants, 19 independent tests) was undertaken to determine their effectiveness in terms of aerobic and anoxic P removal. By comparing parallel P uptake tests under only aerobic or under anoxic-aerobic conditions, results revealed that introducing an anoxic stage led to an overall P removal of on average 90% of the P removed under only aerobic conditions. This was achieved with negligible higher PHA and glycogen requirements, 30% lower overall oxygen consumption and with the simultaneous removal of nitrate, reducing up to an estimate of 70% of carbon requirements for simultaneous N and P removal. Varying fractions of denitrifying polyphosphate accumulating organisms (DPAOs), from an average of 25% to 84%, were found in different plants. No correlation was found between the DPAO fractions and EBPR configuration, season, or the concentration of any of the microbial groups measured via quantitative fluorescence in situ hybridisation. These included Type I and Type II Ca. Accumulibacter and glycogen accumulating organisms, suggesting that chemical batch tests are the best methodology for quantifying the potential of anoxic P removal in full-scale wastewater treatment plants.

The increase of salt concentrations in influent wastewaters will be a consequence of the sea level rises in coastal areas due to climate change and the future use of seawater to flush toilets as a cost-attractive option for alternative water resources. Yet, little is known about the salinity effect on full-scale wastewater treatment plants (WWTPs) performance and on greenhouse gas (GHG) emissions, such as nitrous oxide (N2O). This study aimed at quantifying the N2O emissions of a full-scale biological aerated filter (BAF) and to correlate the dynamic behavior of the emissions with the process conditions and the periods of infiltration of seawater. A full-scale BAF was monitored for 3 months to assess both their gaseous and liquid N2O fluxes. The total average daily N2O emissions of the plant were 6.16 g N–N2O/kg of NH4–N removed. For the first time at full-scale, a correlation between the N2O emissions and the wastewater influent conductivity (salinity) was found, in which the increase in seawater infiltration in the sewer at high tide augments the daily N2O production and emission to 13.78 g N–N2O/kg of NH4–N removed. The proportional increase in influent conductivity and the N2O emission factor in this WWTP suggested that periods of high conductivity could serve as an indicator of increased N2O emissions by the plant. Furthermore, the operational conditions and the wastewater influent characteristics that influence the N2O emissions were identified as being the dissolved oxygen (DO) dynamics due to the filter washing steps, leading to rapid transitions from oxic to sub-oxic conditions, as well as the (re-)adaptation of microbial consortia due to the dynamics of the biofilm thickness associated to the daily washing process. This study shows the impact that the washing process and seawater infiltration has on the N2O emissions of a BAF and contributes to a better understanding of the operational conditions impacting the emissions in WWTPs.

Mixed microbial cultures are a viable means for polyhydroxyalkanoate (PHA) production, which can produce polymers of commercial quality with high yields. Various PHA co-polymer blends can be produced by surplus full-scale municipal activated sludge fed with fermented waste feedstocks. In biological nutrient removal, ammonia is converted to nitrate by ammonia and nitrite oxidizing bacteria (AOBs and NOBs) through nitrification and removed as nitrogen gas through denitrification. Activated sludge can be enriched with significant PHA storage potential alongside nitrogen removal by denitrifying heterotrophic and nitrifying autotrophic bacteria. The latter adds complexity and aeration demand during the aerobic side-stream PHA accumulation stage since fermented organic residuals often contain significant amounts of ammonia. In the present work, the influence of dissolved oxygen (DO) levels on both PHA accumulation and nitrification rates for a municipal activated sludge were evaluated. The objective was to identify potential for a DO control strategy for PHA accumulation, which would mitigate the unnecessary nitrification activity during PHA production. A much higher apparent Michaelis–Menten DO affinity for volatile fatty acid (VFA) consumption (KDO _VFA 0.1 ± 0.06 mg/L) was found as compared to nitrification (KDO _NH4 2.87 ± 1.31 mg/L). Consequently, with lower DO levels, PHA production was not limited by oxygen supply, while nitrogen was removed by simultaneous nitrification and denitrification processes. This study suggests a method for PHA accumulation using nitrifying activated sludge, while feeding ammonia-containing organic feedstocks by means of DO level control where: (1) NOB activity and growth are both mitigated, (2) nitrogen removal is facilitated, (3) alkalinity is controlled through simultaneous denitrification, and (4) energy demand for aeration is reduced.

Few attempts have been made in previous studies to link the microbial community structure and function with nitrous oxide (N2O) emissions at full-scale wastewater treatment plants (WWTPs). In this work, high-throughput sequencing and reverse transcriptase-qPCR (RT-qPCR) was applied to activated sludge samples from three WWTPs for two seasonal periods (winter and summer) and linked with the N2O emissions and wastewater characteristics. The total N2O emissions ranged from 7.2 to 937.0 g N-N2O/day, which corresponds to an emission factor of 0.001 to 0.280% of the influent NH4-N being emitted as N2O. Those emissions were related to the abundance of Nitrotoga, Candidatus Microthrix and Rhodobacter genera, which were favored by higher dissolved oxygen (DO) and nitrate (NO3−) concentrations in the activated sludge tanks. Furthermore, a relationship between the nirK gene expression and N2O emissions was verified. Detected N2O emission peaks were associated with different process events, related to aeration transition periods, that occurred during the regular operation of the plants, which could be potentially associated to increased emissions of the WWTP. The design of mitigation strategies, such as optimizing the aeration regime, is therefore important to avoid process events that lead to those N2O emissions peaks. Furthermore, this study also demonstrates the importance of assessing the gene expression of nosZ clade II, since its high abundance in WWTPs could be an important key to reduce the N2O emissions.

Ibuprofen (IBU) is a non-steroidal anti-inflammatory drug that is becoming increasingly recognized as an important micropollutant to be monitored in wastewater treatment plants (WWTP), since it has been detected in effluents at the µg L

Poster presented at the World Congress on Industrial Biotechnology, in Philadelphia USA, 17-19 July 2018. &nbsp

Food and beverage industry wastes present high amounts of organic matter, which may cause water quality degradation if not treated. Two-stage anaerobic digestion is a promising and efficient solution for the treatment of this type of wastes whilst producing bioenergy. The composition of fruit pulp waste varies throughout the different harvesting seasons, which may impact the process performance. In this study, a two-stage anaerobic digestion system was operated to assess the effect of substrate shift from peach to apple pulp wastes (obtained from a fruit juice company) on the microbial community activity and performance. During acidogenesis, the sugar conversion was higher than 95% for all operational conditions tested, obtaining a degree of acidification up to 89%. Principal Component Analysis was used to evaluate the relationship between the initial fermentation state of the residues in each operational condition and the obtained effluent. Methanogenic activity resulted in high organic carbon consumption (89%) and high methane productivities, achieving a maximum of 4.33 L C H 4 / L . d for peach waste influent. Overall, the results showed that the microbial community activity was not affected by the substrate shift, converting the sugars into biogas rich in methane (>70% CH4). Microbial analysis showed that the communities present in the acidogenic and methanogenic reactors were highly enriched in bacteria and archaea, respectively. The observed stability of the process, also demonstrated in pilot scale, confirmed the robustness of the process and thus, was suitable for implementation in companies producing seasonally different fruit wastes in a continuous operation.