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- Long-term stability of a non-adapted aerobic granular sludge process treating fish canning wastewater associated to EPS producers in the core microbiomePublication . Paulo, Ana M. S.; Amorim, Catarina L.; Costa, Joana; Mesquita, Daniela P.; Ferreira, Eugénio C.; Castro, Paula M. L.The tolerance of aerobic granular sludge (AGS) to variable wastewater composition is perceived as one of its greatest advantages compared to other aerobic processes. However, research studies select optimal operational conditions for evaluating AGS performance, such as the use of pre-adapted biomass and the control of wastewater composition. In this study, non-adapted granular sludge was used to treat fish canning wastewater presenting highly variable organic, nutrient and salt levels over a period of ca. 8 months. Despite salt levels up to 14 g NaCl L−1, the organic loading rate (OLR) was found to be the main factor driving AGS performance. Throughout the first months of operation, the OLR was generally lower than 1.2 kg COD m−3 day−1, resulting in stable nitrification and low COD and phosphorous levels at the outlet. An increase in OLR up to 2.3 kg COD m−3 day−1 disturbed nitrification and COD and phosphate removal, but a decrease to average values between 1 and 1.6 kg COD m−3 day−1 led to resuming of those processes. Most of the bacteria present in the AGS core microbiome were associated to extracellular polymeric substances (EPS) production, such as Thauera and Paracoccus, which increased during the higher OLR period. Ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) species were detected in AGS biomass; while AOB were identified throughout the operation, NOB were no further identified after the period of increased OLR. Different polyphosphate-accumulating organisms (PAOs) were detected along the process: Candidatus Accumulibacter, Tetrasphaera and Gemmatimonas. A non-adapted granular sludge was able to treat the fish canning wastewater and to tolerate salinity fluctuations up to 14 g L−1. Overall, a high microbial diversity associated to EPS producers allowed to preserve bacterial groups responsible for nutrients removal, contributing to the adaptation and long-term stability of the AGS system.
- Simultaneous partial nitrification and 2-fluorophenol biodegradation with aerobic granular biomass: reactor performance and microbial communitiesPublication . Ramos, Carlos; Amorim, Catarina L.; Mesquita, Daniela P.; Ferreira, Eugénio C.; Carrera, Julián; Castro, Paula M. L.An aerobic granular bioreactor was operated for over 4months, treating a synthetic wastewater with a high ammonium content (100mgNL-1). The inoculum was collected from a bioreactor performing simultaneous partial nitrification and aromatic compounds biodegradation. From day-56 onwards, 2-fluorophenol (2-FP) (12.4mgL-1) was added to the feeding wastewater and the system was bioaugmented with a 2-FP degrading bacteria (Rhodococcus sp. FP1). By the end of operation, complete 2-FP biodegradation and partial nitrification were simultaneously achieved. Aerobic granules remained stable over time. During the 2-FP loading, a shift in the community structure occurred, coinciding with the improvement of 2-FP degradation. DGGE analysis did not allow to infer on the bioaugmented strain presence but pyrosequencing analysis detected Rhodococcus genus by the end of operation. Together with other potential phenolic-degraders within granules, these microorganisms were probably responsible for 2-FP degradation.
- Variability in the composition of extracellular polymeric substances from a full-scale aerobic granular sludge reactor treating urban wastewaterPublication . Oliveira, Ana S.; Amorim, Catarina L.; Ramos, Miguel A.; Mesquita, Daniela P.; Inocêncio, Paulo; Ferreira, Eugénio C.; Loosdrecht, Mark van; Castro, Paula M. L.Within the framework of the circular economy, there is a need for waste management alternatives that promote the reuse of materials produced in wastewater treatment plants (WWTP). An interesting option is the recovery of extracellular substances from sludge. The variability of characteristics of potential recovered bioproducts has to be assessed in full scale operational settings. In this study, aerobic granular sludge (AGS) from a full-scale WWTP treating urban wastewater was regularly collected for 4 months to assess variability in extracellular polymeric substances (EPS) composition and in granular morphology. Variations in the EPS composition occurred with time. Proteins and humic substances were the main EPS components (329–494 and 259−316 mg/g VSS of AGS, respectively), with polysaccharides and DNA representing minor components. The application of an extra purification step after extraction to obtain a purer EPS led to a decrease in the yield of each EPS component, particularly pronounced for the polysaccharides. The final product had a rather constant composition for the monthly samples. The granules showed morphological stability throughout the sampling period and the yield of EPS was correlated to the size of the granules, higher when there was a higher content of small granules (Deq<150 μm) comparing to intermediate (150 ≤ Deq<1500 μm) or large granules (Deq≥1500 μm). This is the first time that a potential valorization strategy for surplus AGS biomass is studied in a full-scale environment. Knowledge on yield and product homogeneity is important as these features are essential for downstream application of the recovered EPS.
- Impact of industrial wastewater on aerobic granules morphology and nitrification process in bioreactorsPublication . Paulo, Ana M. S.; Costa, Joana; Amorim, Catarina L.; Mesquita, Daniela P.; Ferreira, Eugénio C.; Castro, Paula M.L.
- Sludge volume index and suspended solids estimation of mature aerobic granular sludge by quantitative image analysis and chemometric toolsPublication . Leal, Cristiano; Río, Angeles Val del; Mesquita, Daniela P.; Amaral, António L.; Castro, Paula M. L.; Ferreira, Eugénio C.Aerobic granular sludge (AGS) is considered a promising technology for wastewater treatment. Furthermore, it is recognized that the stability of the process is related to the balanced growth of the suspended (floccular) and granular fractions. Therefore, the development of adequate techniques to monitor this balance is of interest. In this work the sludge volume index (SVI), volatile suspended solids (VSS) and total suspended solids (TSS) of mature AGS were successfully predicted with multilinear regression (MLR) models using data obtained from quantitative image analysis (QIA) of both fractions (suspended and granular). Relevant predictions were obtained for the SVI (R2 of 0.975), granules TSS (R2 of 0.985), flocs TSS (R2 of 0.971), granules VSS (R2 of 0.984) and flocs VSS (R2 of 0.986). The estimation of the granular fraction ratio from the predicted TSS and VSS was also successful (R2 of 0.985). The predictions help to avoid instability episodes of the AGS system, such as changes in biomass morphology, structure and settling properties.