Competition between polyphosphate and glycogen accumulating organisms in enhanced biological phosphorus removal systems with acetate and propionate as carbon sources

Enhanced biological phosphorus removal (EBPR) is a widely used process for achieving phosphorus removal from wastewater. A potential reason for EBPR failure is the undesirable growth of glycogen accumulating organisms (GAOs), which can compete for carbon sources with the bacterial group responsible for phosphorus removal from wastewater: the polyphosphate accumulating organisms (PAOs). This study investigates the impact of carbon source on EBPR performance and the competition between PAOs and GAOs. Two sequencing batch reactors (SBRs) were operated during a 4-6 month period and fed with a media containing acetate or propionate, respectively, as the sole carbon source. It was found that the acetate fed SBR rarely achieved a high level of phosphorus removal, and that a large portion of the microbial community was comprised of Candidatus Competibacter phosphatis, a known GAO. The propionate fed SBR, however, achieved stable phosphorus removal throughout the study, apart from one brief disturbance. The bacterial community of the propionate fed SBR was dominated by Candidatus Accumulibacter phosphatis, a known PAO, and did not contain Competibacter In a separate experiment, another SBR was seeded with a mixture of PAOs and a group of alphaproteobacterial GAOs, both enriched with propionate as the sole carbon source. Stable EBPR was achieved and the PAO population increased while the GAOs appeared to be out-competed. The results of this paper suggest that propionate may provide PAOs with a selective advantage over GAOs in the PAO-GAO competition, particularly through the minimisation of Competibacter Propionate may be a more suitable substrate than acetate for enhancing phosphorus removal in EBPR systems. (c) 2005 Elsevier B.V. All rights reserved.

Avaliação de processo de lodos ativos por batelada seguido de tratamento terciário com ênfase na remoção de matéria orgânica e na sedimentabilidade do lodo

This paper evaluate the performance of a Wastewater Treatment Plant (WWTP) in sequential batch activated sludge modality with tertiary treatment step, located in high temperature region. It also presents the analysis of organic matter’s removal and the evaluation of sludge sedimentation conditions through reactors in bench scale, fed with different substrate’s and biomass’ concentrations, from the WWTP in study. The results showed high efficiency and stability of the treatment process using Sequential Batch Reactors for domestic sewage, even with sudden changes of organic and hydraulic load, reaching more than 90% of efficiency in the removal of biodegradable organic matter. The removal of organic matter and sedimentation tests in bench reactors showed the good performance in respect of the organic matter’s removal, however, the high concentration of micro-organism results in a lower sludge sedimentation rate, which can compromise the quality of the final effluent. The relation Food/Microorganism in the conditions of the WWTP’s current operation showed a value of 0.06 gCOD/gVSS.d. and zonal sedimentation velocity of 0.59 m/h, the great ratio of the concentration of the substrate by biomass concentration, which obtained the maximum operational efficiency, showed a value of 0.09 gCOD/gVSS.d. and zonal sedimentation velocity of 1.4 m/h.

Avaliação de processo de lodos ativos por batelada seguido de tratamento terciário com ênfase na remoção de matéria orgânica e na sedimentabilidade do lodo

This paper evaluate the performance of a Wastewater Treatment Plant (WWTP) in sequential batch activated sludge modality with tertiary treatment step, located in high temperature region. It also presents the analysis of organic matter’s removal and the evaluation of sludge sedimentation conditions through reactors in bench scale, fed with different substrate’s and biomass’ concentrations, from the WWTP in study. The results showed high efficiency and stability of the treatment process using Sequential Batch Reactors for domestic sewage, even with sudden changes of organic and hydraulic load, reaching more than 90% of efficiency in the removal of biodegradable organic matter. The removal of organic matter and sedimentation tests in bench reactors showed the good performance in respect of the organic matter’s removal, however, the high concentration of micro-organism results in a lower sludge sedimentation rate, which can compromise the quality of the final effluent. The relation Food/Microorganism in the conditions of the WWTP’s current operation showed a value of 0.06 gCOD/gVSS.d. and zonal sedimentation velocity of 0.59 m/h, the great ratio of the concentration of the substrate by biomass concentration, which obtained the maximum operational efficiency, showed a value of 0.09 gCOD/gVSS.d. and zonal sedimentation velocity of 1.4 m/h.

Impianti di depurazione delle acque: SBR

In questo elaborato è stato discusso il tema della depurazione delle acque reflue, in particolar modo il sistema SBR. L'SBR (Sequencing Batch Reactors) è un sistema di impianti di depurazione composto da una vasca di raccolta del liquame e una o più vasche in parallelo, i reattori, che consistono nel vero e proprio cure dell'impianto. Di fatto le fasi del processo depurativo restano immutate rispetto ad un impianto tradizionale, ma l'SBR introduce come nuovo parametro dimensionale il tempo. infatti, tutti i trattamenti depurativi sono svolti sequenzialmente nel reattore. Un programma gestisce le varie fasi del trattamento esclusivamente sulla base della loro durata (stabilita relativamente alla natura del refluo e quindi ai trattamenti da svolgere in maniera più o meno intensiva). Questa caratteristica rende l'intero impianto molto versatile nel caso di variazioni dei dati in ingresso. Per questo motivo gli impianti SBR sono ottimi per la piccola media impresa, in quanto sono facilmente adattabili alle variazioni stagionali di produzione. Sono inoltre possibili realizzazioni di impianti per il trattamento di ingenti portate, o elevate concentrazioni, ponendo più reattori in parallelo alimentati dalle stessa vasca di accumulo. In questo modo è possibile svolgere un maggiore numero di cicli depurativi al giorno e quindi rispettare i valori normativi in uscita dell'impianto. In conclusione questa tipologia d'impianto presenta notevoli vantaggi fra i quali anche quello di avere bassi costi operativi. La motivazione di ciò sta nel fatto che l'impianto lavora solo se ha effettivamente una portata, per cui se non vi è presenza di refluo il reattore non lavora e quindi non comporta costi.

Produção de biopolímeros por culturas microbianas mistas selecionadas

Com a realização deste trabalho, pretendeu-se efetuar uma seleção de culturas mistas em reatores semi-descontínuos (SBR) com capacidade de acumulação de polihidroxialcanoatos (PHA). Para a seleção de culturas foram utilizados inóculos provenientes de diferentes Estações de Tratamento de Águas Residuais (ETAR) e ácidos orgânicos voláteis (AOV) como fonte de carbono. Foram testadas diferentes condições como a proveniência do inóculo, as cargas orgânicas aplicadas e a seleção de culturas utilizando soro de queijo. Verificaram-se elevadas remoções da CQO (acima de 90%) em grande parte dos ensaios realizados, apresentando uma acumulação de PHA por parte de algumas espécies de bactérias presentes. Ocorreu o aparecimento de microrganismos filamentosos com capacidade de acumulação de PHA em alguns ensaios, levando a serem testadas como culturas acumuladoras de PHA. A estabilidade das culturas mistas não foi atingida, mesmo havendo ensaios com 80 dias de operação. Efetuaram-se ensaios de acumulação de PHA em reatores descontínuos, utilizando as culturas selecionadas anteriormente em reatores SBR, com AOV provenientes da acidificação anaeróbia de diferentes resíduos (Fração Orgânica dos Resíduos Sólidos Urbanos - FORSU e Soro de Queijo). Verificou-se uma melhor acumulação por parte das culturas selecionadas com soro de queijo, na qual a quantidade de polímero acumulado triplicou.

SELECTED CHEMOAUTOTROPHIC PROCESSES IN WASTEWATER TREATMENT: LOW TEMPERATURE NITRIFICATION INHIBITION BY AN AZO DYE AND BIOFILTRATION FOR ODOR CONTROL OF HYDROGEN SULFIDE

Biochemical processes by chemoautotrophs such as nitrifiers and sulfide and iron oxidizers are used extensively in wastewater treatment. The research described in this dissertation involved the study of two selected biological processes utilized in wastewater treatment mediated by chemoautotrophic bacteria: nitrification (biological removal of ammonia and nitrogen) and hydrogen sulfide (H2S) removal from odorous air using biofiltration. A municipal wastewater treatment plant (WWTP) receiving industrial dyeing discharge containing the azo dye, acid black 1 (AB1) failed to meet discharge limits, especially during the winter. Dyeing discharge mixed with domestic sewage was fed to sequencing batch reactors at 22oC and 7oC. Complete nitrification failure occurred at 7oC with more rapid nitrification failure as the dye concentration increased; slight nitrification inhibition occurred at 22oC. Dye-bearing wastewater reduced chemical oxygen demand (COD) removal at 7oC and 22oC, increased i effluent total suspended solids (TSS) at 7oC, and reduced activated sludge quality at 7oC. Decreasing AB1 loading resulted in partial nitrification recovery. Eliminating the dye-bearing discharge to the full-scale WWTP led to improved performance bringing the WWTP into regulatory compliance. BiofilterTM, a dynamic model describing the biofiltration processes for hydrogen sulfide removal from odorous air emissions, was calibrated and validated using pilot- and full-scale biofilter data. In addition, the model predicted the trend of the measured data under field conditions of changing input concentration and low effluent concentrations. The model demonstrated that increasing gas residence time and temperature and decreasing influent concentration decreases effluent concentration. Model simulations also showed that longer residence times are required to treat loading spikes. BiofilterTM was also used in the preliminary design of a full-scale biofilter for the removal of H2S from odorous air. Model simulations illustrated that plots of effluent concentration as a function of residence time or bed area were useful to characterize and design biofilters. Also, decreasing temperature significantly increased the effluent concentration. Model simulations showed that at a given temperature, a biofilter cannot reduce H2S emissions below a minimum value, no matter how large the biofilter.

Preparation and assessment of immobilized laccase-based micro- and nanocatalysts for the degradation of anthropogenic compounds

Since the dawn of its presence on earth, the human being has been able to exploit the enzymes for its subsistence. More recent is the meeting between the enzymatic processes and the urgent need for technologies that aim to preserve our planet. In this field nowadays enzymatic catalysis is tested either to depollution/remediation as well as waste disposal. The work presented in this thesis, regarding both these two topics, is tailored on two European projects (EU 2020), MADFORWATER and TERMINUS respectively. Firstly, production of micro- and nanocatalysts via immobilization of laccases (a lignin-degrader enzyme) is performed. In the second part of the thesis laccase is applied to a tertiary treatment of wastewater with the aim to degrade 9 pharmaceutical active compounds in batch reactors. Despite several optimizations, poor degradation is reached and we did not proceed with the study of different bioreactor setups. Therefore, the focus is moved to a project concerning the production of smart multi-layer plastic packaging containing enzymes to improve the possibilities of recycling. In this field shielded nanocatalysts produced via coating techniques able to interact with redox mediators are investigated. The target substrate in this second project is produced in laboratory (i.e. polyurethane like compounds), starting from monomers whose degradation had already been tested, as a proof of concept. The first enzyme studied is still the laccase.

Influence of carbon sources and C/N ratio on EPS production in anaerobic sequencing batch biofilm reactors for wastewater treatment

The objective of this work was to evaluate the influence of different carbon sources and the carbon/nitrogen ratio (C/N) on the production and main composition of insoluble extracellular polymers (EPS) produced in an anaerobic sequencing batch biofilm reactor (ASBBR) with immobilized biomass in polyurethane foam. The yield of EPS was 23.6 mg/g carbon, 13.3 mg/g carbon, 9.0 mg/g carbon and 1.4 mg/g carbon when the reactor was fed with glucose, soybean oil. fat acids, and meat extract, respectively. The yield of EPS decreased from 23.6 to 2.6 mg/g carbon as the C/N ratio was decreased from 13.6 to 3.4 gC/gN, using glucose as carbon source. EPS production was not observed under strict anaerobic conditions. The results suggest that the carbon source, microaerophilic conditions and high C/N ratio favor EPS production in the ASBBR used for wastewater treatment. Cellulose was the main exopolysaccharide observed in all experimental conditions. (C) 2009 Elsevier Ltd. All rights reserved.

Post-treatment of effluents from the sulfate reduction process by anaerobic sequencing batch biofilm reactors

The main objective of this research was to evaluate the potential use of a bench-scale anaerobic sequencing batch biofilm reactor (ASBBR) containing mineral coal as inert support for removal Of Sulfide and organic matter effluents from an ASBBR (1.2 m(3)) utilized for treatment of sulfate-rich wastewater. The cycle time was 48 h, including the steps of feeding (2 h), reaction with continuous liquid recirculation (44 h) and discharge (2 h). COD removal efficiency was up to 90% and the effluents total sulfide concentrations (H(2)S, HS(-), S(2-)) remained in the range of 1.5 to 7.5 mg.l(-1) during the 50 days of operation (25 cycles). The un-ionized Sulfide and ionized sulfides were converted by biological process to elemental sulfur (S(0)) under oxygen limited conditions. The results obtained in the bench-scale reactor were used to design an ASBBR in pilot scale for use in post-treatment to achieve the emission standards (sulfide and COD) for sulfate reduction. The pilot-scale reactor, with a total volume of 0.43 m(3), the COD and total sulfide removal achieved 88% and 57%, respectively, for a cycle time of 48 h (70 days of operation or 35 cycles).

Performance of UASB reactors in two stages followed by post-treatment with activated sludge in wastewater batch of wet-processed coffee

In this study it was evaluated the efficiency of the treatment of wet-processed coffee wastewater in upflow anaerobic sludge blanket (UASB) reactors in two stages, in bench scale, followed by post-treatment with activated sludge in batch. The first UASB reactor was submitted to an hydraulic retention time (HRT) of 6.2 d and organic loading rates (OLR) of 2.3 and 4.5g CODtotal (L d)-1, and the second UASB reactor to HRT of 3.1 d with OLR of 0.4 and 1.4g CODtotal (L d)-1. The average values of the affluent CODtotal increased from 13,891 to 27,926mg L-1 and the average efficiencies of removal of the CODtotal decreased from 95 to 91%, respectively, in the UASB reactors in two stages. The volumetric methane production increased from 0.274 to 0.323L CH4 (L reactor d)-1 with increment in the OLR. The average concentrations of total phenols in the affluent were of 48 and 163mg L-1, and the removal efficiencies in the UASB reactors in two stages of 92 and 90%, respectively, and increased to 97% with post-treatment. The average values of the removal efficiencies of total nitrogen and phosphorus were of 57 to 80% and 44 to 60%, respectively, in the UASB reactors in two stages and increased to 91 and 84% with the post-treatment.

Performance of UASB reactors in two stages followed by post-treatment with activated sludge in wastewater batch of wet-processed coffee

In this study it was evaluated the efficiency of the treatment of wet-processed coffee wastewater in upflow anaerobic sludge blanket (UASB) reactors in two stages, in bench scale, followed by post-treatment with activated sludge in batch. The first UASB reactor was submitted to an hydraulic retention time (HRT) of 6.2 d and organic loading rates (OLR) of 2.3 and 4.5g CODtotal (L d)-1, and the second UASB reactor to HRT of 3.1 d with OLR of 0.4 and 1.4g CODtotal (L d)-1. The average values of the affluent CODtotal increased from 13,891 to 27,926mg L-1 and the average efficiencies of removal of the CODtotal decreased from 95 to 91%, respectively, in the UASB reactors in two stages. The volumetric methane production increased from 0.274 to 0.323L CH4 (L reactor d)-1 with increment in the OLR. The average concentrations of total phenols in the affluent were of 48 and 163mg L-1, and the removal efficiencies in the UASB reactors in two stages of 92 and 90%, respectively, and increased to 97% with post-treatment. The average values of the removal efficiencies of total nitrogen and phosphorus were of 57 to 80% and 44 to 60%, respectively, in the UASB reactors in two stages and increased to 91 and 84% with the post-treatment.

Chemical Reactors. Problem 2: Constant pressure adiabatic stirred batch reactor with variable heat capacities (2011-2012 Course)

Wording of problem 2 (week 3, 17/10/11).

Chemical Reactors. Problem 2: Constant pressure adiabatic stirred batch reactor with variable heat capacities. Solution (2011-2012 Course)

Chemical Reaction Engineering. Course 2011-12. Solution of problem 2: constant pressure adiabatic stirred batch reactor with variable heat capacities.