Browsing by Author "Paulo, A. M. S."
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- Aerobic granular sludge process treats real fish canning wastewater.Publication . Paulo, A. M. S.; Amorim, Catarina L.; Castro, P. M. L.Aerobic Granular Sludge (AGS) is an innovative technology used for carbon and nutrients removal from wastewater, using less space and energy compared to other biotechnological solutions. Aerobic granules present a compact structure, composed of extracellular polymeric substances (EPS), which increase AGS resistance to variable wastewater composition, as those commonly produced by industry. In this study, C, N and P-removal from a fish canning plant wastewater was evaluated using an AGS-SBR (sequential batch reactor). Throughout the first 3 months of operation with variable feed composition, the chemical oxygen demand (COD) at the outlet was below the discharge limit of 125 mg O2 L-1, phosphorous removal was stable and the nitrification process improved. At the higher organic loading rates (OLR), the AGS performance was temporary affected. This study contributes to understanding the effects of the variability of a real wastewater on an AGS process.
- Effect of salt on EPS production by halotolerant bacteria for aerobic granular sludge treatmentPublication . Paulo, A. M. S.; Amorim, Catarina L.; Castro, P. M. L.Extracellular polymeric substances (EPS) are overproduced by some microbes as a response to stress. The diverse composition of microbial EPS confers unique properties to these biopolymers, which find application in the food industry (e.g., thickening agents) or in the wastewater treatment (e.g., flocculants). The aerobic granular sludge (AGS) process is a promising biotechnology which relies on EPS-producing bacteria for granule formation and stability. One of the current challenges is to use the AGS process to treat high salinity wastewater. Bioaugmentation with EPS-producing halotolerant bacteria can be used as strategy to increase the robustness of AGS to high salinity. The aim of the present study was to retrieve halotolerant EPS producers from wastewater and to investigate EPS production at varying salt levels. Bacteria were isolated from brine wastewater collected in a fish canning plant. Ten isolates were compared for biofilm production (potential EPS producers) using different carbon sources and NaCl concentration (0 to 40 g L-1). Four isolates were selected for EPS production, in a medium with salt concentration up to 40 g NaCl L-1 and using saline wastewater from a fish canning plant. The EPS content in proteins, humic acids and carbohydrates was quantified. The four most promising EPS producing bacteria belonged to the Kocuria (isolate A1), Psychrobacter (isolate H3) and Acinetobacter (isolates H4 and CX1) genera. Isolate A1 was the best biofilm producer, forming more biofilm compared to the other isolates with acetate (10 g L-1) and 20 or 40 g L-1 of NaCl. In the presence of the highest salt concentration (40 g NaCl L-1), isolate A1 produced more EPS, containing a higher percentage of carbohydrates in its composition. These EPS producers are being assessed for bioaugmentation of an AGS process treating high salinity wastewater.
- Enhancement of methane production from 1-hexadecene by additional electron donorsPublication . Paulo, A. M. S.; Salvador, A. F.; Alves, J. I.; Castro, R.; Langenhoff, A. A. M.; Stams, A. J. M.; Cavaleiro, A. J.1-Hexadecene-contaminated wastewater is produced in oil refineries and can be treated in methanogenic bioreactors, although generally at low conversion rates. In this study, a microbial culture able to degrade 1-hexadecene was enriched, and different stimulation strategies were tested for enhancing 1-hexadecene conversion to methane. Seven and three times faster methane production was obtained in cultures stimulated with yeast extract or lactate, respectively, while cultures amended with crotonate lost the ability to degrade 1-hexadecene. Methane production from 1-hexadecene was not enhanced by the addition of extra hydrogenotrophic methanogens. Bacteria closely related to Syntrophus and Smithella were detected in 1-hexadecene-degrading cultures, but not in the ones amended with crotonate, which suggests the involvement of these bacteria in 1-hexadecene degradation. Genes coding for alkylsuccinate synthase alpha-subunit were detected in cultures degrading 1-hexadecene, indicating that hydrocarbon activation may occur by fumarate addition. These findings are novel and show that methane production from 1-hexadecene is improved by the addition of yeast extract or lactate. These extra electron donors may be considered as a potential bioremediation strategy of oil-contaminated sites with bioenergy generation through methane production.