Effect of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part I: biofilm growth and activity

Two similar anaerobic fixed-bed bioreactors which allowed the biomass to be periodically withdrawn were run in parallel. After feeding each digester with synthetic dairy wastes of different lipid content (Period I), both digesters were fed with increasing sodium oleate concentrations with skim milk as co-substrate (Period II) and oleate as the sole carbon source (Period III). In Period I, the digester fed with lipids was more effcient and exhibited lower levels of volatile fatty acids than the digester fed without lipids. The biofilm built up in the presence of lipids was thinner, but more resistant to the presence of oleate than the biofilm formed in the absence of lipids, which lost 53% of its solids after contacting with oleic acid. The specific methanogenic activity with butyrate as substrate was enhanced in the presence of lipids, but no significant effect was detected on the acetoclastic and hydrogenophilic activities, which remained similar for both digesters along the trial period

Effects of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part II : oleic acid toxicity and biodegradability

Oleic acid toxicity and biodegradability were followed during long-term operation of two similar anaerobic fixed-bed units. When treating an oleate based effluent, the sludge from the bioreactor that was acclimated with lipids during the first operation period, showed a higher tolerance to oleic acid toxicity (IC50=137 mg/l) compared with the sludge fed with a non-fat substrate (IC50=80 mg/l). This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methane production rates between 33 and 46 mlCH4_(STP)/gVS.day and maximum percentages of methanization between 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l. When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter, possibly oleate or an intermediate of its degradation, e.g. stearate that was degraded at a maximum rate of 99 mlCH4_(STP)/gVS.day. This suggests the possibility of using adsorption-degradation cycles for the treatment of LCFA based effluents. Both tolerance to toxicity and biodegradability of oleic acid were improved by acclimatization with lipids or oleate below a threshold concentration

Effect of lipids on biomass development in anaerobic fixed-bed reactors treating a synthetic dairy waste

The aim of this work was to follow the evolution in quantity and quality of the biomass developed during the operation of two anaerobic fixed bed reactors treating a synthetic dairy waste with different lipid contents. The feasibility of a special reactor design that allowed the biomass withdrawal with minimum operation disturbances was tested. The HRT was maintained at 1.5 days and the influent concentration was gradually increased from 3 to 12 g COD/l. Initially, one reactor was loaded with skim milk and the other one with whole milk, with equal organic loading rates (OLR). The effect of lipids was evaluated in terms of reactor performance, total, adhered and entrapped biomass and evolution of biomass quality determined in batch assays by: (i) measuring of potential specific methanogenic activity against direct (acetate, H2/CO2) and indirect (propionate and butyrate) substrates; (ii) measuring of the resistance of acetoclastic bacteria to the presence of sodium oleate. The lipids reduced the adhered fraction of biomass. The methanogenic activity against butyrate was enhanced in the presence of lipids, but no significant effect was detected on the other measured activities. The biomass taken from the reactor fed with lipids was more susceptible to the presence of sodium oleate, but, over the operation period, this susceptibility was reduced

Levantamento da situação de descarga de águas residuais industriais das empresas sediadas nos Parques Industriais de Adaúfe e Celeirós

O levantamento da situação de descarga de águas residuais industriais das empresas sediadas nos Parques Industriais de Adaúfe e Celeirós foi efectuado de Abril a Junho de 2000. A AGERE- E.M. como empresa responsável pelos sistemas de drenagem e tratamento de esgotos, demonstrou todo o interesse neste trabalho, uma vez que lhe permitiu conhecer pormenorizadamente as actividades industriais predominantes e consequentemente o tipo de efluentes produzidos. Este levantamento foi conseguido através de um trabalho de campo que englobou a visita às empresas com conhecimento directo dos seus processos produtivos. Desta forma, efectuou-se uma recolha rigorosa e exaustiva da situação quanto ao: ramo de actividade industrial, identificação e características da empresa, processo produtivo, abastecimento de água, caracterização de efluentes e ainda recolha de outros elementos que permitiram de uma forma actual, possuir um conjunto de informações importantes para o conhecimento da realidade das indústrias sediadas nestes parques

Influence of lipid acclimatization on the oleic acid toxicity towards methanogenic acetoclastic bacteria

Instituto de Biotecnologia e Química Fina (IBQF)

Influence of lipid acclimatization on the support matrix colonisation in anaerobic filters treating oleic acid

Instituto de Biotecnologia e Química Fina (IBQF)

A new method to study interactions between biomass and packing material in anaerobic filters

A new anaerobic, random-packed, fixed-bed reactor, where the fixed bed matrix is distributed between up to 36 independent mini-bioreactors, has been developed to investigate biomass-support interactions in anaerobic filters. Glass, Plexiglas and polyvinyl chloride (PVC) of three sizes all gave similar results though entrapped biomass was maximal at 3 g/L of matrix void volume for the smallest size and a maximum of 1 g adhered biomass per m2 was obtained for the largest size. In a second run, by periodically removing 3 mini-bioreactors, potential specific methanogenic activities against individual substrates were determined along the time and a continuous growth of the adhered biomass was observed, achieving a maximum of 40% of the total biomass.Comunidade Europeia - Human Capital and Mobility grant

"Bulking" filamentoso na ETAR de Braga: Análise, diagnóstico e soluções

No tratamento secundário de águas residuais o processo de lamas activadas é o mais comunmente utilizado. Este assenta no crescimento de bactérias formadoras de flocos que se separa por gravidade do sobrenadante clarificado, sendo indispensável para uma boa floculação um crescimento equilibrado entre estas bactérias e as bactérias filamentosas. Quando existe um crescimento excessivo destas últimas dá-se o fenómeno indesejado de “bulking” filamentoso. Neste trabalho procedeu-se ao estudo deste fenómeno na ETAR de Braga, tendo-se efectuado observações microscópicas das bactérias filamentosas presentes e caracterizado morfológicamente os flocos por análise de imagem. No período estudado registou-se o predomínio de M. parvicella, e após o seu desaparecimento dos tipos 1851, 1863 e N. limicola I e II. Verificou-se ainda que o “bulking“ filamentoso aparenta ser um problema “crónico” nesta estação de tratamento, principalmente devido ao elevado crescimento das espécies encontradas.Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI/BD/20325/99