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Performance of a fungal monolith bioreactor for the removal of styrene from polluted air

  • Rene, Eldon R.
  • López, M. Estefanía
  • Veiga, María Carmen
  • Kennes, Christian
Gas-phase styrene removal using the fungus, Sporothrix variecibatus was evaluated in a novel monolith bioreactor, receiving a continuous supply of nutrients from the trickling liquid phase. During the start-up process, the monolith reactor was operated for 22 days with relatively low styrene concentrations in the gas-phase (<0.4 g m−3). Afterwards, continuous experiments were carried out at different inlet styrene concentrations, ranging between 0.06 and 2.5 g m−3, and at two different flow rates corresponding to empty bed residence times (EBRTs) of 77 and 19 s, respectively. A maximum elimination capacity of 67.4 g m−3 h−1 was observed at an inlet styrene load of 73.5 g m−3 h−1. However, it was observed that the critical loading rates to the monolith bioreactor were a strong function of the gas residence time. The critical load, with greater than 95% styrene removal was 74 g m−3 h−1 at an EBRT of 77 s, while it was only 37.2 g m−3 h−1 for an EBRT of 19 s. After 92 days of continuous operation, due to excess biomass growth on the surface of the monolith, the biodegradation efficiency decreased significantly. To ascertain the instantaneous response of the attached fungus, to withstand fluctuations in loading conditions, two dynamic shock loads were conducted, at EBRTs of 77 and 19 s, respectively. It was observed that, the performance of the monolith bioreactor decreased significantly at low residence times, when subjected to high shock loads. The recovery times for high performance, in both cases, did not exceed more than 1 h.
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Two-liquid-phase mesophilic and thermophilic biotrickling filters for the biodegradation of α-pinene

  • Montes, María
  • Veiga, María Carmen
  • Kennes, Christian
α-Pinene biodegradation was evaluated in mesophilic and thermophilic biotrickling filters. The potential of silicone oil for enhancing the removal was evaluated too, at both temperatures. Performance was studied at empty bed residence times between 60 and 14 s, and concentrations of 0.06–38.84 g m−3, with or without silicone oil. Efficiency decreased as the pollutant concentration was increased, showing higher elimination capacities at higher EBRTs. In the absence of silicone oil, better results were obtained in the thermophilic than in the mesophilic bioreactor. At similar loads (360 g m−3 h−1), in the thermophilic bioreactor the elimination capacity was 293 g m−3 h−1, with a removal efficiency of 81%, while in the mesophilic BTF the elimination capacity only reached 195 g m−3 h−1, for that same load. The presence of a second liquid phase improved performance of both bioreactors. With 5% silicone oil, elimination capacities as high as 2000 g m−3 h−1 were achieved, under either mesophilic or thermophilic conditions.
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Biodegradation of gas-phase styrene using the fungus Sporothrix variecibatus: Impact of pollutant load and transient operation

  • Rene, Eldon R.
  • Veiga, María Carmen
  • Kennes, Christian
Biofiltration of gas-phase styrene was studied using a newly isolated fungus Sporothrix variecibatus, in a perlite biofilter, at inlet concentrations and gas-flow rates ranging from 0.13 to 14 g m−3 and 0.075 to 0.34 m3 h−1, respectively, corresponding to empty bed residence times (EBRT) ranging between 91 and 20 s. Styrene loading rates were varied between 50 and 845 g m−3 h−1and a maximum elimination capacity of 336 g m−3 h−1 was attained with nearly 65% styrene removal. On the other hand, the critical inlet loads to achieve more than 90% removal were 301, 240 and 92 g m−3 h−1 for EBRT of 91, 40, and 20 s, respectively. In order to test the stability and shock bearing capacity of the fungal biofilter, short-term tests were conducted by suddenly increasing the gas-phase styrene concentration, while maintaining the gas-flow rate constant. The response, a restoration in the removal performance to previous high values, after subjecting the biofilter to shock loads proves the resilient nature of the attached Sporothrix sp. and its suitability for biofiltration under non-steady state conditions.
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Biofiltration of mixtures of gas-phase styrene and acetone with the fungus Sporothrix variecibatus

  • Rene, Eldon R.
  • Špačková, Radka
  • Veiga, María Carmen
  • Kennes, Christian
The biodegradation performance of a biofilter, inoculated with the fungus Sporothrix variecibatus, to treat gas-phase styrene and acetone mixtures under steady-state and transient conditions was evaluated. Experiments were carried out by varying the gas-flow rates (0.05–0.4 m3 h−1), leading to empty bed residence times as low as 17.1 s, and by changing the concentrations of gas-phase styrene (0.01–6.3 g m−3) and acetone (0.01–8.9 g m−3). The total elimination capacities were as high as 360 g m−3 h−1, with nearly 97.5% removal of styrene and 75.6% for acetone. The biodegradation of acetone was inhibited by the presence of styrene, while styrene removal was affected only slightly by the presence of acetone. During transient-state experiments, increasing the overall pollutant load by almost 3-fold, i.e., from 220 to 600 g m−3 h−1, resulted in a sudden drop of removal efficiency (>90–70%), but still high elimination capacities were maintained. Periodic microscopic observations revealed that the originally inoculated Sporothrix sp. remained present in the reactor and actively dominant in the biofilm.
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Steady- and transient-state operation of a two-stage bioreactor for the treatment of a gaseous mixture of hydrogen sulphide, methanol and α-pinene

  • Rene, Eldon R.
  • López, M. Estefanía
  • Veiga, María Carmen
  • Kennes, Christian
A two-stage bioreactor, comprising a biotrickling filter (BTF) as the first stage and a biofilter (BF) as the second stage, operated under steady- and transient-state conditions, was tested to remove gas-phase hydrogen sulphide, methanol and α-pinene. RESULTS: Hydrogen sulphide and methanol were removed in the first stage, while α-pinene, was removed predominantly in the second-stage fungal BF. The effect of the liquid trickling rate was evaluated in the BTF, while concentration-dependent synergistic and antagonistic interactions in both reactors were assessed by varying the concentration of one pollutant, and by maintaining 100% removal of other pollutants. Increasing the liquid trickling rate decreased methanol removal significantly, from > 93% to 40%. Increasing the concentration of hydrogen sulphide from low to high loading rates did not affect the removal of volatile organic compounds (VOCs), however, the reverse occurred. Under all the conditions tested, α-pinene removal in the second-stage biofilter still remained higher than 80%. CONCLUSIONS: The results show the maximum elimination capacities achievable for this complex ternary mixture, under a wide range of operating conditions.
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The SHARON process in the treatment of landfill leachate

  • Vilar, A.
  • Eiroa, M.
  • Kennes, Christian
  • Veiga, María Carmen
The purpose of this paper was to study the partial nitrification of the nitrogen present in a landfill leachate applying the SHARON process in order to obtain a suitable effluent to the ANAMMOX process. As a first step, the SHARON reactor was fed anaerobically pre-treated leachate at an ammonium concentration of 2,000 mg N/L (1.1 kg N/m3 d). In such conditions, the average ammonium and nitrite concentrations in the effluent were 775 mg N/L and 1,225 mg N/L, respectively. During this period the COD removal was very low since most of the biodegradable organic matter was removed in the anaerobic pre-treatment. Afterwards, the SHARON reactor was fed leachate without a previous treatment and the efficiency of the partial nitritation diminished. As well, the COD removal increased, achieving a percentage around 28%.
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Valuable product production from wood mill effluents

  • Mato, T.
  • Ben García, Marta
  • Kennes, Christian
  • Veiga, María Carmen
Fibreboard production is one of the most important industrial activities in Galicia (Spain). Great amounts of wastewater are generated, with properties depending on the type of wood, treatment process, final product and water reusing, among others. These effluents are characterized by a high chemical oxygen demand (COD), low pH and nutrients limitation. Aerobic and anaerobic processes have been used for their treatment. Presently, bioplastics production (mainly polyhydroxyalkanoates or PHA) from wastewaters with mixed cultures is being studied. Substrate requirements for these processes are a high organic matter content and low nutrient concentration. Therefore, wood mill effluents could be a suitable feedstock. PHA production from wastewaters is carried out in three steps. First, complex organic matter is converted into volatile fatty acids (VFA) through acidogenic fermentation. Then, VFA are used as substrate in an aerobic sequencing batch reactor (SBR), in which the enrichement of PHA producing bacteria from a mixed culture is favoured. Finally, the sludge from the SBR is fed with a pulse containing high VFA concentrations, resulting in PHA accumulation inside the cells. In this work, the possibility of applying this process to wood mill effluents is proposed. An acidification percentage of 37% and a storage yield (YSTO) of 0.23 Cmmol/Cmmol were obtained.
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Fluorescence study of tetracaine–cyclodextrin inclusion complexes

  • Iglesias García, Iván.
  • Brandariz, Isabel
  • Iglesias, Emilia
The steady-state fluorescence emission from the local anaesthetic tetracaine (TCA) in water-solvent mixtures and in the presence of α-, β- and γ-cyclodextrin (CD) was investigated at various pH values. Emission was observed from the locally and the intramolecular charge transfer excited states. The TCA-CD system was found to be characterised by 1:1 associate in every case. The association constants of each complex were determined., Ministerio de Educación y Ciencia; CTQ2005-07428/BQU, Ministerio de Ciencia e Innovación; CTQ2008-04429/BQU
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Mental and psychological conditions, medical comorbidity and functional limitation: differential associations in older adults with cognitive impairment, depressive symptoms and co-existence of both

  • Millán-Calenti, José Carlos
  • Maseda, Ana
  • Rochette, Sophie
  • Vázquez, Gustavo A.
  • Sánchez, Alba
  • Lorenzo, Trinidad
[Abstract] Objective: Cognitive impairment and depressive symptoms are common among the geriatric population but the co-occurrence of both is rarely studied. The purpose of this study was to identify and compare the factors associated with three groups of elderly people: those assessed with cognitive impairment alone (COG), depressive symptoms alone (DEP) or co-existence of both (COG-DEP). Methods: The cross-sectional study included 600 community-dwellers ages 65 and older. All participants underwent a comprehensive evaluation. Global cognition was measured by the Mini-Mental State Examination (MMSE) and depressive symptoms were defined by the Geriatric Depression Scale (GDS). Specific chronic illnesses relevant to the Charlson comorbidity index (CCI) were self-reported. Functional status was evaluated by the Katz’ basic (ADL) and Lawton’s instrumental (IADL) activities of daily living scales. Results: COG-DEP was explained by IADL dependence (OR: 11.9, 95% CI: 4.59–30.78), ADL dependence (OR: 11.5, 95% CI: 5.59–23.69), cerebrovascular disease (OR: 3.6, 95% CI: 1.48–8.68), congestive heart failure (OR: 3.4, 95% CI: 1.77–6.59) and diabetes (OR: 2.6, 95% CI: 1.30–5.18), but it was best predicted by functional limitations in the adjusted model. Being functionally dependent and medically ill with shorter life expectancy was shown to significantly increase the odds of being DEP. Functional limitation in IADL was without distinction associated to COG, DEP and COG-DEP. Conclusion: The present results on COG, DEP and COG-DEP show the particular relevance of certain medical comorbidities and functional limitations to those three distinct groups of elderly people.
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Reliability of 4-m and 6-m walking speed tests in elderly people with cognitive impairment

  • Muñoz-Mendoza, Carmen L.
  • Cabañero-Martínez, M. José
  • Millán-Calenti, José Carlos
  • Cabrero-García, Julio
  • López-Sánchez, Rosalía
  • Maseda, Ana
[Abstract] The purpose of this study was to evaluate the interrater and test–retest reliability of 4-m and 6-m walking speed tests in elderly people with cognitive impairment. 50 subjects aged 65 and over with cognitive impairment were selected from an adult day-care centre and a nursing home. To examine interrater reliability, 21 people were evaluated independently by two researchers who administered the 4-m and 6-m walking tests in each evaluation. For test–retest reliability, two observers administered the tests to the same 29 subjects, with a time interval of one week. Intraclass correlation coefficients (ICCs) were calculated to examine interrater and test–retest reliability. The ICCs for interrater reliability reached values of 0.96 and 0.88 for the 4-m and 6-m walking tests, respectively. In the test–retest study, the time interval was 7.4 1.17 days. The ICCs were 0.91 for the 4-m test and 0.86 for the 6-m test. The results support the use of walking tests in elderly people with cognitive impairment.
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