Microalgae community shifts during the biogas upgrading in an alkaline open photobioreactor

Aims: To achieve the functional specialization of a microalgae community through operational tuning of an open photobioreactor used for biogas upgrading under alkaline conditions. Methods and Results: An open photobioreactor was inoculated with an indigenous microalgae sample from the Texcoco Soda Lake. A microalgae community was adapted to fix CO2 from synthetic biogas through different culture conditions reaching a maximum of 220 mg CO2 l?1 per day. Picochlorum sp. and Scenedesmus sp. were identified as the prominent microalgae genera by molecular fingerprinting (partial sequencing of 16S rRNA and 18S rRNA genes) but only the first was detected by microscopy screening. Changes in the microalgae community profile were monitored by a range-weighted richness index, reaching the lowest value when biogas was upgraded. Conclusions: A robust microalgae community in the open photobioreactor was obtained after different culture conditions. The specialization of microalgae community for CO2 fixation under H2S presence was driven by biogas upgrading conditions. Significance and Impact of the Study: The alkaline conditions enhance the CO2 absorption from biogas and could optimize specialized microalgae communities in the open photobioreactor. Denaturing gradient gel electrophoresis fingerprinting and richness index comparison are useful methods for the evaluation of microalgae community shifts and photosynthetic activity performance, particularly in systems intended for CO2 removal from biogas where the CO2 assimilation potential can be related to the microbial richness

Control of dissolved CH4 in a municipal UASB reactor effluent by means of a desorption – Biofiltration arrangement

The direct anaerobic treatment of municipal wastewater represents an adapted technology to the conditions of developing countries. In order to get an increased acceptance of this technology, a proper control of dissolved methane in the anaerobic effluents should be considered, as methane is a potent greenhouse gas. In this study, a pilot-scale system was operated for 168 days to recover dissolved methane from an effluent of an upflow anaerobic sludge blanket reactor and then oxidize it in a compost biofilter. The system operated at a constant air (0.9 m3/h ±0.09) and two air-to anaerobic effluent ratio (1:1 and 1:2). In both conditions (CH4 concentration of 2.7 ± 0.87 and 4.3% ± 1.14, respectively) the desorption column recovered 99% of the dissolved CH4 and approximately 30% ± 8.5 of H2S, whose desorption was limited due to the high pH (>8) of the effluent. The biofilter removed 70% ± 8 of the average CH4 load (60 gCH4/m3h ± 13) and 100% of the H2S load at an empty bed retention time of 23 min. The average temperature inside the biofilter was 42 ± 9 °C due to the CH4 oxidation reaction, indicating that temperature and moisture control is particularly important for CH4 removal in compost biofilters. The system may achieve a 54% reduction of greenhouse gas emissions from dissolved CH4 in this particular case

Chronic coronary syndromes without standard modifiable cardiovascular risk factors and outcomes: the CLARIFY registry

Background and Aims: It has been reported that patients without standard modifiable cardiovascular (CV) risk factors (SMuRFs—diabetes, dyslipidaemia, hypertension, and smoking) presenting with first myocardial infarction (MI), especially women, have a higher in-hospital mortality than patients with risk factors, and possibly a lower long-term risk provided they survive the post-infarct period. This study aims to explore the long-term outcomes of SMuRF-less patients with stable coronary artery disease (CAD). Methods: CLARIFY is an observational cohort of 32 703 outpatients with stable CAD enrolled between 2009 and 2010 in 45 countries. The baseline characteristics and clinical outcomes of patients with and without SMuRFs were compared. The primary outcome was a composite of 5-year CV death or non-fatal MI. Secondary outcomes were 5-year all-cause mortality and major adverse cardiovascular events (MACE—CV death, non-fatal MI, or non-fatal stroke). Results: Among 22 132 patients with complete risk factor and outcome information, 977 (4.4%) were SMuRF-less. Age, sex, and time since CAD diagnosis were similar across groups. SMuRF-less patients had a lower 5-year rate of CV death or non-fatal MI (5.43% [95% CI 4.08–7.19] vs. 7.68% [95% CI 7.30–8.08], P = 0.012), all-cause mortality, and MACE. Similar results were found after adjustments. Clinical event rates increased steadily with the number of SMuRFs. The benefit of SMuRF-less status was particularly pronounced in women. Conclusions: SMuRF-less patients with stable CAD have a substantial but significantly lower 5-year rate of CV death or non-fatal MI than patients with risk factors. The risk of CV outcomes increases steadily with the number of risk factors