Demethanization of aqueous anaerobic effluents using a polydimethylsiloxane membrane module: Mass transfer, fouling and feasibility

The performance, fouling and feasibility of a polydimethylsiloxane hollow fibre membrane module for in situ methane degasification from the effluent of an Expanded Granular Sludge Bed anaerobic reactor has been investigated. Experiments at different operational conditions were carried out (liquid flow, sweep gas flow and vacuum pressure) with maximum removal efficiency (77%) at lowest flow-rate (0.4 L h-1), highest vacuum gauge pressure (-800 mbar) and liquid flowing in lumen side. Mass transport analysis denoted a considerably higher methane transfer than that predicted (attributed to liquid over- saturation). An enhancement factor for liquid phase has been proposed to correlate the experimental results. Long-term experiments were also performed in order to determine the possible influence of fouling on the module performance, and it showed that relatively frequent cleaning with water might be carried out to ensure preservation of the membrane efficiency. Characterization of water quality before and after membrane module was carried out to elucidate fouling causes. Energy balance analysis evidenced that energy production exceeded the system energy requirements. A substantial reduction of CO2 equivalent emissions showed the positive environmental impact of this technology

Start-Up of Chitosan-Assisted Anaerobic Sludge Bed Reactors Treating Light Oxygenated Solvents under Intermittent Operation

Quality of the granular sludge developed during the start-up of anaerobic up-flow sludge bed reactors is of crucial importance to ensure the process feasibility of treating industrial wastewater such as those containing solvents. In this study, the microbial granule formation from suspended-growth biomass was investigated in two chitosan-assisted reactors. These reactors operated mimicking industrial sites working with night closures treating a mixture of ethanol, ethyl acetate, and 1-ethoxy-2-propanol. Each reactor operated under different hydrodynamic regimes typical from UASB (R1: 90%) accompanied by rapid formation of robust anaerobic granules were achieved at both up-flow velocity levels. After three weeks from the start-up, mean size diameters of 475 µm and 354 µm were achieved for R1 and R2, respectively. The performance of the process was found to be stable for the whole operational period of 106 days treating intermittent OLR up to 13 kg COD m−3 d−1. A memory dose of chitosan at day 42 was beneficial to guarantee good quality of the granules by offsetting the negative impact of intermittent water supply on the granular size. Methanocorpusculum was identified as the dominant archaea at both up-flow velocities. Acetobacterium, Geobacter and Desulfovibrio bacteria were also abundant, demonstrating its role on the degradation of light-oxygenated solvents

Gender diversity in STEM disciplines: a multiple factor problem

Lack of diversity, and specifically, gender diversity, is one of the key problems that both technological companies and academia are facing these days. Moreover, recent studies show that the number of female students enrolled in science, technology, engineering and mathematics (STEM) related disciplines have been decreasing in the last twenty years, while the number of women resigning from technological job positions remains unacceptably high. As members of a higher education institution, we foresee that working towards increasing and retaining the number of female students enrolled in STEM disciplines can help to alleviate part of the challenges faced by women in STEM fields. In this paper, we first review the main barriers and challenges that women encounter in their professional STEM careers through different age stages. Next, we focus on the special case of the information theory field, discussing the potential of gendered innovation, and whether it can be applied in the Information Theory case. The working program developed by the School of Engineering at the University of Valencia (ETSE-UV), Spain, which aims at decreasing the gender diversity gap, is then presented and recommendations for practice are given. This program started in 2011 and it encompasses Bachelor, Master and PhD levels. Four main actions are implemented: Providing institutional encouragement and support, increasing the professional support network, promoting and supporting the leadership, and increasing the visibility of female role models. To assess the impact of these actions, a chi-square test of independence is included to evaluate whether there is a significant effect on the percentage of enrolled female students. The percentage of graduated female students in the information and Communications Technology Field is also positioned with respect to other universities and the Spanish reference value. This analysis establishes that, in part, this program has helped to achieve higher female graduation rates, especially among Bachelor students, as well as increasing the number of top-decision positions held by faculty women

Intermittent operation of UASB reactors treating wastewater polluted with organic solvents: process performance and microbial community evaluation

The effect of intermittent feeding on the treatment of wastewater polluted with ethanol, ethyl acetate and 1-ethoxy-2-propanol in anaerobic upflow sludge blanket reactors was investigated. Three laboratory-scale reactors, one periodically supplemented with chitosan, were operated in an intermittent pattern (16 hours per day; 5 days per week) during 5 months. Removal efficiencies higher than 94% were obtained at organic loading rates up to 50 kg COD m−3 d−1. The addition of chitosan positively affected the specific methanogenic activity of the granular sludge. Although partial deterioration of the granules was observed, it was not correlated with variations in the production of extracellular polymeric substances, the percentage of granules remained between 57 and 84%. Microbial community analysis showed the prevalence of bacteria of the genus Geobacter and archaea of the Methanocorpusculum genus were the most abundant methanogens, suggesting that hydrogenotrophic methanogenesis, with the syntrophic oxidation of the substrate, was an important pathway for solvent degradation

Towards breaking the Gender Gap in Science, Technology, Engineering and Mathematics

The gender gap in Science, Technology, Engineering and Mathematics (STEM) has drawn the attention of research and academic communities due to its impact in the Digital Society, targeting the fourth and fifth 2030 sustainable development goals of achieving quality education and gender equality. Recent studies show that women are enrolling STEM studies in smaller proportion than men and that they have a larger probability to renounce to their jobs or to take leaves. In this scenario, the involvement of educational institutions is seminal to change this trend. The School of Engineering of the University of Valencia (ETSE-UV), Spain, launched in 2011 a pilot program to promote STEM careers, focusing on increasing and retaining the number of female students choosing these studies. Building from this experience, the Girls4STEM project has been launched in 2019 with the aim of reaching female students from 6 to 18 years old, their families and teachers. In this paper, we present and motivate the project's objectives and main activities, framing them in current state of the art's literature. Preliminary results of the pilot program actions are presented, demonstrating the statistically significant impact on the percentage of enrolled female students and motivating the subsequent Girls4STEM project

Comparison of simultaneous saccharification and fermentation and separate hydrolysis and fermentation processes for butanol production from rice straw

Rice straw (RS) is one of the lignocellulosic wastes with the highest global production. The main objective of this study was to maximise the butanol production by Clostridium beijerinckii DSM 6422 from RS pretreated by microwave-assisted hydrothermolysis. Two different fermentation strategies were compared: separate hydrolysis and fermentation (SHF, two-step process) and simultaneous saccharification and fermentation (SSF, one-step process). In parallel, the variables that significantly affected the butanol production were screened by using fractional factorial designs. Butanol concentration and productivity at 48 h were, respectively, 8% and 173% higher in SSF than in SHF. A one-step process was more efficient than a two-step process, especially considering the time savings derived from much higher productivity. From these results, SSF was further optimised by response surface methodology with central composite design over the key factors on the butanol production at 48 h: initial pH, enzyme loading and yeast extract concentration. The optimum point yielded a butanol productivity of 0.114 g L-1h−1, with a butanol-biomass ratio of 51 g kg−1 of raw RS (ABE-biomass ratio of 77.0 g kg−1 of raw RS). The parameter with the greatest effect was enzyme loading, with an optimal value of 13.5 FPU g-dw-1. This study showed that microwave-processed RS has great potential as a substrate for the butanol production from ABE fermentation when combining process stages by SSF

Performance and feasibility of biotrickling filtration in the control of styrene industrial air emissions

The performance and feasibility of a pilot unit of biotrickling filter (BTF) for the treatment of industrial emissions polluted by styrene was investigated for one year at a fiber reinforced plastic industrial site. The pilot unit was packed with a structured material with a volume of 0.6 m3. Monitoring results have shown successful treatment of the industrial styrene emissions working at empty bed residence times (EBRT) between 31 and 66 s. The best performance was obtained after 300 days when a more stable biofilm had been developed, obtaining the highest elimination capacity of 18.8 g m−3 h−1 (removal efficiency of 75.6%) working at 31 s of EBRT. In addition, a photocatalytic reactor was evaluated as pretreatment of the biological process, but results have shown very low capacity for improving the BTF performance due to catalyst deactivation. The economic feasibility of the BTF was evaluated. The total direct cost, excluding capital recovery, of the biotrickling filter technology was estimated in 0.71 year−1 per Nm3 h−1 of treated air whereas 2.27 year−1 per Nm3 h−1 was obtained for the regenerative catalytic oxidizer equipped with a zeolite pre-concentrator. Results show that this technology is economically and environmentally competitive in comparison with thermal treatment

Microbial community analysis in biotrickling filters treating isopropanol air emissions

The evolution of the microbial community was analysed over one year in two biotrickling filters operating under intermittent feeding conditions and treating isopropanol emissions, a pollutant typically found in the flexography sector. Each reactor was packed with one media: plastic cross-flow-structured material or polypropylene rings. The communities were monitored by fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA region. After inoculation with activated sludge, the biotrickling filters were operated using inlet loads (ILs) from 20 to 65gCm−3 h−1 and empty-bed residence times (EBRTs) from 14 to 160 s. Removal efficiencies higher than 80% were obtained with ILs up to 35gCm−3 h−1 working at EBRTs as low as 24 s. There was an increase in the total percentage of the target domains of up to around 80% at the end of the experiment. Specifically, the Gammaproteobacteria domain group, which includes the well-known volatile organic compound (VOC)-degrading species such as Pseudomonas putida, showed a noticeable rise in the two biotrickling filters of 26% and 27%, respectively. DGGE pattern band analysis revealed a stable band of Pseudomonas putida in all the samples monitored, even in the lower diversity communities. In addition, at similar operational conditions, the biotrickling filter with a greater relative abundance of Pseudomonas sp. (19.2% vs. 8%) showed higher removal efficiency (90% vs. 79%). Results indicate the importance of undertaking a further in-depth study of the involved species in the biofiltration process and their specific function

Girls4STEM: gender diversity in STEM for a sustainable future

Science, Technology, Engineering, and Mathematics (STEM) are key disciplines towards tackling the challenges related to the Sustainable Development Goals. However, evidence shows that women are enrolling in these disciplines in a smaller percentage than men, especially in Engineering related fields. As stated by the United Nations Women section, increasing the number of women studying and working in STEM fields is fundamental towards achieving better solutions to the global challenges, since the potential for innovation is larger. In this paper, we present the Girls4STEM project, which started in 2019 at the Escola Tècnica Superior d'Enginyeria de la Universitat de València, Spain. This project works towards breaking the stereotypes linked to STEM fields, addressing both boys and girls aged from 6 to 18, but especially trying to open the range of career options for young girls through interaction with female STEM experts. The goal is to spark girls' interest in STEM disciplines from childhood, so that they become more self-confident in these areas. To achieve this goal, the project is built over three main actions: the Girls4STEM Family Talks, where students, families, and teachers participate; the Girls4STEM Professional Talks, where the target is a general audience; and the Initial Training Seminars for teachers. Short-term results are here presented, showing that aspects related to self-perception and perception from others (family, teachers) play a significant role. Moreover, these results also indicate that there may not be a general understanding of which disciplines are included in STEM

Fermentation of municipal primary sludge: effect of SRT and solids concentration on volatile fatty acid production

Laboratory bench-scale experiments were conducted to investigate the performance of primary sludge fermentation for volatile fatty acids production. Primary sludges from two major wastewater treatment plants located in Valencia (Pinedo and Carraixet) were used. Experiments were performed at solids retention times between 4 and 10 days, and total volatile solids concentrations between 0.6 % and 2.8 %. Operation at two temperatures (20°C and 30°C) was also checked. Results indicated the importance of feed sludge characteristics on volatile fatty acids yields, being approximately double for the Carraixet wastewater treatment plant sludge than for the Pinedo plant. In both cases, higher volatile fatty acids yields were observed at higher total volatile solids concentrations. Solids retention times above 6 days scarcely improve volatile fatty acids yields, while experiments conducted at 4 days of solids retention times show an important decrease in volatile fatty acids yields. On raising temperature an increase in volatile fatty acids yields was observed, mainly due to an improvement in the hydrolysis of particulate organic matter