This study evaluates the dynamic membrane build-up of a nitrifying aerobic membrane bioreactor operated at high fluxes. The process achieved complete nitrification and a marked reduction in organic load. The build-up of the dynamic membrane was evaluated under different filtration fluxes (50-400 L/hm2). The effect of particle content and different cleaning strategies were also assessed. Results show that filtration flux has no influence on the initial construction of the dynamic membrane or on effluent quality, which achieves acceptable turbidity levels for its reuse in less than four minutes. However, operation at high fluxes does lead to cake layer compaction in shorter operating times. Metabolite content is key to the formation of dynamic membranes, but without the presence of particles, the separation efficiency of the dynamic membrane is reduced. Results also indicate that air-backwashing is the best physical cleaning strategy among those tested, as it removes some of the pore-blocking material and enables longer filtration times between cleanings. In addition, the off-spec product time is less than one minute after each cleaning.

The combination of anaerobic and membrane photobioreactor (MPBR) technologies has generated interest as a sustainable strategy for domestic wastewater treatment. The former allows lower sludge production than aerobic technologies and energy recovery through biogas production, while MPBRs act as an advanced secondary effluent treatment. This study shows the effects of the light photoperiod on the suspension characteristics and overall performance of bench-scale MPBRs applied to an advanced secondary effluent treatment of a pilot upflow anaerobic sludge blanket (UASB). The results of the experimental runs showed the key role played by light incidence on the organisms developed and consequently on wastewater recovery performance and membrane fouling. The two light/dark photoperiods tested (9/15 h and 12/12 h) resulted in similar values for regeneration performance and membrane fouling. However, the longer photoperiod promoted a more sustainable process of nitrogen conversion associated with photosynthetic activity. In addition, longer daylight hours contributed to membrane performance characterized by more easily removable fouling using physical cleaning methods and with less residual character. Consequently, the tested technology can further improve performance in terms of long-term membrane operation and contributes to the design of an overall sustainable process.

Integrating anaerobic processes, such as the Upflow Anaerobic Sludge Blanket (UASB) reactor, with membrane photobioreactors (MPBRs) represents a significant advance in wastewater treatment, combining effective water purification, biogas production, and the generation of recoverable biomass. Short-term and long-term experiments comparing MPBR reactors with intermittent and continuous membrane rotation were evaluated to assess their effectiveness in fouling control and nutrient recovery. These configurations were also compared with a rotative membrane bioreactor (MBR) which revealed the superior performance of MPBRs in managing membrane fouling and nutrient removal. MPBR reactors surpassed the conventional MBR in permeate quality, nutrient recovery rates referred to as NRR and PRR for nitrogen and phosphorous, respectively (MPBR-I: NRR 9.2 f 3.2 mg/L center dot d and PRR 0.8 f 0.3 mg/L center dot d; MPBR-II: NRR 7.9 f 1.7 mg/L center dot d, PRR 0.4 f 0.2 mg/L center dot d), but also biomass production, indicating great potential for bioproduct recovery applications. Moreover, the continuous rotation implemented in the MPBR led to a significant reduction in fouling by enhancing particle dispersion, mitigating the negative effects of soluble microbial products, maintaining higher critical flux values, and achieving lower hydraulic resistance, despite increased carbohydrate levels due to shear-induced stress on microalgae. Although physical cleaning methods effectively removed over 90 % of fouling, highlighting its reversible nature and benefits for membrane longevity, MPBRs required stronger chemical treatments due to persistent biofilm adhesion. Therefore, an integrated approach combining rotation and chemical cleaning could effectively address current wastewater treatment needs and providing a replicable and sustainable model, emphasizing resource recovery, waste minimization, and long-term operational efficiency.

Anthropogenic microparticles, including natural and semisynthetic cellulosic textile fibres and microplastics, are generated globally as by-products of human activities and enter the environment mainly via wastewater. Wastewater treatment plants (WWTPs) play a crucial role in reducing these pollutants, thereby improving water quality and supporting planetary health. This study evaluates the concentration, variability, and characteristics of such particles across different stages of an urban WWTP in Tenerife (Canary Islands, Spain) equipped with a membrane bioreactor (MBR) and reverse electrodialysis (RED), and further examines their correlations with physicochemical water parameters and environmental factors. Monthly fieldwork in 2023 involved triplicate sampling at six WWTP points and reclaimed water supplied at a banana farm for crops irrigation. A total of 252 samples were generally submitted to an oxidative digestion, filtered, and the resulting anthropogenic particles (n = 12,847 items) were analysed using stereomicroscopy and Fourier transform infrared microspectroscopy (n = 1124 items). Particles ranged from 50 to 6607 μm and were categorised into fibres, fragments, films, and microbeads, with fibres accounting for over 60 % at all stages. Average concentrations were 926 ± 438, 2342 ± 658, and 43 ± 43 items/L in the influent, biological reactor, and final effluent, respectively. Composition analyses revealed 21 polymers in the influent but only 4 in the final effluent, with cellulosic fibres always being the predominant type. Time-dependent analyses showed higher particle loads in warmer months, yet an average retention of 95 % highlighted the efficacy of the system in reducing harmful microplastics pollution.

Chemical engineering is a consolidated discipline in Spain with bachelor's degrees in 36 universities. An analysis of main indicators related to chemical engineering undergraduate enrolment has been performed, since the introduction of academic programs according to Bologna principles (2010-2011). Indicators present a wide variety of values across the country depending on the characteristics of universities (size of university and city, presence of industry, etc.). The number of first-year students has remained stable during last years, but a decrease in the number of graduates and students enrolled with chemical engineering as their preferred choice is observed, suggesting a decline in the interest of students in pursuing chemical engineering. This decline may be due not only to the general declining interest of students in science and technology, but also to the low recognition of chemical engineering in Spanish society. Possible causes of this low recognition of chemical engineering in Spain are outlined.

Dynamic membrane technology has recently been investigated for wastewater treatment due to its reduced installation and operating costs compared to conventional membrane systems. However, it has been little studied in combination with photobioreactors, which provide efficient nutrient removal. This study investigates the feasibility of dynamic membrane photobioreactors for the secondary treatment of domestic wastewater. A laboratory unit equipped with a nylon module was tested using a mixed culture of microalgae-bacteria, which removed 93% and 76% of phosphorus and nitrogen, respectively. However, the dynamic membrane build-up on the support layer shows non-uniform growth, a compact structure with low permeability and is not able to effectively separate the suspension from the effluent.

Membrane photobioreactors (MPBRs) combine ultrafiltration membranes and phototrophic-heterotrophicnitrifying culture growth in an interesting process for wastewater treatment that promotes the circular economy. This technology has been investigated to improve the reclamation process of primary and secondary effluents from real domestic wastewater treatment facilities. Microorganism cultures were developed in lab-scale reactors from indigenous microbial consortium under various operating conditions. Culture samples from stable biological suspensions and several strains of heterotrophic nitrification-aerobic denitrification bacteria and fungi were isolated. A total of 140 viable strains of microorganisms were identified and associated with physical-chemical properties of the feedwater and suspensions but also, with the operational conditions, to identify differences in structural composition of the developed consortia. The bacterial community exhibited significantly higher abundance and richness compared to the fungi and plantae communities, encompassing a total of 12 phyla and 43 genera. Proteobacteria were the most dominant phylum, with relative abundances of 71 % and 69 %, respectively. However, the genus composition varied greatly among the different treatments. According to diversity measurements, all suspensions fed with secondary effluents exhibited significantly lower richness, abundance, and diversity than those cultivated with primary effluents. The main factor influencing microbial community composition was the C/N ratio for most secondary effluents, whereas the ammonium-nitrogen loading rate was determinant for primary effluents.

Hydrotalcites have been investigated as adsorption systems for water treatment. However, there is a notable gap in the literature regarding studies analyzing their simultaneous removal of ammonium and phosphate pollutants. This work presents an analysis of the ammonium and phosphate adsorption process in real wastewater by commercial hydrotalcite calcined at different temperatures. In addition, an analysis of the effect of co-ions in the medium is performed, studying synergies and interferences between them. Optimal nutrient adsorption is achieved by calcining the adsorbent at 550 degrees C, facilitating a crystalline restructuring toward a spinel structure. During adsorbent hydration, the chemical memory effect allows phosphate to be incorporated into the interlamellar space, while ammonium is adsorbed mainly by electrostatic attraction when the zero-charge point is exceeded. The alkaline nature of water decreases adsorption capacities due to interference with the adsorbent's crystalline reestablishment process and a buffer effect. The latter effect favors the loss of magnesium from the adsorbent, which results in a lower phosphate adsorption capacity. By contrast, calcium in the medium improves phosphate adsorption but inhibits ammonium adsorption. In real wastewater, the removal performance of phosphate and ammonium reached 90 and 50%, respectively, with standardized doses of 150 mgads/mg PO43- and 80 mgads/mg N-NH4+.

CRAFT BREWING AS AN INNOVATIVE LEARNING ACTIVITY FOR CHEMICAL ENGINEERING STUDENTS IN UNIVERSIDAD DE LA LAGUNA

Compressible cake formation in membrane bioreactors, a key fouling mechanism in domestic wastewater reclamation, results from the deformable nature of foulants. This study investigates the combined impact of air scouring, shear stress, and consolidated residual fouling on compressible cake formation. A simple mathematical model is proposed that describes the net stress of attracted material on the membrane with a convective shear transport flux, which is dependent on applied shear stress and consolidated residual fouling. The convective flux is linked to the threshold flux, providing a straightforward relationship between step flux trials and cake formation. Results indicate that residual fouling reduces the effectiveness of membrane aeration and accelerates cake build-up. In addition, the cake's specific resistance decreases exponentially with the net attractive force of materials during its accumulation, influencing the compressibility coefficient. The proposed model identifies a threshold net material attraction flux, allowing fouling without exceeding an acceptable compressibility level.

Coupling cultivation and harvesting systems remain a challenge in scaling up microalgae-based technologies for wastewater reclamation. The integration of membranes offers alternative process configurations, but effective filtration control is required for sustainable operation. To overcome these issues, this study proposes a novel vertical upflow multi-column configured membrane photobioreactor (VUC-MPBR). In addition, a feedback control system was used to enhance filtration performance, in which the permeate flux was dynamically optimized by controlling filtration time within the filtration cycle. A pilot-scale unit (456 L) was constructed with five vertically arranged columns connected in parallel with a membrane tank for suspension recirculation. It was run outdoors for over 175 days treating secondary wastewater effluent. The upflow mode of operation enhanced solid separation, via sedimentation, which maintained the recirculating suspension at low concentrations (0.14-0.55 g/L). Furthermore, concentrated biomass reached 15.0-15.4 g/L at the bottom of the columns. COD and N-NH4+ removal efficiencies ranging from 48 % to 75 % and from 97 % to 98 % were recorded, respectively. This process configuration permitted stable operation at moderate supra-threshold flux (25.6 L/h m2) by using a conventional filtration strategy. This performance was further improved when a feedback control system was applied. Under optimal environmental conditions, continuous operation at large supra-threshold fluxes (50.6 +/- 4.5 L/h m2) was achieved for over 500 h at low specific aeration demands (op = 6.6 +/- 0.8 Nm3air/m3permeate). This study, shows that the VUC-MPBR can enhance filtration performance and biomass harvesting, thus representing an alternative process configuration for microalgae-based wastewater reclamation.

Anaerobic and membrane technologies are a promising combination to decrease the energy consumption associated with wastewater treatment, allowing the recovery of resources: organic matter as biomethane, nutrient assimilation by microalgae and reclaimed water. In this study, domestic wastewater was treated using a combination of an upflow anaerobic sludge blanket sludge reactor (UASB) and a membrane photobioreactor (MPBR). The outdoor facilities were operated continuously for three months under unfavourable environmental conditions such as lack of temperature control, winter season with lower solar irradiation and lower daylight hours which was a challenge for the present work, not previously described. The energetic valorisation of the organic matter present in the wastewater by biomethane produced in the UASB would contribute to reducing overall facilities’ energy requirements. The ultrafiltration (UF) membrane facilitated the harvesting of biomass, operating at 10 L·h−1·m−2 during the experimental period. Although the main contribution to fouling was irreversible, chemical cleanings were not necessary due to effective fouling control, which prevented the final TMP from exceeding 25 kPa. In addition, microalgae-bacterial consortium developed without prior inoculation were harvested from the MPBR using membrane assistance. The obtained biomass was also successfully tested as a biostimulant for corn germination/growth, as well as a biopesticide against Rhizoctonia solani and Fusarium oxysporum.

Appears in: INTED2024 Proceedings Publication year: 2024Pages: 4952-4956ISBN: 978-84-09-59215-9ISSN: 2340-1079doi: 10.21125/inted.2024.1281Conference name: 18th International Technology, Education and Development ConferenceDates: 4-6 March, 2024Location: Valencia, Spain

This study investigates the direct ultrafiltration process of municipal wastewater (MWW) at pilot scale. Shortterm trials were conducted with two membrane modules to assess the fouling mechanisms using different physical cleaning methods: gas sparging (hydraulic cleaning) and rotation (mechanical cleaning). This work demonstrates that membrane rotation effectively erodes and re -disperses external fouling during the backwashing stages. Consequently, shear stress generated by the rotational movement enables the operation with permeate fluxes ranging between 24 and 30 L/hm2, above the threshold flux value (22-24 L/hm2), while maintaining fouling rates (rf) below 10 Pa/s. In contrast, rf values increases up to 12.4-17.8 Pa/s when gas sparging is employed. Furthermore, the feasibility of up-concentrating municipal wastewater up to 12 times while operating with a net permeate flux of 20 L/hm2 is demonstrated through a long-term trial. The increase in suspended solids concentration (TSS = 5750 mg/L and VSS = 4750 mg/L) favours the rapid formation of a reversible cake on the membrane surface during filtration, at moderate transmembrane pressures (26 cmHg). These operating conditions avoid cake layer compression and protect the inner surface of the membrane module from severe internal residual fouling with an energy consumption of 0.027 kWh/m3.

Direct-flow filtration (i.e., without membrane aeration during the filtration phase) is a challenging oper-ation strategy in membrane bioreactors (MBRs). This study aims to provide a comprehensive approach for assessing optimal values for the main operating parameters (filtration time between backwashes and permeate flux) through the determination of the threshold flux for compressibility (Jth,c). A pilot-scale ter-tiary MBR was used for conducting filtration tests. Flux-step trials revealed the crucial role of cake com-pressibility in fouling deposition and reversibility. Accordingly, the compressible cake model was used to investigate Jth,c under different operating conditions and suspension characteristics. Based on this approach, lower filtration times (5-7 min) are recommended so that sustainable process productivity can be maximized. Specifically, decreasing filtration times from 12 to 7 min results in net permeate flux increase of more than 50%. A significant effect of suspension properties (biopolymer cluster content, BPC) on Jth,c was also found which decreased from 41.9 to 13.0 L/h m2 when increasing BPC from 0.3 to 4.6 mg/ L. Long-term tests, under temporized and variable filtration time modes, demonstrate the feasibility of using the Jth,c as a guideline for optimizing filtration performance.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).