13 research outputs found
Filtration characteristics in membrane bioreactors
No full textCauses of and remedies for membrane fouling in Membrane Bioreactors for wastewater treatment are only poorly understood and described in scientific literature. A Filtration Characterisation Installation and a measurement protocol were developed with the aim of a) unequivocally determination and quantification of the filterability of an activated sludge and b) carrying out short term experiments at labscale to determine foulants and/or fouling propensity determining factors. The installation was tested at three locations in the Netherlands where membrane bioreactors were applied to treat municipal wastewater. The results show that each MBR system creates an activated sludge with very specific filtration characteristics in a wide range. The filterability may well be characterised by the filtration resistance, additional to the clean water resistance, after 20 L of permeate production per square meter membrane area: DR20. Preliminary experiments were carried out to identify fouling substances by testing the theory that polysaccharides in the water phase can be related to fouling behaviour. This relation could not be proved.Civil Engineering and Geoscience
Serious Gaming for Participatory Transformation of Religious Heritage: The case of the Kruispuntkerk in Voorschoten
No full textThis paper utilizes a modular generative design framework, as proposed by Azadi & Nourian (2021b), to create a serious game that includes a novel phase - the development phase - in addition to the three phases proposed in the original framework: planning, configuration, and shaping. The serious game incorporates both digital and physical elements and is tested through a case study involving the transformation of the Kruispunt church in Voorschoten. The game deals with the different stakeholders, their goals and relation towards the church, but also with the values related to attributes that come with religious architectural heritage. In a role game five students play the role of the participants. The reached consensus within the serious game can directly be applied on the case study but the idea is they will be also interpreted by an architect in the last phase, the shaping or as this paper proposes the implementation phase. This paper recommends future research can be done on the further development of a serious game using scoring mechanism, AI and stakeholder participation instead of roleplay.Architecture, Urbanism and Building Sciences | Heritage & Architectur
Membraanvervuiling in membraanbioreactoren door extracellulaire polymere substanties: Een vergelijkend onderzoek met vier pilot-installaties
No full textDe conventionele zuiveringsmethode voor huishoudelijk afvalwater is het actiefslib-proces. Bij deze techniek wordt het afvalwater in een reactor belucht en vermengd met een geconcentreerde suspensie bacteriën. De bacteriën, die in vlokken leven, zorgen voor de biologische afbraak van organische en andere verontreinigingen in het water. Aan het eind van het proces worden de vlokken van het water gescheiden door middel van bezinking en vervolgens teruggevoerd naar de reactor. Een innovatie binnen het actiefslib-proces is de membraanbioreactor (MBR). Bij het MBR-proces vindt de scheiding tussen slib en water niet plaats door middel van bezinking, maar met behulp van een membraanstap. Kwalitatief beter effluent en ruimtebesparing zijn hiervan de voornaamste voordelen. Het nadeel is dat de techniek relatief duur is vanwege de dure membranen, het hogere energieverbruik en de reinigingsmaatregelen die nodig zijn als gevolg van de membraanvervuiling die bij het proces ontstaat. Toch komt MBR-technologie de laatste jaren steeds meer in beeld als zuiveringstechniek voor huishoudelijk afvalwater. Drijfveer hierachter is de daling van de meerkosten die door intensief onderzoek bewerkstelligd is. Sinds 2001 participeert ook de TU Delft met een onderzoek naar membraanvervuiling in MBR.Sanitary EngineeringWatermanagementCivil Engineering and Geoscience
Fouling modification during pretreatment for dead-end ultrafiltration of wwtp effluent: Fractionation in relation to filterability and foulants
No full textA proved technique to upgrade (wastewater treatment plant) wwtp effluent to improved water quality is dead-end ultrafiltration (UF). Although the use of UF for upgrading wwtp effluent results in an excellent basic water quality, this technique faces problems due to membrane fouling. Especially particles in the size range between 0.1 and 0.45 @m (5 to 20 times larger than the membrane pores) are mainly responsible for membrane fouling. By the implementation of a pretreatment step for the dead-end UF installation, the particles in the critical fraction between 0.1 @m and 0.45 @m might be removed. Previous pretreatment methods did not give satisfying results. Apparently pretreatment with multimedia filtration, microfiltration and in-line coagulation with poly aluminium chloride (PACl), sometimes in combination with continuous sand filtration, did not remove the (effect of) these particles. Filterability did improve though, but only with a small percentage. In this research six pretreatment methods for dead-end UF are investigated. The objective of this research is to determine if the implementation of those pretreatment methods have any influence on the filterability of wwtp effluent. When an increase in filterability takes place, after a certain pretreatment step, the fraction in which the main filterability increase takes place, has to be determined. The six pretreatment steps were investigated on three different wwtp’s in the Netherlands. From February until May water was taken from wwtp Maasbommel. At this plant three pretreatment steps were involved; the dosage of NALMET (a polymeric substance, mainly for removal of heavy metals, the dosage of powdered activated carbon (PAC) and treatment with granular activated carbon (GAC). At wwtp Veendam experiments were carried out with a Fuzzy Filter in April. From July until September investigations started at wwtp Horstermeer with two different techniques; a multimedia filter and treatment of wwtp effluent with water fleas (Daphnia). The collected samples were fractionated which divides a sample in four fractions; the raw fraction, 0.45 ?m. Pretreatment with NALMET and GAC is not able to effectively remove the (effect of) the most important membrane fouling fraction of 0.1 - 0.2 ?m. Treatment with PAC and GAC did remove proteins, colour and humic substances. Polysaccharides accumulated in front of the membrane, resulting in high concentrations. No change was determined after treatment with GAC. After dosage of NALMET concentrations of TOC, DOC, proteins and humic substances increased. Concentrations of polysaccharides and colour stayed more or less constant. Treatment with a Fuzzy Filter did not have any effect on all the measured foulants in this research. Varying results were obtained after both multimedia filtration and Daphnia. No foulant did increase or decrease structurally after both pretreatment methods. High SUR values go hand in hand with high concentrations of proteins, colour and humic substances. This is not the case for TOC and polysaccharides. Foulants could not be related to filterability per fraction. The total SUR is mainly caused by particles in the fraction between 0.1 and 0.45 ?m, while most of the foulants are present in the fraction <0.1 ?m. For removing the most important membrane fraction, other options should be investigated. Other methods which might remove the critical fraction are a precoat layer, ozonation and slow sand filtration. Optimizing the configurations of the used pretreatment methods might give other results than illustrated here. Repetition of the experiments carried out for this research could confirm the outcomes of this thesis.Sanitary EngineeringWatermanagementCivil Engineering and Geoscience
Combined ZVS-ZCS topology for high-current direct current hybrid switches: Design aspects and first measurements
No full textElectrical Engineering, Mathematics and Computer Scienc
It Takes Two (Seconds): Decreasing Encoding Time for Two-2 Choice FNIRS BCI Communication
No full textSignificance. Brain-computer interfaces (BCIs) can provide severely motor-impaired patients with a motor-independent communication channel. Functional near-infrared spectroscopy (fNIRS) constitutes a promising BCI-input modality given its high mobility, safety, user comfort, cost-efficiency, and relatively low motion sensitivity.
Aim. The present study aimed at developing an efficient and convenient two-choice fNIRS communication BCI by implementing a relatively short encoding time (2s), considerably increasing communication speed, and decreasing the cognitive load of BCI users.
Approach. To encode binary answers to ten biographical questions, ten healthy adults repeatedly performed a combined motor-speech imagery task within two different time windows guided by auditory instructions. Each answer-encoding run consisted of ten trials. Answers were decoded during the ongoing experiment from the time course of the individually identified most-informative fNIRS channel-by-chromophore combination.
Results. The answers of participants were decoded online with an accuracy of 85.8% (run-based group mean). Post-hoc analysis yielded an average single-trial accuracy of 68.1%. Analysis of the effect of number of trial repetitions showed that the best information-transfer rate could be obtained by combining four encoding trials.
Conclusions. The study demonstrates that an encoding time as short as 2s can enable immediate, efficient, and convenient fNIRS-BCI communication
Filtration Characterization Method as Tool to Assess Membrane Bioreactor Sludge Filterability—The Delft Experience
No full textPrevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming to support optimization in MBR operation. Therefore, there is a need for an evaluation of the lessons learned and how to proceed. In this article, five different methods for measuring MBR activated sludge filterability and critical flux are described, commented and evaluated. Both parameters characterize the fouling potential in full-scale MBRs. The article focuses on the Delft Filtration Characterization method (DFCm) as a convenient tool to characterize sludge properties, namely on data processing, accuracy, reproducibility, reliability, and applicability, defining the boundaries of the DFCm. Significant progress was made concerning fouling measurements in particular by using straight forward approaches focusing on the applicability of the obtained results. Nevertheless, a fouling measurement method is still to be defined which is capable of being unequivocal, concerning the fouling parameters definitions; practical and simple, in terms of set-up and operation; broad and useful, in terms of obtained results. A step forward would be the standardization of the aforementioned method to assess the sludge filtration quality
It takes two (seconds):decreasing encoding time for two-choice functional near-infrared spectroscopy brain-computer interface communication
No full textSIGNIFICANCE: Brain-computer interfaces (BCIs) can provide severely motor-impaired patients with a motor-independent communication channel. Functional near-infrared spectroscopy (fNIRS) constitutes a promising BCI-input modality given its high mobility, safety, user comfort, cost-efficiency, and relatively low motion sensitivity. AIM: The present study aimed at developing an efficient and convenient two-choice fNIRS communication BCI by implementing a relatively short encoding time (2 s), considerably increasing communication speed, and decreasing the cognitive load of BCI users. APPROACH: To encode binary answers to 10 biographical questions, 10 healthy adults repeatedly performed a combined motor-speech imagery task within 2 different time windows guided by auditory instructions. Each answer-encoding run consisted of 10 trials. Answers were decoded during the ongoing experiment from the time course of the individually identified most-informative fNIRS channel-by-chromophore combination. RESULTS: The answers of participants were decoded online with an accuracy of 85.8% (run-based group mean). Post-hoc analysis yielded an average single-trial accuracy of 68.1%. Analysis of the effect of number of trial repetitions showed that the best information-transfer rate could be obtained by combining four encoding trials. CONCLUSIONS: The study demonstrates that an encoding time as short as 2 s can enable immediate, efficient, and convenient fNIRS-BCI communication
Publisher Correction: fNIRS reproducibility varies with data quality, analysis pipelines, and researcher experience
No full textCorrection to: Communications Biology https://doi.org/10.1038/s42003-025-08412-1, published online 4 August 2025In this article, Meryem A. Yücel should have been denoted as a co-corresponding author. The original article has been corrected
