876 research outputs found
Optimalisatie van de sturing van pompstations: Case studie: snelfiltratie pompstation Loosdrecht
No full textDoor wijzigingen in de inrichting van de drinkwatersector en veranderde eisen van de consument is de wens ontstaan de drinkwaterproductie verder te optimaliseren. Anderzijds zijn onder invloed van de ontwikkelingen van de computer, modellen ontwikkeld die de verschillende facetten van de productie beter beschrijven. Gebruik van deze modellen in de sturing van de productie is één van de mogelijkheden om optimalisatie te realiseren. Ten aanzien van de hoeveelheid water (kwantiteit) zijn dergelijke modellen inmiddels met succes opgenomen in de sturing van de productie. Zo wordt de werkelijke productie bepaald op basis van een gemodelleerde voorspelling van de vraag. Inmiddels zijn voor de beschrijving van het waterkwaliteitsverloop in de verschillende zuiveringsstappen modellen aanwezig of in ontwikkeling. Deze modellen geven een beter inzicht in de werking van de installatie. Gebruik hiervan in de sturing (als Model Predictive Control) kan leiden tot kwalitatief beter drinkwater en minimalisatie van de kosten. Daarnaast ontstaat door middel van continue monitoring een betere informatievoorziening met betrekking tot de noodzaak van onderhoud. Invoering van een dergelijke Model Predictive Control houdt een ingrijpende wijziging in de bedrijfsvoering in. In dit onderzoek zijn de mogelijkheden voor optimalisatie van de snelfiltratie van pompstation [PS] Loosdrecht beschreven. Daartoe zijn in het pompstation metingen verricht om de zuiveringsprestaties en de variaties daarin in kaart te brengen en is het programma “Stimela” gebruikt om het gevonden gedrag te simuleren. Aan de hand hiervan worden de mogelijkheden tot verbetering en de beperkingen nader uitgewerkt. PS Loosdrecht zuivert grondwater door middel van achtereenvolgens versproeiing, droogfiltratie, torenbeluchting, vlokmiddeldosering en natfiltratie. Hoge ijzergehaltes in het rein water en een daarbij behorende hoge vuillast worden als de belangrijkste problemen van deze zuivering gezien.Civil Engineering and GeosciencesWater Managemen
Irregular biofilms are predictable: Dental plaque and other bacterial yobs, if you must eat sweets, do it quickly
No full textMicroorganisms will eventually settle on anything,living or dead. Its a simple fact of life. In most cases there is no problem, the microbes are simply part of the greater ecosystem, but in others, bacteria on and in the human body become a nuisance, sometimes with disastrous consequences. Examples include dental plaque, as well as marine and pipeline fouling. Although details of these so-called biofilms have been known for some time, the overall picture was still missing. Together with Prof. Dr. Ir. Mark van Loosdrecht, Dr. Ir. Cristian Picioreanu of the Kluyver Laboratory for Biothechnology at Delft University has developed a set of mathematical models that can paint a pretty accurate picture of what goes on inside biofilms, and he has done so without even entering the field of advanced biology! If you must eat sweets, do it quickly, is one of the conclusions from his model calculations
Don't build your whole career on a single success; interview
No full textIn the future, we will flush our toilets with seawater and the sewage system will become a source of raw materials. This is according to Spinoza prizewinner and water purification expert Professor Mark van Loosdrecht.Delft University of Technolog
Assessing the aerobic/anoxic enrichment efficiency at different C/N ratios: pilot scale polyhydroxyalkanoates production from waste activated sludge
No full textPolyhydroxyalkanoates (PHA) can be produced using fermentation products of an excess sewage sludge fermentation process. An efficient method to enrich a PHA-producing community is an aerobic-feast/anoxic-famine enrichment strategy. The effect of different carbon to nitrogen (C/N) feed ratios of 1, 2 and 3.5 g COD/g N on the process performance was studied. The study was executed on a pilot plant scale using fermented waste activated sludge as the organic carbon source. The system's performance was monitored in terms of removing contaminants, producing PHA, and reducing N2O emissions. The results indicated that a lower C/N ratio results in lower PHA production, with PHA content in the sludge of 20, 24 and 36 % w/w for C/N ratios of 1, 2 and 3.5 g COD/g N, respectively. At the lowest C/N ratio, the highest nitrite accumulation rate (77 %), nitrification efficiency (89 %) and denitrification efficiency (89 %) were observed, but the N2O production was also the highest (0.77 mg N2O-N/L). The long-term comprehensive monitoring carried out in this study revealed high carbon and ammonia removal efficiencies (never below 80 %) despite the C/N shifts and high COD and ammonia concentrations. At the same time, the system showed relatively low PHA production and high environmental impact in terms of high gaseous N2O emission. These findings question the sustainability of the aerobic-feast/anoxic-famine enrichment strategy for PHA production in full-scale plants
From waste activated sludge to polyhydroxyalkanoate: Insights from a membrane-based enrichment process
No full textPolyhydroxyalkanoate (PHA) production is a promising technology fostering the spread of the circular bio-economy approach. However, the environmental implication of the process is usually neglected. This paper shows the results of a membrane-based PHA production pilot plant fed with no-pretreated waste activated sludge (WAS). The system was monitored for effluent water quality, nitrous oxide (N2O), and PHA production by dynamic accumulation over a long-term period to assess the consistency of the results over several fluctuations. The experimental study was characterized by three C/N ratios of 9, 4.5, and 4 g COD/g N. The system achieved a stable and high removal efficiency for carbon and nitrogen (96.3 ± 2.6 % and 89.9 ± 6.7 %, respectively), despite the only legislation limit respected being the biological oxygen demand concentration discharge limits imposed by 2020/741/EU. Low N2O gaseous and liquid concentrations were achieved over the 200-day experimental period, never exceeding 0.52 mg N2O-N/L. Despite the high concentration, the N2O emission factor accounted for only 0.21 ± 0.14 % of the influent nitrogen. Finally, the system produced an average of 36.3 ± 1.8 % g PHA/g VSS with a storage yield of up to 0.42 g CODPHA/g CODVFA. The system revealed a high stability over a long-term experimental period, achieving a considerable amount of PHA while maintaining a low N2O emission. Promising effluent water quality was achieved, highlighting the potential of applying the water reuse practices
Comparing two advanced selection strategies for polyhydroxyalkanoate production from domestic waste activated sludge
No full textThis study compares two membrane bioreactor-based enrichment strategies to produce polyhydroxyalkanoates (PHAs) from domestic waste-activated sludge. The aerobic dynamic feeding was implemented in layout 1 while layout 2 employs an aerobic/anoxic enrichment adopting an additional nitritation reactor. Both systems achieved around 38 % w/w of PHA with storage yields of 0.28–0.42 and 0.35–0.53 gCODPHA/gCODVFA for layouts 1 and 2, respectively. Layout 2 demonstrated an average N removal efficiency of 88.8 ± 3.9 %, slightly higher than layout 1 (82.7 ± 9.9 %). However, layout 2 showed greater nitrous oxide (N2O) emissions, averaging 0.7 ± 0.2 mg N2O-N/L almost doubling layout 1 (0.4 ± 0.1 mg N2O-N/L). Additionally, layout 2 exhibited a 42 % increase in carbon footprint compared to layout 1, reaching 10.2 kg CO2/day. This research highlights the high potential and drawbacks of the AE/AN enrichment strategy for integrating PHA production into wastewater treatment plant operations
Greenhouse gas emissions from membrane bioreactors: Analysis of a two-year survey on different MBR configurations
No full textThis study aimed at evaluating the nitrous oxide (N2O) emissions from membrane bioreactors (MBRs) for wastewater treatment. The study investigated the N2O emissions considering multiple influential factors over a two-year period: (i) different MBR based process configurations; (ii) wastewater composition (municipal or industrial); (iii) operational conditions (i.e. sludge retention time, carbon-to-nitrogen ratio, C/N, hydraulic retention time); (iv) membrane modules. Among the overall analysed configurations, the highest N2O emission occurred from the aerated reactors. The treatment of industrial wastewater, contaminated with salt and hydrocarbons, provided the highest N2O emission factor (EF): 16% of the influent nitrogen for the denitrification/nitrification-MBR plant. The lowest N2O emission (EF 1⁄4 0.5% of the influent nitrogen) was obtained in the biological phosphorus removal-moving bed-MBR plant likely due to an improvement in biological performances exerted by the co-presence of both suspended and attached biomass. The influent C/N ratio has been identified as a key factor affecting the N2O production. Indeed, a decrease of the C/N ratio (from 10 to 2) promoted the increase of N2O emissions in both gaseous and dissolved phases, mainly related to a decreased efficiency of the denitrification processes
Biogrout, ground improvement by microbial induced carbonate precipitation
No full textBiogrout is a new ground improvement method based on microbially induced precipitation of calcium carbonate (MICP). When supplied with suitable substrates, micro-organisms can catalyze biochemical conversions in the subsurface resulting in precipitation of inorganic minerals, which change the mechanical soil properties. This study focuses on one of these biochemical conversions: microbially catalyzed hydrolysis of urea inducing calcium carbonate precipitation in sand. This Biogrout process comprises the following steps: Sporosarcina pasteurii, a bacterial species containing a large amount of the enzyme urease are cultivated, injected in the ground and supplied with a solution containing urea and calcium chloride. Urease catalyzes the conversion of urea into ammonium and carbonate and the produced carbonate precipitates with calcium as calcium carbonate crystals. These crystals form sticking wedges between the sand grains increasing the strength and stiffness of the sand. The remaining ammonium chloride is extracted and disposed. The thesis comprises the necessary steps to develop this process from a laboratory experiment to a practical application, culminating in an unprecedented 100 m3 field scale experiment in which 40 m3 of sand was biologically cemented within 12 days stretching over a distance of 5 m. Engineering tools are established such as empirical correlations between the CaCO3 content and strength or stiffness, which enable to design treatment procedures for several emphasized applications, such as increasing the stiffness of railroad embankment or improving the stability of limestone room and pillar mines. Some of the remaining issues of this Biogrout process include the required removal of ammonium chloride and the use of axenically cultivated aerobic organisms with consequent decaying urease activity in time due to a lack of oxygen in the subsurface. To avoid both these issues the suitability of other possible MICP processes for ground improvement is evaluated and the potential of the most promising alternative, denitrification, is shown in laboratory experiments.BiotechnologyApplied Science
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