Multiphysics modeling of a wastewater treatment plant

Wastewater treatment plants (WWTP) are special structures designed to purify wastewater. The main objective of this work is to model the WWTP from Antequera (Malaga, Spain). The model consists of two combined simulations: (1) a 0D biological plug-flow reactor in a stationary state, establishing the concentration profiles at along the volume of the multizone reactor and, (2) a 3D clarifier. The model is based on global material balances of the WWTP has been done, based on the information from the concentrations that exist in a stationary state in each of the streams. Through this work, detailed description of two of the most important parts of the WWTP have been modeled. The results will be used in future works related to optimizing the use of these facilities for real problems related to controlling the phosphorus and nitrogen levels in the secondary effluent.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Belite calcium sulfoaluminate cement early hydration: citric acid sensitivity.

Three buckets, corresponding to three selected samples, of the same type of belite calcium sulfoaluminate (BCSA) cements have been studied. These cements show very similar elemental and mineralogical compositions, and textural properties. Mortars, for mechanical strength characterisation at 3 and 24 hours, were prepared by two different methodologies: i) with w/c of 0.40 without citric acid and ii) with w/c=0.40 and adding 0.375 wt% by weight of cement (bwc) of citric acid used as a retarder. On the one hand, the mechanical strengths, at 24 hours, obtained by the three mortars prepared by both methodologies are almost coincident, 61(5) MPa without citric acid and 61(4) MPa for the mortars prepared with citric acid. On the other hand, the early mechanical strengths at 3 hours for the mortars prepared without citric acid are also almost coincident among the three cements, i.e. ~49(3) MPa. However, when the citric acid is added, the mechanical strengths at 3 hours are quite different among the three buckets, i.e. 34(1), 42(1) and 48(1) MPa, respectively. The main aim of this study is to understand the reasons causing the different early mechanical strengths. First of all, a full characterization of the three cements has been performed: textural properties, elemental composition by X-Ray Fluorescence (XRF) and mineralogical composition, including the amorphous content, by Laboratory X-Ray Powder Diffraction (LXRPD) combined with the Rietveld method. Moreover, the soluble sulphate contents within the first minutes of hydration are being determined. An isothermal calorimetry study at 20ºC for pastes without and with different amounts of citric acid will be presented as well as in situ X-Ray powder diffraction data analysis. The results will be discussed to give a picture of the early hydration behaviour of these BCSA cements.CTS cement corporation, CSA research Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Effect of alkanolamines in kaolinitic calcined clays pozzolanic reactivity.

Five kaolinitic clays with different amounts of kaolinite, ranging between ~70 wt% and ~30 wt%, have been studied to unravel the possible activation effect of alkanolamines on the aluminate fraction of calcined clays. This is of interest for enhancing the reactivity of LC3 binders. These clays were calcinated at 860ºC for 4 h and ground to particle sizes of DV,50 ~10 μm. Three alkanolamines were selected: triisopropanolamine (TIPA), triethanolamine (TEA) and methyldiethanolamine (MDEOA), added in two dosages, 0.025 and 0.050 wt% (by weight of calcined clay, bwcc). The role of alkanolamines as activators in calcined clays was assessed following the ASTM c1897 standard bases on R3-tests. Concretely, first by measuring the heat evolved due to the pozzolanic reaction of the calcined clay and Ca(OH)2 (i.e. R3 mixture) by isothermal calorimetry at 40ºC during 7 days, and second, the bounded water by measuring the weight loss of R3 mixture after heating them at 350ºC.This study concludes that there is no significant activation of the pozzolanic activity of kaolinitic calcined clays just by adding alkanolamines. However, a mild activation was observed, i.e., higher heat evolved up to 7 days, by adding 0.05 wt% bwcc of TIPA, TEA and MDEOA to a high kaolinite content disordered metakaolin with high specific surface area calcined clay.PID2020-114650RB-I00 CTS cement corporation Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Mix and measure - Combining in situ X-ray powder diffraction and microtomography for accurate hydrating cement studies.

It is reported an innovative methodology based on in situ MoKα1 laboratory X-ray powder diffraction (LXRPD) and microtomography (μCT) avoiding any sample conditioning. The pastes are injected in 2.0 mm capillaries and the extremes are just sealed. The measurements take place in the same region of the hydrating paste. Thick capillaries are key to avoiding self-desiccation, which dictates the need of high-energy X-ray radiation for the diffraction study. This approach has been tested with a PC 42.5 R paste having w/c = 0.50. μCT data were collected at 12 h and 1, 3, 7 and 79 days. LXRPD data were acquired at 1, 3, 7 and 77 days. In this proof-ofprinciple research, the same paste was also cured ex situ. Portlandite contents obtained by thermal analysis, ex situ powder diffraction, in situ mass balance calculation and in situ powder diffraction were 13.8, 13.1, 13.1 and 12.5 wt%, respectively. From the μCT study, the grey value histogram evolution with time showed a crossing point which allowed us to distinguish (appearing) hydrated products from (dissolving) unhydrated cement particles. Segmentations were carried out by global thresholding and the random forest approach (one type of supervised Machine Learning). The comparison of the segmented results for the unhydrated cement fraction and the Rietveld quantitative phase analysis outputs gave an agreement of 2 %. The potential of this methodology to deal with more complex binders is also presented.This research was partly supported by the research grant PID2020- 114650RB-I00 of Agencia Estatal de Investigacion which is co-funded by ERDF

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Combined use of laboratory X-ray diffraction and microtomography in early age cement hydration.

In situ laboratory X-ray powder diffraction (LXRPD) is widely used for studying cement hydration at early ages. However, this approach has limitations due to the intrinsic characteristics of the main methodologies (flat sample and capillary) and their blindness to the amorphous phases and microstructures. In addition, laboratory X-ray microtomography (μ-CT) is being used for several applications but the accuracy of the obtained results is not established. Here, we present an innovative approach where LXRPD and μ-CT data are taken in the same volume of the same hydrating paste within a thick capillary with time. The results from both techniques should agree, resulting in more reliable information. The methodology developed here is based on capillaries of 2 mm of diameter to minimize self-drying and to have very good powder averaging. In this proof-of-principle investigation, μ-CT data have been collected for a PC-42.5R paste, w/c=0.50, at 12 hours and 1, 3 and 7 days, and for LXRPD at 1, 3 and 7 days. Powder diffraction data have been analysed by the Rietveld method and the results have been verified by mass balance calculations. μ-CT data have been segmented. The results indicate that the developed methodology is accurate. The long-term aim of this research is to be able to monitor the reaction of the amorphous components of widely-used supplementary cementitious materials (SCMs) like the amorphous silica in fly/volcanic ashes or the metakaolin in calcined clays.Financial support from PID2020-114650RB-I00 research grant, co-funded by FEDER, is acknowledged. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Pozzolanic materials to reduce CO2 emissions: local solutions for a global issue.

Abstract de una keynote invitada.In recent decades, the cement sector has been looking for solutions to reduce the carbon footprint, being one of the most promising strategies, the replacement of clinker with supplementary cementitious materials, SCMs. However, the main limitation of this approach is the availability of suitable SCMs. This work presents the study of three families of pozzolanic materials, Spanish calcined clays (CC), Natural Pozzolans (NP) and fly ashes (FA). The characterization of each family will be presented, with emphasis on the kaolinite content of the original clays and the amorphous contents of the natural pozzolans and fly ashes. The results of the pozzolanic prediction tests will be compared: strength activity index, SAI, and R3 test according to ASTM C1897-20. The SAI test has two important limitations: i) it gives false positives at 28 days, as does the addition of quartz (Qz) and ii) a minimum of 28 days is required to obtain the pozzolanic activity results. In addition, the R3 test has proved to be useful in ruling out inert additions, such as quartz. Moreover, it presents a very good correlation between the heat emitted and the combined water at 7 days and the amount of kaolinite in clays or amorphous in ashes. However, the absolute values of heat and combined water cannot be compared between different families. That is, in the calcined clay family, it can be inferred that if the kaolinite content is higher than 50 wt%, the heat released should be between 500-700 J/g, whereas a fly ash with an amorphous content of around 70 wt% will release between 200-250 J/g.PID2020-114650RB-I00 grant from Spanish government, Master Builders Solutions Deutschland GmbH (Germany) and Buzzi Unicem SpA (Italy) are thanked for the funding. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Dataset for "Mix and measure - combining in situ X-ray powder diffraction and microtomography for accurate hydrating cement studies" paper

<p>Dataset for paper abstract: "It is reported an innovative methodology based on in situ MoKa1 laboratory X-ray powder diffraction (LXRPD) and microtomography (μCT) avoiding any sample conditioning. The pastes are injected in 2.0 mm capillaries and the extremes are just sealed. The measurements take place in the same region of the hydrating paste. Thick capillaries are key to avoiding self-desiccation, which dictates the need of high-energy X-ray radiation for the diffraction study. This approach has been tested with a PC 42.5 R paste having w/c=0.50. μCT data were collected at 12 hours and 1, 3, 7 and 79 days. LXRPD data were acquired at 1, 3, 7 and 77 days. In this proof-of-principle research, the same paste was also cured ex situ. Portlandite contents obtained by thermal analysis, ex situ powder diffraction, in situ mass balance calculation and in situ powder diffraction were 13.8, 13.1, 13.1 and 12.5 wt%, respectively. From the μCT study, the grey value histogram evolution with time showed a crossing point which allowed us to distinguish (appearing) hydrated products from (dissolving) unhydrated cement particles. Segmentations were carried out by global thresholding and the random forest approach (one type of supervised Machine Learning). The comparison of the segmented results for the unhydrated cement fraction and the Rietveld quantitative phase analysis outputs gave an agreement of 2%. The potential of this methodology to deal with more complex binders is also presented."</p><p><strong>Acknowledgement.</strong> This research was partly supported by the research grant PID2020-114650RB-I00 which is co-funded by ERDF.</p><p><strong>Funding: </strong>PID2020-114650RB-I00</p&gt