Full Mass Balance Research Articles

Flowsheet development for and commissioning of the Kamoa-Kakula project

The Kamoa-Kakula copper resource, located west of Kolwezi in the Democratic Republic of the Congo, was discovered and explored by Ivanhoe from 2008/9 on. As a greenfield project with prospects of high grade ore and a long life-of-mine, the need for best practice flowsheet development was recognised, so as to ensure sustainability of metallurgical performance at the at the maximum economic level from the orebody during metallurgical operations. Process Mineralogy, a hybrid discipline, has been developed in the mining industry over the last forty years, and its proper use has seen very successful outcomes in flowsheet development (Bradshaw, 2014; Lotter, 2011; Lotter et al., 2003; McKay et al., 2007; Pease et al., 2005). Drill core was sampled at site across six phases of flowsheet development that worked with the developing mine plan. The two main geomet units were hypogene and supergene, with the hypogene being unusually rich in bornite. The main variability is between supergene and hypogene, and between Kamoa and Kakula, but with less spatial variability within them. The first viable flowsheet was developed and demonstrated in nine months of test work, followed by various revisions and iterations as required by the discovery of variable mineralogy. The first flowsheet, called “Milestone”, was then challenged with an opportunity for a simpler but better-performing flowsheet, which became known as IFS4A. The simultaneous discovery of the Kakula resource refocussed the project due to its shallower depth and higher grade. Laboratory scale flotation testing using IFS4A in Phase 6 of Kamoa and two drill-holes of Kakula quickly confirmed that the Kakula ore outperformed the Kamoa supergene ore using this flowsheet. A mini-pilot plant campaign was run in 2019 with this flowsheet plus modifications, using 985 kg of metallurgical drill cores material to demonstrate the full flowsheet mass and value balance on a continuous operating campaign. This mass and value balance produced an estimated 85.6 % Cu recovery with a saleable concentrate grading 57.3 % Cu. Whereas this paper concentrates on the mineralogy and its contribution to process implications such as grinding requirements and flotation strategy, it is recognized that first-class design, engineering and construction contributed in no small measure to the successful start-up. This mass and value balance was used in the design of the grinding and flotation circuits, and contributed to the successful commissioning of the new concentrator in 2021, which averaged a recovery of 84.7 % at a grade of 50.5 % Cu, in good agreement with the testwork. A McNulty model for the commissioning data shows a better than Type 1A start-up. The flowsheet development part of the project is discussed in this paper as a case study.

Evaporation of sulphur mustard (HD) from common matrices with comparison to nerve agents

ABSTRACT The use of chemical warfare agents (CWAs) in terrorist attacks remains a potential threat. Therefore, an updated wide-ranging database that contains details on the fate of CWAs on environmental surfaces is required, especially for the persistent blister agent sulphur mustard (HD). For this purpose, long-period evaporation rates measurements of HD from various common urban matrices were conducted from our specialised laboratory-designed wind tunnel. Small HD droplets were dispersed on each matrix surface, and then placed in the evaporation chamber. Samples of the target material were collected by continuous sampling on SPE (solid-phase extraction) tubes and analysed by GC (gas-chromatography) analytical method. Profiles of the air vapour concentrations as a function of time (up to four orders of magnitude) and the total mass balances were calculated at two temperatures. The results indicated fast clearance of HD together with a nearly full mass balance from stainless steel and smooth surface tiles, as these matrices are relatively inert. On the other hand, asphalt blocks relatively conserve HD, exhibiting a slow-release mode of action over 7–11 days until matching the GPL (General Population Limit) for HD. The concentration profile of commercial sidewalk bricks showed a moderate decay that characterises a semi-conserving matrix. These findings were compared to the evaporation profiles of the nerve agents sarin (GB) and VX from the same surfaces at the same experimental conditions. We can conclude that HD contamination can cause a secondary risk by a slow release into the atmosphere, especially from surfaces exhibiting conserving characteristics.

Mass Transport of Diazomethane across Teflon AF2400 Membrane for Scale-Up Development

Diazomethane is an attractive C1 building block in organic chemistry, but its hazardous nature presents scale-up challenges to this date. The use of a Teflon AF2400 membrane, most commonly in a tube-in-tube reactor setup, is the current state-of-the-art methodology for inherently safer laboratory-scale generation, separation, and consumption of anhydrous diazomethane. For the successful scale-up of this membrane process, the key mass transfer coefficient of the AF2400 membrane, its permeability for diazomethane, was investigated. We report in this contribution a novel methodology to determine diazomethane permeability for the rational scale-up of membrane processes for the safe handling of diazomethane. Missing physical properties of diazomethane were established, and the full mass balance of in situ-generated diazomethane within the tube-in-tube reactor was experimentally validated. A numerical model of the membrane reactor system in combination with experimental data yielded a permeability value of 414 barrer. This result enables scale-up development of the laboratory membrane reactor toward production-scale systems.

Key comparison study on peptide purity - hexapeptide of HbA0

Main textUnder the auspices of the Protein Analysis Working Group (PAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM-K115.2018, was coordinated by the Bureau International des Poids et Mesures (BIPM), the Health Sciences Authority (HSA) of Singapore and the Chinese National Institute of Metrology (NIM). Ten Metrology Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of the hexapeptide of HbA0 (VE) present as the main component in the comparison sample for CCQM-K115.2018. The comparison samples were prepared by HSA/BIPM from synthetic VE purchased from a commercial supplier and used as provided without further treatment or purification.VE was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of chemically synthesized peptides of known sequence, without cross-links, up to 5 kDa and without modification. It was anticipated to provide an analytical measurement challenge representative for the value-assignment of compounds of broadly similar structural characteristics.The majority of participants used amino acid analysis (PICAA) with a correction for structurally-related peptide impurities approach as the amount of material that had been provided to each participant (25 mg) was insufficient to perform a full mass balance based characterization of the material by a participating laboratory. The coordinators, the BIPM, the HSA and the NIM, were the laboratories to use the mass balance approach as they had more material available.It was decided to propose KCRVs for both the VE mass fraction and the mass fraction of the peptide related impurities as indispensable contributor regardless of the use of PICAA, mass balance or any other approach to determine the VE purity. This allowed participants to demonstrate the efficacy of their implementation of the approaches used to determine the VE mass fraction. In particular, it allowed participants to demonstrate the efficacy of their implementation of peptide related impurity identification and quantification.More detailed studies on the identification/quantification of peptide related impurities revealed that the integrity of the impurity profile of the related peptide impurities obtained by the participant is crucial for the impact on accuracy of the VE mass fraction assignment.The assessment of the mass fraction of peptide impurities is based on the assumption that only the most consistent set of results is taken for the calculation of the KCRVPepImp. The sum of the combined cis/trans VE depsipeptide impurities (only identified/quantified by NRC and confirmed by BIPM and HSA) and mass fractions of peptide related impurities that have been identified by at least two participants have been used to establish the KCRVPepImp. The KCRVPepImp of 53.0 mg/g is associated with a corresponding expanded uncertainty of 17.3 mg/g (k = 2) providing a more realistic basis of evaluation for the capabilities of the participants to identify/quantify peptide related impurities. Inspection of the degree of equivalence plots for the mass fraction of peptide impurities and additional information obtained from the peptide related impurity profile indicates that in all cases the major related peptide impurity, VE depsipeptide, has not been identified. The VE depsipeptide impurity was initially and uniquely identified and quantified by the NRC by the use of 1H-NMR. The related peptide impurity mass fraction results of only four participants (NRC, LGC, LNE and HSA) are in agreement with the KCRVPepImp. The NRC has identified and quantified the VE depsipeptide whereas the LGC, LNE and HSA have not identified the VE depsipeptide but accounted for that contribution.The approach selected to obtain a KCRVVE for the mass fraction of VE is based on a mass balance calculation that takes into account the most consistent set of results for the peptide related impurities KCRVPepImp, TFA mass fraction and the water mass fraction. The KCRVVE for CCQM-K115.2018 is 613 mg/g with a corresponding expanded uncertainty of the KCRVVE of 20 mg/g (k = 2).To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison study on peptide purity - glycated hexapeptide of HbA1c

Main textUnder the auspices of the Protein Analysis Working Group (PAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM-K115.c, was coordinated by the Bureau International des Poids et Mesures (BIPM), the Health Sciences Authority (HSA) of Singapore and the Chinese National Institute of Metrology (NIM). Nine Metrology Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of the glycated hexapeptide of HbA1c (GE) present as the main component in the comparison sample for CCQM-K115.c. The comparison samples were prepared by HSA/BIPM from synthetic GE purchased from a commercial supplier and used as provided without further treatment or purification.GE was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of chemically synthesized peptides of known sequence, without cross-links, up to 5 kDa and modification (mono-glycation). It was anticipated to provide an analytical measurement challenge representative for the value-assignment of compounds of broadly similar structural characteristics.The majority of participants used amino acid analysis (PICAA) or quantitative nuclear magnetic resonance (PICqNMR) spectroscopy with a correction for structurally-related peptide impurities approach as the amount of material that has been provided to each participant (25 mg) is insufficient to perform a full mass balance based characterization of the material by a participating laboratory. The coordinators, the BIPM, the HSA and the NIM, were the laboratories to use the mass balance approach as they had more material available.It was decided to propose KCRVs for both the GE mass fraction and the mass fraction of the peptide-related impurities as indispensable contributor regardless of the use of PICAA, PICqNMR or mass balance to determine the GE purity. This allowed participants to demonstrate the efficacy of their implementation of the approaches used to determine the GE mass fraction. In particular, it allows participants to demonstrate the efficacy of their implementation of peptide-related impurity identification and quantification.More detailed studies on the identification/quantification of peptide-related impurities revealed that the integrity of the impurity profile of the related peptide impurities obtained by the participant is crucial for the impact on accuracy of the GE mass fraction assignment.The assessment of the mass fraction of peptide impurities is based on the assumption that that all results are directly taken for the calculation of the KCRVPepImp by use of random-effects meta-analysis (DerSimonian-Laird (DSL) variance-weighted mean). The KCRVPepImp of 45.4 mg/g is associated with a corresponding expanded uncertainty of 9.5 mg/g (k =2.26) providing a more realistic basis of evaluation for the capabilities of the participants to identify/quantify peptide-related impurities. Inspection of the degree of equivalence plots for the mass fraction of peptide impurities and additional information obtained from the peptide-related impurity profile indicates that in most cases the major related peptide impurities have been identified and quantified.The approach selected to obtain a KCRVGE for the mass fraction of GE is based on the DerSimonian-Laird (DSL) variance-weighted mean. The DSL mean takes into account the uncertainties of the results while introducing sufficient excess variance to allow for their observed dispersion resulting in a larger expanded uncertainty U(KCRVGE). The KCRVGE for CCQM-K115.c is 628 mg/g with a corresponding expanded uncertainty of the KCRVGE of 27 mg/g (k =2.26). All GE mass fraction results are in agreement with the KCRVGE.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Advanced mass balance characterization and fractionation of algal biomass composition

Opportunities associated with biomass production and bioproduct isolation from algae-derived feedstocks are plentiful and promising; however, there are challenges associated with realizing these applications. One of the most important, and often overlooked, challenges is the lack of availability of a strong foundation of compositional analysis methods validated on microalgal biomass. Currently, compositional analysis in algae is dominated by the use of interference-prone methods, a lack of full mass balance accounting, and the use of top-down approaches that bin all unaccounted-for mass into a single category, such as carbohydrates. We present here an approach based on a bottom-up algal biomass characterization aimed at moving towards, and highlighting the importance of, full and accurate mass closure to achieve the maximum economic potential from a sustainable and renewable feedstock. Algal biomass representing three genera, Nannochloropsis, Scenedesmus, and Monoraphidium, was subjected to a cell rupture and fractionation process, followed by detailed characterization of each fraction to determine the partitioning of measured and unknown components. The goal of this work is to identify where the missing components partition, and develop a strategy to close the mass balance or identify the unknowns, while utilizing a rigorous characterization approach for characterizing algal biomass. Although only 75–80% of the biomass was accounted for, the fractionation approach utilized here provides key insight into possible chemical components for future investigations.

Cross-shelf export of particulate organic carbon in the northern South China Sea: Insights from a 234Th mass balance

Cross-shelf transport of particulate organic carbon (POC) is an essential but poorly quantified process regulating the POC flux and the biological pump efficiency in marginal seas. Here, we estimated the cross-shelf export flux of 234Th and POC from the northern South China Sea (NSCS) shelf based on a dataset of 234Th in the water column and the underlying sediments over the shelf (bottom depth ≤ 200 m) and the adjacent slope (bottom depth > 200 m). Based on a full mass balance of 234Th throughout the water column and the underlying sediments, we found that besides radioactive production and decay, sedimentary accumulation and cross-shelf export associated with drifting particles were the most important processes in the 234Th budget. The input via horizontal shelf-slope water exchange and along-shelf water transport was a 234Th source to the shelf water, and neglecting this component would underestimate the actual vertical 234Th and POC fluxes by ~10–33%. The POC flux via vertical export from the euphotic zone was 26 ± 1 mmol m−2 d−1 while that via cross-shelf transport was 9.9 ± 3.4 mmol m−2 d−1. The cross-shelf exported POC presumably inject into the intermediate/deep waters and could be trapped for several decades in the SCS. Our results highlight the importance of cross-shelf POC transport in regulating carbon storage in the SCS on seasonal to longer time scales. A compilation of the case studies regarding cross-shelf transport suggests its role in the carbon cycle might be more important than previously recognized and needs to be re-evaluated.

Laboratory and pilot evaluation of aquaporin-based forward osmosis membranes for rejection of micropollutants

Aquaporin-based forward osmosis (AQP FO) membranes were applied both in laboratory- and pilot-scale for removing micropollutants from water. The effect of operating parameters (feed flow, draw flow, and transmembrane pressure) on the i) rejection of micropollutants, ii) water flux, iii) reverse salt flux, and iv) water recovery of the AQP FO membrane modules was studied. Among the 21 micropollutants spiked, only four compounds, atenolol, propranolol, metoprolol, and citalopram, permeated through the AQP FO membranes to an extent that they could be quantified in the draw solutions of both the laboratory and pilot systems. The rejection rates, based on the full mass balance calculations, were between 96.1% and 99.7%, and all the other 17 compounds showed rejection exceeding 90% on both systems. The pilot AQP FO system was further employed for six days to treat effluent from a membrane bioreactor (MBR) treating municipal wastewater. 35 micropollutants were investigated. 27 of these were identified and quantified in the MBR effluent. Minute fractions of gabapentin, benzotriazole, and metoprolol were detected passing through the AQP FO membranes into the draw side with a constant rejection of around 99.2%, 95.4%, and 99.9%. Almost all other micropollutants’ minimum rejection rates exceeded 80%.

Multiscale Legacy Responses of Soil Gas Concentrations to Soil Moisture and Temperature Fluctuations

AbstractThe sensitivity of soil carbon dynamics to climate change is a major uncertainty in carbon cycle models. Of particular interest is the response of soil biogeochemical cycles to variability in hydroclimatic states and the related quantification of soil memory. Toward this goal, the power spectra of soil hydrologic and biogeochemical states were analyzed using measurements of soil temperature, moisture, oxygen, and carbon dioxide at two sites. Power spectra indicated multiscale power law scaling across subhourly to annual timescales. Precipitation fluctuations were most strongly expressed in the soil biogeochemical signals at monthly to annual timescales. Soil moisture and temperature fluctuations were comparable in strength at one site, while temperature was dominant at the other. The effect of soil hydrologic, thermal, and biogeochemical processes on gas concentration variability was evidenced by low spectral entropy relative to the white noise character of precipitation. A full mass balance model was unable to capture high‐frequency soil temperature influence, indicating a gap in commonly used model assumptions. A linearized model was shown to capture the main features of the observed and modeled gas concentration spectra and demonstrated how the means and variances of soil moisture and temperature interact to produce the gas concentration spectra. Breakpoints in the spectra corresponded to the mean rate of gas efflux, providing a first‐order estimate of the soil biogeochemical integral timescale (∼1 min). These methods can be used to identify biogeochemical system dynamics to develop robust, process‐based soil biogeochemistry models that capture variability in addition to long‐term mean values.

A data-driven comparison of commercially available testing methods for algae characterization

Algal biomass composition is often the primary driver of economic viability of research and commercial algae-based product development. As the commercial algae production field is expanding, there is a growing need for a standardized language across producers and markets in terms of biomass characterization. Similarly, to establish and design collaborative or cross-institutional algae research projects, groups need to harmonize reported compositional analysis data to ensure comparable and reproducible results. In order to provide a consistent foundation of algae quality assessment, we are working towards closely coordinated, harmonized and objective operational protocols across the algae community. We present here a demonstration of biomass composition data from different commercial analytical laboratories, specifically applied to a reference biomass material. The data highlights a lack of consistency across laboratories in methods that are available for analysis. The data presented here illustrate variability in reported biomass measurements of protein, lipids and carbohydrate content causing differences of up to 1.36, 1.43, and 3.37-fold respectively, when expressed on a dry biomass basis. When the same methods are used between the laboratories, e.g. for protein and ash measurements, the data are consistent across laboratories. However, the reported lipid content varies with the method chosen at each laboratory, and causes the calculated carbohydrate content to then absorb the remaining difference from full mass balance closure. A suggestion of a common set of analytical standard methods available commercially is provided and can help to alleviate some of the challenges the algae community faces in terms of biomass descriptive reporting. This work sets the stage for and identifies critical niches to build on an established framework for understanding and harmonizing analytical methodologies for compositional analysis of algal biomass.

Restoring original composition of hydrothermally altered Archean metavolcanic rocks of the Carajás Mineral Province (Brazil): Geodynamic implications for the transition from lid to mobile tectonics

One of the most debated issues about the Carajás Mineral Province in Brazil is the tectonic setting that prevailed at the time of the major Neoarchean (ca. 2.7 Ga) volcanic event, with views ranging from subduction- to rift-related. During this event, thick lava flows of mainly basaltic and basaltic-andesitic composition extruded at the Earth's surface, cooled and underwent significant alteration by hydrothermal fluids rising through deep-seated crustal faults. Archean settings have been inferred for hydrothermally altered volcanic rocks using as a proxy their whole-rock compositions in discrimination diagrams for modern geotectonics. Despite its debatable application to Archean volcanic sites, the same working approach is used in reconsidering the geodynamic view about the Carajás volcanic event. We use an artificial neural networks-based method to perform a full mass balance calculation on a large compiled database of metavolcanic rocks from Carajás. Predicted precursors reproduce a linear and limited FeO*/MgO increase with SiO2 typical of modern calc-alkaline arc environment. Moreover, the identified least-altered rocks show that they may petrogenetically involve subducted water-bearing sediments. But contrary to what is expected for such a volcanic arc environment, amphibole and magnetite fractionations have not been observed in the precursors. Discrimination diagrams using incompatible trace elements were unable to rule out the subduction hypothesis so other geological and geochemical evidence from the granitoid record of Carajás was taken into consideration. In combination with the Archean granitoid evolution of CMP, we conclude that crustal contamination associated with continental rifting appears to be the most likely process for inducing the calc-alkaline affinity of the Carajás Neoarchean metavolcanic rocks. This calc-alkaline affinity in least-altered volcanic rocks appears to be best reproduced by petrogenetic modelling involving wall-rock assimilation and melting of the Carajás basement (TTG and other K-rich granitoids) by parental magmas derived from depleted mantle source, prior to their fractional crystallization. This volcanic event was coeval with the intrusion of A-type syntectonic granitoids at the transition from a stagnant lid to mobile plate tectonic regime associated with localized translithospheric transpressional rift.

Beryllium-7 Elucidate Sediment Dynamics of the Branford River Estuary, Connecticut, USA

Berrylium-7 elucidates sediment dynamics (i.e., sources, sinks, deposition, and resuspension) in a Connecticut estuary. Average annual atmospheric deposition of 7Be is 290 mBq cm−2 year−1. Sediment samples from 43 locations within the estuary show that 7Be deposition is spatially complex, but were statistically indistinguishable a year apart. Weekly time series of sediments indicate that levels are nearly constant on this shorter time scale once radioactive decay is taken into account. 7Be levels in sediments are a balance between steady losses through radioactive decay and periodic pulse inputs following rainstorms. The water column was measured intensively during three rain events, showing that 7Be is removed rapidly from the water column, with a rate constant averaging 1.00 ± 0.12 day−1. A mass balance shows that 7Be is supplied about equally by direct precipitation onto the estuary’s surface and inflow from the watershed. Losses from the water column are split between net sedimentation (43%) and tidal flushing (57%). Variations in sedimentary 7Be levels at very short (meters) and longer (km) distances, and changes at time scales from hours to years, indicate that a large number of samples are required to capture all the variability in these highly dynamic systems. The current study differs from previous research in that a large number of measurements were conducted on a smaller system, and a full mass balance was developed.

Key comparison study on peptide purity - synthetic oxytocin

Under the auspices of the Protein Analysis Working Group (PAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM-K115.b, was coordinated by the Bureau International des Poids et Mesures (BIPM) and the Chinese National Institute of Metrology (NIM). Seven Metrology Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of oxytocin (OXT) present as the main component in the comparison sample for CCQM-K115.b. The comparison samples were prepared from synthetic OXT purchased from a commercial supplier and used as provided without further treatment or purification.OXT was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of chemically synthesized peptides of known sequence, with one cross-link and up to 5 kDa. It was anticipated to provide an analytical measurement challenge representative for the value-assignment of compounds of broadly similar structural characteristics.The majority of participants used amino acid analysis (PICAA) or quantitative nuclear magnetic resonance (PICqNMR) spectroscopy with a correction for structurally-related peptide impurities approach as the amount of material that has been provided to each participant (25 mg) is insufficient to perform a full mass balance based characterization of the material by a participating laboratory. The coordinators, both the BIPM and the NIM, were the laboratories to use the mass balance approach as they had more material available.It was decided to propose KCRVs for both the OXT mass fraction and the mass fraction of the peptide related impurities as indispensable contributor regardless of the use of PICAA, PICqNMR or mass balance to determine the OXT purity. This allowed participants to demonstrate the efficacy of their implementation of the approaches used to determine the OXT mass fraction. In particular, it allows participants to demonstrate the efficacy of their implementation of peptide related impurity identification and quantification.More detailed studies on the identification/quantification of peptide related impurities and the hydrolysis efficiency revealed that the integrity of the impurity profile of the related peptide impurities obtained by the participant is crucial for the impact on accuracy of the OXT mass fraction assignment.The assessment of the mass fraction of peptide impurities is based on the assumption that only the Largest Consistent Subset (LCS) of results is taken for the calculation of the KCRVPepImp by use of the weighted mean. The KCRVPepImp of 31.6 mg/g is associated with a small corresponding expanded uncertainty of ±1.4 mg/g (k =2) providing a more realistic basis of evaluation for the capabilities of the participants to identify/quantify peptide related impurities. Inspection of the degree of equivalence plots for the mass fraction of peptide impurities and additional information obtained from the peptide related impurity profile indicates that in many cases the major related peptide impurities have been identified and quantified.The approach selected to obtain a KCRVOXT for the mass fraction of OXT is based on random-effects meta-analysis (DerSimonian-Laird (DSL) variance-weighted mean). The DSLmean takes into account the uncertainties of the results while introducing sufficient excess variance to allow for their observed dispersion resulting in a larger expanded uncertainty U(KCRVOXT). The KCRVOXT for CCQM-K115.b is 787.2 mg/g with a corresponding expanded uncertainty of the KCRVOXT of ±12.9 mg/g. All OXT mass fraction results except the result of NMIM are in agreement with the KCRVOXT. It should be pointed out that the mass balance approaches show smaller uncertainties than PICAA or PICqNMR approaches. Mass balance approaches seem to produce slightly higher OXT mass fractions while PICAA approaches deliver slightly lower OXT mass fractions.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Increased cell numbers improve marine biodegradation tests for persistence assessment

Currently available OECD biodegradation screening tests (BSTs) are not particularly suited for persistence screening. Their duration can be much less than international half-life thresholds for persistence and they are variable and stringent, therefore prone to false negatives. The present study extended test durations beyond 28 days and increased biomass concentrations for marine BSTs to better represent the microbial diversity inherent in the sampled environment. For this so-called environmentally relevant BST (erBST) marine cell concentrations were nominally increased 100-fold by tangential flow filtration. The marine erBST was validated against a standard BST using five 14C labeled reference compounds with a range of biodegradation potentials (aniline, 4-fluorophenol, 4-nitrophenol, 4-chloroaniline and pentachlorophenol) in a modified OECD 301B test. A full mass balance was collated to follow chemical fate in the tests. The erBST was more accurate and less variable than the comparator BST in assigning the reference compounds to their expected biodegradation classifications (non-persistent or potentially persistent). According to the REACH non-persistence criterion of ≥60% biodegradation over 60 days, the erBST correctly classified 60% of chemical replicates according to their expected biodegradation classification and had a coefficient of variation of 21% between replicates. In contrast, the BST correctly assessed 40% of reference chemicals in regards to their expected biodegradation classification with a coefficient of variation of 36%. All non-persistent chemicals showed increased degradation in the erBST, except for 4-chloroaniline, which did not degrade in either BST or erBST. Both tests showed no false positive results, correctly classifying the negative control pentachlorophenol as potentially persistent. Next, it is recommended to further validate the marine erBST in an inter-laboratory study incorporating different seawater sources to fully assess its variability and reliability.

The effect of temperature, residence time, and water-sludge ratio on hydrothermal carbonization of DAF dairy sludge

Batch hydrothermal carbonization (HTC) experiments were carried out using dissolved air flotation (DAF) dairy sludge in order to investigate the effects of changing temperature, residence time and water-sludge ratio on the yield and quality of the products. The highest solid hydrochar (HC) yield of 84 % (dry basis) and highest HC energy yield of 96 %, were achieved at a temperature of 250°C, a residence time of 4h and a water content of 96 wt.%. The wt.% of carbon and corresponding energy yield of HC increased with process severity while the oxygen and volatile matter contents decreased. Similarly, HC ash content and ash elemental composition increased and the resulting solid became more stable and hydrophobic. The majority of the compounds detected in the liquid product were acids, with carbon chain ranging between C1 and C10. The total acid-phenol concentrations increased with the severity of the HTC operating conditions, but remained around 2500 ppm. The hydrocarbon content of the gaseous product was low and a high CO2 concentration was observed, while H2S concentration increased significantly with the increase in temperature, residence time and water content. A degradation mechanism for proteins and fats was developed and a full elemental mass balance was performed.

Ibuprofen removal by a microfiltration membrane bioreactor during the startup phase

The behavior of ibuprofen (IBU) during the startup phase of a microfiltration membrane bioreactor (MBR) was determined. A full-scale experimental installation treating real urban wastewater was used for the study. The MBR was composed of an anoxic and an aerobic bioreactors working in pre-denitrification configuration, followed of a membrane reactor. A full mass balance was carried out to estimate the contribution of biotransformation and sorption to biomass to the overall removal of the IBU. During the startup phase of the MBR system there were significant oscillations of the operational variables, mainly of the sludge retention time (SRT); nevertheless, the capacity of the system for IBU removal was very high, with yields of over 94%, despite reaching minimum SRT values of 4.15 d. The main IBU removal occurs in the aerobic reactor, both in the liquid phase and the one associated with the sludge, while in the anoxic bioreactor the removal was scarce, although a certain transfer of IBU from the liquid phase to the sludge took place under anoxic conditions. Despite the high IBU removal yields during startup, the SRT was the most influential variable in IBU removal, an effect observed in all bioreactors, particularly in the anoxic one.

Full Mass Balance Analysis During Industrial Baker's Yeast Fermentation Shows New Perspectives for Biomolecule Recovery

Abstract This study aims to partially compensate the lack of reliable data regarding full mass balance analysis during industrial baker's yeast fermentation and the chemical composition of the resu...

Future retreat of Great Aletsch Glacier

AbstractWe model the future evolution of the largest glacier of the European Alps – Great Aletsch Glacier, Switzerland – during the 21st century. For that purpose we use a detailed three-dimensional model, which combines full Stokes ice dynamics and surface mass balance forced with the most recent climate projections (CH2018), as well as with climate data of the last decades. As a result, all CH2018 climate scenarios yield a major glacier retreat: Results range from a loss of 60% of today's ice volume by 2100 for a moderate CO2 emission scenario (RCP2.6) being in line with the Paris agreement to an almost complete wastage of the ice for the most extreme emission scenario (RCP8.5). Our model results also provide evidence that half of the mass loss is already committed under the climate conditions of the last decade.

The experimental determination of reliable biodegradation rates for mono-aromatics towards evaluating QSBR models

Quantitative Structure Biodegradation Relationships (QSBRs) are a tool to predict the biodegradability of chemicals. The objective of this work was to generate reliable biodegradation data for mono-aromatic chemicals in order to evaluate and verify previously developed QSBRs models. A robust biodegradation test method was developed to estimate specific substrate utilization rates, which were used as a proxy for biodegradation rates of chemicals in pure culture. Five representative mono-aromatic chemicals were selected that spanned a wide range of biodegradability. Aerobic biodegradation experiments were performed for each chemical in batch reactors seeded with known degraders. Chemical removal, degrader growth and CO2 production were monitored over time. Experimental data were interpreted using a full carbon mass balance model, and Monod kinetic parameters (Y, Ks, qmax and μmax) for each chemical were determined. In addition, stoichiometric equations for aerobic mineralization of the test chemicals were developed. The theoretically estimated biomass and CO2 yields were similar to those experimentally observed; 35% (s.d ± 8%) of the recovered substrate carbon was converted to biomass, and 65% (s.d ± 8%) was mineralised to CO2. Significant correlations were observed between the experimentally determined specific substrate utilization rates, as represented by qmax and qmax/Ks, at high and low substrate concentrations, respectively, and the first order biodegradation rate constants predicted by a previous QSBR study. Similarly, the correlation between qmax and selected molecular descriptors characterizing the chemicals structure in a previous QSBR study was also significant. These results suggest that QSBR models can be reliable and robust in prioritising chemical half-lives for regulatory screening purposes.

Long-Term Hydrolytic Degradation of the Sizing-Rich Composite Interphase

Glass fiber-reinforced composites are exposed to hydrolytic degradation in subsea and offshore applications. Fiber-matrix interphase degradation was observed after the matrix was fully saturated with water and typical water absorption tests according to ASTM D5229 were stopped. Due to water-induced dissolution, fiber-matrix interphase flaws were formed, which then lead to increased water uptake. Cutting sample plates from a larger laminate, where the fibers were running parallel to the 1.5 mm long short edge, allowed the hydrolytic degradation process to be studied. The analysis is based on a full mechanistic mass balance approach considering all the composite’s constituents: water uptake and leaching of the matrix, dissolution of the glass fibers, and dissolution of the composite interphase. These processes were modeled using a combination of Fickian diffusion and zero-order kinetics. For the composite laminate studied here with a saturated epoxy matrix, the fiber matrix interphase is predicted to be fully degraded after 22 to 30 years.