Description:
Pulp and paper wastewaters are challenging to treat due to their variability, complexity and toxicity. Membrane Bioreactor’s (MBR’s) provide high-quality filtrates but are subject to periods of low filterability / high capillary suction time (CST) which potentially limit their use in this application. There is a paucity of published literature concerning long-term operational issues in full-scale, industrial MBR’s. We hypothesised that either changes of bacterial population, alteration/reduction of bacterial metabolism or bacterial production of extra-cellular polymers (ESPs) increased CST and reduced filterability. This study, conducted over two years at the 16.4MLD Gippsland Water Factory, was structured to inform this bacterial centric hypothesis. However, no shifts in bacterial population were seen as causative of high CST and microbial stress levels and biological activity were observed to be low during high CST and no sign of toxicity was found. The strongest correlator with CST was the concentration of colloidal Total Organic Carbon of the mixed liquor suspended solids (MLSS) supernatant (following centrifugation). The carbonaceous colloids accumulated in the supernatant were named ‘Non-Centrifugable Total Organic Carbon’ (NCTOC). Their accumulation in the MLSS was found be due to their biologically refractory nature and their retention by the MBR membrane. The accumulation of NCTOC typically followed a period where the influent had a high colour and a high sodium to calcium ratio, which is consistent with a pulping by-product called ‘Black Liquor’. Additional experiments with Black Liquor allowed us to conclude that high CST can be produced by addition of Black Liquor.
Description:
Pulp and paper wastewaters are challenging to treat due to their variability, complexity and toxicity. Membrane Bioreactor’s (MBR’s) provide high-quality filtrates but are subject to periods of low filterability / high capillary suction time (CST) which potentially limit their use in this application. There is a paucity of published literature concerning long-term operational issues in full-scale, industrial MBR’s. We hypothesised that either changes of bacterial population, alteration/reduction of bacterial metabolism or bacterial production of extra-cellular polymers (ESPs) increased CST and reduced filterability. This study, conducted over two years at the 16.4MLD Gippsland Water Factory, was structured to inform this bacterial centric hypothesis. However, no shifts in bacterial population were seen as causative of high CST and microbial stress levels and biological activity were observed to be low during high CST and no sign of toxicity was found. The strongest correlator with CST was the concentration of colloidal Total Organic Carbon of the mixed liquor suspended solids (MLSS) supernatant (following centrifugation). The carbonaceous colloids accumulated in the supernatant were named ‘Non-Centrifugable Total Organic Carbon’ (NCTOC). Their accumulation in the MLSS was found be due to their biologically refractory nature and their retention by the MBR membrane. The accumulation of NCTOC typically followed a period where the influent had a high colour and a high sodium to calcium ratio, which is consistent with a pulping by-product called ‘Black Liquor’. Additional experiments with Black Liquor allowed us to conclude that high CST can be produced by addition of Black Liquor.
Description:
Sustainable reuse of winery wastewaters (WWW) via land application is of interest given the increasing industrialization of wine production. However, before WWW reuse can become widespread, its chemical composition and consequently its potential long-term impact need to be investigated. In this study, soluble materials in influent and effluent waters from different WWW treatment plants were analyzed at the molecular level using Solid Phase Micro Extraction Gas Chromatography/Mass Spectrometry (SPME GC–MS). The analytical focus was on key compound classes with potential for environmental harm, the majority of which were reduced by all treatments considered here. The effluents retained considerable quantities of recalcitrant phenolic compounds, which is of concern due to their potential phytotoxicity and proven resistance to aerobic degradation. This research highlights the importance of understanding the nature of organic material in WWW to ensure sustainable reuse.
Description:
The future development of a non-evaporative brown coal dewatering technique called Mechanical Thermal Expression (MTE) will produce large volumes of acidic, salty and organic rich product water. The overall viability of the MTE process will, in turn rely on the availability of a simple and energy-efficient water remediation strategy. Water treatment using the feed coal itself as an adsorbent may provide such an option. In this study a fixed-bed configuration of raw Loy Yang coal was employed. When the adsorbent was first exposed to MTE water, most of the dissolved organic carbon (DOC) and most of the multivalent cations in solution were adsorbed. However, breakthrough of monovalent cations occurred after a volume of MTE water equivalent to just two times the volume of the adsorbent bed itself (2 bed volumes (BVs)) had passed, with only small proportions of Na and K being retained. About 60% (30 mg/g, db) of the dissolved organic carbon (DOC) and about 25% (0.16 mmol/g, db) of the total cations were removed after passing 20 BV of MTE water through the adsorbent bed. This corresponds to an adsorbent requirement that is 1.4% of the amount of coal to be dewatered. Thus, the use of brown coal adsorbent beds may be an effective primary water treatment option. However specific organic and inorganic components are likely to require further reduction prior to discharge to the environment
Description:
This work is part of a series of studies dealing with the evaluation of the effects of major elements of solid waste, especially metallic oxides, nitrates, sulfates, and chlorides, on the sintering and the densification of calcium hydroxyapatite (Ca-HAP) adsorbent. The effects of chloride salts of potassium (KCl) and zinc (ZnCl2) on sintering and densification of Ca-HAP were studied using surface area reduction and shrinkage measurements. The addition of KCl (2% w/w) activated the sintering process by bringing a swift reduction in surface area and lowering the densification temperature. However, a low final densification was achieved. Increasing the amount of this additive to 10% w/w further lowered the final densification and lowered the densification temperature of hydroxyapatite by 150 oC. On the other hand, the addition of 2 wt % of ZnCl2 deactivated the sintering process by slowing down the densification process and raising the densification temperature. However, the reduction of surface area was comparable to that of Ca-HAP. The densification rate contained two or more rate maxima indicating the additives (salts) bring multiple speeds in the densification process.
Description:
The objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130 degrees C, 150 degrees C, and 170 degrees C) and outlet (55 degrees C, 65 degrees C, and 75 degrees C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130 degrees C and 150 degrees C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170 degrees C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130-65 degrees C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 +/- 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.
Description:
The objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130 degrees C, 150 degrees C, and 170 degrees C) and outlet (55 degrees C, 65 degrees C, and 75 degrees C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130 degrees C and 150 degrees C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170 degrees C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130-65 degrees C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 +/- 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.
Description:
This paper presents a numerical study of soil fluidisation induced by local leakage from a buried pipe using the coupled discrete element and lattice Boltzmann approach (DEM–LBM). The behaviour of the system is studied using different flow rates and initial bed heights. The excess pore pressure distribution and the soil behaviour due to a localised leak are investigated and compared with previous experimental findings. The comparison indicates that DEM–LBM is capable of capturing the leakage–soil interaction at the particle scale. Moreover, as the flow distribution is found to be one-dimensional in the radial direction rather than one-dimensional in the vertical direction, an extension to the Ergun flow equation is derived and the numerically measured fluidising pressure shows good agreement with this analytical solution. In addition, as indicated by the numerical results and the derived analytical solution, the relationship between fluidising pressure and pipe buried depth as well as leak size is also established. The simulation results suggest that DEM–LBM is a promising tool to carry out further studies into the internal fluidisation phenomenon.
Description:
This paper presents the results from the investigation of arsenopyrite oxidation via mechano-chemical activation, using a stirred mill. Water and hydrogen peroxide were chosen as the lixiviant and oxidant, respectively, and maintained at a relatively low temperature (50 °C). The milling media size, mill speed, slurry percent solids and amount of H2O2 added were all kept constant throughoust these experiments. The only operational variable for this investigation was the milling time, which results in increasing levels of specific energy provided by the mill. The products of activated arsenopyrite are characterised in terms of phase composition, particulate and structural characteristics, along with reactivity. Mechano-chemical activation of arsenopyrite under oxidizing conditions shows a maximum dissolution of around 9 wt% for iron and 7 wt% for arsenic after 2 h of milling. After 3 h of milling, the main phase present is found to be amorphous in nature.
Description:
In this study, a novel biorefinery concept producing carbon fibre-poly(butylene succinate) composite foam (CPC foam) from lignocellulose and CO 2 is modelled. The biodegradable nature of poly(butylene succinate) would allow for easy carbon fibre recovery from the CPC foam for reuse at the end of product lifecycle, thus allowing for a circular materials flow. Technical simulation results show the biorefinery consumes 417 kg of biomass, 33 kg of CO 2 , 86 kg of methanol, 23 kg of acetic anhydride, 130 kWh of electricity and 1166 kW of heat per hour. The facility generates 72 kg of CPC foam, 82 kg of carbon fibre, 24 kg of tetrahydrofuran and 50 kg of dimethyl ether (DME). DME is used to fulfil parasitic electricity requirement. These results demonstrate the technical viability of this biorefinery although, research is needed to reduce parasitic energy demand. This carbon negative biorefinery avoids carcinogens and halogens for polymeric materials synthesis by utilising green chemistry principles and lignocellulose feedstock.
Description:
In this study, a novel biorefinery concept producing carbon fibre-poly(butylene succinate) composite foam (CPC foam) from lignocellulose and CO 2 is modelled. The biodegradable nature of poly(butylene succinate) would allow for easy carbon fibre recovery from the CPC foam for reuse at the end of product lifecycle, thus allowing for a circular materials flow. Technical simulation results show the biorefinery consumes 417 kg of biomass, 33 kg of CO 2 , 86 kg of methanol, 23 kg of acetic anhydride, 130 kWh of electricity and 1166 kW of heat per hour. The facility generates 72 kg of CPC foam, 82 kg of carbon fibre, 24 kg of tetrahydrofuran and 50 kg of dimethyl ether (DME). DME is used to fulfil parasitic electricity requirement. These results demonstrate the technical viability of this biorefinery although, research is needed to reduce parasitic energy demand. This carbon negative biorefinery avoids carcinogens and halogens for polymeric materials synthesis by utilising green chemistry principles and lignocellulose feedstock.
Description:
To study the interaction between sand particles and geogrids, pullout tests were performed on one type of geogrid in Pingtan medium sand. The sand motion around the ribs was captured by high-resolution digital camera and CCD camera. The images were analysed with the aid of digital photography measurement and micro-image analysis. Microscopic particle motion and displacement fields around the transverse ribs were then obtained to verify the macro behaviour of the sand–rib interaction. It was found that the thickness of shear band increases with the normal stress applied, and the shear zone is asymmetrical to the soil–rib interface. A near wedge shape shear zone was observed by analysing the shear strain around the ribs, which indicated that a punching shear failure mechanism may be applicable to the tested geogrid in medium-dense sand. Comparison of various models for bearing capacity of geogrids shows that the size and shape of bearing members should be considered in the calculation of bearing resistance of geogrids.
Description:
A numerical model is employed to simulate a single tube reactor featuring a downward particle flow counter to an upward inert gas flow for ceria reduction in the dilute flow regime. The coupled phenomena of mass and momentum transfer as well as chemical kinetics are simulated assuming isothermal operation for the reactor. The model predicts the reduction extent under varying reaction kinetics as well as design and operational choices. The reduction extent is found to increase with the reaction rate constant until achieving the thermodynamic upper limit at a certain critical value. This critical rate constant signifies a transition from a chemical kinetics limited conversion to a gas advection limited conversion. The effect of the reactor length and the particle size on reaction extent is studied for a range of realistic cases. An empirical correlation is developed to quantify the effects of particle and gas flow rates on reduction extent at both slow and fast kinetics. The present work offers insights to help guide reactor design and operation towards achieving the maximum reduction extent. (C) 2020 Elsevier Ltd. All rights reserved.
Description:
The present paper describes the characterization of Pakistan lignite coal, derived humic acids (HAL) and nitrohumic acids (NHA) along with the standard leonardite humic acids (LHA). The study utilized chromatographic and spectroscopic techniques to characterize the structure of coal and derived materials. Pyrolysis coupled to gc/ms was conducted with and without methylating agent (tetramethyl ammonium hydroxide). The pyrolysis study resulted in releasing mainly fatty acid methyl esters, different series of hydrocarbons and α, ω-dicarboxylic acid methyl esters. Triterpenoids, syringic and ρ-coumaric compounds and aromatic compounds derived from lignin moieties were also detected. Fourier transform infrared (FT-IR) and NMR data helped to evaluate the influence of coal rank on regeneration and nitration processes with respect to chemical structural composition of coal and derived materials. FT-IR spectra of four materials were similar except that NHA showed an absorption band at 1532cm−1, thus confirming the presence of -NO2 groups. 13C NMR indicated higher aromaticity and less hydroxylalkyl material in HAL than NHA. The elemental composition and acid functional group content of four materials were also reported. The combination of results from different analytical techniques gives an improved understanding of the Pakistan coal nature and helpful for its future utilization.