Applying infrared thermography and image analysis to dilute 2-phase particulate systems: hot particle curtains

Particle curtains occur in industrial drying and in solar particle receivers and are defined as a stream of particles falling a fixed distance through a gas or fluid phase. In industrial drying optimising heat and mass transfer between the cascading particles and the drying medium is essential for enhancing energy efficiency and reducing emissions. Modelling these devices via pragmatic process systems models and/or with computational fluid dynamics models can contribute to enhanced design and a better understanding of the fundamental processes that occur. Validation of curtain modelling is critical to building confidence in the resultant predictions, but unfortunately traditional methods such as discrete temperature measurement using probes are time consuming and can disturb the flow field. Infrared thermography is an image-based technique with the potential to alleviate some of these issues and to generate whole of field temperature data, well-suited to model validation. In this paper infrared thermographic images of hot particle curtains falling through still air are presented. Image analysis methods for adjusting and scaling images as well as detecting the curtain edges are also described. Experiments involving hot particle curtains (403k-413K) falling through a narrow slot (150×20-60 mm) in a room filled with still air (295K-300K) are presented. Curtain widths were varied by varying the slot width (20 mm and 60 mm) and a range of mass flow rates (0.04 kg/s-0.155 kg/s) and particle diameters (290 μm and 400 μm) were examined. Curtain shape, as defined by the edges of the curtains, was determined using methods adapted from image analysis. The 2D thermal images showed that the shapes of the curtains are strongly dependent on slot width or initial solids volume fraction, which has implications for maximising heat transfer in particle curtain processes

Drying Kinetics of Macroalgae as a Function of Drying Gas Velocity and Material Bulk Density, Including Shrinkage

Macroalgae have many potential applications and can make important contributions to sustainability and circular economy objectives. Macroalgae are degradable high-moisture biomaterials and drying is a necessary step, but drying is an energy and capital-intensive part of their production process. This study presents convective drying curves for commercially promising fresh and saltwater species (U. ohnoi and O. intermedium), obtained over a range of industry-relevant drying gas velocities (0.3–2 m/s) and material bulk densities (33–100 kg/m3). Pragmatic diffusion-based drying models that account for the influence of drying gas velocity, material bulk density, and material shrinkage are presented. Results provide critical insights into the validity of diffusion model assumptions for compressible biomaterials and new mechanisms describing gas penetration into such materials are proposed. The drying models provided in this work demonstrate a high degree of accuracy for both species

Equilibrium moisture and drying kinetics modelling of macroalgae species Ulva ohnoi and Oedogonium intermedium

Algae-based products have applications in the food and pharmaceutical industries, bioremediation of waste streams and biofuel production. Drying has been recognised to constitute the largest energy cost in algae processing, yet there is limited data or modelling characterising the drying kinetics of macroalgae. This research modelled the equilibrium moisture content of two macroalgae species, Ulva ohnoi, a saltwater alga and Oedogonium intermedium, a freshwater alga. The Guggenheim–Anderson–de Boer model was found to best represent experimental equilibrium moisture contents. Drying rate curves obtained under both convective and radiative conditions were fitted to an analytical solution of Fick’s second law, including the modelled equilibrium moisture values. Effective diffusivity values for the two species are presented

A life cycle assessment of recycled polypropylene fibre in concrete footpaths

This study assesses the environmental impact of four alternatives for reinforcing 100 m² of concrete footpath (Functional Unit, FU) by using cradle to gate life cycle assessment (LCA), based on the Australian context. Specifically, the four options considered are a) producing steel reinforcing mesh (SRM), b)producing virgin polypropylene (PP) fibre, c) recycling industrial PP waste and d) recycling domestic PP waste. The FU yields 364 kg of SRM (in a) and 40 kg of PP fibres (in b, c and d), necessary to achieve the same degree of reinforcing in concrete. All the activities required to produce these materials are considered in the study, namely manufacturing and transportation, and also recycling and reprocessing in the case of industrial and domestic recycled PP waste fibres. These processes are individually analysed and quantified in terms of material consumption, water use, and emissions into the environment. This allows for the impacts from producing recycled fibres to be compared with those from producing virgin PP fibre and SRM, which are traditionally used. The LCA results show that industrial recycled PP fibre offers important environmental benefits over virgin PP fibre. Specifically, the industrial recycled PP fibrecan save 50% of CO₂ equivalent, 65% of PO₄ equivalent, 29% of water and 78% of oil equivalent, compared to the virgin PP fibre. When compared to the SRM, the industrial recycled PP fibre can save 93% of CO₂ equivalent, 97% of PO₄ equivalent, 99% of water and 91% of oil equivalent. The domestic recycled PP fibre also generates reduced environmental impacts compared to virgin PP fibre, except for higher consumption of water associated with the washing processes

Occurrence of emerging contaminants in biosolids in northern Queensland, Australia

This study aims to identify and quantify different classes of emerging contaminants (ECs), such as pharmaceutical and personal care products (PPCPs), per-and polyfluoroalkyl substances (PFAS), heavy metals (HMs), polycyclic musks (PMs) in biosolids from different sewage treatment plants (STPs) from regional councils across Northern Queensland, Australia. Biosolids samples were named BS1 to BS7 for each council. The results revealed significant variations in the concentrations of different ECs in biosolids which could be explained in some instances by the characteristics of the upstream sewage network. For instance, BS4-biosolids from a small agricultural shire (largely sugarcane) showed the highest concentration of zinc and copper, which were 2430 and 1050 mg/kg, respectively. Among PPCPs, the concentration of ciprofloxacin was found to be the highest in BS3 and BS5, two large regional council areas which are a mix of domestic and industrial (predominantly domestic) biosolids of 1010 and 1590 ng/g, respectively. In addition, the quantity of sertraline was consistently high in all biosolids except from BS7, one of the smaller regional councils, which is indicative of the domestic catchments attached. PFAS compounds were detected in all biosolids samples except in BS6, one of the small (agricultural and tourist) catchments. Two PFAS compounds emerged as the most common pollutants that were perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The largest industrial catchment biosolids, BS2 showed the highest concentration of PFOS at 253 ng/g, while the smallest regional council, BS7 showed the maximum concentration of 7.90 ng/g of PFOA. Overall, this study concludes that certain ECs such as HMs, antibiotics, PFOS and PFOA in biosolids may pose high environmental risks

Testudines as sentinels for monitoring the dissemination of antibiotic resistance in marine environments: an integrative review

Dissemination of antibiotic resistance (AR) in marine environments is a global concern with a propensity to affect public health and many ecosystems worldwide. We evaluated the use of sea turtles as sentinel species for monitoring AR in marine environments. In this field, antibiotic resistant bacteria have been commonly identified by using standard culture and sensitivity tests, leading to an overrepresentation of specific, culturable bacterial classes in the available literature. AR was detected against all major antibiotic classes, but the highest cumulative global frequency of resistance in all represented geographical sites was against the beta-lactam class by a two-fold difference compared to all other antibiotics. Wastewater facilities and turtle rehabilitation centres were associated with higher incidences of multidrug-resistant bacteria (MDRB) accounting for an average of 58% and 49% of resistant isolates, respectively. Furthermore, a relatively similar prevalence of MDRB was seen in all studied locations. These data suggest that anthropogenically driven selection pressures for the development of AR in sea turtles and marine environments are relatively similar worldwide. There is a need, however, to establish direct demonstrable associations between AR in sea turtles in their respective marine environments with wastewater facilities and other anthropogenic activities worldwide

Microbial and thermal treatment techniques for degradation of PFAS in biosolids: A focus on degradation mechanisms and pathways

Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals detected in biosolids worldwide, which have become a significant concern for biosolids applications due to their increasing environmental risks. Hence, it is pivotal to understand the magnitude of PFAS contamination in biosolids and implement effective technologies to reduce their contamination and prevent hazardous aftermaths. Thermal techniques such as pyrolysis, incineration and gasification, and biodegradation have been regarded as impactful solutions to degrade PFAS and transform biosolids into value-added products like biochar. These techniques can mineralize PFAS compounds under specific operating parameters, which can lead to unique degradation mechanisms and pathways. Understanding PFAS degradation mechanisms can pave the way to design the technology and to optimize the process conditions. Therefore, in this review, we aim to review and compare PFAS degradation mechanisms in thermal treatment like pyrolysis, incineration, gasification, smouldering combustion, hydrothermal liquefaction (HTL), and biodegradation. For instance, in biodegradation of perfluorooctane sulfonic acid (PFOS), firstly C−S bond cleavage occurs which is followed by hydroxylation, decarboxylation and defluorination reactions to form perfluoroheptanoic acid. In HTL, PFOS degradation is carried through OH−catalyzed series of nucleophilic substitution and decarboxylation reactions. In contrast, thermal PFOS degradation involves a three-step random-chain scission pathway. The first step includes C−S bond cleavage, followed by defluorination of perfluoroalkyl radical, and radical chain propagation reactions. Finally, the termination of chain propagation reactions produces very short-fluorinated units. We also highlighted important policies and strategies employed worldwide to curb PFAS contamination in biosolids

Emerging contaminants in biosolids: presence, fate and analytical techniques

Emerging contaminants (ECs) represent a small fraction of the large chemical pollution puzzle where a wide variety of potentially hazardous chemicals reach the environment, and new compounds are continuously synthesized and released in wastewater treatment plants and ultimately in effluent and biosolids. ECs have been classified into various categories; however, this article focuses on the fate of major categories, namely pharmaceutical and personal care products (PPCPs), per-and poly-fluoroalkyl substances (PFAS), flame retardants, surfactants, endocrine-disrupting chemicals (EDCs), and microplastics (MPs). These ECs when discharged to sewer and downstream wastewater treatment plants can undergo further transformations and either degrade, persist or convert into by-products which have the potential in some cases to be more hazardous. Because of potential dangerous impacts of the availability of these contaminants in the environment, information on the fate and behavior of these pollutants is highly important to develop new strategies, such as the regulation of chemicals imported into Australia and Australian consumer goods and environmental policies to mitigate them in a sustainable way. Moreover, advanced technologies are required for the detection and identification of novel contaminants emerging in the environment at ultra low levels. The application of chromatographic techniques coupled with mass spectroscopy has provided attractive breakthroughs to detect new emerging contaminants. However, it is crucially important to understand the sensitivity and robustness of these analytical techniques when dealing with complex matrices such as biosolids. In addition, most of the literature was focused on selected compounds or a family of compounds and the existing reviews have paid less attention to examine the formation of metabolites during the wastewater treatment process and their impacts on the ecosystem. This review presents an overview of the presence of different classes of ECs around the world, their quantification from different sources like wastewater (influents or effluents), sludge and biosolids. In addition, the transformation of ECs during the treatment process, the formation of intermediate products and their impacts on the environment are also critically discussed. Three major steps of ECs analysis include sample preparation, extraction and clean-up, and analysis; hence, different methods employed for extraction and clean-up, and analytical techniques for identification are thoroughly discussed, their advantages and limitations are also highlighted. This comprehensive review article is believed to enhance the understanding of ECs in sewage sludge and would be useful to the readers of the relevant communities and various stakeholders to investigate potential technologies to maximize destruction of ECs

Designing sustainability curricula: a case following chemical engineering curriculum redesign

Developing an engineering student's awareness of sustainability through the embedding of sustainability curricula is widely considered to be essential to modernising chemical engineering degree programs. In this chapter, the chemical engineering program at James Cook University is used as a case study to illustrate the design and sequencing of embedded curricula associated with developing a students' awareness of sustainability. There are a wide range of examples of skills, techniques, and characteristics associated with developing this awareness. In this chapter, an approach is described whereby a set of generic and interdisciplinary capabilities are developed to provide a degree of flexibility in how sustainability is interpreted and taught. A cognitive learning matrix is utilised as a design tool that facilitates determination of new subject learning outcomes aligned with the sustainability capabilities. A variety of curriculum examples are introduced and described

Scaffolding curricula in chemical engineering degree programs in order to develop student’s awareness of sustainability

Global challenges of climate change, resource scarcity, inequality and anthropogenic pollution make a chemical engineering student’s “awareness of sustainability” an important competency to develop. However, embedding sustainability curricula into chemical engineering programs remains a difficult task, often viewed by academics through the prism of new curricula fighting for a place in an already tightly-packed traditional degree program. Thus it has typically been relegated to the peripheries of chemical engineering education, via electives or piecemeal efforts in the knowledge domain. For the past 10 years James Cook University’s Chemical engineering program has been designing and implementing curricula to produce graduates with an “awareness of sustainability”. New sustainability-related assessment and sustainability-associated learning outcomes have been created and embedded across all year levels in the UG degree program, including integration into traditional curricula. Emphasis in this paper is placed on describing the sequence of learning outcomes that facilitate scaffolding of student learning in the area of sustainability. Examples from the first and second years of the degree are provided in order to highlight the foundational knowledge and skills that underpin an awareness of sustainability. The extension of these knowledge and skills into open-ended and problem-based learning exercises such as the capstone design project in fourth year is explained. Examples of sustainability-related assessment from JCU’s capstone subject are presented in order to illustrate how students demonstrate competency in this area