Engineered biochar – A sustainable solution for the removal of antibiotics from water

Antibiotic contamination and the spread of antimicrobial resistant bacteria are global environmental issues. Given the growing consumption of antibiotics, it is crucial to reduce their presence in the environment. Adsorption is one of the most efficient methods for removing contaminants from water and wastewater. For this process to be effective, it is of key importance to identify adsorption mechanisms that allow an efficient and selective adsorbent to be chosen. Carbon-based materials (including activated carbon, biochar and black carbon) are typically used for the adsorptive removal of antibiotics. To enhance the efficiency of adsorption of pharmaceuticals, engineered biochars (physically, chemically and biologically modified biochar) and their composites have attracted increasing interests. Biochar-based sorbents can be produced from various feedstocks, including waste products. The use of “green”, low cost or sustainable biochar for contaminant sorption yields economic and environmental benefits. Moreover, this is in line with global trends in creating a circular economy and sustainable development. This paper collates the most recent data on the consumption of antibiotics, their related environmental contamination, and their removal using biochar-based materials. Special attention is paid to the newly emerging approaches of biochar modification and biochar composites in relation to the antibiotic removal from water. © 2020 Elsevier B.V

A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

Optimization and analysis of syngas production from methane and CO<inf>2</inf> via Taguchi approach, response surface methodology (RSM) and analysis of variance (ANOVA)

This study aims to figure out syngas production from methane and CO2 where the catalytic partial oxidation of methane over a rhodium-based catalyst bed in a Swiss-roll reactor is explored. The syngas yield from the best combination of gas hourly space velocity (GHSV), oxygen-to-methane molar ratio (O2/C ratio), and CO2-to- O2 molar ratio (CO2/O2 ratio) is acquired by a two-stage optimization, namely, the Taguchi approach followed by response surface methodology (RSM). In the first stage, the Taguchi approach suggests that the influences of the factors on the syngas yield are ranked by O2/C ratio > CO2/O2 ratio > GHSV, and the maximum syngas yield is 2.191 mol∙(mol-CH4)−1. Thereafter, the ranges of the three operating parameters are narrowed, and RSM and analysis of variance are used in the second stage to obtain a more precise optimization. In this stage, the significance of the regression coefficients indicating that GHSV and the combination of GHSV and O2/C ratio are pronounced. Based on the Box-Behnken experimental design, RSM analysis leads to the maximum syngas yield of 2.304 mol∙(mol CH4)−1, lifting the syngas yield by 5.15% in the second stage. These results reveal that the syngas yield from the two-stage optimization (Taguchi + RSM) is more efficient than from the single-stage

Insights into upstream processing of microalgae:A review

The aim of this review is to provide insights into the upstream processing of microalgae, and to highlight the advantages of each step. This review discusses the most important steps of the upstream processing in microalgae research such as cultivation modes, photobioreactors design, preparation of culture medium, control of environmental factors, supply of microalgae seeds and monitoring of microalgal growth. An extensive list of bioreactors and their working volumes used, elemental composition of some well-known formulated cultivation media, different types of wastewater used for microalgal cultivation and environmental variables studied in microalgae research has been compiled in this review from the vast literature. This review also highlights existing challenges and knowledge gaps in upstream processing of microalgae and future research needs are suggested

Removal of organic acids from water using biochar and petroleum coke

Alberta produces large volumes of oil sands process-affected water (OSPW) as a result of bitumen extraction and upgrading processes. Naphthenic acids (NAs) and other organic acids (OAs) comprise the main constituents of OSPW that can be acutely toxic to aquatic life. The recycling, safe return or storage of OSPW into the environment is a major challenge for the oil sands industry. Therefore, proper treatment technologies that are effective but inexpensive are needed. In this study, we tested the ability of a biochar (BC) produced from wheat straw and petroleum coke (PC) to remove two model organic acids (OAs) from aqueous solution: lauric acid (LA) and 1-methylcyclohexenecarboxylic acid (MCA). The results showed that BC was generally a more effective sorbent than PC, likely because BC has higher surface area and higher functional group densities than PC. More LA than MCA sorbed to both BC and PC due to the saturated 12-carbon chain of LA which renders it more hydrophobic than MCA. An admixture of BC and PC removed more LA from solution that was expected from its component parts, which may indicate a synergy between BC and PC in removing certain OAs from solution. This study shows that BC and PC might be useful materials for on-site treatment of organic acids. However, the use of PC may also be problematic due to release of significant heavy metals and sulfur to aqueous solution

Value-added chemicals from food supply chain wastes : state-of-the-art review and future prospects

202308 bcchAccepted ManuscriptRGCOthersHong Kong Environment and Conservation Fund; Hong Kong Polytechnic University; Environment and Conservation FundPublishe

Biochar for urban agriculture: Impacts on soil chemical characteristics and on Brassica rapa growth, nutrient content and metabolism over multiple growth cycles

With possible food crises looming in the near future, urban farming, including small-scale community and home gardens for home consumption, presents a promising option to improve food security in cities. These small-scale farms and gardens often use planter boxes and raised beds filled with lightweight soil or potting mixes. While previous studies on biochar focused on its application on large-scale contiguous farmlands, this study aimed to evaluate the suitability of biochar as a partial soil substitute to produce a durable and lightweight soil-biochar mix for small-scale urban farms. The effects of biochar on the chemical properties of the soil-biochar mix, crop yield and, particularly, crop nutrients and metabolic content were assessed. A germination test using pak choi seeds (Brassica rapa L. cultivar group Pak choi, Green-Petioled Form) showed that the biochar contained phytostimulants. Through a nursery pot experiment over four growth cycles, biochar treatments performed better than pure soil at retaining water-soluble NO3− and K+ ions, but were worse at retaining PO43− ions. Nonetheless, despite its positive effect on soil NO3− retention, biochar application did not improve crop yield significantly when the application rate varied from 0% to 60% (v/v). Untargeted metabolomic analyses showed that biochar application may increase the production of carbohydrates and certain flavonoids and glucosinolates. The results of this study showed that biochar can potentially be used to improve pak choi nutritional values and applied in large quantity to obtain a lightweight soil mix for urban farming