The Effect of Exogenous Oxytetracycline on High-Temperature Anaerobic Digestion of Elements in Swine Wastewater

Tetracycline antibiotics (TCs) are a common type of antibiotic found in swine wastewater. Oxytetracycline (OTC) is a significant type of TC. This study mainly examined the influence of OTC on high-temperature anaerobic digestion by adding OTC to collections of swine wastewater at different times during the digestion process. The results showed that high-temperature anaerobic digestion was suitable for the removal of TCs, with an 87% OTC removal efficiency achieved by day 20. Additionally, OTC added from external sources was found to inhibit the chlortetracycline degradation process and affect the first-order degradation kinetic model of TCs. Complexation reactions were the main ways in which OTC affected the heavy metal content of the water. The exogenous addition of OTC was found to inhibit the activity of some digester microbial strains, reduce the proportion of dominant strains, such as MBA03, and kill certain specific strains. This performance alteration was most obvious when OTC was added in the middle of the reaction.

Determination of thermal degradation for high-performance thermoplastic composites manufactured by laser-assisted automated fibre placement

In in situ consolidation of thermoplastic composites by laser-assisted automated fibre placement (AFP), high laser irradiation temperature can improve the fluidity of the resin matrix, which usually enhances the performances of composites. However, it leads to a tendency for thermal degradation as the resin matrix of the composites is exposed to high temperatures for a long time. The thermal degradation behaviours of continuous carbon fibre (CF)-reinforced polyphenylene sulfide (PPS) composites during in situ consolidation by laser-assisted AFP were studied. A thermogravimetric analysis shows that the thermal degradation of CF/PPS composites is quite complex, with multi-step reactions. The thermal degradation of the composites was further analysed via kinetic methods. A thermal degradation kinetic model of the resin matrix was obtained and verified. According to the kinetic model, the thermal degradation of the composites under different placement conditions was predicted. The results were confirmed by Fourier-transform infrared spectroscopy and scanning electron microscopy. With the combination of the kinetic model, AFP in situ consolidation, and characterisation techniques, processing parameters such as laser irradiation temperature and placement speed can be adjusted and optimised.

Bacterial community shift and effects of the inclusion of a mixed psychrotrophic bacteria strain for sewage treatment in constructed wetland in winter seasons

The mechanism of wastewater treatment based on psychrophilic strains to improve the denitrification efficiency of constructed wetlands at low temperatures has already become a new hotspot. In this study, three mixed psychrophilic strains (Psychrobacter TM-1, Sphingobacterium TM-2 and Pseudomonas TM-3) with high capacity of denitrification were added into a vertical-flow constructed wetlands (CWs), and the effect of the mixed strains on CWs sewage treatment was evaluated. The removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN) and total phosphorus (TP) was quantified to establish the degradation kinetic model and determine the best dosage of the mixed strains. The effect mechanism of the mixed strains on indigenous microbial community and the change of sewage treatment performance in low temperature constructed wetlands was clarified by high-throughput sequencing technology. The results showed that the mixed strains can effectively remove the organic pollutants (nitrogen and phosphorus) and the optimum dosage of the mixed strain was 2.5%,with average removal rates of 1.52, 2.12, 2.07 and 1.29 times than those of the control. Meanwhile, the dominant strains in the CWs were Proteobacteria (31.23–44.34%), Chloroflexi (12.04–19.05%), Actinobacteria (10.6-20.62%), Acidobacteria (8.23–11.65%), Firmicutes (2.23–15.95%) and Bacteroidetes (4.01–18.9%). These findings provide a basis for the removal of pollutants in constructed wetlands at low temperature.

Kinetic of polyphenol losses during convection drying of cashew (Anacardium occidentale L.) apples

Lowering manufacturing costs and utilization of by-products are urgent requirements to improve the competitiveness of Vietnamese cashew nuts in the world market. Heat treatment strategies such as drying are common techniques to process waste sources into a food source. The degradation of polyphenol, vitamin C, and tannins in the process represent a major obstacle in maintaining the nutritional quality of cashew pulp as well as in de-acridization of raw materials. This work firstly attempted to determine the optimal convection drying conditions that gave the highest nutritional quality contents in cashew apples. Then, the polyphenol degradation kinetic of cashew apple material during the drying process was examined in zero-order and first-order kinetic models. The results suggested the best contents of polyphenol, vitamin C and tannin could be attained at the drying process at 55°C for 275 mins. In addition, the first-order kinetic model was used to describe the decomposition of polyphenols during the drying process and the equation to predict the residual polyphenol content in cashew apple was formed to optimize the process. Research parameters provide a database for the following processing processes in the production of cashew-derived food products.

Mechanistic Model and Optimization of the Diclofenac Degradation Kinetic for Ozonation Processes Intensification

This work focused on estimating the rate constants for three ozone-based processes applied in the degradation of diclofenac. The ozonation (Oz) and its intensification with catalysis (COz) and photocatalysis (PCOz) were studied. Three mathematical models were evaluated with a genetic algorithm (GA) to find the optimal values for the kinetics constants. The Theil inequality coefficient (TIC) worked as a criterion to assess the models’ deviation. The diclofenac consumption followed a slow kinetic regime according to the Hatta number (Ha<0.3). However, it strongly contrasted with earlier studies. The obtained values for the volumetric rate of photon absorption (VRPA) corresponding to the PCOz process (1.75×10−6 & 6.54×10−7 Einstein L−1 min−1) were significantly distant from the maximum (2.59×10−5 Einstein L−1 min−1). The computed profiles of chemical species proved that no significant amount of hydroxyl radicals was produced in the Oz, whereas the PCOz achieved the highest production rate. According to this, titanium dioxide significantly contributed to ozone decomposition, especially at low ozone doses. Although the models’ prediction described a good agreement with the experimental data (TIC<0.3), the optimization algorithm was likely to have masked the rate constants as they had highly deviated from already reported values.