Nitrogen compounds removal in a packed bed external loop airlift bioreactor

A packed bed external loop airlift bioreactor (PBELAB) was proposed as an alternative treatment system for wastewater containing ammonia and nitrate compounds. The 60L PBELAB consisted of aeration and non-aeration zones, both of which were packed with plastic bioballs to enhance the surface area for the attachment of bacteria. The system was able to achieve complete removal of all nitrogen compounds with simultaneous nitrification and denitrification, i.e., ammonia was decomposed in the aeration zone and nitrate was biodegraded in the non-aeration zone. At normal operation, the nitrification rate obtained from the system was in the range of 0.14-0.87 gNH₃-N/m²d and the denitrification rate was 0.04 gNO₃-N/m²d. The factors found to have great influence on the system included dissolved oxygen concentration and biofilm thickness. In addition, PBELAB was proven to perform well under nitrate shock load condition.     

Novel pineapple leaf fibre composites coating with antimicrobial compound as a potential food packaging

Biodegradable packaging coated with antimicrobial compounds has emerged as a new type of food packaging with potential to enhance food safety, extend shelf life and minimize plastic pollution. We have developed a polylactic acid (PLA) composite pineapple leaf fibre (PALF) biopolymer to fulfil the high demand of biodegradable materials for a potential use in food packaging. Our formulation with 10% pineapple fibre PLA/PALF composites exhibited enhanced melting temperatures and heat resistance, with a 44% reduction in the tensile strength and 2.7-fold reduction on the strain at the break when compared with neat PLA. To impart antimicrobial activity, the PLA/PALF was coated with crude supernatants isolated from Pediococcus pentosaceus PP04 containing 1.3% w/v of nisin. This material coated with the crude extract was shown to inhibit the growth of Bacillus cereus ATCC 11778, Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311, and Escherichia coli ATCC 8739 in culture conditions, as well as minimizing the number of the tested pathogens on coated material surfaces.     

Hybrid procedure to determine optimal workforce without noise hazard exposure

Hearing loss is a major occupational health problem among industrial workers. Repetitive exposure to loud noise increases the risk of hearing loss. An administrative noise control such as job rotation can help to reduce workers’ daily noise exposures. In a case where noise levels are excessively high, it is often necessary to assign additional workers to the current workforce to alleviate daily noise exposures that individual workers receive. This paper presents four solution algorithms (three approximations and one exact) to determine a minimum number of workers and their work assignments to attend noisy workstations without noise hazard exposure (that is, daily noise exposure does not exceed 90 dBA). Then, a hybrid procedure which utilizes the four algorithms successively is proposed to improve the solution procedure. Based on a computational experiment on 300 test problems, it is found that the hybrid procedure outperforms all four algorithms (when utilized separately) and is able to find an optimal solution for 88% of the test problems.     

Repeated phosphate removal from recirculating aquaculture system using cyanobacterium remediation and chitosan flocculation

Unicellular cyanobacterium Synechocystis sp. was used for phosphate removal in a recirculating aquaculture system. The cell harvesting was performed using chitosan solution in this study. The parameters (i.e. cell density, pH of cell suspension and chitosan concentration) affecting the flocculation efficiency of chitosan were investigated. With the optimal condition, the repeated flocculation for phosphate removal in a photobioreactor was demonstrated. The results show that the flocculation efficiency of chitosan depends on cell density, pH of cell suspension and chitosan concentration. The optimal flocculation process could be accomplished by adjusting the pH to 7.2 before adding 20 mg/L chitosan followed by pH adjustment to 7.5. With single inoculation, the sequential process of phosphate removal using cyanobacterial uptake followed by cell flocculation using chitosan with the optimal condition in the photobioreactor was successfully achieved for 12 cycles with water from a recirculating fish tank.     

Electrolytically exfoliated graphene–polylactide‐based bioplastic with high elastic performance

This work reports an innovative way to prepare biopolymer composite by incorporating graphene (GP) synthesized from electrolytic exfoliation into biodegradable polymer blend (polylactide/epoxidized palm oil: PLA/EPO) based on melt‐blending method and studies their physical properties for food packaging and related applications. Multilayer GP structure synthesized by electrolytic exfoliation is confirmed by transmission electron microscopy and Raman spectroscopy, whereas homogeneous GP incorporation in PLA/EPO is verified by scanning electron microscopy and X‐ray diffraction. From thermogravimetric analysis and heat deformation temperature (HDT) studies, the decomposition and HDTs of PLA/EPO/GP composites are higher than those of PLA/EPO but are lower than those of pristine PLA and tend to decrease with increasing GP content because of thermal conductivity effect. From standard tensile test, loading of GP in PLA/EPO at an optimal concentration of 0.6 wt % results in higher elongation at break by as much as 52%. The observed additional elongation under a given tension and the corresponding lower tensile strength/Young's modulus may be attributed to lower binding force of materials in the composite because of the presence of relatively weak GP–PLA/EPO interfaces. Moreover, oxygen permeability is found to decrease with increasing GP contents and oxygen permeability is reduced by 40.33% at the GP loading concentration of 0.6 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41439.