Design and optimization of a sustainable and resilient mask supply chain during the COVID-19 pandemic: a multi-objective approach.

Wearing a mask or a face covering became mandatory in indoor public spaces to reduce the spread of coronavirus disease 2019 (COVID-19). The Ontario government (i.e., a province of Canada) encouraged medical supply producers to switch their operations to produce personal protective equipment (e.g., masks) during the COVID-19 pandemic. In this regard, there are several uncertain parameters (e.g., operational costs, market demand, and capacity levels of facilities) affecting the performance of producers in a medical supplies market. In this study, we propose a flexible optimization model to configure a robust mask supply chain network under uncertainty. Furthermore, companies are supposed to undertake their operations based on sustainable manners, in compliance with provincial policy, in Ontario. Therefore, the proposed flexible optimization model is extended to a robust multi-objective model to investigate sustainable strategies in a mask supply chain network design problem. The applicability of this model is demonstrated for the Greater Toronto Area, Canada.

On-site treatment of flowback and produced water from shale gas hydraulic fracturing: A review and economic evaluation.

On-site flowback treatment systems are typically rated and selected based on three fundamental categories: satisfying customer needs (e.g. meeting effluent quality, capacity, delivery time and time required to reach stable and steady effluent quality), common features comparison (e.g. treatment costs, stability of operation, scalability, logistics, and maintenance frequency) and through substantial product differentiation such as better service condition, overcoming current market limitations (e.g. fouling, salinity limit), and having lower environmental footprints and emissions. For treatment of flowback, multiple on-site treatment systems are available for primary separation (i.e. reducing TSS concentrations and particle size below 25 µm for disposal), secondary separation (i.e. removing TSS, iron and main scaling ions, and reducing particle size up to 5 µm for reuse), or tertiary treatment (i.e. reducing TDS concentration in the permeate/distillate to below 500 mg/L) for recycling or discharge. Depending on geographic features, frac-fluid characteristics, and regulatory aspects, operators may choose disposal or reuse of flowback water. Among these approaches, desalination is the least utilized option while in the majority of cases on-site basic separation is selected which can result in savings up to $306,800 per well. Compared to desalination systems, basic separation systems (e.g. electrocoagulation, dissolved air floatation) have higher treatment capacity (159-4133 m3/d) and specific water treatment production per occupied space (8.9-58.8 m3/m2), lower treatment costs ($2.90 to $13.30 per m3) and energy demand, and finally generate less waste owing to their high recovery of 98-99.5%, which reduces both operator costs and environmental burdens.