The coronavirus disease 2019 pandemic has posed severe threats to humans and the geoenvironment. The findings of severe acute respiratory syndrome coronavirus 2 (Sars-CoV-2) traces in waste water and the practice of disinfecting outdoor spaces in several cities in the world, which can result into the entry of disinfectants and their by-products into storm drainage systems and their subsequent discharge into rivers and coastal waters, raise the issue of environmental, ecological and public health effects. The aims of the current paper are to investigate the potential of water and waste water to operate as transmission routes for Sars-CoV-2 and the risks of this to public health and the geoenvironment. Additionally, several developing countries are characterised by low water-related disaster resilience and low household water security, with measures for protection of water resources and technologies for clean water and sanitation being substandard or not in place. To mitigate the impact of the pandemic in such cases, practical recommendations are provided herein. The paper calls for the enhancement of research into the migration mechanisms of viruses in various media, as well as in the formation of trihalomethanes and other disinfectant by-products in the geoenvironment, in order to develop robust solutions to combat the effects of the current and future pandemics.

No abstract

For a long time in the practice of geotechnical engineering, soil has been viewed as an inert material, comprising only inorganic phases. However, microorganisms including bacteria, archaea and eukaryotes are ubiquitous in soil and have the capacity and capability to alter bio‐geochemical processes in the local soil environment. The cumulative changes could consequently modify the physical, mechanical, conductive and chemical properties of the bulk soil matrix. In recent years, the topic of bio‐mediated geotechnics has gained momentum in the scientific literature. It involves the manipulation of various bio‐geochemical soil processes to improve soil engineering performance. In particular, the process of microbial‐induced calcium carbonate precipitation (MICP) has received the most attention for its superior performance for soil improvement. The present work aims to shape a comprehensive understanding of recent developments in bio‐mediated geotechnics, with a focus on MICP. Referring to around one hundred studies published over the past five years, this review focuses on popular and alternative MICP processes, innovative raw materials and additives for MICP, emerging tools and testing methodologies for characterizing MICP at multi‐scale, and applications in emerging and/or unconventional geotechnical fields.

Microbially Induced Calcite Precipitation (MICP) is a sustainable method of stabilizing (i.e., 2 cementing) loose sandy deposits and/or to create an impervious barrier within the soil mass. 3 MICP can occur through various biochemical pathways, among which 'Urea Hydrolysis (UH)' is considered to be the most efficient method of biochemically inducing calcite 5 precipitation. To date, the geotechnical engineering community investigating MICP has 6 tended to focus on the hydro-mechanical behaviour of the end product, i.e. MICP cemented 7 sands; however, many biochemical factors that affect reaction-rate kinetics and MICP 8 outcome have been understudied or neglected. This study investigated the kinetics of UH and 9 compared different sources of urease enzyme: those microbially cultivated in the laboratory 10 (i.e., Sporosarcina pasteurii) and those extracted from plants (i.e., Jack bean meal), to 11 investigate the influence of urea concentration, buffer capacity, and cell harvesting method on 12 UH. Through this study, an attempt has been made to arrive at an optimal concentration of 13 urea, under the influence of the above mentioned parameters along with the buffering action 14 of the soil, on urea hydrolysis. These results have implications towards optimising MICP and, 15 in particular, for upscaling these methods to in-situ applications.

No abstract