Biosensing Near the Exceptional Point Based on Resonant Optical Tunneling Effect

Inspired by exceptional point (EP) sensing in non-Hermitian systems, in this work, a label-free biosensor for detecting low-concentration analytes is proposed, via a special multilayer structure: a resonant optical tunneling resonator. Due to the square root topology near the exceptional point, a recognized target analyte perturbs the system deviated from the exceptional point, leading to resolvable modes splitting in the transmission spectrum. The performance of the designed sensor is analyzed by the coupled-mode theory and transfer matrix method, separately. Here, the simulation results demonstrate that the obtained sensitivity is 17,120 nm/imaginary part unit of refractive index (IP) and the theoretical detection limit is 4.2 × 10−8 IP (regarding carcinoembryonic antigen (CEA), the minimum detection value is 1.78 ng). Instead of the typical diffusion manner, the liquid sample is loaded by convection, which can considerably improve the efficiency of sample capture and shorten the response time of the sensor. The sketched sensor may find potential application in the fields of biomedical detection, environment protection, and drinking water safety.

Role of Sanitary Engineers in Prevention of Covid-19 Pandemic

Among the most emphasized consequences of pandemic COVID-19 influence is a negative trend of economic development and lock down of many production companies. One of areas where sanitary engineers can be engaged is drinking water safety and safety of wastewater. The new situation requires the change of actual teaching content during the teaching process of sanitary engineers, with the purpose of their training for inclusion in activities on prevention of virus spreading and controlling subjects in charge of people health protection, food safety and protection of living environment. It is very important that higher school institution authorities become familiar with knowledge gaps, potential implications on food, water and environment safety, research direction and other issues related to virus control, among which is also SARS–COV-2. The aim of this work is to encourage wider discussion on promotion of the actual study programs on higher institutions in Bosnia and Herzegovina and neighbouring countries as well as development of content proposals, which can lead to knowledge promotion, and competence of graduated students. During the recent discussion, we came to conclusion that it is necessary to develop studies, which have multidisciplinary approach, including the area of public health system, quality, food safety, environment protection and administrative law. Apart from that, students should obtain the necessary knowledge level in area of organization, management and economy, and with the purpose of enabling continuous production and income creation. We should also develop student research capabilities.

One-step removal of lead from water using an electricity-free and sustainable membrane filtration

Lead (Pb) is a typical contaminant in water with adverse effects on human health. Hong Kong’s incident of drinking water contamination by Pb in 2015 caused severe public concerns regarding drinking water safety. Conventional treatment methods for Pb removal generally require electricity, chemical dosage, and considerable time and space, which significantly restrict their use for rapid water purification under emergency situations. In this study, a polyvinyl alcohol/polyacrylic acid (PVA/PAA) composite nanofibrous membrane was developed for the rapid and effective removal of Pb from water. The PVA/PAA membrane had a high water permeability of 550 L/m2/h/kPa - 710 L/m2/h/kPa, which allowed the filtration to be driven by gravity (e.g. with a water height of 10.0 cm). The membrane showed consistently high removal efficiency of Pb (> 95%) with a volumetric loading up to 3000 L/m2. This high removal efficiency was attributed to the combined effects of complexing and electrostatic attraction between Pb and PAA. An esculent citric acid was used to regenerate the exhausted PVA/PAA membrane. The regenerated membrane maintained its removal efficiency of Pb over a five-cycle filtration. These results imply that the PVA/PAA composite membrane can be repeatedly used in electricity-free filtration devices for rapid elimination of Pb under emergency situations.

Specifically Designed Magnetic Biochar From Waste Wood for Arsenic Removal

Arsenic is a kind of metal elements, widely distributed in nature. Many technologies, including adsorption, ion exchange, membrane separation and extraction, have been developed to treat arsenic-containing wastewater due to a series of drinking water safety problems caused by arsenic pollution. Biochar has some advantages of big surface area, low cost and so on. Therefore, waste wood was used as biochar, FeCl3·6H2O and KMnO4 were also used to promote the performance of arsenic removal. The results of XRD, BET, EA and VSM analysis show that modified biochar has major elements of Fe, Mn with KMnO4. The modified biochar (Fe1Mn1C1) has higher magnetism of 40 emu g-1. Through adsorption performance assessment, the best ratio of Fe/C is 1:1 and the adsorption efficiency and capacity of Fe1C1 is 61.6% and 0.681 mg g-1, respectively. Then, the best ratio of Mn, Fe and C is 4:1:1 with highest adsorption efficiency of 80.8% and capacity of 0.724 mg g-1. The best dosage of Fe1C1 and Fe1Mn2C1 is the same as 1 g L-1. It shows better adsorption capacity under higher pH with pristine biochar (PB) and Fe1C1 while under lower pH with Fe1Mn2C1. The adsorption patterns of PB and Fe1Mn2C1 fit Langmuir well. In contrast, adsorption pattern of Fe1C1 fits Freundlich well. In addition, three types of biochars all fit the pseudo second order adsorption kinetics.

The Ecology and Evolution of Amoeba-Bacterium Interactions

ABSTRACT Amoebae are protists that have complicated relationships with bacteria, covering the whole spectrum of symbiosis. Amoeba-bacterium interactions contribute to the study of predation, symbiosis, pathogenesis, and human health. Given the complexity of their relationships, it is necessary to understand the ecology and evolution of their interactions. In this paper, we provide an updated review of the current understanding of amoeba-bacterium interactions. We start by discussing the diversity of amoebae and their bacterial partners. We also define three types of ecological interactions between amoebae and bacteria and discuss their different outcomes. Finally, we focus on the implications of amoeba-bacterium interactions on human health, horizontal gene transfer, drinking water safety, and the evolution of symbiosis. In conclusion, amoeba-bacterium interactions are excellent model systems to investigate a wide range of scientific questions. Future studies should utilize advanced techniques to address research gaps, such as detecting hidden diversity, lack of amoeba genomes, and the impacts of amoeba predation on the microbiome.

Modification of the H2S test to screen for the detection of sulphur- and sulphate-reducing bacteria of faecal origin in water

The H2S test was created to assess the microbial quality of drinking water in low-resource settings, but the original version of the H2S test lacks sensitivity and specificity for faecal indicator bacteria. There is evidence that a modified media formula of the H2S test may be more sensitive and specific for the faecal indicator bacterium Escherichia coli (E. coli) and less sensitive to organisms of non-faecal origin. This research established the detection threshold and operational range of the H2S test, to increase its sensitivity and specificity for E. coli. A total of 20 modifications of the H2S test, and the original test, were assayed against 20 confirmed and pure culture bacteria of faecal and non-faecal origin at varying concentrations. Additionally, some of the H2S test modifications were evaluated against standard methods for drinking-water analysis. Results indicate that using a modified version of the H2S test containing L-cystine and 2-mercaptopyridine, and bile salts or penicillin G, E. coli will produce H2S. In addition, this research reveals which organisms react positively to the original and modified versions of the H2S test. The modified versions of the H2S test can be promoted as a simple screening test for microbial drinking-water safety in low-resource settings.

The effectiveness of household water treatment and safe storage in improving drinking water quality: a disinfection by-product (DBP) perspective

Serving as the last barrier to secure drinking water safety, household water treatment and safe storage (HWTS) is perceived as an interim measure for removing pathogens from drinking water and reducing disease risk. In recent years, the application of HWTS has shown a growing trend, and its performance in controlling chemicals has also received much attention. Disinfection by-products (DBPs) are formed by the reaction of chemical disinfectants and precursors, and are present at sub-μg·L−1 or low-to-mid-μg·L−1 levels in drinking water. Although precursor control and disinfection operation modification could contribute to DBP mitigation to some degree, DBP removal after their formation emerges as an important strategy due to the ubiquitous existence of DBPs in distribution systems and tap water. In order to figure out how DBP concentrations vary during the residence time of drinking water in households, this review summarizes the effectiveness and mechanism of HWTS and combination technologies for DBP control in municipal tap water, and makes a comparison with regard to technologies implementing different removal mechanisms as well as DBPs possessing different natures. Based on these results, this article provides an insight into DBP risk assessment and human health protection.

Simulation of nitrogen and phosphorus pollution in typical agricultural and forested basins as well as relevant reduction effect based on SWAT model

Non-point source nitrogen and phosphorus pollution is a critical threat to aquatic ecosystems and a potential risk to drinking water safety. To precisely control nitrogen and phosphorus pollution in the river basin, in this study, we identified key pollution areas of the river basin, analyzed the main characteristics of pollution sources as well as their contribution to the river basin pollution, and conducted simulation analysis on reduction measures based on the SWAT model. The results showed that: (1) The simulation effect of the calibrated model was good, and sub-basins 3, 39 and 96 were the key source areas, the main sources of pollution were combined pollution from livestock and poultry breeding and planting industry; (2) crops had the largest input and output for both nitrogen and phosphorus, the output of which was 6,137.8 t/a and 562.4 t/a respectively. The urban point sources had the highest output rates of nitrogen and phosphorus, 75.7% and 67.5% respectively; (3) with the optimal combination of reduction measures, nitrogen and phosphorus were reduced by 1,438.9 t and 85.3 t respectively, i.e., the reduction rates were the highest. The reduction effect for total nitrogen was better than that for total phosphorus.