The importance of nanobubbles is widely acknowledged, particularly in terms of their role with respect to bubble size and stability. Nanobubbles are tiny spherical cap-shaped bubbles, and have ...several unique physical and mechanical characteristics. Longevity, virtual disappearance of buoyancy, high internal pressure, extremely large surface/volume ratio, high oxygen dissolution rate, and generation of free radicals are the important features of nanobubbles. Their peculiar characteristics have led to many applications in the various fields of science and technology, including industrial, biological, and medical fields. This paper aims to provide a state-of-the-art for nanobubble technology. The fundamentals about existence and stability of nanobubbles are reviewed. Understanding of zeta potential values in nanobubbles is reviewed. The current methods of generation and measurement of nanobubbles are reviewed. Finally, the current applications and promising potential applications of nanobubbles are discussed, such as application of nanobubbles in flotation technology, applications of nanobubbles as cleaning agents and applications of nanobubbles in degradation of organic pollutants. In spite of its fantastic properties, use of nanobubble technology is limited to medical applications. Therefore, the recent developments in nanobubble technology are fascinating and promising but challenging as well.
Nepal, one of the least developed countries, is characterized by low per capita energy consumption and hugely dominated by traditional energy sources. Despite having enormous potential of ...hydro-electricity, only 50% of the total population has access to grid electricity. Firewood is the primary energy source for domestic purposes in rural environments. Due to geographical remoteness, a scattered consumer, higher costs of supply and maintenance, low consumption and low level of households’ income linking the rural areas to national electricity grid is difficult and implausible. In order to solve the energy problem in rural areas, Nepal’s government has initiated the production and distribution of several renewable energy technologies. Among several renewable technologies, micro-hydropower has been one of the most promising and widely adopted decentralized technologies to distribute electricity in rural areas. This article begins with a general overview of energy situation in Nepal. Present status and perspective of micro-hydro plants have also been discussed. Similarly, the dynamics of the relationship between electricity and socio-economic development has been analyzed by means of a typical rural electrification project in Tangting, Nepal by assessing the impacts of electricity on health, education, environment, and income in the village. The community has greatly benefitted from the arrival of environment friendly and affordable electricity. It has been concluded that the task of providing electricity to more remote and isolated villages is still challenging in Nepal. More systematic and comprehensive study supported by research and development is required to extend micro-hydro based electricity in more remote and poor communities of Nepal.
► This article begins with a general overview of energy situation in Nepal. ► Present status and perspective of micro-hydro plants have also been discussed. ► Micro-hydro scheme has been found one of the most successful models for the production of clean, environmental friendly and cost effective source of energy. ► Improved health, increased socio-economic condition and saved time for women are some of the major benefits to the users. ► It has been concluded that the task of providing electricity to more remote and isolated villages is still challenging in Nepal.
•Sludge pretreatment methods were compared for electricity production in MFCs.•Various types of sludge were compared for pretreatment and MFCs operation.•PS and ES were more susceptible to ultrasonic ...pretreatment than ADS.•Electricity generation was proportional to SCOD removal with all sludge types.
This study investigated the effects of different sludge pretreatment methods (ultrasonic vs. combined heat/alkali) with varied sources of municipal sewage sludge (primary sludge (PS), secondary excess sludge (ES), anaerobic digestion sludge (ADS)) on electricity generation in microbial fuel cells (MFCs). Introduction of ultrasonically pretreated sludge (PS, ES, ADS) to MFCs generated maximum power densities of 13.59, 9.78 and 12.67mW/m2 and soluble COD (SCOD) removal efficiencies of 87%, 90% and 57%, respectively. The sludge pretreated by combined heat/alkali (0.04N NaOH at 120°C for 1h) produced maximum power densities of 10.03, 5.21 and 12.53mW/m2 and SCOD removal efficiencies of 83%, 75% and 74% with PS, ES and ADS samples, respectively. Higher SCOD by sludge pretreatment enhanced performance of the MFCs and the electricity generation was linearly proportional to the SCOD removal, especially for ES.
Nitrate (NO3−-N) and nitrites (NO2−-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a ...strategy for efficiently reducing nitrates in microbial fuel cells (MFCs) powered by a granular activated carbon (GAC)-biocathode. GAC was developed by acclimatizing and enriching denitrifying bacteria under a redox potential (0.3 V) generated from MFCs. Thus, using the formed GAC-biocathode we continued to study their effect on denitrification with different cathode materials and circulation speeds in MFCs. The GAC-biocathode with its excellent capacitive property can actively reduce nitrate for over thirty days irrespective of the cathode material used. The stirring speed of GAC in the cathode showed a steady growth in potential generation from 0.25 V to 0.33 V. A rapid lag phase was observed when a new carbon cathode was used with enriched GAC. While a slow lag phase was seen when a stainless-steel cathode was replaced. These observations showed that effective storage and supply of electrons to the GAC plays a crucial role in the reduction process in MFCs. Electrochemical analysis of the GAC properties studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and zeta potential showed distinct properties with different abiotic and biocathode conditions. We found that the enrichment of electrotrophic bacteria on GAC facilitates the direct electron transfer in the cathode chamber for reducing NO3−-N in MFCs as observed by scanning electron microscopy.
Abstract
The study, conducted in western hilly areas of Nepal, inventoried and mapped over 4,222 springs from five different watersheds. The study showed that more than 50% of the spring sources were ...found under natural conditions, i.e., open spring whereas 15% of them were of pond type. Similarly, the other 15% spring was recorded as a concrete structure or tank while 1% was determined to be a well. Attempts were made to identify if a change in water discharge from springs relates to rainfall patterns. The inter-annual variability analysis shows a significant fluctuation suggesting variation in water discharge across spring sources. The lowest amount of yearly rainfall received in the river basin is governed by decreasing water flow from the springs in the upper and mid-hills of Nepal. Besides, the intra-annual variation (i.e., seasonal and concentrative nature of rainfall only during monsoon) leads to shortage of drinking water and other domestic purposes (e.g., cooking, cleaning) during the dry months of the year. This study, based on the estimation of discharge flow in these springs, revealed that about 70% were decreasing and, in particular, the flow over the recent ten years decreased significantly.
Determining the prevalence of pre-treatment HIV drug resistance (PDR) is important to assess the effectiveness of first-line therapies. To determine PDR prevalence in Papua New Guinea (PNG), we ...conducted a nationally representative survey.
We used a two-stage cluster sampling method to recruit HIV treatment initiators with and without prior exposure to antiretroviral therapies (ART) in selected clinics. Dried blood spots were collected and tested for PDR.
A total of 315 sequences were available for analysis. The overall PDR prevalence rate was 18.4% (95% CI 13.8-24.3%). The prevalence of PDR to non-nucleoside analog reverse-transcriptase inhibitors (NNRTIs) was 17.8% (95% CI 13.6-23.0%) and of PDR to nucleoside reverse transcriptase inhibitors (NRTIs) was 6.3% (95% CI 1.6-17.1%). The PDR prevalence rate among people reinitiating ART was 42.4% (95% CI 29.1-56.4%).
PNG has a high PDR prevalence rate, especially to NNRTI-based first-line therapies. Our findings suggest that removing NNRTIs as part of first-line treatment is warranted and will lead to improving viral suppression rates in PNG.
Marine biomass is considered an important feedstock for anaerobic digestion to generate energy; however, its utilization as an energy source is still minimal around the world. In the current study, ...the biochemical methane potential test was used to evaluate energy recovery from seaweed, brown algae, green algae, and fish viscera as substrates for methane production. Cumulative CH4 yields of 256 ± 28 and 179 ± 35 mL CH4/g VS were observed using green and brown algae, respectively, after 60 days of digestion. The CH4 content of the biogas was approximately 70% for both substrates. Lower CH4 yields of 127 ± 20 and 102 ± 25 mL CH4/g VS were observed using fish viscera and seaweed, respectively. Given that 44 ± 15% of the TCOD was converted to CH4, a longer adaption period or pretreatment of the marine biomass is necessary to fully convert the TCOD to CH4.
► The BMP test was used to evaluate energy recovery from marine biomass. ► Cumulative CH4 yields of 256 ± 28 mL CH4/g VS was observed using green algae. ► Using brown algae cumulative CH4 yields of 179 ± 35 mL CH4/g VS was observed. ► Lower CH4 yields of and 102 ± 25 mL CH4/g VS was observed using seaweed.
Soil erosion will have impact in the land productivity, water resource and watershed as a whole. The loss of top soil leads to land degradation and for an agrarian area like Jhimruk which also known ...as “The rice bowl of Nepal”, it would be a huge consequence on the land productivity. Therefore, it is essential to know the spatial distribution of the areas susceptible to the degradation and assess the erosion potential to plan effective mitigation measures. The Revised Universal Soil Loss Equation (RUSLE) model was used in a Geographic Information System (GIS) to estimate the soil loss of the Jhimruk watershed, Lumbini Province, Nepal. This research aimed to calculate the erosional soil loss status of the local governments lying inside the watershed. For this, remote sensing data obtained from various sources were used to generate the factor maps to calculate the soil loss through RUSLE. A 13-year mean annual precipitation data from the 8 meteorological stations in and around the watershed were used. The mean annual soil loss of the watershed was found to be 13.4 tons per hectare per year (t/ha/yr). However, the soil loss was calculated to be as high as 182 t/ha/yr. 68.82% of the total area of the watershed lie under very low erosion class and thus, have low conservation priority. On the other hand 7.73% of the total area of the watershed lie under extremely high erosion class and, thus, have a high conservation priority class. The mean erosion rate from the barren land was found to be highest (23.179 t/ha/yr) followed by agricultural (21.40 t/ha/yr) and forest area had the lowest erosion rate, i.e., 7.90 t/ha/yr.
Utilization of renewable energy technologies remains one of the major energy policies throughout the world. These technologies are proven to be successful for electrifying rural communities, ...especially in developing countries. Realizing the benefits of renewable energy sources, the Government of Nepal has initiated the production and distribution of renewable energy technologies in recent years, mainly to electrify rural communities. Although these technologies are suitable for providing electricity in isolated and remote rural areas, their implementation programs have not been successful as expected. This review provides broad-spectrum view about the energy situation in Nepal and highlights the current policies and subsidies for the optimal utilization of renewable energy resources in isolated and poor rural communities. In addition, major promotional barriers for their implementation in Nepal have been discussed.
► Nepal has enormous potential of renewable energy sources. ► Till date only small fraction of renewable energy sources has been exploited. ► However, renewable energy technologies seem to be promising options for rural electrification.
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