Performance evaluation of species varied fixed bed biofilm reactor for wastewater treatment of Dhobi Khola outfall, Setopul, Kathmandu, Nepal.

The sustainability of wastewater treatment plants poses significant challenges for developing countries, necessitating substantial investment for operation and maintenance. Biofilm reactors seeded with specific species of microorganisms were investigated under controlled environmental conditions. However, the performance evaluation of such reactors under natural conditions remains largely underexplored. This study investigated wastewater treatment capabilities of bench-scale fixed bed biofilm reactors, employing various species (Wastewater Microbes, Pseudomonas, Algae, and a co-culture of Algae and Pseudomonas). The reactors (Treatments and Control) were filled with 28 mm nominal-size local aggregates as packing media, operated under different contact times, and subjected to varying concentrations of heavy metals (Zn, Cd). To assess the reactor performances, the Bland-Altman Plot and Chemical Oxygen Demand (COD) removal kinetics were evaluated. The results revealed that the reactor initiated with a co-culture exhibited the optimal COD removal efficiency, reaching 84 ± 1 %. The reactor initially seeded with wastewater microbes exhibited the highest heavy metal elimination, achieving 94 ± 1 % and 88 ± 1 % removal for Zn and Cd respectively. The wastewater-seeded reactor demonstrated the zero-order COD removal kinetic coefficient (k) of 46.41 mg/L/h at an average influent COD concentration of 558 mg/L at 10 h contact time. While Pseudomonas-seeded reactor demonstrated k = 0.73 mg/L/h at 20 h contact time with 69 mg/L influent COD and heavy metal concentrations Zn = 26 mg/L and Cd = 3.57 mg/L. The findings of this study suggest that variations in environmental conditions, contact time, and heavy metal concentration have minimal impact on the pollutant removal efficacy of the reactors, and provide robust evidence for their viability as a sustainable alternative in municipal wastewater treatment. The study also identifies the possibility of treating specific wastewater characteristics by altering the dominant species in the reactors, paving the way for further research on the efficacy of other microbial genomes in fixed bed biofilm reactors.

The bioherbicidal potential of isolated fungi cultivated in microalgal biomass.

This study evaluated the bioherbicidal potential of wild fungi grown on microalgal biomass from the digestate treatment of biogas production. Four fungal isolates were used and the extracts were evaluated for the activity of different enzymes and characterized by gas chromatography coupled with mass spectrometry. The bioherbicidal activity was assessed by application on Cucumis sativus, and the leaf damage was visually estimated. The microorganisms showed potential as agents producing an enzyme pool. The obtained fungal extracts presented different organic compounds, most acids, and when applied to Cucumis sativus, showed high levels of leaf damage (80-100 ± 3.00%, deviation relative to the observed average damage). Therefore, the microbial strains are potential biological control agents of weeds, which, together with the microalgae biomass, offer the appropriate conditions to obtain an enzyme pool of biotechnological relevance and with favorable characteristics to be explored as bioherbicides, addressing aspects within the environmental sustainability.

Characterisation of bushfire residuals in source water and removal by coagulation.

A bushfire is a spontaneous vegetation fire that can fundamentally affect lives, property, the environment, and even the global climate. Ash from fire carries hazardous pollutants like metal oxides/hydroxides, minerals, black carbons, and by-products of partial combustion, such as hydrocarbons and colloidal charcoal. Bushfire gases and residues can heavily pollute surface and groundwater resources. This paper focuses on the impact of bushfire residue on water quality and explores methods to remediate impacted water supplies. Soils burned in controlled furnace conditions between 150 °C, and 600 °C were characterised, suspended in water, and changes in water quality was measured following leaching from the burned residues. Results indicate that once the soil is burned at temperatures above 300 °C, there is little evidence of leached organic matter. At temperatures below 300 °C, the water discolouration was evident after 24 h leaching, and much higher quantities of leached organic matter were measured. Higher burning temperatures resulted in more alkaline residues. Leachate and charred sample characterisation data shows that the charcoal is highly porous and mainly consists of- amorphous material. The ash is a heterogeneous concoction of smaller particles and comprises significant mineral content. The results also indicate that the primary pollutant among the brushfire residuals is ash which increases pH, alkalinity, turbidity, and UV254. Coagulation experiments reveal that dual coagulation systems with metal salts- organic polyelectrolyte reduced the turbidity by 84 %, and dissolved organic carbon (DOC) reduced by 68 % of water containing ash residues. However, some other treatments are needed to reduce the alkalinity.

Applications of smart grid technology in Nepal: status, challenges, and opportunities.

Energy transformation and sustainability have become a challenge, especially for developing countries, which face broad energy-related issues such as a wide demand-supply gap, extensive fossil fuel dependency, and low accessibility to clean energy. Globally, smart grid technology has been identified to address these affairs and enable a smooth transition from traditional to smart energy systems, ensuring energy security. This paper studies the critical role in strengthening the power system, integrating renewable sources, electrifying the transport sector, and harnessing bioenergy. Evaluating the current energy scenario in Nepal, this article presents the smart grid as a solution to existing and future energy issues and the associated challenges during its implementation, urging concerned authorities to launch initiatives to promote it. Moreover, this study also lays the foundation for future research into the smart grid's potential to reform the power sector in other developing nations with abundant renewable energy sources and similar energy-related barriers.

Spatial and temporal distribution of arsenic contamination in groundwater of Nawalparasi-West, Nepal: an investigation with suggested countermeasures for South Asian Region.

Nawalparasi-West/Parasi is one of the severely affected districts in the Terai lowlands of Nepal by arsenic (As) contamination in groundwater, exceeding standards of 10 ppb (WHO) and 50 ppb (Nepal Drinking Water Standard). This study presents the spatial and temporal distribution of As across 6 km × 10 km region in Parasi via meteorological, hydrogeological, physio-chemical, and sedimentological investigations in 31 communities for about 5 years. In this study, water balance analysis was carried out for understanding the groundwater dynamics in the study area and its contribution to As elution. Gentle flow gradient and little to no infiltration was observed in the central region with relatively impervious silty clayey flood plain, where higher As concentrations were obtained compared to the northern Siwalik foothills and southern parts with coarser sediments. Similarly, higher As concentration (1048 ppb) was recorded in the drier pre-monsoon season than the wet season (529 ppb). The aquifer at 12 to 23 m depth feeding 73% wells in the study area exhibited higher As concentration in reduced environment as opposed to the oxidizing state at 5- to 6-m and 30- to 50-m deep aquifers. Other constituents such as Fe, B, and Cr and their relation with As were analyzed. The results of GERAS model analysis done for health risk assessment are also presented which show that under long-term exposure, the residents in Parasi were undertaking intolerable cancer risk of 1.1 to 6.4 × 10-3. This study further incorporates socio-economic sentiments vital to analyze, and propose sustainable and cheap countermeasures for immediate implementation to reduce As exposure and health risk in Nepal, which is also highly applicable for other affected regions in South Asian Region.

Potential application of enhanced phytoremediation for heavy metals treatment in Nepal.

Heavy metals contamination in soil and water resources is a great threat to developing countries because of the lack of waste treatment facilities. A majority of wastewater treatment methods are known to be expensive and out of reach for municipalities and small pollution treatment enterprises. Phytotechnology is a promising, sustainable, environment-friendly, and cost-effective technique for domestic and industrial wastewater treatment in places where land is available. However, interest in conventional remediation methods and the lack of information on recent advances in a significant portion of the society in developing countries have restrained the applications of phytoremediation. This review discusses the concept of phytoremediation, mechanisms of heavy metals removal by plants, and the potential application of enhanced phytoremediation technologies in developing countries like Nepal. The authors also review the commercially viable hyperaccumulator species with their native distribution, heavy metals intake capacity, and their availability in Nepal. Those native plants can be utilized locally or introduced strategically in other parts/countries as well. Thus, for a flora-rich country like Nepal, this study holds great potential and presents enhanced phytoremediation as an effective and sustainable strategy for the future.

Estimation of greenhouse gases emission from domestic wastewater in Nepal: A scenario-based analysis applicable for developing countries.

Domestic wastewater and wastewater treatment plants (WWTPs) are key emitters of greenhouse gases (GHGs). Quantifying these emissions in the present and future is crucial to tackle global climate change issues. As a developing country with few rural and urban wastewater treatment facilities, Nepal may have a unique opportunity to reduce future GHGs emissions by a proper selection of wastewater treatment technology. In this paper, the authors used Python programming to estimate the GHGs emissions from the domestic wastewater sector in Nepal under various technological development scenarios for 2020 to 2040 using the refined 2019 estimation methodology developed by Inter-governmental Panel on Climate Change (IPCC). Results show total equivalent CO2 emission of 3829.43 and 4523.65 Gigagrams in 2020 and 2040, respectively. The 2020 value is seven times greater than Nepal's 2017 national estimates because this study considered rural population and updated methodology. Comparing the technology development scenarios with the Business as Usual scenario, the highest GHGs reduction could be achieved by hybrid constructed wetlands (69.20%) followed by a combined anaerobic and aerobic system with biogas recovery for energy generation (61.72%). Further accuracy may be attained only through the actual measurement of WWTPs emissions and country-specific emission factors. Thus, this paper proposes GHGs estimation of future scenarios portraying urban and rural populations may be invaluable to policymakers of GHGs mitigation for selection of feasible WWTPs, especially in developing countries with limited wastewater treatment facilities and wastewater activity data.

Pretreatment of agricultural biomass for anaerobic digestion: Current state and challenges.

The anaerobic digestion (AD) of agricultural biomass is an attractive second generation biofuel with potential environmental and economic benefits. Most agricultural biomass contains lignocellulose which requires pretreatment prior to AD. For optimization, the pretreatment methods need to be specific to the characteristics of the biomass feedstock. In this review, cereal residue, fruit and vegetable wastes, grasses and animal manure were selected as the agricultural biomass candidates, and the fundamentals and current state of various pretreatment methods used for AD of these feedstocks were investigated. Several nonconventional methods (electrical, ionic liquid-based chemicals, ruminant biological pretreatment) offer potential as targeted pretreatments of lignocellulosic biomass, but each comes with its own challenges. Pursuing an energy-intensive route, a combined bioethanol-biogas production could be a promising a second biofuel refinery option, further emphasizing the importance of pretreatment when lignocellulosic feedstock is used.

Effects of temperature on nitrous oxide (N2O) emission from intensive aquaculture system.

This study examines the effects of temperature on nitrous oxide (N2O) emissions in a bench-scale intensive aquaculture system rearing Koi fish. The water temperature varied from 15 to 24 °C at interval of 3 °C. Both volumetric and specific rate for nitrification and denitrification declined as the temperature decreased. The concentrations of ammonia and nitrite, however, were lower than the inhibitory level for Koi fish regardless of temperature. The effects of temperature on N2O emissions were significant, with the emission rate and emission factor increasing from 1.11 to 1.82 mg N2O-N/d and 0.49 to 0.94 mg N2O-N/kg fish as the temperature decreased from 24 to 15 °C. A global map of N2O emission from aquaculture was established by using the N2O emission factor depending on temperature. This study demonstrates that N2O emission from aquaculture is strongly dependent on regional water temperatures as well as on fish production.