Hydraulic Retention Time (HRT) and Solid Retention Time (SRT) are two major parameters for the performance of the activated sludge process. The present study was aimed at studying the performance of the activated sludge process with varying SRT and HRT using a laboratory-scale plant. The wastewater was synthesized at the laboratory. HRT of 1, 2, 4, 8 and 12 hours were used and SRT of 5 days, 7.5 days and 10 days were used for the study. The performance was found to increase with increasing HRT and SRT. An Analysis of Variance (ANOVA) test was used to confirm the variation. For SRT of 5 days, the performance for Chemical Oxygen Demand (COD) removal increased from 12.9% to 88.4% for an increase in HRT from 1 hr. to 12 hrs. Similarly, for Total Kjeldahl Nitrogen (TKN), the removal increased from 10.8% to 72.1%. Likewise, the performance for COD removal increased from 12.5% to 90.9%, whereas the removal of TKN increased from 10.1% to 85.2% for SRT of 7.5 days. The COD removal increased from 13.8% to 93.4% and TKN removal increased from 9.6% to 90.2% for SRT of 10 days.
In Nepal, both horizontal bed and vertical bed subsurface flow constructed wetlands have been used for wastewater treatment. However, these units were designed based on the empirical findings from other countries. The rational design criteria developed so far has some limitations as the performance of the units is sensitive to the behaviour of the microorganisms, climatic conditions and other attributes pertaining to the local contexts. Secondly, only limited numbers of studies have been carried out to assess the performance of these systems leading to the development of rationale design criteria. Considering these facts, the major objectives of the study were set to: (1) evaluate the performance of the subsurface flow reed bed system in terms of organic matter and ammonia removal; (2) estimate the reaction rate constant and effective specific surface area; (3) assess the relationship between performance and age of the system; and (4) investigate the dynamic behaviour of the reaction rate constant. The study was carried on three full-scale domestic wastewater treatment units and one pilot-scale ranging the age of horizontal beds from 1 to 5 years.
Municipal solid waste management (MSWM) is an engineered and environment-friendly manner which is yet to be achieved in Nepal. Increasing waste generation due to surging urbanization is threatening the environmental sanitation as well as human health. In this context, the exploration of suitable alternative waste treatment methods should be done and practiced soon. This paper was envisioned to explore the recovery potential and feasibility of composting and recycling in 8 Nepalese municipalities. The total recovery value from municipal solid waste (MSW) was NPR 43.14 Lakhs ($35,544) per day. With the amalgamation of composting and recycling, reduction of around 199,000 m3of landfills, 4,800 m3 of leachate generation, and 81,000 (CO2 e) of GHG emissions and saving of above 424,000 trees could be achieved per year. The analysis of the results indicates the realistic explanation of underlying reasons for integrating composting and recycling in MSWM system in all the municipalities. It is anticipated that this paper will serve as a key reference document for making decisions regarding investment in composting and recycling.
The Poverty Alleviation Fund Project will improve the livelihoods of the rural poor, and socially excluded groups in Nepal, by implementing income generation activities, small-scale infrastructure development programs, and sustaining these programs in rural communities, through training, and capacity building. Nevertheless, it is foreseen that some small-scale infrastructure subprojects, may potentially foster adverse environmental impacts, such as due to water supply and sanitation and irrigation subprojects, deforestation practices, as well as because of improper use of pesticides on agricultural lands. Mitigation measures recommend the following. The use of appropriate bioengineering measures, and appropriate management of excavated soil during water supply pipelines installation should be practiced to prevent soil erosion and landslides; training and capacity building shall be provided on water resources handling to prevent water contamination, and on ways to prevent water borne diseases; similarly, monitoring and periodic cleaning should be conducted as part of operational and maintenance activities to minimize biological water pollution; construction of irrigation subprojects should avoid unstable land areas, encouraging the use of bioengineering techniques to avoid soil erosion, while vegetation, and crop land areas should be avoided as possible, or later on, re-vegetative practices should be implemented; irrigation canals should be relocated so as to minimize adverse impacts on forests, wild habitats, and biodiversity, supported by the appropriate training; adequate drainage systems should be in place to prevent water logging, and, indigenous and traditional methods of water distribution should avoid conflicts on water distribution; market access should be ensured concerning agricultural products to enhance the local economy, strengthened by capacity building, and an agricultural base training.
The present study aimed at determining performance and pollutant removal kinetics in the treatment of wastewater using a laboratory-scale continuous flow stirred tank reactor (CFSTR) based on activated sludge process (ASP). The waste activated sludge from the Guheshwori Wastewater Treatment Plant (WWTP) is used as a start-up seed sludge. The CFSTR is operated at varying solid retention time (SRT) of 1, 2, 3, 5, 7.5 and 10 days using synthetic wastewater prepared daily as an influent. Chemical Oxygen Demand (COD) and Total Kjeldahl Nitrogen (TKN) of the influent, effluent and Mixed Liquor Volatile Suspended Solids (MLVSS) of aeration tank are analyzed at various SRT to determine the respective kinetic coefficients. The COD and TKN removal increased with increasing SRT. The kinetic coefficients; maximum substrate utilization rate (k), the half velocity constant (Ks), cell yield coefficient (Y ) and decay coefficient (kd) have been found to be 1.61 g COD/g VSS · day, 87.22 mg/L, 0.50 g Volatile Suspended Solid (VSS)/g COD and 0.07 day-1 respectively for synthetic wastewater. Similarly, k, Ks, Y and kd for the treatment of wastewater from Guheswori WWTP have been observed to be 1.86 g COD/g VSS.day, 107.77 mg/L, 0.32 g VSS/g COD and 0.04 day-1.
Abstract The COVID‐19 pandemic has impacted social, economic, and environmental systems worldwide, slowing down and reversing the progress made in achieving the Sustainable Development Goals (SDGs). SDGs belong to the 2030 Agenda to transform our world by tackling humankind's challenges to ensure well‐being, economic prosperity, and environmental protection. We explore the potential impacts of the pandemic on SDGs for Nepal. We followed a knowledge co‐creation process with experts from various professional backgrounds, involving five steps: online survey, online workshop, assessment of expert's opinions, review and validation, and revision and synthesis. The pandemic has negatively impacted most SDGs in the short term. Particularly, the targets of SDG 1, 4, 5, 8, 9, 10, 11, and 13 have and will continue to have weakly to moderately restricting impacts. However, a few targets of SDG 2, 3, 6, and 11 could also have weakly promoting impacts. The negative impacts have resulted from impeding factors linked to the pandemic. Many of the negative impacts may subside in the medium and long terms. The key five impeding factors are lockdowns, underemployment and unemployment, closure of institutions and facilities, diluted focus and funds for non‐COVID‐19‐related issues, and anticipated reduction in support from development partners. The pandemic has also opened a window of opportunity for sustainable transformation, which is short‐lived and narrow. These opportunities are lessons learned for planning and action, socio‐economic recovery plan, use of information and communication technologies and the digital economy, reverse migration and “brain gain,” and local governments' exercising authorities.
The study is focused on the life cycle assessment of municipal solid waste management of Kathmandu city. Total waste generated in a year was taken as a functional unit (FU) in the study to compare three different scenarios: 1.) Business as usual (BAU) consisting of collection, transport, and landfilling; 2.) Energy recovery along with recycling; and 3.) Conjunctive disposal system comprising of composting and landfilling. The primary and secondary data were collected from Environment Department and Solid Waste Management Section of Kathmandu city and Solid Waste Management Technical Support Center of Government of Nepal. The life cycle inventory was developed with detail unit process by quantifying values of various resources and emissions. Life cycle impact assessment was performed to compute impacts on the environment. The contribution of this process to the environment was calculated as global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), and fuel energy consumption (FEC).The results obtained from the quantification of environmental impacts were compared. It was found that the Scenario 3 is more eco-friendly than Scenario 1 and Scenario 2. The findings were fundamentally based on the environmental burden of waste managed in landfill regardless of recycling and composting. At the end, GWP, AP, EP, and FEC were calculated for each scenario and compared in kg equivalents per metric ton of waste managed in landfill (Table 1). The comparative study of environmental impacts was performed and we calculated GWP, AP and EP for the total waste managed in a year. Table 1 also includes emission for annual waste management. The results obtained warrant a need for sustainable waste management methods for Kathmandu considering the conjunctive disposal system with composting and landfilling that reduces all four environmental impacts excluding the inefficient collection system, low public participation, landfill location, and operational improvements.As indicated above, Scenario 3 was found to be an option with minimum environmental impacts (less GWP, AP, and EP) and cheaper fuel cost. At the same time, the results are influenced by higher composition of organic waste that can be composted and the GWP, which can be controlled. The results of this study can be applied for an integrated solid waste management system as an environmental tool.
The COVID-19 pandemic has affected humankind worldwide, slowing down and even reversing the progress made in achieving Sustainable Development Goals (SDGs). It has negatively impacted most SDGs but with positive impacts on a few. We discuss some initial impacts observed and explores potential impacts on the achievement of SDGs for Nepal. The study followed a knowledge co-creation process with experts from various professional backgrounds, involving five steps: online survey, online workshop, assessment of expert's opinions, review and validation, and revision and synthesis. The pandemic has restricting impacts on the progress of most SDGs. However, it has also opened a window of opportunity for sustainable transformation. Many of the negative impacts may subside in the medium and long terms. The negative impacts on SDGs resulted from factors linked to the pandemic or the measures taken to control it. The key five impending factors are lockdowns, underemployment and unemployment, closure of institutions and facilities, diluted focus and funds for non-COVID-19 issues, and anticipated reduced support from development partners. The generated transformative opportunities are lessons learned for planning and actions, socio-economic recovery plan, use of information and communication technologies and impetus to the digital economy, reverse migration and 'brain gain,' and local governments' exercising authorities. For sustainable transformation, the window to grasp these opportunities is short-lived and will get narrow over time, i.e., before rebounds occur following the past trajectories.
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