Biofilm Reactors: A Potential Alternative to Current Treatment Technology for Wastewater in Kathmandu Valley

Kathmandu Valley faces challenges managing its growing wastewater volume, compounded by the complex composition of unregulated industrial discharges. Releasing untreated wastewater poses a severe risk to public health and the environment. Existing wastewater treatment infrastructure, primarily reliant on conventional activated sludge processes (ASP) struggles to meet growing demands. These systems require substantial land area, are sensitive to influent variations, produce a high volume of sludge, and incur high operational and maintenance costs. Biofilms, naturally occurring assemblages of microorganisms adherent to surfaces and embedded within an extracellular polymeric matrix (EPS), present a compelling alternative for wastewater treatment due to their diverse pollutant removal capabilities. When implemented as biofilm reactors, they offer distinct advantages, including tolerance to fluctuations in wastewater composition, minimal land requirements, and reduced energy consumption. Notably, microbes residing within a biofilm are capable of biodegradation of persistent materials such as pharmaceuticals, metals, and plastics. Globally, biofilmmediated wastewater treatment has been implemented successfully, while a knowledge gap remains for the treatment of Kathmandu's wastewater.  This review critically assesses biological wastewater treatment methods, providing insight into: a) suspended growth process with their configuration, application, and limitations, b) wastewater treatment infrastructures of Kathmandu Valley, and c) biofilm process with their configuration, factors influencing biofilm development and performance, application of specific microbial strains for enhanced treatment efficiency, and factors to be considered during implementation. Furthermore, the paper recommends: a) an extensive study of laboratory-scale biofilm reactors evaluating and optimizing their performance for local integration and b) investigating the role of diverse microbial communities to further enhance the treatment plant's operation. By prioritizing research and development towards biofilm technology, Kathmandu Valley can achieve efficient and environmentally friendly wastewater management.

Water, Sanitation, and Hygiene of Nepal: Status, Challenges, and Opportunities

Access to water, sanitation, and hygiene (WASH) has been a challenge to south Asia’s rapidly growing and climate change-sensitive region. Nepal, a water-abundant country, faces obstacles to fulfilling the highly prioritized WASH Sustainable Development Goal 6 (SDG 6). This review offers details about Nepal’s WASH status from 2000 to 2020 with regard to the challenges Nepal had in delivering reliable WASH services to the people, as well as opportunities for a sustainable way forward, and provides insights that can be applied to other developing countries. From analysis of national-level assessments, estimates point toward healthy progress in extending WASH access to the population. However, large inequalities persist at the subnational level between urban and rural residents, between poor and rich residents, and between genders. Many local constraints such as a lack of long-term infrastructural capacity to provide and maintain WASH services, financial issues, and institutional and policy incompatibilities are some of the key factors that technical considerations and private sector involvement could address. We also propose roles for Nepal’s central, provincial, and local governments for identification and adaptation to the undeniable risks of climate change. Furthermore, there is a need to capitalize on the potential opportunities for developing a much-needed robust and climate-resilient WASH sector in Nepal, safeguarding the rights of future generations to safe and clean water

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.[GRAPHICS