Surface water pollution is one of the serious environmental problems in urban centers in Nepal due to the discharge of untreated wastewater into the river-system turning them into open sewers. Wastewater treatment plants are almost non-existing in the country except for a few in the Kathmandu Valley and even these are not functioning well. A new approach called Constructed Wetland System for treatment of wastewater has been introduced in Nepal. ENPHO was the pioneering organization to introduce Constructed Wetland (CW) in Nepal in 1997. Starting with the first CW in Dhulikhel Hospital, it achieved popularity within a short time of its operations. CW is simple, locally manageable, cost effective and excellent performance in removal of pollutants. In our country where all wastewater is draining into the surface water bodies without any treatment, new hope brings for clean future. Now, there are 11 sub-surface flow constructed wetland systems in operation for treatment of greywater, wastewater and fecal sludge at household to institutional scale. The scale of treatment systems is from single household to institutions with more than 300 inhabitants. In addition, a large-scale CW system for treatment of 75 m3 of fecal sludge and 40 m3 of leachate has recently been completed for Pokhara Sub-metropolitan City. Despite of non-existence of effluent quality criteria for municipal or domestic wastewater, many institutions and small municipalities are now taking keen interest to install CW at their premises and several communities are now in designing stage. Recently, government has decided to install CW system at eight small cities for the treatment of municipal wastewater under Urban Environment Improvement Program funded by Asian Development Bank.

ENPHO is providing technical services for designing and construction supervision of the system. It is also carrying out research on its performance evaluation. Many national and international scholars are carrying out research on the existing operational CWs that is helping to improve future design criteria in the context of Nepal. On the basis of past six-year experience on CW, ENPHO found high pollutant removal efficiency as more than 95 percent of major pollutants such as suspended solids, organic pollutants, and ammonia-nitrogen. Similarly, removal of E. coli is also achieved by 99 %. At three sites, the treated wastewater is being reused for toilet flushing, irrigation and cleaning vehicles. Similarly the construction of fecal sludge and leachate treatment system through CW at Pokhara Sub-Metropolitan City would probably be the largest constructed wetland system for treatment in Asia. There are still lots of challenges to be faced for the successful implementation of this technology in Nepal as well as other countries for water conservation and protection of water bodies in a sustainable manner.

• Constructed Wetland System for treatment of wastewater of Kapan Monastery, Kathmandu
• Constructed Wetland System to treat septage and landfill leachate for Pokhara sub-metropolis for EAST Consult/ENPHO
• Conducted feasibility study for design of a constructed wetland system for Tansen Municipality
• Conducted feasibility study for design of a constructed wetland system for Madhyapur Thimi Municipality
• Construction of Constructed Wetland for treatment of wastewater for Sushma Koirala Memorial Hospital, Sankhu.
• Designed Constructed Wetland System for Middle Marsyangdi Hydropower Staff Quarter for Nepal consult Pvt. Ltd., 2000.
• Designed Constructed Wetland System for Kathmandu University, 2000
• Designed and supervised construction of Constructed Wetland system for Malpli- International School, 2000
• Designed and supervised construction of septage treatment plant using the Constructed Wetland System for Kathmandu Metropolis, 1998
• Designed Constructed Wetland to treat greywater from a single household to recycle greywater and investigate its performance for six months
• Designed a two-staged Constructed Wetland for wastewater treatment of Dhulikhel Hospital and investigate its performance for a year.
• Carried out investigations on a surface water treatment plant (Horizontal-roughing Filter followed by slow sand filter) for artificial groundwater recharge in Marchfeld region, Vienna, Austria (1993)