Dr. Roshan Raj Shrestha and Prajwal Shrestha

ABSTRACT

Constructed Wetland (CW) for treatment of wastewater was introduced in Nepal on 1997 from a hospital. Now, there are 11 sub-surface flow constructed wetland system in operation for treatment of gray water, wastewater and fecal sludge at household to institutional (hospital, university, school, monastery and staff quarter) 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 a city. Recently, government has decided to install CW system at 8 small cities for treatment of municipal wastewater under Urban Environment Improvement Program funded by Asian Development Bank. ENPHO is carrying out research on its performance evaluation. Many national and international scholars are carrying out research on 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, ammonia-nitrogen. Similarly, removal of E. coli is also achieved about 99%. At three sites, the treated wastewater is being reused for toilet flushing, irrigation and cleaning vehicles. This paper analyses the pros and cons of CWs in Nepal for the treatment and reuse of wastewater from various sources and recommends measured to expand the use of this technology in Nepal as well as other countries for water conservation and protection of water bodies in a sustainable manner.

KEY WORDS: Constructed wetland, wastewater treatment, developing country, reuse, appropriate technology