APPLICATION OF WASTE STABILIZATION PONDS IN BHUTAN - LESSONS WITHIN ASUSTAINABLE DEVELOPMENT CONTEXT

The Danish International Development Assistance agency has funded a pr oject in Bhutan which includes a water supply component in six urban c entres, a sewerage component in the two largest cities plus associated institutional development. The project includes the implementation of an extensive water-home sewerage system and associated wastewater tre atment. The treatment process adopted was waste stabilisation pond tec hnology due to the low associated construction, operations and mainten ance costs and low requirements for technical skills hence contributin g to financial and O&M sustainability of the project, as well as meeti ng the water quality requirements for the receiving waters. Since esse ntially all available land is utilised in the country, the locations o f the treatment plants are adjacent to rivers which are fast flowing, leading to a risk of severe erosion conditions during the monsoon seas on. In order to protect the treatment plant structure, river training was necessary. The high elevation of the country also has consequences for the design and operation of the plants. The wastewater treatment process includes a train of anaerobic, secondary facultative and matur ation ponds, lined with a high density polyethylene liner. This paper describes the project as implemented, focusing on the wastewater treat ment plants and the hurdles required to be overcome to ensure sustaina ble operation of the waste stabilisation pond treatment plants, in par ticular overall design of the system, the re-design required due to th e lass of land occasioned by the intense monsoon rains in the south of the country prior to construction of river training works, the traini ng required for the local staff from the operations and maintenance au thorities and the financial aspects of the project The project is disc ussed within a broader framework of Danish development aid in the coun try which covers the health, environment and the public health infrast ructure sectors. Lessons learnt from the project are discussed. (C) 19 97 IAWQ. Published by Elsevier Science Ltd.